Abstract
In this chapter, chiroptical properties, especially circularly polarized luminescence (CPL) properties of optically active molecules based on planar chiral [2.2]paracyclophane are mainly introduced. In addition, practical optical resolution methods of disubstituted and tetrasubstituted [2.2]paracyclophane molecules are also focused on. The enantiopure [2.2]paracyclophane compounds have been used as chiral building blocks to synthesize the optically active molecules by means of optical resolution. The [2.2]paracyclophane-based molecules are π-stacked molecules, which construct optically active second-ordered structures, such as V-, X-, triangle-shaped, and one-handed double helical structures, due to the orientation of stacked π-electron systems. Photoexcitation allows them to emit bright CPL with good photoluminescence (PL) quantum efficiencies and large dissymmetry factors (glum values). Thus, planar chiral [2.2]paracyclophane is the ideal scaffold to achieve excellent CPL properties.
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1 Introduction: Circularly Polarized Luminescence (CPL)
Circularly polarized luminescence (CPL) is a chiroptical (chiral + optical) property that is responsible for the difference in luminescence intensity between left-handed and right-handed emissions. Circular dichroism (CD) is another chiroptical property that is responsible for the difference in molar extinction coefficients between left- and right-polarized light. CPL and CD spectroscopy provide important information about the orientation of luminophores and chromophores, respectively (Berova et al. 2000). Many optically active molecules exhibit CPL and CD in the excited and ground states, respectively, but these phenomena cannot be always observed even if the molecules possess a chiral source.
CPL is evaluated by the anisotropic factor (dissymmetric factor), referred to as glum value (by Berova et al. 2000; Riehl and Richardson 1986; Riehl and Muller 2012), which can be calculated as the following Eq. (10.1):
∆I = (emission intensity of left-handed CPL) − (emission intensity of right-handed CPL) and I = emission intensity
The glum value can also be expressed as
Here, μ and m represent electric and magnetic transition dipole moments, respectively, and the θ represents the angle between them (Berova et al. 2000; Riehl and Richardson 1986; Riehl and Muller 2012). Thus, the maximum absolute glum value is calculated to be |glum| = +2.
Ideally, forbidden electric transitions and allowed magnetic transitions are preferred. Generally, the glum values of chiral lanthanide complexes are much larger than those of chiral organic molecules. The emission of lanthanides is derived from the Laporte forbidden f-f transition (Muller 2014); therefore, the μ is small and m is large. It is reported that the chiral Eu(III) complex, tetrakis(3-heptafluoro-butylryl-(+)-camphorato) Eu(III), has a glum value of +1.38 (Lunkley et al. 2008).
Many of glum values of organic molecules reported are within the range 10−3–10−5 order due to the much smaller m. Therefore, Eq. (10.2) can be simply converted to the approximated Eq. (10.3).
Considering the photoluminescence quantum efficiency (ΦPL) and emission intensity, an allowed electronic transition is preferable. It is a challenging task to achieve a large m and small μ, and their linear orientation (their angle θ = 0° or 180°) in the organic molecules. Organic CPL dyes are attractive luminescent materials due to their light-weight, as well as the ease of fabrication, functional group modification, and emission color control. These dyes are expected to be promising candidates for next-generation emissive materials such as light-emitting diodes for three-dimensional displays, security inks, light for plant growth, bioimaging materials, etc.
A wide variety of organic CPL emitters have been reported thus far, and the last five years have seen a marked increase in the number of related manuscripts because of the widespread use of CPL spectrometers (Maeda and Bando 2013; Sánchez-Carnerero et al. 2015; Tanaka et al. 2018; Chem and Yan 2018). The CPL-emitting small organic molecules in the dispersed state are briefly introduced below. In 1967, CPL from organic molecules was reported for cyclic ketones with a central chirality (Emeris and Oosterhoff 1967); a representative example is shown in Fig. 10.1. Because of the forbidden n-π* transition, the molecule emitted CPL with a very large glum value of +3.5 × 10−2. This value was long considered the champion value for a long time in the small organic molecules in a diluted solution, although the ΦPL was quite low (ΦPL = 1 × 10−5). Various CPL emitters with the central chirality have been reported to show large glum values. As the representative examples, naphthyl (Amako et al. 2014) and naphthalimide (Sheng et al. 2016) emissive units were connected on chiral cyclic scaffolds, which showed CPL emission from the intramolecular aggregate (excimer) of the aromatic units with |glum| values of 9.4 × 10−3 (ΦPL = 0.02) and 1.4 × 10−2, respectively. In 2017, the champion glum value was updated for the cylindrical molecule 4 with cylinder helicity (Fig. 10.2), and it was on the order of 10−1 (|glum| = 1.5 × 10−1 and ΦPL = 0.80) (Sato et al. 2017). Theoretical studies revealed a large m, as well as linearly oriented m and μ (θ = 180°).
Biaryl-based axial chirality is an easily accessible chiral scaffold for CPL emission. Figure 10.3 shows the binaphthyl-based molecules. In 2007, perylenebiscarboxydiimide-containing binaphtylene (S)-5 was prepared (Kawai et al. 2007). This compound showed intense emission with ΦPL of 0.88, and the glum was estimated to be approximately 3 × 10−3. Simple biaryl-based molecules (open- and closed-type molecules (S)-6open and (S)-6close, respectively) were synthesized (Kimoto et al. 2012). Despite their similar photoluminescence behavior and identical absolute configuration, these molecules showed different CPL signals. The values for (S)-6open and (S)-6close were calculated to be +1.0 × 10−3 (ΦPL = 0.19) and −1.4 × 10−3 (ΦPL = 0.25), respectively. Optically active naphthalene oligomers were synthesized; the representative molecule (R,R,R,R,R,R,R)-7 consisting of eight naphthyl moieties is also shown in Fig. 10.3 (Takaishi et al. 2017). This molecule showed bright CPL emission with glum = +2.2 × 10−3 and ΦPL = 0.90. Compound (S)-5 emitted from the perylenediimide moieties, whereas (S)-6 and 7 showed emission from the oligoaryl scaffolds.
Helical chirality is also employed for CPL emission. Generally, ΦPL of a helical molecule is not very high; however, its glum value is very large, often on the order of 10−2. Figure 10.4 shows the helicene derivatives (M)-8 (Field et al. 2003) and (M)-9 (Sawada et al. 2012) as representative examples. Molecule 8 is the first helicene emitting CPL in dilute solution. This molecule was obtained as a diastereomer due to the attachment of a camphanate unit as the chiral auxiliary. The |glum| value was calculated to be 1.1 × 10−3. A very large |glum| value of 3.2 × 10−2 (ΦPL = 0.30) was obtained from molecule 9, which was prepared by the Rh-catalyzed enantioselective [2 + 2 + 2] cycloaddition. Molecule 10 is a stimuli-responsive compound used for capturing halogen anions to form a helix (Haketa et al. 2012). The chiral counter cation is allowed for the introduction of one-handed helicity in dilute solution. The resulting ion pair was emissive, and the |glum| value was calculated to be 1.3 × 10−2 with ΦPL of 0.33.
Recently, planar chirality has also been applied to CPL emission. However, there are fewer CPL emitters based on planar chirality as compared to those based on axial and helical chiralities. Unique optically active molecules have been prepared by taking advantage of the planar chirality of a [2.2]paracyclophane scaffold, and large glum values, as well as high ΦPL were achieved (Morisaki and Chujo 2019). Various interesting second-ordered structures were also constructed. This chapter focuses on planar chirality and CPL emission in the mono-dispersed state from the optically active small organic molecules based on the planar chiral [2.2]paracyclophanes.
2 Introduction: [2.2]Paracyclophane and Its Planar Chirality
Cyclophane is a cyclic compound containing at least one aromatic ring in the main chain skeleton. It is a well-known cyclic compound and have been used particularly in the field of synthetic organic chemistry and organometallic chemistry (Vögtle 1993; Gleiter and Hopf 2004). The typical cyclophane is [2.2]paracyclophane (Fig. 10.5), in which two phenylenes are stacked in proximity (the distance between two benzene rings is approximately 3.0 Å). [2.2]Paracyclophane was first synthesized in 1949, by pyrolysis of para-xylene (Brown and Farthing 1949); subsequently, a direct synthesis from 1,4-bis-bromomethylbenzene by Wurtz-type intramolecular cyclization was reported in 1951 (Cram and Steinberg 1951). Since then, various synthetic routes have been developed to prepare a wide variety of [2.2]paracyclophane molecules. [2.2]Paracyclophane has a unique π-stacked structure, and there have been many studies on its physical properties within the field of organic chemistry (Gleiter and Hopf 2004; Brown and Farthing 1949).
Although [2.2]paracyclophane is a molecule that has generally been used in the field of organic chemistry and organometallic chemistry, its utilization is not widespread in the fields of polymer chemistry and materials chemistry (Hopf 2008; Morisaki and Chujo 2006, 2008, 2009, 2011, 2012; Mizogami and Yoshimura 1985; Guyard and Audebert 2001; Guyard et al. 2002; Salhi et al. 2002; Salhi and Collard 2003; Jagtap and Collard 2010; Weiland et al. 2019). In terms of the through-space conjugated system, [2.2]paracyclophane-based π-stacked molecules have been systematically prepared, and their electronic communication between the stacked π-electron systems have been known since 1998 (Oldham et al. 1998; Bazan et al. 1998; Bartholomew and Bazan 2001; Bazan 2007). In 2001, thiophene-substituted [2.2]paracyclophanes were polymerized electrochemically; however, the polymer was deposited on the electrode and was insoluble in solvents (Guyard and Audebert 2001). In 2002, soluble π-stacked polymers consisting of [2.2]paracyclophane as a repeating unit in the main chain were synthesized (Morisaki and Chujo 2002). Since then, various π-stacked polymers have been prepared (Morisaki and Chujo 2006, 2008, 2009, 2011, 2012). The structures have been well-characterized, and the properties, such as optical properties, have been shown due to their solubility in organic solvents. Since their optical properties changed continuously depending on the number of the stacked π-electron systems, they were called “through-space conjugated polymers”. Highly efficient unidirectional fluorescence resonance energy transfer (FRET) (Morisaki et al. 2013, 2014a, 2014b, 2017), as well as through-space electron transfer (Molina-Ontoria et al. 2011; Wielopolski et al. 2013) was achieved by precisely designing the stacked π-electron systems. [2.2]Paracyclophane-based through-space conjugated polymers and oligomers can act as single molecular wires.
As described above, [2.2]paracyclophane consists of two phenylene units fixed in proximity; therefore, the rotational movement of the benzene rings is suppressed. By introducing a substituent at appropriate positions on the benzene ring(s), the corresponding [2.2]paracyclophane becomes a planar chiral molecule (Fig. 10.5) (Cram and Allinger 1955; Rozenberg et al. 2004; Rowlands 2008; Gibson and Knight 2003; Aly and Brown 2009; Paradies 2011). The planar chirality of [2.2]paracyclophane is well-known in the fields of organic chemistry and organometallic chemistry, and planar chiral [2.2]paracyclophanes have been utilized as chiral auxiliaries and chiral ligands. However, until recently, the planar chirality of [2.2]paracyclophane has been ignored in the fields of polymer chemistry and materials chemistry until recently. In 2012, a new optical resolution method was developed for pseudo-ortho-disubstituted [2.2]paracyclophane, and the transformation and polymerization of the enantiopure [2.2]paracyclophanes were reported (Morisaki et al. 2012a, b). The resulting optically active polymer emitted CPL (Morisaki et al. 2012).
This chapter highlights and introduces the recent results on the synthesis of enantiopure disubstituted and tetrasubstituted [2.2]paracyclophanes. The preparation of optically active molecules based on the [2.2]paracyclophanes for their application in the fields of polymer and materials chemistry as the CPL emitters is also described.
3 Synthesis of Enantiopure Disubstituted [2.2]Paracyclophane and Optically Active π-Stacked Molecules
Optical resolution routes of mono-substituted [2.2]paracyclophanes were developed, and various enantiopure ortho-, pseudo-geminal-, and syn-latero-disubstituted [2.2]paracyclophanes were prepared (Cram and Allinger 1955; Rozenberg et al. 2004; Rowlands 2008; Gibson and Knight 2003; Aly and Brown 2009; Paradies 2011). In addition, several synthetic routes to the syntheses of enantiopure disubstituted [2.2]paracyclophanes, e.g., pseudo-ortho-disubstituted [2.2]paracyclophanes, have been reported (Pye et al. 1997; Rossen et al. 1997; Zhuravsky et al. 2008; Jiang and Zhao 2004; Jones et al. 2003; Pamperin et al. 1997; Pamperin et al. 1998; Braddock et al. 2002), as shown in Fig. 10.6. A representative example is the synthesis of enantiopure pseudo-ortho-bis(diarylphosphino)[2.2]paracyclophane (Ph-PHANEPHOS) (Fig. 10.6a) (Pye et al. 1997). The resulting (Sp)- and (Rp)-Ph-PHANEPHOS are the commercially available chiral ligands for the transition metal-catalyzed asymmetric reactions. This PHANEPHOS makes it possible to produce enantioenriched pseudo-ortho-dibromo[2.2]paracyclophane (Fig. 10.6b) by kinetic resolution (Rossen et al. 1997). Synthesis of optically active 4-bromo-12-hydroxy[2.2]paracyclophane (Zhuravsky et al. 2008), pseudo-ortho-dihydroxy[2.2]paracyclophane (PHANOL) (Jiang and Zhao 2004), and pseudo-ortho-dihydroxymethyl[2.2]paracyclophane (Jones et al. 2003) were successfully synthesized by using chiral camphanic acid chloride as the chiral auxiliary; for example, Fig. 10.6c shows the optical resolution of PHANOL racemate. The enzyme-promoted kinetic resolutions of pseudo-ortho-disubstituted [2.2]paracyclophanes have also been developed (Pamperin et al. 1997, 1998; Braddock et al. 2002).
A practical route to the optical resolution of pseudo-ortho-dibromo[2.2]paracyclophane was reported in 2012, in which (1R,2S,5R)-(-)-menthyl (S)-p-toluenesulfinate was used as the chiral auxiliary (Fig. 10.7) (Morisaki et al. 2012). Racemic pseudo-ortho-dibromo[2.2]paracyclophane rac-11 was reacted with n-butyllithium (n-BuLi). Then, the reaction with (1R,2S,5R)-(-)-menthyl-p-toluenesulfinate afforded the diastereomers (Rp,S)- and (Sp,S)-12, which could be separated by using SiO2 column chromatography. The isolated diastereomers were reacted with t-BuLi to form dilithiated intermediate 13; not only the lithium-halogen exchange reaction, but also the lithium-sulfur exchange reaction occurred (Rowlands 2008; Clayden 2002; Hitchcock et al. 2005; Parmar et al. 2010). The subsequent reaction with various electrophiles produced enantiopure pseudo-ortho-disubstituted [2.2]paracyclophanes (Fig. 10.7). (Rp)- and (Sp)-Diformyl[2.2]paracyclophanes 14 could be separated by chiral column chromatography; thus, their chromatographic optical resolution was also possible (Morisaki et al. 2012). This synthetic route can be used to produce new PHANEPHOS; for example, cyclohexyl groups could be introduced on phosphorus atoms to produce Cy-PHANEPHOS 16 (Fig. 10.7).
Pseudo-ortho-diformyl[2.2]paracyclophane 14 could be converted to the corresponding diethynyl[2.2]paracyclophane 17 using the Ohira-Bestmann reagent (Fig. 10.8) (Ohira 1989; Müller et al. 1996), which was used as a monomer to synthesize poly(p-arylene-ethynylene)s (poly-PAEs) via Sonogashira-Hagihara coupling (Tohda et al. 1975; Sonogashira 2002) polymerization. The treatment of 17 with 1,4-diiodobenzene derivative 18 affords the optically active through-space conjugated polymers (Rp)- and (Sp)-19 (Morisaki et al. 2012). Chiroptical properties (chiral optical properties) of 9 showed the intense CPL in the emission region (Fig. 10.9). In addition, its absolute photoluminescence (PL) quantum efficiency (ΦPL) was approximately 80% and the |glum| value was 2.2 × 10−3 in dilute CHCl3 solution. These results indicated that the optically active polymer 19 is a good CPL emitter.
The chiroptical properties of PAE oligomers were investigated (Morisaki et al. 2014). As shown in Fig. 10.10, the optically active PAE-type π-stacked dimer (Rp)-20, trimer (Rp)-21, tetramer (Rp)-22, and cyclic trimer (Rp)-23 were prepared from (Rp)-15 (shown in Fig. 10.7) and (Rp)-17 as the key chiral building blocks.
Figure 10.10 includes the optical and chiroptical data. The absolute anisotropic factors of absorbance (gabs values = [(molar absorption coefficient of left-handed circular polarized light) – (molar absorption coefficient of right-handed circular polarized light)]/(molar absorption coefficient) at \( \lambda \)abs,max) were calculated from the CD spectra of the optically active oligomers, and the |glum| values at \( \lambda \)PL,max calculated from CPL spectra. The |gabs| values of 20–22 were substantially constant at 3.0 × 10−3, regardless of the number of stacked π-electron systems. Linearly π-stacked structures of 20–22 in the ground state can adopt various conformations in dilute solution, leading to the constant gabs values. In other words, the constant gabs values reflect only the chirality of optically active V-shaped skeleton of the cyclophane moiety. A gabs value is a normalized value; therefore, the gabs values of 20–22 were constant independent of the number of stacked π-electron systems.
In contrast, the glum values of 20–22 increased depending on the number of stacked π-electron systems. It is speculated that some sort of chirality is induced in addition to the optically active V-shaped structure of the cyclophane moiety in the excited state. The comparison of linear trimer 21 with cyclic trimer 23 gave the answer to this question. The gabs values of 21 and 23 were different, and their glum values were identical. The cyclic structure is a fixed chiral triangle structure (fixed optically active second-ordered structure), whereas the linear π-stacked structure adopts various conformations in the ground state. Thus, chiralities of both the second-ordered structure (chiral triangle structure) and the V-shaped structure affect the larger gabs value of 23 (3.7 × 10−3) more than that of 21 (3.0 × 10−3). On the other hand, the glum values of 21 and 23 were identical, indicating that 21 and 23 adopt a similar structure in the excited state. PAEs, poly(p-arylenevinylene)s (PAVs), and poly(p-arylene)s (PAs) are known to form planar structures in the excited states, because of the contribution of the quinoid moiety in the excited state. Considering the conformation of 21 in the excited state, each of the three π-electron systems of 21 assumes a planar structure, producing either a zigzag structure or a helical structure (foldamer) in the excited state. The glum values of 21 and 23 were identical; therefore, 21 forms a structure similar to a cyclic one, i.e., a one-handed helical structure (optically active second-ordered structure), as shown in Fig. 10.11.
Optically active through-space conjugated polymer 26 consisting of enantiopure planar chiral 4,12-disubstituted [2.2]paracyclophane and quaterthiophene was synthesized by Suzuki-Miyaura coupling (Miyaura et al. 1979) between 24 and 25 (Fig. 10.12) (Morisaki et al. 2015). Moderate CPL was observed (Fig. 10.13), and the ΦPL and |glum| values were estimated to be 0.07 and 5 × 10−4, respectively.
Chromatographic optical resolutions of pseudo-ortho-disubstituted [2.2]paracyclophanes were reported by Lützen (Meyer-Eppler et al. 2013) and Hasegawa (Kobayakawa et al. 2014; Hasegawa et al. 2017, 2019; Ishioka et al. 2019), and several enantiopure π-stacked molecules have been produced. Figure 10.14 shows the (Rp)-isomers prepared by Hasegawa and coworkers (Kobayakawa et al. 2014; Hasegawa et al. 2017; Hasegawa et al. 2019; Ishioka et al. 2019). Although the CPL properties of these compounds were not reported, their interesting chiroptical and electrochemical properties were shown. Compound 27 was used as a chiral dopant for nematic liquid crystals with a helical twisting power of around 10 m−1 (Kobayakawa et al. 2014), and 28 (Hasegawa et al. 2017) and 29 (Hasegawa et al. 2019) exhibited unique redox behaviors owing to the closely stacked quaterthiophenes and biselenophenes, respectively. Recently, PA-type π-stacked molecules 30 and 31 have been reported, in which terphenylenes and quaterphenylenes were stacked at the terminal benzene rings (Ishioka et al. 2019), respectively, as shown in Fig. 10.14. Intense CPL was observed from 30 with ΦPL of 0.20 and |glum| of 4.2 × 10−3 as well as 31 with ΦPL of 0.64 and |glum| of 1.5 × 10−3.
4 Synthesis of Enantiopure 4,7,12,15-Tetrasubstituted [2.2]Paracyclophane and Optically Active π-Stacked Molecules
In 2014, an optical resolution method of 4,7,12,15-tetrasubstituted [2.2]paracyclophane was reported (Fig. 10.15) (Morisaki et al. 2014). The racemate 4,7,12,15-tetrabromo[2.2]paracyclophane rac-32 was synthesized by Chow and coworkers (Chow et al. 2005). One of the bromo groups of rac-32 was converted to a hydroxy group to obtain rac-33, and the reaction with (1S,4R)-(-)-camphanic chloride as a chiral auxiliary resulted in the diastereomers (Rp,1S,4R)-34 and (Sp,1S,4R)-34. The absolute configuration could be determined by X-ray crystallography. Separation of diastereomers was readily carried out in gram-scale by simple SiO2 column chromatography.
The chiral unit was easily removed by hydrolysis to afford the optically active phenol 33 (Fig. 10.16). The treatment of 33 with trifluoromethanesulfonic anhydride afforded the optically active 4,7,12,15-tetrasubstituted [2.2]paracyclophane 35. Subsequent Sonogashira-Hagihara coupling between the optically active cyclophane 35 with trimethylsilyl (TMS) acetylene proceeded smoothly to afford triyne 36 with good yield. Interestingly, Pd2(dba)3/PtBu3/CuI catalyst system (dba = dibenzylideneacetone and PtBu3 = tri(t-butyl)phosphine) led to chemoselective coupling with bromo groups. Then, the remaining trifluoromethylsulfonyl group could be reacted with TMS acetylene using a PdCl2(dppf) catalyst (dppf = 1,1′-bis(diphenylphosphino)ferrocene) to give the optically active tetrayne 37. The TMS groups were removed to give the optically active 4,7,12,15-tetraethynyl[2.2]paracyclophane 38.
Optically active cyclic molecules 39–41 were synthesized with 38 serving as a chiral building block (Fig. 10.17), and their chiroptical properties were revealed. The large chirality was induced in both the ground state and the excited state. For example, the specific rotation of 39 was approximately 1,500, and the molar ellipticity reached 3,000,000 deg cm2 dmol−1. Cyclic molecule 39 exhibited excellent CPL profiles (Fig. 10.18), and the |glum| value at \( \lambda \)PL,max was on the order of 10−2 with ΦPL of 0.45. In addition to the planar chirality of the [2.2]paracyclophane skeleton, the chiral second-ordered structure, namely, the chiral two blades propeller-shaped structure contributed to the chiral induction in the excited state. The propeller-shaped molecules 40 (Gon et al. 2015) and 41 (Gon et al. 2016) showed a large molar absorption coefficient, good ΦPL, and large CPL glum value. Especially, propeller-shaped molecule 40 was also an excellent CPL emitter with a large glum value and good ΦPL of 0.60.
Optically active X-shaped molecules 42–44 were synthesized from 4,7,12,15-tetrasubstituted [2.2]paracyclophane 38 (Fig. 10.19) (Gon et al. 2015). Various aromatic units such as benzene, naphthalene, and anthracene could be introduced to the 4,7,12,15-tetrasubstituted [2.2]paracyclophane skeleton. All compounds emitted CPL with good ΦPL, and large CPL glum value; as a representative example, PL and CPL spectra of 43 are shown in Fig. 10.20.
Figure 10.21 shows the 3rd generation chiral dendrimer (Gon et al. 2016) consisting of a chiral X-shaped core and Fréchet-type dendrons that were prepared by the convergent method (Hawker and Fréchet 1990; Fréchet 1994). The 2nd to 4th generation dendrimers exhibited good film-forming ability, and the thin films could be obtained by the spin-coating approach. The thin film emitted bright CPL from the chiral core unit upon excitation of the benzene rings of dendrons. Energy transfer occurred from the dendrons to the chiral core, and intense PL was emitted. Due to the dendrons, aggregation-caused quenching was completely suppressed, and thus, the bright CPL was observed; CPL and PL spectra are shown in Fig. 10.22. The ΦPL of the thin films were estimated to be 65%, and the glum value at \( \lambda \)PL,max was approximately 2 × 10−3.
An optically active X-shaped molecule 46 consisting of a more extended π-conjugation system was prepared from 38 as a chiral building block (Fig. 10.23) (Gon et al. 2017). The X-shaped molecule 46 emitted CPL with ΦPL of 87% in the dilute solution with a good |glum| value of 1.2 × 10−3. In addition, this molecule showed good film formability. The glum value of the thin film formed by the spin-coating method exhibited the positive CPL signal with the glum value of +2.1 × 10−2 (Fig. 10.24), which was larger by one order of magnitude compared with that the dilute solution. The annealed spin-coated film exhibited a negative glum value of –0.25 (Fig. 10.24), which was a very large value on the order of 10−1. The optically active higher-ordered structure was constructed in the thin film by π-π interactions among the extended π-conjugation systems, as well as the van der Waals force of the C12H25 chains. It seems that the thermodynamically stable higher-ordered structure was formed by the heating protocol.
Chemoselective Sonogashira-Hagihara coupling using Pd2(dba)3/PtBu3 catalyst system was utilized to stack different π-electron systems (Sasai et al. 2018). The triyne 36 mentioned above was used as the substrate to produce chiral X-shaped π-stacked dimers 48 and 50 consisting of different π-electron systems as shown in Fig. 10.25. Normal X-shaped molecule 51 was also prepared from 36 via 37 (Gon et al. 2017; Kikuchi et al. 2019). The optical, as well as chiroptical properties of 48 and 50, were almost the same as those of the corresponding X-shaped molecule 51 (Table 10.1). The number of methoxy groups increased, spectra were redshifted and ΦPL and glum values were increased. Thus, they were excellent CPL emitters.
Optically active p-arylene-vinylenes (PAVs)-stacked X-shaped molecules 52 and 53 were also prepared (Gon et al. 2017), and the structures are shown in Fig. 10.26. Racemic molecule 52 was prepared and their properties were investigated in detail (Bazan et al. 1998; Bartholomew and Bazan 2001; Bazan 2007; Morisaki and Chujo 2002). Molecule 52 exhibited CPL with a good ΦPL of 0.78 and |glum| value of 3.7 × 10−3, while the PL of the aggregates quenched to exhibit ΦPL of 0.03 with good |glum| = 4.3 × 10−3. Molecule 53 showed moderate PL profiles both in solution (ΦPL = 0.58) and in the aggregated state (ΦPL = 0.24), and moderate CPL properties with |glum| in the order of 10−4 in solution, as well as in the aggregation state were observed. The optical and chiroptical properties varied drastically by attaching phenyl groups to the ethene moieties.
5 Synthesis of Enantiopure Bis-(Para)-Pseudo-Ortho-Tetrasubstituted [2.2]Paracyclophane and Syntheses of Optically Active π-Stacked Molecules
In 2016, a new type of enantiopure 4,7,12,15-tetrasubstituted [2.2]paracyclophane was produced. Racemic bisphenol rac-54 was used as a starting material and reacted with (1S,4R)-(-)-camphanic chloride as a chiral auxiliary to obtain the diastereomers (Rp,1S,4R)-55 and (Sp,1S,4R)-55 (Figs. 10.6c, 10.27) (Jiang and Zhao 2004). The diastereomers were reacted with bromine using iron without separation (Fig. 10.27). Regioselective bromination proceeded with iron to obtain 4,7,12,15-tetrasubstituted [2.2]paracyclophanes (Rp,1S,4R)-56 and (Sp,1S,4R)-56 (Kikuchi et al. 2019; Morisaki et al. 2016); this tetrasubstituted isomer is called bis-(para)-pseudo-ortho-tetrasubstituted [2.2]paracyclophane (Vorontsova et al. 2008). The diastereomers were separated by simple column chromatography using SiO2. Removal of the chiral auxiliary groups with KOH formed chiral bisphenol 57, and the successive reaction with trifluoromethanesulfonic anhydride resulted in enantiopure bis-(para)-pseudo-ortho-type tetrasubstituted [2.2]paracyclophane building blocks 58 (Morisaki et al. 2016).
Chemoselective Sonogashira-Hagihara coupling was available for 58. The treatment of 58 with TMS acetylene in the presence of a catalytic amount of Pd2(dba)3/PtBu3/CuI afforded the diyne 59 selectively, as shown in Fig. 10.28. The coupling reaction between 59 with triisopropylsilyl (TIPS) acetylene using a Pd2(dba)3/dppf catalyst system enabled us to obtain the corresponding tetrayne 60. K2CO3/MeOH allowed the chemoselective removal of the TMS group from 60 to obtain diyne 61. Then, Sonogashira-Hagihara coupling of 60 with p-iodoanisole produced 62. The TIPS group was easily removed by Bu4NF, and the reaction with m-diiodobenzene provided enantiopure cyclic molecule 63 consisting of two optically active cyclophanes, in which boomerang-shaped arylene-ethynylene containing five benzene rings are stacked at the second and fourth phenylene moieties. This cyclic molecule forms a one-handed double helical structure; for example, the (Rp,Rp)-isomer construct left-handed double helices. This double helical molecule also emitted intense CPL with ΦPL of 0.62 and |glum| = 1.6 × 10−3; the PL and CPL spectra are shown in Fig. 10.29.
Enantiopure bisphenol 57 was reacted with K2CO3 and MeI to obtain a new chiral building block (Rp)-64 in high yield (Fig. 10.30) (Kikuchi et al. 2019). The reaction of (Rp)-64 with TMS acetylene in the presence of Pd2(dba)3/PtBu3/CuI catalyst system proceeded smoothly to obtain the cross-coupling product (Rp)-65. The TMS groups of (Rp)-65 were easily removed by K2CO3/MeOH to obtain diyne (Rp)-66. The Sonogashira-Hagihara reaction of (Rp)-66 with iodotoluene derivative resulted in the corresponding V-shaped molecule (Rp)-67 (Fig. 10.30). In molecule 67, π-electron systems are stacked at the terminal benzene rings, whereas the same π-electron systems are stacked at the central benzene rings in the X-shaped molecule 51 (Fig. 10.25). Their CPL spectra are shown in Fig. 10.31, indicating the opposite CPL signs in spite of having the same absolute configuration. Incidentally, Fig. 10.31 shows the spectra of (Sp)-isomers, because the simulation was carried out for them (vide infra).
The electronic transition dipole moments and magnetic transition dipole moments were simulated for V-shaped 67 and X-shaped 51 (Fig. 10.32) (Kikuchi et al. 2019); the simulations were carried out for (Sp)-isomers. Theoretically, a glum value is expressed in the following equation: 4|μ||m|cosθ/(|μ|2 + |m|2) as mentioned. The μ and m represent electric and magnetic transition dipole moments, respectively, and the θ represents the angle between the μ and m. The angle θ between μ and m of (Sp)-67 was estimated to be 144°, and that of (Sp)-51 was estimated to be 87°. Simulation results predicted opposite CPL signs for 67 (negative due to θ = 144°) and 51 (positive due to θ = 87°), which was supported by the experimental results (Fig. 10.31). Thus, the appropriate construction of the intermolecular orientations of π-electron systems is important not only for CPL intensity, but also for CPL signs. In other words, negative and positive signs of CPL can be controlled by the orientation of the π-electron systems.
6 Synthesis of Enantiopure Bis-(Para)-Pseudo-Meta-Tetrasubstituted [2.2]Paracyclophane
In 2018, enantiopure bis-(para)-pseudo-meta-tetrasubstituted [2.2]paracyclophane derivatives were prepared as new chiral building blocks by means of diastereomeric optical resolution (Sawada et al. 2018). On the other hand, Lützen and coworkers had already reported the chromatographic optical resolution of disubstituted analogs in 2014 (Meyer-Eppler et al. 2014). Racemic 4,7,12,15-tetrasubstituted [2.2]paracyclophane rac-33 was used as the starting material, which was reacted with BuLi to form the dilithiated intermediate rac-68 (Fig. 10.33). After the formation of lithium phenoxide, the next lithium-halogen exchange occurred at pseudo-meta-position due to the electronic effect, leading to bis-(para)-pseudo-meta-type dilithiated [2.2]paracyclophane. Addition of B(OMe)3 to the intermediate and the treatment with H2O2/NaOH resulted in dibromodihydroxy[2.2]paracyclophane rac-69. Diastereomer approach using (1S,4R)-(-)-camphanic chloride enabled the optical resolution of the bis-(para)-pseudo-meta-type tetrasubstituted [2.2]paracyclophane (Fig. 10.33). The resulting diastereomers (Rp,1S,4R)-70 and (Sp,1S,4R)-70 were separated by simple column chromatography using SiO2. The reaction of 70 with KOH afforded the bisphenol and the next reaction with trifluoromethanesulfonic anhydride produced enantiopure bis-(para)-pseudo-meta-type tetrasubstituted [2.2]paracyclophanes 71. These enantiomers are also used as the chiral building blocks for various CPL emitters.
7 Conclusion
In summary, the authors have focused on the planar chirality of [2.2]paracyclophane and the intense CPL emission from the enantiopure [2.2]paracyclophane-based molecules in this chapter. Their optical resolution methods basically consisted of diastereomer resolution methods using the common chiral auxiliaries such as (1R,2S,5R)-(-)-menthyl-p-toluenesulfinate and (1S,4R)-(-)-camphanic chloride instead of chromatographic resolution by chiral columns. A wide variety of optically active π-stacked molecules, cyclic molecules, oligomers, and polymers were prepared using the obtained enantiopure disubstituted and tetrasubstituted [2.2]paracyclophanes as chiral building blocks. They were used to construct the chiral higher-ordered structures such as V-shaped, X-shaped, propeller-shaped, triangle-shaped, and double helical structures both in the ground and excited states due to the structurally stable planar chiral cyclophanes. This is important to show excellent CPL performance. [2.2]Paracyclophane-based molecules exhibit good PL property with high ΦPL. Their ε values are large because of the extended π-electron systems. Generally, it is difficult to produce the materials emitting intense CPL with high ΦPL and large glum. The planar chiral [2.2]paracyclophane skeleton seems to be an ideal scaffold for developing materials exhibiting strong CPL.
References
Aly AA, Brown AB (2009) Asymmetric and fused heterocycles based on [2.2]paracyclophane. Tetrahedron 65:8055–8089
Amako T, Nakabayashi K, Mori T, Inoue Y, Fujiki M, Imai Y (2014) Sign inversion of circularly polarized luminescence by geometry manipulation of four naphthalene units introduced into a tartaric acid scaffold. Chem Commun 50:12836–12839
Bartholomew GP, Bazan GC (2001) Bichromophoric paracyclophanes: models for interchromophore delocalization. Acc Chem Res 34:30–39
Bazan GC (2007) Novel organic materials through control of multichromophore interactions. J Org Chem 72:8615–8635
Bazan GC, Oldham WJ, Lachicotte RJ, Tretiak S, Chernyak V, Mukamel S (1998) Stilbenoid dimers: dissection of a paracyclophane chromophore. J Am Chem Soc 120:9188–9204
Berova N, Nakanishi K, Woody RW (eds) (2000) Circular dichroism, 2nd edn. Wiley-VCH, Toronto
Braddock DC, MacGilp ID, Perry BG (2002) Improved synthesis of (±) -4,12-dohydroxy[2.2]paracyclophane and its enantiomeric resolution by enzymatic methods: plana chiral (r)- and (s)-phanol. J Org Chem 67:8679–8681
Brown CJ, Farthing AC (1949) Preparation and structure of di-p-xylylene. Nature 164:915–916
Chem N, Yan B (2018) Recent theoretical and experimental progress in circularly polarized luminescence of small organic molecules. Molecules 23:3376/1–32
Chow HF, Low KH, Wong KY (2005) An improved method for the regiospecific synthesis of polysubstituted [2.2]paracyclophanes. Synlett 2130–2134
Clayden J (2002) In organolithiums: selectivity for synthesis. Pergamon, Oxford, pp 141–142
Cram DJ, Allinger NL (1955) Macro rings. xii. stereochemical consequences of steric compression in the smallest paracyclophane. J Am Chem Soc 77:6289–6294
Cram DJ, Steinberg H (1951) Macro rings. i. preparation and spectra of the paracyclophanes. J Am Chem Soc 73:5691–5704
Emeris CA, Oosterhoff LJ (1967) Emission of circularly-polarized radiation by optically-active compounds. 1:129–132
Field JE, Muller G, Riehl JP, Venkataraman D (2003) circularly polarized luminescence from bridgedtriarylamine helicenes. J Am Chem Soc 125:11808–11809
Fréchet JMJ (1994) Functional polymers and dendrimers: reactivity, molecular architecture, and interfacial energy. Science 263:1710–1715
Gibson SE, Knight JD (2003) [2.2]Paracyclophane derivatives in asymmetric catalysis. Org Biomol Chem 1:1256–1269
Gleiter R, Hopf H (2004) Modern cyclophane chemistry. Wiley-VCH, Weinheim
Gon M, Morisaki Y, Chujo Y (2015a) Optically active cyclic compounds based on planar chiral [2.2]paracyclophane: extension of the conjugated systems and chiroptical properties. J Mater Chem C 3:521–529
Gon M, Morisaki Y, Chujo Y (2015) Highly emissive circularly polarized luminescence from optically active conjugated dimers consisting of planar chiral [2.2]paracyclophane. Eur J Org Chem 7756–7762
Gon M, Kozuka H, Morisaki Y, Chujo Y (2016a) Optically active cyclic compounds based on planar chiral [2.2]paracyclophane: extension of the π-surface with naphthalene units. Asian J Org Chem 5:353–359
Gon M, Morisaki Y, Sawada R, Chujo (2016) Synthesis of optically active x-shaped conjugated compounds and dendrimers based on planar chiral [2.2]paracyclophane, leading to highly emissive circularly polarized luminescence materials. Chem Eur J 22:2291–2298
Gon M, Sawada R, Morisaki Y, Chujo (2017) Enhancement and controlling the signal of circularly polarized luminescence based on a planar chiral tetrasubstituted [2.2]paracyclophane framework in aggregation system. Macromolecules 50:1790–1802
Gon M, Morisaki Y, Chujo (2017) optically active phenylethene dimers based on planar chiral tetrasubstituted [2.2]paracyclophane. Chem Eur J 23:6323–6329
Guyard L, Audebert P (2001) Synthesis and electrochemical polymerization of bis-dithienyl cyclophane. Electrochem Commun 3:164–167
Guyard L, Audebert P, Dolbier WR Jr, Duan JX (2002) Synthesis and electrochemical polymerization of new oligothiophene functionalized fluorocyclophanes. J Electroanal Chem 537:189–193
Haketa Y, Bando Y, Takaishi K, Uchiyama M, Muranaka A, Naito M, Shibaguchi H, Kawai T, Maeda H (2012) Asymmetric induction in the preparation of helical receptor-anion complexes: ion-pair formation with chiral cations. Angew Chem Int Ed 51:7967–7971
Hasegawa M, Kobayakawa K, Matsuzawa H, Nishinaga T, Hirose T, Sako K, Mazaki Y (2017) Chem Eur J 23:3267–3271
Hasegawa M, Kobayakawa K, Nojima Y, Mazaki Y (2019) Org Biomol Chem 17:8822–8826
Hawker CJ, Fréchet JMJ (1990) Preparation of polymers with controlled molecular architecture. a new convergent approach to dendritic macromolecules. J Am Chem Soc 112:7638–7647
Hitchcock PB, Rowlands GJ, Parmar R (2005) The synthesis of enantiomerically pure 4-substituted [2.2]paracyclophane derivatives by sulfoxide–metal exchange. Chem Commun 4219–4221
Hopf H (2008) [2.2]paracyclophane in polymer chemistry and materials chemistry. Angew Chem Int Ed 47:2–7
Ishioka S, Hasegawa M, Hara N, Sasaki H, Nojima Y, Imai Y, Mazaki Y (2019) Chiroptical properties of oligophenylenes anchoring with stereogenic [2.2]paracyclophane 48:640–643
Jagtap SP, Collard DM (2010) Multitiered 2D π-stacked conjugated polymers based on pseudo-geminal disubstituted [2.2]paracyclophane. J Am Chem Soc 132:12208–12209
Jiang B, Zhao XL (2004) A simple and efficient resolution of (±)-4,12-dihydroxy[2.2]paracyclophane. Tetrahedron Asym 15:1141–1143
Jones PG, Hillmer J, Hopf H (2003) (S)-4,16-dihydroxymethyl-[2.2]paracyclophane bis-(1s)-camphanoate. Acta Cryst E59:o24–o25
Kawai T, Kawamura K, Tsumatori H, Ishikawa M, Naito M, Fujiki M, Nakashima T (2007) Circularly polarized luminescence of a fluorescent chiral binaphthylene-perylenebiscarboxydiimide dimer. Chem Phys Chem 8:1465:1468
Kikuchi K, Nakamura J, Nagata Y, Tsuchida H, Kakuta T, Ogoshi T, Morisaki Y (2019) Control of circularly polarized luminescence by orientation of stacked π-electron systems. Chem Asian J 14:1681–1685
Kimoto T, Tajima N, Fujiki M, Imai Y (2012) Control of circularly polarized luminescence by using open- and closed-type binaphthyl derivatives with the same axial chirality. Chem Asian J 7:2836–2841
Kobayakawa K, Hasegawa M, Sasaki H, Endo J, Matsuzawa H, Sako K, Yoshida J, Mazaki Y (2014) Dimeric tetrathiafulvalene linked to pseudo-ortho-[2.2]paracyclophane: chiral electrochromic properties and use as a chiral dopant. Chem Asian J 9:2751–2754
Lunkley JL, Shirotani D, Yamanari K, Kaizaki S, Muller G (2008) Extraordinary circularly polarized luminescence activity exhibited by cesium tetrakis(3-heptafluoro-butylryl-(+)-camphorato) Eu(III) complexes in EtOH and CHCl3 Solutions. J Am Chem Soc 130:13814–13815
Maeda H, Bando Y (2013) Recent progress in research on stimuli-responsive circularly polarized luminescence based on π-conjugated molecules. Pure Appl Chem 85:1967–1978
Meyer-Eppler G, Vogelsang E, Benkhäuser C, Schneider A, Schnakenburg G, Lützen A (2013) Synthesis, chiral resolution, and absolute configuration of dissymmetric 4,12-difunctionalized [2.2]paracyclophane. Eur J Org Chem 4523–4532
Meyer-Eppler G, Sure R, Schneider A, Schnakenburg G, Grimme S, Lützen A (2014) Synthesis, chiral resolution, and absolute configuration of dissymmetric 4,15-difunctionalized [2.2]paracyclophanes. J Org Chem 79:6679–6687
Miyaura N, Yamada K, Suzuki A (1979) A new stereospecific cross-coupling by the palladium-catalyzed reaction of 1-alkenylboranes with 1-alkenyl or 1-alkynyl halides. Tetrahedron Lett 20:3437–3440
Mizogami S, Yoshimura S (1985) Synthesis of a new crystalline polymer: polymetacyclophane. J Chem Soc Chem Commun 1736–1738
Molina-Ontoria A, Wielopolski M, Gebhardt J, Gouloumis A, Clark T, Guldi DM, Martín N (2011) [2,2’]paracyclophane-based π-conjugated molecular wires reveal molecular-junction behavior. J Am Chem Soc 133:2370–2373
Morisaki Y, Chujo Y (2002) Synthesis of novel π-conjugated polymers having [2.2]paracyclophane skeleton in the main chain. extension of π-conjugated length via the through-space. Macromolecules 35:587–589
Morisaki Y, Chujo Y (2006) Through-space conjugated polymers based on cyclophanes. Angew Chem Int Ed 45:6430–6437
Morisaki Y, Chujo Y (2008) cyclophane-containing polymers. Prog Polym Sci 33:346–364
Morisaki Y, Chujo Y (2009) synthesis of π-stacked polymers on the basis of [2.2]paracyclophane. Bull Chem Soc Jpn 82:1070–1082
Morisaki Y, Chujo Y (2011) Through-space conjugated polymers consisting of [2.2]paracyclophane. Polym Chem 2:1249–1257
Morisaki Y, Chujo Y (2012) π-electron-system-layered polymers based on [2.2]paracyclophane. Chem Lett 41:840–846
Morisaki Y, Chujo Y (2019) Planar chiral [2.2]paracyclophanes: optical resolution and transformation to optically active π-stacked molecules. Bull Chem Soc Jpn 92:265–274
Morisaki Y, Hifumi R, Lin L, Inoshita K, Chujo Y (2012a) T practical optical resolution of planar chiral pseudo-ortho-disubstituted [2.2]paracyclophane. Chem Lett 41:990–992
Morisaki Y, Hifumi R, Lin L, Inoshita K, Chujo Y (2012b) Through-space conjugated polymers consisting of planar chiral pseudo-ortho-linked [2.2]paracyclophane. Polym Chem 3:2727–2730
Morisaki Y, Kawakami N, Nakano T, Chujo Y (2013) Energy transfer properties of a [2.2]paracyclophane-based through-space dimer. Chem Eur J 19:17715–17718
Morisaki Y, Kawakami N, Shibata S, Chujo Y (2014a) Through-space conjugated molecular wire consisting of three π-electron systems. Chem Asian J 9:2891–2895
Morisaki Y, Kawakami N, Shibata S, Chujo Y (2014b) Synthesis and properties of a through-space conjugated dimer. Chem Lett 43:426–428
Morisaki Y, Inoshita K, Chujo Y (2014c) Planar chiral through-space conjugated oligomers: synthesis and characterization of chiroptical properties. Chem Eur J 20:8386–8390
Morisaki Y, Gon M, Sasamori T, Tokitoh N, Chujo Y (2014d) Planar chiral tetrasubstituted [2.2]paracyclophane: optical resolution and functionalization. J Am Chem Soc 136:3350–3353
Morisaki Y, Inoshita K, Shibata S, Chujo Y (2015) Synthesis of optically active through-space conjugated polymers consisting of planar chiral [2.2]paracyclophane and quaterthiophene. Polym J 47:278–281
Morisaki Y, Sawada R, Gon M, Chujo Y (2016) New type of planar chiral [2.2]paracyclophanes and construction of one-handed double helices. Chem Asian J 11:2524–2527
Morisaki Y, Shibata S, Chujo Y (2017) [2.2]paracyclophane-based single molecular wire consisting of four π-electron systems can. J Chem 95:424–431
Muller G (2014) In luminescence of lanthanide ions in coordination compounds and nanomaterials. In: de Bettencourt-Dias A (ed). John Wiley & Sons, Chichester, U.K., pp 77–124
Müller S, Liepold B, Roth GJ, Bestmann HJ (1996) An improved one-pot procedure for the synthesis of alkynes from aldehydes. Synlett 1996:521522
Ohira S (1989) Methanolysis of dimethyl (1-diazo-2-oxopropyl) phosphonate: generation of dimethyl (diazomethyl) phosphonate and reaction with carbonyl compounds. Synth Commun 19:561–564
Oldham WJ, Miao YJ, Lachicotte RJ, Bazan GC (1998) Stilbenoid dimers: effect of conjugation length and relative chromophore orientation. J Am Chem Soc 120:419–420
Pamperin D, Hopf H, Syldatk C, Pietzsch M (1997) Synthesis of Planar Chiral [2.2]Paracyclophanes by Biotransformations: Kinetic Resolution of 4-Formyl[2.2]paracyclophane by Asymmetric Reduction. Tetrahedron Asym 8:319–325
Pamperin D, Ohse B, Hopf H, Pietzsch M (1998) Synthesis of planar-chiral [2.2]paracyclophanes by biotransformations: screening for hydrolase activity for the kinetic resolution of 4-acetoxy-[2.2]paracyclophane. J Mol Cat B Enzymatic 5:317–319
Paradies J (2011) [2.2]Paracyclophane derivatives: synthesis and application in catalysis. Synthesis 3749–3766
Parmar R, Coles MP, Hitchcock PB, Rowlands GJ (2010) Towards a flexible strategy for the synthesis of enantiomerically pure [2.2]paracyclophane derivatives: the chemistry of 4-tolylsulfinyl[2.2]paracyclophane. Synthesis 4177–4187
Pye PJ, Rossen K, Reamer RA, Tsou NN, Volante RP, Reider PJ (1997) A new planar chiral bisphosphine ligand for asymmetric catalysis: highly enantioselective hydrogenations under mild conditions. J Am Chem Soc 119:6207–6208
Riehl JP, Muller F (2012) Comprehensive chiroptical spectroscopy. Wiley and Sons, New York
Riehl JP, Richardson FS (1986) Circularly polarized luminescence spectroscopy. Chem Rev 86:1–16
Rossen K, Pye PJ, Maliakal A, Volante RP (1997) Kinetic resolution of rac-4,12-dibromo[2.2]paracyclophane in a palladium [2.2]phanephos catalyzed amination. J Org Chem 62:6462–6463
Rowlands GJ (2008) The synthesis of enantiomerically pure [2.2]paracyclophane derivatives. Org Biomol Chem 6:1527–1534
Rozenberg V, Sergeeva E, Hopf H (2004) In Gleiter R, Hopf H (eds) Modern cyclophane chemistry. Wiley-VCH, Weinheim, Germany, pp 435–462
Salhi F, Collard DM (2003) π-stacked conjugated polymers: the influence of paracyclophane π-stacks on the redox and optical properties of a new class of broken conjugated polythiophenes. Adv Mater 15:81–85
Salhi F, Lee B, Metz C, Bottomley LA, Collard DM (2002) Influenece of π-stacking. on the redox properties of oligothiophenes: (α-alkyloligo-thienyl)para[2.2]cyclophane. Org Lett 4:3195–3198
Sánchez-Carnerero EM, Agarrabeitia AR, Moreno F, Maroto BL, Muller G, Ortiz MJ, de la Moya S (2015) Circularly polarized luminescence from simple organic molecules. Chem Eur J 21:13488–13500
Sasai Y, Tsuchida H, Kakuta T, Ogoshi T, Morisaki Y (2018) Synthesis of optically active π-stacked compounds based on planar chiral tetrasubstituted [2.2]paracyclophane. Mater Chem Front 2:791–795
Sato S, Yoshii a, Takahashi S, Furumi S, Takauchi M, Isobe H (2017) Chiral intertwined spirals and magnetic transition dipole moments dictated by cylinder helicity. PNAS 114:13097–13101
Sawada Y, Furumi S, Takai A, Takeuchi M, Noguchi K, Tanaka K (2012) Rhodium-catalyzed Enantioselective synthesis, crystal structures, and photophysical properties of helically chiral 1,1’-bitriphenylenes. J Am Chem Soc 134:4080–4083
Sawada R, Gon M, Nakamura J, Morisaki Y, Chujo Y (2018) Synthesis of enantiopure planar chiral bis-(para)-pseudo-meta-type [2.2]paracyclophanes. Chirality 30:1109–1114
Sheng Y, Ma J, Liu S, Wang Y, Zhu C, Cheng Y (2016) Strong and reversible circularly polarized luminescence emission of a chiral 1,8-naphthalimide fluorophore induced by excimer emission and orderly aggregation. Chem Eur J 22:9519–9522
Sonogashira K (2002) In: Negishi E (ed) Handbook of organopalladium chemistry for organic synthesis. Wiley-Interscience, New York, pp 493–529
Takaishi K, Yamamoto S, Hinoide S, Ema T (2017) Helical oligonaphthodioxepins showing intense Circularly Polarized Luminescence (CPL) in solution and in the solid state. Chem Eur J 23:9249–9252
Tanaka H, Inoue Y, Mori T (2018) Circularly polarized luminescence and circular dichroisms in small organic molecules: correlation between excitation and emission dissymmetry factors. ChemPhotoChem 2:386–402
Tohda Y, Sonogashira K, Hagihara N (1975) A convenient synthesis of acetylenes: catalytic substitutions of acetylenic hydrogen with bromoalkenes, iodoarenes and bromopyridines. Tetrahedron Lett 16:4467–4470
Vögtle F (1993) cyclophane chemistry: synthesis, structures and reactions. John Wiley & Sons, Chichester
Vorontsova NV, Rozenberg VI, Sergeeva EV, Vorontsov EV, Starikova ZA, Lyssenko KA, Hopf H (2008) Symmetrically tetrasubstituted [2.2]paracyclophanes: their systematization and regioselective synthesis of several types of bis-bifunctional derivatives by double electrophilic substitution. Chem Eur J 14:4600–4617
Weiland KJ, Gallego A, Mayor M (2019) Beyond simple substitution patterns—symmetrically tetrasubstituted [2.2]paracyclophanes as 3D functional materials. Eur J Org Chem 3073–3085
Wielopolski M, Molina-Ontoria A, Schubert C, Margraf JT, Krokos E, Kirschner J, Gouloumis A, Clark T, Guldi DM, Martín N (2013) Blending through-space and through-bond π-π-coupling in [2,2’]-paracyclophane-oligophenylenevinylene molecular wires. J Am Chem Soc 135:10372–10381
Zhuravsky R, Starikova Z, Vorontsov E, Rozenberg V (2008) Novel Strategy for the synthesis of chiral pseudo-ortho-substituted hydrxy[2.2]paracyclophane-based ligands from the resolved 4-bromo-12-hydroxy[2.2]paracyclophane as a parent compound. Tetrahedron Asym 19:216–222
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Morisaki, Y. (2021). Circularly Polarized Luminescence (CPL) Based on Planar Chiral [2.2]Paracyclophane. In: Ooyama, Y., Yagi, S. (eds) Progress in the Science of Functional Dyes. Springer, Singapore. https://doi.org/10.1007/978-981-33-4392-4_10
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