Synthesis of Optically Active, X‐Shaped, Conjugated Compounds and Dendrimers Based on Planar Chiral [2.2]Paracyclophane, Leading to Highly Emissive Circularly Polarized Luminescence

Abstract

What promoted you to investigate this topic/problem? We achieved practical optical resolution of planar chiral 4,12-disub-stituted and 4,7,12,15-tetrasubstituted [2.2]paracyclophane compounds in 2012 and 2014, respectively.W eh ave prepared various conjugated compounds consisting of the di-or tetrasubstituted planar chiral [2.2]paracyclophane units. These compounds emit intense circularly polarized luminescence (CPL) with high photolumi-nescence (PL) quantum efficiencyinsolution, whereas the PL quantum efficiencyd ecreases dramatically in the solid state. We tried to overcome the problem of aggregation-caused quenching and obtain CPL-emissive thin films by taking advantage of ad endritic structure. What is the most significant result of this study? We could solve the above-mentioned problem completely;n amely, we achieved intense CPL from the dendrimer thin films with high PL quantum efficiencies. The dendrons sufficiently isolate the planar chiral [2.2]paracyclophane-containing conjugated core unit; this suppresses the aggregation-caused quenching of the core. In addition, the dendrons show al ight-harvesting effect and provide film-forming ability.T hus, the dendrimer films exhibited large molar extinction coefficients, high PL quantum efficiencies, intense PL and CPL, and large CPL dissymmetry factors. We realized gram-scale optical resolution and transformations of 4,7,12,15-tetrasub-stituted [2.2]paracyclophanes in this study. What other topics are you working on at the moment? We have been interested in "chirality". In particular,w eh ave fo-cused on the central chirality of the phosphorus atom in addition to the planar chirality of [2.2]paracyclophane. It is well known that the trivalent phosphorus atom in phosphine can act as ac hiral center because of the high inversion energy,u nlike that of nitrogen atoms. From this viewpoint, we have focused on P-chiral phos-phines and synthesized optically active P-chiral polymers, oligo-mers, and cyclic compounds using P-stereogenic bisphosphines as chiral building blocks. Recently,apractical synthetic route to P-ste-reogenic diphosphacrowns (crown ether derivatives consisting of chiral phosphorus atoms in the ring skeletons) was developed. Syntheses of various P-stereogenic phosphacrowns, investigations on the host-guest chemistry,a nd attempts for application to the field of materials chemistry are underway. Invited for the cover of this issue is YasuhiroM orisaki at Kwansei Gakuin University together with the group of Yoshiki Chujo at Kyoto University.T he image depicts the circularly polarizedl uminescence of the dendrimer films described in their Full Paper.R ead the full text of the article at

Circularly Polarized Luminescence: A Review of Experimental and Theoretical Aspects

“…Many more interesting applications of CPL than presented above have been reported in the literature, and a small sample of quite recent contributions, mainly from several laboratories in Japan, may be found in Refs. .…”

Remarkable Solvatofluorochromism of a [2.2]Paracyclophane‐Containing Organoboron Complex: A Large Stokes Shift Promoted by Excited State Intramolecular Charge Transfer

“…Thus, derivatives of 2 BF 2 that have a broad response range which is similar to that of Reichardt's dye should be applicable as high‐performance polarity sensors. The development of novel luminescent materials which take advantage of the unique properties of π‐conjugated paracyclophane systems is currently under investigation.…”

Beyond Simple Substitution Patterns – Symmetrically Tetrasubstituted [2.2]Paracyclophanes as 3D Functional Materials

“…To further explore the potential of X‐shaped conjugated structures with a central PC subunit, the same group attached dendrons via Sonogshira ‐type chemistry at the four alkynes of the enantiopure tetraalkyne 56 …”

“…Synthesis of the series of chiral CP comprising dendrimers 57 and the X‐shaped molecules 58 and 59 for aggregation studies, the extended model compounds 60 and 61 , which were analyzed as CPL emitters, and the V‐shaped model compound 63 …”