Circularly Polarized Luminescence in Supramolecular Assemblies of Chiral Bichromophoric Perylene Bisimides

Chiral bichromophoric perylene bisimides are demonstrated as active materials of circularly polarized emission. The bichromophoric system exhibited circularly polarized luminescence with dissymmetry factors typical of that of similar organic chiral chromophoric systems in the monomeric state. Variation in solvent composition led to the formation of stably soluble helical aggregates through intermolecular interactions. A large enhancement in the dissymmetry of circularly polarized luminescence was exhibited by the aggregated structures both in the solution and solid states. The sum of excitonic couplings between the individual chromophoric units in the self‐assembled state results in relatively large dissymmetry in the circularly polarized luminescence, thereby giving rise to enhanced dissymmetry factors for the aggregated structures. The spacer between chiral center and chromophoric units played a crucial role in the effective enhancement of chiroptical properties in the self‐assembled structures. These materials might provide opportunities for the design of a new class of functional bichromophoric organic nanoarchitectures that can find potential applications in the field of chiroptical memory and light‐emitting devices based on supramolecular electronics.     

Planar chirality of twisted trans-azobenzene structure induced by chiral transfer from binaphthyls

The absolute configuration of a binaphthyl-azobenzene dyad 2b, which has a chiral axis and a chiral plane, was determined by comparing the experimental circular dichroism (CD) spectra with the theoretical CD spectra calculated by the time-dependent (TD)-DFT method. The CD signals of the trans-azobenzene moiety indicated that the two benzene rings of this moiety are twisted unidirectionally. It is suggested that these dyads with shorter linkers may be suitable for use as chiroptical switches.     

Electric field induced nuclear spin resonance mediated by oscillating electron spin domains in GaAs-based semiconductors

We demonstrate an alternative nuclear spin resonance using a radio frequency (rf) electric field [nuclear electric resonance (NER)] instead of a magnetic field. The NER is based on the electronic control of electron spins forming a domain structure. The rf electric field applied to a gate excites spatial oscillations of the domain walls and thus temporal oscillations of the hyperfine field to nuclear spins. The rf power and burst duration dependence of the NER spectrum provides insight into the interplay between nuclear spins and the oscillating domain walls.     

Synthesis of poly(tert-butoxycarbonyl-p-phenylene): precursor to poly(p-phenylene)

Poly[2-(tert-butoxycarbonyl)-1,4-phenylene] ( 2 ) was prepared by the Ni-catalyzed polymerization of tert-butyl 2,5-dichlorobenzoate ( 1 ). The microstructure of polymer 2 was probably alternating head-to-head and tail-to-tail. This polymer was soluble in dipolar aprotic solvents, chloroform, tetrahydrofuran, and dichloromethane. Polymer 2 was saponified easily by thermal or acid treatment to yield poly[2-carboxy-1,4-phenylene] ( 3 ). Decarboxylation of polymer 3 in quinoline in the presence of copper(II) oxide produced poly(p-phenylene) (PPP) ( 4 ).