Intramolecular charge transfer chromophores

R. K. Guo and S. Tazuke, Microheterogeneity oflocal segment mobility in solid polymethacrylates as studied by a polymer-bound twisted intramolecular charge transfer chromophore, Macromolecules 22, 3286 (1989). 

Related to these dimetallic systems, though not involving transition metals, are the boratastilbene complexes such as a " [ H 5 C 5 B-CH =CH-CH 4 -C H =C H P h ]" (isoelectronic with distyrylbenzene chromophores) that show aggregation-dependent photophysics. In nonpolar solvents, they form tightly bound ion pairs that are poorly luminescent, but in polar solvents, or when the counter ions are encapsulated in crown ethers, strong emission is observed as a result of intramolecular charge transfer.130... 

The optical properties of organic dyes (Fig. ld-f, Table 1) are controlled by the nature of the electronic transition(s) involved [4], The emission occurs either from an electronic state delocalized over the whole chromophore (the corresponding fluorophores are termed here as resonant or mesomeric dyes) or from a charge transfer (CT) state formed via intramolecular charge transfer (ICT) from the initially excited electronic state (the corresponding fluorophores are referred to as CT dyes) [4], Bioanalytically relevant fluorophores like fluoresceins, rhodamines, most 4,4 -difluoro-4-bora-3a,4a-diaza-s-indacenes (BODIPY dyes), and cyanines (symmetric... 

Fourfold Heck coupling (twofold on each dibromobenzene moiety) and Jeffery conditions has been applied on the two easily accessible tetrabromo[2.2]paracyclophane isomers 21 and 23, respectively, to prepare new double-layered 1,2- and 1,4-distyrylbenzene chromophoric systems 22-R and 24-R respectively, to enable studies of intramolecular charge-transfer phenomena in such systems (Scheme... 

We have reported further improvements in the photorefractive sensitivity of liquid crystals by doping with chromophores that undergo efficient photoinduced intramolecular charge transfer [24], The magnitude of the observed photorefrac-... 

Fig. 1 Schematic of the methodology used for intramolecular photoinduced charge separation in metal-organic charge-transfer chromophores...

Kato et al. (1983) studied PVK containing three different intramolecular charge-transfer complexes, each containing a carbazole donor chromophore and a tricyanovinyl acceptor. The results were compared to PVK TNF and PVKiTCNE (telracyanoethylene) intermolecular complexes. Relative to the intermolecular complexes, intramolecular complexes show high primary quantum yields. The thermalization distances were about 22 A, less than 28 to 35 A for the intermolecular complexes. Differences in the structure of the intramolecular complexes caused slight differences in the primary quantum yield, but did not cause significant differences in the thermalization distance. 

NLO properties. For different polyene series (Figure 1.13), the MLCT bands unexpectedly blue-shift as the number of ethylene units increases from one to three, and / o maximises at = 2. This behaviour is in marked contrast with known push-pull polyene organic chromophores, in which the tt-tt intramolecular charge transfer (ICT) bands red-shift as the number of ethylene units increases and the values increase steadily with Time-dependent (TD)-DFT calculations corroborate the... 

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