Phenyl electron transfer bridge

Some bichromophoric systems, whose structure is based on the donor-bridge-acceptor principle, can undergo complete charge transfer, i.e. electron transfer. The resulting huge dipole moment in the excited state explains the very high sensitivity to solvent polarity of such molecules. An example is FP (l-phenyl-4-[(4-cyano-l- ... 

Chlorides RMe2CCH2Cl [(a) R = Me, R = Ph and (b) R = CH2Ph] reacted with diphenylphosphide ions in liquid ammonia, via a proposed 5rn 1 mechanism and their reactivities were measured. The higher reactivity of (a) has been attributed to efficient intramolecular electron transfer from the phenyl ring to the C—Cl a bond (intra-ET catalysis). The lower reactivity of (b) is ascribed to a decrease in the rate of the intra-ET by elongation of the bridge by one methylene unit. The relative reactivity of (a) versus (b) is proposed to indicate the ratio of the intra-ET rates of the radical anions of both compounds. ... 

Recently, new insight into detailed mechanisms of photochemical processes in donor-acceptor pairs (DA) has emerged. To study the role of bridge energy levels on electron transfer rates, a series of rod-like donor-bridge-acceptor (D-B-A) molecules in which a 4-aminonaphthalene-l,8-imide (ANI) electron donor is linked to a 1,8 4,5-naphthalenediimide acceptor (NI) via the 1,4 positions on a phenyl bridge was... 

Remarkably, subpicosecond injection rates were measured with Ru sensitizers anchored to a surface about 24 A from the semiconductor surface if the idealized Eiffel Tower-like orientation shown was achieved.118-120 Of course delocalization of the excited state onto the phenyl ethyne substituents of the bpy ligands would decrease the injection distance. Indeed, this bridge may act as a conduit for excited-state electron transfer to Ti02-12°... 

Sannicolo et al. first reported the electropolymerization of a Ceo-derivatized bridged bithiophenic precursor (235) [431]. Ferraris et al. have described the synthesis and the electropolymerization of a bithiophene with a Cgo group attached at P-position by an alkyl spacer (236), whereas processable PT copolymers were postfunctionalized with Cgo to give polymers [432]. Recently, PT with Cgo groups connected to the rr-conjugated polymer chain by a phenyl polyether linker has been prepared by electropolymerization of bithiophene 237 [427,433]. While the donor backbone and the acceptor moiety do not interact in the ground state, a photoinduced electron transfer between the PT chain and the attached Cgo group has been demonstrated by ESR measurements. 

Of course, the influence of the bridge on the degree of electronic coupling appears to be an excellent way to promote electron transfer from a donor to an acceptor. Fukuzumi, Kadish, and Crossley have reported the use of covalently linked chromophores in which electronic coupling is enhanced by a bridge that allows a coplanar orientation of the donor and the acceptor. In addition to the choice of a biphenyl type link, in which each phenyl is fused with the tetrapyrrolic rings, the subtlety of the hybrid dimer 23 depicted in Figure 13.24 is the use of a nonneutral dyad. 

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