Charge-transfer ion pairs

PHOTOINDUCED ELECTROCHROMISM IN LB FILMS CONTAINING ION-PAIR CHARGE-TRANSFER COMPLEXES... 

Outer-sphere photoredox reactions are often interpreted as a consequence of ion-pair charge-transfer, IPCT [168] or charge-transfer to solvent, CTTS [92] excited states. In principle, however, any kind of excited state can be involved in such processes. 

IV. PHOTOINDUCED ELECTROCHROMISM OF ION-PAIR CHARGE-TRANSFER COMPLEXES IN VARIOUS MICROENVIRONMENTS... 

Molecules in the second coordination sphere, that is, solvent or partners of an ion pair, can transfer charge to the metal ion of a coordination complex in an optically induced electronic transition. The excited states are, respectively, known as solvent to metal charge transfer (SMCT) and ion pair charge transfer (IPCT) excited states. A typical example are the ion pairs, [Cora(NH3)6]3 +, X-, formed between [Coln(NH3)6]3 + and halide and pseudohalide ions X. The UV-Vis spectrum of ion... 

The monolayer also provides an environment of variable dielectric so that intermolecular association between photoactive molecules can readily occur. For example, molecular association of pyrene within a Langmuir-Blodgett film is clearly seen through time-resolved fluorescence measurements on the picosecond timescale [92], Attenuated total reflectance studies of dyes in cast films can similarly reveal their positions and photophysical interactions [93], Photochromism in a monolayer assembly has been attributed to excitation of ion-pair charge transfer complexes formed within the array [94]. 

Under special conditions still further transitions can be observed as (1) metal-to-metal (MMCT) or intervalence (IT) charge transfers characteristic for polynuclear complexes and (2) charge transfer to solvent (CTTS) or ion-pair-charge-transfer (IPCT) detectable in cases of fairly strong external interactions [3]. 

CTTS) or ion-pair-charge-transfer (IPCT) excitations, although other CT processes can be also assigned to the PET modes. 

In more recent years, a great number of studies have been reported by Kisch and co-workers (66-71) that involve ion-pair charge-transfer (IPCT) photochemistry of complex salts of the type A[M(SS)2], where A = organic acceptors... 

---