Tg. Spence et al., INFLUENCE OF SEQUENTIAL SOLVATION ON METAL-TO-LIGAND CHARGE-TRANSFER IN BIS(2,2',2''-TERPYRIDYL)IRON(II) CLUSTERED WITH DIMETHYL-SULFOXIDE, The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory, 102(40), 1998, pp. 7779-7786
The first direct measurements of the contributions of individual solve
nt molecules to solvent reorganization associated with photoinitiated
charge transfer in a coordination complex are reported for gas-phase c
lusters of bis(2,2',2 ''-terpyridyl)iron(II), [Fe(terpy)(2)](2+), with
dimethyl sulfoxide (DMSO) prepared by electrospray ionization. Excita
tion of [Fe(terpy)(2).(DMSO)(n)](2+) clusters at wavelengths correspon
ding to the metal-to-ligand charge-transfer (MLCT) absorption characte
ristic of Fe(II)-polypyridine complexes in solution triggers evaporati
on of solvent molecules, permitting the application of laser photofrag
mentation mass spectrometry to monitor MLCT absorption. The energy of
the optical transition corresponding to MLCT E-op is reported for [Fe(
terpy)(2).(DMSO)(n)](2+) clusters (n = 1-11), and the cluster-size dep
endence of E-op is examined following Jortner's cluster-size-equation
approach (Jortner, J. Z. Phys. D 1992, 24, 247). The first 11 DMSO mol
ecules contribute 54-63% of the bulk solvent reorganization energy, ba
sed on estimates that E-op for the gas-phase [Fe(terpy)(2)](2+) comple
x falls between 1.860 x 10(4) and 1.876 x 10(4) cm(-1).