| The study of photo-induced linkage isomerism in transition metal complexes that contain ambi-dentate small ligands is very provocative. The challenges are great, but the outcome might be enormous. Sulfur dioxide complexes of ruthenium of general formula trans-[RuII(NH 3)4(SO2)X]Y (where X = Cl −, H2O or CF3COO− (TFA−)) and Y = Cl−, C6H 5SO3−, Tos− or TFA−)) were studied. Low temperature IR and DSC experiments indicated linkage isomerization of SO2, starting with η 1-planar S-bound to η2-side S,O-bound SO2 (MS2), after irradiation and confirmed the isomers to be metastable states. Photocrystallographic studies provided the direct evidence for the generation of photo-induced isomers and their geometry. Quantum chemical DFT calculations gave further support for the existence of such species and indicated that a third η1-O-bound (MSI) isomer might be observed. The FT-IR spectra of RuCO and RuDMSO complexes revealed the generation of the new photo-induced features, upshifted by 50–70 cm−1 for carbonyl compounds and downshifted by 160–187 cm−1 for DMSO complexes. However, the photo-induced species could not be unambiguously assigned to possible linkage isomers.; A series of copper(I) diimine complexes Cu(diimine)2 +, Cu(diimine)P2+, CuX(dmp)(PPh3) 0 suitable for the time-resolved X-ray diffraction experiments have been synthesized (diimine = 2,9-substituted 1,10-phenanthroline, P = phosphine ligand, X = halide, NCS). Their structures and photophysical properties have been studied. The structures Cu(II)Cl2dmp and Cu (II)Br2dmp complexes have been discussed as models for the MLCT excited states of the Cu(I) compounds. |
