Picosecond time-resolved infrared spectroscopy of rhodium and iridium azides

Picosecond time-resolved infrared spectroscopy was used to elucidate early photochemical processes in the diazido complexes M(Cp*)(N3)2(PPh3), M = Rh (1), Ir (2), using 266 nm and 400 nm excitation in THF, CH2Cl2, MeCN and toluene solutions. The time-resolved data have been interpreted with the aid of DFT calculations on vibrational spectra of the singlet ground states and triplet excited states and their rotamers. While the yields of phototransformations via N2 loss are low in both complexes, 2 cleaves a N3 ligand under 266 nm excitation. The molecular structure of 1 is also reported as determined by single crystal X-ray diffraction.