Theoretical Studies on the Structures and Spectroscopic Properties of N-Heterocyclic Carbene-pyridine-based Ruthenium Sensitizers

Using bidentate N-heterocyclic carbene-pyridine ligands in substitution for two thiocyanates of the N749, a series of novel thiocyanate-free cyclometalated ruthenium polypyridine complexes (1-4) was designed. These complexes were studied theoretically using density functional theory(DFT) and time-dependent density functional theory(TD-DFT) techniques to explore their geometry structures, electronic structures and the spectral properties. The calculations indicate that the lowest-energy absorption of complexes 1-4 in CH3 CN solution is calculated at around 800 nm, arise from the MLCT/LLCT transition.