A TDDFT study of the ruthenium(II) polyazaaromatic complex [Ru(dppz)(phen)2]2+ in solution

DFT/TDDFT calculations were performed to investigate the structural, electronic and optical properties of the [Ru(dppz)(phen)2]2+ complex in solution. TDDFT calculations in water show two groups of metal-to-ligand charge transfer (MLCT) transitions at ≈450 and 415 nm whose superposition gives account of the broad absorption band experimentally characterized at 440 nm. Also, a group of almost coincident MLCT transitions partially mixed with dppz intraligand π–π∗ transitions centered at ≈380 nm is found to give rise to the narrow absorption band experimentally found at 380 nm. Our results provide insight into the hypochromic shifts experimentally characterized upon intercalation of the title complex into DNA.