Photophysical Properties and Photobiological Activitiesof Ruthenium(II) Complexes Bearing π‑Expansive CyclometalatingLigands with Thienyl Groups

A new family of cyclometalated ruthenium(II) complexes [Ru(N^N)2(C^N)]+ derived from the π-extended benzo[h]imidazo[4,5-f]quinolone ligand appended with thienyl groups (n = 1–4, compounds 1–4) was prepared and its members were characterized for their chemical, photophysical, and photobiological properties. The lipophilicities of 1–4, determined as octanol–water partition coefficients (log Po/w), were positive and increased with the number of thienyl units. The absorption and emission bands of the C^N compounds were red-shifted by up to 200 nm relative to the analogous Ru(II) diimine systems. All of the complexes exhibited dual emission with the intraligand fluorescence (1IL, C^N-based) shifting to lower energies with increasing n and the metal-to-ligand charge transfer phosphorescence (3MLCT, N^N-based) remaining unchanged. Compounds 1–3 exhibited excited state absorption (ESA) profiles consistent with lowest-lying 3MLCT states when probed by nanosecond transient absorption (TA) spectroscopy with 532 nm e...