Synthesis, characterization, biomolecular interaction, potent aqueous singlet oxygen generation and NADH photo-oxidation of phenanthroline-based cyclometalated Ir(iii) complexes

Abstract

Cyclometalated iridium complexes have been a great choice for PDT agents over the last few decades. Herein, we endeavoured to introduce a newly synthesized Ir(III) complex [LIr], focusing on its photophysical properties, DNA interactions, and catalytic potential. DNA-binding studies indicated a combination of binding interactions with notable affinity (K = 1.04 × 10⁵ M⁻¹) and a high Stern–Volmer quenching constant (K_SV = 7.35 × 10⁹ M⁻¹), suggesting strong DNA association, while UV-visible spectroscopy confirmed robust MLCT transitions. The complex efficiently generated singlet oxygen with a quantum yield of 0.0613, highlighting its potential for photodynamic therapy. Additionally, it demonstrated moderate catalytic activity in NADH oxidation, with a turnover number (TON) of 4.22 and a turnover frequency (TOF) of 8.46 h⁻¹, both enhanced under visible light, thereby establishing complex [LIr] as a promising future candidate for DNA-targeted therapies and photoactivated catalysis.