Asymmetrically Coordinated Heterodimetallic Ir-Ru System: Synthesis, Computational, and Anticancer Aspects.

Herein, we present an unprecedented formation of a heterodinuclear complex [{(ppy) 2 Ir III }(μ-phpy){Ru II (tpy)}](ClO 4 ) 2 {[ 1 ](ClO 4 ) 2 } using terpyridyl/phenylpyridine as ancillary ligands and asymmetric phpy as a bridging ligand. The asymmetric binding mode (N ∧ N-∩-N ∧ N ∧ C - ) of the phpy ligand in {[ 1 ](ClO 4 ) 2 } is confirmed by 1 H, 13 C, 1 H- 1 H correlated spectroscopy (COSY), high-resolution mass spectrum (HRMS), single-crystal X-ray crystallography techniques, and solution conductivity measurements. Theoretical investigation suggests that the highest occupied molecular orbital (HOMO) and the least unoccupied molecular orbital (LUMO) of [ 1 ] 2+ are located on iridium/ppy and phpy, respectively. The complex displays a broad low energy charge transfer (CT) band within 450-575 nm. The time-dependent density functional theory (TDDFT) analysis suggests this as a mixture of metal-to-ligand charge transfer (MLCT) and ligand-to-ligand charge transfer (LLCT), where both ruthenium, iridium, and ligands are involved. Complex {[ 1 ](ClO 4 ) 2 } exhibits Ru II Ir III /Ru III Ir III - and Ru III Ir III /Ru III Ir IV -based oxidative couples at 0.83 and 1.39 V, respectively. The complex shows anticancer activity and selectivity toward human breast cancer cells (IC 50 ; MCF-7: 9.3 ± 1.2 μM, and MDA-MB-231: 8.6 ± 1.2 μM) over normal breast cells (MCF 10A: IC 50 ≈ 21 ± 1.3 μM). The Western blot analysis and fluorescence microscopy images suggest that combined apoptosis and autophagy are responsible for cancer cell death.