A novel Dinuclear rhenium(I) Tricarbonyl complex as a potential anticancer agent: Synthesis, structural...

Rhenium tricarbonyl complexes in their monometallic forms have been extensively studied, mainly for their potent inhibitory activity against cancer cells. However, far fewer dinuclear complexes have been investigated for similar applications. In this study, we report the synthesis, crystal structure, DFT analysis, in vitro biological screening, and in silico molecular docking of the complex NEt₄[{Re(CO)₃}₂-μ-(OCH₃)₂-μ-(3,5-Me₂py)], C1 (where OCH₃ = methoxy; 3,5-Me₂py = 3,5-dimethyl-1H-pyrazolate). This dinuclear complex, C1, was characterised spectroscopically by FT-IR, ¹H and ¹³C NMR, UV-Vis, as well as single-crystal X-ray diffraction. Preliminary in vitro screening at a single dose of 10 μM in DMSO revealed excellent cytotoxicity of C1 against cervical (HeLa and CaSki), pancreatic (PANC-1 and CFPAC-1), and breast (MCF-7) cancer cell lines. It was further evaluated for its half-maximal inhibitory concentration (IC₅₀) which was determined as 1.59 ± 0.34 (SI = 6.39), 1.06 ± 0.35 (SI = 9.59), 0.74 ± 0.22 (SI = 13.73), 3.58 ± 0.10 (SI = 2.83) and 2.24 ± 0.45 (SI = 4.54) μM against HeLa, CaSki, CFPAC-1, PANC-1 and MCF-7, respectively, while the IC₅₀ against MRC-5 (non-cancerous human fibroblast cells) was 10.16 ± 0.8 μM. The DFT calculations indicated that C1 is both reactive and conductive, with an energy gap (E_HOMO-E_LUMO) of 4.11 eV. Additionally, C1 was docked against tubulin to illustrate its potential binding modes to the target tubulin, and the in silico molecular docking results revealed binding affinities ranging from -5.43 to -4.37 kcal/mol.