'Optimized route' to synthesize isoelectronic and isostructural Au(III)- and Pt(II)-NHC complexes: synthesis, structure, spectral properties, electrochemistry, and molecular docking studies

We report the synthesis, structures, luminescent properties, and electrochemistry of gold(iii) and platinum(ii)-N-heterocyclic carbene complexes. The proligand 1-methyl-2-(pyridylmethyl)imidazo[1,5-a]pyridin-4-ylium hexafluorophosphate, (1 & BULL;HPF6), and two novel isoelectronic and isostructural complexes, viz. [Au(1)(2)][PF6](3) (2), [Pt(1)(2)][PF6](2) (3), were synthesized and characterized by several spectroscopic studies. Finally, the single crystal X-ray diffraction studies established the square planar geometry of both complexes 2 and 3. The solid state structures of both the square planar complexes revealed two C-carbene and two N-pyridine present in trans fashion around the central metal ions. The complexes showed strong absorbance at & SIM;350 nm and DFT studies demonstrated the ILCT transition. Both complexes are luminescent at & SIM;400 nm. DFT and TDDFT studies were performed to gain insights into the experimental findings of solid-state structures and electronic properties. Electrochemical studies of Au(iii)-NHC complex 2 showed two irreversible Au(iii) & RARR; Au(i) and Au(i) & RARR;Au(0) reductions at -0.75 V and -1.28 V, whereas Pt(ii)-NHC complex 3 revealed Pt(ii/iv) two-electron reversible oxidation potential at 0.53 V. Molecular docking analysis revealed the highest free binding energy for complex 3 with human-DNA topoisomerase as compared to complex 2 and proligand 1 & BULL;HPF6. Pharmacokinetics studies revealed the scope of the complexes to be potent drugs.