Trinuclear cylinder-like potential anticancer and antibacterial Cu(i), Ag(i) and Au(i) nano-sized cationic complexes with tris-NHC ligands: cationic M metal cluster displaying positive or negative cooperativity in triad [L(R)→M] complexes?

N-Heterocyclic carbenes (NHCs) are a class of organic molecules containing a divalent carbon atom, known as a carbene, within a heterocyclic (ring) structure where nitrogen atoms (N) form part of the ring. These molecules have garnered significant attention in coordination chemistry due to their unique bonding properties, particularly as strong σ-donor ligands that facilitate the formation of stable complexes. A theoretical study was conducted to investigate the structural and bonding characteristics of M←C bonds in trinuclear, nano-sized Cu(i), Ag(i), and Au(i) cations with two tris-NHC ligands, which exhibit promising anti-cancer and antibacterial potential. The study employed natural bond orbital (NBO) techniques, energy decomposition analysis (EDA), and extended transition-state natural orbital for chemical valence (ETS-NOCV) methods to analyze the bonding interactions. The cooperativity values between bonds were also examined, revealing positive values indicative of anti-cooperativity within the complexes. The results further demonstrated that the M←C interactions are predominantly electrostatic in nature. These findings highlight the unique structural and electronic properties of the complexes, suggesting their potential as candidates for anti-cancer and antibacterial applications.