Chemical bonding in some anticancer NHC complexes [RʹC≡C → ML] (M=Cu (I), Ag (I), Au (I); Rʹ=C10H7 and C9NH12SO2; L=NHC (R) and P (R)3; and R=F, Cl, Br, H, CH3, SiH3, Ph)

Among the new complexes, metal N-heterocyclic carbene (NHC) complexes have recently gained remarkable attention as they are entirely appropriate prerequisites for effective drug design and quick optimization. Furthermore, N-heterocyclic carbenes (NHCs) like phosphines contain strong σ-donating properties, which can bind to metals and create stable complexes. This article reports a general theoretical discussion on the structures and nature of C_{(carbene/alkenyl)} → M, P → M and C≡C bonds. Also, the influence of changing L and Rʹ groups in some adducts of [RʹC≡C → ML], (M=Cu (I), Ag (I), Au (I); R'=C₁₀H₇, C₉NH₁₂SO₂; L=NHC (R), P (R)₃; and R=F, Cl, Br, H, CH₃, SiH₃, Ph) has been studied. In this context, DFT calculations by PBE-D3/def2-TZVP level of theory have been used. The nature of C_{(carbene/alkenyl)} → M bonds in [RʹC≡C → MNHCR] and also P → M and C_(alkenyl) → M bonds in [RʹC≡C → MPR₃] complexes was surveyed. This was done using natural bond orbital (NBO), atoms in molecules (AIM), energy decomposition analysis (EDA), and energy decomposition analysis natural orbital for chemical valence (EDA-NOCV). The data have shown that σ donation from C_(alkenyl) to M atom in [RʹC≡C → MPR₃] complexes was greater than corresponding [RʹC≡C → MNHCR] complexes. Also, the C_(alkenyl) → M bonds in corresponding complexes were predominantly electrostatic. In addition, the C≡C bond has been also investigated by applying AIM, EDA, and ETS-NOCV analysis. The outcomes indicate that the highest percentage of interaction energy for C≡C bond is related to covalent interaction.