Chemical bonding in some anticancer NHC complexes [R'C≡C → ML] (M=Cu (I), Ag (I), Au (I); R'=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 sigma-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 equivalent to C bonds. Also, the influence of changing L and R' groups in some adducts of [R'C equivalent to 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 [R'C equivalent to C -> MNHCR] and also P -> M and C-(alkenyl) -> M bonds in [R'C equivalent to 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 sigma donation from C-(alkenyl) to M atom in [R'C equivalent to C -> MPR3] complexes was greater than corresponding [R'C equivalent to C -> MNHCR] complexes. Also, the C-(alkenyl) -> M bonds in corresponding complexes were predominantly electrostatic. In addition, the C equivalent to 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 equivalent to C bond is related to covalent interaction.