Nature of Metal-Drug Bond in Some Antitumor Active Complexes of Coinage Metal Ions

Abstract

N-Heterocyclic carbene and phosphine can be labeled as solid σ-donor ligands and can contribute to stable complexes. In addition, the constructed complex can accommodate a wide variety of applications, such as pharmaceutical products. In the light of this, a theoretical analysis was carried out on the existence of metal-drug interactions of group 11 metal ions in coordination with symmetrical unsaturated N-heterocyclic carbenes [NHC(R)(R')] and monodentate phosphine (PR₃). The R substitutes on N atoms in NHC and phosphines are identical, and R' substitutes are located on two noncarbenic carbon atoms (C4 and C5) in the heterocycle complexes. All complexes are in general formula, [Tgt → ML] {where M = Cu(I), Ag(I), Au(I), Tgt = 2,3,4,6-tetra-O-acetyl-1-thio-β-d-glucopyranoside, L= [NHC(R)(R')], and PR₃; R = F, Cl, Br, H, CH₃, C₂H₅, SiH₃, 2,6-diisopropylphenyl; R' = H and Ph} at the PBE-D3/def2-TZVP level of theory. Findings show greater tolerance for the release of drugs in the presence of Ag(I) metal ions than the other metal ions studied here. Applying natural bond orbital (NBO), atoms in molecules (AIMs), energy decomposition analysis (EDA), and extended transition-state natural orbital for chemical valence (ETS-NOCV) analysis have been researched in order to ascertain the nature of M ← S and M ← C (M ← P) bonds in the complexes. Results have shown that σ donation from S to M atoms in [Tgt → MPR₃] complexes is better and the π acceptor is weaker than the corresponding [Tgt → MNHC(R)(R')] complexes.

Scheme 1. Schematic Representation of the [Tgt → MNHC(R)(R′)] and [Tgt → MP(R)₃] Complexes [M = Cu(I), Ag(I), Au(I); R = F, Cl, Br, H, CH₃, C₂H₅, SiH₃, 2,6-Diisopropylphenyl; R′ = H and Ph]

Figure 1

Optimized structures of [Tgt → MNHC(R)(H)][M = Cu(I), Ag(I), Au(I); R = F, Cl, Br, H, CH₃, SiH₃, 2,6-diisopropylphenyl; R′ = H] complexes of the investigated here at the mentioned level of theory.

Figure 2

Optimized structures of [Tgt → MP(R)₃] [M = Cu(I), Ag(I), Au(I); R = F, Cl, Br, H, CH₃, C₂H₅, SiH₃, 2,6-diisopropylphenyl] complexes of the investigated here at the mentioned level of theory.

Figure 3

Optimized structures of[Tgt → MNHC(R)(Ph)][M = Cu(I), Ag(I), Au(I); R = F, Cl, Br, H, CH₃, SiH₃, 2,6-diisopropylphenyl; R′ = Ph] complexes of the investigated here at the mentioned level of theory.

Figure 4

Calculated ΔE_int vs electron density (ρ) for the M–S bond of [Tgt → MNHC(R)(H)] [M = Cu(I), Ag(I), Au(I); R = F, Cl, Br, H, CH₃, SiH₃, 2,6-diisopropylphenyl; R′ = H].

Figure 5

Calculated ΔE_int vs electron density (ρ) for the M–S bond of [Tgt → MPR₃][M = Cu(I), Ag(I), Au(I); R = F, Cl, Br, H, CH₃, SiH₃, 2,6-diisopropylphenyl].

Figure 6

Deformation densities associated with the most important orbital interactions for [Tgt → CuNHC(CH₃)(H)] and [Tgt → CuP(CH₃)₃] complexes at the BP86-D3/TZ2P(ZORA)//PBE-D3/def2-TZVP level of theory.

Figure 7

Deformation densities associated with the most important orbital interactions for [Tgt → CuNHC(F)(H)] and [Tgt → CuP(F)₃] complexes at the BP86-D3/TZ2P(ZORA)//PBE-D3/def2-TZVP level of theory.