Comparison of Halide Donators Based on Pi···m (M = Cu, Ag, Au), Pi···h and Pi···halogen Bonds

The interactions in π/aromatic π/pseudo-π type complexes of C2H4/C2H2/C6H6/(CH2)3···MX (M = Cu, Ag, Au; X = F, Cl, Br, I) were researched by theoretical calculation at the wB97XD/aug-cc-pVTZ level and compared with the isomorphous C2H4/C2H2/C6H6/(CH2)3···HX/YX (X = F, Cl, Br; Y = Cl, Br) complexes. Results indicate that non-bonded interactions, namely π/aromatic π/pseudo-π···Cu/Ag/Au, contribute to the stability of the resulting dimers except for (CH2)3···AuF. The interaction energies of C2H2/C2H4/C6H6/(CH2)3···MX reduced with the decrease in electronegativity F > Cl > Br > I. The order is Au > Cu > Ag in C2H4/C2H2/C6H6···MX complexes. The interaction energies are π···MX > aromatic π···MX > pseudo-π···MX > π/aromatic π/pseudo-π···HX/YX with the sequence Cu > Au > Ag. The charge transfer of most complexes is from the bonding orbital (πC–C) of C–C bonds to antibonding orbital of MX monomers and occupied orbitals of the metal back-donation into the πCC* antibonding orbital of the π-system. (CH2)3···AuF has the unique largest interaction energy (− 89.31 kcal/mol) with the charge transfer from σC–Au to \( \sigma_{{{\text{C}}{-}{\text{Au}}}}^{*} \) because it formed two stable coordination bonds.