Zwitterionic pi-coordination compounds of copper(I) with monosubstituted alkynes: synthesis, crystal and electronic structure of two copper(I) halide pi-complexes with 4-amino-1-propargylpyridinium

摘要

Crystals of two mononuclear pi-coordination compounds of copper(I) halide with 4-amino-1-propargylpyridinium cation - [(HC equivalent to CCH2NC5H4NH2)CuBr2] (1) and [(HC equivalent to CCH2NC5H4NH2)CuCl1.61 Br-0.39] (2) - were obtained in the CuX-H2O-(HC equivalent to CCH2NC5H4 NH2)Br system (HC equivalent to CCH2N+C5H4NH2 is 4-amino-1-propargylpyridinium cation (app (+)), X=Cl or Br). The purity and identity of the synthesized compounds were verified by elemental analysis and IR spectroscopy. The compounds were structurally characterized using X-ray single crystal method and are isostructural. Both crystals are built of zwitterionic appCuX (2) units, in which triple C equivalent to C bond is coordinated to only one copper(I) ion. The Cu-m distance (m is the middle of the C equivalent to C bond) is 1.933(5) and 1.917(3) angstrom for 1 and 2, respectively. The predisposition of copper(I) halides to coordination polymer self-assembly through Cu-X center dot center dot center dot Cu bridge formation is not realized in 1 and 2. However, the equivalent to C-H center dot center dot center dot X and N-H center dot center dot center dot X hydrogen bonds along with pi-pi stacking of 4-aminopyridinium groups compensate an absence of the structure-forming interaction Cu-X center dot center dot center dot Cu. DFT calculations of an electron structure of [(app)CuCl2] were carried out (the restricted Hartree-Fock (RHF) method with a 6-31 G* orbital basis set). Calculated values of the charge density distribution on atoms as well as the constructed molecular orbitals (MOs) are in agreement with stereochemical parameters of the (Cu(I)-(C equivalent to C))-core of both coordination compounds.