Effect of hydrogen bonding on coordination in trans-di(Z-aminobenzoato-O)di(1,3-diaminopropane-N,N′)copper(II) (Z= 2, 3 or 4) complex units

Article abstract of DOI:10.1016/s0020-1693(97)05702-2

The crystal structures of the series of compounds containing the di(Z-aminobenzoato-O)di(1,3-diaminopropane-N,N′)copper(II) (Z= 2, 3 or 4) coordination units were determined by single-crystal X-ray methods. In the ortho- and me/a-aminobenzoate analogues the structures are composed of monomeric complex units, where a copper(II) cation is located at a centre of symmetry and the chelate rings display a chair conformation. The benzoate anions in the axial positions are coordinated via one oxygen only. In the para-aminobenzoate analogue the complex units are similar, but there are two additional crystal water molecules in the asymmetric unit. The main differences between the three coordination units are seen in the bite angle of a chelate ring and the declination value of a benzoate anion. The differences are likely due to variation in the participation of an amine group of a chelate ring and a carboxylate group of a benzoate anion to form a hydrogen bonding network. Intramolecular hydrogen bonding seems to be correlated with inclination of a benzoate anion. Small inclination and absolute declination values for a benzoate anion seem to be related with bifurcated intramolecular hydrogen bonding and narrowing of a bite angle N-Cu-N. The hydrogen bonding to the coordinated oxygen atom changes its hybridisation from approximate sp² towards sp³. The existence of hydrogen bonding is supported by IR spectra. The crystallographic data are as follows (tn: 1,3-diaminopropane; bzO: a benzoate anion): [Cutn₂(2NH₂bzO)₂], C₂₀H₃₂CuN₆O₄, monoclinic, space group P2₁/a No. 14, a = 10.513(2), b = 9.1789(12), c= 12.126(2) ?, β = 99.82(2)°, V = 1153.0(4) ?³; [Cutn₂ (3NH₂bzO)₂], C₂₀H₃₂CuN₆O₄, monoclinic, space group P2₁/n No. 14, a = 6.7128(12), b = 16.503(4), c=10.268(2) ?, β = 92.022(15)°, V= 1136.8(4) ?³; [Cutn₂(4NH₂bzO)₂] · 2H₂O, C₂₀H₃₆CuN₆O₆, monoclinic, space group P2₁/n No. 14, a = 9.484(2), b = 8.938(2), c= 16.301(3) ?, β = 103.910(14)°, V= 1334.6(5) ?³.