Crystal structure and thermal characterisation of a theophyllinato Cu(II) complex with benzylamine

Abstract

Diaquabis(benzylamine)bis(theophyllinato)copper(II) (1) was prepared and characterised by FTIR spectroscopy and thermogravimetry. Its molecular structure was determined by single crystal X-ray diffraction. 1 crystallises in triclinic crystal system, space group P-1 (No. 2), a = 8.108(1) Å, b = 9.597(2) Å, c = 11.216(2) Å, α = 82.36(1)°, β = 71.19(1)°, γ = 68.42(1)°. Z = 2, ρ = 1.453 Mg m-3, μ = 0.770 mm -1, R = 0.0546. The copper ion is located at an inversion centre and surrounded by two theophyllinate anions (bound via N7), two benzylamines (bound via N) and two water molecules in an octahedral trans arrangement. The complex molecules are connected forming a chain by hydrogen bonds of the water molecules (to N9 and O6 atoms of neighbouring theophyllinato moieties). No chelation of O6 of the theophyllinato anions to Cu2+ occurs. The thermal loss of water molecules at 120°C results in a structural transformation as indicated by powder XRD. On further heating first the benzylamine molecules are lost, then the theophyllinato moieties are degraded. The final residue is CuO in air at 500°C.