A flame retardant-hardener for epoxy resins: Synthesis, structural, and DFT studies of the [Cu(H2NC2H4NH2)2(H2O)Cl]Cl complex.

Abstract

The aqua-bis(ethylenediamine)-chloro-copper(II) chloride complex, [Cu(en)2(H2O)(Cl)]Cl (1), was synthesized by direct interaction of CuCl2×2H2O with pepa (pepa is a polyethylenepolyamine containing ethylenediamine (en)). The crystalline complex 1 was characterized by IR spectra and structurally studied. Crystals of this complex consist of the [Cu(en)2(H2O)(Cl)]+ discrete cations, whose Cu2+ ion is chelated by two en molecules. The Cu(II) coordination polyhedron has the shape of an elongated square bipyramid, in which four nitrogen atoms of the -NH2 groups of en molecules form the base of this bipyramid, and the oxygen atom of the water molecule and Cl- are in its apical positions. Three-dimensional framework 1 is formed due to hydrogen bonds O-H…Cl and N-H…Cl. The Cu(II)-(H2NC2H4NH2) chelation was studied by DFT using the 6-31G* basis set. The calculated electron-stereochemical parameters are in good agreement with the ability of complex 1 to simultaneously be a flame retardant and a curing agent of epoxy resins.