Spectroscopic studies of electronic structure of copper(II) ethanolamine complexes in solutions and in impregnated wood

Optical and electron paramagnetic resonance (EPR) spectra were recorded for a series of Cu(II) complexes with monoethanolamine (EA) and the quaternary ammonium compound (QAC) alkyldimethylbenzylammonium chloride in aqueous solution with H₃BO₃ which are tested as modern impregnating solutions for wood preservation. It is proved that in aqueous solutions of Cu-EA the octahedral complexes I, Cu(EA)₂(H₂O)₂, exist with water in apical positions. The addition of the QAC results in an exchange of water for nitrogen of the QAC molecules with a possible partial destruction of the coordinating molecule (complex II). The detailed electronic structure is determined for both species I and II. Boric acid does not influence the complex structures. In the treated wood (Pinus silvestris L.) the complex I is destroyed and Cu(EA)₂ is attached to the OH groups of cellulose molecules, forming a stable complex. The complexes II still exist in wood, but with higher-concentration impregnating solution a part of these complexes is destroyed by coordination to the OH groups of cellulose molecules.