Computer-aided electron paramagnetic resonance spectroscopy in the speciation of pH-dependent equilibria for copper {[2,2′-[1-(1-ethoxyethyl)-1,2-ethanediylidene]bis[N,N-dimethylhydrazinecarbothioamidato]](2-)N2,N2′,S,S′} complex

Abstract

An extensive reinvestigation of EPR spectra of [{2,2′-[1-(1-ethoxyethyl)-1,2-ethanediylidene]bis[N,N-dimethyl-hydrazinecarbothioamidato]}(2-)N²,N²′,S,S′]copper(II)(CuKTSM₂) was performed over a large pH range at room temperature. A thorough speciation was possible only by massive use of computer simulation of spectra at room temperature and careful exploration of linewidth details. EPR data vs. pH for CuKTSM₂ clearly establishes the existence in solution of two distinguishable forms, at pH = 1.7 and at pH = 6.4. Spin Hamiltonian parameters and the correlation time were precisely discriminated by a new strategy based on computer-aided EPR spectroscopy and the choice of a suitable microwave frequency.