Evaluation of the Influence of a Thioether Substituent on the Solid State and Solution Properties of N3S-ligated Copper(II) Complexes
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The Royal Society of Chemistry
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Admixture of a N3S(thioether) ligand having two internal hydrogen bond donors (pbnpa: N-2-(phenylthio)ethyl-N,N-bis-((6-neopentylamino-2-pyridyl)methyl)amine; ebnpa: N-2-(ethylthio)ethyl-N,N-bis-((6-neopentylamino-2-pyridyl)methyl)amine) with equimolar amounts of Cu(ClO4)2·6H2O and NaX (X = Cl−, NCO−, or N3−) in CH3OH/H2O yielded the mononuclear Cu(II) derivatives [(pbnpa)Cu–Cl]ClO4 (1), [(ebnpa)Cu–Cl]ClO4 (2), [(pbnpa)Cu–NCO]ClO4 (3), [(ebnpa)Cu–NCO]ClO4 (4), [(pbnpa)Cu–N3]ClO4 (5), and [(ebnpa)Cu–N3]ClO4 (6). Each complex was characterized by FTIR, UV-VIS, EPR, and elemental analysis. Complexes 1, 2, 3 and 6 were characterized by X-ray crystallography. The structural studies revealed that [(pbnpa)Cu–X]ClO4 derivatives (1, 3) exhibit a distorted square pyramidal type geometry, whereas [(ebnpa)Cu–X]ClO4 complexes (2, 6) may be classified as distorted trigonal bipyramidal. EPR studies in CH3OH/CH3CN solution revealed that 1–6 exhibit an axial type spectrum with g∥ > g⊥ > 2.0 and A∥ = 15–17 mT, consistent with a square pyramidal based geometry for the Cu(II) center in each complex. A second species detected in the EPR spectra of 2 and 6 has a smaller A∥ value, consistent with greater spin delocalization on to sulfur, and likely results from geometric distortion of the [(ebnpa)Cu(II)–X]+ ions present in 2 and 6.