Binuclear Metal Complexes, XXXIX. Synthesis and Properties of Binuclear Copper(II) Complexes with [2-(2-Pyridyl)ethylamino]alkanols and [2-(2-Pyridyl)ethylthio]alkanols

Di-μ-alkoxo-bridged binuclear copper(II) complexes, Cu(py-3-3-nno)X, Cu(py-3-2-nso)X, and Cu(py-3-3-nso)X (X=Cl, Br, ClO4, NO3, PF6, BF4), have been synthesized and characterized, where Hpy-3-3-nno, Hpy-3-2-nso, and Hpy-3-3-nso denote 3-[2-(2-pyridyl)ethylamino]-1-propanol, 2-[2-(2-pyridyl)ethylthio]ethanol, and 3-[2-(2-pyridyl)ethylthio]-1-propanol, respectively. It was found that 2-[2-(2-pyridyl)ethylamino]ethanol (Hpy-3-2-nno) cannot form di-μ-alkoxo-bridged binuclear copper(II) complexes owing to the high strain in the fused ring system. These complexes exhibited a band at 22000–27000 cm−1 characteristic of the di-μ-alkoxo-bridged structure, the bands for Cu(py-3-2-nso)X and Cu(py-3-3-nso)X being lower in frequency compared with those for Cu(py-3-3-nno)X. Antiferromagnetic interaction was stronger and reduction potential (Cu(II)–Cu(II)→Cu(I)–Cu(I)) was higher for Cu(py-3-3-nso)X than those for Cu(py-3-3-nno)X. Cu(py-3-3-nso)Cl and Cu-(py-3-2-nso)Br showed two reduction waves at about +0.15 and −0.4 V vs. SCE. These results were discussed in terms of the structure in solution on the basis of conductivity measurements.