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2,2‘-Bis(3-(2-pyridyl)-1-methyltriazolyl)biphenyl:  A Tetracoordinating Wrapping Ligand Inducing Similar Skew Coordination Geometries at Copper(I) and Copper(II)

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journal contribution
posted on 27.03.1996, 00:00 by Edgar Müller, Gérald Bernardinelli, Jan Reedijk
The synthesis of a new wrapping ligand, 2,2‘-bis(3-(2-pyridyl)-1-methyl-1,2,4-triazol-5-yl)biphenyl (mbptb) is described. This ligand induces similar, about 45°-crossed (skew) coordination geometries at both the Cu(I) and the Cu(II) ion. Both [CuI(mbptb)]ClO4 and [CuII(mbptb)](ClO4)2 were characterized by X-ray structure determinations, UV/vis spectroscopy, and electrochemical measurements. The electronic spectrum of the orange Cu(I) complex shows two metal-to-ligand charge transfer bands at 442 and 340 nm, with extinctions ε of 1300 and 2600 M-1 cm-1 respectively, corresponding to excitations into the lowest and the second lowest unoccupied ligand MO. The turquoise Cu(II) compound shows a broad d−d transition with a maximum at 799 nm (ε = 73.4 M-1 cm-1) with a shoulder at 690 nm, as well as a ligand-to-metal charge transfer transition at 344 nm (ε = 55 M-1 cm-1). The CuII/CuI potential (in acetonitrile) is 0.53 V (NHE).