Tuning of electronic properties of one-dimensional cyano-bridged CuII-NiII, CuII-PdII, and CuII-PtII bimetallic assemblies by stereochemistry of ligands

Preparations, XPS and electronic spectroscopy, and magnetism of seven new one-dimensional cyano-bridged coordination polymers, chiral [Cu(RR-chxn)(2)][Pd(CN)(4)] center dot 2H(2)O (1), [Cu(trans-chxn)(2)][M(CN)(4)] center dot 2H(2)O (2, 4, and 6 for M = Pd, Ni, and Pt), and [Cu(cis-chxn)(2)][M(CN)(4)] center dot 2H(2)O (3, 5, and 7 for M = Pd, Ni, and Pt) (RR-chxn = cyclohexane-(1R,2R)-diamine, trans-chxn = racemic trans-cyclohexane-(1,2)-diamine, and cis-chxn = racemic cis-cyclohexane-(1,2)-diamine) have been reported in view of tuning of their electronic properties by stereochemistry of chxn ligands and metal-substitution. Comparison of Cu 2p(1/2) and 2p(3/2) peaks of XPS and broad d-d bands around 18 000 cm(-1) of electronic spectra are described systematically for 1-7. Variable-temperature magnetic measurement shows that complexes 1-7 indicate weak anti ferromagnetic interactions via cyano-bridges. Because of semi-coordination coupled with pseudo Jahn-Teller elongation and electrostatic interaction for 1, the axial Cu-N coordination bond distances of 2.330(7) and 3.092(8) angstrom are considerably longer than those of equatorial ones in the range from 2.016(6) to 2.030(6) angstrom. The former bond distances of 1 are intermediate values among the related Ni (2.324(6) and 3.120(8) angstrom) and Pt (2.34(1) and 3.09(1) angstrom) complexes. (c) 2007 Elsevier B.V. All rights reserved.