A New Molecular Magnetic Semiconductor Based on Tetrathiafulvalene (ttf) and Oxamato Ligand (opba): [ttf](2)[Cu(opba)]center dot H2O

摘要

An oxamato-based compound of formula [ttf](2)[Cu(opba)]center dot H2O, with ttf = tetrathiafulvalene and opba = ortho-phenylenebis(oxamato), has been prepared and characterized. The complex was obtained by metathesis from (ttf)(3)(BF4)(2) and (Bu4N)(2)[Cu(opba)] in acetonitrile at room temperature. The UV-Vis-NIR spectrum reveals the presence of the radical cation in two forms, (ttf(center dot+)) and (ttf(center dot+))(2) dimer. The electronic transport properties of [ttf](2)[Cu(opba)]center dot H2O were studied by impedance spectroscopy (IS) and linear voltammetry (LV), and show a typical semiconductor behavior. The EPR spectra exhibit two superposed lines corresponding to electron spins of Cu-II ions and ttf(center dot+) radical cations. The dc magnetic properties show a room temperature value of the chi T-M product close to that expected for three uncoupled S = (1)/(2) spins and a value of 0.13 emu K mol(-1) at low temperature (4 K). The chi T-M vs. T curve was fitted and the best model consists of a term for a (ttf(center dot+))(2) dimer (Bleaney-Bowers, leading to J(2) = -186 cm(-1)) and a second term related to an antiferromagnetic {Cu center dot center dot center dot ttf(center dot+)} chain (J(1) = -10.1 cm(-1)).