EPR, magnetic, and structural investigations on the weak-exchange heisenberg linear chain bis(jv-methylphenazinium) bis(dicyanoethenedithiolato)cuprate(II), [(NMP)₂][Cu(mnt)₂]

The title compound [(NMP)₂] [Cu(mnt)₂] crystallizes in the monoclinic space group P2₁/n with a = 11.417 (2) Å, b = 8.126 (2) Å, c = 17.674 (7) Å, β = 92.11 (2)°, and Z = 2. The structure, including H, was solved by Patterson and Fourier methods and refined by full-matrix least squares to R = 0.048, based on 1944 observations. The compound forms a kind of mixed stack with a donor-acceptor sequence DAD-DAD along the a axis. The static susceptibilitymeasurements showed the exchange to be weak. Single-crystal EPR in the ac^* plane, where the two sites are magnetically equivalent, showed single exchange-narrowed Lorentzian lines with hyperfine dominated line width. The relative magnitudes of various Hamiltonians are H_Zee > H_ex > H_hyp > H_dip. The angular dependence of the line width in the ac^* plane along with the computed second moments was used to evaluate the high-temperature Fourier components of the autocorrelation function C(ʈ) and C²(ʈ). The computed nonsecular components were shown to follow from either the Blume-Hubbard model with J = 2100 G or from the Anderson-Weiss model with J = 1175 G.