12146-48-4Relevant academic research and scientific papers
Spectroscopic and magnetic studies of two electrically conducting charge-transfer compounds of 7,7,8,8-tetracyanoquinodimethanide with cationic copper chelates
Schwartz, Michael,Hatfield, William E.
, p. 2823 - 2825 (2008/10/08)
Electronic spectral data for [Cu(en)2][TCNQ]2 reveal a TCNQ- + TCNQ- → TCNQ0 + TCNQ2- charge-transfer band at 1220 nm. With a value for the transfer integral t of 0.2, a value for the Coulomb integral U of 1.3 eV may be estimated from the relationship ΔE(CT) = (U - 21/2t). A band gap is expected to open at the Fermi level for values of 4t/U ST is estimated to be 0.12 eV from the relationship ΔEST = 4t2/U. The lack of a contribution of paramagnetism from TCNQ- to that of [Cu(en)2][TCNQ]2 may be understood, even in the absence of charge transfer, since a system with ΔEST of 0.12 eV would exhibit a magnetic susceptibility of 10-5 emu/mol at 300 K. This small magnetic susceptibility cannot be detected in the presence of the molar magnetic susceptibility of [Cu(en)2][TCNQ]2. In addition to the TCNQ- + TCNQ- → TCNQ0 + TCNQ2- CT band, [Cu(phen)2][TCNQ]2 exhibits a TCNQ- + TCNQ0 → TCNQ0 + TCNQ- band at 2500 nm. The magnetic susceptibility of [Cu(phen)2][TCNQ]2 indicates that, on the average, one-third to one-half of an electron is transferred from each TCNQ site to [Cu(phen)2]2+, and the site preference energy E is 0.17-0.25 eV. Since E and t are comparable in magnitude, the bandwidth is appreciable, and high electrical conductivities and low activation energies are expected, and observed.
