Synthesis and Characterization of Thallium (￥2) Complexes with Tetracyanoquinodimethane, Tl(TCNQ)3 and TICl2(TCNQ)2.5

摘要

TlCl2(TCNQ)2.5 and Tl(TCNQ)3 were obtained from the reaction of LiTCNQ (TCNQ=tetracyanoquinodimethane) and TlX3 (X=Cl and NO3). These compounds were characterized by spectroscopic(IR, UV, EPR), electrochemical methods, and electrical conductivity measurements. Thermal analysis (TG, DSC) was also conducted. The room temperature electrical conductivities of these compounds are in the range of semiconductors. Spectroscopic studies indicate that Tl(TCNQ)3 has fully ionized TCNQ- ions in a form of simple salt, whereas TlCl2(TCNQ)2.5 is consisted of TCNQ- and TCNQ0 as a complex salt. EPR values of TCNQ- radical anion are 1.999 in both compounds and the signal attributable to metal ion is not observed, suggesting that any unpaired electrons are localized on TCNQ radicals, and metal atoms have diamagnetic state. Ligand decomposition and reduction process are simultaneously progressed in both compounds above at 200 ∩. The endothermic activation energy of TlCl2(TCNQ)2.5 is shown somewhat larger than that of Tl(TCNQ)3, it may be due to Tl-Cl bond strength. The mid-peak potentials of these compounds are very similar to those of TCNQ and the values of Epa and Epc are almost equal to 1. The wave of thallium ion is not detected in cyclic voltammogram, hence the redox processes of the complexes might be mainly localized to the TCNQ ligand rather than thallium ion.