Synthesis, structure and electrochemical properties of TCNQ lanthanide complexes

Five TCNQ (TCNQ = 7,7,8,8-tetracyano-p-quinodimethane) lanthanide complexes, namely, [Gd2(TCNQ)2(DMF)4(H2O)12][(TCNQ)4]·4H2O (1), [Gd(TCNQ)2(H2O)7][TCNQ]·6H2O·EtOH (2), [Gd2(TCNQ)4(H2O)8(CH3OH)2][(TCNQ)2]·2H2O (3), [Ln(TCNQ)2(H2O)6][TCNQ]·H2O·2MeOH [Ln = Ho (4), Ln = Yb (5)], have been synthesized by salt-elimination reactions. X-ray crystallographic analysis shows that 1–5 are discrete ionic complexes with monomer and dimer structure. Cyclic voltammograms, differential pulse voltammograms and the 1st–10th cycles CV for complexes 1–5 show the reversible one-electron oxidation and reversible one-electron reduction within the electrochemical window of CH3CN. Their electrochemical HOMO–LOMO gap and the reversibility are discussed.