Effects of Protonation and Metal Coordination on Intramolecular Charge Transfer of Tetrathiafulvalene Compound

摘要

A protonated bifunctional pyridine-based tetrathiafulvalene (TTF) derivative (DMT-TTF-pyH)N03 and a copper(II) complex Cu(acac)2(DMT-TTF-py)2 have been obtained and studied.Electronic spectra of the protonated compound show a large ICT (intramolecular charge transfer) band shift (DELTA lambda = 136 nm) compared with that of the neutral compound.Cyclic voltammetry also shows a large shift of the redox potentials (DELTA E_(1/2)(1) = 77 mV).Theoretical calculation suggests that the pyridium substituent is a strong pi-electron acceptor.Crystal structures of the protonated compound and the metal complex have been obtained.The dihedral angle between least-squares planes of the pyridyl group and the dithiole ring might reflect the intensity of the ICT effect between the TTF moiety and the pyridyl group.It is also noteworthy that the TTF moiety could be oxidized to TTF~(2+) dication by Fe(CIO4)3 centre dot 6H2O when forming a metal complex,while the protonated TTF derivative can only be oxidized to the TTF~(centare dot +) radical cation by Fe(ClO4)3 centre dot 6H2O even with an excess amount of the Fe(lll) salt,which can be used to control the oxidation process to obtain neutral TTF,TTF~(centre dot +) radical cation,or TTF~(2+) dication.