Organic conductors derived from substituted tetraselenafulvalenes
A summary of some important molecular properties of several tetraselenafulvalenes(Photoelectron spectra, Electrochemistry,Mass spectra and optical absorbtion spectra) will be presented and the results compared with those obtained for the corresponding tetrathiafulvalenes.
The tetraselenafulvalenes in question form highly conducting charge-transfer salts with TCNQ and analogous compounds such as MTCNQ(Methyl-TCNQ) and DMTCNQ(Dimethyl-TCNQ), but often, depending on the conditions of crystallization, also insulating, diamagnetic (1:1) compounds can be isolated.
HMTSF-TCNQ exhibit unusual properties as a result of a more 3-dimensional character of the electronic states at low temperature(ref. 1 and 2). The 3-dimensional character is broken if small, amounts of MTCNQ or DMTCNQ are introduced in the lattice probably due to the increase in size of the dopants,when compared to TCNQ. Also the low temperature properties of HMTSF-TCNQ depend somewhat on the conditions of crystallization.
A new low symmetric donor DEDMTSF(DiethylDimethyltetraselenafulvalene) has been prepared. DEDMTSF-TCNQ (1:1) can be obtained in both a highly conducting and an insulating form. Preliminary results of the temperature dependent conductivity of single crystals of the conducting form will be reported.