NEW SUPERCONDUCTING INTERCALATION COMPOUNDS OF ORGANIC 5-MEMBERED HETEROCYCLIC-COMPOUNDS WITH 2H-TANTALUM DISULFIDE

The intercalation compounds TaS2(pyrrole)0.5 (1), TaS2(2-methylpyrrole)0.33 (2), TaS2(2,5-dimethylpyrrole) (3), TaS2(thiazole)0.33 (4) and TaS2(imidazole)0.33 (5) are formed readily in closed systems at temperatures up to 200-degrees-C. Furane and thiophene show no tendency to intercalate in 2H-TaS2. Compounds 2-5 are molecular intercalation species, and deintercalation is finished at 350-degrees-C, while in 1 the pyrrole guests have been associated and thermally induced deintercalation proceeds up to 900-degrees-C with fragmentation. 1-5 can be indexed on the basis of hexagonal symmetry assuming the space group P6(3)/mmc. In 1 the stacking sequence of the host lattice TaS2 remains unchanged while in 2, 3 and 5 a transformation from the BaB CaC stacking of 2H-TaS2 to a sequence AbA AcA occurs. In 4 a stacking CbC BcB like in MoS2 is realized. 1-5 show superconducting behaviour at low temperatures, 2 exhibits a pronounced metal-semiconductor transition at 220 K.