New Organic Metals Based on BDH‐TTP Radical Cation Salts with the Photochromic Nitroprusside Anion [FeNO(CN)₅]^2–

Abstract

Abstract Three new 2,5‐bis(1,3‐dithiolan‐2‐ylidene)‐1,3,4,6‐tetrathiapentalene (BDH‐TTP) radical cation salts with the photochromic nitroprusside anion have been synthesized: κ‐(BDH‐TTP) 4 [FeNO(CN) 5 ]·NB ( 1 ), κ‐(BDH‐TTP) 4 [FeNO(CN) 5 ] ( 2 ), and (BDH‐TTP) 2 [FeNO(CN) 5 ] ( 3 ). The salts were characterized by single‐crystal X‐ray diffraction, electrical resistance measurements, and electronic band structure calculations. The crystals of 1 and 2 have a layered structure in which the BDH‐TTP layers of κ‐type alternate with anionic sheets. Solvent (nitrobenzene) molecules are also involved in the composition of the anion sheet of 1 . The crystals of 1 have triclinic symmetry and two crystallographically independent BDH‐TTP radical cations in the unit cell, while there is only one independent radical cation in the monoclinic structure of 2 . The salts 1 and 2 are stable quasi‐2D metals down to 4.2 K, while 3 , with full charge transfer, is a semiconductor with low conductivity at room temperature. It is suggested that the κ‐type layers of BDH‐TTP are more robust than those of BEDT‐TTF and its derivatives and the consequences for the electronic structure are discussed.