Crystal structure of the charge-transfer complex 2-(1,2,3,4-tetrahydronaphthalen-1-ylidene)hydrazinecarbothioamide–pyrazine-2,3,5,6-tetracarbonitrile (2/1)

The reaction of 2-(1,2,3,4-tetrahydronapthalen-1-ylidene)hydrazinecarbothioamide (TTSC) with pyrazine-2,3,5,6-tetracarbonitrile (tetracyanopyrazine, TCNP) yields the title 2:1 charge-transfer adduct, 2C11H12N3S·C6N8. The complete TCNP molecule is generated by a crystallographic inversion centre and the non-aromatic ring in the TTSC molecule adopts an envelope conformation with a methylene C atom as the flap. In the crystal, the thiosemicarbazone molecules are connected through inversion-related pairs of N—H...S interactions, building a polymeric chain along theb-axis direction. The TCNP molecules are embedded in the structure, forming TTSC–TCNP–TTSC stacks with the aromatic rings of TTSC and the molecular plane of TCNP in a parallel arrangement [centroid–centroid distance = 3.5558 (14) Å]. Charge-transfer (CT)viaπ-stacking is indicated by a CT band around 550 cm−1in the single-crystal absorption spectrum.