Crystal structure of the chalcogen-containing precursors for polymethine dyes

Abstract

Polymethine dyes are potential materials for all-optical signal processing.1 However, in order for these materials to retain their favorable solution properties in the high-number density films, their molecular aggregation should be reduced. To limit aggregation, bulky groups may be introduced in several positions of the dye to protect the π-conjugated system from interacting with itself. 2,3Currently, we are presenting the investigation of thio-, seleno-and telluro-pyranones and chalcogenopyrylium salts with bulky tert-butyl groups, which were prepared as described previously. 4 The general scheme of studied compounds is presented below, where Z is S, Se, or Te.The crystal structures of thio-and seleno-pyranones I atoms are isostructural and crystallize in P21/c space group. There no any special intermolecular contacts in these crystals. However, introduction of larger Te atom in telluro-pyranone changes the crystal structure, and it contains hydrogen-bonded dimers with H…O distance 2.58 Å.The crystal structures of seleno-and telluropyrylium salts II are isomorphous and crystallize in C2/c space group. Both structures contain three symmetrically independent cations and three PF6 -anions. In crystal, the molecules form hexamers containing two of each symmetrically independent molecules connected by six PF6 -anions. The hexamers are packed in columns along [0 0 1] direction. Our research provides an insight into the crystal structure and intermolecular interactions that may occur in polymethine dyes.