Experimental and Theoretical Study of the Structure of 3-Arylidene-1-Pyrrolinium Salts

Molecular, crystal, and electronic structures of a series of 3-arylidene-1-pyrrolinium salts are studied. Trifluoroacetates and nitrates of a number of arylidene pyrrolines containing various substituents in the para-position of the arylidene fragment are analyzed. It is shown that the organic cations have a virtually planar molecular structure that is quite easily distorted due to the mobility of the C–C single bond. Varying the substituent in the arylidene pyrroline structure affects insignificantly the geometric and electronic characteristics of the studied compounds. The nature of the anion has almost no effect on the molecular and electronic structure. In all cases, the crystal packing of the studied compounds is mainly due to the hydrogen bonds and non-covalent interactions involving the π-system and the presence of halogen atoms.