Intermolecular forces and functional group effects in the packing structure of thiophene derivatives

Thiophene was derivatized at the beta-carbon with isophthalic, dipicolinic, and four nitrobenzoic acids to yield 4-thiophen-3-yl-pyridine-2,6-dicarboxylic acid diethyl ester, I; 5-thiophen-3-yl-isophthalic acid diethyl ester, II; 2-nitro-4-thiophen-3-yl benzoic acid ethyl ester, III; 3-nitro-4-thiophen-3-yl benzoic acid ethyl ester, IV; 3-nitro-2-thiophen-3-yl benzoic acid ethyl ester, V; and 2-nitro-5-thiophen-3-yl benzoic acid ethyl ester, VI. These resulting compounds have been isolated and characterized by X-ray single-crystal diffraction. The solid-state structures of these substances are discussed as a function of the position and nature of the functional groups and the intermolecular forces. Modeling of the thiophene-aromatic ring torsion angle allowed us to attribute large differences in torsion angles to packing effects in the structures, due to pi-pi interactions between the aromatic rings.