Structure and solvatochromism of heteroaromatic aminoketones containing thiophene moieties

A series of N‐substituted phenyl‐2‐thienyl ketones including 2‐(4‐fluorobenzoyl)thiophene (FLBT, 1a), 2‐(4‐piperidinobenzoyl)thiophene (PIBT, 1b), 2‐(4‐morpholinobenzoyl)thiophene (MOBT, 1c), 2‐(4‐thiomorpholinobenzoyl)thiophene (THBT, 1d), 2‐(4‐phenylpiperazinobenzoyl)thiophene (PHBT, 1e), 2‐(4‐pyrrolidinobenzoyl)‐thiophene (PYBT, 1f), 2‐(4‐hydroxyethylpiperazinobenzoyl)thiophene (HYBT, 1g), 1,4‐bis(4‐benzoyl‐2‐thienyl)piperazine (BBTP, 2) and 1,6‐bis(4‐benzoyl‐2‐thienyl)‐N,N′‐dimethylhexamethylenediamine (BBDA, 3) have been investigated regarding solvatochromism and solid‐state structure. Solvatochromic properties have been analyzed using the Kamlet–Taft linear solvation energy relationship. The influence of the dipolarity/polarizability (π*) and hydrogen‐bond acidity (α) of the solvent, respectively, on the portions of the bathochromic UV–Vis band shift as a function of substituent is discussed. The solid‐state structures of 1b (C16H17NOS), 1c (C15H15NO2S) and 1f (C15H15NOS) have been determined by single‐crystal x‐ray structure analysis. Crystallochromic effects are discussed comparatively with regard to the linear solvation energy relationships and the results of the solid‐state structures.