The supramolecular assemblies of 7-amino-2,4-dimethylquinolinium salts and the effect of a variety of anions on their luminescent properties

The 7-amino-2,4-dimethylquinolinium salts with a variety of anions (Cl-, HCOO-, CH3COO-, PhCOO-, L-HOOCCH(OH)CH(OH)COO-) have been synthesized and characterized. The crystal structures of these salts were determined by single-crystal X-ray diffraction. The structure analysis confirms that the nitrogen atoms in the quinoline rings are protonated in all salts. The two solvates have been obtained and thereby provide a useful complement to cocrystal screening. All the quinolinium salts display interesting three dimensional supramolecular networks. The hydrogen bonding interactions observed in all of the salts are N-H center dot center dot center dot O, O-H center dot center dot center dot O and N-H. Cl, together with weak C-H center dot center dot center dot O, C-H center dot center dot center dot N, C-H center dot center dot center dot Cl hydrogen bonds. The weak C/N-H center dot center dot center dot pi contacts and pi-pi stacking interactions involving the quinoline moieties also exist in quinolinium salts. The observed noncovalent interactions become prominent in stabilizing their crystal packing. The 7-amino-2,4-dimethylquinolinium salts show strong luminescence in the solid state and solution in the range 422-534 nm. The solid-state emission spectra of the quinolinium salts are sensitive to the anion species, and highly dependent on the nature of the stacking interactions.