Possible Application of the Organic Barbiturates as NLO Materials

The self-assembly, crystal structures, and optical properties are reported for eight novel organic crystals of derivatives of barbituric acid, i.e. 4-methoxypyrydinium barbiturate dihydrate (1), 1,10-phenanthrolinium barbiturate monohydrate (2), 1-amino isoquinolinium barbiturate monohydrate (3), 5-hydrohy-L-tryptophan barbituric acid complex (4), 5-hydroxy-L-tryptophan 1,3-dimethylbarbituric acid dihydrate molecule complex (5), 1,10-phenanthrolinium (thio)barbiturate (6), 1-amino-1,2,4-triazole violuric acid monohydrate (7), and pyridine-3-aldoxime violuric acid complex (8). Compounds 1-8 were synthesized and characterized by means of single crystal X-ray diffraction, solution and solid-state UV/vis/NIR spectroscopy, and linear-polarized infrared (IR-LD) spectroscopy. Quantum chemical ab initio and DFT calculations were performed with a view to understanding the optical properties of these species. The potential application of these derivatives as NLO-phores is discussed by comparison with the corresponding violurate salts.