Co-crystals of 2-amino-5-nitropyridine barbital with Extreme Birefringence and Large Second Harmonic Generation Effect.

Technological innovation enforces a revolutionized approach towards materials chemistry. In this paper a new methodology towards crystal engineering of polar materials for possible applications in linear or non-linear optics (NLO), as well as ferroelectric, pyroelectric or piezoelectric crystals is presented. The necessity to fulfil several criteria concerning symmetry, electron properties of the building blocks, and also mechanical and optical stability was achieved by fusion of a pharmaceutical molecule and an NLO-phore. Co-crystals of 2-amino-5-nitropyridine barbital, presented in this manuscript, show cutting-edge optical performance. Large second harmonic generation (SHG) efficiency (40 times better than potassium dihydrogen phosphate, KDP), extreme birefringence (2.7 times higher than for calcite), simplicity in preparation, and optical and mechanical stability of the product proves that in fact a new generation of smart materials was obtained.