Rational Design of Noncentrosymmetric Organic-Inorganic Hybrids with a π-Conjugated Pyridium-Type Cation for High Nonlinear-Optical Performance

Organic-inorganic hybrid materials have attracted increasing attention due to their unique superiority by combining the features of organic parts with inorganic parts. Herein, two organic-inorganic hybrid nonlinear-optical crystals, [C5H6O2N3](2)[IO3](2) (I) and [C5H6O2N3][HSO4]center dot H2O (II), were successfully synthesized in aqueous solution by selecting 2-amino-3-nitropyridine as the cation and different anions of [IO3](-) and [HSO4](-). The two compounds crystallized in the noncentrosymmetric space groups of P2(1) and P2(1)2(1)2(1), respectively. I displays second-harmonic-generation (SHG) effects of 2.4 x KDP (KH2PO4) and a large birefringence (Delta n(cal) similar to 0.22). Moreover, II exhibits a stronger SHG response of 5.2 x KDP, an enhanced band gap (2.81 eV), as well as a large birefringence (Delta n(cal) similar to 0.25). This work points out a new feasible path for the rational design of high-performance organic-inorganic hybrid materials.