(3-C6H10N2)ZnX4 (X = Cl and Br): Two Excellent UV Nonlinear Optical Crystals Designed by Combination of π-conjugated and [ZnX4]2- Tetrahedral Units

To design excellent UV nonlinear optical crystals, via a combination of the two excellent genes, planar pi-conjugated 3-(aminomethyl)pyridinium ((3-AMP)(2+), (C6H10N2)(2+)) and d(10) metallic tetrahedral anion, two novel organic-inorganic hybrid (3-C6H10N2)ZnX4 (X = Cl and Br) bulk crystals are synthesized using a simple solution method. Remarkably, they exhibit excellent UV nonlinear optical performances, including in short UV absorption edge (229 and 235 nm), robust second harmonic generation (SHG) intensity (2.05 and 4.36 x KDP), suitable large birefringence (0.129-0.144@546 nm) and short phase-matching wavelength (238 and 262 nm). First-principles calculations elucidate that the excellent SHG performances of (3-AMP)ZnCl4 and (3-AMP)ZnBr4 are dominated by the synergetic contributions of planar pi-conjugated (C6H10N2)(2+) and distorted [ZnX4](2-) tetrahedral groups. This research not only provides two NLO-active genes but also paves the way for efficient exploration and rational design of organic-inorganic hybrid new NLO materials with optimal balanced optical performances.