A novel 2-(aminomethyl)pyridineH2PO4 crystal with second-order nonlinear optical performance

Abstract

Organic phosphate nonlinear optical (NLO) materials, especially with the introduction of π-conjugated organic cations, have attracted attention due to their excellent performance and promising applications. Here, by combining the π-conjugated organic cationic 2-(aminomethyl)pyridine ((C₆H₉N₂)⁺) with the inorganic moiety H₂PO₄⁻, a novel (C₆H₉N₂)H₂PO₄ ((2-Ampy)H₂PO₄) crystal with a non-centrosymmetric structure has been grown by the slow evaporation method under the conditions of RT and ambient atmosphere. The data about the crystal structure, optical, thermal, photoluminescence and nonlinear optical properties were sufficiently studied. (2-Ampy)H₂PO₄ exhibits a high diffuse reflection with wide transparent range and appropriate thermal stability. Furthermore, an obvious photoluminescence characteristic was presented and displayed two emission peaks with positions at about 385 and 489 nm, while the average PL lifetime was 5.36 μs under the excitation of 300 nm. Importantly, SHG about 0.3× that of KDP is attributed to the hydrogen bond and π-conjugated cationic effects for (2-Ampy)H₂PO₄ crystal powder. By DFT calculations, the simulated band gap is about 3.84 eV, and the electronic states around the forbidden gap are largely determined by the combined effects of the (2-Ampy)⁺ and (H₂PO₄)⁻ groups’ contribution to the optical features. All the above characteristics should be beneficial to the design and application of novel organic–inorganic hybrid phosphate NLO materials.