C4H4O4]⋅[C6H13N] as a nonlinear optical co-crystal with spike-like dielectric anomalies

Abstract

Nonlinear optical (NLO) effects have important applications in optoelectronic technology, such as frequency conversion and information processing. Here, we report a NLO co-crystal [C4H4O4]∙[C6H13N] 1, where [C4H4O4] is fumaric acid and [C6H13N] is cyclohexylamine/CHA. Second harmonic generation (SHG) intensity of compound 1 is 1.25 × KH2PO4. The variable-temperature single-crystal X-ray structural measurements reveal that compound 1 crystallizes in triclinic P1 space group accompanied with a homogeneous phase change. The structural phase change of compound 1 is mainly attributed to order-disorder transition resulted from the thermal movements of cyclohexylamine cations. Spike-like dielectric anomalies can be observed at different frequencies.