Above Room Temperature Organic Dielectric Switchable and NLO Co‐crystal: [C4H4O4][C8H19N]

Abstract A new pure organic co‐crystal compound 1 , [C4H4O4][C8H19N] ([C4H4O4]=maleic acid, [C8H19N]=diisobutylamine/DIBA) was discovered to undergo an above room temperature reversible phase transition at around 353/343 K. The variable‐temperature single‐crystal X‐ray structural measurements reveal that space group of the structural phase transition is from space group Cmm 2 to space group Imm 2. The phase transition of compound 1 is mainly ascribed to the twisted movement of diisobutylamine molecules. Meanwhile, nonlinear optical (NLO) properties were also observed in compound 1 .