Switchable Nonlinear Optical and Tunable Luminescent Properties Triggered by Multiple Phase Transitions in a...

A new perovskite-like inorganic-organic hybrid compound [Et₃(n-Pr)P][Cd(dca)₃] (1) (where [Et₃(n-Pr)P]⁺ is the propyltriethylphosphonium cation and dca is a dicyanamide ligand) was discovered to undergo three reversible phase transitions at 270 K (T₁), 386 K (T₂), and 415 K (T₃), respectively. The variable-temperature single-crystal X-ray structural analyses reveal that these sequential phase transitions originate from the deformations of the [Cd(dca)₃]^- frameworks and the concomitant reorientations of the [Et₃(n-Pr)P]⁺ guest cations. It is found that 1 possesses a sensitive nonlinear optical (NLO) switching at T₂ with a large contrast of ∼40 within a narrow temperature range of ∼7 K. Furthermore, 1 shows intriguing photoluminescence (PL) property, and the PL intensity suffers a plunge near T₃. The multiple phase transitions, switchable NLO and tunable luminescent properties simultaneously exist in this inorganic-organic perovskite-like hybrid compound, suggesting its great potential application in molecular switches and photoelectric field.