Dual-Switchable Dielectric and Photoluminescence Response in Organic-Inorganic Manganese Halide Hybrids

Multifunctional response materials exhibit potential applications in sensors and optoelectronic devices; however, successfully targeting such materials remains a significant challenge. In this study, we synthesized two zero-dimensional hybrids: (C₆H₁₆N)₂MnBr_1.53Cl_2.47 (1, C₆H₁₆N = trimethyl propyl ammonium) and (C₇H₁₈N)₂MnBr_1.40Cl_2.60 (2, C₇H₁₈N = trimethyl butyl ammonium). These compounds were formed by combining pseudoglobular organic ammonium cations with the highly emissive [MnX₄]^2- (X = Br or Cl) anion. Both compounds undergo order-disorder structural phase transitions, exhibiting thermal hysteresis: 1 at 331 K (heating)/326 K (cooling) and 2 at 383 K/373 K and 445 K/428 K (heating/cooling), respectively. These transitions result in a switchable dielectric behavior. At ambient conditions, both compounds emit the bright characteristic luminescence of the [MnX₄]^2- anion, with photoluminescence quantum yields (PLQY) of 88.71% for 1 and 94.59% for 2. However, they exhibit thermal quenching at elevated temperatures (∼420 K for 1 and ∼460 K for 2). Near their phase transition temperatures, both compounds also show switchable luminescent properties. Collectively, 1 and 2 represent rare examples of materials exhibiting dual-switchable dielectric and luminescence responses.