Lim Ae Ran, Yeom Tae Ho
Graduate School of Carbon Convergence Engineering, Jeonju University, Jeonju 55069, South Korea.
Department of Science Education, Jeonju University, Jeonju 55069, South Korea.
ACS Omega. 2024 Jul 29;9(32):34918-34926. doi: 10.1021/acsomega.4c04606. eCollection 2024 Aug 13.
The crystal structure of NH(CH)CuCl, an organic-inorganic hybrid perovskite, undergoes a phase transition from triclinic to monoclinic at the phase transition temperature of 287 K. We investigated the temperature dependencies of NMR chemical shifts and spin-lattice relaxation time to gain insights into the structural geometry and molecular dynamics during the transition from phase II to phase I at high temperatures. Analysis of the H and C NMR chemical shifts of the cation revealed a continuous change in the surrounding structural geometry with temperature, without any anomalous changes around . The sudden decrease in values from low to high temperatures indicated a significant variation in proton and carbon dynamics at , arising from the slowing motion of molecular dynamics across the phase transition. The activation energies obtained from the temperature dependence of for H and C were larger in phase I than in phase II. This suggests that molecular motions in phase II exhibit a higher degree of freedom compared to those in phase I, where they are more constrained. These findings on NH(CH)CuCl are presented to enhance its potential applications by elucidating the crystal configuration and structural molecular dynamics of ABX type compound.
有机-无机杂化钙钛矿NH(CH)CuCl的晶体结构在287 K的相变温度下经历从三斜晶系到单斜晶系的相变。我们研究了核磁共振（NMR）化学位移和自旋晶格弛豫时间与温度的依赖关系，以深入了解高温下从II相到I相转变过程中的结构几何形状和分子动力学。对阳离子的氢和碳核磁共振化学位移分析表明，周围结构几何形状随温度持续变化，在相变温度附近没有任何异常变化。从低温到高温，自旋晶格弛豫时间值的突然下降表明，在相变温度处质子和碳动力学有显著变化，这是由于分子动力学在相变过程中运动减慢所致。从氢和碳的自旋晶格弛豫时间对温度的依赖关系获得的活化能在I相中比在II相中更大。这表明与I相相比，II相中的分子运动表现出更高的自由度，在I相中分子运动受到更多限制。展示这些关于NH(CH)CuCl的研究结果，是为了通过阐明ABX型化合物的晶体构型和结构分子动力学来增强其潜在应用。
