Changes in luminescence due to solution-mediated phase transition (SMPT) and crystal-to-crystal phase transitions of a novel cyclometalated platinum(II) complex with isoquinoline-1-carboxylate (Iq-1-COO^–) [Pt(bzq)(Iq-1-COO)] (bzq^–: benzoquinolinate) were studied experimentally and theoretically. Recrystallization of the complex allowed three crystal forms depending on the solvent: red polymorph R_DMF (λ_emi = 689 nm), yellow polymorph Y_DMSO (λ_emi = 641 nm), and red pseudopolymorph RB_CHCl3 (λ_emi = 721 nm). Crystals of R_DMF in the DMF solution at room temperature showed SMPT to yellow crystals Y_DMF (λ_emi = 627 nm), in which R_DMF first dissolved partly into the solution, and then the dissolved complex crystallized as Y_DMF. RB_CHCl3 exhibited crystal-to-crystal phase transitions to R_DMF and Y_DMF by being heated to 150 °C and stored in atmospheric conditions, respectively. Molecular structures of each of the four crystal forms, analyzed by X-ray crystallography, showed different planarities because of the dihedral angles between the bzq^– and Iq planes being 3.15, 4.80, 8.35, and 17.7° for RB_CHCl3, R_DMF, Y_DMSO, and Y_DMF, respectively. The planar complexes in R_DMF and RB_CHCl3 constructed dimers through intermolecular Pt–Pt and π–π interactions, whereas the distorted complexes in Y_DMF and Y_DMSO remained as monomers. Density functional theory (DFT) calculations, which reveal the relation between the molecular structure and thermodynamic stability, suggest that the SMPT is triggered by thermodynamic transformation from the metastable planar structure to the stable distorted structure. The intradimer interactions in R_DMF and RB_CHCl3 induced red-shifts in the absorption and emission colors from those of Y_DMF and Y_DMSO; thus, the photophysical properties of RB_CHCl3 and R_DMF originate from the MML_IqCT state in contrast with the ML_IqCT/L_bzqL_IqCT character for Y_DMF and Y_DMSO. DFT and time-dependent DFT (TD-DFT) calculations in the ground and excited states provide insight into the structural, electronic, and optical properties.

中文翻译：

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溶液介导的环金属化铂（II）配合物与异喹啉羧酸盐的相变诱导的发光变化

由于溶液介导的相变（SMPT）和具有异喹啉-1-羧酸盐（Iq-1-COO ^–）[Pt（bzq）（ Iq-1-COO）]（bzq ^–：苯并喹啉酸酯）进行了实验和理论研究。复合物的重结晶根据溶剂允许三种晶型：红色多晶型物R _DMF（_λemi = 689 nm），黄色多晶型物Y _DMSO（_λemi = 641 nm）和红色假多晶型RB _{CHCl 3}（_λemi = 721 nm）。 。室温下，DMF溶液中R _DMF的晶体显示SMPT为黄色晶体Y_DMF（_λemi = 627 nm），其中R _DMF首先部分溶解在溶液中，然后溶解的配合物结晶为Y _DMF。RB _{CHCl 3}通过加热到150°C并在大气条件下储存，分别呈现出晶体-晶体向R _DMF和Y _DMF的相变。每个的四个晶体形式，通过X射线晶体学分析的分子结构，表明因为BZQ之间的二面角的不同平面性^-和Iq面为3.15，4.80，8.35，以及17.7°，RB_{三氯甲烷3}，R _DMF， Y _DMSO和Y _DMF， 分别。R _DMF和RB _{CHCl 3中}的平面络合物通过分子间Pt–Pt和π–π相互作用构建二聚体，而Y _DMF和Y _DMSO中扭曲的络合物仍作为单体保留。密度泛函理论（DFT）计算揭示了分子结构与热力学稳定性之间的关系，表明SMPT是由从亚稳态平面结构到稳定畸变结构的热力学转变触发的。R _DMF和RB _{CHCl 3中}的二聚体相互作用引起吸收和发射颜色的红移，与Y _DMF和Y _DMSO的吸收和发射颜色发生红移; 因此，与Y _DMF和Y _DMSO的ML _Iq CT / L _bzq L _Iq CT特性相反，RB _{CHCl 3}和R _DMF的光物理性质源自MML _Iq CT状态。在基态和激发态中的DFT和与时间有关的DFT（TD-DFT）计算提供了对结构，电子和光学特性的洞察力。