Skvortsova Sofia V, Verkhov Fyodor K, Nikolaenkova Elena B, Rakhmanova Marianna I, Kokina Tatiana E, Sukhikh Taisiya S, Shekhovtsov Nikita A, Bushuev Mark B
Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, 3, Acad. Lavrentiev Ave., Novosibirsk, 630090, Russia.
Novosibirsk State University, 2, Pirogova str., Novosibirsk, 630090, Russia.
Dalton Trans. 2025 Jun 3;54(22):9000-9015. doi: 10.1039/d5dt00498e.
Two bicyclic pyrazolylpyrimidine compounds, 2-benzylthio-4-(3,5-dimethyl-1-pyrazol-1-yl)pyrimidine (LH) and 2-benzylthio-4-(3,5-dimethyl-1-pyrazol-1-yl)-6-methylpyrimidine (LMe), were synthesized and studied as ligands for the preparation of copper(I) halido complexes. In the solid state, LH and LMe demonstrate dual excitation-wavelength dependent emission, fluorescence at higher excitation energies and phosphorescence at lower excitation energies due to the presence of a heavy sulphur atom. The reactions of LH and LMe with CuBr and CuI afforded a series of centrosymmetric binuclear complexes of the [Cu2L2Hal2] type (L = LH, Hal = Br, I; L = LMe, Hal = I). The possibility of rotation of the benzylthio group relative to the pyrazolylpyrimidine core leads to the isolation of two polymorphic modifications of the copper(I) iodido complex with LH, which differ by the Cu⋯Cu distance by more than 0.2 Å (2.86 Å for [Cu2(LH)2I2] (form I) 2.65 Å for [Cu2(LH)2I2] (form II)). The isolation of the [Cu2(LH)2I2] complex in two different crystalline forms made it possible to reveal the influence of a rarely explored factor, namely the change in the Cu⋯Cu distance in a single molecule, on the photoluminescence quantum efficiency. Two structural indices, , which showcases the degree of merging of CuLHal monomers into the centrosymmetric [Cu2L2Hal2] dimers, and , which characterises the degree of planarization of the NCuHalCuN unit, were introduced and used for combined experimental and theoretical analyses of the relation between the structure of the complexes and their luminescence. All complexes exhibit phosphorescence of the ligand-to-halide charge transfer (LXCT) character in the orange region. According to TD-DFT calculations, an increase in the Cu⋯Cu distance facilitates structural rearrangement in the T state followed by a rapid decrease in the T-S energy gap and subsequent non-radiative decay electron-phonon coupling, which substantiates the higher photoluminescence quantum yield (PLQY) of [Cu2(LH)2I2] (form II) (Cu⋯Cu 2.65 Å) compared to that of [Cu2(LH)2I2] (form I) (Cu⋯Cu 2.86 Å).
合成了两种双环吡唑基嘧啶化合物，即2-苄硫基-4-(3,5-二甲基-1-吡唑-1-基)嘧啶（LH）和2-苄硫基-4-(3,5-二甲基-1-吡唑-1-基)-6-甲基嘧啶（LMe），并将其作为配体用于制备卤化亚铜配合物进行研究。在固态下，由于存在重硫原子，LH和LMe表现出双激发波长依赖发射，在较高激发能量下发出荧光，在较低激发能量下发出磷光。LH和LMe与CuBr和CuI反应得到了一系列[Cu2L2Hal2]型的中心对称双核配合物（L = LH，Hal = Br，I；L = LMe，Hal = I）。苄硫基相对于吡唑基嘧啶核心的旋转可能性导致分离出与LH形成的碘化亚铜配合物的两种多晶型变体，它们的Cu⋯Cu距离相差超过0.2 Å（[Cu2(LH)2I2]（晶型I）为2.86 Å，[Cu2(LH)2I2]（晶型II）为2.65 Å）。以两种不同晶体形式分离出[Cu2(LH)2I2]配合物，使得揭示一个很少被探索的因素的影响成为可能，即单个分子中Cu⋯Cu距离的变化对光致发光量子效率的影响。引入了两个结构指标，展示了CuLHal单体合并成中心对称[Cu2L2Hal2]二聚体的程度，以及表征NCuHalCuN单元平面化程度的指标，并用于对配合物结构与其发光之间关系的联合实验和理论分析。所有配合物在橙色区域均表现出配体到卤化物电荷转移（LXCT）特征的磷光。根据TD-DFT计算，Cu⋯Cu距离的增加有利于T态的结构重排，随后T-S能隙迅速减小并发生非辐射衰变——电子-声子耦合，这证实了[Cu2(LH)2I2]（晶型II）（Cu⋯Cu 2.65 Å）比[Cu2(LH)2I2]（晶型I）（Cu⋯Cu 2.86 Å）具有更高的光致发光量子产率（PLQY）。
