A new series of conjugated donor−π–acceptor type of 2,6-bis(pyrazolyl)pyridine derivatives (compounds IK-(3–9)) have been synthesized via Horner–Wadsworth–Emmons (HWE) reaction, starting from a common phosphonate precursor and diverse donor aromatic aldehydes and characterized by routine spectral analysis including elemental analysis. Compound IK-2, one of the starting precursors, and molecule IK-3, the first member of the donor−π–acceptor series, are additionally characterized by single-crystal X-ray structure determination. Compounds IK-2 and IK-3 are crystallized in P1̅ (triclinic) and P2₁/c (monoclinic) space groups, respectively. The absorption maxima in the electronic spectra of the title compounds shift mainly due to intramolecular charge transfer (ICT) between different donor (dibutyl and cyclic pyrrolidine) groups and the acceptor moiety [2,6-bis(pyrazolyl) pyridine]. Solution-state emission spectral studies of all these compounds show large solvent sensitive behavior with significant amounts of Stokes shifts. The large solvent dependence of the emission indicates that the excited state is stabilized in more polar solvents due to the ICT. All chromophores exhibit solid-state fluorescence behavior except compound IK-7. The role of the position and nature of the donor functionalities in the conjugated backbone of overall donor moiety of compounds IK-(3–9), on the electronic absorption properties of the title chromophores has been demonstrated, which has further been corroborated by density functional theory (DFT) and time-dependent DFT (TDDFT) computational studies. The emission spectral results of compounds IK-3, IK-5, and IK-7 have also been supported by the DFT and TDDFT calculations. A fluorescence lifetime study on this series also shows that the excited states are stabilized in more polar solvents. Finally, one of the chromophores (chromophore IK-4) in the title series has been shown to act as a selective molecular sensor (turn-off switch) for the Cu(II) ion.

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双（吡唑基）吡啶衍生物的功能分子系统：光物理，光谱学，计算和离子传感

从霍尼韦德-沃兹沃斯-埃蒙斯（HWE）反应合成了一系列新的共轭供体-π-受体类型的2,6-双（吡唑基）吡啶衍生物（化合物IK-（3-9））。膦酸酯前体和各种供体芳族醛，并通过常规光谱分析（包括元素分析）进行表征。化合物IK-2是起始前体之一，而分子IK-3是供体-π-受体系列的第一个成员，还通过单晶X射线结构测定来表征。化合物IK-2和IK-3在结晶化P 1（三斜晶）和P 2 ₁ / ç（单斜）空间组。标题化合物在电子光谱中的吸收最大值发生偏移，主要是由于不同供体（二丁基和环状吡咯烷）基团与受体部分[2,6-双（吡唑基）吡啶]之间的分子内电荷转移（ICT）。所有这些化合物的溶液状态发射光谱研究表明，溶剂的行为很敏感，斯托克斯位移很大。发射对溶剂的依赖性很大，这表明由于ICT，激发态在极性更大的溶剂中稳定了。除化合物IK-7外，所有生色团均表现出固态荧光行为。供体官能团的位置和性质在化合物IK-（3-9）的整体供体部分的共轭主链中的作用，已经证明了标题生色团的电子吸收性能，其进一步得到密度泛函理论（DFT）和时变DFT（TDDFT）计算研究的证实。DFT和TDDFT计算也支持了化合物IK-3，IK-5和IK-7的发射光谱结果。关于该系列的荧光寿命研究还表明，在更多极性溶剂中，激发态是稳定的。最后，标题系列中的一个生色团（生色团IK-4）已显示出可作为Cu（II）离子的选择性分子传感器（关断开关）。