The synthesis and characterization of a flexidentate pyridine-substituted formazanate ligand and its boron difluoride adducts, formed via two different coordination modes of the title ligand, are described. The first adduct adopted a structure that was typical of other boron difluoride adducts of triarylformazanate ligands and contained a free pyridine subsituent, while the second was formed via the chelation of nitrogen atoms from the formazanate backbone and the pyridine substituent. Stepwise protonation of the pydridine-functionalized adduct, which is essentially nonemissive, resulted in a significant increase in the fluorescence quantum yield up to a maximum of 18%, prompting the study of this adduct as a pH sensor. The coordination chemistry of each adduct was explored through reactions with nickel(II) bromide [NiBr₂(CH₃CN)₂], triflate [Ni(OTf)₂], and 1,1,1,4,4,4-hexafluoroacetylacetonate [Ni(hfac)₂(H₂O)₂] salts. Coordination to nickel(II) ions altered the physical properties of the boron difluoride formazanate adducts, including red-shifted absorption maxima and less negative reduction potentials. Together, these studies have demonstrated that the physical and electronic properties of boron difluoride adducts of formazanate ligands can be readily modulated through protonation and coordination chemistry.

中文翻译：

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柔性吡啶取代的甲酸酯配体的二氟化硼加合物：通过质子化和配位化学的性质调节。

描述了通过标题配体的两种不同配位方式形成的柔性吡啶取代的甲酸酯配体及其二氟化硼加合物的合成和表征。第一个加合物采用的是三芳基甲氮酸酯配体的其他二氟化硼加合物的典型结构，并包含一个游离的吡啶取代基，而第二个则是通过甲from骨架和吡啶取代基上氮原子的螯合形成的。吡啶官能化的加合物的逐步质子化（本质上是非必需的）导致荧光量子产率显着提高，最高可达18％，这促使人们对该加合物作为pH传感器进行了研究。通过与溴化镍（II）[NiBr ₂（CH ₃ CN）₂ ]，三氟甲磺酸盐[Ni（OTf）₂ ]和1,1,1,1,4,4,4-六氟乙酰丙酮酸盐[Ni（hfac）₂（H ₂ O）₂ ]盐。与镍离子的配位改变了二氟化硼甲酸酯加合物的物理性质，包括最大的红移吸收和较小的负还原电位。总之，这些研究表明，甲酸酯配体的二氟化硼加合物的物理和电子性质可以通过质子化和配位化学容易地调节。