Abstract The ligand, 4-chloro-2,6-dipicolinic acid (H2PDA-Cl), and its two heavy metal complexes, [Ag(HDPA-Cl)(H2DPA-Cl)·2H2O] (1) and {[Cd(μ2-H2O)(H2O)(PDA-Cl)]}n (2), were prepared and then characterized by single-crystal X-ray diffraction. In addition, spectral and thermal correlations with structural results complete their solid-state description and facilitate complex 3 ([Pb(DPA-Cl)]) composition determinations. Complex 1 crystallizes in a monoclinic space group C2/c and each DPA-Cl ligand is tridentate to Ag(I) through the pyridine N and two monodentate carboxyl O atoms. The carboxy group with carbonyl C1 is semideprotonated and forms a symmetric hydrogen bond with a carboxy group of a neighboring complex. Complex 2 crystallizes in a triclinic lattice with space group P The Cd(II) ions are seven-coordinate and the coordination polyhedra can be described as a distorted pentagonal bipyramid. IR data are consistent with monodentate coordination of the carboxylate to Ag(I), Cd(II), and Pb(II) and observed wavenumber shifts confirm PDA-Cl ligand coordination to Pb(II) in 3. Thermal stability of anhydrous complexes indicates the metal–ligand interactions. The thermal stability of prepared compounds is reflected by the strength of interaction between metal–ligand and hydrogen bonds.

中文翻译：

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4-氯吡啶二羧酸的重金属配合物 - 结构、光谱和热相关性

摘要 配体 4-氯-2,6-吡啶二羧酸 (H2PDA-Cl) 及其两种重金属配合物 [Ag(HDPA-Cl)(H2DPA-Cl)·2H2O] (1) 和 {[Cd( μ2-H2O)(H2O)(PDA-Cl)]}n (2)，然后通过单晶 X 射线衍射表征。此外，光谱和热与结构结果的相关性完善了它们的固态描述，并促进了复合物 3 ([Pb(DPA-Cl)]) 成分的确定。配合物 1 在单斜空间群 C2/c 中结晶，每个 DPA-Cl 配体通过吡啶 N 和两个单齿羧基 O 原子与 Ag(I) 三齿。带有羰基 C1 的羧基被半去质子化，并与相邻配合物的羧基形成对称氢键。配合物 2 在空间群 P 的三斜晶格中结晶。Cd(II) 离子是七配位的，配位多面体可以描述为扭曲的五边形双锥。IR 数据与羧酸盐与 Ag(I)、Cd(II) 和 Pb(II) 的单齿配位一致，观察到的波数位移证实 3 中 PDA-Cl 配体与 Pb(II) 的配位。无水配合物的热稳定性表明金属-配体相互作用。制备的化合物的热稳定性通过金属-配体和氢键之间的相互作用强度来反映。无水配合物的热稳定性表明金属-配体相互作用。制备的化合物的热稳定性通过金属-配体和氢键之间相互作用的强度来反映。无水配合物的热稳定性表明金属-配体相互作用。制备的化合物的热稳定性通过金属-配体和氢键之间的相互作用强度来反映。