A tetra-dentate ligand L [3,3′-((pyridin-2-ylmethyl)azanediyl)dipropanamide] was synthesized and characterized by spectroscopic and structural methods. The reaction of L with two different copper(II) halides [CuX2; X = Br, Cl] in a similar condition yielded two different compounds of [LCuCl]Cl, 1 and [CuLBr]2[CuBr4]·CH3OH·H2O, 2. Both compounds were characterized by several physicochemical techniques. Single-crystal X-ray studies revealed that the Cu(II) centers in the cationic complexes 1 and 2 are in a square pyramidal N2O2X (X = Cl and Br) environment. Compound 1 is chromotropic and its solvatochromism and halochromism properties were investigated. It was found that the observed positive solvatochromism is due to structural change and solvation of the vacant site of the complex. The complex demonstrated distinct reversible spectral change over the pH range 1.3–12.1 and can act as pH-induced off–on–off absorption switch through deprotonation and the Cu–O to Cu–N bond rearrangement of the coordinated amide groups in aqueous solution.

中文翻译：

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铜 (II) 配合物与 3,3'-((pyridin-2-ylmethyl)azanediyl)dipropanamide 配体的结构和向色性特性

合成了四齿配体 L [3,3'-((pyridin-2-ylmethyl)azanediyl)dipropanamide]，并通过光谱和结构方法对其进行了表征。L 与两种不同的卤化铜 (II) [CuX2; X = Br, Cl] 在类似条件下产生两种不同的化合物 [LCuCl]Cl, 1 和 [CuLBr]2[CuBr4]·CH3OH·H2O, 2。这两种化合物都通过几种物理化学技术进行了表征。单晶 X 射线研究表明，阳离子配合物 1 和 2 中的 Cu(II) 中心位于方形金字塔形 N2O2X（X = Cl 和 Br）环境中。化合物1是变色的，对其溶剂化变色和卤化变色特性进行了研究。发现观察到的正溶剂化显色是由于复合物空位的结构变化和溶剂化。