5,11,17,23-四亚甲基对氨基苯羧酸间苯二酚杯[4]芳烃亚胺衍生物与锌(II)、镉(II)离子配位的DFT计算模型分析

DFT Calculation and Model Analysis of the Coordination between Zinc (II)/Cadmium (II) Ions and a 5,11,17,23-Tetramethylene-p-Aminobenzoic Acid[4] Resorcinarene Imine Derivative

摘要: 本文比较两种羧酸功能化间苯二酚杯[4]芳烃衍生物——2,8,14,20-四丙基-5,11,17,23-四亚甲基N-苯乙酸间苯二酚杯[4]芳烃(化合物1)与2,8,14,20-四丙基-5,11,17,23-四亚甲基N-苯丁酸间苯二酚杯[4]芳烃(化合物2)，并综合运用密度泛函理论(DFT)计算与紫外–可见吸收光谱，系统研究了其与重金属离子Zn²⁺和Cd²⁺的配位行为。理论计算表明，两种化合物均能以四配位模式与金属离子形成稳定的1:1配合物，导致杯芳烃上缘空腔由开放结构转变为封闭结构。键长与电荷布居分析揭示了支链长度与金属离子种类对配位键的影响，其中Cd²⁺因离子半径更大，其配位键(O-Cd)长于Zn²⁺的配位键(O-Zn)。热力学计算证实配合物的形成是自发过程(ΔG < 0)。实验光谱中特征吸收峰的蓝移(347 nm → 339 nm)及495 nm处旧峰的消失与433 nm处新峰的出现，为配位作用提供了确凿的实验证据。本研究为开发新型杯芳烃基重金属离子受体提供了坚实的理论与实验依据。

Abstract: The coordination behavior of two carboxyl-functionalized resorcin[4]arene derivatives with heavy metal ions (Zn²⁺ and Cd²⁺) was systematically investigated and compared using density functional theory (DFT) calculations and UV-Vis absorption spectroscopy. The ligands studied are 2,8,14,20-tetrapropyl-5,11,17,23-tetramethylene N-phenylaceticacidresorcin[4]arene (Compound 1) and its homologue, 2,8,14,20-tetrapropyl-5,11,17,23-tetramethylene N-phenylbutyric acid resorcin[4]arene (Compound 2). Theoretical calculations revealed that both compounds form stable 1:1 complexes with the metal ions via a tetra-coordination mode, inducing a structural transition of the resorcin[4]arene upper rim from an open to a closed conformation. Analysis of bond lengths and atomic charges elucidated the influence of the carboxylate side chain length and the metal ion identity on the coordination bonds, noting that the larger ionic radius of Cd²⁺ resulted in longer O-Cd bonds compared to O-Zn bonds. Thermodynamic calculations confirmed the spontaneity of the complexation processes (ΔG < 0). Experimental spectroscopic changes, including a blue shift of the characteristic absorption band (from 347 nm to 339 nm), the disappearance of the peak at 495 nm, and the emergence of a new band at 433 nm, provided conclusive evidence for coordination. This research provides a solid theoretical and experimental foundation for developing novel resorcin[4]arene-based receptors for heavy metal ions.