The effect of β-cyclodextrin (β-CD) on the spectroscopic properties of mebendazole, MBZ, in aqueous solution was investigated at pH values of 2.0, 4.0, 6.0, 8.0, 10.0, and 12.0, where mebendazole exists as protonated (HMBZ⁺), neutral (MBZ), or deprotonated (MBZ⁻) forms. Mebendazole shows two absorption bands at 236 nm and 288 nm at pH 2.0, which are shifted gradually as pH increases to 265 nm and 350 nm at pH 12.0, and one fluorescence emission band at 463 nm at all pH values. In the presence of β-CD, the emission band at 463 nm was enhanced and new emission bands in the range 300–350 nm were observed at pH 2.0–6.0. In addition, pK_a1 of MBZ increased and pK_a2 decreased, indicating that both benzimidazole and carbamate moieties are involved in complex formation, which is confirmed by the results of molecular dynamics (MD) simulations. Benesi–Hildebrand analysis and MD simulations show that binding stoichiometry of neutral MBZ/β-CD complex is 1:2, where the wide rims of both CD macrocycles face each other, while a stoichiometry of 1:1 was observed for the protonated HMBZ⁺/β-CD complex. Experimentally obtained thermodynamic parameters show that complexation of MBZ with β-CD is a spontaneous enthalpy driven process (ΔG° = −36.3 kJ mol⁻¹ for MBZ/β-CD and ΔG° = −25.9 kJ mol⁻¹ for HMBZ⁺/β-CD), while binding free energy computed through MM-PBSA computational method shows that driving forces for complex formation is van der Waals interactions and H-bonding.

在pH值为2.0、4.0、6.0、8.0、10.0和12.0的条件下，研究了β-环糊精（β-CD）对甲苯咪唑MBZ在水溶液中的光谱性质的影响，其中苯甲达唑以质子化形式存在（HMBZ ⁺），中性（MBZ），或去质子化（MBZ ^- ）形式。甲苯苯达唑在pH 2.0时在236 nm和288 nm处显示两个吸收带，在pH 12.0时随着pH值增加到265 nm和350 nm而逐渐移动，在所有pH值下在463 nm处显示一个荧光发射带。在存在β-CD的情况下，在pH 2.0-6.0时，463 nm处的发射带得到增强，并且在300-350 nm范围内观察到了新的发射带。此外，MBZ的p K _a1增加，p K _a2分子动力学（MD）模拟结果证实，苯甲并咪唑和氨基甲酸酯部分都参与了复合物的形成。Benesi–Hildebrand分析和MD模拟显示，中性MBZ /β-CD复合物的结合化学计量比为1：2，两个CD大环的宽边彼此面对，而质子化HMBZ ⁺的化学计量比为1：1。/β-CD复合物。实验获得的热力学参数显示MBZ与β-CD该络合是一个自发焓驱动的过程（Δ ģ °= -36.3千焦摩尔^-1为MBZ /β-CD和Δ ģ °= -25.9千焦摩尔^-1为HMBZ ⁺/β-CD），而通过MM-PBSA计算方法计算出的结合自由能表明，复合物形成的驱动力是范德华相互作用和氢键。