Joseph Suman, Somkuwar Pranati, Menon Gayathri G, Rajesh Anjana C, Selvam Pravinkumar, Ramasamy Selva Kumar, Bhaskar R, Kumar S K Ashok
Department of Chemistry, School of Advanced Sciences, Vellore Institute of Technology, Vellore - 632 014, Tamil Nadu, India.
Department of Chemistry, M. M. Engineering College, Maharishi Markandeshwar (Deemed to be University), Mullana, Ambala-33207, Haryana, India.
Anal Methods. 2025 Jan 2;17(2):265-274. doi: 10.1039/d4ay01574f.
In this study, we present three different approaches for the colorimetric detection of Ni ions using a specifically designed benzothiazole-quinoline dyad (L) synthesized the Knoevenagel condensation reaction in high yield. The unique properties of L enable a rapid and selective response to Ni ions, making it an ideal probe for practical applications. The probe L shows a pale yellow color under normal conditions. Upon interaction with Ni ions, L undergoes a significant color change from pale yellow to bright orange, allowing for visual detection in semi-aqueous media. This rapid colorimetric response enables real-time monitoring of Ni concentrations. The absorption maximum of L undergoes a bathochromic shift in the presence of Ni ions due to ligand-to-metal charge transfer (LMCT). The probe L could form a 2 : 1 [L : Ni] stoichiometric complex, confirmed through Job's plot and ESI mass analysis with an estimated association constant of 2.61 × 10 M. The probe L could detect Ni concentration down to 61 nM, 106 nM, and 129 nM a UV-Vis spectrophotometer, smartphone-assisted RGB method, and test paper strip analysis. The binding mechanism of probe L with metal ions was studied using H NMR, ESI mass spectrometry, and DFT calculations. The zeta potential analysis showed a potential of -28.38 mV for the free ligand and +12.09 mV upon complexation with Ni. More importantly, the potential application of probe L includes the quantification of Ni ions in various water samples through all three sensing approaches.
在本研究中，我们展示了三种不同的比色法检测镍离子的方法，使用通过克诺文格尔缩合反应高产率合成的一种特殊设计的苯并噻唑 - 喹啉二元化合物（L）。L的独特性质使其能够对镍离子做出快速且选择性的响应，使其成为实际应用中的理想探针。探针L在正常条件下呈浅黄色。与镍离子相互作用时，L会发生显著的颜色变化，从浅黄色变为亮橙色，从而可在半水介质中进行目视检测。这种快速的比色响应能够实时监测镍的浓度。由于配体到金属的电荷转移（LMCT），L的最大吸收峰在镍离子存在下发生红移。通过乔布氏图和电喷雾电离质谱分析证实，探针L可形成化学计量比为2∶1 [L∶Ni]的配合物，估计缔合常数为2.61×10 M。通过紫外 - 可见分光光度计、智能手机辅助RGB方法和试纸条分析，探针L能够检测低至61 nM、106 nM和129 nM的镍浓度。使用核磁共振氢谱、电喷雾电离质谱和密度泛函理论计算研究了探针L与金属离子的结合机制。zeta电位分析表明，游离配体的电位为 - 28.38 mV，与镍络合后为 + 12.09 mV。更重要的是，探针L的潜在应用包括通过所有三种传感方法对各种水样中的镍离子进行定量分析。
