Effect of Meso Substituents in Tin (IV) Corrole on Chemosensing: Highly Selective Coloro/Fluorimetric Sensing of F ⁻ and CN ⁻ Ions and Their Practical Applicability

Here, we synthesized tin (IV)-based chemosensors (5,10,15-tris(4-cyanophenyl)corrolato)tin (IV)-chloride (Sn1) and (5,10,15-tris(methyl-5-formyl-2-methoxybenzoate)corrolato)tin(IV)-chloride (Sn2) and thoroughly characterized them by various spectroscopic techniques. These receptors, Sn1 and Sn2, exhibit selective colorimetric and fluorogenic responses towards fluoride (F^-) and cyanide (CN^-) anions. The addition of these analytes significantly enhances the fluorescence intensity. Sn1 exhibits a limit of detection (LOD) of 1.65 μM for F^- and 1.7 μM for CN^- ions, while Sn2 has an LOD of 4.8 μM for F^- detection using the fluorometric method. The association constant was calculated to be 2.42 × 10⁴ and 1.45 × 10⁴ for the complexation of Sn1 with F^- and CN^- and 1.21 × 10⁴ for Sn2 with F^-. The larger binding constant and lower LOD of Sn1 and Sn2 demonstrated the ability to sense even traces of target analytes. The sensing ability of Sn1 and Sn2 was comprehensively evaluated through optical, electrochemical, and theoretical studies. The Benesi-Hildebrand and Job's plots suggested a 1:1 binding interaction between the Sn1/Sn2 and respective anions. The ESI mass spectra of Sn receptor + anion complexes revealed that the sensing mechanism involved the exchange of an axial Cl atom with the incoming anions. In addition to that, real-time analysis was also carried out for the detection of F^- ion present in the toothpaste and RGB analysis to depict the applicability of tin (IV) receptors for real-time applications.