Synthesis and structural elucidation of a unique turn-off fluorescent sensor based on oxo-bridged tin (IV) cluster for selective detection of dopamine in biological fluids

A unique TOC chemosensor for fluorescence sensing of dopamine in human blood plasma. [Display omitted] •An oxo-bridged tin(IV) cluster was synthesized and thoroughly characterized by spectroscopic and single crystal X-ray diffraction studies.•TOC exhibits selective turn-off fluorescence sensing for Dopamine over other analytes.•Application studies were performed in human blood plasma.•Confocal imaging studies were performed to investigate TOC sensing ability to detect DA in human blood serum.•DFT studies further support the sensing mechanism. An oxo-bridged Sn (IV) Cluster, (TOC) was synthesized and fully characterized by FT-IR, UV–vis, 1H NMR, 119Sn NMR, Mass spectrometry and single crystal X-ray diffraction studies. The single-crystal X-ray analysis revealed that the crystal crystallizes in the monoclinic crystal system possessing the P 21/c space group and exhibited a distorted trigonal bipyramidal geometry. The TOC exhibited a unique turn-off fluorescence response for the selective detection of dopamine (DA) over other analytes. The stoichiometry between the TOC and DA was calculated using Job’s plot. The value of the detection limit was found to be 1.33 µM. The Hirshfeld surface analysis was carried out on the crystal structure to investigate the H-H, Cl-H, Cl-Cl, Sn-Cl and Cl-C interaction studies in the molecule. Density Functional Theory (DFT) studies further supported the sensing mechanism, which closely agreed with the experimental results. Furthermore, the TOC chemosensor was used to detect DA in human blood plasma, and molecular docking studies validated the interaction between the chemosensor and protein. Confocal fluorescence imaging studies were carried out and validated TOC sensing ability for DA in human blood plasma.