Recognition of Some Metal Ions Using N,N-, N,O- or N,S-Donor Ligands and Cytotoxicity, Cell Imaging Studies

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My Thesis contains five chapters. Chapter 1 is about Introduction, Materials and Methods. In this chapter introduction about Fluorescence and various sensing mechanisms are explained. Some recent literature reports based on metal ion detection using different fluorescent probes have been discussed. Along with this, materials, methods and instrumentation related to this thesis are described in details. In Chapter 2 the heterocyclic probe 3-(1-isoquinolinyl)imidazo[5, 1-a]isoquinoline (L1) in CH3OH/HEPES buffer system (5 mM, pH = 7.4, 6:4, v/v), exhibits blue fluorescence (λem = 454 nm) upon excitation with 359 nm light. Upon adding Pd2+ ion solution, L1 shows “turn-off” response. Job’s plot and ESI mass spectrometric analysis reveal a 1:1 ratio for binding of L1 with Pd(II) ion. DFT/TDDFT calculations performed on [Pd(L1)Cl(CH3CN)]+ ion support the experimental findings. Fluorescence imaging in the absence and presence of Pd2+ revealed that L1 can be successfully applied on living cells with outstanding sensitivity. In Chapter 3 the heterocyclic probe 3-(2-hydroxyphenyl)imidazo[5, 1-a]isoquinoline (L2H) has exhibited specific recognition of Cu2+ ion by forming a complex of formula [Cu(L2)2], which in turn showed recognition for CN– ions with in CH3CN/aqueous HEPES-buffer solution (5 mM, pH = 7.4, 6:4, v/v). Based on the cytotoxic analysis, 5 M of L2H was selected for determining its fluorescence attributes in cellular imaging in MDA-MB-231 and HDF cells. In Chapter 4 Schiff base probe (L3) containing coumarin and pyrene moieties is synthesized and characterized which can detect trivalent M(III) ions (M = Al, Cr and Fe) through “OFF-ON” fluorescence process. Fluorescence intensity of these M(III) bound L3 complexes is quenched by fluoride ions. From cytotoxicity analysis, 7.5 μM of probe L3 was selected to analyze its fluorescence attributes in cellular imaging. In Chapter 5 the probe (L4) having hydrazinecarbothioamide and 1,8-naphthalimide moieties has been synthesized and evaluated for its metal ion sensing ability. It exhibits a selective and sensitive colorimetric as well as fluorescent recognition of Hg2+ and Ag+ ions in CH3OH - HEPES buffer solution (5 mM, 7:3, v/v, pH = 7.4). The DFT/TDDFT calculation has revealed a decrease in energy of the HOMO-LUMO gap in mercury and silver complex thereby supporting the experimentally observed red shift in absorption bands. Based on the cytotoxic assay, 5 M concentration of probe L4 was considered for intracellular detection of Hg2+ and Ag+ ions in MDA-MB-231 and HDF cells through “turn-on” fluorescence response.
Supervisor: V Manivannan