Design And Syntheses Of Fluorogenic Probes For Selective Detection And Bioimaging Of Transition Metals

In metal ion sensing,a minor alteration in the ligand can be the source of an immense transformation with respect to selectivity of the sensor and affect its sensing mechanism.Fluorescent probes are a beneficial and convenient tool for the recognition of biologically related species in vitro and in vivo including metal ions because of their specificity and sensitivity and accuracy and fast response time.Once the ligand identifies the target analyte,the fluorescence signal can be perceived as enhancement,shift in the fluorescence maxima or quenching,due to either energy transfer(ET),electron transfer(eT),or charge transfer(CT)processes.In this dissertation,we focus on the design,synthesis and biological applications of fluorescent sensors,for the transition metals.Fluorescent sensors can be classified in to "turn-on"(enhancement)"turn-off"(quenching),and ratiometric(signal shift upon identification of the target analyte).This dissertation emphasizes on "turn-on" fluorescent probes for Cobalt(?),Nickel(II),and Palladium(0).A diverse class of fluorogenic sensors exhibiting absorbance or fluorescence modifications in signals upon binding with Co(?)ions have been reported.Though,generally these fluorescent probes display quenching of fluorescence signal and limited selectivity.Two fluorescent sensors for selective detection of Co(?)have been synthesized,a quench probe SNP1 comprising naphthalimide as a fluorophore.The SNP1 shows bright fluorescence in aqueous solution,but displays fluorescence quenching after the addition of Co(?)ions,this response is attributed to the Co(?)-paramagnetic behavior.Other one is SGPB1 with fluorescence "turn-on",both use Salicylhydrazide as Co(?)-recognition unit.Both fluorescence probes are selective and sensitive towards Cobalt(?)ions,and possess a nanomolar level limit of detections.Both probes proved suitable for bioimaging experiments.Chapter 3 utilizes 1,8-naphthalimide as fluorophore,for the development of a "turn-on"fluorescent sensor for Ni(?)ions.This chapter unveils that independent probe NiP possessed very weak fluorescence but displayed a high selectivity(?160-fold)and sensitivity for Ni(II)detection by PET mechanism.The diverse applicability of NiP can be recognized as it can detect Ni(?)at subcellular level of living cells,as NiP can localize in mitochondria.This approach offers advantages by being fast,simple,and low cost.Chapter 4 reveals a colorimetric fluorescent probe NI-Pd for the detection of Pd(0)specie in living cells and in vivo,based on ICT mechanism.The chemosensor utilizes naphthalimide derivative as fluorophore,and can be applied in one photon and two photon cell imaging.