Development Of A Simple Organic Probe For Colorimetric Detection Of Cu²⁺

Copper is an important trace metal in many living organisms and plays important roles in different physiological processes.It is widely used by human in all parts of life including industry,households,vehicles,airplanes etc.Excess of copper into the food chain is toxic and causes serious health problems in plants,animals and human.Therefore,selective,sensitive and instant detection methodologies development for Cu²⁺is important.In the present study we investigated the synthesis and evaluation of an organic molecule for chromogenic sensing of Cu²⁺in aqueous organic medium based on principles of molecular recognition.We focused on design and synthesis of a salicylaldehyde and benzyldithiocarbazate based probe（SalTCB）suitable as sensor for Cu²⁺among commonly occurring metal cations.This selective sensing phenomenon was associated with the ONS binding of the probe to Cu²⁺associated with color change from colorless to yellow.This sensing phenomenon could be observed through naked eye as this binding resulted optical change noticeable through naked eye.This coordination property of SalTCB for Cu²⁺was investigated as selective Cu²⁺sensor.The colorless SalTCB change to yellow when react with Cu²⁺in buffered acetonitrile water mixture.This sensing property was studied in detail by ¹H NMR,IR,HR-ESI-MS and UV-vis spectroscopy.The probe benzyl 2-（2-hydroxybenzylidene）-1-methylhydrazine-1-carbodithioate（SalTCB）gave a new tetra-nuclear sulphate bridged complex（Cu₄（SalTCB）₄（SO₄）₂）（SalTCB-Cu）after reaction with CuSO₄ at room temperature in CH₃CN/CH₃OH/H₂O mixture,which was characterized by IR,UV-vis spectroscopy,HR ESI-MS,elemental analysis and single crystal X-ray.The solid-state characterization showed a 1:1 complex formation between the SalTCB and Cu²⁺.Job’s plot and mass spectrometric analysis also indicated a 1:1 interaction of SalTCB with Cu²⁺.We studied eighteen commonly occurring metal ions in the interference study and found that this sensing property of SalTCB for Cu²⁺was not interfered by any other commonly competing metal ions.The limit of detection（LOD）for Cu²⁺was as low as 0.51μM,which was far below the WHO permitted level of Cu²⁺in drinking water i.e.20μM.SalTCB was retrieved completely using EDTANa₂.Similarly,SalTCB solution based methodology was developed that afforded instant naked eye detection of Cu²⁺.In conclusion,we investigated a simple organic probe for highly selective sensing of Cu²⁺through naked eye or simple UV-vis spectroscopy and the binding of the probe with Cu²⁺was thoroughly investigated by detailed chemical structure elucidating techniques.