A fluorescent di-zinc(II) complex of bis-calix[4]arene conjugate as chemosensing-ensemble for the selective recognition of ATP

摘要

A triethylene glycol di-imine locked triazole linked bis-calix[4]arene conjugate L has been synthesised and characterised. Conjugate L exhibits high fluorescence enhancement towards Zn~(2+) among the 13 metal ions studied down to a lower detection limit of, 12 ppb. The absorption and visual colour change experiments differentiated the Zn~(2+) from the other metal ions studied. The isolated zinc complex, [Zn_2L] has been used as a chemo-sensing ensemble for the recognition of anions based on their binding affinities towards Zn~(2+). [Zn_2L] was found to be sensitive and selective towards phosphatebearing species and in particular to adenosine triphosphate (ATP~(-2)) among the other 20 anions studied as observed based on the changes occurred in the fluorescence intensity. The selectivity of the ATP~(-2) has been shown on the basis of the changes observed in the emission and absorption spectral studies. The lowest detectable concentration for ATP~(-2) with the chemosensing ensemble [Zn_2L] is 348 ppb in methanol. The fluorescence quenching by the phosphate-based anions has been modelled by molecular mechanics studies and found that the anions possessing two or more phosphate moieties can only bridge between the two zinc centres, and hence those possessing only one phosphate moiety (H_2PO~-_4 and AMP~(2-)) are ineffective.