Metalloreceptors of the type L-M-L [L = (4′-(2-pyridyl)-2,2′:6′,2″-terpyridine), M = Co(II), Cu(II), Zn(II)] for the recognition of Fe2+ ions

Abstract

New complexes of the type [Co(L)2](NO3)2 (P1), [Cu(L)2](NO3)2 (P2) and [Zn(L)2](NO3)2 (P3) where L = (4′-(2-pyridyl)-2,2′:6′,2″-terpyridine) have been synthesized and characterized using standard analytical and spectroscopic techniques (IR, 1H and 13C NMR, UV–Vis, fluorescence and ESR). The structures of the complexes were further authenticated by their single X-ray crystallography. The synthesized complexes are exploited as a receptor in the detection of cations using absorption and emission spectra, as well as cyclic voltammetry for P3 only. UV–Vis spectral titrations of each complex separately with Fe2+ ions displayed a new band at λmax = 570 nm. Among the complexes, only P3 emitted at room temperature at λemi = 450 nm. The intensity of the peak decreases on incremental addition of Fe2+ ions, with a concomitant appearance of a new peak at λemi = 525 nm. Distinct colour changes are observed in all three complexes in the presence of Fe2+ ions. Analytical detection limits using the standard deviation method are found as 1.2, 1.1 and 0.6 µM for complexes P1, P2 and P3 respectively. © 2017