Syntheses and non-covalent interactions of naphthalene-bearing Schiff base complexes of Zn(II), Co(III), Cu(II) and V(IV): Selective detection of Zn(II)

A new Schiff base ligand, 1-[(2-pyridin-2-yl-ethylimino)-methyl]-naphthalen-2-ol, (HPEMN) has been synthesized equipped with naphthalene and pyridine backbone, to study the interplay of various non-covalent interactions. Experiments have been carried out to investigate the outcome of combinations of HPEMN and ZnCl2 (1), ZnBr2 (2), ZnI2 (3), Zn(NO3)2·6H2O (4), Co(ClO4)2·6H2O (5), Cu(ClO4)2·6H2O (6) and VO(acac)2 (7). The prevalent non-covalent interactions described here include naphthalene–naphthalene (for 1, 2, 3 and 5) and pyridine–pyridine π–π stacking (for 4) interactions, nitrate anion⋯π interaction (for 4) and hydrogen bonding (for 6). HPEMN is able to sense Zn(II) selectively and this phenomenon was further demonstrated by the results of fluorescence studies in H2O/acetonitrile (8:2, v/v) HEPES buffer (pH = 7.4) solution and human lung cancer cell lines.

Graphical AbstractZn(II), Co(III), Cu(II) and V(IV) complexes of a naphthalene bearing Schiff base were synthesized and structurally characterized. The complexes demonstrate a plethora of non-covalent interactions including naphthalene–naphthalene, pyridine–pyridine π–π stacking, nitrate anion⋯π interaction and hydrogen bonding. Selective Zn(II) detection ability was also explored in detail.Figure optionsDownload as PowerPoint slide