Aroylhydrazone derivative as fluorescent sensor for highly selective recognition of Zn2+ ions: syntheses, characterization, crystal structures and spectroscopic properties

A new Zn2+ fluorescent chemosensor N'-(3,5-di-tert-butylsalicylidene)-2-hydroxybenzoylhydrazine (H3L1) and its complexes [Zn(HL1)C2H5OH](infinity) (1) and [Cu(HL1)(H2O)]CH3OH (2) have been synthesized and characterized in terms of their crystal structures, absorption and emission spectra. H3L1 displays high selectivity for Zn2+ over Na+, K+, Mg2+, Ca2+ and other transition metal ions in Tris-HCl buffer solution (pH = 7.13, EtOH-H2O = 8 : 2 v/v). To obtain insight into the relation between the structure and selectivity, a similar ligand 3,5-di-tert-butylsalicylidene benzoylhydrazine (H2L2), which lacks the hydroxyl group substituent in salicyloyl hydrazide compared with H3L1, and its complex [Zn-2(HL2)(2)(CH3COO)(2)(C2H5OH)] (3), [Co(L-2)(2)][Co(DMF)(4)(C2H5OH)(H2O)] (4), [Fe(HL2)(2)]Cl center dot 2CH(3)OH (5), have also been investigated as a reference. H3L1 exhibits improved selectivity for Zn2+ compared to H2L2. The findings indicate that the hydroxyl group substituent exerts an effect on the spectroscopic properties, complex structures and selectivity of the fluorescent sensor.