Benzazolate complexes of pentacoordinate nickel(II). Synthesis, spectroscopic study and luminescent response towards metal cations

[Ni(mcN3)(hpbY)](PF6) (1a–3b) [mcN3 = Me3–mcN3 (2,4,4-trimethyl-1,5,9-triazacyclododec-1-ene); Me4–mcN3 (its 9-methyl derivative); hpbY = hpbm (2-(2′-hydroxyphenyl) benzimidazolate); hpbx (2-(2′-hydroxyphenyl) benzoxazolate); hpbt, 2-(2′-hydroxy phenyl)benzothiazolate] were synthesized via acid–base method and structurally characterized. The complexes exhibit moderate fluorescence intensities. Hetero-atoms of benzazole ligands present in the Ni(II) complexes influence their luminescent properties. These complexes are used for the recognition of different cations of biological and environmental interest. The study of luminescence properties of these complexes reveals that they display good sensitivity towards transition metal ions ZnII, CuII and HgII. The complexes act as sensitive fluorescent ON−OFF probe for CuII. Other metal ions such as HgII and ZnII gave an enhanced fluorescence response.

Graphical abstractHetero-atoms of benzazole ligands present in the Ni(II) complexes described in this work influence the luminescent properties. Giving rise to three types of behavior, which include on–off sensor with Cu(II) and enhancement luminescent intensity with Hg(II) and Zn(II). These complexes are used for the recognition of different cations of biological and environmental interest.Figure optionsDownload full-size imageDownload as PowerPoint slide