Studying anion-dependent paradoxically fluorescent Cu(II) complexes bearing a pyridine-decorated tetradentate half-salamo-like ligand.

A new pyridine-decorated half-salamo-like ligand (HL) was designed and synthesized. Three novel anion-dependent Cu(II) complexes [Cu(L)Cl]·CH 3 OH (1), [Cu(L)Br] (2) and [Cu(L)(NO 3)] (3) have been synthesized and characterized structurally. Furthermore, DFT calculations were investigated in the complexes 1 , 2 and 3. Paradoxically, the fluorescence intensities of these Cu(II) complexes are significantly increased compared to the ligand. [Display omitted] • A new pyridine-decorated half-salamo-like ligand was synthesized. • Three anion-dependent Cu(II) complexes 1 , 2 and 3 have been synthesized and characterized structurally. • The fluorescence intensities of these Cu(II) complexes are significantly increased compared to the ligand. A new pyridine-decorated half-salamo-like ligand (HL) was designed and synthesized by a one-pot method. Based on this ligand, the single crystals of three anion-dependent Cu(II) complexes [Cu(L)Cl]·CH 3 OH (1), [Cu(L)Br] (2) and [Cu(L)(NO 3)] (3) have been cultivated successfully and the structural features were determined by single crystal X-ray diffraction analyses. The results showed that the complexes 1 , 2 and 3 have homologous mononuclear structures, in which the five-coordinated Cu(II) atom is not only surrounded by the N 3 O cavity of the ligand (L)- unit, but also coordinated with Cl−, Br− and NO 3 − as auxiliary coordination, respectively. The ligand HL and the complexes 1 , 2 and 3 were characterized via elemental analyses, IR and UV–Vis spectroscopy. The short-range interactions of the complexes 1 , 2 and 3 were investigated by Hirshfeld surfaces analyses. Furthermore, DFT calculations were investigated in the complexes 1 , 2 and 3. Paradoxically, the fluorescence intensities of these Cu(II) complexes are significantly increased compared to the ligand. [ABSTRACT FROM AUTHOR]