Adjustment of coordination environment of Ln3+ ions to modulate near-infrared luminescent properties of Ln3+ complexes

With the Zn-Schiff-base [ZnL(Py)] from the pure Salen-type Schiff-base ligand H2L (H2L = N,N′-bis(salicylidene)ethylene-1,2-diamine) as the precursor, a series of hetero-trinuclear Zn2Ln complexes [Zn2Ln(L)2(NO3)2(SCN)(Py)2] (Ln = Nd, 1; Ln = Yb, 2; Ln = Er, 3 and Ln = Gd, 4) are obtained by the further reaction with Ln(NO3)3·6H2O and KSCN on the condition of stoichiometry control, respectively. The influence of molecular structures on the photophysical properties shows their NIR luminescent properties are hypersensitive to the composition and symmetry of the coordination environments of Ln3+ ions bonded with the mixed anions, which provides a wide variety of means to modulate the NIR luminescence of Ln3+ complexes.

Graphical AbstractA series of hetero-trinuclear Zn2Ln complexes [Zn2Ln(L)2(NO3)2(SCN)(Py)2] (Ln = Nd, 1; Ln = Yb, 2; Ln = Er, 3 and Ln = Gd, 4) are obtained from the further reaction of Ln(NO3)3·6H2O and KSCN on the condition of stoichiometry control with the Zn-Schiff-base [ZnL(Py)] precursor from the pure Salen-type Schiff-base ligand H2L (H2L = N,N′-bis(salicylidene)ethylene-1,2-diamine), respectively. The correlation between the molecular structures and the photophysical properties shows their NIR luminescent properties are hypersensitive to the composition and symmetry of the coordination environments of Ln3+ ions bonded with the mixed anions, which provides a wide variety of means to modulate the NIR luminescence of Ln3+ complexes.Figure optionsDownload as PowerPoint slideResearch Highlights
► Through the adjustment of the chemical environment of 4f ions induced by mixed anions in the series of trinuclear Zn2Ln complexes of the pure Salen-type Schiff-base ligands, the modulation of their NIR luminescence should be relatively effective.
► hetero-trinuclear Zn2Ln complexes;
► effective modulation of NIR luminescence;
► mixed anions inducement.