Dual-Emission from a Single-Phase Eu–Ag Metal–Organic Framework: An Alternative Way to Get White-Light Phosphor

Abstract

A new bifunctional NTB (tris(benzimidazol-2-ylmethyl)amine)-type ligand incorporating coordination discriminable tripodal benzimidazolyl and monodentate pyridyl groups, tris((pyridin-3-ylmethyl)benzoimidazol-2-ylmethyl)amine (3-TPyMNTB), has been prepared to assemble 4d–4f heterometallic three-dimensional metal–organic frameworks (MOFs) in a stepwise route: (1) direct reaction of 3-TPyMNTB with Ln(ClO 4 ) 3 affords monomeric complexes [Eu(3-TPyMNTB) 2 ](ClO 4 ) 3 ·2.5MeCN ( 1 - Eu ) and [Gd(3-TPyMNTB) 2 ](ClO 4 ) 3 ·2MeCN·2CHCl 3 ( 1 - Gd ), and (2) assembly of the precursors 1 - Eu and 1- Gd with AgClO 4 gives rise to infinite MOFs [EuAg 3 (3-TPyMNTB) 2 (H 2 O)(MeCN)](ClO 4 ) 6 ·4MeCN ( 2 - Eu - Ag ) and [GdAg 3 (3-TPyMNTB) 2 (H 2 O)(MeCN)](ClO 4 ) 6 ·4MeCN ( 2 - Gd - Ag ), respectively. In monomer 1 - Eu, the ligand shows an antenna effect to transfer absorbed energy to Eu 3+ center to emit characteristic red luminescence, while in 4d–4f heterometallic MOF 2 - Eu - Ag, the ligand centered emission is resensitized by Ag + ions to generate dual emissions, coming up with the direct white-light emission from a single crystal. The detailed photoluminescent study has been carried out in both solid state and solution to elucidate the emission nature.