Two d10 Metal–Organic Frameworks as Low-Temperature Luminescent Molecular Thermometers

Abstract

The assemblies of a p-conjugated organic luminophore ligand (p-tr2Ph) and d10 transition metal cations produce two metal–organic frameworks (MOFs), [Zn(μ4-p-tr2Ph)(μ2-NO3)]·NO3 (1), and {[Cd2(μ4-1,4-BDC)2(μ4-p-tr2Ph)(μ2-DMF)(H2O)2]}·2H2O (2) (p-tr2Ph = 1,4-phenylene-4,4′-bis(1,2,4-triazole), DMF = N,N′-dimethylformamide, 1,4-H2BDC = 1,4-dicarboxybenzene). Compound 1 is a new three-dimensional (3D) cationic framework with left-handed helical channels constructed from a right-handed helical chain [Zn(μ2-tr)2(μ2-NO3)]n. Compound 2 possesses a 3D 3-fold interpenetrated neutral framework with one-dimensional distorted hexagonal channels in each MIL-88 type single-net. The compounds 1 and 2 both exhibit blue fluorescence. Notably, the intensity-based luminescent thermometer measurements reveal that compound 2 is extremely more linear with temperature, has finer reversibility within three cycles, and a wider temperature range than those of compound 1, indicating that compound 2 is a more desirable low-temperatur...