The preparation of coordination polymers with good room temperature phosphorescence is the focus of current research. In this paper, zinc and cadmium were used as metal ions and 2,3-pyridinedicarboxylic acid (H 2 L = 2,3-pyridinedicarboxylic acid) was used as organic ligands to successfully synthesize Cd (II) homometallic [CdL]·H 2 O and Zn(II)Cd(II) heterometallic [ZnCdL 2 ]·DMF·5H 2 O coordination polymers microstructures. In addition, morphology, powder X-ray diffraction (PXRD), infrared spectroscopy (IR), elemental analyses, thermogravimetric analysis (TGA) and their luminescence properties were studied. Cd-CP is a micron-sized spherical structure, while Zn/Cd-CP is a flower-like structure formed by the accumulation of sheets. The results show that Cd(II) homo- and Zn(II)Cd(II) heterometallic coordination polymers have quantum yields of 10.05% and 8.54%, respectively. It is worth noting that the lifetime of Cd-CP is 124.62 ms, while the lifetime of Zn/Cd-CP is significantly extended to 363.09 ms after doping with metal ion Zn 2+ . The phosphorescent lifetime of coordination polymers was improved by the heterometallic doping strategy, which provided a new idea and method for the preparation of coordination polymers with long-lived room temperature phosphorescent properties. In addition, the two coordination polymers exhibited blue and cyan fluorescence at 365 nm UV light, respectively, and a green afterglow of about 2 s could be observed with the naked eye when the UV lamp was turned off.
The reaction of X-H2BDC (X = H, Br, NO2 and CH3) and methyl-functionalized dmbpy ligands with metal salts under different solvent media conditions generates nine structurally diverse zinc(II)/cadmium(II)-based coordination polymers (CPs), {[Zn2(BDC)2(DMF)3]·DMF}n (1), [Zn(BDC)2(dmbpy)]n (2), {[(Me2NH2)2Zn3(Br-BDC)4]·3DMF·3H2O}n (3), [Zn2(Br-BDC)2(dmbpy)]n (4), {[Zn13(NO2-BDC)8(μ3-OH)2(μ2-OH)6(H2O)4]·12H2O·2NO3}n (5), [Zn2(NO2-BDC)2(dmbpy)(H2O)2]n (6), {[Cd(NO2-BDC)(dmbpy)0.5(H2O)]·(ACN)·H2O}n (7), [Zn(CH3-BDC)(dmbpy)0.5(H2O)]n (8), and [Zn(CH3-BDC)(dmbpy)0.5]n (9) (H2BDC = isophthalic acid, Br-H2BDC = 5-bromoisophthalic acid, NO2-H2BDC = 5-nitroisophthalic acid, CH3-H2BDC = 5-methylisophthalic acid, dmbpy = 2,2′-dimethyl-4,4′-bipyridine, DMF = N,N-dimethylformamide, ACN = acetonitrile). All the compounds are synthesized using dual linkers (X-H2BDC and dmbpy). 1 and 7–8 show a 2D (4,4) network when dinuclear metal ions and ligands are regarded as nodes and linkers, respectively. 2 is a wave-like chain with BDC ligands alternately pointing up and down. CPs 3–6 and 9 all exhibit 3D networks with 5-connected sqp, 6-connected jsm, 6-connected pcu, (3,4)-connected dmc and 6-connected jsm topologies, respectively. Furthermore, luminescence, thermogravimetric and chemical stability properties of these CPs were investigated. The results suggest that both organic ligands and solvent media influence the final resulting CPs.
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