Teng-Fei Zheng

Three-dimensional two-fold interpenetrated CrIII–GdIII heterometallic framework as an attractive cryogenic magnetorefrigerant

The hydrothermal reaction of CrO3, Gd2O3 and iminodiacetic acid (H2IDA) yields a three-dimensional (3D) two-fold interpenetrated complex [CrGd(IDA)2(C2O4)]∞ (1). The oxalate anions were generated in situ under hydrothermal conditions. Magnetic studies suggest the presence of weak antiferromagnetic coupling between CrIII and GdIII ions, and negligible GdIII⋯GdIII and CrIII⋯CrIII couplings. Complex 1 exhibits a large magnetocaloric effect with − ΔSmaxm = 39.86 J kg−1 K−1 (the mass aspect) and 93.69 mJ cm−3 K−1 (the volumetric aspect), making it an attractive refrigerant for low-temperature applications.

Two GdIII complexes derived from dicarboxylate ligands as cryogenic magnetorefrigerants

Two GdIII complexes, namely [Gd2(OH)2(oda)2(H2O)4]∞ (1) and {[Gd(fum)(ox)0.5(H2O)2]·2H2O}∞ (2) (H2oda = oxydiacetic acid, H2fum = fumaric acid and H2ox = oxalic acid), have been constructed via hydrothermal reactions. Complex 1 has a one-dimensional (1D) chain structure based on hydroxyl-bridged Gd2O2 cores, while complex 2 exhibits a three-dimensional (3D) framework consisting of Gd6 macrocycles, and can also be seen as a 3D layer-pillar structure with intersected channels occupied by guest water. Magnetic studies indicate that weak antiferromagnetic and ferromagnetic interactions exist between adjacent GdIII ions in 1 and 2, which display large magnetocaloric effects with −ΔSmaxm = 43.3 and 37.1 J kg−1 K−1 for ΔH = 7 T, respectively. Notably, the maximum entropy changes (−ΔSmaxm) of 1 and 2 reach 29.9 and 28.5 J kg−1 K−1, respectively, at 2 K for a moderate field change (ΔH = 3 T). Therefore, 1 and 2 could be regarded as potential magnetorefrigerants for low-temperature applications.

Large magnetic entropy changes in three GdIII coordination polymers containing GdIII chains

Three chain-based GdIII coordination polymers, namely [Gd2(SO4)3(phen)2(H2O)2]n (1), [Gd2(oda)2(ox)(H2O)6]n (2) and {[Gd2(glu)3(H2O)2]·4H2O}n (3) (phen = 1,10-phenanthroline, H2oda = oxydiacetic acid, H2ox = oxalic acid and H2glu = glutaric acid), have been successfully constructed by using multidentate O ligands under hydro/solvothermal conditions. Complex 1 has a one-dimensional (1D) chain bridged by inorganic sulfate, and complex 2 exhibits a 1D double-chain ladder-shaped structure connected by oxalate. While, complex 3 is a three-dimensional (3D) metal–organic framework composed of 1D chains. All of them display good thermal stabilities and large magnetic entropy changes with −ΔSmaxm > 31 J kg−1 K−1 (7 T), suggesting them to be good candidates for use as cryogenic magnetic refrigerants.

Dicarboxylate-induced structural diversity of luminescent ZnII/CdII coordination polymers derived from V-shaped bis-benzimidazole

Six new coordination polymers (CPs) based on the V-shaped 1,3-bis(benzimidazolyl)benzene (bbib) have been synthesized under solvothermal conditions: [Zn(bbib)(ip)]n (1), {[Zn(bbib)(oba)]·solvents}n (2), {[Zn(bbib)(tp)]·DMF}n (3), [Cd(bbib)(ip)]n (4), {[Cd(bbib)(oba)]·H2O·solvents}n (5) and {[Cd(bbib)(tp)]·DMF}n (6) (ip = isophthalate, oba = 4,4′-oxybisbenzoate and tp = terephthalate). Complexes 1–3 display a plane minimal net, (4,4) sheet and a hexagonal plane net, respectively. The structures of 4–6 range from a 1D zigzag chain (4), 2D (4,4) sheet (5) to a 3D “pillar-layer” coordination framework with pcu α-Po topology (6). The structural transition from 1D to 3D among these complexes is realized with the aid of different auxiliary ligands. The results demonstrate that the conformations and coordination modes of dicarboxylate ligands make an impact on the structural diversity of ZnII/CdII coordination polymers. To the best of our knowledge, the CPs based on the bbib ligand have been successfully prepared for the first time. Moreover, complex 2 is a good bifunctional chemosensor for the detection of both Fe3+ and MnO4− with the detection limits of 3.31 ppm and 8.81 ppm, respectively, indicating that 2 could be used as an efficient fluorescent sensor with high sensitivity and selectivity for Fe3+ and MnO4−.