Xiao-Min Kan

Transition metal carboxylate coordination polymers with amide-bridged polypyridine co-ligands: assemblies and properties

Coordination polymers (CPs) can be formed by the self-assembly of metal ions and one kind of ligand or mixed ligands. Carboxylate anions have been extensively utilized to construct metal–organic CPs with diverse structures and topologies as well as versatile properties. The introduction of neutral nitrogen-donor co-ligands in such metal carboxylate system is an effective strategy for tuning the architectures and functionalities of metal–organic CPs. As a family of neutral nitrogen-donor co-ligands, amide-bridged polypyridine compounds have been introduced into such metal carboxylate system in the past decade. A large number of metal–organic CPs derived from the mixed ligands of carboxylate and amide-bridged polypyridine have been reported. Therefore, we present the recent developments of transition metal carboxylate CPs with amide-bridged polypyridine co-ligands in this highlight. We summarize their syntheses, structures, architectural influence factors and properties in detail. Such highlight may play a significant role in the rational design and construction of amide-bridged polypyridine-based transition metal carboxylate CPs with structure-dependent properties.

Polyoxometalate-directed assembly of various multinuclear metal–organic complexes with 4-amino-1,2,4-triazole and selective photocatalysis for organic dye degradation

A series of polyoxometalate (POM)-based metal–organic complexes containing multinuclear Cu(II) clusters with a 4-amino-1,2,4-triazole (4-atrz) ligand, namely, [Cu3(4-atrz)8(PMo12O40)2(H2O)2]·2H2O (1), [Cu2(4-atrz)6(SiW12O40)(H2O)]·6H2O (2), [Cu2(4-atrz)4(μ2-OH)(CrMo6(OH)6O18)]·3H2O (3), [Cu3(4-atrz)3(Mo8O27)(H2O)4]·6H2O (4) and [Cu3(4-atrz)3(V10O30)0.5(μ3-OH)(H2O)]·H2O (5) have been synthesized by selectively adding additional citric acid or boric acid under hydrothermal conditions and have been structurally characterized by single-crystal X-ray diffraction and powder X-ray diffraction. Compound 1 has a zero-dimensional (0D) architecture, which is constructed from a linear trinuclear cluster [Cu3(4-atrz)8(H2O)2]6+ and two Keggin PMo12O403− anions. Compound 2 shows a 1D zigzag chain, in which the binuclear [Cu2(4-atrz)6(H2O)]4+ clusters and Keggin SiW12O404− anions connect to each other. Compound 3 is a 1D linear chain based on linear [Cu3(4-atrz)6]6+ clusters; the [CrMo6(OH)6O18]3− anions hang on two sides of the 1D chain. Compound 4 has a 2D layer constructed from trigonal [Cu3(4-atrz)3(H2O)4]6+ clusters and rare infinite [Mo8O27]n6n− chains. The [Mo8O27]6− anion is transformed from the Anderson-type [CoMo6(OH)6O18]3− anion, which is also rare in the POM-based reaction system. Compound 5 has a 3D framework constructed from trigonal trinuclear [Cu3(4-atrz)3(OH)]5+ clusters and rare [V10O30]10− polyanions, which represents the first example of a V10O30-based 3D metal–organic complex. Structural analyses indicate that different POMs show great effect on the various structures of 1–5 and the additional acids play an important role in the formation of 1–5. Photocatalytic experiments of 1–5 on degradation of three organic dyes (methylene blue, Rhodamine B and methyl orange) manifest that compounds 1–3 are good candidates for the photocatalytic degradation of methylene blue, and compound 1 is a good photocatalyst for the degradation of Rhodamine B.

Systematic Investigation of Reaction-Time Dependence of Three Series of Copper–Lanthanide/Lanthanide Coordination Polymers: Syntheses, Structures, Photoluminescence, and Magnetism

Three series of copper-lanthanide/lanthanide coordination polymers (CPs) Ln(III) Cu(II) Cu(I) (bct)3 (H2 O)2 [Ln=La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Dy (9), Er (10), Yb (11), and Lu (12), H2 bct=2,5-bis(carboxymethylmercapto)-1,3,4-thiadiazole acid], Ln(III) Cu(I) (bct)2 [Ln=Ce (2 a), Pr (3 a), Nd (4 a), Sm (5 a), Eu (6 a), Gd (7 a), Tb (8 a), Dy (9 a), Er (10 a), Yb (11 a), and Lu (12 a)], and Ln(III) 2 (bct)3 (H2 O)5 [Ln=La (1 b), Ce (2 b), Pr (3 b), Nd (4 b), Sm (5 b), Eu (6 b), Gd (7 b), Tb (8 b), and Dy (9 b)] have been successfully constructed under hydrothermal conditions by modulating the reaction time. Structural characterization has revealed that CPs 1-12 possess a unique one-dimensional (1D) strip-shaped structure containing two types of double-helical chains and a double-helical channel. CPs 2 a-12 a show a three-dimensional (3D) framework formed by Cu(I) linking two types of homochiral layers with double-helical channels. CPs 1 b-9 b exhibit a 3D framework with single-helical channels. CPs 6 b and 8 b display visible red and green luminescence of the Eu(III) and Tb(III) ions, respectively, sensitized by the bct ligand, and microsecond-level lifetimes. CP 8 b shows a rare magnetic transition between short-range ferromagnetic ordering at 110 K and long-range ferromagnetic ordering below 10 K. CPs 9 a and 9 b display field-induced single-chain magnet (SCM) and/or single-molecule magnet (SMM) behaviors, with Ueff values of 51.7 and 36.5 K, respectively.

Syntheses, structures, and magnetic properties of two series of copper-lanthanide heterometallic coordination polymers based on pyridine-2,3-dicarboxylic acid and succinic acid

Two series of copper-lanthanide heterometallic coordination polymers (CPs), [LnCu(2,3-pydc)2(suc)0.5(H2O)3]·H2O [Ln = La (I), Pr (II), Nd (III), Sm (IV), Gd (V), and Eu (VI), 2,3-H2pydc = pyridine-2,3-dicarboxylic acid, H2suc = succinic acid], [Ln2Cu3(2,3-pydc)6(H2O)10]·8H2O [Ln = Eu (VII), Tb (VIII), Dy (IX), and Er (X)], [Ln2Cu(2,3-pydc)2(suc)(μ2-OH)2(H2O)2]·2H2O [Ln = Er (XI), Yb (XII), and Lu (XIII)], [Ln2Cu(2,3-pydc)2(suc)2(H2O)6]·2H2O [Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5), and Er (6)], and Ln2Cu(2,3-pydc)2(suc)2(H2O)2 [Ln = Er (7), Yb (8), and Lu (9)], were successfully synthesized by the hydrothermal reactions of Cu(NO3)2·3H2O, LnCl3·nH2O, 2,3-H2pydc, and H2suc. CPs 1–9 show two types of similar two-dimensional (2D) structures. In 1–9, the 2,3-pydc anions bridge the CuII ions into a one-dimensional (1D) loop chain, and the suc anions link the LnIII ions into a 1D double chain. The 1D loop chains and the 1D double chains connect each other to generate a 2D layer. The adjacent 2D layers are further packed into a three-dimensional (3D) supramolecular architecture by hydrogen-bonding interactions. CPs 4 and 6 display ferromagnetic interactions between the paramagnetic centers, and CP 5 shows a field-induced slow magnetic relaxation behavior. The structures and magnetic properties of I–XIII have been reported in previous work (Eur. J. Inorg. Chem., 2016, 1060).