Zheng-Shuai Bai

Construction of coordination frameworks based on 4-imidazolyl tecton 1,4-di(1H-imidazol-4-yl)benzene and varied carboxylic acids

Nine new coordination polymers [Mn(L)(OX)] (1), [Zn(L)(MBDC)] (2), [Zn(L)(BPDA)] (3), [Co3(L)2(BTA)2]·2H2O (4), [Co2(L)2(BTCA)]·2H2O (5), [Ni(L)(e,a-cis-1,2-CHDC)]·2H2O (6), [Co(L)(e,a-cis-1,4-CHDC)] (7), [Co(L)(e,e-trans-1,4-CHDC)]·2H2O (8) and [Co(L)(e,e,e-cis-1,3,5-HCHTC)]·0.45H2O (9) were obtained by reactions of varied metal salts with 1,4-di(1H-imidazol-4-yl)benzene (L) in the presence of corresponding auxiliary ligands of oxalic acid (H2OX), 5-methyl-1,3-benzenedicarboxylic acid (H2MBDC), 4,4′-biphenyldicarboxylic acid (H2BPDA), benzene-1,3,5-triacetic acid (H3BTA), 1,2,4,5-benzenetetracarboxylic acid (H4BTCA), cis-1,2-cyclohexanedicarboxylic acid (cis-1,2-H2CHDC), cis-/trans-1,4-cyclohexanedicarboxylic acid (cis-/trans-1,4-H2CHDC) and cis-1,3,5-cyclohexane tricarboxylic acid (cis-1,3,5-H3CHTC), respectively. Complex 1 has a one-dimensional (1D) chain structure and 2 has a two-dimensional (2D) network with 63-hcb topology. Complex 3 is a complicated uninodal 4-connected three-dimensional (3D) net with Point (Schlafli) symbol (4·6·83·10)(4·63·82)(63·103)(64·82) while 4 is a (3,8)-connected tfz-d 3D net with Point (Schlafli) symbol (43)2(46·618·84) based on the trinuclear Co(II) secondary building units (SBUs). Complex 5 is a 3-fold interpenetrating mog net with Point (Schlafli) symbol of (4·64·8)2(42·62·82), while 6 is a 2D net with (4,4) topology based on binuclear SBUs. In contrast to the 2D network of 7 with e,a-cis-1,4-CHDC2−, 8 with e,e-trans-1,4-CHDC2− is a 5-fold interpenetrating 66-dia 3D net. Complex 9 has a 1D ladder-like chain structure with a stable conformation from the e,e,e-cis-1,3,5-HCHTC2− ligand. Complexes 2 and 3 exhibit intense light blue emission in the solid state at room temperature and the results of magnetic measurements showed that there are antiferromagnetic interactions in 1.

Cadmium(II) coordination polymers with flexible tetradentate ligand 1,2,4,5-tetrakis(imidazol-1-ylmethyl)benzene: anion effect and reversible anion exchange property

Six new three-dimensional (3D) Cd(II) coordination polymers, {[Cd2(L)3](NO3)4·6H2O}n (1), {[Cd2(L)3](ClO4)4·2H2O}n (2), {[Cd2(L)3](BF4)4·2H2O}n (3), {[Cd(L)Cl2]·2H2O}n (4), {[Cd2(L)2(SO4)2(H2O)]·2H2O}n (5) and {[Cd2(L)(SO4)2(H2O)3]·4H2O}n (6), have been solvothermally synthesized by reactions of the corresponding Cd(II) salts with flexible tetradentate ligand 1,2,4,5-tetrakis(imidazol-1-ylmethyl)benzene (L), respectively. The X-ray diffraction analysis revealed that the isostructural 1, 2 and 3 have 3D framework structures with (46·66·83)2(42·63·8)3 topology. Complex 4 has a different 3D framework structure with (65·8) topology, while 5 and 6 possess pillared-layer and plywood-like 3D framework structures, respectively. The distinct structures of 1 (2, 3), 4 and 5 indicate that the counter anions with different coordination abilities play an important role in the formation of coordination polymers. Complexes 5 and 6, synthesized by the same reactants in the same solvent, have different structures due to the different metal/ligand ratio. In addition, the results also demonstrated that the flexible tetradentate ligand L can adopt varied conformations and coordination modes to form complexes with different structures. L adopts up,up,down,down-conformation in 1–3, while in 4, it has a up,down-conformation. It is interesting that two different conformations of up,down,down,up- and H-type of L coexist in 5. In the case of 6, L has H-type conformation. Furthermore, the reversible anion exchange property of 1 was studied.

Metal–organic frameworks with six- and four-fold interpenetration and their photoluminescence and adsorption property

Three-dimensional interpenetrated metal–organic frameworks (MOFs) {[ZnL2]·4H2O}n (1) and {[Cu(HL)2(H2O)2]Cl2}n (2) were synthesized by reactions of the corresponding metal salt and 1-(imidazol-1-yl)-4-(imidazol-4-yl)benzene (HL) with and without addition of sodium hydroxide, respectively. Complex 1 is a 6-fold interpenetrated porous 66dia framework filled with water molecules, in which the metal atom has distorted tetrahedral coordination geometry and the ligand was deprotonated. While complex 2 with octahedral Cu(II) is a 4-fold interpenetrated dia framework with chloride as counteranions and no deprotonation of the ligand occurred. In addition, the stability, photoluminescence and the adsorption properties of the complexes were studied.

Synthesis and characterization of metal complexes with a mixed 4-imidazole-containing ligand and a variety of multi-carboxylic acids

Six new metal–organic coordination polymers [Ni(L)(adip)(H2O)] (1), [Co(L)(adip)]·H2O (2), [Cd2(L)(adip)2] (3), [Ni(L)(oxba)]·H2O (4), [Co(L)(obea)]·H2O (5) and [Mn3(L)2(bta)2]·2H2O (6) were synthesized by reactions of the corresponding metal salt with the rigid ligand 1,4-di(1H-imidazol-4-yl)benzene (L) and different multi-carboxylic acids of adipic acid (H2adip), 4,4′-oxybis(benzoic acid) (H2oxba), 1,2-phenylenediacetic acid (H2obea), benzene-1,3,5-triacetic acid (H3bta), respectively. The structures of the complexes were determined by single crystal X-ray diffraction analysis. Complexes 1–4 have entangled structures with different topologies: 1 is a 2-fold interpenetrating two-dimensional (2D) network with (4,4) topology containing rare meso-helical chains; 3 is a three-dimensional (3D) uninodal 8-connected self-penetrating net; 2 and 4 are a 3-fold interpenetrating dmp 3D net. Complex 5 is a 2D network with (4,4) topology, while 6 is a typical (3,8)-connected tfz-d 3D net based on the trinuclear Mn(II) subunits. Complex 3 exhibits intense light blue emission in the solid state at room temperature and the results of magnetic measurements show that there are antiferromagnetic interactions in 6.

Synthesis, structure and property of cobalt(II) complexes with 3,5-di(1H-imidazol-1-yl)benzoic acid

Two novel cobalt(II) complexes [Co(L)(NO3)] (1) and [Co(L)(H2O)2]ClO4 (2) were synthesized by reactions of 3,5-di(1H-imidazol-1-yl)benzoic acid (HL) with corresponding cobalt(II) salts, and their structures were determined by single crystal X-ray diffraction analysis. In the title complexes, the carboxylate group of L− ligand adopts a µ2–ŋ1:ŋ1-bridging mode to connect two cobalt(II) atoms, and each L− ligand acts as a 4-connector, and the cobalt(II) has distorted octahedral coordination geometry. In 1, one oxygen atom of the nitrate anion links two cobalt(II) atoms to complete a 3D structure which is a binodal (4,6)-connected net with Schlafli symbol of (3·42·52·6)(32·42·52·64·74·8). While in 2, the 3D structure has topology related to SrAl2, CeCu2 and KHg2 with Schlafli symbol of (42·63·8) and there are 1D channels filled with perchlorate anions. The results revealed that the nature of the counteranions, such as their shape, size and coordination ability, has a remarkable influence on the structure of the complexes. The results of the magnetic measurements showed that there are antiferromagnetic interactions between the neighboring Co(II). Furthermore, complex 2 exhibited a modest second-harmonic-generation (SHG) efficiency and anion-exchange property.

Unprecedented three-dimensional 10-connected bct nets based on trinuclear secondary building units and their magnetic behavior

Three unprecedented metal-organic frameworks [M3(tib)2(CTC)2]·nH2O [M = Co(II), n = 2 (1); Mn(II), n = 2.92 (2) and Ni(II), n = 2 (3)] based on M3(OCO)6 trinuclear secondary building units (SBUs) have been successfully synthesized by reactions of corresponding metal salt with mixed flexible triacid of 1,3,5-cyclohexanetricarboxylic acid (H3CTC) and rigid imidazol-containing ligand 1,3,5-tris(1-imidazolyl)benzene (tib) under hydrothermal conditions. In 1–3, the CTC3− ligands link the SBUs to form two-dimensional (2D) ‘hxl’ (hexagonal lattice) networks and the tib ligands further pillar the 2D layers leading to the formation of three-dimensional frameworks, which are firstly reported uninodal 10-connected bct nets. The magnetic measurements showed that 1 and 3 exhibit ferromagnetic coupling interactions between the adjacent metal centers with g = 2.63, D = 66.69 cm−1, zJ = 0.68 cm−1 and g = 2.22, J = 6.25 cm−1, zj′ = −0.053 cm−1, respectively, while 2 has antiferromagnetic interaction between the Mn(II) ions with g = 2.01, J = −0.57 cm−1, zj′ = 1.3 × 10−4 cm−1.

Metal–organic frameworks with pyridyl- and carboxylate-containing ligands: syntheses, structures and properties

Assembly reactions of pyridyl- and carboxylate-containing ligand 5-(isonicotinamido)isophthalic acid (H2INAIP) with corresponding metal salts result in formation of six new coordination polymers, namely {[Mn(INAIP)(DMF)]·0.5DMF}n (1), {[Mn(INAIP)(H2O)2]·4H2O}n (2), {[Co(INAIP)(H2O)]·2H2O}n (3), {[Co(INAIP)(bpy)0.5]}n (4), {[Co(INAIP)(Him)(H2O)]·H2O}n (5), and {[Cu(INAIP)(Him)(H2O)]·H2O}n (6) (DMF = N,N-dimethylformamide, bpy = 4,4′-bipyridine, Him = imidazole). The results of single-crystal X-ray diffraction analysis indicate that 1 is a two-fold interpenetrated three-dimensional (3D) framework with sra topology, complexes 2, 5 and 6 have two-dimensional (2D) network structure with (6,3) topology, while 3 and 4 have infinite 2D bi-layer structure with different topologies. Complex 3 exhibits a 4-connected network with the Schlafli symbol (43·63), and 4 displays a (4,5)-connected net with Schlafli symbol (43·52·6)(43·55·62). The magnetic and adsorption properties of the complexes were investigated.

Coordination polymers with mixed 4,4′-bipyridine-2,2′,6, 6′-tetracarboxylate and imidazole-containing ligands: synthesis, structure and properties

Three new coordination polymers [Mn4(bptca)2(titmb)(H2O)7]·DMF·4H2O (1), [Ni2(bptca)(titmb)2]·13H2O (2) and [Co2(bptca)(titmb)2]·13H2O (3) were constructed from 4,4′-bipyridine-2,2′,6,6′-tetracarboxylic acid (H4bptca) and 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene (titmb) under hydrothermal conditions. Single crystal X-ray diffraction analysis shows that 1 contains [Mn4(μ2-OCO)4] subunits linked through organic ligands to form a two-dimensional (2D) double-layer structure, while 2 and 3 are isostructural and exhibit a unique three-dimensional (3D) framework with open channels resided by water molecules. The magnetic behavior of 1 and sorption property of 2 have been investigated.