Shui-Sheng Chen

Reversible Single-Crystal-to-Single-Crystal Transformation and Highly Selective Adsorption Property of Three-Dimensional Cobalt(II) Frameworks

A three-dimensional (3D) coordination polymer, [Co(3)(L)(2)(BTEC)(H(2)O)(2)]·2H(2)O [1, HL = 3,5-di(imidazol-1-yl)benzoic acid, H(4)BTEC = 1,2,4,5-benzenetetracarboxylic acid], with tfz-d topology has been hydrothermally synthesized. The framework of 1 has high thermal stability and exhibits single-crystal-to-single-crystal (SCSC) transformations upon removing and rebinding the noncoordinated and coordinated water molecules. X-ray crystallographic analyses revealed that the coordination geometry of Co(II) changes from octahedral to square pyramid upon dehydration, accompanying the appearance of one-dimensional (1D) open channels with dimensions of 2.0 × 2.8 Å. The dehydrated form [Co(3)(L)(2)(BTEC)] (2) exhibits highly selective adsorption of water molecules over N(2), CH(3)OH, and CH(3)CH(2)OH, which could be used as sensors for water molecules. Furthermore, the magnetic properties of 1 and 2 were investigated, showing the existence of ferromagnetic interaction between the Co(II) atoms within the trinuclear subunit.

Spontaneous resolution of two homochiral ferroelectric cadmium(II) frameworks and an achiral framework from a one-pot reaction involving achiral rigid ligands

Unprecedented two homochiral Cd(II) enantiomers and one achiral Cd(II) complex obtained from one pot reaction with achiral mixed rigid ligands 1,3,5-tris(1-imidazolyl)benzene (tib) and 1,4-benzenedicarboxylate (BDC2−) feature interesting entangled structures in which the ligands display huge distortion, and the homochiral enantiomers show ferroelectric property.

Cadmium(II) complexes with 3,5-di(1H-imidazol-1-yl)benzoate: topological and structural diversity tuned by counteranions

Four new coordination polymers [Cd(L)(OAc)]·H2O (1), [Cd(L)(µ2-OH)]·H2O (2), [Cd2(L)2(µ3-SO4)(H2O)2]·5H2O (3) and [Cd(L)2]·H2O (4) with different structures and topologies were obtained by solvo/hydrothermal reactions of varied Cd(II) salts with 3,5-di(1H-imidazol-1-yl)benzoic acid (HL) and 1,3-bis(4-pyridyl)propane (bpp). The structures of 1–4 were characterized by single-crystal X-ray diffraction analysis and the results showed that no bpp ligands were incorporated in the resulting complexes, and more interestingly, complexes 1–3 were obtained by reactions of metal to ligand ratio of 1:1, however, when the reactions were carried out with a metal to ligand ratio of 1:2, the resulting complexes had the same structure, namely [Cd(L)2]·H2O (4). In contrast to the 2D network with 63-hcb topology of complex 1 with acetate as terminal ligand, complex 2 is a 3D (4,6)-connected net with µ2-hydroxyl bridging group. Complex 3 is an unprecedented 3D self-penetrating (3,4,5)-connected net with each sulfate as a µ3-bridge to link three Cd(II) atoms, and complex 4 is a 3D self-penetrating (3,5)-connected net formed by two alternate chiral helical chains linking 2-fold interpenetrating 2D (4,82) nets. The results showed that the L− ligand has varied coordination modes and the counteranions have a great impact on the structure of the complexes.

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.

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.

Three-dimensional lanthanide–silver heterometallic coordination polymers: syntheses, structures and properties

Assembly reactions of 5-(isonicotinamido)isophthalic acid (H2INAIP) with Ln2O3 or Ln(NO3)3·6H2O together with NaOH in the presence of AgNO3 result in formation of two series of new 4d–4f heterometallic coordination polymers {[LnAg(INAIP)2]·3H2O}n [Ln = Nd (1), Sm (2), Eu (3), Gd (4), Tb (5)] and {[LnAg(INAIP)2(H2O)]·xH2O}n [Ln = La (6), Pr (7), Nd (8), x = 0; Dy (9), Er (10), x = 1]. The results of single-crystal X-ray diffraction analysis indicate that 1–5 are isomorphous and have 2-fold interpenetrated 3D structure with 3-nodal net Point (Schlafli) symbol for net: (4·62)4(44·66·815·103), while 6–10 are isostructural with similar non-interpenetrating 3D frameworks containing 2D lanthanide–carboxylate bilayers. The results indicate that the reaction conditions have great influence on the structure of the resulting complexes in this system. Furthermore, 3 and 5 show intense red and green fluorescent emissions, respectively, and the emission bands of Nd(III) were observed in the near IR region for 1. The magnetic properties of 1–5, 9 and 10 were investigated.

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.

Cadmium(II) and zinc(II) complexes with rigid 1-(1H-imidazol-4-yl)-3-(4H-tetrazol-5-yl)benzene and varied carboxylate ligands

Six new coordination polymers [Cd2(HL)2(pbda)(H2O)2]·4H2O (1), [Cd2(HL)2(mbda)(H2O)2]·6H2O (2), [Cd(H2L)(mmbda)(H2O)] (3), [Cd2(H2L)2(btca) (H2O)2]·4H2O (4), [Zn2(H2L)2(btca)] (5) and [Zn6(H2L)6(btca)3] (6) were synthesized by reactions of cadmium(II)/zinc(II) salts with a rigid ligand 1-(1H-imidazol-4-yl)-3-(4H-tetrazol-5-yl)benzene (H2L) and different carboxylic acids of 1,4-benzenedicarboxylic acid (H2pbda), 1,3-benzenedicarboxylic acid (H2mbda), 5-methyl-1,3-benzenedicarboxylic acid (H2mmbda), 1,2,4,5-benzenetetracarboxylic acid (H4btca), respectively. The structures of the complexes were determined by single crystal X-ray diffraction analysis. Although complexes 1 and 2 possess the same two-dimensional (2D) network with (4·82)-fes topology built from Cd(II)–(HL)− moieties, different coordinated orientation of auxiliary carboxylates of pbda2− and mbda2− pillar the 2D layer into distinct frameworks. Complex 1 is an unusual binodal (3,4)-connected three-dimensional (3D) dmc net with Point (Schlafli) symbol of (4·82)(4·85) while 2 is a rare binodal (3,4)-connected 3D architecture with a (4·6·8)(4·62·83) fsc-3,4-C2/c topology. Complexes 3 and 4 have the same 2D networks with (4,4) topology, and H-bonding or π–π stacking interactions extending the 2D layers into 3D supramolecular frameworks, respectively. Complexes 5 and 6 present a pair of pseudopolymorphs, and 5 is an uninodal (4,4)-connected 3D net with Point (Schlafli) symbol of (62·84)(64·82)2 while 6 is an unprecedented penta-nodal 4-connected net with (4·62·83)2(4·64·8)2(62·84)(64·82)4 topology. The thermal stability and photoluminescent property of the complexes were investigated.

The roles of imidazole ligands in coordination supramolecular systems

Imidazole is a fundamental building unit possessing a conjugated five-membered ring system with two N-donor coordination sites. The parent imidazole nucleus can be derivatized to three types of compounds at the 1-, 2-, or 4-positions, generating 1, 2, or 4-imidazole-containing ligands, or can be endowed with other functional groups to form multi-functional ligands. Imidazole and its derivatives have been widely employed as excellent candidates for targeted metal–organic frameworks (MOFs) in the domain of coordination chemistry. Moreover, recent reports show a boom in exploratory synthesis using imidazole derivatives to construct novel MOFs due to their distinct characteristics. In consideration of the rapidly growing research on imidazole ligands, herein, we would like to highlight the recent advances in the rational design of MOFs based on imidazole derivatives from our and other research groups; we would also like to provide new insights into the rational design of organic tectons and the construction of these advanced crystalline materials with desirable properties and functionalities.