Jian-Yong Zhang

Solvent-controlled structural diversity observed in three Cu(II) MOFs with a 2,2′-dinitro-biphenyl-4,4′-dicarboxylate ligand: synthesis, structures and magnetism

Three extended three-dimensional CuII-based metal–organic frameworks (MOFs) have been separated successfully from reactions of 2,2′-dinitro-biphenyl-4,4′-dicarboxylate (H2dnpdc) and Cu(NO3)2 under controllable solvothermal conditions. The resulting structures of the MOFs are highly dependent on the solvent used during the synthesis. Compound 1, [Cu(dnpdc)(H2O)]n·(DMA)4(H2O)2, is a two-fold interpenetrated three-dimensional framework with NbO topology based on a binuclear [Cu2(O2C)4] “paddle-wheel” secondary building unit. In compound 2, [Cu9(dnpdc)6(OH)6(H2O)2]n·{(DMF)8(EtOH)3(H2O)12}n, the complicated one-dimensional [Cu(OH)(OCO)]n chains are cross-linked into three-dimensional frameworks by the dnpdc2− ligands. Compound 3, {Cu4(dnpdc)3(OH)2(py)4}n, displays three-dimensional nets with pcu topology based on 6-connected [Cu(μ3-OH)2(OCO)4] tetracopper clusters. Magnetically, compound 2 exhibits homo-spin topological ferrimagnetic behavior. Compound 3 features antiferromagnetic interactions mediated by μ3-OH and syn–syn-OCO heterobridges between the CuII ions.

N-donor auxiliary ligand-directed assembly of CoII compounds with a 2,2′-dinitro-biphenyl-4,4′-dicarboxylate ligand: structures and magnetic properties

To explore the influence of different N-donor auxiliary ligands on the self-assembly and structures of CoII-based coordination polymers (CPs), six coordination compounds, formulated as {Co(dnpdc)(bipy)}n (1), {[Co3(dnpdc)3(bipy)3(H2O)2]·2H2O}n (1s), {[Co5(OH)2(dnpdc)4(bpp)2(H2O)2]·2H2O}n (2), {[Co5(OH)2(dnpdc)4(bpp)2(H2O)2]·2H2O}n (3), {Co(dnpdc)(bcim)·(H2O)0.5}n (4) and {Co2(dnpdc)2(bpee)(bpim)}n (5) where bipy = 4,4′-bipyridine, bpee = bis(4-pyridyl)ethene, bpp = 1,3-bis(4-pyridyl)propane, bimb = 1,4-bis(imidazolyl)benzene, bcim = 4-bis(imidazol-1-ylmethyl)benzene and bpim = 4,4′-bis(imidazolyl)biphenyl, have been rationally designed and generated through the hydrothermal reaction of the dicarboxylate derivative ligand (H2dnpdc), Co(NO3)2, and a series of different N-donor co-ligands. These N-donor ligands were employed in the crystal preparation of these CPs as structure-directing ligands owing to their structural specialties and size-matching fashions. X-ray analyses revealed that these compounds exhibit two- or three-dimensional architectures. Compounds 1 and 5 are iso-structural, and both exhibit 3D “pillared” frameworks based on 1D [Co(OCO)2]n chains. Compound 1s, prepared at higher temperature, displays unusual (4,6)-connected and three-fold interpenetrated frameworks based on mononuclear and dinuclear nodes. Compound 2 features a new 10-connected 3D topology net based on a novel Co5(μ-OH)2(μ-OCO)6 pentanuclear cluster linked by mixed bpp and dnpdc ligands. Compound 3 exhibits a 6-fold interpenetrated diamond net. Compound 4 shows 2D sheets constructed from flexible bcim and dnpdc ligands. The magnetic properties of compounds 1, 2 and 5 have also been investigated to help us tentatively understand their structure–property relationships.

Structural diversity and catalytic properties of five Co2(COO)4 cluster-based coordination polymers modified with R-isophthalic acid (R = H, NO2, CH3, OH and tBu)

The self-assembly of 5-substituted isophthalic acid (R-H2BDC, R = H, –NO2, –CH3, –OH and –tBu), CoII ions and 2,4,6-tris(4-pyridyl)-1,3,5-triazine (TPT) under solvothermal conditions yielded five Co-based coordination polymers (CPs): {[Co(BDC)(TPT)]·0.5(H2O)}n (CP1), {[Co(NO2-BDC)(TPT)]·H2O}n (CP2), {[Co(CH3-BDC)(TPT)]·0.5H2O}n (CP3), {[Co(HO-BDC)(TPT)]·0.5H2O}n (CP4), and {[Co(tBu-BDC)(TPT)2/3]·(CH3CH2OH)(H2O)}n (CP5) (H2BDC = isophthalic acid, NO2-BDC = 5-nitroisophthalic acid, CH3-BDC = 5-methylisophthalic acid, OH-BDC = 5-hydroxyisophthalic acid and tBu-BDC = 5-tert-butylisophthalic acid). All compounds comprise Co2(COO)4 binuclear units, which are connected via a combination of R-H2BDC and TPT ligands. In CP1, the binuclear Co2(COO)4 units are bridged into 1D chains extending along the [1 1 0] and [−1 1 0] directions, which are further interlinked by TPT ligands into a 3D network with CdS net topology. CP2, CP3 and CP4 are iso-structural and all exhibit 3D frameworks with pcu (α-Po) topology. In CP5, the Co2(COO)4 units are firstly linked into a 3D NbO net viatBu-BDC ligands, which are further accommodated by size-matching trigonal TPT ligands into a novel (3,8)-connected 3D net. Catalytic measurements show that CP2 and CP3 are good catalysts for the Knoevenagel condensation reaction of benzaldehyde with ethyl cyanoacetate, exhibiting conversions of 91.3% and 96.6% in 120 min, respectively, compared with the other present compounds. In addition, CP2 and CP5 exhibit highly efficient catalytic properties for the selective epoxidation of styrene.