Series of Cadmium-Organic Frameworks Based on Mixed Flexible and Rigid Ligands: Single-Crystal-to-Single-Crystal Transformations, Sorption, and Luminescence Properties

Here, we present a series of Cd(II) coordination polymers containing two types of ligands: sterically rigid terephthalate derivatives (bdc-NO22- and bdc-Br2-) and flexible bis(2-methylimidazolyl)propane (bmip). The combination of two types of ligands is used to obtain and characterize compounds by single crystal and powder X-ray diffraction, FT-IR, elemental analysis, and TGA. Guest exchange results in structural transformations. 2-fold interpenetrated 1·DMF and 2·DMF rapidly undergo to 4-fold interpenetrated 1·Et2O, 1·EtOH, and 1·H2O, or 2·Et2O, respectively. Also, changes in the coordinating numbers and length of the N,N'-donor bmip ligand were observed according to single crystal X-ray analysis. Activated guest-free compounds [Cd(bdc-NO2)(bmip)] (1) and [Cd(bdc-Br)(bmip)] (2) are shown to be porous with a BET surface area of 103 and 283 m2·g-1, respectively. Moreover, both compounds demonstrate gate-opening behavior of ethylene adsorption isotherms at low pressures (<1 bar) and highly selective adsorption of benzene over cyclohexane or lower alcohols. Also, both compounds demonstrate a strong dependence of the maximum of the photoluminescence emission on an excitation wavelength. As a result, the photoluminescence color changes from white to red and from blue to red through green and yellow for compounds 1 and 2, respectively, with excitation wavelength changing from 360 to 540 nm.

Crystal structure of poly[diaqua-(μ 2-2,5-dihydroxyterephthalato-κ2 O:O′)(μ 2-bis(4-pyridylformyl)piperazine-κ2 N:N′)cadmium(II)] dihydrate, C24H28CdN4O12

C24H28CdN4O12, monoclinic, P21/c (no. 14), a = 11.0801(4) Å, b = 8.3925(3) Å, c = 13.9503(5) Å, β = 102.810(3)°, Z = 2, V = 1353.89(8) Å3, R gt (F) = 0.0273, wR ref (F 2) = 0.0633, T = 291 K.

The effect of solvent on one-dimensional cadmium coordination polymers

We transformed one one-dimensional coordination polymer directly to another by carrying out a dissolution–recrystallization structural transformation (DRST).

Synthesis, structures and photoluminescence properties of mixed ligand divalent metal–organic frameworks

Crystal engineering is an effective route for synthesis of mixed ligand metal–organic frameworks with attractive topologies and versatile potential applications.

Crystal structure of hexaaquamanganese(II) bis(3-carboxythiophene-2-carboxylate) C12H18MnO14S2

C12H18O14S2Mn, Triclinic, P1̅, a = 6.5076(10) Å, b = 8.4923(13) Å, c = 9.8092(15) Å, α = 66.6180(10)°, β = 86.903(2)°, γ = 82.235(2)°, V = 493.02(13) Å3, Z = 1, R gt (F) = 0.0569, wR ref (F 2 ) = 0.1756, T = 296(2) K.

Co5In(BTC)4[B2O4(OH)]2: the first MOF material constructed by borate polyanions and carboxylate mixed ligands

A novel heterometallic organic–inorganic hybrid MOF material, Co₅In(BTC)₄[B₂O₄(OH)]₂, has been synthesized under ionothermal conditions. Its structure is characterized as a 3D open framework constructed by the Co_2.5In_0.5[B₂O₄(OH)] cluster and the 1,3,5-benzenetricarboxylate ligand.

Crystal engineering of cadmium coordination polymers decorated with nitro-functionalized thiophene-2,5-dicarboxylate and structurally related bis(imidazole) ligands with varying flexibility

Five bis(imidazole) ligand modulated cadmium coordination polymers based on a new nitro-functionalized thiophene-2,5-dicarboxylate ligand or 4-nitro-thiophene-2-carboxylic acid involving in situ ligand synthesis.

Syntheses, structures and luminescence of a series of coordination polymers constructed with 4-substituted 1,2,4-triazole and biscarboxylate co-ligands

Eight coordination polymers were hydrothermal synthesized based on semi-rigid 4-substituted 1,2,4-triazole btpm and biscarboxylate ligands. 1–8 show the structural diversity based on mono-metal, bi-, tri- and tetra-nuclear metal clusters.

The structural diversity and photoluminescent properties of cadmium thiophenedicarboxylate coordination polymers

Two series of Cd(ii) CPs based on two positional isomeric thiophenedicarboxylic acids and N-donor ligands have been synthesized. Moreover, the thermal stability and photoluminescence properties of these complexes are investigated.

Structural modulation in two CuII-based MOFs by synergistic assembly involving the mixed-ligand synthetic strategy and the solvent effect

A synergistic assembly involving the mixed-ligand synthetic strategy and the solvent effect was successfully applied to tune two Cu^II-based MOFs. 1 represents a cds topology, while 2 is built by three distinct {Cu₄} clusters as SBUs.

Two three-dimensional cadmium(ii) coordination polymers based on 5-amino-tetrazolate and 1,2,4,5-benzenetetracarboxylate: the pH value controlled syntheses, crystal structures and luminescent properties

Two 3D cadmium(ii) coordination polymers have been prepared by controlling the pH values of the reaction mixture.

Four d10 metal coordination polymers based on bis(2-methyl imidazole) spacers: syntheses, interpenetrating structures and photoluminescence properties

Combining 2,5-thiophenedicarboxylate and bis(2-methyl imidazole) mixed ligands, four interpenetrating CPs with sql, dmp and dia networks have been constructed.

A series of novel zinc(II) entangled coordination polymers based on carboxyphenyl-terpyridine ligands

Hydrothermal synthesis has afforded five divalent zinc coordination polymers containing 4-(4-carboxyphenyl)-2,2':6',2''-terpyridine (HL1) or its isomer 4-(4-carboxyphenyl)-2,2':4',4''-terpyridine (HL2), with or without the addition of auxiliary ligands, 1,3,5-benzenetricarboxylic acid (H3btc) and 1,4-benzenedicarboxylic acid (H2bdc). Their structures have been characterized by single crystal X-ray analyses and further characterized by infrared spectra, elemental analyses, powder X-ray diffraction, thermogravimetric analyses and photoluminescent spectra. Across this series, the π···π interactions have a dramatic impact on the self-assembly of these entanglement structures, in either case it can exert an important structure-directing role. In addition, the disposition of pyridine nitrogen atoms in ligands also plays a large role in structure direction in this system. Complex 1 is a 2D + 2D→3D inclined polycatenated coordination polymer based on the resulting array of 2D (6,3) layers constructed by 1D→2D π···π directed self-assembly. Complex 2 is assembled into a 3D framework by means of 1D + 1D→3D mutual interdigitation based on 1D→1D self-assembly driven by π···π stacking interactions. Complex 3 shows a 2D + 2D→3D interdigital network involving 2D + 2D→2D parallel interpenetrated and 2D + 2D→2D interdigital (4,4) layer motifs. Complex 4 displays a 2D + 2D→3D polythreaded framework based on a 2D (4,4) network comprised of alternating rings and rods. Complex 5 is a (3,4)-connected 3D framework with topology (4.8(2).10(3))(4.8(2)). In comparison with covalently connected entanglements, such π···π directing self-assembly of entanglements are far less explored, especially, polycatenane based on 1D chain motifs and polythread based on 2D layer motifs are rarely reported. Furthermore, the luminescent properties of complexes 1-5 at room temperature have also been studied in detail herein.