Coordination Polymers from an Amino-Functionalized Terphenyl-Tetracarboxylate Linker: Structural Multiplicity and Catalytic Properties.

An amino-functionalized terphenyl-tetracarboxylic acid, 2'-amino-[1,1':4',1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid (H4tpta), was used as an adaptable linker to synthesize, under hydrothermal conditions, eight coordination polymers (CPs). The obtained products were formulated as [Co(µ6-H2tpta)]n (1), [Co(µ3-H2tpta)(2,2'-bipy)]n (2), [M3(µ6-Htpta)2(2,2'-bipy)2]n (M = Mn (3), Cd (4)), [Ni2(µ4-tpta)(phen)2(H2O)4]n (5), [Zn2(µ6-tpta)(phen)2]n (6), {[Zn2(µ6-tpta)(µ-4,4'-bipy)]·H2O}n (7), and [Zn2(µ6-tpta)(µ-H2biim)(H2O)2]n (8), wherein 2,2'-bipyridine (2,2'-bipy), 4,4'-bipyridine (4,4'-bipy), 1,10-phenanthroline (phen), or 2,2'-biimidazole (H2biim) are present as additional stabilizing ligands. The structural types of 1-8 vary from one-dimensional (1D) (2, 5) and two-dimensional (2D) (3, 4, 6) CPs to three-dimensional (3D) metal-organic frameworks (MOFs) (1, 7, and 8) with a diversity of topologies. The products 1-8 were investigated as catalysts in the Knoevenagel condensation involving aldehydes and active methylene derivatives (malononitrile, ethyl cyanoacetate, or tert-butyl cyanoacetate), leading to high condensation product yields (up to 99%) under optimized conditions. Various reaction conditions, substrate scope, and catalyst recycling were investigated. This work broadens the application of H4tpta as a versatile tetracarboxylate linker for the generation of diverse CPs/MOFs.

Syntheses, Crystal Structures, and Catalytic Properties of Three Cu(II) and Cobalt(II) Coordination Compounds Based on an Ether-Bridged Tetracarboxylic Acid.

Three new products, [Cu2(µ3-dppa)(2,2'-bipy)2(H2O)]n·2nH2O (1), [Co4(µ4-dppa)2(phen)4(H2O)4]·2H2O (2), and [Co2(µ6-dppa)(µ-4,4'-bipy)(H2O)2]n·3nH2O (3) were synthesized using a hydrothermal method from Cu(II) and Co(II) metal(II) chlorides, 3-(3,4-dicarboxyphenoxy)phthalic acid (H4dppa), and different auxiliary ligands, namely 2,2'-bipyridine (2,2'-bipy),1,10-phenanthroline (phen), and 4,4'-bipyridine (4,4'-bipy). Products 1-3 were characterized by elemental analysis, FTIR, TGA, PXRD, SEM, and single-crystal X-ray crystallography. The structure of 1 features a 1D chain of the 2C1 topological type. Compound 2 shows a discrete tetrameric complex. Product 3 demonstrates a 3D metal-organic framework (MOF) with the new topology. Their structure and topology, thermal stability, and catalytic activity were studied. In particular, excellent catalytic activity was demonstrated for copper(II)-polymer 1 in the cyanosilylation reaction at 35 °C.

Hydrothermal Assembly, Structural Multiplicity, and Catalytic Knoevenagel Condensation Reaction of a Series of Coordination Polymers Based on a Pyridine-Tricarboxylic Acid.

A pyridine-tricarboxylic acid, 5-(3',5'-dicarboxylphenyl)nicotinic acid (H3dpna), was employed as a adjustable block to assemble a series of coordination polymers under hydrothermal conditions. The seven new coordination polymers were formulated as [Co(µ3-Hdpna)(µ-dpey)]n·nH2O (1), [Zn4.5(µ6-dpna)3(phen)3]n (2), [Co1.5(µ6-dpna)(2,2'-bipy)]n (3), [Zn1.5(µ6-dpna)(2,2'-bipy)]n (4), [Co3(µ3-dpna)2(4,4'-bipy)2(H2O)8]n·2nH2O (5),[Co(bpb)2(H2O)4]n[Co2(µ3-dpna)2(H2O)4]n·3nH2O (6), and [Mn1.5(µ6-dpna)(µ-dpea)]n (7), wherein 1,2-di(4-pyridyl)ethylene (dpey), 1,10-phenanthroline (phen), 2,2'-bipyridine(2,2'-bipy),4,4'-bipyridine(4,4'-bipy),1,4-bis(pyrid-4-yl)benzene (bpb), and 1,2-di(4-pyridyl)ethane (dpea) were employed as auxiliary ligands. The structural variation of polymers 1-7 spans the range from a 2D sheet (1-4, 6, and 7) to a 3D metal-organic framework (MOF, 5). Polymers 1-7 were investigated as heterogeneous catalysts in the Knoevenagel condensation reaction, leading to high condensation product yields (up to 100%) under optimized conditions. Various reaction conditions, substrate scope, and catalyst recycling were also researched. This work broadens the application of H3dpna as a versatile tricarboxylate block for the fabrication of functional coordination polymers.

Coordination Polymers Constructed from an Adaptable Pyridine-Dicarboxylic Acid Linker: Assembly, Diversity of Structures, and Catalysis.

4,4'-(Pyridine-3,5-diyl)dibenzoic acid (H2pdba) was explored as an adaptable linker for assembling a diversity of new manganese(II), cobalt(II/III), nickel(II), and copper(II) coordination polymers (CPs): [Mn(µ4-pdba)(H2O)]n (1), {[M(µ3-pdba)(phen)]·2H2O}n (M = Co (2), Ni (3)), {[Cu2(µ3-pdba)2(bipy)]·2H2O}n (4), {[Co(µ3-pdba)(bipy)]·2H2O}n (5), [Co2(µ3-pdba)(µ-Hbiim)2(Hbiim)]n (6), and [M(µ4-pdba)(py)]n (M = Co (7), Ni (8)). The CPs were hydrothermally synthesized using metal(II) chloride precursors, H2pdba, and different coligands functioning as crystallization mediators (phen: 1,10-phenanthroline; bipy: 2,2'-bipyridine, H2biim: 2,2'-biimidazole; py: pyridine). Structural networks of 1-8 range from two-dimensional (2D) metal-organic layers (1-3, 5-8) to three-dimensional (3D) metal-organic framework (MOF) (4) and disclose several types of topologies: sql (in 1), hcb (in 2, 3, 5), tfk (in 4), 3,5L66 (in 6), and SP 2-periodic net (6,3)Ia (in 7, 8). Apart from the characterization by standard methods, catalytic potential of the obtained CPs was also screened in the Knoevenagel condensation of benzaldehyde with propanedinitrile to give 2-benzylidenemalononitrile (model reaction). Several reaction parameters were optimized, and the substrate scope was explored, revealing the best catalytic performance for a 3D MOF 4. This catalyst is recyclable and can lead to substituted dinitrile products in up to 99% product yields. The present study widens the use of H2pdba as a still poorly studied linker toward designing novel functional coordination polymers.

Coordination Polymers from Biphenyl-Dicarboxylate Linkers: Synthesis, Structural Diversity, Interpenetration, and Catalytic Properties.

The present work explores two biphenyl-dicarboxylate linkers, 3,3'-dihydroxy-(1,1'-biphenyl)-4,4'-dicarboxylic (H4L1) and 4,4'-dihydroxy-(1,1'-biphenyl)-3,3'-dicarboxylic (H4L2) acids, in hydrothermal generation of nine new compounds formulated as [Co2(µ2-H2L1)2(phen)2(H2O)4] (1), [Mn2(µ4-H2L1)2(phen)2]n·4nH2O (2), [Zn(µ2-H2L1)(2,2'-bipy)(H2O)]n (3), [Cd(µ2-H2L1) (2,2'-bipy)(H2O)]n (4), [Mn2(µ2-H2L1)(µ4-H2L1)(µ2-4,4'-bipy)2]n·4nH2O (5), [Zn(µ2-H2L1)(µ2-4,4'-bipy)]n (6), [Zn(µ2-H2L2)(phen)]n (7), [Cd(µ3-H2L2)(phen)]n (8), and [Cu(µ2-H2L2) (µ2-4,4'-bipy)(H2O)]n (9). These coordination polymers (CPs) were generated by reacting a metal(II) chloride, a H4L1 or H4L2 linker, and a crystallization mediator such as 2,2'-bipy (2,2'-bipyridine), 4,4'-bipy (4,4'-bipyridine), or phen (1,10-phenanthroline). The structural types of 1-9 range from molecular dimers (1) to one-dimensional (3, 4, 7) and two-dimensional (8, 9) CPs as well as three-dimensional metal-organic frameworks (2, 5, 6). Their structural, topological, and interpenetration features were underlined, including an identification of unique two- and fivefold 3D + 3D interpenetrated nets in 5 and 6. Phase purity, thermal and luminescence behavior, as well as catalytic activity of the synthesized products were investigated. Particularly, a Zn(II)-based CP 3 acts as an effective and recyclable heterogeneous catalyst for Henry reaction between a model substrate (4-nitrobenzaldehyde) and nitroethane to give ß-nitro alcohol products. For this reaction, various parameters were optimized, followed by the investigation of the substrate scope. By reporting nine new compounds and their structural traits and functional properties, the present work further outspreads a family of CPs constructed from the biphenyl-dicarboxylate H4L1 and H4L2 linkers.

Cobalt(II) Coordination Polymers Assembled from Unexplored Pyridine-Carboxylic Acids: Structural Diversity and Catalytic Oxidation of Alcohols.

New coordination polymers of cobalt(II), namely, [Co(µ4-cpna)(H2O)2] n (1), [Co(µ3-cpna)(phen)(H2O)] n· nH2O (2), [Co3(µ4-dppa)2(H2O)6] n·2 nH2O (3), and [Co3(µ5-dppa)2(µ-4,4'-bipy)(H2O)2] n·4 nH2O (4), have been generated under hydrothermal conditions from CoCl2·6H2O, two different multifunctional pyridine-carboxylic acids {H2cpna: 5-(4-carboxyphenoxy)nicotinic acid; H3dppa: 5-(3,4-dicarboxylphenyl)picolinic acid}, and optional N, N-supporting ligands {phen: 1,10-phenanthroline; 4,4'-bipy: 4,4'-bipyridine} acting as mediators of crystallization. These Co(II) coordination polymers (CPs) have been obtained as stable crystalline materials and characterized by conventional solid-state techniques, including X-ray crystallography. The obtained products are 3D metal-organic frameworks (MOFs 1 and 4) or 2D coordination polymers (CPs 2 and 3). Analysis of the topologies of simplified nets has revealed the sra (1), fes (2), and 3,4L13 (3) networks, in addition to a very complex topologically unique framework in 4. An observed diversity of structures is driven by types of carboxylate building blocks and crystallization mediators. Thermal stability and magnetic and catalytic properties of 1-4 have also been studied. In fact, the Co(II) compounds act as heterogeneous catalysts for the oxidation of alcohols with tBuOOH ( tert-butylhydroperoxide) under mild conditions. Compound 2 features a good catalytic activity (up to 45% yield) in the oxidation of 1-indanol to 1-indanone. Finally, products 1-4 broaden a still very small number of CPs or MOFs driven by the present type of multifunctional pyridine-carboxylic acids (H2cpna, H2dppa).

Metal-Organic Architectures Assembled from Multifunctional Polycarboxylates: Hydrothermal Self-Assembly, Structures, and Catalytic Activity in Alkane Oxidation.

A three-component aqueous reaction system comprising copper(II) acetate (metal node), poly(carboxylic acid) with a phenylpyridine or biphenyl core (main building block), and 1,10-phenanthroline (crystallization mediator) was investigated under hydrothermal conditions. As a result, four new coordination compounds were self-assembled, namely, {[Cu(µ3-cpna)(phen)]·H2O} n (1), {[Cu(µ-Hbtc)(phen)]·H2O} n (2), {[Cu(µ3-Hcpic)(phen)]·2H2O} n (3), and [Cu6(µ-Hcptc)6(phen)6]·6H2O (4), where H2cpna = 5-(2'-carboxylphenyl)nicotinic acid, H3btc = biphenyl-2,4,4'-tricarboxylic acid, H3cpic = 4-(5-carboxypyridin-2-yl)isophthalic acid, H3cptc = 2-(4-carboxypyridin-3-yl)terephthalic acid, and phen = 1,10-phenanthroline. Crystal structures of compounds 1-3 reveal that they are 1D coordination polymers with a ladder, linear, or double-chain structure, while product 4 is a 0D hexanuclear complex. All of the structures are extended further [1D → 2D (1 and 2), 1D → 3D (3), and 0D → 3D (4)] into hydrogen-bonded networks. The type of a multicarboxylate building block has a considerable effect on the final structures of 1-4. The magnetic behavior and thermal stability of 1-4 were also investigated. Besides, these copper(II) derivatives efficiently catalyze the oxidation of cycloalkanes with hydrogen peroxide under mild conditions. The obtained products are the unique examples of copper derivatives that were assembled from H2cpna, H3btc, H3cpic, and H3cptc, thus opening up their use as multicarboxylate ligands toward the design of copper-organic architectures.

New Copper(II) Coordination Compounds Assembled from Multifunctional Pyridine-Carboxylate Blocks: Synthesis, Structures, and Catalytic Activity in Cycloalkane Oxidation.

Two new copper(II) coordination compounds, namely a 1D coordination polymer [Cu(µ-cpna)(phen)(H2O)]n (1) and a discrete tetracopper(II) derivative [Cu(phen)2(H2O)]2[Cu2(µ-Hdppa)2(Hdppa)2] (2), were hydrothermally synthesized from copper(II) chloride as a metal source, 5-(4-carboxyphenoxy)nicotinic acid (H2cpna) or 5-(3,4-dicarboxylphenyl)picolinic acid (H3dppa) as a principal building block, and 1,10-phenanthroline (phen) as a crystallization mediator. Compounds 1 and 2 were isolated as air-stable microcrystalline solids and fully characterized by elemental and thermogravimetric analyses, IR spectroscopy, powder and single-crystal X-ray diffraction. In the solid state, the structure of 1 discloses the linear interdigitated 1D coordination polymer chains with the 2C1 topology. The crystal structure of an ionic derivative 2 shows that the mono- and dicopper(II) units are extended into the intricate 1D hydrogen-bonded chains with the SP 1-periodic net (4,4)(0,2) topology. Thermal stability and catalytic properties of 1 and 2 were also investigated. In fact, both Cu derivatives act as efficient homogeneous catalysts (catalyst precursors) for the mild oxidation of cycloalkanes by hydrogen peroxide to give the corresponding alcohols and ketones; the substrate scope and the effects of type and amount of acid promoter as well as bond-, regio-, and stereo-selectivity features were investigated.

Six metal-organic architectures from a 5-methoxyisophthalate linker: assembly, structural variety and catalytic features.

A methoxy-functionalized isophthalic acid, 5-methoxy isophthalic acid (H2mia), was used a versatile linker for assembling six new metal(ii) compounds under hydrothermal conditions. The obtained products were [Cu2(µ2-mia)2(phen)2(H2O)2]·2H2O (1), [Mn(µ3-mia)(phen)]n (2), [Co(µ2-mia)(2,2'-bipy)(H2O)]n·nH2O (3), [Co(µ3-mia)(µ2-4,4'-bipy)]n·nH2O (4), [Co(µ3-mia)(py)2]n (5), and [Cd(µ2-mia)(py)(H2O)2]n·nH2O (6), where phen(1,10-phenanthroline), 2,2'-bipy(2,2'-bipyridine), 4,4'-bipy(4,4'-bipyridine) or py(pyridine) were incorporated as auxiliary ligands. The crystal structures of 1-6 range from 0D (1) and 1D (2, 3, 5, 6) CPs to a 2D network (4) with a variety of topological types. The catalytic behavior of 1-6 was studied in the cyanosilylation reaction between trimethylsilyl cyanide and aldehydes, resulting in up to 99% yields of products under optimized conditions. Various reaction parameters as well as catalyst recycling and substrate scope were investigated. This study widens the use of H2mia as a versatile dicarboxylate linker for assembling a diversity of functional metal-organic architectures with remarkable structural features and catalytic properties.

Poly[diaqua-bis-(nitrato-κ²O,O')bis-(1,10-phenanthroline-κ²N,N')-µ3-succinato-dicadmium].

In the title coordination polymer, [Cd2(C4H4O4)(NO3)2(C12H8N2)2(H2O)2](n), the Cd(II) ion is seven-coordinated within a distorted penta-gonal-bipyramidal O5N2 environment. The succinate anions, located on an inversion centre, adopt a bis-monodentate bridging mode, leading to the formation of rods along [100]. The rods are connected by O-H⋯O hydrogen bonds between the coordinating water mol-ecules and nitrate O atoms of adjacent rods; the same type of hydrogen bonds are also observed between water and carboxyl-ate O atoms within the rods. π-π stacking inter-actions with a minimum plane-to-plane separation of 3.462 (2) Šoccur between phenanthroline ligands.

N-[2-(2-Hy-droxy-eth-oxy)pheneth-yl]phthalimide.

The title compound, C(18)H(17)NO(4), was obtained accidentally through acid-catalysed aromatization of a phthalimide-substituted 2-(1-hy-droxy-eth-yl)cyclo-hex-2-enone. It exhibits an intra-molecular O-H⋯O(c) (c = carbonyl) hydrogen bond and forms a three-dimensional network structure via π-π stacking inter-actions between adjacent benzene rings (phthalimide-to-phenyl-ene and phthalimide-to-phthalimide), with centroid-centroid distances of 3.8262 (6) and 3.6245 (5) Å.

Poly[diaqua-tris-(µ(4)-1,3-phenyl-ene-diacetato)-dicerium(III)].

In the title coordination polymer, [Ce(2)(C(10)H(8)O(4))(3)(H(2)O)(2)](n), each Ce(III) atom is nine-coordinated by eight O atoms from six different 1,3-phenyl-enediacetate (pda) bivalent anions and one O atom from a coordinated water mol-ecule, forming a distorted tricapped trigonal-prismatic coordination geometry. Eight Ce(III) ions and twelve pda ligands form a large [Ce(8)(pda)(12)] ring, and four Ce(III) ions and six pda ligands form a small [Ce(4)(pda)(6)] ring. The rings are further connected by the coordination inter-actions of pda ligands and Ce(III), generating a three-dimensional supra-molecular framework.

Poly[[triaqua-(µ(3)-4-oxidopyridine-2,6-dicarboxyl-ato)terbium(III)] monohydrate].

In the title coordination polymer, {[Tb(C(7)H(2)NO(5))(H(2)O)(3)]·H(2)O}(n), the Tb(III) atom is eight-coordinated by a tridentate 4-oxidopyridine-2,6-dicarboxyl-ate trianion, two adjacent monodentate anions and three water mol-ecules, forming a distorted bicapped trigonal-prismatic TbNO(7) coordination environment. The anions bridge adjacent Tb(III) ions into double chains. Adjacent chains are further connected into sheets parallel to (10). O-H⋯O hydrogen bonds involving both coordinated and uncoordinated water mol-ecules generate a three-dimensional network.

Di-µ-benzoato-κO,O':O;κO:O,O'-bis-[(benzoato-κO,O')(1,10-phenanthroline-κN,N')lead(II)].

In the centrosymmetric dinuclear title compound, [Pb(2)(C(7)H(5)O(2))(4)(C(12)H(8)N(2))(2)], two Pb(2+) ions are connected by two tridentate bridging benzoate anions. The Pb(2+) ion is seven-coordinated by five O atoms from three benzoate anions and two N atoms from the 1,10-phenanthroline ligands. The benzoate anions adopt two different coordination modes, one bidentate-chelating and one tridentate bridging-chelating. The three-dimensional supra-molecular framework is achieved by inter-molecular π-π stacking inter-actions, with a shortest centroid-centroid distance of 3.617 (4) Å.

Di-µ-benzoato-κO,O':O';κO:O,O'-bis-[(benzoato-κO,O')(1,10-phenanthroline-κN,N')cadmium].

The dinuclear title compound, [Cd(2)(C(7)H(5)O(2))(4)(C(12)H(8)N(2))(2)], lies on a crystallographic twofold axis. The Cd(II) ions are connected by two bridging benzoate anions and each ion is seven-coordinated by five O atoms from three benzoate ligands and by two N atoms from 1,10-phenanthroline. The benzoate ligands adopt two different coordination modes, acting as bidentate and bridging tridentate ligands. The discrete neutral mol-ecules further extend their structure into a three-dimensional supra-molecular framework by inter-molecular π-π [inter-planar distances of 3.392 (4) Å] and C-H⋯π stacking inter-actions [H-mean plane = 2.567 (4) and 2.781 (4) Å].

Poly[diaqua-tris-(µ(4)-1,3-phenyl-enediacetato)-dineodymium(III)].

In the title coordination polymer, [Nd(2)(C(10)H(8)O(4))(3)(H(2)O)(2)](n), each of the two Nd(III) ions is nine-coordinated by eight O atoms from six different 2,2'-(m-phenyl-ene)diacetate (pda) bivalent anions and by one O atom from a water mol-ecule, forming a distorted tricapped trigonal-prismatic coordination geometry. Eight Nd(III) ions and 12 pda ligands form a large [Nd(8)(pda)(12)] ring, and four Nd(III) ions and six pda ligands form a small [Nd(4)(pda)(6)] ring. These rings are further connected by the coordination inter-actions of pda ligands and Nd(III), generating a three-dimensional supra-molecular framework.

Poly[[triaqua-(µ(3)-4-oxidopyridine-2,6-dicarboxyl-ato)holmium(III)] mono-hydrate].

In the title coordination polymer, {[Ho(C(7)H(2)NO(5))(H(2)O)(3)]·H(2)O}(n), the Ho(III) atom is eight-coordinated by a tridentate 4-oxidopyridine-2,6-dicarboxyl-ate trianion, two monodentate anions and three water mol-ecules, forming a distorted bicapped trigonal-prismatic HoNO(7) coordination geometry. The anions bridge adjacent Ho(III) ions into double chains. Adjacent chains are further connected into sheets. O-H⋯O hydrogen bonds involving both coordinated and uncoordinated water mol-ecules generate a three-dimensional supra-molecular framework.

Poly[[triaqua-(µ(3)-4-oxidopyridine-2,6-dicarboxyl-ato)thulium(III)] monohydrate].

In the title coordination polymer, {[Tm(C(7)H(2)NO(5))(H(2)O)(3)]·H(2)O}(n), the Tm(III) atom is eight-coordinated by a tridentate 4-oxidopyridine-2,6-dicarboxyl-ate trianion, two monodentate anions and three water mol-ecules, forming a distorted bicapped trigonal-prismatic TmNO(7) coordination geometry. The anions bridge adjacent Tm(III) ions into double chains. Adjacent chains are further connected into sheets. O-H⋯O hydrogen bonds involving both coordinated and uncoordinated water mol-ecules generate a three-dimensional supra-molecular framework.

Piperazine-1,4-diium bis-(hydrogen 2-propyl-1H-imidazole-4,5-dicarbox-ylate) monohydrate.

The title compound, C(4)H(12)N(2) (2+)·2C(8)H(9)N(2)O(4) (-)·H(2)O, is a hydrated proton-transfer compound obtained from 2-propyl-1H-imidazole-4,5-dicarb-oxy-lic acid and piperazine. The asymmetric unit contains one half-cation, one anion and half a water mol-ecule. There is a centre of inversion at the centre of the cation ring and the water molecule O atom lies on a twofold rotation axis. In the crystal, inter-molecular N-H⋯O and N-H⋯N hydrogen bonds help to construct a three-dimensional framework. Almost symmetrical, intramolecular O-H⋯O inter-actions are also observed.

Triaqua-(1,10-phenanthroline-2,9-dicarboxyl-ato)cobalt(II) dihydrate.

The title compound, [Co(C(14)H(6)N(2)O(4))(H(2)O)(3)]·2H(2)O, has two-fold crystallographic symmetry. The Co(II) atom is in a distorted penta-gonal-bipyramidal coordination environment with two N atoms and two O atoms from a tetradentate 1,10-phenanthroline-2,9-dicarboxyl-ate ligand and one O atom from a water mol-ecule forming the penta-gonal plane, and two O atoms from two water mol-ecules occupying axial positions. In the crystal, adjacent mol-ecules are linked by O-H⋯O hydrogen bonds, forming a three-dimensional network.