Extended metal-organic solids based on benzenepolycarboxylic and aminobenzoic acids

This article describes the recent results obtained in our laboratory on the interaction of polyfunctional ligands with divalent alkaline earth metal ions and a few divalent transition metal ions. Treatment of MC12·nH2O (M = Mg, Ca, Sr or Ba) with 2-amino benzoic acid leads to the formation of complexes [Mg(2-aba)2] (1), [Ca(2-aba)2(OH2)3]∞ (2), [{Sr(2-aba)2(OH2)2}2·H2O)]∞ (3), [Ba(2-aba)2(OH2)]∞ (4), respectively. While the calcium ions in 2 are hepta-coordinated, the strontium and barium ions in 3 and 4 reveal a coordination number of nine apart from additional metal-metal interactions. Apart from the carboxylate functionality, the amino group also binds to the metal centres in the case of strontium and barium complexes 3 and 4. Complexes [{Mg(H2O)6}(4-aba)2·2H2O] (5), [Ca(4-aba)2(H2O)2] (6) prepared from 4-aminobenzoic acid reveal more open or layered structures. Interaction of 2-mercaptobenzoic acid with MCl2·6H2O (M = Mg, Ca), however, leads to the oxidation of the thiol group resulting in the disulphide 2,2' -dithiobis(benzoic acid). New metal-organic framework based hydrogen-bonded porous solids [{M(btec) (OH2)4}n·n(C4H12N2)·4nH2O] (btec = 1,2,4,5-benzene tetracarboxylate) (M = Co9; Ni10; Zn11) have been synthesized from 1,2,4,5-benzene tetracarboxylic acid in the presence of piperazine. These compounds are made up of extensively hydrogen-bonded alternating layers of anionic M-btec co-ordination polymer and piperazinium cations. Compounds 2- 11 described herein form polymeric networks in the solid-state with the aid of different coordinating capabilities of the carboxylate anions hydrogen bonding interactions

Di-tert-butyl phosphate as synthon for metal phosphate materials via single-source coordination polymers [M(dtbP)(2)](n) (M = Mn, Cu) and [Cd(dtbP)(2)(H(2)O)](n) (dtbp-H = (tBuO)(2)P(O)OH)

Reaction of M(OAc)(2).xH(2)O (M = Mn, Cu, or Cd) with di-tert-butyl phosphate (dtbp-H) in a 1:2 molar ratio in methanol followed by slow crystallization of the resultant solid in MeOH/THF medium results in the formation of three new polymeric metal phosphates [M(dtbP)(2)](n) [M = Mn, 1 (beige); M = Cu, 2 (blue)] and [Cd(dtbP)(2)(H(2)O)](n), 3 (colorless)] in good yields. The formation of [Mn(dtbP)21, (1) proceeds via tetrameric manganese phosphate [Mn(4)(O)(dtbP)(6)] (4), which has been isolated in an analytically pure form. Perfectly air- and moisture-stable compounds 1-4 were characterized with the aid of analytical, thermoanalytical, and spectroscopic techniques. The molecular structures of 1-3 were further established by single-crystal X-ray diffraction studies. Crystal data for 1: C(32)H(72)-Mn(2)O(16)P(4), monoclinic, P2(1)/c, a = 19.957(4) Angstrom, b = 13.419(1) Angstrom, c = 18.083(2) Angstrom, beta = 91.25(2)degrees, Z = 4. Crystal data for 2: C(16)H(36)CUO(8)P(2), orthorhombic, Pccn, a = 23.777(2) Angstrom, b = 10.074(1) Angstrom, c = 10.090(1) Angstrom, Z = 4. Crystal data for 3: C(48)H(114)Cd(3)O(27)P(6), triclinic, P (1) over bar, a = 12.689(3) Angstrom, b = 14.364(3) Angstrom, c = 22,491(5) Angstrom, alpha = 84.54(3)degrees, beta = 79.43(3)degrees, gamma = 70.03(3)degrees, Z = 2. The diffraction studies reveal three different structural forms for the three compounds investigated, each possessing a one-dimensional coordination polymeric structure. While alternating triple and single dtbp bridges are found between the adjacent Mn(2+) ions in 1, uniform double dtbp bridges across the adjacent Cu(2+) ions are present in 2. The cadmium ions in the structure of 3 are pentacoordinated. Thermal analysis (TGA and DSC) indicates that compounds 1-3 convert to the corresponding crystalline metaphosphate materials M(PO(3))(2), in each case at temperatures below 500 degreesC. Similarly, the thermal decomposition of 4 results in the formation of Mn(PO(3))(3) and Mn(2)P(2)O(7). The final materials obtained by independent thermal decomposition of bulk samples have been characterized using I R spectroscopic, powder diffraction, and N(2) adsorption studies

Di-tert-butylphosphate complexes of Mn(II) and Cu(II) as single-source precursors for metal phosphate materials

Octahedral Mn(II) and Cu(II) di-tert-butylphosphate (L) complexes [ML2(imz)(4)] have been synthesized and characterized using IR, UV-vis, luminescence, and EPR spectroscopy and single crystal X-ray diffraction studies. Thermal decomposition of both the complexes (probed by TGA, DTA, and DSC) indicate stepwise elimination of iso-butene. imidazole and water to finally yield the respective ceramic materials Mn(PO3)(2) or Cu(PO3)(2)

Anionic metal-organic and cationic organic layer alternation in the coordination polymers [{M(BTEC)(OH2)(4)}center dot{C4H12N2}center dot 4H(2)O](n) (M = Co, Ni, and Zn; BTEC=1,2,4,5-benzenetetracarboxylate)

New coordination polymers[{M(BTEC)(OH2)(4)vertical bar.vertical barC(4)H(12)N(2)}.4H(2)O](n)(BTEC= 1,2,4,5-benzenetetracarboxylate) (M = Co 1: Ni 2: Zn 3) have been synthesized starting from the respective transition metal salts, 1,2,4,5-benzenetetracarboxylic acid and piperazine hexahydrate. The highly-crystalline compounds, which are insoluble in water as well as common organic solvents. have been characterized in the solid-state with the aid of elemental analysis. IR and diffuse reflectance UV-visible spectroscopy, and TGA/DTA measurements. The molecular structures of all the compounds have been determined in the solid-state by X-ray diffraction studies; all the three compounds are isomorphous and crystallize in centerosymmetric triclinic space group. The molecular structures are made up of extensively hydrogen-bonded alternating layers of anionic {M(BTEC)(OH2)(4)}(n) coordination polymer and piperazinium dications. The extended structure formed in the solid-state due to extensive inter-layer O-H...O and N-H...O hydrogen bonds incorporate four water molecules per unit cell. The water molecules present in the polymeric network can be easily removed at fairly low temperatures. Heating 1 or 2 to approximately 60-70degreesC in a vacuum (0.1 mmHg) for 12 h results in the elimination of three water molecules as evidenced by elemental analysis. Similar results were obtained from the thermogravimetric studies. The dehydration process is accompanied by a colour change in the case of compounds 1 and 2. Exposure of the dehydrated sample to ammonia results in the uptake of three equivalents of ammonia molecules. However. the methane gas adsorption studies carried out on dehydrated sample did not show the presence of a porous structure

Di-tert-butyl phosphate complexes of cobalt(II) and zinc(II) as precursors for ceramic M(PO(3))(2) and M(2)P(2)O(7) materials: Synthesis, spectral characterization, structural studies, and role of auxiliary ligands

Reaction of the metal acetates M(OAc)(2). xH(2)O with di-tert-butyl phosphate (dtbp-H) (3) in a 4:6 molar ratio in methanol or tetrahydrofuran followed by slow evaporation of the solvent results in the formation of metal phosphate clusters [M(4)(mu (4)-O)(dtbp)(6)] (M = Co (4, blue); Zn (5, colorless)) in nearly quantitative yields. The same reaction, when carried out in the presence of a donor auxiliary ligand such as imidazole (imz) and ethylenediamine (en), results in the formation of octahedral complexes [M(dtbp)(2)(imz)(4)] (M = Co (6); Ni (7); Zn (8)) and [Co(dtbp)(2)-(en)(2)] (9). The tetrameric clusters 4 and 5 could also be converted into mononuclear 6 and 8, respectively, by treating them with a large excess of imidazole. The use of slightly bulkier auxiliary ligand 3,5-dimethylpyrazole (3,5-dmp) in the reaction between cobalt acetate and 3 results in the isolation of mononuclear tetrahedral complex [Co(dtbp)(2)(3,5-dmp)(2)] (10) in nearly quantitative yields. Perfectly air- and moisture-stable samples of 4-10 were characterized with the aid of analytical, thermoanalytical, and spectroscopic techniques. The molecular structures of the monomeric pale-pink compound 6, colorless 8, and deep-blue 10 were further established by single-crystal X-ray diffraction studies. Crystal data for 6: C(28)H(52)CoN(8)O(8)P(2), a = 8.525(1) Angstrom, b = 9.331(3) Angstrom, c = 12.697(2) Angstrom, alpha = 86.40(2)degrees, beta = 88.12(3)degrees, gamma = 67.12(2)degrees, triclinic, P (1) over bar, Z = 1. Crystal data for 8: C(28)H(52)N(8)O(8)P(2)Zn, a = 8.488(1) Angstrom, b = 9.333(1) Angstrom, c = 12.723(2) Angstrom, alpha = 86.55(1)degrees, beta = 88.04(1)degrees, gamma = 67.42(1)degrees, triclinic, P (1) over bar, Z = 1. Crystal data for 10: C(26)H(52)CON(4)O(8)P(2), a = b = 18.114(1) Angstrom, c = 10.862(1) Angstrom, tetragonal, P4(1), Z = 4. The Co(2+) ion in 6 is octahedrally coordinated by four imidazole nitrogens which occupy the equatorial positions and oxygens of two phosphate anions on the axial coordination sites. The zinc derivative 8 is isostructural to the cobalt derivative 6. The crystal structure of 10 reveals that the central cobalt atom is tetrahedrally coordinated by two phosphate and two 3,5-dmp ligands. In all structurally characterized monomeric compounds (6, 8, and 10), the dtbp ligand acts as a monodentate, terminal ligand with free P=O phosphoryl groups. Thermal studies indicate that heating the samples at 171 (for 4) or 93 degreesC (for 5) leads to the loss of twelve equivalents of isobutene gas yielding carbon-free [M(4)(mu (4)-O)(O(2)P(OH)(2))(6)], which undergoes further condensation by water elimination to yield a material of the composition Co(4)O(19)P(6) This sample of 4 when heated above 500 degreesC contains the crystalline metaphosphate Co(PO(3))(2) along with amorphous pyrophosphate M(2)P(2)O(7) in a 2:1 ratio. Similar heat treatment on samples 6-8 results in the exclusive formation of the respective metaphosphates Co(PO(3))(2), Ni(PO(3))(2), and Zn(PO(3))(2); the tetrahedral derivative 10 also cleanly converts into Co(PO(3))(2) On heating above 600 degreesC

Cobalt and manganese nets via their wires: Facile transformation in metal-diorganophosphates

The manganese and cobalt complexes [M(dtbP)(2)](n) (M = Mn, Co; dtbp = di-tert-butyl phosphate), which exist as one-dimensional molecular wires, transform to [M(dtbP)(2)(bpy)(2)(.)2H(2)O](n) by the addition of 4,4-bipyridine (bpy) at room temperature; the latter compounds form noninterpenetrating rectangular grid structures

Copper phosphates and phosphinates with pyridine/pyrazole alcohol co-ligands: Synthesis and structure

Copper phosphates, [Cu(dtbp)(2)(pzet)(2)]center dot H(2)O (1) and [Cu(dtbp)(2)(pyme)(2)] (2), as well as copper phosphinate, [Cu(dppi)(2)(pyet)(2)] (3) have been synthesized by the reaction of copper acetate with di-tert-butyl phosphate (dtbp) or diphenyl phosphinate (dppi) in the presence of pyridine base having hydroxyl group, namely, 3,5-dimethylpyrazole-2-ethanol (pzet) or 2-(hydroxymethyl) pyridine (pyme) or 2-(2-hydroxyethyl) pyridine (pyet). Single crystal X-ray diffraction studies reveal that copper ion in all the three complexes is bonded to two phosphoryl ions (P(O)O ) and two pyridine co-ligands. The crystal structure of 1 reveals that the hydroxyl group of the CH(2)CH(2)OH moiety of pzet ligand exhibits a positional disorder between the non-bonding position and the bonding position with respect to the central copper ion along the Jahn-Teller axis. Hence, the structure of 1 can be considered to exhibit both 'square-planar' and 'octahedral' coordination geometries simultaneously for the copper ion in the same complex. A similar situation for the -OH groups has not been observed in the complexes 2 and 3 and hence the coordination geometry around the copper ion is axially elongated octahedron. (C) 2011 Elsevier B.V. All rights reserved

Non-interpenetrating transition metal diorganophosphate 2-dimensional rectangular grids from their 1-dimensional wires: structural, transformations under mild conditions

The manganese, cobalt, and cadmium complexes [M(dtbP)(2)](n) (M = Mn (1) and Cc (2)) and [Cd(dtbP)(2)(H2O)](n), (3) (dtbp = di-tert-butyl phosphate), which exist as one-dimensional molecular wires, transform to non-interpenetrating rectangular grids [M(dtbP)(2)(bPY)(2)(.)2H(2)O](n) (M = Mn (4), Co (5), and Cd (6)) by the addition of 4,4-bipyridine (bpy) at room temperature. Products 4-6 have also been prepared by a room-temperature reaction or by solvothermal synthesis in methanol through a direct reaction between the metal acetate, di-tert-butyl phosphate, and 4,4 '-bipyridine (bpy) in a 1:22 molar ratio. Single-crystal X-ray structure determination of 4-6 shows that these compounds are composed of octahedral transition metal ions woven into a two-dimensional grid structure with the help of bpy spacer ligands. The axial coordination sites at the metal are occupied by bulky unidentate dtbp ligands, which prevent any interpenetration of the individual grids. The change of reaction conditions from solvothermal to hydrothermal, for the attempted synthesis of a magnesium grid structure, however leads to the isolation of an organic phosphate [(H(2)bpy)(H2PO4)(2)] (7) and an inorganic phosphate [Mg(HPO4)(OH2)(3)] (8). Compound 7 can also be prepared quantitatively from a direct reaction between bpy and H3PO4. The new organic phosphate 7 is a unique example of a phosphate material with alternating layers of [H(2)bpy](2+) cations and [H2PO4](2+) anions that are held together by hydrogen bonds. Solid-state thermal decomposition of 4-6 produced the respective metaphosphate materials [M(PO3)(2)] (M = Mn (9), Cc (10), and Cd (11)). All new metal-organic phosphates have been characterized by elemental analysis, thermal analysis (TGA, DTA, DSC), and IR and NMR spectroscopy. The metaphosphate ceramic materials were characterized by IR spectral and powder X-ray diffraction studies

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Not AvailableMicrowave irradiation of 2-hydroxy chalcones under solvent-free conditions resulted in a ‘‘green-chemistry’’ procedure for the preparation of flavanones in good yields, using an unmodified household microwave oven and silica as solid support. By irradiation of 2-hydroxy chalcones with trifluoroacetic acid over silica gel, 11 known flavanones were prepared in high yields. The synthesised compounds were characterised using spectroscopic techniques, namely, 1H NMR, 13C NMR and IR, and screened for their antifungal activity in vitro against Sclerotium rolfsii and Rhizoctonia solani by poisoned food technique. The compounds tested were found to be more active against R. solani, whereas against S. rolfsii, moderate activity was observed, as evident from LC50 values. The most potent compound 2-(4-fluorophenyl)-2,3-dihydrochromen-4-one (4a) had LC50 value of 12.0 mg L71 followed by 11, 11a, 3a, 9a, 8a, 10a and 10 having LC50 values 18.21, 18.3, 32.9, 50.7, 88.8, 118.8 and 119.7 mg L71, respectively.Not Availabl