Coordination polymers: structural transformation from two to three dimensions through ligand conformation change

M, Rawat P, Singh RN, Shahid M, Trivedi S, Gautam A, Zeeshan M. A new Zn(ii) MOF assembled from metal–organic cubes (MOCs) as a highly efficient adsorbent for cationic dyes

A new MOC [Zn₃(Tz)₂(tpa)₂(DMSO)₄] was synthesized. The cluster representation reveals an interwoven pcu 6/4/c1 sqc1 topological type. The MOC exhibits excellent water stability, recyclability, adsorption and separation abilities toward selected dyes.

A manganese-salen complex as dipeptidyl peptidase IV inhibitor for the treatment of type 2 diabetes

A manganese Schiff base complex with N,N'-1,2-phenylenediamine-bis(salicyladimine) was synthesized and characterized by X-ray crystallography. This complex was administered intragastrically to alloxan-diabetic mice 3 weeks. In vivo tests showed that the complex significantly lowered serum glucose levels in alloxan-diabetic mice at doses of 77 mg V kg^-1. Meanwhile, this complex was investigated as dipeptidyl peptidase IV (DPP-IV) inhibitor for the treatment of type 2 diabetes. The compound exhibit moderate inhibition against DPP-IV and possessed an IC₅₀ value of 30 μM. Lineweaver-Burk transformation of the inhibition kinetics data demonstrated that it was a noncompetitive inhibitor of DPP-IV and Ki value was 136.3 μM. Moreover, molecular modeling studies suggested that the complex could fit well within the active-site cleft of DPP-IV. An acute toxicity study showed that animals treated intragastically with complex 1 at a dose of 5.0 g/kg did not show any significantly abnormal signs. These preliminary results suggest that the manganese Schiff base complex can induce a hypoglycemic effect in alloxan-diabetic mice.

A two-dimensional manganese(II) complex: poly[bis(μ2-4,4′-bipyridyl)tetrakis(μ2-3,5-dinitrobenzoato)dimanganese(II)]

The Mn atom in the title compound, [Mn₂(C₇H₃N₂O₆)₄(C₁₀H₈N₂)₂]_n, is six-coordinated by two N atoms and four O atoms, forming a distorted octa­hedral geometry. The Mn—O bond lengths are in the range 2.1281 (13)–2.2011 (12) Å and the Mn—N bond lengths are 2.269 (2) and 2.278 (2) Å. Mn(II) atoms are double-bridged along the a axis by two pairs of bi-monodentate carboxyl groups, forming a double-stranded chain, while the bidentate 4,4′-bipyridine ligand bridges the Mn atom along the b axis. This results in a two-dimensional structure constructed of oblong grids with the sides of length 11.634 and 5.075 Å

The Thermal Decomposition Kinetics of [Co(bipy)(H2O)4](C4H4O4)·4H2O

The thermal decomposition kinetics of [Co(bipy)(H2O)4](C4H4O4) · 4H2O was carried out by thermogravimetry (TG) and derivate thermogravimetry (DTG) analysis at four heating rates of 5, 8, 11 and 14 °C/min in nitrogen atmosphere. TG confirmed that thermal decomposition of the compound takes place in a single step. The kinetic parameters (activation energy, frequency factor, and activation entropy) were calculated using various forms of non-isothermal methods. The activation energy obtained by the Ozawa method is in agreement with the value determined by the Coats–Redfern technique. However, a much lower activation energy was obtained by the Kissinger method.

Assembly of Heterometallic Clusters and Coordination Polymers by Combining Mo−S-Based Clusters with Mn2+

Addition of [Mo(V)2O2S2(edt)2]2- (edt =1,2-ethanedithiolate) to acetonitrile and/or methanol solutions of MnII containing bipyridines [4,4'-trimethylenedipyridine (TDP), 4,4'-bipyridine (4,4'-bpy), 2,2'-bipyridine (2,2'-bpy)] or 15-crown-5 produces three new heterometallic cluster coordination polymers, [Mn2[Mo2O2S2(edt)2]2(TDP)3(CH3OH)2(NCMe)2].3CH3OH.0.25MeCN (1), [Mn(TDP)2(H2O)2]2+[Mn[Mo2O2S2(edt)2)2(TDP)2]]2-.6CH3OH (2), [Mn[Mo2O2S2(edt)2](TDP)2(CH3OH)(H2O)].CH3OH (3), and three new multinuclear clusters, [Mn[Mo2O2S2(edt)2](4,4'-bpy)(CH3OH)4].0.5(4,4'-bpy) (4), [Mn[Mo2O2S2(edt)2](2,2'-bpy)2].2CH3OH (5), and (NEt4)2[Mn(15-crown-5)[Mo2O2S2(edt)2]2] (6). All compounds were characterized by X-ray crystallography. The coordination mode of Mn in these compounds depends on the ligands and the crystallization conditions. Compound 2 readily converts to 1 or 3 depending on the reaction and solvent conditions. Compounds 1 and 2 were analyzed using thermogravimetric analysis combined with mass spectroscopy (TG-MS) in the temperature range 25-500 degrees C. The room-temperature magnetic moments for compounds 1-6 were determined.

3D Coordination Polymers with Nitrilotriacetic and 4,4‘-Bipyridyl Mixed Ligands: Structural Variation Based on Dinuclear or Tetranuclear Subunits Assisted by Na−O and/or O−H···O Interactions

The reactions of Cu(II) with the mixed nitrilotriacetic acid (H3NTA) and 4,4'-bipyridyl (4,4'-bpy) ligands in different metal-to-ligand ratios in the presence of NaOH and NaClO4 afforded two complexes, Na3[Cu2(NTA)2(4,4'-bpy)]ClO4 x 5H2O (1) and [Cu2(NTA) (4,4'-bpy)2]ClO4 x 4H2O (2). The two complexes have been characterized by elemental analysis, IR, XRD, and single-crystal X-ray diffraction. 1 contains a basic doubly negatively charged [Cu2(NTA)2(4,4'-bpy)]2- dinuclear unit which was further assembled via multiple Na-O and O-H...O interactions into a three-dimensional (3D) pillared-layer structure. 2 features a two-dimensional (2D) undulated brick-wall architecture containing a basic doubly positively charged [Cu4(NTA)2(4,4'-bpy)2]2+ tetranuclear unit. The 2D network possesses large cavities hosting guest molecules and was further assembled via O-H...O hydrogen bonds into a 3D structure with several channels running in different directions.

Magneto-structural xorrelations in 2D and 3D extended structures of manganese(II)-malonate systems

Two polymeric malonato-bridged manganese(II) complexes of formula [Mn(mal)(H(2)O)(2)](n)() (1) and [Mn(2)(mal)(2)(4,4'-bipy)(H(2)O)(2)](n)() (2) have been synthesized and characterized (mal = malonate dianion; 4,4'-bipy = 4,4'-bipyridine). The crystal structure of complex 1 was already known. Complex 2 crystallizes in monoclinic space group P2(1)/n, Z = 2, with unit cell parameters of a = 7.2974(10) A, b = 18.7715(10) A, c = 7.514(3) A, and beta = 91.743(12) degrees. The structure determination reveals that the complex [Mn(2)(mal)(2)(4,4'-bipy)(H(2)O)(2)](n)() (2) is a 3D network being composed of Mn-malonate sheets which are pillared by bidentate 4,4'-bipy spacer forming small voids. The Mn-Mn distances through Mn-mu-(O3-C8-O4)-Mn, Mn-mu(O1-C6-O2)-Mn, and Mn-mu-4,4'-bipy-Mn bridges are 5.561, 5.410, and 11.723 A, respectively. The magnetic behaviors of complexes 1 and 2 in the temperature range 300-2 K are very close, corresponding to a weak antiferromagnetic coupling. The magnetic pathways of complex 1 are through two Mn-O-C-O-Mn with anti-anti conformation and two Mn-O-C-O-Mn with syn-anti conformations and in complex 2 through all Mn-O-C-O-Mn with syn-anti conformations. Both syn-anti and anti-anti conformations create weak antiferromagnetic coupling, and the susceptibility data are fitted by the expansion series of Lines and the Curély formula for an S = 5/2 antiferromagnetic quadratic layer, based on the exchange Hamiltonian H = -Sigma(nn)()JS(i)()S(j)(). The best fit is given by the superexchange parameters J = -0.32 cm(-)(1) and g = 2.00 for complex 1 and J = -0.14 cm(-)(1), J(inter) = -0.031 cm(-)(1), and g = 2.00 for complex 2. Finally, in both the complexes there is a magnetic pathway Mn-O-C-C-C-O-Mn, and this pathway through the three carbon atoms of the malonato-bridging ligand could be considered negligible.