DMF Solvent Molecules Research Articles

Solvent-rich layered cobalt(II) 1,4-benzenedicarboxylate based on binuclear {Co2(μ-OH2)(RCOO)2} secondary building unit

The reaction of a ditopic ligand, 1,4-benzenedicarboxylic acid (H2bdc) with Co(CH3COO)2·4H2O in solution resulted in a solvent-rich layered coordination polymer with the composition {[Co2(μ2-OH2)(bdc)2(dmf)2(H2O)2]·(dmf)·3(H2O)}n (1) whose crystal structure was determined by single crystal X-ray diffraction. The compound is built on the binuclear {Co2(μ2-OH2)(COO)2} metal clusters, where each Co(II) atom is coordinated by six oxygen atoms in a distorted octahedral arrangement. The crystal lattice of 1 hosts the dmf and water solvent molecules via the OH⋯O hydrogen bonding with coordination network. The easy destruction of the crystals due to the partial solvent loss occurs rapidly in ambient conditions and is confirmed by the TGA data.

Tetragonal versus Hexagonal: Structure-Dependent Catalytic Activity of Co/Zn Bimetallic Metal-Organic Frameworks.

Tetragonal and hexagonal phases of monometallic Zn and bimetallic Co/Zn metal-organic frameworks (MOFs), with secondary building units (SBUs) containing a M3O (M = metal) cluster, were synthesized from identical constituents using a benzenetricarboxylate (BTC(3-)) linker that forms decorated 3,6- and 3,5-connected networks, respectively. There exist subtle differences between the SBUs; one of the metal atoms in the M3O cluster in the tetragonal phase has one dissociable DMF solvent molecule while that in the hexagonal phase has three. Connectivities between the SBUs form one-dimensional channels in both MOFs. These MOFs catalyze the chemoselective addition of amines to epoxides, giving exclusively β-hydroxyamine under heterogeneous conditions. A ring-opening reaction of a symmetrical epoxide showed that the hexagonal phase diastereoselectively yields trans-alcohol, exhibiting an exquisite model for structure-dependent activity.

Syntheses, Characterization, and Luminescence Properties of Four Metal–Organic Frameworks Based on a Linear-Shaped Rigid Pyridine Ligand

Solvothermal syntheses in DMF (or DMA) and H2O afforded four novel metal–organic frameworks: {[Cd(DPBT) (BDC)]·2(H2O)}n (1), {[Zn2(DPBT)2(IPA)2]·2(DMA)}n (2), {[Co2(DPBT)2(BDC)2]·2(DMF)·5(H2O)}n (3), and {[Ni(DPBT)2(H2O)4]·(BDC)}n (4) (DPBT = 4,7-di(4-pyridyl)-2,1,3-benzothiadiazole, BDC = 1,4-benzene dicarboxylate, IPA = isophthalic acid, DMA = N,N-dimethylacetamide, and DMF = N,N-dimethylformamide). X-ray analyses show that 1 and 3 show similar structures with the same building blocks and possess 3-dimensional 6-connected pcu net. Compounds 1 and 3 are based on a 2-fold interpenetrating network with solvent molecules located in the framework, whereas 3 is different in the absence of DMF solvent molecules. Compared with compounds 1 and 3, 4 is constructed under the same conditions except with metal ions and possesses a completely different structure type. Luminescence properties of 1 and 2 without any activation well-dispersed in common solvents have also been investigated systematically; the luminescenc...

Self-Assembled Pyridine-Dipyrrolate Cages.

An inherently nonlinear pyridine dipyrrolate ligand, namely 2,6-bis(3,4-diethyl-5-carboxy-1H-pyrrol-2yl)pyridine (compound 1), is able to distinguish between different zinc(II) cation sources, namely Zn(acac)2 and Zn(OAc)2, respectively. This differentiation is manifest both in terms of the observed fluorescent behavior in mixed organic media and the reaction chemistry. Treatment of 1 with Zn(acac)2 gives rise to a cage dimer, cage-1, wherein two molecules of compound 1 act as double bridging units to connect two individual cage subunits. As inferred from X-ray crystallographic studies, this cage system consists of discrete zinc dimers with hydroxide bridges that, with the assistance of bound DMF solvent molecules, serve to fix the geometry and orientation of the pyridine dipyrrolate building blocks. When a different zinc source, Zn(OAc)2, is used to carry out an ostensibly similar complexation reaction with compound 1, an acetate-bridged 1D abacus-like cage polymer is obtained as inferred from X-ray diffraction analysis. This extended solid state structure, cage-2, contains individual zinc dimer cage submits and appears stabilized by solvent molecules (DMF) and the counteranion (acetate). Rod-like assemblies are also observed by DLS and SEM. This construct, in contrast to cage-1, proved fluorescent in mixed organic media. The structure of the ligand itself (i.e., in the absence of Zn(II)) was confirmed by X-ray crystallographic analysis and was found to assemble into a supramolecular polymer. Conversion to a dimer form was seen upon the addition of TBAOAc. On the basis of the metric parameters, the structures seen in the solid state are stabilized via hydrogen bonding interactions involving solvent molecules.

A 2D Semiquinone Radical-Containing Microporous Magnet with Solvent-Induced Switching from Tc = 26 to 80 K.

The incorporation of tetraoxolene radical bridging ligands into a microporous magnetic solid is demonstrated. Metalation of the redox-active bridging ligand 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (LH2) with Fe(II) affords the solid (Me2NH2)2[Fe2L3]·2H2O·6DMF. Analysis of X-ray diffraction, Raman spectra, and Mössbauer spectra confirm the presence of Fe(III) centers with mixed-valence ligands of the form (L3)(8-) that result from a spontaneous electron transfer from Fe(II) to L(2-). Upon removal of DMF and H2O solvent molecules, the compound undergoes a slight structural distortion to give the desolvated phase (Me2NH2)2[Fe2L3], and a fit to N2 adsorption data of this activated compound gives a BET surface area of 885(105) m(2)/g. Dc magnetic susceptibility measurements reveal a spontaneous magnetization below 80 and 26 K for the solvated and the activated solids, respectively, with magnetic hysteresis up to 60 and 20 K. These results highlight the ability of redox-active tetraoxolene ligands to support the formation of a microporous magnet and provide the first example of a structurally characterized extended solid that contains tetraoxolene radical ligands.

Synthesis and supramolecular features of hybrid POM/onium solid-state assemblies

Polyoxomolybdate-based organic−inorganic hybrid architectures were synthesised and characterised by X-ray crystallography. The supramolecular assemblies present rows of metallic clusters H-bonded by ammonium cations, with a 1:2 molybdate/ammonium ratio. The organic moieties of the ammonium cations establish hydrophobic contact among them such as van der Waals, C–H⋯π and π⋯π interactions that stabilise the supramolecular architectures. In particular, for compound 5 the n-alkyl tails pack closely together giving a lipid-like bilayer. In compound 6, the aromatic phenyl rings of the organic cation allow the stabilisation of the supramolecular architecture by C–H⋯π and π⋯π interactions. Regarding the X-ray structure of the compound 11, the tetraanionic octa-molybdate [Mo8O26]4− cluster is surrounded by four ethyl-triphenyl-phosphonium cations. Running along the b-axis open channels are occupied by DMF solvent molecules. Interestingly, a soaking experiment in n-pentane with the corresponding crystals of compound 11 afforded to a crystal structure very different from the native one.

Spin Crossover, Reversible Redox, and Supramolecular Interactions in 3d Complexes of 4-(4-Pyridyl)-2,5-dipyrazyl-pyridine.

A new terpyridine-inspired terdentate ligand, 4-(4-pyridyl)-2,5-dipyrazyl-pyridine (py-pzpypz), featuring three "spare" nitrogen donors "out the back", has been used to synthesize five bis-ligand complexes, [M(II)(py-pzpypz)2]X2, where M = Mn with X = ClO4, or M = Fe, Co, Ni, and Zn with X = BF4. In contrast, when M = Cu(II), regardless of the M:L ratio employed, 1:1 M:L products were obtained: for X = BF4 a 1D chain {[Cu(II)(py-pzpypz)(DMF)2](BF4)2}n, and for X = Cl a monometallic complex [Cu(py-pzpypz)Cl2]. All seven complexes were structurally characterized, confirming the expected N6 coordination of the M(II) centers in all cases except Cu(II). Notably, a Jahn-Teller elongation is observed in the Co(II) complex, consistent with it being low spin at 100 K. The Cu(II) 1D chain complex has an N4O2 coordination sphere as in this case the "spare" pyridine donor out the back of the py-pzpypz ligand bridges to the next Cu(II) center in the chain, hence providing both a terdentate site and a monodentate pyridine to the next Cu(II) center, and the coordination sphere is completed by weak axial coordination by two DMF solvent molecules. The Cu(II) center in the monometallic complex has an N3Cl2 square pyramidal coordination sphere. In all cases, the noncoordinating, "spare", pyrazine nitrogen atoms are involved in interesting intermolecular interactions, including NPz-π interactions and nonclassical C-H···NPz hydrogen bonding. The Fe(II) complex is low spin as expected. Two polymorphs of the Co(II) complex were obtained, both of which showed gradual spin crossover, with a room temperature T1/2. Two reversible redox processes are observed for [Co(II)(py-pzpypz)2](BF4)2, with Em(M(I)/M(II)) = -0.63 V and Em(M(II)/M(III)) = +0.37 V, and a quasireversible redox process for [Fe(II)(py-pzpypz)2](BF4)2, with Em(M(II)/M(III)) = +1.26 V, versus 0.01 M AgNO3/Ag in MeCN. These potentials are shifted to significantly higher potentials (by ∼0.45 V) than the literature values for the corresponding Fe(II) and Co(II) complexes of the equivalent all-pyridine ligand, consistent with replacement of the two pyridine rings by two pyrazine rings significantly stabilizing the lower oxidation states.

Synthesis, Structure and Photoluminescence of Lanthanide Metal‐Organic Frameworks, Ln4(TDC)6(DMF)4(H2O)2, where TDC2− = thiophene‐2,5‐dicarboxylate, DMF = N,N‐dimethylformamide

AbstractA series of lanthanide metal‐organic frameworks, Ln4(TDC)6(DMF)4(H2O)2, where Ln = Nd (1), Sm (2), Eu (3), Gd (4), TDC2− = thiophene‐2,5‐dicarboxylate, have been synthesized at 80 °C in mixed H2O/DMF. Structural characterizations by single‐crystal X‐ray crystallography reveal that 1∼4 are isomorphous and adopt three‐dimensional frameworks which are constructed by cross‐linking Ln3+ ions with thiophene‐2,5‐dicarboxylates as bridging ligands. These frameworks feature rhomboidal channels, inside which coordinated DMF solvent molecules are located. Thermogravimetric analyses suggest solvent molecules can be removed at about ca. 340 °C. Photoluminescence studies indicate TDC2− ligand shows excellent antenna effect for the europium(III) MOF (3), which exhibits intense characteristic europium(III) emissions upon excitation at μex = 306 nm.

8-Chloro-6-iodo-2-phenylchromeno[4,3-c]pyrazol-4(2H)-oneN,N-dimethylformamide monosolvate

In the title compound, C16H8ClIN2O2·C3H7NO, the fused tricyclic pyrazolo­coumarin ring and the N-phenyl ring are almost coplanar, the dihedral angle between them being 1.86 (9)°. In the crystal, these rings stack on top of each other via π–π inter­actions [centroid–centroid distances = 3.489 (2), 3.637 (2), 3.505 (2) and 3.662 (2) Å], forming infinite chains along the a axis. The chains are connected into layers parallel to ac plane through I⋯O inter­actions [3.0011 (18) Å] between pairs of symmetry-related mol­ecules. The DMF solvent mol­ecules are C—H⋯O bonded to this network.

μ-Oxalato-bis[(2,2′-bipyridyl)copper(II)] bis(perchlorate) dimethylformamide disolvate monohydrate

The title compound, [Cu2(C2O4)(C10H8N2)4](ClO4)2·2C3H7NO·H2O, contains doubly charged centrosymmetric dinuclear oxalato-bridged copper(II) complex cations, perchlorate anions, and DMF and water solvate mol­ecules. In the complex cation, the oxalate ligand is coordinated in a bis-bidentate bridging mode to the Cu atoms. Each Cu atom has a distorted tetra­gonal-bipyramidal environment, being coordinated by two N atoms of the two chelating bipy ligands and two O atoms of the doubly deprotonated oxalate anion. Pairs of perchlorate anions and water mol­ecules are linked into recta­ngles by O—H⋯O bonds in which the perchlorate O atoms act as acceptors and the water mol­ecules as donors. Methyl groups of the DMF solvent molecule are disordered over two sites with occupancies of 0.453 (7):0.547 (7), and the water molecule is half-occupied.

Coordination steric effect of N, N-dimethylformamide, N, N-dimethylacetamide and N-methyl-2-pyrrolidone on the assembly of coordination polymers

Three coordination polymers 1, 2 and 3 have been synthesized in DMF ( N, N-dimethylformamide), DMA ( N, N-dimethylacetamide) and NMP ( N-methyl-2-pyrrolidone), respectively. In 1, DMF solvent molecule coordinates to zinc ion as an ancillary ligand, and 1D chain structure is obtained. 2 and 3 are isostructural, in which solvent molecules, DMA and NMP, do not coordinate to zinc ions, and 1D double stranded chain structures are formed. The coordination steric hindrance of the solvents is suggested as the decisive factor of the assemblies. Crystallography and thermoanalysis reveal that 2 and 3 are more stable and also include more guest solvent molecules than 1.

(E)-1-(3-Cyano-benzyl-idene)thio-semi-carbazide N,N-dimethyl-formamide solvate.

The title compound, C9H8N4S·C3H7NO, adopts an E configuration about both the C=N and C—N bonds. Inter­molecular N—H⋯O hydrogen bonding links the compound to the DMF solvent molecule. The crystal packing is characterized by chains of mol­ecules linked by inter­molecular N—H⋯S hydrogen-bonding inter­actions.

An Interdigitated Metalloporphyrin Framework: Two-Dimensional Tessellation, Framework Flexibility, and Selective Guest Accommodation

A novel porphyrin-based metal−organic framework (MPF-3) was synthesized by the solvothermal reaction of Zn(NO3)2·6H2O and meso-tetra(3-pyridyl)porphine in N,N-dimethylformamide (DMF). Its structure was characterized by single crystal X-ray diffraction and found to be a two-dimensional (2D) interdigitated framework in which DMF solvent molecules reside between the interdigitated layers. The observed 2D topology can be related to the Cairo pentagonal tessellation. X-ray powder diffraction reveals that MPF-3 undergoes a phase transformation when the solvent molecules are removed by heating. Surprisingly, the original topologies are restored when the desolvated phase is immersed in DMF, thereby demonstrating the flexibility of the framework.

In situ synthesis of (5-phenyl-1H-pyrazole-3-carboxylic acid) metal complexes and their stable supramolecular microporous frameworks

By in situ generation of ppc ligand in the presence MCl 2 and 3-phenyl-1H-pyrazole-5-carbohydrazide at room temperature, the complexes, [M(ppc) 2(DMF) 2]·2H 2O (M = Co ( 1) and Ni ( 2); ppc = 5-phenyl-1H-pyrazole-3-carboxylic acid), were synthesized and characterized by single-crystal X-ray diffraction, IR spectrum, UV spectra and elemental analysis. X-ray structural analysis revealed that the complexes were formed into 3D supramolecular polymers via C–H⋯O and π⋯π interactions. The 3D supramolecular networks of two complexes were constructed from 1D nanochannels along the c-direction with the disorder DMF and water solvent molecules shuttling easily. TG and powder X-ray diffraction analysis showed two complexes had high stability when DMF and H 2O molecules were removed. Upon DMF molecules liberated, two complexes become stable microporous solid with coordination-unsaturated [M(ppc) 2] as center. The electrochemical properties were also investigated.

Bis{benzylN′-[(1H-indol-3-yl)methylene]dithiocarbazato-κ2N′,S}copper(II)N,N-dimethylformamide disolvate

In the structure of [Cu(C17H14N3S2)2]·2C3H7NO, the Cu atom (site symmetry ) is N,S-chelated by the two deprotonated Schiff-base anions that define a distorted square-planar geometry. An N—H⋯O hydrogen bond links the mononuclear complex to the DMF solvent mol­ecules.

Structure of a Crystalline Vapochromic Platinum(II) Salt

Square-planar cations of the orange form of [Pt(Me2bzimpy)Cl](PF6) x DMF [Me2bzimpy = 2,6-bis(N-methylbenzimidazol-2-yl)pyridine] stack along the b axis in a head-to-tail arrangement with short interplanar spacings (3.35 and 3.39 A). Long intermolecular Pt...Pt contacts [4.336(2) and 4.565(2) A] and comparatively short Me2bzimpy...Me2bzimpy distances are consistent with spectroscopic measurements for orange salts of Pt(Me2bzimpy)Cl+. The DMF solvent molecules line channels parallel to c, which may provide a conduit for vapor absorption. The crystals are vapochromic, changing from orange to violet upon exposure to acetonitrile vapor. The changes in spectroscopic properties accompanying vapor absorption are consistent with changes in intermolecular interactions between complexes.

(Ph3Sn)3VO4]·CH3CN und [(Ph3Sn)3VO4]·2 DMF, Triphenylzinnvanadate mit neuartigen Kettenstrukturen

Abstract[(Ph3Sn)3VO4]·CH3CN and [(Ph3Sn)3VO4]·2 DMF, Triphenyltin Vanadates with Novel Chain StructuresThe reaction of Na3VO4 with Ph3SnCl in a water/CH2Cl2 mixture leads to the formation of [(Ph3Sn)3VO4] (1). Recrystallization of 1 from toluene/CH3CN gives pale yellow crystals of [(Ph3Sn)3VO4]·CH3CN (2). 2 crystallizes as coordination polymer which consists of infinite chains composed of corner‐sharing VO4 tetrahedra and Ph3SnO2 trigonal bipyramides. Additionally the VO4 groups are connected to two terminal SnPh3‐Groups containing tin atoms in a tetrahedral environment. [(Ph3Sn)3VO4]·2 DMF (3) which is obtained from Na3VO4 and Ph3SnCl in a water/DMF mixture contains a polymeric chain structure similar to 2 and additionally one of the terminal SnPh3 groups is coordinated to a DMF solvent molecule.

Electron Paramagnetic Resonance Structure Investigation of Copper Complexation in a Hemicarcerand

The double-bridged hemicarcerand [A,B-(CH2OH)2-cavitand]-(CH2NHCH2)2-[A,B-(CH2OH)2-cavitand] 23 (and several other related compounds) was synthesized by the condensation of the two complementary precursors A,B-(CH2NH2)2(CH2OH)2-cavitand and A,B-(CH2Br)2(CH2OAc)2-cavitand followed by hydrolysis of the acetate groups. This hemicarcerand has nitrogen and oxygen donor atoms located on the interior of the spherical cavity and thus allows endohedral coordination of metal ions. The cavity has a volume of approximately 0.12 nm3, a value obtained by calculating a Connolly-type contact surface and the molecular electrostatic potential. The Cu2+ complex of hemicarcerand 23 was studied in detail by EPR and DFT calculations at the UB3LYP/6-31G level to verify the anticipated endohedral nature of the metal complex. It could be shown that the copper ion is coordinated to four oxygen donor atoms and no deviation from axial symmetry at the copper site could be detected. No direct coordination to nitrogen atoms of the hemicarcerand could be observed; however, complexation with DMF solvent molecules was detected by ESEEM and HYSCORE experiments. The closed structure of the hemicarcerand was also confirmed by an evaluation of proton-copper distances. Results from DFT calculations are in accord with the EPR results, and further support suggested coordination of the Cu(II) within the hemicarcerand cavity by four oxygen donor atoms.

Chromium(V) Peptide Complexes: Synthesis and Spectroscopic Characterization

A series of stable Cr(V) model complexes that mimic the binding of Cr(V) to peptide backbones at the C-terminus of proteins have been prepared for N,N-dimethylurea derivatives of the tripeptides Aib3-DMF, AibLAlaAib-DMF, and AibDAlaAib-DMF (Aib = 2-amino-2-methylpropanoic acid, DMF = N,N-dimethylformamide). The Cr(ll) precursor complexes were synthesized by the initial deprotonation of the amide and acid groups of the peptide ligands in DMF with potassium tert-butoxide in the presence of CrCl2. The Cr(II) intermediates thus formed were then immediately oxidized to Cr(V) using tert-butyl hydroperoxide. Spectroscopic and mass-spectrometric analyses of the Cr(V) complexes showed that a new metal-directed organic transformation of the ligand had occurred. This involved a DMF solvent molecule becoming covalently bound to the amine group of the peptide ligand, yielding a urea group, and a third coordinated deprotonated urea nitrogen donor. A metal-directed oxidative coupling has been proposed as a possible mechanism for the organic transformation. The Cr(V/IV) reduction potential was determined for the three Cr(V) complexes using cyclic voltammetry, and in all cases it was quasi-reversible. These are the first isolated and fully characterized Cr(V) complexes with non-sulfur-containing peptide ligands.

Synthesis and X-ray crystallographic studies of novel proton-ionizable nitro- and halogen-substituted acridono-18-crown-6 chromo- and fluorogenic ionophores

Starting from acridono-18-crown-6 ligand 1 ( Fig. 1) seven new proton-ionizable chromogenic and fluorogenic ionophores 2– 8 ( Fig. 1) containing NO 2 group(s) and/or Br or Cl atom(s) in the aromatic rings were prepared by electrophilic substitution. The precursor macrocycle 1 was obtained by a modification of the reported procedure which made chromatography unnecessary in purification and gave higher yield. X-ray crystallographic studies of the complexes of acridono-18-crown-6 type ligands 1 , 2 , 3 , 6 and 8 show that the proton-ionizable units are in the acridone tautomeric form and that the ligands invariably bind a water molecule in their cavities by multipodal hydrogen bonding. In two cases ( 6 and 8 ) an additional DMF solvent molecule is also bound at the crown perimeter in the solid state.