The dehydration process in the DL-phenylglycinium trifluoromethanesulfonate monohydrate crystal revealed by XRD, vibrational and DSC studies

Thermal analysis, X-ray diffraction and temperature-dependent IR spectroscopy were used to study the dehydration process of crystalline DL-phenylglycinium trifluoromethanesulfonate monohydrate (PGTFH), C8H10NO2 +·CF3SO3 −·H2O. PGTFH dehydrates in one step centred at 353 K and crystallizes in the monoclinic space group C2/c, whereas the anhydrous compound (PGTF) crystallizes in the triclinic space group P\overline{1}. The dehydration process in PGTFH is preceded by a weakening of both the noncovalent aromatic–aromatic interactions and the packing contacts. This process is accompanied by the breakage of medium-strength O—H...O hydrogen bonds between ions inside layers and a reorganization of the ions within the layers. This reorganization results in the formation of two different ion pairs (DL-phenylglycinium trifluoromethanesulfonate) and the formation of a new hydrogen-bond network. The dehydration process does not destroy the nature of the crystal structure. Both crystals, i.e. hydrated and anhydrous, have a layered structure, although the layers of each crystal are arranged somewhat differently.

Band gap, sorption properties and fluorescence sensing behaviour of a novel 1D→2D cathenane-like cobalt(II)–organic framework

A novel hydrolytic stable CoII–organic framework, namely poly[[bis(2-amino-4-sulfonatobenzoato-κO 1)tetraaquatris{μ-1,4-bis[(imidazol-1-yl)methyl]benzene-κ2 N 3:N 3′}dicobalt(II)] tetrahydrate], {[Co(C7H5NO5S)(C14H14N4)1.5(H2O)2]·2H2O} n , (1), based on multifunctional 2-amino-5-sulfobenzoic acid (H2asba) and the auxiliary flexible ligand 1,4-bis[(imidazol-1-yl)methyl]benzene (bix), was prepared using the solution evaporation method. The purity of (1) was confirmed by elemental analysis and powder X-ray diffraction (PXRD) analysis. Complex (1) shows a novel 1D→2D interpenetrating network, which is further extended into a 3D supramolecular framework with channels occupied by the lattice water molecules. The 2-amino-4-sulfonatobenzoate (asba2−) ligand adopts a monodentate coordination mode. The bix ligands exhibit gauche–gauche (GG) and trans–trans (TT) conformations. A detailed analysis of the solid-state diffuse-reflectance UV–Vis spectrum reveals that an indirect band gap exists in the complex. The band structure, the total density of states (TDOS) and the partial density of states (PDOS) were calculated using the CASTEP program. The calculated band gap (E g) matches well with the experimental one. The complex exhibits a reversible dehydration–rehydration behaviour. Interestingly, gas sorption experiments demonstrate that the new fully anhydrous compound obtained by activating complex (1) at 400 K shows selective adsorption of CO2 over N2. Complex (1) retains excellent framework stability in a variety of solvents and manifests distinct solvent-dependent fluorescence properties. Moreover, the complex shows multiresponsive fluorescence sensing for some nitroaromatics in aqueous medium.

Structural Transformations in the Thermal Dehydration of [Cu2(bpa)(btec)(H2O)4]n Coordination Polymer

Reactions between pyridinic ligands such as 1,2-bis(4-pyridyl)ethane (bpa) and transition metal cations are a very widespread technique to produce extended coordination polymers such as Metal-Organic Frameworks. In combination with a second ligand these systems could present different topologies and behaviors. In this context, the use of 1,2,4,5-benzenetetracarboxylic acid (H4btec) gave us a novel 2D compound, [Cu2(bpa)(btec)(H2O)4]n (1), which was prepared by microwave-assisted synthesis and structurally characterized by means of single crystal X-ray diffraction. Its thermal behavior was analyzed through thermogravimetric analysis and variable temperature powder X-ray diffraction, concluding that thermal stability is influenced by the coordination water molecules, allowing two sequential thermochromic phase transformations to take place. These transformations were monitored by electronic paramagnetic resonance spectroscopy and magnetic susceptibility measurements. In addition, the crystal structure of the anhydrous compound [Cu2(bpa)(btec)]n (1.ah) was determined. Finally, a topological study was carried out for the bpa ligand considering all the structures deposited in the Cambridge Structural Databased. More than 1000 structures were analyzed and classified into 17 different topologies, according to the role of the ligand.

Synthesis and crystal structure of anhydrous Na[MnO4]

There are numerous reports in the literature about the amount of hydrate water in sodium permanganate, which is said to be between one half and three water molecules per Na[MnO4]. Because no structural descriptions of the hydrate and the anhydrous compound can be found yet, this work reports the synthesis of anhydrous Na[MnO4] via the Muthmann method and its crystal structure. Na[MnO4] crystallizes as dark purple needles in the monoclinic space group P21/n with a = 572.98(5), b = 842.59(7), c = 715.47(6) pm, β = 92.374(3)° and Z = 4. As such and with its isotype to Ag[MnO4], Na[MnO4] completes the series of anhydrous alkali-metal permanganates, comprising Li[MnO4] (orthorhombic, Cmcm, Cr[VO4] type) and the isostructural heavier congeners A[MnO4] (A = K, Rb, Cs; orthorhombic, Pnma, Ba[SO4] type).

The effect of coordinated water on the connectivity of uranium(IV) sulfatex-hydrate: [U(SO4)2(H2O)5]·H2O and [U(SO4)2(H2O)6]·2H2O, and a comparison with other known structures

Two new solid-state uranium(IV) sulfatex-hydrate complexes (wherexis the total number of coordinated plus solvent waters), namelycatena-poly[[pentaaquauranium(IV)]-di-μ-sulfato-κ4O:O′] monohydrate], {[U(SO4)2(H2O)5]·H2O}n, and hexaaquabis(sulfato-κ2O,O′)uranium(IV) dihydrate, [U(SO4)2(H2O)6]·2H2O, have been synthesized, structurally characterized by single-crystal X-ray diffraction and analyzed by vibrational (IR and Raman) spectroscopy. By comparing these structures with those of four other known uranium(IV) sulfatex-hydrates, the effect of additional coordinated water molecules on their structures has been elucidated. As the number of coordinated water molecules increases, the sulfate bonds are displaced, thus changing the binding mode of the sulfate ligands to the uranium centre. As a result, uranium(IV) sulfatex-hydrate changes from being fully crosslinked in three dimensions in the anhydrous compound, through sheet and chain linking in the tetra- and hexahydrates, to fully unlinked molecules in the octa- and nonahydrates. It can be concluded that coordinated waters play an important role in determining the structure and connectivity of UIVsulfate complexes.

The effect of partial methylation of the glycine amino group on crystal structure inN,N-dimethylglycine and its hemihydrate

N,N-Dimethylglycine, C4H9NO2, and its hemihydrate, C4H9NO2·0.5H2O, are discussed in order to follow the effect of the methylation of the glycine amino group (and thus its ability to form several hydrogen bonds) on crystal structure, in particular on the possibility of the formation of hydrogen-bonded `head-to-tail' chains, which are typical for the crystal structures of amino acids and essential for considering amino acid crystals as mimics of peptide chains. Both compounds crystallize in centrosymmetric space groups (PbcaandC2/c, respectively) and have twoN,N-dimethylglycine zwitterions in the asymmetric unit. In the anhydrous compound, there are no head-to-tail chains but the zwitterions formR44(20) ring motifs, which are not bonded to each other by any hydrogen bonds. In contrast, in the crystal structure ofN,N-dimethylglycinium hemihydrate, the zwitterions are linked to each other by N—H...O hydrogen bonds into infiniteC22(10) head-to-tail chains, while the water molecules outside the chains provide additional hydrogen bonds to the carboxylate groups.

Cadmium Carboxylate Chemistry: Preparation, Crystal Structure, and Thermal and Spectroscopic Characterization of the One-dimensional Polymer [Cd(O2CMe)(O2CPh)(H2O)2]n

Compound [Cd(O2CMe)(O2CPh)(H2O)2]n (1) was initially obtained in a serendipitous way during efforts to prepare a CdII /PhCO2 −/bepy complex (bepy = 2-benzoylpyridine). With the identity of 1 established by single-crystal X-ray crystallography, a rational preparative route to this complex was designed and carried out by reacting Cd(O2CMe)2·2H2O with a slight excess of PhCOOH in MeCN under reflux. The crystal structure of 1 consists of isolated zig-zag chains. The CdII atom is coordinated to five carboxylate and two aqua oxygen atoms creating a distorted, capped trigonal prismatic coordination polyhedron. The acetate group exhibits the η1:η2:μ2 coordination mode, while the benzoate ligand is chelating. There is an extensive hydrogen-bonding network which reinforces the chains and also links them generating sheets. The new complex was characterized by IR, far-IR, Raman, CP MAS and solution 113Cd NMR spectroscopy. The spectroscopic data are discussed in terms of the nature of bonding and the known structure. An anhydrous compound with the empirical formula Cd(O2CMe)(O2CPh) was isolated during the thermal decomposition of 1; the vibrational study of this thermally stable intermediate supports an 1D polymeric structure with 6-coordinate CdII ions.

Dehydration and volatilization non isothermic kinetic of the solid state aluminium 8-hydroxyquinolinate

Al(C9H6ON)3.2.5H2O was precipitated from the mixture of an aqueous solution of aluminium ion and an acid solution of 8-hydroxyquinoline, by increasing the pH value to 9.5 with ammonia aqueous solution. The TG curves in nitrogen atmosphere present mass losses due to dehydration, partial volatilisation (sublimation plus vaporisation) of the anhydrous compound followed by thermal decomposition with the formation of a mixture of carbonaceous and residues. The relation between sublimation and vaporisation depends on the heating rate used. The non isothermic integral isoconventional methods as linear equations of Ozawa-Flynn-Wall and Kissinger-Akahira-Sunose (KAS) were used to obtain the kinetic parameters from TG and DTA curves, respectively. Despite the fact that both dehydration and volatilisation reactions follow the linearity by using both methods, only for the volatilisation reaction the validity condition, 20<= E/RT<= 50, was verified.

The Crystal and Molecular Structure and Properties of Diaqua[N-salicylidene – (S) – (+) – glutamato]copper(II) Monohydrate

The crystal and molecular structure of the title complex was determinated by single crystal X-ray diffraction (R = 0.066 for 1059 observed reflections). The approximately square-pyramidal coordination of Cu(II) results from donor atoms O(12), O(1), N(1), O(5) of one H2O molecule as well as the tridentate Schiff base dianion ligand and from the weakly bonded O(1) donor atom of one other H2O molecule in the apical site.The magnetic behaviour of the complex studied obeys the Curie—Weiss law in the temperature range 94—309 K with a small value of the Weiss constant, θ = 1.4 Κ. A similar cryomagnetic behaviour is also characteristic for the anhydrous compound, [N-salicylidene—(S)—(+)-glutamato]copper(II), obtained by thermal dehydration of the title complex.

Magnetic properties of anhydrous and hydrated dimethylphosphinates of manganese(II). The crystal and molecular structure of poly-bis(μ-dimethylphosphinato)diaquomanganese(II)

The dimethylphosphinate of manganese(II), Mn[(CH3)2PO2]2, and its dihydrate have been prepared and studied using magnetic susceptibility, differential scanning calorimetry, and electronic and vibrational spectroscopic methods. The dihydrate was obtained in crystalline form and a single crystal X-ray diffraction study revealed a polymeric structure.Crystals of poly-bis(μ-dimethylphosphinato)diaquomanganese(II) are monoclinic, a = 20.722(3), b = 4.8652(2), c = 11.0689(14) Å, β = 102.209(7)°, Z = 4, space group C2/c. The structure was solved by conventional heavy-atom methods and was refined by full-matrix least-squares procedures to R = 0.030 and Rw = 0.033 for 983 reflections with I ≥ 3σ(I). The structure consists of infinite centrosymmetric chains of Mn(II) atoms linked by double phosphinate bridges and extending along the crystallographic b axis. The water molecules are involved in both interchain and bifurcated intrachain hydrogen bonding [Formula: see text], 2.899(3) and 3.120(3) Å). The coordination about Mn is slightly distorted octahedral with libration-corrected bond lengths Mn—O(phosphinato) = 2.156(2) and 2.212(2), Mn—OH2 = 2.247(2) Å.Magnetic susceptibility studies on the dihydrate from 300 to 4.2 K reveal a magnetic moment of ~5.9 BM over most of the range and give no evidence for significant magnetic exchange. The anhydrous compound, which is considered on the basis of indirect evidence to retain the double phosphinate bridged structure exhibited by the dihydrate, shows relatively strong antiferromagnetic behaviour. The data have been analyzed according to two theoretical models both of which employ the isotropic Heinsenberg Hamiltonian. The scaling model of Wagner and Friedberg gives J = −2.94 cm−1 and g = 2.02 and the interpolation scheme of Weng gives J = −2.69 cm−1 and g = 2.01. The magnitude of the exchange coupling is considered in relation to that observed in related manganese compounds and possible reasons for the observed damping of the exchange on hydration are discussed.