Structural Transformation Pathways of Alkaline Earth Family Coordination Polymers Containing 3,3',5,5'-Biphenyl Tetracarboxylic Acid.

The understanding of crystal stepwise transformation is very important to enclose the "black box" in the preparation of crystal materials. In this work, different structural intermediates were isolated prior to the formation of the final alkali earth coordination polymers (CPs) during the preparation of three pairs of alkali earth CPs through solvothermal method and convenient oil-bath reactions. Single crystal X-ray diffraction analysis demonstrated the structural transformation from a 0 D to 1 D inorganic connectivity for the Ca-CPs and Sr-CPs, but a 1 D to 0 D inorganic connectivity for Ba-CPs, involving the breakage/formation of chemical bonds in the reaction solutions. Further analyses indicated that these two different structural transformation pathways are determined by the deprotonation of organic acid, competitive balance between the inorganic and organic connectivity, and the twist of the linker. FT-IR spectra, thermogravimetric and luminescence behaviors agree with their structural characteristics.

pH-Dependent reversible crystal transformation of 1-carboxymethyl-1-methyl-pyrrolidinium bromides and their spectroscopic fingerprint.

In this work, two 1-carboxymethyl-1-methyl-pyrrolidinium bromides (N-methylpyrrolidine betaine hydrobromides) with the stoichiometry of betaine:hydrobromic acid as 1:1 and 2:1, denoted as CMPRHBr-I and CMPRHBr-II, respectively, were prepared and crystallographically determined. The large difference in these two structures is the type of hydrogen bonds, resulting in the different thermal stability. A strong OH⋯Br hydrogen bond was observed in CMPRHBr-I, whereas O⋯H⋯O hydrogen bond in CMPRHBr-II. Both these two crystals can mutually transform by changing the pH value of the aqueous solution. Vibrational spectroscopic studies shows that these two structures can be easily distinguished by the characteristic bands such as νCO stretching vibration and the D-type bands. Our studies indicate that it should be cautious of the structural change as this type of organic salts was purified and recrystallized.

A four-unit [c2]daisy chain connected by hydrogen bonds.

A mono-adenine-functionalized pillar[5]arene and a guest including uracil were prepared. They formed a novel four-unit [c2]daisy chain both in the solid state and in a chloroform solution. As far as we know, this [c2]daisy chain is the first one without a covalently bound linear thread. This unique assembly behavior is mainly induced by hydrogen-bond interactions between A and U in the A-U base pairs.

From a binary salt to salt co-crystals of antibacterial agent lomefloxacin with improved solubility and bioavailability.

The cocrystallization of lomefloxacin (Lf) with barbituric acid (HBA) and/or isophthalic acid (H2ip) leads to novel binary and ternary salts via hydrogen-bonding recognition. X-ray single-crystal diffraction analyses show that zwitterionic lomefloxacin can adjust itself to fulfill a different supramolecular array in either binary salts or ternary salt co-crystals, formulated as [HLf]·[Hip]·H2O (1), [HLf]·[BA]·[HBA]·H2O (2) and [HLf]·[BA]·[H2ip]·CH3OH·H2O (3). These pharmaceutical agents present uniform charge-assisted hydrogen-bonding networks between HLf cations and acidic coformers with the lattice capturing water molecules. Structural comparison of (2) and (3) indicated that a delicate balance of geometries and hydrogen-bonding partners is required for stacking to favor the formation of ternary salt co-crystals. Cocrystallization was able to overcome the water insolubility of lomefloxacin. Both the salt co-crystals display enhanced solubility and better pharmaceutical applicability.

[Ab initio calculations of vibrational frequencies and structures of ion pairs of perchlorate].

Ion association of solutions of lithium perchlorate in N,N-dimethylformamide, acetonitrile, tetrahydrofuran, acetone, methyl acetate and other organic solvents have been investigated by infrared and Raman spectroscopy, respectively. The spectroscopically free ion, contact ion pair and dimer are fingerprint by the curve fitting of upsilon1 band of. The most stable geometries of contact ion pairs and dimmer, and the vibrational frequencies were optimized and calculated using the ab initio methods. The comparison between calculated and experimental data of band position was made. Effect of solvation mode and solvent molecule on the vibrational frequencies of ion pairs was also indicated.

[Theoretical study on structure and vibrational spectra of M+ AsF6- (M=Li, Na, K, Rb and Cs) contact ion pairs].

The present paper reports the possible geometries and vibrational spectra of AsF6- anion and M+ AsF6- (M+ = Li+, Na+, K+, Rb+ and Cs+) contact ion pairs. It was shown that the tridentate C3v structure of M+ AsF- was preferred over the monodentate and bidentate geometry. In the tridentate structure, the symmetry of AsF6- in the coordination is lowered because of the presence of M+, and its structural parameters and vibrational modes largely differ from its original octahedral structure. The effect of Li+ on the structure of AsF6- was greater due to its larger charge/radius ratio. The calculated bands for AsF6- in M+ AsF6-, located in the range of 600-800 cm(-1), could be used to fingerprint what kind of ion pair was present in solutions.

Bis(benzoato-κO,O')(2,9-dimethyl-1,10-phenanthroline-κN,N')cobalt(II).

In the title compound, [Co(C(7)H(5)O(2))(2)(C(14)H(12)N(2))], the Co(II) ion is located on a twofold rotation axis and is chelated by a 2,9-dimethyl-1,10-phenanthroline (dmphen) ligand and two benzoate anions in a distorted octa-hedral geometry. The crystal packing is stabilized by π-π inter-actions between parallel dmphen ligands of neighbouring mol-ecules, with a face-to-face distance of 3.411 (2) Å.

(2,9-Dimethyl-1,10-phenanthroline-κN,N')bis-(2-hydroxy-benzoato)-κO;κO,O'-cobalt(II).

In the title compound, [Co(C(7)H(5)O(3))(2)(C(14)H(12)N(2))], the Co(II) ion is five-coordinated by two N atoms from one 2,9-dimethyl-1,10-phenanthroline (dmphen) ligand and three O atoms from two 2-hydroxy-benzoate anions in a distorted trigonal bipyramidal geometry. The carboxyl-ate group of one of the two 2-hydroxy-benzoate anions is monodentate with a normal Co-O distance [1.9804 (18) Å], while the other is bidentate with two longer Co-O bonds [2.1981 (18) and 2.1359 (19) Å]. The crystal structure is stabilized by aromatic π-π stacking inter-actions [centroid-centroid distances of 4.0380 (3) and 3.8216 (3) Šbetween dmphen/dmphen and benzene/dmphen rings, respectively] and C-H⋯π(benzene) inter-actions.

Factors affecting ionic liquids based removal of anionic dyes from water.

Liquid--liquid extraction with imidazolium based ionic liquids--[C4mim][PF6], [C6miml][PF6], [C6mim[BF4], and [C8mim][PF6--is proposed for removal of anionic dyes including methyl orange, eosin yellow, and orange G from aqueous solutions. The effects of extraction time, pH of aqueous phase, structure of the ionic liquids, temperature, and KCl concentration on the extraction efficiencies have been studied. Extraction efficiencies of dyes were strongly affected by the pH of the aqueous phase. Under the optimized pH condition, 85-99% of methyl orange, almost 100% eosin yellows, and 69% of orange G in tested water samples were transferred into the ionic liquids in a single extraction. Extraction efficiency for a given dye was found to increase with increasing temperature and increasing alkyl chain length of cation of the ionic liquids. Presence of a small amount of KCl in the aqueous phase did not considerably improve the extraction efficiency of the dyes. Thermodynamic studies revealed that the extraction process was driven by hydrophobic interaction of the anionic dyes and the ionic liquids.

Erratum: catena-Poly[[(2,9-dimethyl-1,10-phenanthroline-κN,N')lead(II)]-di-µ-2-hydroxy-benzoato-κO,O:O;κO:O,O]. Corrigendum.

A reference in the paper by Xuan & Zhao [Acta Cryst. (2007), E63, m2678] is replaced.[This corrects the article DOI: 10.1107/S1600536807045941.].

Bis(µ-3-hydroxy-benzoato-κO,O':O)bis-[aqua-(3-hydroxy-benzoato-κO,O')(1,10-phenanthroline-κN,N')lead(II)] monohydrate.

In the centrosymmetric binuclear title complex, [Pb(2)(C(7)H(5)O(3))(4)(C(12)H(8)N(2))(2)(H(2)O)(2)]·H(2)O, each Pb atom is eight-coordinated in a PbO(6)N(2) environment by two N atoms from the 1,10-phenanthroline (phen) ligand, five carboxylate O atoms from four 3-hydroxy-benzoate anions and one O atom from the coordinated water mol-ecule in a distorted bicapped trigonal-prismatic geometry. The benzoate groups coordinate each Pb(II) atom in two different ways. Two benzoate ions behave as bidentate ligands to the Pb atom, and another benzoate ion bridges the Pb atoms, forming a binuclear structure. The dimeric units are packed via O-H⋯O hydrogen bonds and π-π inter-actions between the aromatic rings of neighboring mol-ecules, with centroid-centroid distances of 3.552 (2) and 3.641 (2) Å.

[Ion solvation and ion association in high-concentration of NaBF4/DMF solutions].

Ion solvation and ion association in solutions of NaBF4/DMF were studied by infrared and Raman spectroscopy and ab initio quantum chemistry. It was found that the sodium cation interacts on oxygen atom of C=O group in DMF molecules. The solvation number of Na+, four, was obtained according to the change analysis of CH3 rocking band. The splitting of the nu1 mode of BF4(-) anion indicates the presence of contact ion pairs. Ionic association degree increases with increasing molality of the salt. The solvated structure of Na+ and the geometry of Li+ BF4(-) ion pair were also suggested based on the ab initio calculations.