Hydrogen bonded structures in organic amine oxalates

Bromide hydrogen oxalate salts with the diprotonated 1,4-diazabicyclo[2.2.2]octane counterion

Two new salts composed of the diprotonated 1,4-diazabicyclo[2.2.2]octane (DABCO) molecule as the cations and bromide and hydrogen oxalate as the anions have been isolated and structurally characterized by X-ray diffraction analysis. The salt [DABCOH2]{[HC2O4][Br]} (1) crystallizes in the orthorhombic system, space group P212121 with a = 9.0809(7), b = 9.5156(7), c = 12.3558(9) Å, V = 1067.67(14) Å3 and Z = 4. The salt [DABCOH2]2{[HC2O4][Br]3}·H2O (2) crystallizes in the orthorhombic system, space group Pnma with a = 26.6554(17), b = 7.3711(4), c = 10.7421(7) Å, V = 2110.6(2) Å3 and Z = 4. The compounds were prepared from ethanolic solutions of [DABCOH2][HC2O4]2 (L 1 ) and ZnBr2 in molar ratios of 2:1 and 1:1, respectively. The salts 1 and 2 exhibit extended hydrogen bonding networks leading to supramolecular topologies.

Efficient synthesis of dipeptide analogues of α-fluorinated β-aminophosphonates

Herein, we present an efficient synthesis of dipeptide analogues of α-fluorinated β-aminophosphonates. Each step of the synthesis was optimized to provide excellent yields. Moreover, the absolute configuration of the obtained compounds was determined by X-ray analysis, which proved the stereochemistry that was proposed based on NMR studies.

Crystal structure of (ferrocenylmeth-yl)di-methyl-ammonium hydrogen oxalate

The crystal structure of the title salt, [Fe(C5H5)(C8H13N)](HC2O4), consists of discrete (ferrocenylmeth-yl)di-methyl-ammonium cations and hydrogen oxalate anions. The anions are connected through a strong O-H⋯O hydrogen bond, forming linear chains running parallel to [100]. The cations are linked to the anions through bifurcated N-H⋯(O,O') hydrogen bonds. Weak C-H⋯π inter-actions between neighbouring ferrocenyl moieties are also observed.

Crystal structure of allyl-ammonium hydrogen succinate at 100 K

The asymmetric unit of the title compound, C₂H₈N⁺·C₄H₅O₄⁻, consists of two allyl­ammonium cations and two hydrogen succinate anions (Z′ = 2). One of the cations has a near-perfect syn-periplanar (cis) conformation with an N—C—C—C torsion angle of 0.4 (3)°, while the other is characterized by a gauche conformation and a torsion angle of 102.5 (3)°. Regarding the anions, three out of four carboxilic groups are twisted with respect to the central C–CH₂–CH₂–C group [dihedral angles = 24.4 (2), 31.2 (2) and 40.4 (2)°], the remaining one being instead almost coplanar, with a dihedral angle of 4.0 (2)°. In the crystal, there are two very short, near linear O—H⋯O hydrogen bonds between anions, with the H atoms shifted notably from the donor O towards the O⋯O midpoint. These O—H⋯O hydrogen bonds form helical chains along the [011] which are further linked to each other through N—H⋯O hydrogen bonds (involving all the available NH groups), forming layers lying parallel to (100).

Allyl-ammonium hydrogen oxalate hemihydrate

In the title hydrated mol-ecular salt, C3H8N(+)·C2HO4 (-)·0.5H2O, the water O atom lies on a crystallographic twofold axis. The C=C-C-N torsion angle in the cation is 2.8 (3)° and the dihedral angle between the CO2 and CO2H planes in the anion is 1.0 (4)°. In the crystal, the hydrogen oxalate ions are linked by O-H⋯O hydrogen bonds, generating [010] chains. The allyl-ammonium cations bond to the chains through N-H⋯O and N-H⋯(O,O) hydrogen bonds. The water mol-ecule accepts two N-H⋯O hydrogen bonds and makes two O-H⋯O hydrogen bonds. Together, the hydrogen bonds generate (100) sheets.

1-Methyl-piperazine-1,4-dium bis-(hydrogen oxalate)

In the crystal structure of the title compound, C5H14N2 (2+)·2HC2O4 (-), the two crystallographically independent hydrogen oxalate anions are linked by strong inter-molecular O-H⋯O hydrogen bonds, forming two independent corrugated chains parallel to the b axis. These chains are further connected by N-H⋯O and C-H⋯O hydrogen bonds originating from the organic cations, forming a three-dimensional network. The diprotonated piperazine ring adopts a chair conformation, with the methyl group occupying an equatorial position.

Piperazine-1,4-diium bis(2,4,5-tricarboxybenzoate) dihydrate

In the title hydrated salt, C₄H₁₂N₂²⁺·2C₁₀H₅O₈⁻·2H₂O, the piperazinediium cation, lying about an inversion center, adopts a chair conformation. The benzene ring of the anion makes dihedral angles of 25.17 (8)° with the carboxyl­ate group and angles of 8.50 (7), 20.07 (7) and 80.86 (8)° with the three carb­oxy­lic acid groups. In the crystal, the cations, anions and water mol­ecules are connected by O—H⋯O and N—H⋯O hydrogen bonds into double layers parallel to (110).

Molecular interactions of 2'-deoxyguanosine 5'-monophosphate with glycine in aqueous media probed via concentration and pH dependent Raman spectroscopic investigations and DFT study

In order to gain insights into nucleotide-protein interaction, the molecular interaction of glycine (Gly) with 2'-deoxyguanosine 5'-monophosphate (dGMP) was monitored in aqueous media through Raman spectroscopic measurements and density functional theory (DFT) calculations. Raman spectra of dGMP, glycine and their binary mixtures (dGMP + Gly) in aqueous media at 10 different concentrations corresponding to the dGMP : Gly molar ratios varying from 1 : 1 to 1 : 10 were recorded in the fingerprint region 2000-400 cm(-1). Raman spectra of the dGMP : Gly mixture with a molar ratio of 1 : 3 in aqueous media at 10 different pH values starting from 1 to 10 at an interval of 1 were also recorded. The DFT calculations were performed on dGMP, glycine and their various complexes with varying number of H(2)O molecules in gas phase as well as in solvation using hybrid functional B3LYP employing the high level basis set 6-311+G(d,p). The variations in the observed spectral features were explained in terms of calculated optimized structures of dGMP, glycine and their various complexes with water molecules and a good spectra-structure correlation was obtained. Raman spectra of glycine in 1.2 M aqueous solution were also recorded at three pH values, 2, 6 and 10, and the subtle differences in the spectral features were correlated with the calculated Raman spectra of protonated, deprotonated and zwitterionic forms of glycine. The results also give experimental evidence rather convincingly that the zwitterionic and protonated forms of glycine are formed at pH = 6 and 2, respectively, but even at pH = 10, deprotonated glycine is not formed. An important aspect of this study is the monitoring of the interaction of dGMP with the zwitterionic form of glycine giving insightful details regarding the binding site.

Self-assembling systems based on amphiphilic alkyltriphenylphosphonium bromides: elucidation of the role of head group

A systematic study of the aggregation behavior of alkyltriphenylphosphonium bromides (TPPB-n; n=8, 10, 12, 14, 16, 18; here n is the number of carbon atoms in alkyl groups) in aqueous solutions has been carried out and compared with trimethyl ammonium bromides (TMAB-n). Critical micelle concentrations (cmcs) of TPPB-n and TMAB-n decrease with the number of carbon atoms with the slope parameter of ca.0.3. The low cmcs and effective solubilization power toward Orange OT indicate high micellization capacity of phosphonium surfactants. The low counterion binding parameter β is revealed for TPPB-10 and TPPB-12, while high counterion binding of ≥80% is observed for high TPPB-n homologs. Values of the surface potential ψ calculated on the basis of pK(a) shifts of p-nitrophenols is similar for both series and monotonously increase with alkyl chain length. Several points indicate non-monotonic changes within TPPB-n series. There are peculiarities of the tensiometry and solubilization plots for high homologs and above mentioned increases in counterion binding on transiting from low to high molecular weight surfactants. Differences in aggregation behavior between TPPB and TMAB series and between low and high homologs can be due to the specific structural character of the TPP(+) cation, which is supported by X-ray data.

NIR-FT Raman and infrared spectra and ab initio computations of glycinium oxalate

The single crystals of glycinium oxalate are grown by slow evaporation technique and vibrational spectral analysis is carried out using NIR-FT Raman and FT-IR spectra. The ab initio quantum computations are also performed at HF/6-31 G(d) level to derive the optimized geometry, atomic charges and vibrational frequencies of the glycinium oxalate molecule. Vibrational analysis indicates the presence of peculiar intermolecular C-H...O hydrogen bonding interaction producing "blue shift" of C-H stretching frequency. The vibrational spectra confirm the existence of NH3(+) in glycinium oxalate. Hydroxyl vibrations with different inter and intra molecular H-bonding are analysed, supported by computed results.

Synthesis, Resolution, and Applications of 1,16-Dihydroxytetraphenylene as a Novel Building Block in Molecular Recognition and Assembly1

This paper concerns the synthesis of 1,16-dihydroxytetraphenylene (DHTP) (2) by employing a novel NBS bromination route. (+/-)-DHTP 2 was successfully resolved into its optical antipodes and converted to (+/-)-1,16-bis(diphenylphosphino)tetraphenylene (BPTP) (26), whose platinum complex BPTP-PtCl(2) (27) was also obtained. As a hydrogen bond donor, racemic and optically active DHTP 2 was allowed to assemble with 4,4'-bipyridine to form single crystals of good quality. X-ray Diffraction studies of these crystals revealed that the crystallographic packing of the hydrogen bonded complex between (+/-)-2 and 4,4'-bipyridine was different from the one formed from (S)-2 and 4,4'-bipyridine. It was found that an infinite zigzag chain with alternate chirality was formed in the assembly of (+/-)-2 and 4,4'-bipyridine, while (S)-2 and 4,4'-bipyridine failed to show the same assembly pattern. The reason (+/-)-2 formed an alternate and zigzag chain with 4,4'-bipyridine was most likely due to the inherent stability of this supramolecular assembly. The chiral recognition between 2 and optically active BINAP under the direction of platinum(II) has also been examined. (1)H and (31)P NMR spectroscopic studies demonstrated that there was an obvious discrimination of 2 between the enantiomers of BINAP-PtCO(3).