Karl A. Byriel

Molecular cocrystals of carboxylic acids. XX. The crystal structures of 3, 5-Dinitrosalicylic acid and its adducts with the isomeric monoaminobenzoic acids

The crystal structure of 3,5-dinitrosalicylic acid monohydrate (1) and its adducts with 2- aminobenzoic acid (2-aba) [( dnsa )(2-aba)] (2), 3-aminobenzoic acid (3-aba) [( dnsa )(3-aba)] (3), and 4-aminobenzoic acid (4-aba) [( dnsa )(4-aba)2] (4), have been determined and the hydrogen bonding associations in each analysed . The acid (1), which is essentially planar, forms strong hydrogen-bonding network associations involving the carboxylic, nitro and phenolic oxygens as well as the lattice water. In all adducts, protonation of the amino group of the second acid occurs, with subsequent hydrogen bonding via all three alkyl ammonium hydrogens to the carboxylic, nitro and phenolic oxygens of dnsa. With the 1:2 adduct (4), only one of the two 4-aba molecules is protonated, these forming a secondary hydrogen-bonded cyclic dimer. A strong intramolecular hydrogen bond between the phenolic proton and the carboxylate group is found in all adducts.

Dehydration Converts DsbG Crystal Diffraction from Low to High Resolution

Diffraction quality crystals are essential for crystallographic studies of protein structure, and the production of poorly diffracting crystals is often regarded as a dead end in the process. Here we show a dramatic improvement of poorly diffracting DsbG crystals allowing high-resolution diffraction data measurement. Before dehydration, the crystals are fragile and the diffraction pattern is streaky, extending to 10 A resolution. After dehydration, there is a spectacular improvement, with the diffraction pattern extending to 2 A resolution. This and other recent results show that dehydration is a simple, rapid, and inexpensive approach to convert poor quality crystals into diffraction quality crystals.

Preparation and crystal structures of the silver(I) carboxylates [Ag2{C6H4(CO2)2}(NH3)2], [NH4][Ag5{C6H3(CO2)3}2(NH3)2(H2O)2]·H2O and [NH4][Ag{C4H2N2(CO2)2}]

Two silver ammine complexes with the polyprotic aromatic acids benzene-1,2-diacarboxylic acid (phthalic acid) and benzene-1,3,5-tricarboxylic acid (trimesic acid) have been prepared and their structures determined using single-crystal X-ray diffraction and infrared spectroscopy. Complex 1, [Ag2{C6H4(CO2)2}(NH3)2], is a hydrogen-bonded polymer based on a simple diamminephthalatodisilver(I) species, with an ammonia molecule and a single phthalate carboxylate oxygen bonded to separate silver atoms, giving essentially linear co-ordination [Ag–N 2.116(3), Ag–O 2.134(2)A, O–Ag–N 175.3(1)°]. All three ammine hydrogens are involved in intermolecular hydrogen-bonding interactions, giving a chain polymer. Complex 2, [NH4][Ag5{C6H3(CO2)3}2(NH3)2(H2O)2]·H2O, is a two-dimensional sheet polymer based on a pseudo-centrosymmetric S-type trimer unit, linked by the carboxylate groups of two independent trimesate residues [Ag ⋯ Ag 2.928(1), 2.946(1)A]. The two ammonia molecules are also bonded linearly to two independent silvers [Ag–N 2.141 (6), 2.159(7)A; N–Ag–O 166.1(2), 170.2(2)°]. The terminal silvers provide bonding links to adjacent trimesate carboxyl oxygens between the layers while the third trimesate carboxyl group forms conventional centrosymmetric bis[(carboxylato-O,O′)silver(I)] dimers [Ag ⋯ Ag 2.847(1), 2.856(4)A], with water molecules in the axial sites for the dimer. A third compound 3, ammonium silver(I) pyrazine-2,3-dicarboxylate [NH4][Ag{C4H2N2(CO2)2}], has also been prepared using a procedure similar to that for 1 and 2. However, unlike them, it has no bonded ammines but has a distorted trigonal-planar co-ordination involving two carboxylate oxygens [Ag–O 2.333(6), 2.376(5)A] and one heteronitrogen [Ag–N 2.249(6)A], from three separate ligand molecules, giving a polymer structure.

Silver(I) carboxylates—part 11. The preparation and crystal structures of silver(I) nicotinate, ammonium silver(I) nicotinate monohydrate, ammonium silver(I) dipicolinate dihydrate, and silver(I) N-acetylanthranilate dihydrate

Abstract Two silver(I) complexes with pyridine-3-carboxylic acid (nicotinic acid) one with pyridine-2,6-dicarboxylic acid (dipicolinic acid) and one with N-acetylanthranilic acid have been prepared and their crystal structures determined by X-ray diffraction. Complex 1, catena-{[pyridine-3-carboxylato-(O,O′)]silver(I)} is based on a three-coordinate silver repeating unit [AgO, 2.258, 2.280(8) A; AgN, 2.362(10 A], with the carboxylate groups bridging alternating silvers in the convoluted sheet structure [AgAg, 3.035(1) A]. Complex 2, ammonium bis[pyridine-3-carboxylato-(itO,N,N′)]silver(I) monohydrate is also polymeric but with the three-coordinate distorted trigonal planar silver centres involving two nitrogens from the two nicotinate ligands [AgN, 2.248, 2.269(3) A]. The bridging link in the chain polymer is provided by a carboxylate oxygen [AgO, 2.342(3) A]. Partial refinement of the structure of ammonium dipicolinate dihydrate (3) indicates that it is a polymer based on a five-coordinate pentagonal planar silver centre with bonds to a nitrogen and two oxygens of a dipicolinate ligand and two carboxylate oxygens of an adjacent ligand. Complex (4), bis[(N-acetylanthranilato)-aquasilver(I)] dihydrate forms discrete centrosymmetric bis-carboxylato-(O,O′) dimers [AgO, 2.185(2), 2.207(3) A; AgAg, 2.831(2) A]. An unusual feature of the structure is the presence of waters in the axial sites of the dimer [AgO, 2.518(4) A.

Lead macrocyclic complexes : the synthesis, complex formation and X-ray crystal structures of [Pb(L1)(NO3)2] and [Pb(L2)(NO3)2] (L1 = 1,4,7,10-tetraoxa-13-azacyclopentadecane, L2 = 1,4,7,10,13-pentaoxa-16-azacyclooctadecane)

Lead(II) complexes of the 15- and 18-membered ring macrocycles 1,4,7,10- tetraoxa-13-azacyclopentadecane (L1) and 1,4,7,10,13-pentaoxa-16-azacyclooctadecane (L2) have been prepared. The stability constants for the 1 : 1 lead complexes [L1, log β 6.0(1); L2, log β 8.4(1)] have been determined potentiometrically (0. 1 M NEt4ClO4, 95% methanol). The complexes [Pb(L1)(NO3)2] and [Pb(L2)(NO3)2] have been examined by 13C NMR spectroscopy and single-crystal X-ray structural analysis. In the molecule [Pb(L1)(NO3)2] the lead(II) cation is situated 1.52 A above the plane of the macrocyclic ring. The Pb-N(1) distance of 2.465(5) A is the shortest bond to lead(II) in the structure which also exhibits two short [2.627(4) and 2.643(4) A] and two long [2.909(4) and 2.992(5) A] PbOmacrocycle distances. The presence of a stereoactive lone pair of electrons on the cation is inferred from this stereochemistry. In [Pb(L2)(NO3)2] the lead(II) cation lies in the macrocyclic cavity. As for [Pb(L1)(NO3)2], the PbN(1) distance of 2.539(9) A is the shortest bond to lead in this structure, which has in addition two short [2.694(7) and 2.697(8) A] and three long [2.877(10), 2.951(6) and 2.999(9) A] PbOmacrocycle interactions. There is no evidence for a stereoactive lone pair of electrons in this structure.

The utility of 4-aminobenzoic acid in promotion of hydrogen bonding in crystallization processes: the structures of the cocrystals with halo and nitro subsituted aromatic compounds, and the crystal structures of the adducts with 4-nitroaniline (1:1), 4-(4-nitrobenzyl)pyridine (1:2), and (4-nitrophenyl)acetic acid (1:1)

A number of molecular adducts of 4-aminobenzoic acid (4-ABA) have been prepared and characterized using infrared spectroscopy and in three cases by X-ray diffration methods. These three compounds are with 4-nitroaniline [(4-ABA) (C6H6N2O2)], 4-(4-nitrobenzyl) pyridine, [(4-ABA)2(C12H10N2O2)4], and (4-nitrophenyl)acetic acid, [(4-ABA) (C8H7NO4)]. Other compounds described are with 4-chlorobenzoic acid, [(4-ABA) (C7H5ClO2)], 4-bromobenzoic acid, [(4-ABA) (C7H5BrO2)], 4-cyanobenzoic acid, [(4-ABA) (C7H6N2)], 2-nitrobenzoic acid, [(4-ABA) (C7H5NO4)], and 3-nitrobenzoic acid, [(4-ABA) (C7H5NO4)]. All compounds have 1:1 stoichiometry except that with 4-(4-nitrobenzyl)pyridine (1:2) which is unique in being retro-stoichiometric. A review of the systematics of the 4-aminobenzoic acid adducts is also made, particularly with respect to the infrared characterization of the cocrystalline materials and prediction of their NLO potential.

Characterisation of alkaloids from some Australian Stephania (Menispermaceae) species

Chemical investigations of some Stephania species native to Australia and reportedly employed by Aboriginal people as therapeutic agents, are described. The alkaloids from the forest vines Stephania bancroftii F.M. Bailey and S. aculeata F.M. Bailey (Menispermaceae) have been isolated and characterised. The major alkaloids in the tuber of the former species are (-)-tetrahydropalmatine and (-)-stephanine, whereas these are minor components in the leaves, from which a C-7 hydroxylated aporphine has been identified. The major tuber alkaloids in S. aculeata are (+)-laudanidine, and the morphinoid, (-)-amurine, whose absolute stereochemistry has been established by X-ray structural analysis of the methiodide derivative. No significant levels of alkaloids were detected in S. japonica. Complete and unambiguous 1H and 13C NMR data are presented for these alkaloids.

Molecular Cocrystals of Carboxylic Acids. XXV The Utility of Urea in Structure Making with Carboxylic Acids and the Crystal Structures of a Set of Six Adducts with Aromatic Acids

Molecular adducts of urea with six aromatic carboxylic acids have been prepared and characterized by using X-ray diffraction methods and infrared spectroscopy. These compounds are with 5-nitrosalicylic acid [(C7H5NO5)2(CH4N2O)] (1), 3,5-dinitrosalicylic acid [(C7H4N2O7)(CH4N2O)] (2), 4-aminobenzoic acid [(C7H7NO2)2(CH4N2O)] (3), o-phthalic acid [(C8H6O4)(CH4N2O)] (4), pyrazine-2,3-dicarboxylic acid [(C4H4N2O4)(CH4N2O)] (5) and pyridine-2,6-dicarboxylic acid [(C7H5NO4)(CH4N2O)2] (6). In the majority of the adducts, all six potential interactive sites on the urea molecules are utilized in hydrogen bonding, giving polymeric structures.

Molecular Cocrystals of Carboxylic Acids. XXI. The Role of Secondary Group Interactions in Adduct Formation Between 2-Aminopyrimidine and Substituted Benzoic Acids: the Crystal Structures of the Adducts With o-Phthalic Acid, o-Nitrobenzoic Acid, o-Aminobenzoic Acid and m-Aminobenzoic Acid

The crystalline adducts of 2-aminopyrimidine (2-ap) with a series of mainly ortho-substituted benzoic acids, o-phthalic acid ( opht ) [(2-ap)( opht )] (1), 2-nitrobenzoic acid (2-nba) [(2-ap)(2-bna)2] (2), 2-aminobenzoic acid (2-aba) [(2-aba) [(2-ap)(2-aba)2] (3) and 3-aminobenzoic acid (3-aba) [(2-ap)(3-aba)] (4) have been prepared and their hydrogen-bonding motifs characterized by using single-crystal X-ray diffraction. The role of substituent groups in secondary associations with cocrystal formation is considered for the 2-aminopyrimidine system.

The preparation and crystal structure determination of a polymeric adduct of copper(II) acetate with 2-aminopyrimidine

Abstract The adduct of copper(II) acetate with 2-aminopyrimidine, catena-[(2-aminopyrimidine-N,N′)-tetrakis-μ-(ethanoato-O,O′)-dicopper(II)], has been prepared and its structure determined using X-ray diffraction. The structure is based on a tetracarboxylate-bridged dimer unit of the copper(II) acetate hydrate type [CuCu, 2.633(2) A] but is extended into an infinite zigzag polymer via the meta-related nitrogen atoms of bridging 2-aminopyrimidine molecules [CuN, 2.218(5) A].