Daniel E. Lynch

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.

Geometry of the 2-aminoheterocyclic–carboxylic acid R22(8) graph set: implications for crystal engineering

The geometry of the R2(2)(8) graph set formed between a 2-aminoheterocyclic ring containing an Nsp2 atom (in the 1-position of the ring) and a carboxylic acid has been studied. Collating data from known co-crystal structures containing five- and six-membered heterocyclic rings from the Cambridge Structural Database revealed unexpected differences between two kinds of non-hydrogen contact distances, and between specific bond distances and angles of the heterocycle. Not only were the interatomic non-hydrogen distances between the N atoms (heterocycle) and O atoms (carboxylate) asymmetric, but also the 2-amino N atom (N21) to the heterocyclic C atom (C2) bond was shorter than the C2 to N1sp2 bond. However, this shortening of the C2-N21 bond was not observed in the examples where N21 was substituted with a non-H atom. For the six-membered rings the data also showed that as the C2-N21 bond shortened the N1-C2-N21 bond angle increased.

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.

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.

2,4-Bis[4-(N,N-dibutylamino)phenyl] squaraine: X-ray crystal structure of a centrosymmetric dye and the second-order non-linear optical properties of its non-centrosymmetric Langmuir–Blodgett films

Crystals of the title compound exist as a green monoclinic phase [space group P21/c with a= 9.046(1), b= 19.615(2), c= 9.055(1)A, β= 116.107(5)°, Z= 2] and a purple triclinic phase. The chromophore is both planar and centrosymmetric and its dimensions indicate a tendency towards a quinoidal structure with extensive delocalisation. The Langmuir–Blodgett (LB) films show two types of aggregation with absorption maxima at 655 nm and 540 nm. These monolayers also exhibit strong second harmonic generation (SHG) comparable to the intensity from films of hemicyanine dyes. The anomalous non-linear optical properties are attributed to a serendipitous non-centrosymmetric packing arrangement within the films and to an intermolecular charge transfer contribution to the bulk second-order susceptibility.

Metal phenoxyalkanoic acid interactions—36. The preparation and crystal structures of tetraaquabis(2-phenoxybenzoato)nickel(ii) dihydrate, diaquabis(4-fluorophenoxyacetato)zinc(ii), catena-diaquabis(phenoxyacetato)cobalt(ii) and tetrakis-μ-[(pentafluorophenoxy)acetato(o,o′)] bis[aquacopper(ii)]

The structures of four complexes involving divalent first-row transition metals and phenoxy substituted carboxylic acids have been determined by X-ray diffraction. These are tetraaquabis(2-phenoxybenzoato)nickel(II) dihydrate (1), diaquabis(4-fluorophenoxyacetato)zinc(II) (2), diaquabis(phenoxyacetato)cobalt(II) (3) and tetrakis-μ-(pentafluorophenoxyacetato)bis[aquacopper(II)] (4). Complex 1 is regular octahedral with trans-related unidentate carboxylate [Ni-O (carboxylate) 2.031(1) A] and four waters [Ni-O 2.049, 2.104(2) A]. Complex 2 has a skew trapezoidal bipyramidal stereochemistry, involving four oxygens from two asymmetric bidentate carboxylates [Zn-O 2.107, 2.332(3) A] and two waters [Zn-O 1.989(4) A]. The polymeric complex 3 is isomorphous and isostructural with the manganese(II) analogue, with centrosymmetric octahedral CoO stereochemistry comprising four bonds to carboxylate oxygens (both bridging) [Co-O 2.076, 2.087(3) A] and two to waters [Co-O 2.134(3) A]. Complex 4 is a pseudo-centrosymmetric tetracarboxylate bridged dimer of the copper(II) acetate hydrate type with a Cu-Cu separation of 2.644(4) A. Bond distances to copper are 1.96(1) (average, equatorial) and 2.15(1) A (average, axial, to water).

Preparation and crystal structure of polymeric ammonium silver(I) citrate hydrate, {NH4[Ag2(C6H5O7)(H2O)]}n

Abstract The polymeric silver(I) citrate complex {NH4[Ag2(C6H5O7)(H2O)]}n has been synthesized and its structure determined by X-ray diffraction methods and refined to R = 0.046 for 2520 observed reflections. This compound represents the first reported complexes of a silver(I) citrate. In the structural repeating unit there are two independent but different carboxylato(O,O′) bridged silver dimers [AgAg, 2.845, 2.846(1) A] linked into infinite linear chains by the terminal carboxyl groups of the citrato(3 −) ligands. With one dimer, the AgO (axial) bonds are to oxygens from the sub-terminal carboxylate groups of two independent silver citrate chains. The second silver dimer also forms links with adjacent chains via axial AgO(carboxylate) bonds, while in the remaining axial sites are water molecules. The mean AgO distance is 2.377(4) A. The result is a novel convoluted anionic chain sheet structure.

A Neutral Donor-Acceptor p-Stack: Solid-State Structures of 1 : 1 Pyromellitic Diimide-Dialkoxynaphthalene Cocrystals

Pyromellitic diimide forms orange-coloured cocrystals of 1 : 1 stoichiometry with dialkoxynaphthalene derivatives. The solid-state structures of two examples are presented. The cocrystal formed with 2,6-dimethoxynaphthalene presents vertical stacks of alternating π-rich and π-deficient subunits with the long axes of the respective components approximately parallel. Investigation of the packing in the cocrystal also reveals a stabilizing array of hydrogen bonds between the components of adjacent stacks. Cocrystallization with 1,5-[2-(2-hydroxyethoxy)ethoxy]naphthalene, a derivative bearing hydroxy terminated ethyleneoxy chains, gives rise to an altered structural arrangement. Alternating donor- acceptor stacks once again dominate the structure but adopt a geometry where the long axes of the constituents are essentially perpendicular. Hydrogen-bonding interactions result in the formation of continuous non-covalently linked columns of donor and acceptor subunits by linking the terminal hydroxy functions of the naphthalene component to the imide protons. The structural preferences revealed by these solid-state analyses indicate that these complexes are useful prototypes of more complex neutral supramolecular assemblies.

Molecular co-crystals of carboxylic acids, part 29. The effect of competitive interactions on adduct formation involving 2-aminopyrimidine: the crystal structure of the 1∶1 adduct of 2-aminopyrimidine with indole-2-carboxylic acid

The crystal structure of the 1∶1 adduct of 2-aminopyrimidine with indole-2-carboxylic acid has been determined by single crystal X-ray diffraction, revealing a novel interactive mode. The utility of 2-aminopyrimidine in formation of stable hydrogen-bonded networks with carboxylic acids is discussed and the modes of interaction are reviewed.

Conformational Comparisons Between Phenoxyacetic Acid Derivatives in Adducts and in the Free Form

Six molecular complexes containing the herbicidally active (2,4-dichlorophenoxy)acetic acid (2,4-d) and (2,4,5-trichlorophenoxy)acetic acid (2,4,5-t) have been prepared and studied by using single-crystal X-ray diffraction techniques. These adduct structures are 2,4-d with 4,4′-dipyridine (2 : 1 complex), and 2,4,5-t with respectively 5-nitroquinoline (1 : 1), 4,4′-dipyridine (2 : 1), 2-amino-2-thiazoline (1 : 1), 2-aminobenzothiazole (1 : 1) and 2-amino-5-ethyl-1,3,4-thiadiazole (1 : 1). The conformations of the phenoxyacetic acid molecules were found to be either synclinal (in three cases) or antiperiplanar (in the other three cases). A general review is also made about the conformational aspects of previously reported adducts of phenoxyacetic acid derivatives and how they compare to their free acid structures.