Graham Smith

The Modulated Crystal Structure of the Molecular Adduct of 2,4,6-Trinitrobenzoic Acid with 2,6-Diaminopyridine

The 1 : 1 adduct of 2,4,6-trinitrobenzoic acid (tnba) with 2,6-diaminopyridine (2,6-dap), [(2,6-dap)+(tnba)-], has been prepared and the low-temperature crystal structure has been determined by X-ray crystallography. A modulated structure has been identified and refined by using a stacking fault model that requires reflection data to be put on three scales depending on an index condition. Crystals are triclinic, space group P1–, with Z 8 in a cell of dimensions a 13.538(3), b 14.516(4), c 16.480(4) A; α 97.17(2), β 105.69(2), γ 106.09(2)˚. The structure involves proton transfer from the tnba molecule to the 2,6-dap molecule, with the resulting pyridinium proton and an amine proton interacting with the carboxyl oxygens of the tnba molecule in a primary cyclic hydrogen-bonding association. Additional peripheral hydrogen bonding completes a two-dimensional sheet structure.

Recognition of phytotropins by the receptor for 1-N-naphthylphthalamic acid

The structure requirements for phytotropin activity and receptor binding are expressed in terms of a recognition site on the receptor with which phytotropins, including 1-N-naphthylphthalamic acid, interact. It is postulated that the site can be represented by a large region which accepts planar molecules, and is possibly electrophilic in nature. A second area is also postulated which may be lipophilic or electrophilic, together with a carboxyl acceptor. It is suggested that if the requirements of the carboxyl acceptor and adjacent area are met, then phytotropin activity will result if the candidate molecule has a configuration, or can adopt a configuration, such that a conjugated portion of the molecule can interact with the larger area. It is argued that the close relationship observed between receptor binding and effect on the gravitropic response implies that the receptors may be directly involved in the gravitropic response mechanism.

Molecular Cocrystals of Aromatic Carboxylic Acids with 1,1-Diethylurea: Synthesis and the Crystal Structures of a Series of Nitro-Substituted Analogues

Molecular adducts of 1,1-diethylurea with the nitro-substituted aromatic carboxylic acids 2-nitrobenzoic acid, [(C7H5NO4)(C5H12N2O)] (1), 3-nitrobenzoic acid, [(C7H5NO4)(C5H12N2O)] (2), 4-nitrobenzoic acid, [(C7H5NO4)2(C5H12N2O)] (3), 3,5-dinitrobenzoic acid, [(C7H4N2O6)(C5H12N2O)] (4), 5-nitrosalicylic acid, [(C7H5NO5)(C5H12N2O)] (5) and 3,5-dinitrosalicylic acid, [(C7H4N2O7)(C5H12N2O)] (6), have been prepared and characterized by using infrared spectroscopy, and, in the case of four of these [(1), (4), (5) and (6)], by single-crystal X-ray diffraction methods. In all examples, primary cyclic hydrogen-bonding interactions are found between the amide group of the substituted urea and the carboxylic acid group of the acid, while further peripheral associations result predominantly in simple chain polymeric structures, and in one case [adduct (1)], a cyclic tetramer. The crystal structure of the parent 1,1-diethylurea has also been determined, revealing a cyclic hydrogen-bonded tetramer which forms into a chain polymer by weak hydrogen-bonding associations.

Reactions of gallium hydrides with 1,4-di-t-butyl-1,4-diazabutadiene; subvalent and hydrometallation products

Reaction of LiGaH4 and gallium metal with 1,4-di-t-butyl-1,4-diazabutadiene (dbdab) in diethyl ether at room temperature yields the monomeric, formally gallium(II) species [Ga(dbdab)2], (1), previously prepared using metal vapours, and GaH3·NMe3 with dbdab in hexane at –80 °C yields the novel hydrogallation product [{H2Ga}2{µ-N(But)CH2}2], (2) which has magnetically distinct geminal hydrides (2JHH 44 Hz) in agreement with the crystal structure ( 2.013A, 1.56A) and IR data (νGa–H 1920, 1870 cm–1).

Polymeric anhydrous sodium 2-aminobenzensulfonate

The crystal structure of anxadhydroxadus sodium 2-aminoxadbenzenexadsulfonate, [Na(C6H6NO3S)]n, reveals the presence of a two-dimensional sandwich polymer structure based on a distorted octahedral six-coordinate NaO5N repeating unit. O-Donor atoms are from five different sulfonate groups [Na—O = 2.294u2005(3)–2.532u2005(3)u2005A] and an amine nitroxadgen [Na—N = 2.572u2005(3)u2005A], completing a six-membered chelate ring including Na. Hydroxadgen bonds also stabilize the core structure. The outer layers of the sandwich comprise the unassociated benzene rings.

1-(Diphenylphosphino)-4-(diphenylphosphinoyl)butane

The structure of the title `half oxide, C28H28P2O, (I), is found to be isomorphous with the previously determined `full oxide, 1,4-bisxad(dixadphenylxadphosphinoyl)xadbutane. A significant feature is an apparent shortening of the P—O bond distance [1.379u2005(3)u2005A] in (I) compared to the `full oxide [1.481u2005(2)u2005A], a result consistent with other known phosphine `partial oxides.

Proton-transfer compounds featuring the unusual 4-arsonoanilinium cation from the reaction of (4-aminophenyl) arsonic acid with strong organic acids

Abstract The crystal structures of the 1:1 proton-transfer compounds of (4-aminophenyl)arsonic acid (p-arsanilic acid) with the strong organic acids, 2,4,6-trinitrophenol (picric acid), 3,5-dinitrosalicylic acid, (3-carboxy-4-hydroxy)benzenesulfonic acid (5-sulfosalicylic acid) and toluene-4-sulfonic acid have been determined at 200 K and their hydrogen–bonding patterns examined. The compounds are, respectively, anhydrous 4-arsonoanilinium 2,4,6-trinitrophenolate (1), the hydrate 4-arsonoanilinium 2-carboxy-4,6-dinitrophenolate monohydrate (2), the hydrate 4-arsonoanilinium (3-carboxy-4-hydroxy)benzenesulfonate monohydrate (3) and the partial solvate 4-arsonoanilinium toluene-4-sulfonate 0.8 hydrate (4). The asymmetric unit of 2, a phenolate, comprises two independent but conformationally similar cation-anion pairs and two water molecules of solvation, and in all compounds, extensive inter-species hydrogen–bonding interactions involving arsono O–H···O and anilinium N–H···O hydrogen–bonds generate three-dimensional supramolecular structures. In the cases of 1 and 2, the acceptors include phenolate and nitro O-atom acceptors, with 3 and 4, additionally, sulfonate O-atom acceptors, and with the hydrates 2–4, the water molecules of solvation. A feature of the hydrogen–bonding in 3 is the presence of primary chains extending along (010) through centrosymmetric cyclic R22(8) motifs together with conjoined cyclic R34(12) motifs, which include the water molecule of solvation. The primary hydrogen–bonding in the substructure of 4 involves homomolecular cation–cation arsono O–H···O interactions forming columns down the crystallographic four-fold axis of the unit cell.

Zwitterionic 5-amino-2-naphthalenesulfonic acid

The crystal structure of 5-amino-2-naphthalenexadsulfonic acid (1,6-Cleves acid), C10H9NO3S, shows the presence of a sulfonate–aminium group zwitterion, viz. 5-ammonio-2-naphthalenexadsulfonate. All aminium H atoms are involved in head-to-tail intermolecular hydrogen-bonding interactions with separate sulfonate O-atom acceptors, giving a three-dimensional framework polymer structure.

The crystal structures of six polybromo carvones

The crystal structures of six polybromo carvones have been determined by single-crystal X-ray diffraction. These are the three previously reported isomeric tetrabromo carvones, (1S,3S,4R,8R)-1,3,8,9-tetrabromo-p-menthan-2-one (4), (1S,3S,4R,8S)-1,3,8,9-tetrabromo-p-menthan-2-one (5) and (1R,3S,4R,8R)-1,3,8,9-tetrabromo-p-menthan-2-one (12), two tribromo derivatives, (1S, 4R, 8R)-1,8,9-tribromo-p-menthan-2-one (10) and (1S,4R, 8S)-1,8,9-tribromo- p-menthan-2-one (11) [all derived from (R)- carvone (1)], together with a pentabromo derivative, (1S, 3S, 4R, 6R, 8R)- 1,3,6,8,9- pentabromo-p-menthan-2-one (7) [derived from (S)-carvone ent-(1)]. In all examples, the stereochemistry agrees with that predicted from the synthetic pathway, while with one [the (1R, 3S, 4R, 8R)- tetrabromide (12)] a distorted twist-chair conformation is found.