Urs D. Wermuth

5-Nitrosalicylic Acid and its Proton-Transfer Compounds with Aliphatic Lewis Bases

The crystal structures of the proton-transfer compounds of 5-nitrosalicylic acid (5-nsa) with morpholine (morph), hexamethylenetetramine (hmt), and ethylenediamine (en) have been determined and their solid-state packing structures described. The compounds are [(morph)+(5-nsa)–] 1, [(hmt)+(5-nsa)–·H2O] 2, and [(en)2+2(5-nsa)–·H2O] 3. In all compounds, protonation of the hetero-nitrogen of the Lewis base occurs. With 1, the 5-nsa anions and the morpholine cations lie, respectively, in or across crystallographic mirror planes and are linked within the planes by hydrogen-bonding interactions through the aminium group and the carboxylic and phenolic oxygens of the anionic 5-nsa species giving a two-dimensional sheet polymer. Compound 2 is an unusual structure with the planar 5-nsa anions lying within pseudo mirror planes and cyclically linked by duplex water bridges through a single carboxylate oxygen into centrosymmetric dimers. The hmt cation molecules are disordered across the pseudo mirror and are strongly linked by N+–H···O hydrogen bonds only to the water molecules with peripheral weak hmt C–H···O hydrogen bonds extending the dimer within and between the dimer planes. Compound 3 is a network polymer comprised of the 5-nsa anions, the en dianions, and the water molecule in an extensive hydrogen-bonded structure.

Structure-Making with 3,5-Dinitrosalicylic Acid. II. The Proton-Transfer Compounds of 3,5-Dinitrosalicylic Acid with the Monocyclic Heteroaromatic Amines

The crystal structures of the proton-transfer compounds of 3,5-dinitrosalicylic acid (dnsa) with a series of common monocyclic heteroaromatic amines (pyridine, 4-cyanopyridine, pyridine-4-carboxylic acid, 2,6-diaminopyridine, and 2-aminopyrimidine) have been determined and the hydrogen-bonding associations in each analyzed. The compounds are the adduct [(C5H6N)+(dnsa)–· (dnsa)] (1), the 1 : 1 salts [(C6H5N2)+(dnsa)–] (2), [(C6H6NO2)+(dnsa)–] (3), [(C5H8N3)+(dnsa)–] (4), and the 2 : 2 ethanol hemi-solvate [2(C4H6N3)+·2(dnsa)–· 0.5(EtOH)] (5). With all compounds, protonation of the hetero-nitrogen atom occurs with subsequent hydrogen bonding to the oxygen atoms of the functional groups of the dnsa anions, resulting in the formation of relatively simple linear or chain polymer associations. Compound (1) represents a rare example of other than a 1 : 1 association, and the first example of a 2 : 1 (dnsa/amine) type, with the unusual presence of an additional adduct molecule of dnsa in the structure.

Structure-making with 3,5-dinitrosalicylic acid. I. The proton-transfer compounds of 3,5-dinitrosalicylic acid with a series of aliphatic amines

The crystal structures of the proton-transfer compounds of 3,5-dinitrosalicylic acid (dnsa) with ammonia (two polymorphs) and a series of common aliphatic amines (methylamine, triethylamine, hexamethylenetetramine and ethylenediamine) have been determined and the hydrogen-bonding associations in each analysed. The compounds are [(NH4)+(dnsa)-] (1A, 1B), [(CH3NH3)+(dnsa)-] (2), [{(C2H5)3NH}+(dnsa)-] (3), [(C6H12 N4H)+(dnsa)-] (4) and [{(CH2 NH3) 2}2+(dnsa)2-·H2O] (5). It is of interest that with hydrate (5) the phenolic proton of dnsa is also lost on reaction, giving a rare dianionic species. In all compounds, protonation of the amino group of the Lewis base occurs, with subsequent hydrogen bonding via this and other hydrogens variously to the carboxylic, nitro and phenolic oxygens of dnsa, and in the case of (5), the lattice water. The result is the formation of simple linear associations with the tertiary amines, or network polymers with the less-substituted examples. Short intramolecular hydrogen bonds between the phenolic group and the carboxylate group are found in all compounds except (5), with the proton localized on the carboxylate oxygen rather than on the phenolic oxygen, but in the case of (3), delocalized within the hydrogen bond.

Interactions of Aromatic Carboxylic Acids with Quinolin-8-ol (Oxine): Synthesis and the Crystal Structures of the Proton-Transfer Compounds with the Nitro-Substituted Benzoic Acids

Proton-transfer compounds of quinolin-8-ol (oxine) with the nitro-substituted aromatic carboxylic acids 2-nitrobenzoic acid, [(C9H8NO+)(C7H4NO4–)·H2O] (1), 3-nitrobenzoic acid, [(C9H8NO+)(C7H4NO4)–] (2), 4-nitrobenzoic acid, [(C9H8NO+)(C7H4NO4–)(C7H5NO4)] (3), 3,5-dinitrobenzoic acid, [(C9H8NO+)2(C7H3N2O6–)2·3H2O] (4), 5-nitrosalicylic acid, [(C9H8NO+) (C7H4NO5–)] (5) and 3,5-dinitrosalicylic acid, [(C9H8NO+)(C7H3N2O7–)] (6) have been prepared and characterized by using both infrared spectroscopy and single-crystal X-ray diffraction methods [(3), (4) and (6)]. In all compounds, protonation of the quinoline nitrogen occurs together with primary hydrogen-bonding interactions involving this group and the carboxylate group of the acid, while further peripheral associations, in the case of the trihydrate (4), also involving the water molecules, result predominantly in simple chain polymeric structures.

Molecular recognition in proton-transfer compounds of brucine with achiral substituted salicylic acid analogues

The 1:1 proton-transfer brucinium compounds from the reaction of the alkaloid brucine with 5-nitrosalicylic acid, 3,5-dinitrosalicylic acid, and 5-sulfosalicylic acid, namely anhydrous brucinium 5-nitrosalicylate (1), brucinium 3,5-dinitrosalicylate monohydrate (2), and brucinium 5-sulfosalicylate trihydrate (3) have been prepared and their crystal structures determined by X-ray crystallography. All structures further demonstrate the selectivity of brucine for meta-substituted benzoic acids and comprise three-dimensional hydrogen-bonded framework polymers. Two of the compounds (1 and 3) have the previously described undulating brucine sheet host-substructures which incorporate interstitially hydrogen-bonded salicylate anion guest species and additionally in 3 the water molecules of solvation. The structure of 2 differs in having a three-centre brucinium–salicylate anion bidentate N+–H···O(carboxyl) hydrogenbonding association linking the species through interstitial associations involving also the water molecules of solvation. A review of the crystallographic structural literature on strychnine and brucine is also given.

A second crystal polymorph of anilinium picrate

The crystal structure of a second monoclinic polymorph of anilinium picrate shows a three-dimensional hydrogen-bonded polymer with strong primary interspecies interactions involving the proximal phenolate and adjacent nitro group O-atom acceptors and separate anilinium H-atom donors in two cyclic R (6) associations. Other nitro-O-anilinium-H hydrogen bonds together with heteromolecular interactions are also present.

Two pseudopolymorphic hydrates of brucine: brucine–water (1/4) and brucine–water (1/5.25) at 130 K

The structures of two pseudopolymorphic hydrates of brucine, C 23 H 26 N 2 O 4 ·4H 2 O, (I), and C 23 H 26 N 2 O 4 ·5.25H 2 O, (II), have been determined at 130 K. In both (I) and (II) (which has two independent brucine molecules together with 10.5 water molecules of solvation in the asymmetric unit), the brucine molecules form head-to-tail sheet substructures, which associate with the water molecules in the interstitial cavities through hydrogen-bonding associations and, together with water-water associations, give three-dimensional framework structures.

Molecular Cocrystals of Aromatic Carboxylic Acids with Unsymmetrically Substituted Ureas. The Structures of Phenylurea and the 1 : 1 Adducts of Phenylurea with a Series of Nitro-Substituted Acids

The crystal structure of phenylurea (1), [(C7H8N2O)], has been determined and revealed a simple cyclic dimer involving hydrogen bonding between the two nitrogen atoms of one molecule and the oxygen atom of a second molecule. The system is completed by a hydrogen bond between the non-substituted nitrogen atom of a third molecule and the oxygen atom of the second molecule to form a chain polymer. The 1 : 1 molecular adducts of phenylurea with 2-nitrobenzoic acid, [(C7H5NO4)(C7H8N2O)] (2), 3-nitrobenzoic acid, [(C7H5NO4)(C7H8N2O)] (3), 3,5-dinitrobenzoic acid, [(C7H4N2O6)(C7H8N2O)] (4), 2,4,6-trinitrobenzoic acid, [(C7H3N3O8)(C7H8N2O)] (5), 5-nitrosalicylic acid, [(C7H5NO5)(C7H8N2O)] (6), and 3,5-dinitrosalicylic acid, [(C7H4N2O7)(C7H8N2O)] (7) have been prepared and characterized by infrared spectroscopy and, for compounds (2), (4), (5) and (6), by single crystal X-ray diffraction methods. The adduct involving phenylurea and 4-nitrobenzoic acid could not be isolated from this system. In all examples, cyclic hydrogen-bonding interactions are found between the phenylurea and the carboxylic acid groups. All display further peripheral hydrogen bond associations that result in the formation of predominantly simple chain polymeric structures.

Brucinium toluene-4-sulfonate trihydrate at 130 K

The low-temperature (130 K) structure of the 1:1 proton-transfer compound of brucine with toluene-4-sulfonic acid (systematic name: 2,3-dimethoxy-10-oxostrychnidinium toluene-4-sulfonate trihydrate), C23H27N2O4+·C7H7O3S-·3H2O, has been determined. The asymmetric unit contains two cations, two anions and six molecules of water. Brucinium cations form the familiar undulating head-to-tail ribbon structures, which associate with the toluene-4-sulfonate anions and the water molecules in the interstitial cavities through hydrogen-bonding associations involving all available donor and acceptor atoms on all species. The result is a framework polymer structure.

Hydrogen bonding in 1:1 proton-transfer compounds of 5-sulfosalicylic acid with 4-X-substituted anilines (X = F, Cl or Br).

The crystal structures of three proton-transfer compounds of 5-sulfosalicylic acid (3-carboxy-4-hydroxybenzenesulfonic acid) with 4-X-substituted anilines (X = F, Cl and Br), namely 4-fluoroanilinium 5-sulfosalicylate (3-carboxy-4-hydroxybenzenesulfonate) monohydrate, C6H7FN+.C7H5O6S-.H2O, (I), 4-chloroanilinium 5-sulfosalicylate hemihydrate, C6H7ClN+.C7H5O6S-.0.5H2O, (II), and 4-bromoanilinium 5-sulfosalicylate monohydrate, C6H7BrN+.C7H5O6S-.H2O, (III), have been determined. The asymmetric unit in (II) contains two formula units. All three compounds have three-dimensional hydrogen-bonded polymeric structures in which both the water molecule and the carboxylic acid group are involved in structure extension. With both (II) and (III), which are structurally similar, the common cyclic R(2)(2)(8) dimeric carboxylic acid association is present, whereas in (I), an unusual cyclic R(3)(3)(8) association involving all three hetero-species is found.