Dimethyl Sulfoxide Monosolvate Research Articles

Architecture of the rings of 5-arylidenerhodanine derivatives versus P-gp inhibition.

5-Arylidene derivatives of rhodanine show various biological activities. The new crystal structures of five derivatives investigated towards ABCB1 efflux pump modulation are reported, namely, 2-[5-([1,1'-biphenyl]-4-ylmethylidene]-4-oxo-2-thioxothiazolidin-3-yl)acetic acid dimethyl sulfoxide monosolvate, C18H13NO3S2·C2H6OS (1), 4-[5-([1,1'-biphenyl]-4-ylmethylidene]-4-oxo-2-thioxothiazolidin-3-yl)butanoic acid, C20H17NO3S2 (2), 5-[4-(benzyloxy)benzylidene]-2-thioxothiazolidin-4-one, C17H13NO2S2 (3), 4-{5-[4-(benzyloxy)benzylidene]-4-oxo-2-thioxothiazolidin-3-yl}butanoic acid, C21H19NO4S2 (4), and 5-[4-(diphenylamino)benzylidene]-2-thioxothiazolidin-4-one, C22H16N2OS2 (5). Compounds 1 and 3-5 crystallize in the triclinic space group P-1, while 2 crystallizes in the monoclinic space group P21/n, where the biphenyl moiety is observed in two positions (A and B). Two molecules are present in the asymmetric unit of 5 and, for the other four compounds, there is only one molecule; moreover, 1 crystallizes with one dimethyl sulfoxide molecule. The packing of the molecules containing a carboxyl group (1, 2 and 4) is determined by O-H...O hydrogen bonds, while in the other two compounds (3 and 5), the packing is determined by N-H...O hydrogen bonds. Additionally, induced-fit docking studies have been performed for the active compounds to investigate their putative binding mode inside the human glycoprotein P (P-gp) binding pocket.

5-([(Z)-Meth-oxy-imino]{2-[(2-methyl-phen-oxy)meth-yl]phen-yl}meth-yl)-1,3,4-oxa-diazole-2(3H)-thione dimethyl sulfoxide monosolvate.

The title compound, C18H17N3O3S·C2H6OS, crystallizes in the monoclinic space group P21 /c. In the crystal, C 1 1(9) chains of C-H⋯O inter-actions are formed, propogating in the c-axis direction. The N-H hydrogen atom forms a strong hydrogen bond with the oxygen atom of a DMSO solvate mol-ecule.

First crystal structure of a Pigment Red 52 compound: DMSO solvate hydrate of the monosodium salt.

Pigment Red 52, Na2[C18H11ClN2O6S], is an industrially produced hydrazone-laked pigment. It serves as an inter-mediate in the synthesis of the corresponding Ca2+ and Mn2+ salts, which are used commercially for printing inks and lacquers. Hitherto, no crystal structure of any salt of Pigment Red 52 is known. Now, single crystals have been obtained of a dimethyl sulfoxide solvate hydrate of the monosodium salt of Pigment Red 52, namely, monosodium 2-[2-(3-carb-oxy-2-oxo-1,2-di-hydro-naphthalen-1-yl-idene)hydrazin-1-yl]-5-chloro-4-methyl-benz-ene-sulfonate dimethyl sulfoxide monosolvate monohydrate, Na+·C18H12ClN2O6S-·H2O·C2H6OS, obtained from in-house synthesized Pigment Red 52. The crystal structure was determined by single-crystal X-ray diffraction at 173 K. In this monosodium salt, the SO3 - group is deprotonated, whereas the COOH group is protonated. The residues form chains via ionic inter-actions and hydrogen bonds. The chains are arranged in polar/non-polar double layers.

Crystal structure and Hirshfeld surface analysis of 2-[(2-oxo-2H-chromen-4-yl)-oxy]acetic acid dimethyl sulfoxide monosolvate.

The title compound, C11H8O5·(CH3)2SO, is a new coumarin derivative. The asymmetric unit contains two coumarin mol-ecules (A and B) and two di-methyl-sulfoxide solvent mol-ecules (A and B). The dihedral angle between the pyran and benzene rings in the chromene moiety is 3.56 (2)° for mol-ecule A and 1.83 (2)° for mol-ecule B. In mol-ecule A, the dimethyl sulfoxide sulfur atom is disordered over two positions with a refined occupancy ratio of 0.782 (5):0.218 (5). In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds, forming chains running along the c-axis direction. The chains are linked by C-H⋯O hydrogen bonds, forming layers parallel to the ac plane. In addition, there are also C-H⋯π and π-π inter-actions present within the layers. The inter-molecular contacts in the crystal have been analysed using Hirshfeld surface analysis and two-dimensional fingerprint plots, which indicate that the most important contributions to the packing are from H⋯H (33.9%) and O⋯H/H⋯O (41.2%) contacts.

Crystal structure and Hirshfeld surface analysis of 4-[4-(1H-benzo[d]imidazol-2-yl)phen-oxy]phthalo-nitrile dimethyl sulfoxide monosolvate.

This work presents the synthesis and structural characterization of [4-(1H-benzo[d]imidazol-2-yl)phen-oxy]phthalo-nitrile, a phthalo-nitrile derivative carrying a benzimidazole moiety. The compound crystallizes as its dimethyl sulfoxide monosolvate, C21H12N4O·(CH3)2SO. The dihedral angle between the two fused rings in the heterocyclic ring system is 2.11 (1)°, while the phenyl ring attached to the imidazole moiety is inclined by 20.7 (1)° to the latter. In the crystal structure, adjacent mol-ecules are connected by pairs of weak inter-molecular C-H⋯N hydrogen bonds into inversion dimers. N-H⋯O and C-H⋯O hydrogen bonds with R 2 1(7) graph-set motifs are also formed between the organic mol-ecule and the disordered dimethyl sulfoxide solvent [occupancy ratio of 0.623 (5):0.377 (5) for the two sites of the sulfur atom]. Hirshfeld surface analysis and fingerprint plots were used to investigate the inter-molecular inter-actions in the crystalline state.

Crystal structure and Hirshfeld surface analysis of (E)-2-(5-bromo-2-hy-droxy-benzyl-idene)hydrazine-carbo-thio-amide di-methyl sulfoxide monosolvate.

The mol-ecule of the title Schiff base, C8H8BrN3OS·C2H6OS, which crystallizes as a di-methyl sulfoxide (DMSO) monosolvate, displays an E configuration with respect to the C=N bond, with a dihedral angle of 14.54 (11)° between the benzene ring and the mean plane of the N-N-C(N)=S unit. In the crystal, mol-ecules are linked by N-H⋯O hydrogen bonds, forming chains propagating along the b-axis direction. Within the chains there are R23(11) ring motifs, which are reinforced by C-H⋯ODMSO hydrogen bonds enclosing secondary R12(6) and R23(9) loops. The chains are linked by O-Hhydrox-yl⋯S hydrogen bonds, forming layers parallel to (011). Inversion-related layers are linked by short Br⋯Br inter-actions [3.5585 (5) Å], forming slabs parallel to (011). The inter-molecular inter-actions have been investigated using Hirshfeld surface studies and two-dimensional fingerprint plots. The crystal structure of the unsolvated form of the title compound has been reported previously [Kargar et al. (2010). Acta Cryst. E66, o2999], and its solid-state structure is compared with that of the title solvated form.

Crystal structures of hibiscus acid and hibiscus acid dimethyl ester isolated from Hibiscus sabdariffa (Malvaceae).

The biologically active title compounds have been isolated from Hibiscus sabdariffa plants, hibiscus acid as a dimethyl sulfoxide monosolvate [systematic name: (2S,3R)-3-hy-droxy-5-oxo-2,3,4,5-tetra-hydro-furan-2,3-di-carb-oxy-lic acid dimethyl sulfoxide monosolvate], C6H6O7·C2H6OS, (I), and hibiscus acid dimethyl ester [systematic name: dimethyl (2S,3R)-3-hy-droxy-5-oxo-2,3,4,5-tetra-hydro-furan-2,3-di-carboxyl-ate], C8H10O7, (II). Compound (I) forms a layered structure with alternating layers of lactone and solvent mol-ecules, that include a two-dimensional hydrogen-bonding construct. Compound (II) has two crystallographically independent and conformationally similar mol-ecules per asymmetric unit and forms a one-dimensional hydrogen-bonding construct. The known absolute configuration for both compounds has been confirmed.

Crystal structure of 16-ferrocenylmethyl-3β-hydroxy-estra-1,3,5(10)-trien-17-one: a potential chemotherapeutic drug.

A new ferrocene complex, 16-ferrocenylmethyl-3β-hy-droxy-estra-1,3,5(10)-trien-17-one dimethyl sulfoxide monosolvate, [Fe(C5H5)(C24H27O2)]·C2H6OS, has been synthesized and structurally characterized by single-crystal X-ray diffraction techniques. The mol-ecule crystallizes in the space group P21 with one mol-ecule of dimethyl sulfoxide. A hydrogen bond links the phenol group and the dimethyl sulfoxide O atom, with an O⋯O distance of 2.655 (5) Å. The ferrocene group is positioned in the β face of the estrone moiety, with an O-C-C-C torsion angle of 44.1 (5)°, and the carbonyl bond length of the hormone moiety is 1.216 (5) Å, typical of a C=O double bond. The average Fe-C bond length of the substituted Cp ring [Fe-C(Cp*)] is similar to that of the unsubstituted one [Fe-C(Cp)], i.e. 2.048 (3) versus 2.040 (12) Å. The structure of the complex is compared with those of estrone and eth-oxy-methyl-estrone.

One-pot green synthesis of biologically relevant novel spiro[indolin-2-one-3,4'-pyrano[2,3-c]pyrazoles] and studies on their spectral and X-ray crystallographic behaviors.

Syntheses via green route and single-crystal X-ray structural investigations have been carried out for three spiro[indolin-2-one-3,4'-pyrano[2,3-c]pyrazole] derivatives, 6'-amino-2-oxo-3'-propyl-2'H-spiro[indoline-3,4'-pyrano[2,3-c]pyrazole]-5'-carbonitrile dimethyl sulfoxide monosolvate (5a), 6'-amino-5-fluoro-2-oxo-3'-propyl-2'H-spiro[indoline-3,4'-pyrano[2,3-c]pyrazole]-5'-carbonitrile dimethyl sulfoxide monosolvate (5b) and methyl 6'-amino-5-cyano-1-methyl-2-oxo-3'-propyl-2'H-spiro[indoline-3,4'-pyrano[2,3-c]pyrazole]-3'-carboxylate 0.25 hydrate (5c), respectively. Compounds (5a) and (5b) crystallize in the triclinic space group P\bar 1, whereas compound (5c) crystallizes in the monoclinic space group C2/c. In molecules (5a) and (5b) all the rings are practically flat, while in (5c), the heterocyclic pyran ring adopts a flattened-boat conformation. In (5a) and (5b) the cyanide group is oriented in a (-ap) conformation, while the amino group is oriented in a (+ap) conformation with a pyran ring, but in (5c) both the cyanide and amino groups are oriented in a (-ap) conformation with the pyran ring. In the crystal structure of (5a) and (5b), the molecules are linked by an elaborate system of N-H...O and N-H...N hydrogen bonds to generate a zigzag-like construct. In (5c) molecules are linked by N-H...O hydrogen bonds, thereby generating extended chains. The present communication focuses on the detailed and comparative information about spectral behaviors, single-crystal X-ray crystallographic properties and solid-state supramolecular architectures of these synthesized compounds of potential biological interests.

Structural Properties, Order–Disorder Phenomena, and Phase Stability of Orotic Acid Crystal Forms

Orotic acid (OTA) is reported to exist in the anhydrous (AH), monohydrate (Hy1), and dimethyl sulfoxide monosolvate (SDMSO) forms. In this study we investigate the (de)hydration/desolvation behavior, aiming at an understanding of the elusive structural features of anhydrous OTA by a combination of experimental and computational techniques, namely, thermal analytical methods, gravimetric moisture (de)sorption studies, water activity measurements, X-ray powder diffraction, spectroscopy (vibrational, solid-state NMR), crystal energy landscape, and chemical shift calculations. The Hy1 is a highly stable hydrate, which dissociates above 135 °C and loses only a small part of the water when stored over desiccants (25 °C) for more than one year. In Hy1, orotic acid and water molecules are linked by strong hydrogen bonds in nearly perfectly planar arranged stacked layers. The layers are spaced by 3.1 Å and not linked via hydrogen bonds. Upon dehydration the X-ray powder diffraction and solid-state NMR peaks become broader, indicating some disorder in the anhydrous form. The Hy1 stacking reflection (122) is maintained, suggesting that the OTA molecules are still arranged in stacked layers in the dehydration product. Desolvation of SDMSO, a nonlayer structure, results in the same AH phase as observed upon dehydrating Hy1. Depending on the desolvation conditions, different levels of order–disorder of layers present in anhydrous OTA are observed, which is also suggested by the computed low energy crystal structures. These structures provide models for stacking faults as intergrowth of different layers is possible. The variability in anhydrate crystals is of practical concern as it affects the moisture dependent stability of AH with respect to hydration.

The crystal structures of three clozapinium salts: different mol-ecular configurations, and supra-molecular assembly in one, two and three dimensions.

The structures of three salts derived from clozapine, 8-chloro-11-(4-methyl-piperazin-1-yl)-5H-dibenzo[b,e][1,4]diazepine, are reported, namely, clo-za-pin-ium 3,5-di-nitro-benzoate dimethyl sulfoxide monosolvate, C18H20ClN4 (+)·C7H3N2O6 (-)·C2H6OS, (I), where the dimethyl sulfoxide component is disordered over two sets of atomic sites having occupancies 0.627 (2) and 0.373 (2); clo-za-pin-ium hydrogen maleate 0.21-hydrate, C18H20ClN4 (+)·C4H3O4 (-)·0.21H2O, (II), and clozapinium 2-hy-droxy-benzoate, C18H20ClN4 (+)·C7H5O3 (-), (III). In all three salts, the protonation site is the methyl-ated N atom of the piperazine ring, and the dimensions and conformations of the fused tricyclic system are very similar. However, differences are apparent in the piperazine component: in both compounds (II) and (III), the unprotonated N atom of this ring has a pyramidal geometry, but in compound (I) this atom has a planar geometry. In compound (III), both N-substituents in this ring occupy equatorial sites, but in compound (II) the fused tricyclic system occupies an axial site of the piperazine ring. The independent components of compound (I) are linked within the selected asymmetric unit by a combination of N-H⋯O and C-H⋯O hydrogen bonds, and these hydrogen-bonded aggregates are linked into chains by an aromatic π-π stacking inter-action. In compound (II), the components are linked into sheets by a combination of O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds, and in compound (III), a combination of N-H⋯O, C-H⋯O and C-H⋯N hydrogen bonds links the components into a three-dimensional framework structure. Comparisons are made with some similar compounds.

3-Cyano-6-hydroxy-4-methyl-2-pyridone: two new pseudopolymorphs and two cocrystals with products of an in situ nucleophilic aromatic substitution.

Four crystal structures of 3-cyano-6-hydroxy-4-methyl-2-pyridone (CMP), viz. the dimethyl sulfoxide monosolvate, C7H6N2O2·C2H6OS, (1), the N,N-dimethylacetamide monosolvate, C7H6N2O2·C4H9NO, (2), a cocrystal with 2-amino-4-dimethylamino-6-methylpyrimidine (as the salt 2-amino-4-dimethylamino-6-methylpyrimidin-1-ium 5-cyano-4-methyl-6-oxo-1,6-dihydropyridin-2-olate), C7H13N4(+)·C7H5N2O2(-), (3), and a cocrystal with N,N-dimethylacetamide and 4,6-diamino-2-dimethylamino-1,3,5-triazine [as the solvated salt 2,6-diamino-4-dimethylamino-1,3,5-triazin-1-ium 5-cyano-4-methyl-6-oxo-1,6-dihydropyridin-2-olate-N,N-dimethylacetamide (1/1)], C5H11N6(+)·C7H5N2O2(-)·C4H9NO, (4), are reported. Solvates (1) and (2) both contain the hydroxy group in a para position with respect to the cyano group of CMP, acting as a hydrogen-bond donor and leading to rather similar packing motifs. In cocrystals (3) and (4), hydrolysis of the solvent molecules occurs and an in situ nucleophilic aromatic substitution of a Cl atom with a dimethylamino group has taken place. Within all four structures, an R2(2)(8) N-H...O hydrogen-bonding pattern is observed, connecting the CMP molecules, but the pattern differs depending on which O atom participates in the motif, either the ortho or para O atom with respect to the cyano group. Solvents and coformers are attached to these arrangements via single-point O-H...O interactions in (1) and (2) or by additional R4(4)(16) hydrogen-bonding patterns in (3) and (4). Since the in situ nucleophilic aromatic substitution of the coformers occurs, the possible Watson-Crick C-G base-pair-like arrangement is inhibited, yet the cyano group of the CMP molecules participates in hydrogen bonds with their coformers, influencing the crystal packing to form chains.

Ethyl 6-amino-5-cyano-4-phenyl-2,4-di-hydro-pyrano[2,3-c]pyrazole-3-carboxyl-ate dimethyl sulfoxide monosolvate.

In the asymmetric unit of the title compound, C16H14N4O3·C2H6OS, there are two independent main mol­ecules (A and B) and two dimethyl sulfoxide solvent mol­ecules. In mol­ecule A, the pyran ring is in a flattened sofa conformation, with the sp 3-hydridized C atom forming the flap. In mol­ecule B, the pyran ring is in a flattened boat conformation, with the sp 3-hydridized C atom and the O atom deviating by 0.073 (3) and 0.055 (3) Å, respectively, from the plane of the other four atoms. The mean planes the pyrazole and phenyl rings form dihedral angles of 84.4 (2) and 84.9 (2)°, respectively, for mol­ecules A and B. In the crystal, N—H⋯O and N—H⋯N hydrogen bonds link the components of the structure into chains along [010]. In both solvent mol­ecules, the S atoms are disordered over two sites, with occupancy ratios of 0.679 (4):0.321 (4) and 0.546 (6):0.454 (6).

Alternariol 9-O-methyl ether dimethyl sulfoxide monosolvate

The title compound (systematic name: 3,7-dihy­droxy-9-meth­oxy-1-methyl-6H-benzo[c]chromen-6-one dimethyl sulfoxide monosolvate), C15H12O5·C2H6OS, was isolated from an unidentified endophytic fungus (belonging to class Ascomycetes) of Taxus sp. In the crystal, both the alternariol 9-O-methyl ether (AME) and the dimethyl sulfoxide (DMSO) mol­ecules exhibit crystallographic mirror symmetry. One of the hy­droxy groups makes bifurcated hydrogen bonds, viz. an intra­molecular bond with the carbonyl group and an inter­molecular bond with the carbonyl group in an inversion-related AME mol­ecule. In the crystal, the AME mol­ecules are organized into stacks parallel with the b axis by π–π inter­actions between centrosymmetrically related mol­ecules [the distance between the centroid of the central ring and the centroid of the meth­oxy-substituted benzene ring in the next mol­ecule of the stack is 3.6184 (5) Å]. Pairs of DMSO mol­ecules, linked via centrosymmetric C—H⋯O contacts, are inserted into the voids created by the AME mol­ecules, making O—H⋯O and C—H⋯O contacts with the hosts.

9-(5-Bromo-1H-indol-3-yl)-1,2,3,4,5,6,7,8,9,10-decahydroacridine-1,8-dione dimethyl sulfoxide monosolvate

In the title compound, C21H19BrN2O2·C2H6OS, the indole ring system is essentially planar, with a maximum deviation of 0.050 (3) Å for the non-bridgehead C atom adjacent to the N atom. The two cyclo­hex-2-enone rings adopt half-chair conformations. An intra­molecular C—H⋯O hydrogen bond occurs. The solvent mol­ecule exhibits minor disorder of the S atom [site occupancies = 0.8153 (16) and 0.1847 (18)]. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds, forming layers parallel to the bc plane.

2-Cyano-3-(2,3,6,7-tetra-hydro-1H,5H-benzo[ij]quinolizin-9-yl)prop-2-enoic acid dimethyl sulfoxide monosolvate.

In dimethyl sulfoxide solvated 9-(2-carb­oxy-2-cyano­vin­yl)julolidine, C16H16N2O2·C2H6OS, the essentially planar –CH=(CN)–CO2H substituent (r.m.s. deviation = 0.014 Å) is almost coplanar with respect to the benzene ring, the dihedral angle between the two planes being 0.48 (2)°. The conformations of the fused, non-aromatic rings were found to be half-chair. In the crystal, the acid molecule forms a hydrogen bond to the O atom of the solvent mol­ecule. The acid mol­ecule is disordered over two positions with respect to the methyl­ene C atoms in a 1:1 ratio. The crystal studied was found to be a racemic twin.

Pseudopolymorphs of chelidamic acid and its dimethyl ester

Different tautomeric and zwitterionic forms of chelidamic acid (4-hydroxypyridine-2,6-dicarboxylic acid) are present in the crystal structures of chelidamic acid methanol monosolvate, C(7)H(5)NO(5)·CH(4)O, (Ia), dimethylammonium chelidamate (dimethylammonium 6-carboxy-4-hydroxypyridine-2-carboxylate), C(2)H(8)N(+)·C(7)H(4)NO(5)(-), (Ib), and chelidamic acid dimethyl sulfoxide monosolvate, C(7)H(5)NO(5)·C(2)H(6)OS, (Ic). While the zwitterionic pyridinium carboxylate in (Ia) can be explained from the pK(a) values, a (partially) deprotonated hydroxy group in the presence of a neutral carboxy group, as observed in (Ib) and (Ic), is unexpected. In (Ib), there are two formula units in the asymmetric unit with the chelidamic acid entities connected by a symmetric O-H···O hydrogen bond. Also, crystals of chelidamic acid dimethyl ester (dimethyl 4-hydroxypyridine-2,6-dicarboxylate) were obtained as a monohydrate, C(9)H(9)NO(5)·H(2)O, (IIa), and as a solvent-free modification, in which both ester molecules adopt the hydroxypyridine form. In (IIa), the solvent water molecule stabilizes the synperiplanar conformation of both carbonyl O atoms with respect to the pyridine N atom by two O-H···O hydrogen bonds, whereas an antiperiplanar arrangement is observed in the water-free structure. A database study and ab initio energy calculations help to compare the stabilities of the various ester conformations.

1,2-Bis(diphenyl-phosphan-yl)ethane-κ(2)P,P']dichloridopalladium(II) dimethyl sulfoxide monosolvate.

In the title compound, [PdCl2(C26H24P2)]·C2H6OS, the PdII atom adopts a distorted cis-PdCl2P2 square-planar coordination geometry. The five-membered chelate ring adopts an envelope conformation with a methyl­ene C atom in the flap position. The S and C atoms of the dimethyl sulfoxide (DMSO) solvent mol­ecule are disordered over two sets of sites in a 0.8976 (18):0.1024 (18) ratio. The DMSO O atom accepts three C—H⋯O hydrogen bonds from an adjacent complex mol­ecule.

Conformational studies of hydantoin-5-acetic acid and orotic acid

Hydantoin-5-acetic acid [2-(2,5-dioxoimidazolidin-4-yl)acetic acid] and orotic acid (2,6-dioxo-1,2,3,6-tetrahydropyrimidine-4-carboxylic acid) each contain one rigid acceptor-donor-acceptor hydrogen-bonding site and a flexible side chain, which can adopt different conformations. Since both compounds may be used as coformers for supramolecular complexes, they have been crystallized in order to examine their conformational preferences, giving solvent-free hydantoin-5-acetic acid, C(5)H(6)N(2)O(4), (I), and three crystals containing orotic acid, namely, orotic acid dimethyl sulfoxide monosolvate, C(5)H(4)N(2)O(4)·C(2)H(6)OS, (IIa), dimethylammonium orotate-orotic acid (1/1), C(2)H(8)N(+)·C(5)H(3)N(2)O(4)(-)·C(5)H(4)N(2)O(4), (IIb), and dimethylammonium orotate-orotic acid (3/1), 3C(2)H(8)N(+)·3C(5)H(3)N(2)O(4)(-)·C(5)H(4)N(2)O(4), (IIc). The crystal structure of (I) shows a three-dimensional network, with the acid function located perpendicular to the ring. Interestingly, the hydroxy O atom acts as an acceptor, even though the carbonyl O atom is not involved in any hydrogen bonds. However, in (IIa), (IIb) and (IIc), the acid functions are only slightly twisted out of the ring planes. All H atoms of the acidic functions are directed away from the rings and, with respect to the carbonyl O atoms, they show an antiperiplanar conformation in (I) and synperiplanar conformations in (IIa), (IIb) and (IIc). Furthermore, in (IIa), (IIb) and (IIc), different conformations of the acid O=C-C-N torsion angle are observed, leading to different hydrogen-bonding arrangements depending on their conformation and composition.

2-Ammonio-5-chloro-4-methylbenzenesulfonate, its 1-methyl-2-pyrrolidone and dimethyl sulfoxide monosolvates and a corrected structure of 2,2′-(1,4-phenylene)di(4,5-dihydroimidazolium) bis(4-aminobenzenesulfonate) dihydrate

2-Ammonio-5-chloro-4-methylbenzenesulfonate, C(7)H(8)ClNO(3)S, (Ia), is an intermediate in the synthesis of lake red azo pigments. The present structure determination from single-crystal data confirms the results of a previous powder diffraction determination [Bekö, Thoms, Brüning, Alig, van de Streek, Lakatos, Glaubitz & Schmidt (2010). Z. Kristallogr. 225, 382-387]. The zwitterionic tautomeric form is confirmed. During a polymorph screening, two additional pseudopolymorphs were obtained, viz. 2-ammonio-5-chloro-4-methylbenzenesulfonate 1-methyl-2-pyrrolidone monosolvate, C(7)H(8)ClNO(3)S·C(5)H(9)NO, (Ib), and 2-ammonio-5-chloro-4-methylbenzenesulfonate dimethyl sulfoxide monosolvate, C(7)H(8)ClNO(3)S·C(2)H(6)OS, (Ic). The molecules of (Ib) have crystallographic m symmetry. The 1-methyl-2-pyrrolidone solvent molecule has an envelope conformation and is disordered around the mirror plane. The structure shows hydrogen-bonded ladders of molecules [graph-set notation C(2)(2)(6)R(2)(2)(12)] in the [010] direction. The benzene groups of adjacent ladders are also stacked in this direction. A different type of hydrogen-bonded ladder [graph-set notation C(6)R(2)(2)(4)R(4)(4)(12)] occurs in (Ic). In (Ia), (Ib) and (Ic), the molecules correspond to the zwitterionic tautomer. The structure of the cocrystal of 4-aminobenzenesulfonic acid with 1,4-bis(4,5-dihydroimidazol-2-yl)benzene [Shang, Ren, Wang, Lu & Yang (2009). Acta Cryst. E65, o2221-o2222] is corrected; it actually contains 4-aminobenzenesulfonate anions and 2,2'-(1,4-phenylene)di(dihydroimidazolium) dications, i.e. 2,2'-(1,4-phenylene)di(4,5-dihydroimidazolium) bis(4-aminobenzenesulfonate) dihydrate, C(12)H(16)N(4)(2+)·2C(6)H(6)NO(3)S(-)·2H(2)O. Hence, all known structures of aminobenzenesulfonic acid complexes contain ionic or zwitterionic molecules; there is no known structure with a neutral aminobenzenesulfonic acid molecule.