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1.  Conformation and crystal structures of 1-amino­cyclo­hexa­neacetic acid (β3,3Ac6c) in N-protected derivatives1  
The gauche conformation of backbone torsion angles (ϕ, θ) for β3,-Ac6c-OH is observed in the N-protected derivatives of 1-amino­cyclo­hexa­neacetic acid.
N-Protected derivatives of 1-amino­cyclo­hexa­neacetic acid (β3,3-Ac6c), namely Valeroyl-β3,3-Ac6c-OH [2-(1-pentanamidocyclohexyl)acetic acid, C13H23NO3], (I), Fmoc-β3,3-Ac6c-OH [2-(1-{[(9H-fluoren-9-yloxy)carbonyl]amino}cyclohexyl)acetic acid, C23H25NO4], (II), and Pyr-β3,3-Ac6c-OH {2-[1-(pyrazine-2-amido)cyclohexyl]acetic acid, C13H17N3O3}, (III), were synthesized and their conformational properties were determined by X-ray diffraction analysis. The backbone torsion angles (ϕ, θ) for β3,3-Ac6c-OH are restricted to gauche conformations in all the derivatives, with a chair conformation of the cyclo­hexane ring. In the crystal structure of (I), the packing of mol­ecules shows both carb­oxy­lic acid R 2 2(8) O—H⋯O and centrosymmetric R 2 2(14) N—H⋯O hydrogen-bonding inter­actions, giving rise to chains along the c-axis direction. In (II), centrosymmetric carb­oxy­lic acid R 2 2(8) O—H⋯O dimers are extended through N—H⋯O hydrogen bonds and together with inter-ring π–π inter­actions between Fmoc groups [ring centroid distance = 3.786 (2) Å], generate a layered structure lying parallel to (010). In the case of compound (III), carb­oxy­lic acid O—H⋯Npyrazine hydrogen bonds give rise to zigzag ribbon structures extending along the c-axis direction.
doi:10.1107/S1600536814020777
PMCID: PMC4257263  PMID: 25484721
crystal structure; disubstituted-β-amino acids; π–π inter­action; hydrogen bonds; conformation
2.  2-Amino­pyridinium 1-phenyl­cyclo­propane-1-carboxyl­ate 
In the title salt, C5H7N2 +·C10H9O2 −, 2-amino­pyridine and 1-phenyl­cyclo­propane-1-carb­oxy­lic acid crystallize together, forming a 2-amino­pyridinium–carboxyl­ate supra­molecular heterosynthon involving two N—H⋯O hydrogen bonds, which in turn dimerizes to form a four-component supra­molecular unit also sustained by N—H⋯O hydrogen bonding. A C—H⋯π inter­action between a pyridine C—H group and the centroid of the phenyl ring of the anion further stabilizes the four-component supra­molecular unit. The overall crystal packing also features C—H⋯O inter­actions.
doi:10.1107/S1600536810049093
PMCID: PMC3011640  PMID: 21589613
3.  Acrinathrin: (S)-cyano­(3-phen­oxy­phenyl)methyl (Z)-(1R,3S)-2,2-dimethyl-3-{2-[2,2,2-trifluoro-1-(trifluoro­methyl)eth­oxy­carbon­yl]vin­yl}cyclo­propane-1-carboxyl­ate 
In the title compound, C26H21F6NO5, the dihedral angle between the cyclo­propane ring plane and the vinyl group plane is 79.3 (3)°. The dihedral angle between the benzene and phenyl ring planes in the phen­oxy­benzyl group is 82.7 (1)°. In the crystal structure, weak inter­molecular C—H⋯π inter­actions and C—H⋯F hydrogen bonds contribute to the stabilization of the packing.
doi:10.1107/S1600536811014760
PMCID: PMC3089073  PMID: 21754558
4.  Crystal structure of [propane-1,3-diylbis(piperidine-4,1-di­yl)]bis­[(pyridin-4-yl)methanone]–4,4′-oxydi­benzoic acid (1/1) 
In the title co-crystal, C25H32N4O2·C14H10O5, mol­ecules are connected into supra­molecular chains aligned along [102] by O—H⋯N hydrogen bonding. These aggregate into supra­molecular layers oriented parallel to (20-1) by C—H⋯O inter­actions. These layers then stack in an ABAB pattern along the c crystal direction to give the full three-dimensional crystal structure. The central chain in the dipyridylamide has an anti–anti conformation. The dihedral angle between the aromatic ring planes is 29.96 (3)°. Disorder is noted in some of the residues in the structure and this is manifested in two coplanar dispositions of one statistically disordered carb­oxy­lic acid group.
doi:10.1107/S160053681401811X
PMCID: PMC4186108  PMID: 25309203
crystal structure; co-crystal; hydrogen bonding; piperazine-1,4-diylbis(pyridin-4-yl­methanone); 4,4′-oxydi­benzoic acid
5.  Crystal structures and hydrogen bonding in the co-crystalline adducts of 3,5-di­nitro­benzoic acid with 4-amino­salicylic acid and 2-hy­droxy-3-(1H-indol-3-yl)propenoic acid 
The crystal structures of the co-crystal adducts of 3,5-di­nitro­benzoic acid with 4-amino­salicylic acid (a 2:2:0.4-hydrate) and with 2-hy­droxy-3-(1H-indol-3-yl)propenoic acid (a 1:1:1 d 6-DMSO solvate) show, respectively, polymeric and hexa­molecular hydrogen-bonded and π–π-bonded structures
The structures of the co-crystalline adducts of 3,5-di­nitro­benzoic acid (3,5-DNBA) with 4-amino­salicylic acid (PASA), the 1:1 partial hydrate, C7H4N2O6·C7H7NO3·0.2H2O, (I), and with 2-hy­droxy-3-(1H-indol-3-yl)propenoic acid (HIPA), the 1:1:1 d 6-dimethyl sulfoxide solvate, C7H4N2O6·C11H9NO3·C2D6OS, (II), are reported. The crystal substructure of (I) comprises two centrosymmetric hydrogen-bonded R 2 2(8) homodimers, one with 3,5-DNBA, the other with PASA, and an R 2 2(8) 3,5-DNBA–PASA heterodimer. In the crystal, inter-unit amine N—H⋯O and water O—H⋯O hydrogen bonds generate a three-dimensional supra­molecular structure. In (II), the asymmetric unit consists of the three constituent mol­ecules, which form an essentially planar cyclic hydrogen-bonded heterotrimer unit [graph set R 3 2(17)] through carboxyl, hy­droxy and amino groups. These units associate across a crystallographic inversion centre through the HIPA carb­oxy­lic acid group in an R 2 2(8) hydrogen-bonding association, giving a zero-dimensional structure lying parallel to (100). In both structures, π–π inter­actions are present [minimum ring-centroid separations = 3.6471 (18) Å in (I) and 3.5819 (10) Å in (II)].
doi:10.1107/S1600536814019898
PMCID: PMC4257166  PMID: 25484647
co-crystal structures; carb­oxy­lic acid mol­ecular adducts; 3,5-di­nitro­benzoic acid; 4-amino­salicylic acid; 2-hy­droxy-3-(1H-indol-3-yl)propenoic acid; hydrogen bonding; homodimers; heterodimers; π–π inter­actions.
6.  rac-cis-Cyclo­hexane-1,2-dicarb­oxy­lic acid–isoquinoline (1/1) 
In the crystal structure of the title mol­ecular adduct, C9H7N·C8H12O4, the two species are ­linked through a carb­oxy­lic acid–isoquinoline O—H⋯N hydrogen bond. These mol­ecular pairs then inter-associate through the second acid group of the cis-cyclo­hexane-1,2-dicarb­oxy­lic acid molecules, forming a classic centrosymmetric cyclic head-to-head carb­oxy­lic acid–carboxyl O—H⋯O hydrogen-bonding association [graph-set R 2 2(8)], giving a zero-dimensional (cluster) structure, consisting of two of each species.
doi:10.1107/S1600536811030613
PMCID: PMC3200759  PMID: 22058919
7.  rac-4-Carbamoylpiperidinium cis-2-car­boxy­cyclo­hexane-1-carboxyl­ate 
In the title racemic salt, C6H13N2O+·C8H11O4 −, formed from the reaction of cis-cyclo­hexane-1,2-dicarb­oxy­lic anhydride with isonipecotamide, the cations are linked into duplex chain substructures through both centrosymmetric cyclic head-to-head ‘amide motif’ hydrogen-bonding associations [graph set R 2 2(8)] and ‘side-by-side’ R 2 2(14) associations. The anions are incorporated into the chains through cyclic R 4 3(10) inter­actions involving amide and piperidinium N—H⋯Ocarbox­yl hydrogen bonds which, together with inter-anion carb­oxy­lic acid O—H⋯Ocarbox­yl hydrogen bonds, give a two-dimensional layered structure extending along (011).
doi:10.1107/S1600536812004710
PMCID: PMC3295451  PMID: 22412562
8.  rac-2-Amino­pyridinium cis-2-carb­oxy­cyclo­hexane-1-carboxyl­ate 
In the structure of the title compound, C5H7N2 +·C8H11O4 −, the cis anions associate through head-to-tail carb­oxy­lic acid–carboxyl O—H⋯O hydrogen bonds [graph set C(7)], forming chains which extend along c and are inter­linked through the carboxyl groups, forming cyclic R 2 2(8) associations with the pyridinium and an amine H-atom donor of the cation. Further amine–carboxyl N—H⋯O inter­actions form enlarged centrosymmetric rings [graph set R 4 4(18)] and extensions down b, giving a three-dimensional structure.
doi:10.1107/S1600536811025256
PMCID: PMC3212294  PMID: 22090951
9.  3-[(E)-2-Chloro-3,3,3-trifluoro­prop-1-en-1-yl]-N-(2-chloro­phen­yl)-2,2-dimethyl­cyclo­propane-1-carboxamide 
In the title compound, C15H14Cl2F3NO, synthesized by the reaction of 3-[(E)-2-chloro-3,3,3-trifluoro­prop-1-en­yl]-2,2-dimethyl­cyclo­propane­carb­oxy­lic acid and 2-chloro­aniline, the aromatic ring makes a dihedral angle of 76.7 (3)° with the plane of the cyclo­propane ring. In the crystal, inter­molecular N—H⋯O hydrogen bonds link the mol­ecules into chains running along the b axis.
doi:10.1107/S1600536810050634
PMCID: PMC3050387  PMID: 21522772
10.  Propane-1,3-diaminium pyridine-2,5-di­carboxyl­ate dimethyl sulfoxide mono­solvate 
In the crystal structure of the title solvated molecular salt, C3H12N2 2+·C7H3NO4 2−·C2H6OS, two amine groups of propane-1,3-diamine (pda) are protonated and two carb­oxy­lic acid groups of pyridine-2,5-dicarb­oxy­lic acid (2,5-pydcH2) are deprotonated. The crystal packing features N—H⋯O hydrogen bonds and weak C—H⋯O inter­molecular inter­actions.
doi:10.1107/S1600536811004545
PMCID: PMC3051960  PMID: 21522367
11.  A second tricilinc polymorph of 6,6′-dieth­oxy-2,2′-[propane-1,2-diylbis(nitrilo­methyl­idyne)]diphenol 
The title Schiff base compound, C21H26N2O4, is a second triclinic polymorph of a previously reported room-temperature structure [Jia (2009 ▶). Acta Cryst. E65, o646]. Strong intra­molecular O—H⋯N hydrogen bonds generate S(6) ring motifs. Inter­molecular C—H⋯O inter­actions link neighbouring mol­ecules into dimers with an R 2 2(16) ring motif. The mean planes of the two benzene rings are almost perpendicular to each other, making a dihedral angle of 88.24 (5)°. An inter­esting feature of the crystal structure is the intermolecular short C⋯O [3.1878 (13) Å] contact which is shorter than the sum of the van der Waals radii of the relevant atoms. The crystal structure is further stabilized by inter­molecular C—H⋯π and π–π inter­actions [centroid–centroid distance = 3.7414 (6) Å]. The structure has a stereogenic centre but the space group is centrosymmetric, so the mol­ecule exists as a racemate.
doi:10.1107/S1600536809008137
PMCID: PMC2968989  PMID: 21582458
12.  Crystal structure of 8-[7,8-bis­(4-chloro­benzo­yl)-7H-cyclo­penta­[a]ace­naphthylen-9-yl]naphthalene-1-carb­oxy­lic acid 
The title compound packs with a three-dimensional supra­molecular architecture via O—H⋯O, C—H⋯O and C—H⋯Cl hydrogen bonds and through C—H⋯π inter­actions.
The title compound, C40H22Cl2O4, was formed by a Michael–Aldol domino reaction sequence, which coupled acenaphthene­quinone with 4-chloro­aceto­phenone in the presence of KOH in methanol. The dihedral angles between the central cyclo­penta­[a]ace­naphthyl­ene fused-ring system (r.m.s. deviation = 0.066 Å) and the 4-chloro­benzoyl rings are 62.25 (10) and 70.19 (10)°. The dihedral angle between the central ring system and the naphthoic acid grouping is 62.46 (7)°. This twisting of the pendant rings facilitates the formation of an intra­molecular aromatic π–π stacking inter­action between the 4-chloro­benzoyl and naphthoic acid rings, with centroid–centroid distances of 3.4533 (16) and 3.5311 (16) Å, and a C—H⋯π inter­action between one of the H atoms of the central moiety and the 4-chloro­benzoyl ring with an H⋯π distance of 2.57 Å. In the crystal, carb­oxy­lic acid inversion dimers generate R 2 2(8) loops. The dimers are linked by weak C—H⋯O and C—H⋯Cl hydrogen bonds and C—H⋯π inter­actions, generating a three-dimensional architecture.
doi:10.1107/S2056989014026334
PMCID: PMC4331862
crystal structure; domino reaction; acenaphthene­quinone; 4-chloro­aceto­phenone; hydrogen bonding
13.  4-Meth­oxy­anilinium 2-carb­oxy-4,5-di­chloro­benzoate 
In the title salt C7H10NO+·C8H3Cl2O4 − the benzene rings of the cation and anion are essentially parallel [inter-ring dihedral angle 4.8 (2)°]. In the anion the carb­oxy­lic acid and carboxyl­ate groups make dihedral angles of 19.0 (2) and 79.5 (2)°, respectively, with the benzene ring. Aminium N—H⋯O, carb­oxy­lic acid O—H⋯O and weak aromatic C—H⋯O hydrogen-bonding associations with carboxyl O-atom acceptors together with cation–anion π–π ring inter­actions [minimum ring centroid separation = 3.734 (3) Å] give rise to a sheet structure lying parallel to (001).
doi:10.1107/S1600536813025014
PMCID: PMC3790412  PMID: 24098231
14.  2-Amino-4-(4-chloro­phen­yl)-7,7-dimethyl-5-oxo-5,6,7,8-tetra­hydro-4H-chromene-3-carbonitrile propan-2-one monosolvate 
In the title compound, C18H17ClN2O2·C3H6O, the 4H-pyran ring is nearly planar [maximum deviation = −0.108 (1) Å] and the cyclo­hexene ring is puckered [puckering parameters Q T = 0.4596 (17) Å, θ = 55.9 (2)° and ϕ = 226.5 (3)°]. The 4H-pyran ring is approximately perpendicular to the benzene ring [dihedral angle = 84.35 (7)°] and is almost coplanar with the mean plane of the cyclo­hexene ring [dihedral angle = 8.64 (7)°]. In the crystal, inversion-related main mol­ecules are linked into dimers by pairs of N—H⋯N hydrogen bonds, generating an R 2 2(12) graph-set motif. These dimers are further connected by N—H⋯O and C—H⋯N hydrogen bonds, forming a layer structure extending parallel to the (011) plane. In addition, the mol­ecules within the layers inter­act with each other via C—H⋯π inter­actions.
doi:10.1107/S1600536812024142
PMCID: PMC3379514  PMID: 22719712
15.  2-[5-Methyl-2-(propan-2-yl)phen­oxy]-N′-{2-[5-methyl-2-(propan-2-yl)phen­oxy]acet­yl}acetohydrazide 
The complete mol­ecule of the title compound, C24H32N2O4, is generated by a crystallographic inversion center. The 1,2-diethyl­hydrazine moiety is nearly planar, with a maximum deviation of 0.024 (1) Å, and is inclined at a dihedral angle of 54.20 (4)° with the phenyl ring. In the crystal, [001] chains are formed, with adjacent mol­ecules in the chain linked by pair of inter­molecular N—H⋯O hydrogen bonds, generating R 2 2(10) ring motifs. Inter­molecular C—H⋯O hydrogen bonds and C—H⋯π inter­actions are also observed.
doi:10.1107/S1600536811033964
PMCID: PMC3200946  PMID: 22059000
16.  2-Carb­oxy-6-(quinolin-1-ium-8-yl­oxy)benzoate 
In the zwitterionic title compound, C17H11NO5, the dihedral angle between the two aromatic rings is 76.90 (7)°. The dihedral angles between the carboxyl groups and the benzene ring are 64.02 (9) and 21.67 (9)°, the larger angle being associated with an intra­molecular N—H⋯Ocarbox­yl hydrogen bond, resulting from proton transfer from the carb­oxy­lic acid group to the quinoline N atom and giving an S(9) ring motif. In the crystal, mol­ecules are connected by O—H⋯O hydrogen bonds into chains extending along the b-axis direction. An overall two-dimensional network structure is formed through π–π inter­actions between the quinoline rings [minimum ring-centroid separation = 3.6068 (6) Å].
doi:10.1107/S1600536812013980
PMCID: PMC3344484  PMID: 22590246
17.  Crystal structures of the co-crystalline adduct 5-(4-bromo­phen­yl)-1,3,4-thia­diazol-2-amine–4-nitro­benzoic acid (1/1) and the salt 2-amino-5-(4-bromo­phen­yl)-1,3,4-thia­diazol-3-ium 2-carb­oxy-4,6-di­nitro­phenolate 
The hydrogen-bonded structures of both a (1:1) mol­ecular adduct and a salt of 5-(4-bromo­phen­yl)-1,3,4-thia­diazol-2-amine with 4-nitro­benzoic acid and 3,5-di­nitro­salicylic acid, respectively, have been determined.
The structures of the 1:1 co-crystalline adduct C8H6BrN3S·C7H5NO4, (I), and the salt C8H7BrN3S+·C7H3N2O7 −, (II), obtained from the inter­action of 5-(4-bromo­phen­yl)-1,3,4-thia­diazol-2-amine with 4-nitro­benzoic acid and 3,5-di­nitro­salicylic acid, respectively, have been determined. The primary inter-species association in both (I) and (II) is through duplex R 2 2(8) (N—H⋯O/O—H⋯O) or (N—H⋯O/N—H⋯O) hydrogen bonds, respectively, giving heterodimers. In (II), these are close to planar [the dihedral angles between the thia­diazole ring and the two phenyl rings are 2.1 (3) (intra) and 9.8 (2)° (inter)], while in (I) these angles are 22.11 (15) and 26.08 (18)°, respectively. In the crystal of (I), the heterodimers are extended into a chain along b through an amine N—H⋯Nthia­diazole hydrogen bond but in (II), a centrosymmetric cyclic hetero­tetra­mer structure is generated through N—H⋯O hydrogen bonds to phenol and nitro O-atom acceptors and features, together with the primary R 2 2(8) inter­action, conjoined R 4 6(12), R 2 1(6) and S(6) ring motifs. Also present in (I) are π–π inter­actions between thia­diazole rings [minimum ring-centroid separation = 3.4624 (16) Å], as well as short Br⋯Onitro inter­actions in both (I) and (II) [3.296 (3) and 3.104 (3) Å, respectively].
doi:10.1107/S1600536814021138
PMCID: PMC4257302  PMID: 25484726
5-substituted-2-amino-1,3,4-thia­diazo­les; 4-nitro­benzoic acid; 3,5-di­nitro­salicylic acid; proton transfer; mol­ecular adducts; co-crystals; hydrogen bonding; π–π inter­actions; crystal structure
18.  Crystal structures and hydrogen bonding in the proton-transfer salts of nicotine with 3,5-di­nitro­salicylic acid and 5-sulfosalicylic acid 
The crystal structures of the 1:1 salts of nicotine with 3,5-di­nitro­salicylic acid and with 5-sulfosalicylic acid both show polymeric hydrogen-bonded and π–π-bonded structures but these differ in that in the first example, cations and anions form separate cation chains or anion columns which are unassociated through formal hydrogen bonds while in the second, hydrogen-bonded cation–anion chains are found.
The structures of the 1:1 anhydrous salts of nicotine (NIC) with 3,5-di­nitro­salicylic acid (DNSA) and 5-sulfosalicylic acid (5-SSA), namely (1R,2S)-1-methyl-2-(pyridin-3-yl)-1H-pyrrolidin-1-ium 2-carb­oxy-4,6-di­nitro­phenolate, C10H15N2 +·C7H3N2O7 −, (I), and (1R,2S)-1-methyl-2-(pyridin-3-yl)-1H-pyrrolidin-1-ium 3-carb­oxy-4-hy­droxy­benzene­sulfonate, C10H15N2 +·C7H5O6S−, (II), are reported. The asymmetric units of both (I) and (II) comprise two independent nicotinium cations (C and D) and either two DNSA or two 5-SSA anions (A and B), respectively. One of the DNSA anions shows a 25% rotational disorder in the benzene ring system. In the crystal of (I), inter-unit pyrrolidinium N—H⋯Npyridine hydrogen bonds generate zigzag NIC cation chains which extend along a, while the DNSA anions are not involved in any formal inter-species hydrogen bonding but instead form π–π-associated stacks which are parallel to the NIC cation chains along a [ring-centroid separation = 3.857 (2) Å]. Weak C—H⋯O inter­actions between chain substructures give an overall three-dimensional structure. In the crystal of (II), A and B anions form independent zigzag chains with C and D cations, respectively, through carb­oxy­lic acid O—H⋯Npyridine hydrogen bonds. These chains, which extend along b, are pseudocentrosymmetrically related and give π–π inter­actions between the benzene rings of anions A and B and the pyridine rings of the NIC cations C and D, respectively [ring centroid separations = 3.6422 (19) and 3.7117 (19) Å]. Also present are weak C—H⋯O hydrogen-bonding inter­actions between the chains, giving an overall three-dimensional structure.
doi:10.1107/S1600536814023253
PMCID: PMC4257264  PMID: 25484766
crystal structure; nicotine; proton-transfer salts; 3,5-di­nitro­salicylic acid; 5-sulfosalicylic acid; hydrogen-bonding; π–π inter­actions
19.  Diaqua­[N,N′-bis­(2-pyridylmethyl­ene)propane-1,3-diamine]manganese(II) dibromide–aqua­bromido[N,N′-bis­(2-pyridylmethyl­ene)propane-1,3-diamine]manganese(II) bromide–dibromido[N,N′-bis­(2-pyridylmethyl­ene)propane-1,3-diamine]manganese(II) (1/2/1) 
There are three different MnII complexes in the asymmetric unit of the title compound, [Mn(C15H16N4)(H2O)2]Br2·2{[MnBr(C15H16N4)(H2O)]Br}·[MnBr2(C15H16N4)]. In the neutral complex, the Mn2+ ion is six-coordinated in a distorted octa­hedral environment by four N atoms of the tetra­dentate ligand N,N′-bis­(2-pyridylmethyl­ene)propane-1,3-diamine (bppd) and two bromide ligands. In the two cationic complexes, the Mn2+ ions are also six-coordinated in similar environments, but one Mn ion is coordinated by four N atoms of bppd, one Br atom and one O atom of a coordinating water mol­ecule, whereas the other Mn ion is coordinated by four N atoms of bppd and two O atoms of water ligands. The complexes with two coordinated Br atoms or two H2O ligands are disposed about a twofold axis through Mn and C atoms with the special positions (, y, 0) and (0, y, ), respectively. The compound displays inter­molecular O—H⋯Br hydrogen bonding. There are inter­molecular π–π inter­actions between adjacent pyridine rings, with centroid–centroid distances of 3.822 and 3.833 Å, and a C—H⋯O inter­action is also present.
doi:10.1107/S1600536808041731
PMCID: PMC2967905  PMID: 21581533
20.  {6,6′-Dimeth­oxy-2,2′-[2,2-dimethyl­propane-1,3-diylbis(nitrilo­methyl­idyne)]diphenolato}nickel(II) 1.78-hydrate 
In the title complex, [Ni(C21H24N2O4)]·1.78H2O, the NiII ion has a slightly distorted planar geometry, coordinated by the two N and two O atoms of the tetra­dentate Schiff base ligand, with a mean deviation of 0.272 Å from the NiN2O2 plane. The N and O donor atoms are mutually cis. The dihedral angle between two benzene rings of the ligand is 38.86 (8)°. There are also three solvent water mol­ecules, two of which lie across different crystallographic twofold rotation axes; one of these is partially occupied with a refined occupancy factor of 0.570 (7). The water mol­ecules are linked together as tetra­mers in R 2 2(8) ring motifs, which also connect two neighbouring mol­ecules of the complex through a network of O—H⋯O hydrogen bonds. The crystal structure is further stabilized by inter­molecular C—H⋯O and C—H⋯π inter­actions, which link neighbouring mol­ecules into extended chains along the b axis. Other inter­esting features of the crystal structure are the short inter­molecular C⋯C [3.204 (3)–3.365 (3) Å] and the C⋯O [3.199 (2)–3.205 (2) Å] contacts which are shorter than the sum of the van der Waals radii of these atoms.
doi:10.1107/S1600536809014500
PMCID: PMC2977614  PMID: 21583800
21.  2-(4-Methyl­cyclo­hex-3-en­yl)propan-2-yl N-phenyl­carbamate 
In the title carbamate compound, C17H23NO2, one of the Csp 3 atoms of the cyclo­hexene ring is disordered over two sites with refined occupancies of 0.55 (2) and 0.45 (2), both disorder components resulting in half-boat conformations. The mean plane through the carbamate unit is inclined at inter­planar angles of 14.80 (13), 18.30 (17) and 24.0 (2)°, respectively, with respect to the phenyl ring, and the major and minor disorder component cyclo­hexene rings. In the crystal structure, adjacent mol­ecules are linked into chains along [001] via inter­molecular N—H⋯O hydrogen bonds. The crystal structure is further stabilized by weak inter­molecular C—H⋯π inter­actions.
doi:10.1107/S1600536810025080
PMCID: PMC3007260  PMID: 21588225
22.  2,3,4-Trihy­droxy­benzoic acid 0.25-hydrate 
The asymmetric unit of the title compound, C7H6O5·0.25H2O, contains two mol­ecules of 2,3,4-trihy­droxy­benzoic acid, with similar conformations, and one water mol­ecule which lies on a twofold rotation axis. Both acid mol­ecules are essentially planar [maximum r.m.s deviations = 0.0324 (2) and 0.0542 (3) Å for the two acid molecules]. The mol­ecular conformations are stabilized by intra­molecular O(phenol)—H⋯O(carbox­yl/phenol) inter­actions. A cyclic inter­molecular association is formed between the two acid and one water mol­ecule [graph set R 3 3(12)] involving O—H⋯O hydrogen bonds. The two acid mol­ecules are further linked through a cyclic R 2 2(8) carb­oxy­lic acid hydrogen-bonding association, which together with inter­molecular O—H⋯O hydrogen-bonding inter­actions involving the phenol groups and the water mol­ecule, and weak π–π inter­actions [minimum ring centroid separation = 3.731 (3) Å], give a three-dimensional network.
doi:10.1107/S160053681200709X
PMCID: PMC3297886  PMID: 22412689
23.  catena-Poly[[silver(I)-μ-4,4′-bipyridine-κ2 N:N′] 4-[2-(4-carb­oxy­phen­yl)-1,1,1,3,3,3-hexa­fluoro­propan-2-yl]benzoate] 
Assembly of the flexible dicarb­oxy­lic ligand 4-[2-(4-carboxyphenyl)-1,1,1,3,3,3-hexafluoropropan-2-yl]benzoate and 4,4′-bipyridine as co-ligand with AgI ions resulted in the formation of the polymeric title compound, {[Ag(C10H8N2)](C17H9F6O4)}n, in which the metal atoms are bridged by the 4,4′-bipyridine ligands, generating cationic chains extending along [010]. The dihedral angles between the benzene rings in the anion and the pyridine rings in the cation are 72.42 (9) and 9.36 (10)°, respectively. The mol­ecular conformation of the anion is stabilized by intra­molecular C—H⋯F hydrogen bonds. In the crystal, the anions inter­act with the cationic chains via C—H⋯O hydrogen bonds, forming layers parallel to (001), in which weak π–π stacking inter­actions [centroid–centroid distances = 3.975 (3)–4.047 (3) Å] involving the pyridine rings of adjacent 4,4′-bipyridine ligands are present. The planes are further assembled into a three-dimensional network by O—H⋯O hydrogen bonds.
doi:10.1107/S1600536812015322
PMCID: PMC3344349  PMID: 22590115
24.  Methyl 2-[2-(benzyl­oxycarbonyl­amino)­propan-2-yl]-5-hy­droxy-6-meth­oxy­pyrimidine-4-carboxyl­ate 
In the title compound, C18H21N3O6, a pyrimidine derivative, the dihedral angle between the benzene and pyrimidine rings is 52.26 (12)°. The carboxyl­ate unit is twisted with respect to the pyrimidine ring, making a dihedral angle of 12.33 (7)°. In the crystal, mol­ecules are linked by a pair of O—H⋯O hydrogen bonds, forming an inversion dimer. The dimers are stacked into columns along the b axis through weak C—H⋯O inter­actions.
doi:10.1107/S160053681005467X
PMCID: PMC3051748  PMID: 21522966
25.  4-(4-Nitro­benz­yl)pyridinium 3-carb­oxy-4-hy­droxy­benzene­sulfonate 
In the title salt, C12H11N2O2 +·C7H5O6S−, the dihedral angle between the benzene and pyridine rings in the 4-(4-nitro­benz­yl)pyridinium cation is 82.7 (2)°. Within the anion there is an intramolecular hydroxy-O—H⋯O(carboxylic acid) bond. In the crystal, the cation forms a single N+—H⋯Osulfonate hydrogen bond with the anion. These cation–anion pairs inter­act through duplex anion carb­oxy­lic acid O—H⋯Osulfonate hydrogen bonds, giving a centrosymmetric cyclic association [graph set R 2 2(16)]. The crystals studied were non-merohedrally twinned.
doi:10.1107/S1600536813000093
PMCID: PMC3569266  PMID: 23424489

Results 1-25 (680834)