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1.  Synthesis, Characterization and Biological Evaluation of Transition Metal Complexes Derived from N, S Bidentate Ligands 
Two bidentate NS ligands were synthesized by the condensation reaction of S-2-methylbenzyldithiocarbazate (S2MBDTC) with 2-methoxybenzaldehyde (2MB) and 3-methoxybenzaldehyde (3MB). The ligands were reacted separately with acetates of Cu(II), Ni(II) and Zn(II) yielding 1:2 (metal:ligand) complexes. The metal complexes formed were expected to have a general formula of [M(NS)2] where M = Cu2+, Ni2+, and Zn2+. These compounds were characterized by elemental analysis, molar conductivity, magnetic susceptibility and various spectroscopic techniques. The magnetic susceptibility measurements and spectral results supported the predicted coordination geometry in which the Schiff bases behaved as bidentate NS donor ligands coordinating via the azomethine nitrogen and thiolate sulfur. The molecular structures of the isomeric S2M2MBH (1) and S2M3MBH (2) were established by X-ray crystallography to have very similar l-shaped structures. The Schiff bases and their metal complexes were evaluated for their biological activities against estrogen receptor-positive (MCF-7) and estrogen receptor-negative (MDA-MB-231) breast cancer cell lines. Only the Cu(II) complexes showed marked cytotoxicity against the cancer cell lines. Both Schiff bases and other metal complexes were found to be inactive. In concordance with the cytotoxicity studies, the DNA binding studies indicated that Cu(II) complexes have a strong DNA binding affinity.
doi:10.3390/ijms160511034
PMCID: PMC4463689  PMID: 25988384
bidentate NS ligands; crystal structure analysis; hydrogen bonding; cytotoxic activity; DNA binding
2.  Crystal structure of 3-methyl­pyridine-2-carbaldehyde 4-methyl­thio­semi­carba­zone monohydrate 
In the title hydrate, C9H12N4S·H2O (systematic name: 3-methyl-1-{(E)-[(3-methyl­pyridin-2-yl)methyl­idene]amino}­thio­urea monohydrate), a small twist is noted between the pyridine ring and the rest of the organic mol­ecule [dihedral angle = 6.96 (5)°]. The imine and pyridine N atoms are syn, and the amine H atoms are anti. The latter arrangement allows for the formation of an intra­molecular N—H⋯N(imine) hydrogen bond. Both the N-bonded H atoms form hydrogen bonds to symmetry-related water mol­ecules, and the latter forms O—H hydrogen bonds with the pyridine N and thione S atoms. These inter­actions lead to supra­molecular layers that stack along the a-axis direction with no specific inter­actions between them.
doi:10.1107/S2056989015005034
PMCID: PMC4438841  PMID: 26029441
crystal structure; hydrogen bonding; thio­semicarbazone
3.  Crystal structure of 2′-hy­droxy­aceto­phenone 4-methyl­thio­semicarbazide 
In the organic mol­ecule of the title hydrate, C11H15N3OS·H2O, {systematic name: 3-ethyl-1-{(E)-[1-(2-hy­droxy­phen­yl)ethyl­idene]amino}­thio­urea monohydrate}, a dihedral angle of 5.39 (2)° is formed between the hy­droxy­benzene ring and the non-H atoms comprising the side chain (r.m.s. deviation = 0.0625 Å), with the major deviation from planarity noted for the terminal ethyl group [the C—N—C—C torsion angle = −172.17 (13)°]. The N—H H atoms are syn and an intra­molecular hy­droxy–imine O—H⋯N hydrogen bond is noted. In the crystal, the N-bonded H atoms form hydrogen bonds to symmetry-related water mol­ecules, and the latter form donor inter­actions with the hy­droxy O atom and with a hy­droxy­benzene ring, forming a O—H⋯π inter­action. The hydrogen bonding leads to supra­molecular tubes aligned along the b axis. The tubes are connected into layers via C—H⋯O inter­actions, and these stack along the c axis with no directional inter­actions between them.
doi:10.1107/S2056989015004958
PMCID: PMC4438807  PMID: 26029436
crystal structure; thio­semicarbazide; hydrogen bonding; O—H⋯π inter­actions
4.  Crystal structure of 2-((1E)-{2-[bis­(2-methyl­benzyl­sulfan­yl)methyl­idene]hydrazin-1-yl­idene}meth­yl)-6-meth­oxy­phenol 
In the title compound, C25H26N2O2S2, the central CN2S2 atoms are almost coplanar (r.m.s. deviation = 0.0058 Å). One phenyl ring clearly lies to one side of the central plane, while the other is oriented in the plane but splayed. Despite the different relative orientations, the phenyl rings form similar dihedral angles of 64.90 (3) and 70.06 (3)° with the central plane, and 63.28 (4)° with each other. The benzene ring is twisted with respect to the central plane, forming a dihedral angle of 13.17 (7)°. The S2C=N, N—N and N—N=C bond lengths of 1.2919 (19), 1.4037 (17) and 1.2892 (19) Å, respectively, suggest limited conjugation over these atoms; the configuration about the N—N=C bond is E. An intra­molecular O—H⋯N hydrogen bond is noted. In the crystal, phen­yl–meth­oxy C—H⋯O and phen­yl–phenyl C—H⋯π inter­actions lead to supra­molecular double chains parallel to the b axis. These are connected into a layer via meth­yl–phenyl C—H⋯π inter­actions, and layers stack along the a axis, being connected by weak π–π inter­actions between phenyl rings [inter-centroid distance = 3.9915 (9) Å] so that a three-dimensional architecture ensues.
doi:10.1107/S2056989015004946
PMCID: PMC4438809  PMID: 26029435
crystal structure; S-substituted di­thio­carbaza­tes; hydrogen bonding; C—H⋯π inter­actions; π–π inter­actions
5.  Crystal structure of benzyl 3-(3-methyl­phen­yl)di­thio­carbazate 
In the title compound, C15H16N2S2, the central CN2S2 residue is almost planar (r.m.s. deviation = 0.0354 Å) and forms dihedral angles of 56.02 (4) and 75.52 (4)° with the phenyl and tolyl rings, respectively; the dihedral angle between the aromatic rings is 81.72 (5)°. The conformation about the N—N bond is gauche [C—N—N—C = −117.48 (15)°]. Overall, the mol­ecule has the shape of the letter L. In the crystal packing, supra­molecular chains along the a axis are formed by N—H⋯S(thione) hydrogen bonds whereby the thione S atom accepts two such bonds. The hydrogen bonding leads to alternating edge-shared eight-membered {⋯HNCS}2 and 10-membered {⋯HNNH⋯S}2 synthons. The chains are connected into layers by phen­yl–tolyl C—H⋯π inter­actions; the layers stack along the c axis with no specific inter­actions between them.
doi:10.1107/S2056989015004764
PMCID: PMC4438800  PMID: 26029430
crystal structure; hydrogen bonding; C—H⋯π inter­actions; S-substituted di­thio­carbazate
6.  Crystal structure of 7-[(2E)-2-benzyl­idene-3-oxobut­oxy]-4-methyl-2H-chromen-2-one 
Two independent mol­ecules (A and B) comprise the asymmetric unit of the title compound, C21H18O4. There are significant conformational differences between the mol­ecules relating in particular to the relative orientation of the 3-oxo-2-(phenyl­methyl­idene)but­oxy substituent with respect to the superimposable chromen-2-one residues. To a first approximation, the substituents are mirror images; both are approximately perpendicular to the chromen-2-one fused ring system with dihedral angles of 88.50 (7) (A) and 81.96 (7)° (B). Another difference between the independent mol­ecules is noted in the dihedral angles between the adjacent phenyl and but-3-en-2-one groups of 8.72 (12) (A) and 27.70 (10)° (B). The conformation about the ethene bond in both mol­ecules is E. The crystal packing features C—H⋯O, C—H⋯π(ar­yl) and π–π [Cg⋯Cg = 3.6657 (8) and 3.7778 (8) Å] stacking inter­actions, which generate a three-dimensional network.
doi:10.1107/S2056989015003084
PMCID: PMC4438806  PMID: 26029424
crystal structure; chromen-2-one; conformation
7.  Crystal structure of 1-{1-[2-(phenyl­selan­yl)phen­yl]-1H-1,2,3-triazol-4-yl}cyclo­hexan-1-ol 
Two independent mol­ecules, A and B, comprise the asymmetric unit of the title compound, C20H21N3OSe. While the benzene ring directly bound to the central triazole ring is inclined to the same extent in both mol­ecules [dihedral angles = 40.41 (12) (mol­ecule A) and 44.14 (12)° (B)], greater differences are apparent in the dihedral angles between the Se-bound rings, i.e. 74.28 (12) (mol­ecule A) and 89.91 (11)° (B). Close intra­molecular Se⋯N inter­actions of 2.9311 (18) (mol­ecule A) and 2.9482 (18) Å (B) are noted. In the crystal, supra­molecular chains along the a axis are formed via O—H⋯N hydrogen bonding. These are connected into layers via C—H⋯O and C—H⋯N inter­actions; these stack along (01-1) without directional inter­molecular inter­actions between them.
doi:10.1107/S2056989015003242
PMCID: PMC4350684  PMID: 25844248
crystal structure; organoselenium; hydrogen bonding; Se⋯N halogen bonding
8.  Crystal structure of 4-phenyl-1-{2-[(2,4,6-tri­methyl­phen­yl)selan­yl]phen­yl}-1H-1,2,3-triazole 
In the title compound, C23H21N3Se, the C-bound phenyl ring is almost coplanar with the central five-membered ring [dihedral angle = 2.84 (10)°], but the N-bound benzene ring is inclined [dihedral angle = 47.52 (10)°]. The dihedral angle between the Se-bound rings is 69.24 (9)°. An intra­molecular Se⋯N inter­action of 3.0248 (15) Å is noted. In the crystal, C—H⋯π inter­actions connect mol­ecules into double layers that stack along the a axis with no directional inter­actions between them.
doi:10.1107/S2056989015003229
PMCID: PMC4350715  PMID: 25844250
crystal structure; organoselenium; hydrogen bonding; Se⋯N halogen bonding; C—H⋯π inter­actions
9.  Crystal structure of 1-{2-[(2-meth­oxy­phen­yl)selan­yl]phen­yl}-4-phenyl-1H-1,2,3-triazole 
In the title compound, C21H17N3OSe, the dihedral angles between the central five-membered ring and the C- and N-bound rings are 17.89 (10) and 42.35 (10)°, respectively, indicating the mol­ecule is twisted. The dihedral angle between the Se-bound rings is 85.36 (10)°. A close intra­molecular Se⋯O contact of 2.8507 (13) Å is noted. In the crystal, C—H⋯O, C—H⋯N and C—H⋯π inter­actions lead to the formation of supra­molecular layers parallel to (011); these stack with no specific inter­molecular inter­actions between them.
doi:10.1107/S2056989015003230
PMCID: PMC4350762  PMID: 25844249
crystal structure; organoselenium; Se⋯O halogen bonding; hydrogen bonding; C—H⋯π inter­actions
10.  Crystal structure of 5-(1,3-di­thian-2-yl)-2H-1,3-benzodioxole 
In the title compound, C11H12O2S2, two independent but virtually superimposable mol­ecules, A and B, comprise the asymmetric unit. In each mol­ecule, the 1,3-di­thiane ring has a chair conformation with the 1,4-disposed C atoms being above and below the plane through the remaining four atoms. The substituted benzene ring occupies an equatorial position in each case and forms dihedral angles of 85.62 (9) (mol­ecule A) and 85.69 (8)° (mol­ecule B) with the least-squares plane through the 1,3-di­thiane ring. The difference between the mol­ecules rests in the conformation of the five-membered 1,3-dioxole ring which is an envelope in mol­ecule A (the methyl­ene C atom is the flap) and almost planar in mol­ecule B (r.m.s. deviation = 0.046 Å). In the crystal, mol­ecules of A self-associate into supra­molecular zigzag chains (generated by glide symmetry along the c axis) via methyl­ene C—H⋯π inter­actions. Mol­ecules of B form similar chains. The chains pack with no specific directional inter­molecular inter­actions between them.
doi:10.1107/S2056989015002455
PMCID: PMC4350690  PMID: 25844230
crystal structure; 1,3-di­thiane; conformation; 1,3-benzodioxole; C—H⋯π inter­actions
11.  Crystal structure of 2-(3-nitro­phen­yl)-1,3-di­thiane 
In the title compound, C10H11NO2S2, the 1,3-di­thiane ring has a chair conformation with the 1,4-disposed C atoms being above and below the remaining four atoms. The nitro­benzene substituent occupies an equatorial position and forms a dihedral angle of 88.28 (5)° with the least-squares plane through the 1,3-di­thiane ring. The nitro group is twisted out of the plane of the benzene ring to which it is connected, forming a dihedral angle of 10.12 (3)°. In the crystal, mol­ecules aggregate into supra­molecular zigzag chains (glide symmetry along the c axis) via nitro–benzene N—O⋯π [N—O⋯Cg(benzene) = 3.4279 (18) Å and angle at O = 93.95 (11)°] inter­actions. The chains pack with no specific inter­molecular inter­actions between them.
doi:10.1107/S2056989015002844
PMCID: PMC4350730  PMID: 25844237
crystal structure; 1,3-di­thiane; conformation; N—O⋯π inter­actions
12.  Crystal structure of 2-(3-bromo­phen­yl)-1,3-di­thiane 
In the title compound, C10H11BrS2, the 1,3-di­thiane ring has a chair conformation with the 1,4-disposed C atoms being above and below the remaining four atoms. The bromo­benzene ring occupies an equatorial position and forms a dihedral angle of 86.38 (12)° with the least-squares plane through the 1,3-di­thiane ring. Thus, to a first approximation the mol­ecule has mirror symmetry with the mirror containing the bromo­benzene ring and the 1,4-disposed C atoms of the 1,3-di­thiane ring. In the crystal, mol­ecules associate via weak methyl­ene–bromo­benzene C—H⋯π and π–π [Cg⋯Cg = 3.7770 (14) Å for centrosymmetrically related bromo­benzene rings] inter­actions, forming supra­molecular layers parallel to [10-1]; these stack with no specific inter­molecular inter­actions between them.
doi:10.1107/S2056989015002832
PMCID: PMC4350742  PMID: 25844236
crystal structure; 1,3-di­thiane; conformation; C—H⋯π inter­actions; π–π inter­actions
13.  Crystal structure of 3-[2-(thio­phen-3-yl)ethyn­yl]-2H-chromen-2-one 
In the title compound, C15H8O2S, the coumarin moiety is approximately planar (r.m.s. deviation of the 11 non-H atoms = 0.025 Å) and is slightly inclined with respect to the plane of the thio­phen-3-yl ring, forming a dihedral angle of 11.75 (8)°. In the crystal, the three-dimensional architecture features a combination of coumarin–thio­phene C—H⋯π and π–π [inter-centroid distance = 3.6612 (12) Å] inter­actions.
doi:10.1107/S2056989015002157
PMCID: PMC4350713  PMID: 25844223
crystal structure; coumarin; asymmetric alkyne; C—H⋯π inter­actions; π–π inter­actions
14.  Crystal structure of 3-[2-(4-methyl­phen­yl)ethyn­yl]-2H-chromen-2-one 
The coumarin ring system in the title asymmetric alkyne, C18H12O2, is approximately planar (r.m.s. deviation of the 11 non-H atoms = 0.048 Å), and is inclined with respect to the methyl­benzene ring, forming a dihedral angle of 33.68 (4)°. In the crystal, supra­molecular zigzag chains along the c-axis direction are formed via weak C—H⋯O hydrogen bonds, and these are connected into double layers via weak C—H⋯π inter­actions; these stack along the a axis.
doi:10.1107/S2056989014027790
PMCID: PMC4384545  PMID: 25878887
crystal structure; coumarins; asymmetric alkyne; hydrogen bonding; C—H⋯π inter­actions
15.  Crystal structure of 2-meth­oxy-2-[(4-methyl­phen­yl)sulfan­yl]-1-phenyl­ethan-1-one 
In the title β-thio­carbonyl compound, C16H16O2S, the carbonyl and meth­oxy O atoms are approximately coplanar [O—C—C—O torsion angle = −18.2 (5)°] and syn to each other, and the tolyl ring is orientated to lie over them. The dihedral angle between the planes of the two rings is 44.03 (16)°. In the crystal, supra­molecular chains are formed along the c axis mediated by C—H⋯O inter­actions involving methine and methyl H atoms as donors, with the carbonyl O atom accepting both bonds; these pack with no specific inter­molecular inter­actions between them.
doi:10.1107/S205698901402550X
PMCID: PMC4331849  PMID: 25705490
crystal structure; β-thio­carbon­yl; C—H⋯O inter­actions
16.  Crystal structure of a new monoclinic polymorph of 2,4-di­hydroxy­benzaldehyde 4-methyl­thio­semi­carbazone 
A new monoclinic (P21/c) polymorph of the title compound has the same overall conformation as a previously reported (Cc) form with the exception of the conformation of the outer hy­droxy H atom. This difference results in very different crystal packing based on hydrogen bonding, i.e. supra­molecular tubes in the new form as opposed to a three-dimensional architecture in the Cc form.
The title compound, C9H11N3O2S, is a second monoclinic (P21/c) polymorph of the previously reported Cc form [Tan et al. (2008b ▶). Acta Cryst. E64, o2224]. The mol­ecule is non-planar, with the dihedral angle between the N3CS residue (r.m.s. deviation = 0.0816 Å) and the benzene ring being 21.36 (4)°. The conformation about the C=N bond [1.292 (2) Å] is E, the two N-bound H atoms are anti, and the inner hy­droxy O-bound and outer amide N-bound H atoms form intra­molecular hydrogen bonds to the imine N atom. Crucially, the H atom of the outer hy­droxy group is approximately syn to the H atom of the benzene C atom connecting the two C atoms bearing the hy­droxy substituents. This arrangement enables the formation of supra­molecular tubes aligned along [010] and sustained by N—H⋯O, O—H⋯S and N—H⋯S hydrogen bonds; the tubes pack with no specific inter­actions between them. While the mol­ecular structure in the Cc form is comparable, the H atom of the outer hy­droxy group is approximately anti, rather than syn. This different orientation leads to the formation a three-dimensional architecture based on N—H⋯O and O—H⋯S hydrogen bonds.
doi:10.1107/S2056989014026498
PMCID: PMC4331891  PMID: 25705451
crystal structure; thio­semicarbazone; polymorph; conformation; hydrogen bonding
17.  Crystal structure of [(2R,3R,4S)-3,4-bis(acet­yloxy)-5-iodo-3,4-di­hydro-2H-pyran-2-yl]methyl acetate 
In the title compound, C12H15IO7, the 3,4-di­hydro-2H-pyran ring is in a distorted half-boat conformation with the atom bearing the acet­yloxy group adjacent to the C atom bearing the methyl­acetate group lying 0.633 (6) Å above the plane of the remaining ring atoms (r.m.s. deviation = 0.0907 Å). In the crystal, mol­ecules are linked into a supra­molecular chain along the a axis through two C—H⋯O inter­actions to the same acceptor carbonyl O atom; these chains pack with no specific inter­molecular inter­actions between them.
doi:10.1107/S205698901402564X
PMCID: PMC4331918  PMID: 25705505
Crystal structure; carbohydrate; conformation; C—H⋯O inter­actions; crystal structure
18.  Crystal structure of 2-{[2-(3-phenyl­allyl­idene)hydrazin-1-yl]thio­carbonyl­sulfanylmeth­yl}pyridinium chloride 
In the title salt of an S-substituted di­thio­carbazate, C16H16N3S2 +·Cl−, the dihedral angles between the almost planar (r.m.s deviation = 0.005 Å) central CN2S2 residue and the terminal pyridinium and phenyl rings are 80.09 (11) and 3.82 (11)°, respectively, indicating the cation has an L-shape; the amine H and thione S atoms are syn. The conformation about each of the imine [1.376 (3) Å] and ethene [1.333 (4) Å] bonds is E. The shortened C—C bond [1.444 (4) Å] linking the double bonds is consistent with conjugation in this part of the mol­ecule. In the crystal, supra­molecular layers with a jagged topology are formed by charged-assisted amine-H⋯Cl− and pyridinium-N+—H⋯Cl− hydrogen bonds. The layers stack along the a axis with no specific directional inter­actions between them.
doi:10.1107/S1600536814023228
PMCID: PMC4257274  PMID: 25484832
crystal structure; hydrogen bonding; S-substituted di­thio­carbaza­tes; salt
19.  Crystal structure of ethyl 2-[(4-bromo­phen­yl)amino]-3,4-di­methyl­pent-3-enoate 
In the title compound, C15H20BrNO2, there are two independent mol­ecules (A and B) comprising the asymmetric unit and these adopt very similar conformations. In A, the dihedral angle between the CO2 and MeC=CMe2 groups is 80.7 (3)°, and these make dihedral angles of 3.5 (3) and 84.09 (16)°, respectively, with the bromo­benzene ring. The equivalent dihedral angles for mol­ecule B are 78.4 (3), 2.1 (3) and 78.37 (12)°, respectively. The most prominent inter­actions in the crystal packing are amine-N—H⋯O(carbon­yl) hydrogen bonds between the two independent mol­ecules, resulting in non-centrosymmetric ten-membered {⋯OC2NH}2 synthons. Statistical disorder is noted for each of the terminal methyl groups of the ethyl residues.
doi:10.1107/S1600536814020832
PMCID: PMC4257164  PMID: 25484707
crystal structure; hydrogen bonding; amine
20.  Crystal structure of (3E)-3-(2,4-di­nitro­phen­oxy­meth­yl)-4-phenyl­but-3-en-2-one 
In the title compound, C17H14N2O6, the conformation about the C=C double bond [1.345 (2) Å] is E, with the ketone moiety almost coplanar [C—C—C—C torsion angle = 9.5 (2)°] along with the phenyl ring [C—C—C—C = 5.9 (2)°]. The aromatic rings are almost perpendicular to each other [dihedral angle = 86.66 (7)°]. The 4-nitro moiety is approximately coplanar with the benzene ring to which it is attached [O—N—C—C = 4.2 (2)°], whereas the one in the ortho position is twisted [O—N—C—C = 138.28 (13)°]. The mol­ecules associate via C—H⋯O inter­actions, involving both O atoms from the 2-nitro group, to form a helical supra­molecular chain along [010]. Nitro–nitro N⋯O inter­actions [2.8461 (19) Å] connect the chains into layers that stack along [001].
doi:10.1107/S1600536814018819
PMCID: PMC4186202  PMID: 25309220
crystal structure; hydrogen bonding; N⋯O inter­actions
21.  Crystal structure of (3E)-3-[(4-nitro­phen­oxy)­meth­yl]-4-phenyl­but-3-en-2-one 
In the title compound, C17H15NO4, the conformation about the C=C double bond [1.348 (2) Å] is E with the ketone group almost co-planar [C—C—C—C torsion angle = 7.2 (2)°] but the phenyl group twisted away [C—C—C—C = 160.93 (17)°]. The terminal aromatic rings are almost perpendicular to each other [dihedral angle = 81.61 (9)°] giving the mol­ecule an overall U-shape. The crystal packing feature benzene-C—H⋯O(ketone) contacts that lead to supra­molecular helical chains along the b axis. These are connected by π–π inter­actions between benzene and phenyl rings [inter-centroid distance = 3.6648 (14) Å], resulting in the formation of a supra­molecular layer in the bc plane.
doi:10.1107/S1600536814018327
PMCID: PMC4186193  PMID: 25309202
crystal structure; hydrogen bonding; π–π inter­actions
22.  Crystal structure of a new monoclinic polymorph of N-(4-methyl­phen­yl)-3-nitro­pyridin-2-amine 
Molecules in both polymorphs of the title compound display deviations from planarity owing to crystal packing effects.
The title compound, C12H11N3O2, is a second monoclinic polymorph (P21, with Z′ = 4) of the previously reported monoclinic (P21/c, with Z′ = 2) form [Akhmad Aznan et al. (2010 ▶). Acta Cryst. E66, o2400]. Four independent mol­ecules comprise the asymmetric unit, which have the common features of a syn disposition of the pyridine N atom and the toluene ring, and an intra­molecular amine–nitro N—H⋯O hydrogen bond. The differences between mol­ecules relate to the dihedral angles between the rings which range from 2.92 (19) to 26.24 (19)°. The geometry-optimized structure [B3LYP level of theory and 6–311 g+(d,p) basis set] has the same features except that the entire mol­ecule is planar. In the crystal, the three-dimensional architecture is consolidated by a combination of C—H⋯O, C—H⋯π, nitro-N—O⋯π and π–π inter­actions [inter-centroid distances = 3.649 (2)–3.916 (2) Å].
doi:10.1107/S1600536814012227
PMCID: PMC4158497  PMID: 25249854
crystal structure; amine; pyridine; polymorph; conformation
23.  Crystal structures of 1,4-di­aza­bicyclo­[2.2.2]octan-1-ium 4-nitro­benzoate dihydrate and 1,4-di­aza­bicyclo­[2.2.2]octane-1,4-diium bis­(4-nitro­benzoate): the influence of solvent upon the stoichiometry of the formed salt 
Solvent-dependent outcomes are noted in co-crystallization experiments between DABCO and 4-nitrobenzoic acid with mono- and diprotonated forms of DABCO are isolated.
The 1:1 co-crystallization of 1,4-di­aza­bicyclo­[2.2.2]octane (DABCO) with 4-nitro­benzoic acid in ethanol–water (3/1) gave the salt dihydrate C6H13N2 +·C7H4NO4 −·2H2O, (1), whereas from methanol, the salt C6H14N2 2+·2C7H4NO4 −, (2), was isolated. In (1), the cation and anion are linked by a strong N—H⋯O hydrogen bond, and the carboxyl­ate anion is close to planar [dihedral angle between terminal residues = 6.83 (9)°]. In (2), a three-ion aggregate is assembled by two N—H⋯O hydrogen bonds, and the carboxyl­ate anions are again close to planar [dihedral angles between terminal residues = 1.7 (3) and 5.9 (3)°]. Through the inter­vention of solvent water mol­ecules, which self-assemble into helical supra­molecular chains along the b axis, the three-dimensional architecture in (1) is stabilized by water–DABCO O—H⋯N and water–carboxyl­ate O—H⋯O hydrogen bonds, with additional stability afforded by C—H⋯O inter­actions. The global crystal structure comprises alternating layers of water mol­ecules and ion pairs stacked along the c axis. In the crystal of (2), the three-ion aggregates are assembled into a three-dimensional architecture by a large number of methyl­ene–carboxyl­ate/nitro C—H⋯O inter­actions as well as π–π contacts between inversion-related benzene rings [inter-centroid distances = 3.5644 (16) and 3.6527 (16) Å]. The cations and anions assemble into alternating layers along the c axis.
doi:10.1107/S1600536814011532
PMCID: PMC4120614  PMID: 25161500
crystal structure; amine; carb­oxy­lic acid; co-crystallization; salt formation
24.  2-[(3S,3aS,5R,8S,8aS)-3,8-Di­methyl­hexa­hydro-1H,4H-3a,8a-ep­oxy­azulen-5-yl]propan-2-ol 
Four independent mol­ecules (A–D) comprise the asymmetric unit of the title compound, C15H26O2, which differ only in the relative orientations of the terminal –C(Me)2OH groups [e.g. the range of Cmethyl­ene—Cmethine—Cquaternary—Ohy­droxy torsion angles is 52.7 (7)–57.1 (6)°, where the Cmethyl­ene atom is bound to an epoxide C atom]. The five-membered rings adopt envelope conformations, with the methyl­ene C atom adjacent to the methine C atom being the flap atom in each case. In each mol­ecule, the conformation of the seven-membered ring is a half-chair, with the Cmethyl­ene—Cmethine bond, flanked by methyl­ene C atoms, being the back of the chair. Supra­molecular helical chains along the b axis are found in the crystal packing, sustained by hy­droxy–epoxide O—H⋯O hydrogen bonding. Mol­ecules of A self-associate into a chain as do those of D. A third independent chain comprising B and C mol­ecules is also formed. The studied crystal is a pseudo-merohedral twin (minor component ca 21%).
doi:10.1107/S1600536814013543
PMCID: PMC4120619  PMID: 25161564
25.  Corymbolone 
The title compound, C15H24O2 [systematic name: (4S,4aR,6R,8aR)-4a-hy­droxy-4,8a-dimethyl-6-(prop-1-en-2-yl)octahydro­naphthalen-1(2H)-one], features two edge-shared six-membered rings with the hydroxyl and methyl substituents at this bridge being trans. One adopts a flattened chair conformation with the C atoms bearing the carbonyl and methyl substituents lying 0.5227 (16) and 0.6621 (15) Å, respectively, above and below the mean plane through the remaining four C atoms (r.m.s. deviation = 0.0145 Å). The second ring, bearing the prop-1-en-2-yl group, has a chair conformation. Supra­molecular helical chains along the b axis are found in the crystal packing, which are sustained by hy­droxy–carbonyl O—H⋯O hydrogen bonding.
doi:10.1107/S1600536814012938
PMCID: PMC4120577  PMID: 25161551

Results 1-25 (625)