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1.  1-[(4-{[(2-Oxo-1,2-dihydro­naphthalen-1-yl­idene)meth­yl]amino}­anilino)methyl­idene]naphthalen-2(1H)-one dihydrate 
The title compound, C28H20N2O2·2H2O, comprises a Schiff base mol­ecule with an imposed inversion centre in the middle of p-phenyl­enediamine unit and water mol­ecules of crystallization. In the structure, the Schiff base mol­ecule is present as the keto–amino tautomer with a strong intra­molecular N—H⋯O hydrogen bond. The Schiff base mol­ecules and water mol­ecules of crystallization create infinite [010] columns through O—H⋯O hydrogen bonds. Inter­molecular attractions within columns are through additional π–π inter­actions [centroid–centroid distance = 3.352 (1) Å] between parallel Schiff base mol­ecules. The columns are joined into infinite (011) layers through weak C—H⋯O hydrogen bonds. The layers pack in an assembly by van der Waals attractions, only being effective between bordering non-polar naphthalene ring systems.
PMCID: PMC3247366  PMID: 22219984
2.  trans-Diaqua­bis(ethyl­enediamine-κ2 N,N′)copper(II) bis[3-(3-pyrid­yl)propionate] dihydrate 
The asymmetric unit of the title complex, [Cu(C2H8N2)2(H2O)2](C8H8NO2)2·2H2O, contains one anion, one half-cation and one water mol­ecule. The CuII atom in the [Cu(en)2(H2O)2]2+ cation (en is ethyl­enediamine) lies on an inversion centre. The four N atoms of the en ligands in the equatorial plane around the CuII atom form a slightly distorted square-planar arrangement, while the slightly distorted Jahn–Teller octa­hedral coordination is completed by two water O atoms in axial positions. In the crystal structure, intra- and inter­molecular N—H⋯O and O—H⋯O hydrogen bonds form a three-dimensional network.
PMCID: PMC2960896  PMID: 21201981
3.  A series of N-(2-phenyl­ethyl)nitro­aniline derivatives as precursors for slow and sustained nitric oxide release agents 
A series of N-(2-phenyl­ethyl)nitro­aniline derivatives is presented, demonstrating that modest changes in the functional groups cause significant differences in mol­ecular conformation, inter­molecular inter­actions and packing.
2,4-Di­nitro-N-(2-phenyl­ethyl)aniline, C14H13N3O4, (I), crystallizes with one independent mol­ecule in the asymmetric unit. The adjacent amine and nitro groups form an intra­molecular N—H⋯O hydrogen bond. The anti conformation about the ethyl C—C bond leads to the phenyl and aniline rings being essentially parallel. Mol­ecules are linked into dimers by inter­molecular N—H⋯O hydrogen bonds, such that each amine H atom participates in a three-centre inter­action with two nitro O atoms. Though the dimers pack so that the arene rings of adjacent mol­ecules are parallel, the rings are staggered and π–π inter­actions do not appear to be favoured. 4,6-Di­nitro-N,N′-bis­(2-phenyl­ethyl)benzene-1,3-di­amine, C22H22N4O4, (II), differs from (I) in the presence of a second 2-phenyl­ethyl­amine group on the substituted ring. Compound (II) also crystallizes with one unique mol­ecule in the asymmetric unit. Both amine groups are involved in intra­molecular N—H⋯O hydrogen bonds with adjacent nitro groups. Although one ethyl group adopts an anti conformation as in (I), the other is gauche, with the result that the pendant phenyl rings are not parallel. The amine group that is part of the gauche conformation participates in a three-centre N—H⋯O hydrogen bond with the nitro group of a neighbouring mol­ecule, leading to dimers as in (I). The other amine H atom does not form any inter­molecular hydrogen bonds. The packing leads to separations of ca 3.4 Å of the parallel anti phenyl and amino­benzene rings. 2-Cyano-4-nitro-N-(2-phenyl­ethyl)aniline, C15H13N3O2, (III), differs from (I) only in having a cyano group in place of the 2-nitro group. The absence of the adjacent nitro group eliminates the intra­molecular N—H⋯O hydrogen bond. Mol­ecules of (III) adopt the same anti conformation about the ethyl group as in (I), but crystallize in the higher-symmetry monoclinic space group P21/n. The mol­ecules are linked into dimers via N—H⋯N amine–cyano hydrogen bonds, while the nitro groups are not involved in any N—H⋯O inter­actions. Owing to the different symmetry, the mol­ecules pack in a herringbone pattern with fewer face-to-face inter­actions between the rings. The closest such inter­actions are about 3.5 Å between rings that are largely slipped past one another. 4-Methyl­sulfonyl-2-nitro-N-(2-phenyl­ethyl)aniline, C15H16N2O4S, (IV), differs from (I) in having a methyl­sulfonyl group in place of the 4-nitro group. The intra­molecular N—H⋯O hydrogen bond is present as in (I). However, unlike (I), the conformation about the ethyl group is gauche, so the two arene rings are nearly per­pen­dicular rather than parallel. The packing is significantly different from the other three structures in that there are no inter­molecular hydrogen bonds involving the N—H groups. The mol­ecules are arranged in tetra­gonal columns running along the c axis, with the aniline rings mostly parallel and separated by ca 3.7 Å. Taken together, these structures demonstrate that modest changes in functional groups cause significant differences in mol­ecular conformation, inter­molecular inter­actions and packing.
PMCID: PMC3818095  PMID: 24192194
crystal structure; N-(2-phenyl­ethyl)nitro­aniline derivatives; secondary amines; nitric oxide release agents
4.  {5,5′-Dihydr­oxy-2,2′-[o-phenyl­enebis­(nitrilo­methyl­idyne)]diphenolato}nickel(II) dihydrate 
In the title complex, [Ni(C20H14N2O4)]·2H2O, the NiII ion is in an essentially square-planar geometry involving an N2O2 atom set of the tetra­dentate Schiff base ligand. The Ni atom lies on a crystallographic twofold rotation axis. The asymmetric unit contains one half-mol­ecule of the complex and a water mol­ecule. An inter­molecular O—H⋯O hydrogen bond forms a four-membered ring, producing an R 1 2(4) ring motif involving a bifurcated hydrogen bond to the phenolate O atoms of the complex mol­ecule. In the crystal structure, mol­ecules are linked by π–π stacking inter­actions, with centroid–centroid distances in the range 3.5750 (11)–3.7750 (11) Å. As a result of the twofold symmetry, the central benzene ring makes the same dihedral angle of 15.75 (9)° with the two outer benzene rings. The dihedral angle between the two hydroxy­phenyl rings is 13.16 (5)°. In the crystal structure, mol­ecules are linked into infinite one-dimensional chains by directed four-membered O—H⋯O—H inter­actions along the c axis and are further connected by C—H⋯O and π–π stacking into a three-dimensional network. An inter­esting feature of the crystal structure is the short Ni⋯O, O⋯O and N⋯N inter­actions which are shorter than the sum of the van der Waals radii of the relevant atoms. The crystal structure is stabilized by inter­molecular O—H⋯O and C—H⋯O hydrogen bonds and by π–π stacking inter­actions.
PMCID: PMC2960688  PMID: 21201624
5.  A new Schiff base nickel(II) complex: {5,5′-dihydr­oxy-2,2′-[o-phenyl­enebis(nitrilo­methyl­idyne)]diphenolato}nickel(II) methanol disolvate 
The monomeric title nickel(II) complex of a salicylaldimine, [Ni(C20H14N2O4)]·2CH3OH, was obtained by the reaction of 2,4-dihydroxy­benzaldehyde and 1,2-phenyl­enediamine with nickel(II) acetate. The NiII atom is coordinated by two N atoms [Ni—N = 1.839 (2) Å] and two O atoms [Ni—O = 1.8253 (19) Å] in an approximately square-planar geometry. In the crystal structure, inter­molecular O—H⋯O hydrogen bonds link the mol­ecules into a chain along [001].
PMCID: PMC2971377  PMID: 21578111
6.  An octa­nuclear zinc(II) complex with 6,6′-dihydr­oxy-2,2′-[1,2-phenyl­enebis(nitrilo­methyl­idyne)]diphenol 
The asymmetric unit of the title compound, tetra­aqua­tetrakis­{μ3-6,6′-di­oxido-2,2′-[1,2-phenyl­enebis(nitrilo­methyl­idyne)]diphenolato}octa­zinc(II) dimethyl sulfoxide tetra­solvate dihydrate, [Zn8(C20H12N2O4)4(H2O)4]·4C2H6OS·2H2O, contains one quarter of a ZnII octa­nuclear complex with symmetry, one dimethyl sulfoxide mol­ecule and one half of a water mol­ecule which lies on a twofold rotation axis. The ZnII atoms of the octa­nuclear complex have two different five-coordinate environments, viz. ZnN2O3 and ZnO5. All eight ZnII centers adopt a distorted square-pyramidal coordination; four ZnII ions have the N2O2 tetra­dentate Schiff base ligand bound in a basal plane and the coordinated water mol­ecule occupying the apical site, while the remaing four ZnII ions are bound by five O atoms from three Schiff base ligands. In the crystal structure, ZnII complex mol­ecules, coordinated and uncoord­inated water mol­ecules and dimethyl sulfoxide mol­ecules are linked via O—H⋯O and C—H⋯O hydrogen bonds and C—H⋯π inter­actions, forming a three-dimensional framework.
PMCID: PMC2961853  PMID: 21202773
7.  (1E,1′E)-4,4′-[1,1′-(Hydrazine-1,2-diyl­idene)bis­(ethan-1-yl-1-yl­idene)]diphenol dihydrate 
The asymmetric unit of the title compound, C16H16N2O2·2H2O, contains one half-mol­ecule of diphenol and one water mol­ecule. The complete diphenol mol­ecule is generated by a crystallographic inversion centre. In the mol­ecule, the central Cmeth­yl—C=N—N=C—Cmeth­yl plane makes a dihedral angle of 8.88 (6)° with its adjacent benzene ring. In the crystal, the components are linked by O—H⋯N and O—H⋯O hydrogen bonds into a three-dimensional network. The crystal structure is further stabilized by a weak C—H⋯π inter­action.
PMCID: PMC3200688  PMID: 22064463
8.  Ethane-1,2-diaminium dipicrate dihydrate 
The title compound, C2H10N2 2+·2C6H2N3O7 −·2H2O, crystallizes with a complete picrate anion and half an ethyl­enediammonium dication on a mirror plane, and two half-water mol­ecules (both on a mirror plane) in the asymmetric unit. The N atoms from separate half ethyl­enediammonium dications are in near proximity to a phenolate O atom and two o-NO2 groups from the picrate anion, which, along with the water mol­ecule form N—H⋯O, O—H⋯O and weak intermolecular C—H⋯O hydrogen bonds that create cyclic patterns with graph-set descriptors R 2 4(8), R 4 4(12), and R 4 4(16). The crystal packing is strongly influenced by these inter­molecular inter­actions between symmetry-related water mol­ecules, the half ethyl­enediammonium dication and the picrate anion, forming a three-dimensional supermolecular structure.
PMCID: PMC3052063  PMID: 21522391
9.  6,6′-Dihydr­oxy-2,2′-[(pentane-1,5-diyl­dioxy)bis­(nitrilo­methyl­idyne)]diphenol 
The mol­ecule of the title compound, C19H22N2O6, assumes a W-shaped configuration with the dihedral angle between the two halves of the mol­ecule being 82.48 (5)°. There is one half-mol­ecule in the asymmetric unit with a crystallographic twofold rotation axis passing through the central C atom of the five methylene groups in the [—CH=N—O—(CH2)5—O—N=CH—] bridge. The dihedral angle formed by the two benzene rings in each mol­ecule of the title compound is 84.18 (4)°. There are strong intra­molecular O—H⋯N and O—H⋯O hydrogen bonds and weak inter­molecular π–π stacking inter­actions between neighbouring benzene rings, and the inter­molecular plane-to-plane distances are 3.488 (2) and 3.841 (3) Å along the b and c axes, respectively. In the crystal structure, inter­molecular O—H⋯O hydrogen bonds link each mol­ecule to two others, forming an infinite three-dimensional supra­molecular structure.
PMCID: PMC2962213  PMID: 21203294
10.  2,3-Diamino­phenazine tetra­hydrate 
The title compound, C12H10N4·4H2O, was obtained from a room-temperature solution of o-phenyl­enediamine and copper acetate. In the crystal structure, there are significant π–π stacking inter­actions, with a centroid–centroid separation of 3.575 (2) Å. In addition, inter­molecular O—H⋯O, N—H⋯O, N—H⋯N and O—H⋯N hydrogen bonds link 2,3-diamino­phenazine mol­ecules and water mol­ecules, forming a three-dimensional framework.
PMCID: PMC2961609  PMID: 21202528
11.  Hexaaqua­(5,7-dihydr­oxy-4-oxo-2-phenyl-4H-chromene-8-sulfonato)calcium(II) 5,7-dihydr­oxy-4-oxo-2-phenyl-4H-chromene-8-sulfonate trihydrate 
In the title compound, [Ca(C15H9O7S)(H2O)6](C15H9O7S)·3H2O, the Ca centre has a distorted deca­hedral geometry, coordinated by six O atoms from water mol­ecules and one sulfonate O atom. The crystal structure is stabilized by aromatic π–π inter­actions, with centroid–centroid distances of 3.765 (5) and 3.896 (5) Å between the phenyl ring and the benzene ring of the chromene unit of neighbouring mol­ecules. In addition, the stacked mol­ecules exhibit inter- and intra­molecular O—H⋯O hydrogen bonds, including the uncoordinated water mol­ecules.
PMCID: PMC2959999  PMID: 21581174
12.  N 1-[(1H-Imidazol-2-yl)methyl­idene]-N 4-phenyl­benzene-1,4-di­amine 
The title compound, C16H14N4, is non-planar with dihedral angles between the planes of the imidazole and phenyl­enedi­amine rings of 30.66 (4)° and between the planes of the phenyl­enedi­amine and N-phenyl rings of 56.63 (7)°. In the crystal, mol­ecules are connected by N—H⋯N hydrogen bonds, generating a chain extending along the b-axis direction. The crystal structure is also stabilized by C—H⋯π inter­actions between N-phenyl and imidazole rings and slipped π–π stacking inter­actions between imidazole rings [centroid–centroid distance = 3.516 (4) Å] giving an overall two-dimensional layered structure lying parallel to (010).
PMCID: PMC4120595  PMID: 25161587
crystal structure
13.  Crystal structure of N-[(2S,5R)-4-oxo-2,3-diphenyl-1,3-thia­zinan-5-yl]acetamide 0.375-hydrate 
The crystal structure of the title compound displays boat and half-chair configurations of the thia­zine ring.
The asymmetric unit of the title compound, C18H18N2O2S.0.375H2O, has two independent organic mol­ecules (A and B) and 3/4 of a water mol­ecule distributed over three sites. In mol­ecule A, the 1,3-thia­zine ring is in a boat conformation, with the C atoms at the 2- and 5-positions out of the plane. The angle between the two phenyl rings is 51.70 (12)°. In mol­ecule B, the thia­zine ring is in a half-chair conformation, with the S atom forming the back of the half-chair. The angle between the two phenyl rings is 84.44 (14)°. The A mol­ecule features an intra­molecular N—H⋯O hydrogen bond, which closes an S(5) ring motif. In the crystal, the corresponding N—H grouping of the B mol­ecule participates in an inter­molecular hydrogen bond to the A mol­ecule. The A mol­ecule participates in a C—H⋯O inter­action back to the B mol­ecule, whilst the B mol­ecule features an intra­molecular C—H⋯O link, which generates an S(10) loop.
PMCID: PMC4331885
crystal structure; thia­zine ring; boat; half-chair; 1,3-thia­zin-4-one; hydrogen bonding
14.  Crystal structure of a tetra­kis-substituted pyrazine compound: 2,3,5,6-tetra­kis­(bromo­meth­yl)pyrazine1  
The title molecule crystallizes with two half-molecules in the asymmetric unit, the whole molecules being generated by twofold rotation symmetry. In the crystal, there are two interpenetrating three-dimensional networks involving the individual molecules that are linked by C—H⋯Br and Br⋯Br interactions.
The title compound, C8H8Br4N2, crystallizes in the enanti­omorphic-defining space group P41212 and has a refined Flack x parameter of 0.04 (4). In the asymmetric unit, there are two half-mol­ecules; the whole mol­ecules (A and B) are generated by twofold rotation symmetry. In mol­ecule A, the twofold axis is normal to the pyrazine ring passing through the centre of the ring, while in mol­ecule B, the twofold rotation axis lies in the plane of the pyrazine ring bis­ecting the C—C aromatic bonds. The two mol­ecules are pseudo-mirror images of one another, and the best fit of the two mol­ecules was obtained for inverted mol­ecule B on mol­ecule A, with an r.m.s. deviation of 0.1048 Å and a maximum deviation of any two equivalent atoms of 0.2246 Å. In the crystal, the A mol­ecules are linked by weak C—H⋯Br hydrogen bonds and Br⋯Br inter­actions [3.524 (3) Å], forming a three-dimensional framework. The B mol­ecules are also linked by weak C—H⋯Br hydrogen bonds and Br⋯Br inter­actions [3.548 (3) Å], forming a three-dimensional network that inter­penetrates the network of A mol­ecules.
PMCID: PMC4158553  PMID: 25249852
crystal structure; tetra­kis-substituted; pyrazine; chiral
15.  Bis(μ2-2-chloro­benzoato-κ2 O:O′)bis­[(2-chloro­benzoato-κO)(1,10-phenanthroline-κ2 N:N′)copper(II)] dihydrate 
In the title compound, [Cu2(C7H4ClO2)4(C12H8N2)2]·2H2O, the two crystallographically independent dinuclear complex mol­ecules, A and B, have different Cu⋯Cu separations, viz. 3.286 (1) Å in A and 3.451 (1) Å in B. Both independent mol­ecules reside on inversion centres, so the asymmetric unit contains a half-mol­ecule each of A and B and two water mol­ecules. Each Cu atom has a square-pyramidal environment, being coordinated by two O atoms from two bridging 2-chloro­benzoate ligands, one O atom from a monodentate 2-chloro­benzoate ligand and two N atoms from a 1,10-phenanthroline ligand. The water mol­ecules can also be considered as coordinating ligands, which complete the coordination geometry up to distorted octa­hedral with elongated Cu—O distances, viz. 3.024 (3) Å in A and 2.917 (3) Å in B. In the crystal, weak inter­molecular C—H⋯O inter­actions contribute to the consolidation of the crystal packing.
PMCID: PMC3212258  PMID: 22090915
16.  Aqua­chloridobis(diphenyl­glyoximato-κ2 N,N′)cobalt(III) dihydrate 
The asymmetric unit of the title complex, [Co(C14H11N2O2)2Cl(H2O)]·2H2O or [Co(dpgH)2Cl(H2O)]·2H2O, where dpgH− is diphenyl glyoximate, consists of one-half of a [Co(dpgH)2Cl(H2O)] complex and one solvent water mol­ecule. The complex is completed through inversion symmetry, with the CoIII atom situated at the centre of symmetry. The coordination geometry around the CoIII atom is distorted octa­hedral with the four N atoms of the two dpgH− ligands forming an approximate square plane with N—Co—N bite angles of 81.13 (14) and 98.87 (14)°. The Cl− ligand and the water mol­ecule are disordered in a 1:1 ratio and are in the axial positions, almost perpendicular to the plane of the glyoximate ligands [O—Co—Cl = 175.3 (10)°]. The two glyoximate ligands are linked by strong intra­molecular O—H⋯O hydrogen bonds. In addition, O—H⋯O inter­actions involving the solvent water mol­ecules and O—H⋯N hydrogen-bonding inter­actions are also observed. The solvent water mol­ecule is disordered over five positions with different occupancies.
PMCID: PMC3089102  PMID: 21754336
17.  Phenazine–naphthalene-1,5-diamine–water (1/1/2) 
The asymmetric unit of the title compound, C12H8N2·C10H10N2·2H2O, contains one half-mol­ecule of phenazine, one half-mol­ecule of naphthalene-1,5-diamine and one water mol­ecule. The phenazine and naphthalene-1,5-diamine mol­ecules are located on inversion centers. The water mol­ecules serve as bridges between the naphthalene-1,5-diamine mol­ecules and also between the naphthalene-1,5-diamine and phenazine mol­ecules. The naphthalene-1,5-diamine and water mol­ecules are connected via N—H⋯O and O—H⋯N hydrogen bonds, forming a T4(2) motif. They are arranged into a two-dimensional polymeric structure parallel to (10) in which the water mol­ecule is a single donor and a double acceptor, whereas the amino group is a double donor and a single acceptor in the hydrogen bonding. These two-dimensional assemblies alternate with the layers of phenazine mol­ecules arranged into a herringbone motif. Each phenazine mol­ecule is hydrogen bonded to two water mol­ecules and thus a three-dimensional framework of hydrogen-bonded mol­ecules is generated.
PMCID: PMC2972038  PMID: 21578891
18.  Bis{4-[(Z)-N′-(4-hydroxy­benzyl­idene)hydrazino]-8-(trifluoro­meth­yl)quinolinium} sulfate dihydrate 
The title compound, 2C17H13F3N3O+·SO4 2−·2H2O, crystallizes with four independent cations (A, B, C and D) in the asymmetric unit, which is composed of two groups of two cations, one anion and two water mol­ecules (Z′ = 2). The dihedral angle between the mean planes of the 4-hydroxy­phenyl and quinolinium groups is 8.9 (7)° in A, 30.1 (6)° in B, 28.8 (8)° in C and 12.8 (1)° in D. The crystal packing is stabilized by inter­molecular O—H⋯O and N—H⋯O hydrogen bonding between H atoms from 4-hydroxy­phenyl O atoms and the O atoms of nearby water molecules and sulfate anions, as well as H atoms from the N atom of the hydrazino group to O atoms of neighboring sulfate anions, linking the components into chains with the 4-hydroxy­phenyl and quinolinium rings parallel to the (011) plane. There is also an extensive array of inter­molecular hydrogen bonds between water mol­ecules themselves and with sulfate O atoms, as well as hydrogen-bond inter­actions between H atoms from the hydrazino group and sulfate O atoms. In addition, inter­molecular π–π stacking inter­actions occur between nearby 4-hydroxy­phenyl and quinolinium groups, with distances between the centroids of inter­acting rings in the range 3.4140 (9)–3.9659 (9) Å.
PMCID: PMC2960448  PMID: 21201506
19.  Hexa­kis­(3-chloro-2-methyl­anilinium) cyclo­hexa­phosphate dihydrate 
In the organic/inorganic salt hydrate, 6C7H9ClN+·P6O18 6−·2H2O, the cyclo­hexa­phosphate anion resides on an inversion centre. The asymmetric unit consists of three cations, one half-anion and a water mol­ecule. In the crystal, the water mol­ecules and the [P6O18]6− anions are linked by O—H⋯O hydrogen bonds, generating infinite layers parallel to the ab plane. These layers are inter­connected by the organic cations through N—H⋯O hydrogen bonds.
PMCID: PMC3914095  PMID: 24527000
20.  1-Methyl-1H-benzimidazole-2(3H)-thione 
The title compound, C8H8N2S, was prepared by the condensation of N-methyl-1,2-phenyl­enediamine and carbon disulfide. The crystal structure is stabilized by a C—H⋯π inter­action between a benzene H atom and the benzene ring of a neighbouring mol­ecule, and by inter­molecular N—H⋯S inter­actions.
PMCID: PMC2961472  PMID: 21202650
21.  Benzoic acid–2-{(E)-[(E)-2-(2-pyridyl­methyl­idene)hydrazin-1-yl­idene]meth­yl}pyridine (2/1) 
The asymmetric unit of the title cocrystal, C12H10N4·2C7H6O2, comprises a single mol­ecule of benzoic acid and one half-mol­ecule of 2-pyridine­aldazine situated about a centre of inversion. The carboxyl group is coplanar with the benzene ring to which it is connected [O—C—C—C = −172.47 (12)°] and similarly, the 2-pyridine­aldazine mol­ecule is planar (r.m.s. deviation of the 16 non-H atoms = 0.017 Å). In the crystal, mol­ecules are connected into a non-planar three-mol­ecule aggregate [dihedral angle between the benzene and pyridyl ring connected by the hydrogen bond = 61.30 (7)°] with a twisted Z-shape. Layers of 2-pyridine­aldazine mol­ecules in the ab plane are sandwiched by benzoic acid mol­ecules being connected by O—H⋯N and C—H⋯O inter­actions, the latter involving the carbonyl O atom so that each benzoic acid mol­ecule links three different 2-pyridine­aldazine mol­ecules. Inter­digitated layers stack along the c axis.
PMCID: PMC3009141  PMID: 21589004
22.  5,8-Bis[bis­(pyridin-2-yl)amino]-1,3,4,6,7,9,9b-hepta­aza­phenalen-2(1H)-one dimethyl sulfoxide monosolvate dihydrate 
In the asymmetric unit of the title compound, C26H17N13O·C2H6OS·2H2O, there is one independent hepta­zine-based main mol­ecule, one dimethyl sulfoxide mol­ecule and two water mol­ecules as solvents. The tri-s-triazine unit is substituted with two dipyridyl amine moieties and a carbonylic O atom. As indicated by the bond lengths in this acid unit of the hepta­zine derivative [C=O = 1.213 (2) Å, while the adjacent C—N(H) bond = 1.405 (2) Å] it is best described by the keto form. The cyameluric nucleus is close to planar (r.m.s. deviation = 0.061 Å) and the pyridine rings are inclined to its mean plane by dihedral angles varying from 47.47 (5) to 70.22 (5)°. The host and guest mol­ecules are connected via N—H⋯O, O—H⋯O and O—H⋯N hydrogen bonds, forming a four-membered inversion dimer-like arrangement enclosing an R 4 4(24) ring motif. These arrangements stack along [1-10] with a weak π–π inter­action [inter-centroid distance = 3.8721 (12) Å] involving adjacent pyridine rings. There are also C—H⋯N and C—H⋯O hydrogen bonds and C—H⋯π inter­actions present within the host mol­ecule and linking inversion-related mol­ecules, forming a three-dimensional structure.
PMCID: PMC3998556  PMID: 24826156
23.  {6,6′-Diethoxy-2,2′-[4,5-dimethyl-o-phenylenebis(nitrilomethylidyne)]di­phenolato}nickel(II) dihydrate 
In the title complex, [Ni(C26H26N2O4)]·2H2O, the NiII ion, lying on a twofold crystallographic rotation axis, has a square-planar geometry, being coordinated by the N2O2 unit of the tetra­dentate Schiff base ligand. The asymmetric unit of the title compound comprises one-half of the complex mol­ecule and one of the water mol­ecules of crystallization. The water H atoms form bifurcated O—H⋯(O,O) hydrogen bonds with the O atoms of the phenolato and eth­oxy groups with R 1 2(5) and R 1 2(6) ring motifs. The dihedral angle between the central benzene ring and the two outer benzene rings are 4.07 (11) and 3.99 (12)°. The dihedral angle between the two O–Ni–N coordination planes is only 0.77 (11)°. In the crystal structure, the mol­ecules are linked together into extended chains along the c axis by inter­molecular O—H⋯O and C—H⋯O inter­actions. An inter­esting feature of the crystal structure is a short inter­molecular C ⋯ C [3.355 (3) Å] contact, which is shorter than the sum of the van der Waals radii. The crystal structure may be further stabilized by inter­molecular π–π inter­actions [centroid–centroid distances in the range 3.5758 (13)–3.6337 (13) Å].
PMCID: PMC2977562  PMID: 21583748
24.  catena-Poly[[[dibromidomanganese(II)]-μ-2,2′-bipyrimidine-κ4 N 1,N 1′:N 3,N 3′]dihydrate] 
The asymmetric unit of the title compound, {[MnBr2(C8H6N4)]·2H2O}n, contains one half of a repeat unit of the neutral linear coordination polymer and a solvent water mol­ecule, with the MnII ion on a crystallographic twofold axis. In the polymer, inversion-related MnII ions are bridged by the bis-chelating 2,2′-bipyrimidine (bpym) ligands, thereby forming a chain structure along the c-axis direction, and are six-coordinated in a distorted cis-N4Br2 octa­hedral environment by four N atoms of twofold-related bpym ligands and twofold-related bromide anions. In the crystal, the complex polymers and solvent water mol­ecules are linked by inter­molecular O—H⋯Br and C—H⋯O hydrogen bonds, forming a two-dimensional layered structure extending parallel to the ac plane.
PMCID: PMC3238743  PMID: 22199620
25.  Poly[[tetra­aqua­bis­(μ3-1H-imidazole-4,5-dicarboxyl­ato)tetra­kis­(μ2-1H-imidazole-4,5-dicarboxyl­ato)tricobalt(II)diytterbium(III)] dihydrate] 
The asymmetric unit of the title compound, {[Co3Yb2(C5H2N2O4)6(H2O)4]·2H2O}n, contains one YbIII ion, two CoII ions (one situated on an inversion centre), three imidazole-4,5-dicarboxyl­ate ligands, two coordinated water mol­ecules and one uncoordinated water mol­ecule. The YbIII ion is seven-coordinated, in a monocapped trigonal prismatic coordination geometry, by six O atoms from three imidazole-4,5-dicarboxyl­ate ligands and one water O atom. Both CoII ions are six-coordinated in a slightly distorted octa­hedral geometry. The CoII ion that is located on an inversion center is coordinated by two O atoms from two water mol­ecules, as well as two O atoms and two N atoms from two imidazole-4,5-dicarboxyl­ate ligands. The second CoII ion is bonded to four O atoms and two N atoms from four imidazole-4,5-dicarboxyl­ate ligands. These metal coordination units are connected by bridging imidazole-4,5-dicarboxyl­ate ligands, generating a three-dimensional network. The crystal structure is further stabilized by N—H⋯O, O—H⋯O and C—H⋯O hydrogen-bonding inter­actions involving the water mol­ecules and the imidazole-4,5-dicarboxyl­ate ligands.
PMCID: PMC3212186  PMID: 22090888

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