Dichloridodi-µ(2)-hydroxido-di-µ(3)-oxido-octa-phenyl-tetra-tin(IV) dimethyl sulfoxide disolvate.

In the centrosymmetric tetra-nuclear title mol-ecule, [Sn(4)(C(6)H(5))(8)Cl(2)O(2)(OH)(2)]·2C(2)H(6)OS, the two independent tin(IV) atoms show distorted trigonal-bipyramidal SnC(2)O(3) and SnC(2)O(2)Cl coordination geometries. The four tin(IV) atoms are bridged by the hydroxo and oxo ligands, forming a ladder-like array of three edge-connected Sn(2)O(2) squares. The solvent mol-ecules are linked to the tetra-nuclear mol-ecule via O-H⋯O hydrogen bonds.

Guanidinium hexa-aqua-zinc(II) bis[tris-(3-carb-oxy-pyridine-2-carboxyl-ato)zincate].

In the title mol-ecular salt, (CH(6)N(3))(1.30)[Zn(H(2)O)(6)](0.35)[Zn(C(7)H(4)NO(4))(3)](2), the Zn(II) atom (site symmetry 3) in the anion is coordinated by three N,O-bidentate 3-carb-oxy-pyridine-2-carboxyl-ate monoanions to generate a fac-ZnN(3)O(3) octa-hedral coordination geometry. The guanidinium cation (the C atom has site symmetry 3) and the octa-hedral hexa-aqua-zinc(II) dication (the Zn(2+) cation has site symmetry -3) are occupationally disordered in a 1.30:0.35 ratio. In the crystal, the components are linked by O-H⋯O and N-H⋯O hydrogen bonds to generate infinite (001) sheets. Weak aromatic π-π stacking [centroid-centroid distance = 3.797 (8) Å] is also observed in the crystal.

Bis(guanidinium) tris-(pyridine-2,6-dicarboxyl-ato-κ(3)O(2),N,O(6))zirconate(II) tetra-hydrate.

In the title complex, (CH(6)N(3))(2)[Zr(C(7)H(3)NO(4))(3)]·4H(2)O, the Zr(IV) ion lies on a twofold rotation axes and is coordinated by six O and three N atoms of three tridentate pyridine-2,6-dicarboxyl-ate ligands, forming a slightly distorted tricapped trigonal-prismatic geometry. In the crystal, O-H⋯O and N-H⋯O hydrogen bonds link the components into a three-dimensional network.

1-(3,5-Dichloro-phen-yl)-3-(2-meth-oxy-phen-yl)triaz-1-ene.

The title mol-ecule, C(13)H(11)Cl(2)N(3)O, is almost planar and adopts a trans conformation with respect to the -N=N- bond; the dihedral angle between the rings is 3.47 (2)°. The N-N bond lengths indicate the presence of single- and double-bond characters and hence the -N=N-NH- moiety. In the crystal, inversion dimers linked by pairs of N-H⋯Cl hydrogen bonds occur, and C-H⋯π and π-π stacking interactions are also observed.

N-(2-Eth-oxy-phen-yl)formamide.

The title compound, C(9)H(11)NO(2), was obtained as an unexpected product in an attempt to synthesize a triazene ligand. The title mol-ecule is almost planar, with the formamide and eth-oxy groups oriented at 2.7 (3) and 12.9 (2)°, respectively, with respect to the mean plane of the benzene ring. In the crystal, mol-ecules are linked by inter-molecular N-H⋯O hydrogen bonds, forming a chain along the a axis. Weak C-H⋯π inter-actions with an H⋯π distance of 2.78 Šreinforce the crystal packing, resulting in a three-dimensional network.

4-[(4-Bromo-phen-yl)diazen-yl]-2-eth-oxy-aniline.

The title compound, C(14)H(14)BrN(3)O, exhibits a trans geometry about the -N=N- double bond. The dihedral angle between the benzene rings is 24.01 (5)°. An intra-molecular N-H⋯O hydrogen bond occurs. In the crystal, inter-molecular N-H⋯N hydrogen bonds between the amine groups lead to the formation of a C(8) polymeric chain along [101].

4-[(4-Chloro-phen-yl)diazen-yl]-3-meth-oxy-aniline.

The title compound, C(13)H(12)ClN(3)O, exhibits a trans geometry about the N=N double bond in the solid state. The dihedral angle between the rings is 22.20 (8)°. Inter-molecular N-H⋯O hydrogen bonds between the amine and meth-oxy groups lead to the formation of a chain-like polymer along the c axis with a C(6) graph set. There is also weak non-classical C-H⋯N hydrogen bonds involving an aromatic C-H group and a diazenyl N atom, which connect the chains into a two-dimensional framework.

Poly[[piperazine-1,4-dium [diaqua-tetra-kis-(µ-sulfanediyldiacetato)-dicerate(III)]] trihydrate].

The title compound, (C(4)H(12)N(2))[Ce(2)(C(4)H(4)O(4)S)(4)(H(2)O)(2)]·3H(2)O, features a polymeric anion with a centrosymmetric Ce(2)O(2) core and a Ce⋯Ce distance of 4.3625 (4) Å. The anions form ribbons {[Ce(2)(C(4)H(4)O(4)S)(4)(H(2)O)(2)](2-)}(n) extending along [100]. The doubly protonated piperazinium cations reside on centers of inversion and link the polymeric ribbons via N-H⋯O hydrogen bonding. Each Ce(III) cation is ten-coordinated by an O(2)S donor set from two tridentate sulfanediyldiacetate (tda) ligands, one water mol-ecule and three other tda O donors from adjacent {Ce(tda)(2)(H(2)O)} units in a distorted bicapped cubic environment. Additional O-H⋯O hydrogen bonding involving the coordinated and solvent water mol-ecules is also present. H atoms of the crystal water molecules could not be located and were not included in the refinement.

Acridinium 6-carb-oxy-pyridine-2-carboxyl-ate monohydrate.

The title compound, C(13)H(10)N(+)·C(7)H(4)NO(4) (-)·H(2)O or (acrH)(+)(pydcH)(-)·H(2)O, is a monohydrate of acridinium cations and a mono-deprotonated pyridine-2,6-dicarb-oxy-lic acid. The structure contains a range of non-covalent inter-actions, such as O-H⋯O, O-H⋯N and N-H⋯O hydrogen bonds, as well as π-π stacking [range of centroid-centroid distances = 3.4783 (5)-3.8059 (5) Å]. The N-H⋯O hydrogen bond between the donor acridinium cation and the carboxyl-ate acceptor is particularly strong. The average separation between the π-stacked acridinium planes is 3.42 (3) Å.

Statistically disordered short hydrogen bonds in (pipzH2)(cdoH)2 and a comparison with (pipzH2)(cdo)·H2O (pipz is piperazine and cdoH2 is chelidonic acid).

Two related proton-transfer compounds, namely piperazine-1,4-diium 4-oxo-4H-pyran-2,6-dicarboxylate monohydrate, C(4)H(12)N(2)(2+)·C(7)H(2)O(6)(2-)·H(2)O or (pipzH(2))(cdo)·H(2)O, (I), and piperazine-1,4-diium bis(6-carboxy-4-oxo-4H-pyran-2-carboxylate), C(4)H(12)N(2)(2+)·2C(7)H(3)O(6)(-) or (pipzH(2))(cdoH)(2), (II), were obtained by the reaction of 4-oxo-4H-pyran-2,6-dicarboxylic acid (chelidonic acid, cdoH(2)) and piperazine (pipz). In (I), both carboxyl H atoms of chelidonic acid have been transferred to piperazine to form the piperazine-1,4-diium ion. The structure is a monohydrate. All potential N-H donors are involved in N-H···O hydrogen bonds. The water molecule spans two anions via the 4-oxo group of the pyranose ring and a carboxylate O atom. The hydrogen-bonding motif is essentially two-dimensional. The structure is a pseudomerohedral twin. In the asymmetric unit of (II), the anion consists of monodeprotonated chelidonic acid, while the piperazine-1,4-diium cation is located on an inversion centre. The single carboxyl H atom is disordered in two respects. Firstly, the disordered H atom is shared equally by both carboxylic acid groups. Secondly, the H atom is statistically disordered between two positions on either side of a centre of symmetry and is engaged in a very short hydrogen-bonding interaction; the relevant O···O distances are 2.4549 (11) and 2.4395 (11) Å, and the O-H···O angles are 177 (6) and 177 (5)°, respectively. Further hydrogen bonding of the type N-H···O places the (pipzH(2))(2+) cations in pockets formed by the chains of (cdoH)(-) anions. In contrast with (I), the (pipzH(2))(2+) cations form hydrogen-bonding arrays that are perpendicular to the anions, yielding a three-dimensional hydrogen-bonding motif. The structures of both (I) and (II) also feature π-π stacking interactions between aromatic rings.

4,4'-Bipyridinium bis-(µ-4-oxo-1,4-dihydropyridine-2,6-dicarboxyl-ato)bis-[aqua-hydroxido-anti-monate(III)] dihydrate.

The title compound, (C(10)H(10)N(2))[Sb(2)(C(7)H(2)NO(5))(2)(OH)(2)(H(2)O)(2)]·2H(2)O, consists of a binuclear anion, a diprotonated 4,4'-bipyridinium cation and two uncoordinated water mol-ecules. Each Sb(III) atom is six-coordinated by one chelating 4-oxidopyridine-2,6-dicarboxyl-ate ligand, one water mol-ecule, one OH group and one bridging O atom from a neighboring carboxyl-ate group in a distorted penta-gonal-pyramidal geometry, with the OH group at the apical position. The two pyridine rings in the bipyridinium cation are twisted with respect to each other, making a dihedral angle of 22.7 (1)°. The cations are connected to the anions by N-H⋯O hydrogen bonds, forming a chain. The coordinated water mol-ecules form hydrogen bonds with the oxido O atoms of the anion, building a two-dimensional sheet, which is further connected into a three-dimensional structure by O-H⋯O and C-H⋯O hydrogen bonds and C=O⋯π inter-actions [O⋯centroid distances = 3.1785 (17), 3.4737 (19) and 3.5685 (19) Å].

Bis(9-amino-acridinium) bis-(pyridine-2,6-dicarboxyl-ato)cuprate(II) trihydrate.

The asymmetric unit of the title compound, (C(13)H(11)N(2))(2)[Cu(C(7)H(3)NO(4))(2)]·3H(2)O, consists of one [Cu(pydc)(2)](2-) dianion (pydc is pyridine-2,6-dicarboxyl-ate), two 9-amino-acridinum monocations and three uncoordinated water mol-ecules. The Cu(II) atom is coordinated by two pydc dianions acting as tridentate ligands, and forming five-membered chelate rings with copper(II) as the central atom. The Cu(II) atom is surrounded by four O atoms in the equatorial plane and two pyridine N atoms in axial positions, resulting in a distorted octa-hedral coordination geometry. In the crystal, there are two types of O-H⋯O and N-H⋯O hydrogen-bonding synthons linking the anionic and cationic fragments and the water mol-ecules, namely R(4) (4)(16), and R(4) (2)(8). There are also weak C-H⋯O hydrogen bonds, π-π stacking inter-actions [the shortest centroid-centroid distance is 3.350 (2) Å], and a C-O⋯π inter-action [O⋯centroid distance = 3.564 (2) Å], which connect the various components into a three-dimensional network.

Bis[1-(2-eth-oxy-phen-yl)-3-(4-nitro-phen-yl)triazenido]mercury(II).

In the title compound, [Hg(C(14)H(13)N(4)O(3))(2)], the central Hg atom (site symmetry 2) is six-coordinated by two tridentate 1-(2-eth-oxy-phen-yl)-3-(4-nitro-phen-yl)triazenide ligands through two N and one O atoms. The mononuclear complex mol-ecules are connected into two parallel chains by inter-molecular C-H⋯O hydrogen-bonding inter-actions. These chains are connected to each other by face-to-edge C-H⋯π inter-actions between the CH of the ethoxy groups and the aromatic rings, resulting in a two-dimensional architecture in the ac plane.

Acridinium 3-carb-oxy-pyrazine-2-carboxyl-ate.

The title ion pair, C(13)H(10)N(+)·C(6)H(3)N(2)O(4) (-), contains a protonated acridine cation and a 3-carb-oxy-pyrazine-2-carboxyl-ate monoanion, which are linked together through O-H⋯O, N-H⋯O and weak C-H⋯O hydrogen bonds. These hydrogen bonds generate a C(10) chain graph-set motif. The crystal structure is further stabilized by extensive π-π stacking inter-actions between nearly parallel [dihedral angle = 1.21(2)°] acridine systems. The shortest distance between the centroids of the six-membered rings within the cations is 3.6315 (8) Å. In addition, C-H⋯π edge-to-face inter-actions are present.

Bis[1,3-bis-(2-cyano-phen-yl)triazenido]mercury(II).

In the title compound, [Hg(C(14)H(8)N(5))(2)], the central atom is four-coordinated by two bidentate 1,3-bis-(2-cyano-phen-yl)triazenide ligands in a distorted square-planar geometry. The asymmteric unit is composed of one ligand molecule and one Hg(II) ion, which is disordered over two sites, one lying on an inversion center and the other on a general position with site-occupancy factors of 0.2378 (7) and 0.3811 (7), respectively. The monomeric mol-ecules of the complex are linked into pairs through non-classical C-H⋯N hydrogen bonds. The resulting dimeric units are assembled by translation along the crystallographic c axis into chains linked through secondary π-π inter-actions [centroid-centroid distances = 3.685 (2) and 3.574 (2) Å], as well as C-H⋯π stacking inter-actions, resulting in a two-dimensional architecture.

[1,3-Bis(2-ethoxy-phen-yl)triazenido]bromidomercury(II).

To the central atom of the title compound, [HgBr(C(16)H(18)N(3)O(2))], is attached one bromide ion and a 1,3-bis-(2-ethoxy-phen-yl)triazenide ligand through one O and two N atoms, forming a distorted square-planar geometry around the Hg(II) atom. The mononuclear complexes are linked into centrosymmetric dimers by non-classical inter-molecular C-H⋯N hydrogen bonds and by weak Hg-η(3)-arene π-inter-actions [mean distance = 3.434 (3) Å]. The resulting dimeric units are assembled into zigzag chains by translation along the crystallographic c axis through secondary C-H⋯π edge-to-face benzene ring inter-actions.

1,3-Bis(2-ethoxy-phen-yl)triazene methanol 0.33-solvate.

There are three independent mol-ecules of 1,3-bis-(2-ethoxy-phen-yl)triazene and a mol-ecule of methanol in the asymmetric unit of the title compound, C(16)H(19)N(3)O(2)·0.33CH(3)OH. Two mol-ecules related by a non-crystallographic pseudo-twofold rotation axis are linked via distinct inter-molecular N-H⋯N hydrogen bonds, leading to the formation of a dimer with an R(2) (2)(8) graph set. The third mol-ecule is connected to the methanol mol-ecule by O-H⋯N and N-H⋯O hydrogen bonds. There are a number of weak C-H⋯π inter-actions, with H⋯π distances ranging from 2.74 to 2.89 Šbetween the C-H groups and the aromatic benzene rings.

Diacridinium trans-diaqua-bis(pyrazine-2,3-dicarboxyl-ato)cobaltate(II) hexa-hydrate.

The title compound, (C(13)H(10)N)(2)[Co(C(6)H(2)N(2)O(4))(2)(H(2)O)(2)]·6H(2)O, consists of mononuclear trans-[Co(pz-2,3-dc)(2)(H(2)O)(2)](2-) complex anions, (acrH)(+) cations and uncoordinated water mol-ecules (acr is acridine and pz-2,3-dcH(2) is pyrazine-2,3-dicarboxylic acid). The Co(II) atom, which lies on a crystallographic center of symmetry, has a slightly distorted octa-hedral coordination environment, with two N and two O atoms from the (pz-2,3-dc)(2-) ligands in the equatorial plane and with two water mol-ecules in axial positions. In the crystal, the components are held together by two distinct N-H⋯O and C-H⋯O hydrogen bonds with R(2) (2)(8) graph-sets. The coordinated and uncoordinated water mol-ecules are also involved in O-H⋯O hydrogen bonds, which lead to the formation of layers with R(3) (3)(12) graph-set motifs. Extensive π-π stacking inter-actions between parallel aromatic rings of the acridinium ions, with distances ranging from 3.533 (1) to 3.613 (1) Å, occur in the structure.

Hydroxonium hydrate tris-(2,4,6-tri-amino-1,3,5-triazin-1-ium) bis-[bis-(pyri-dine-2,6-dicarboxyl-ato)cuprate(II)] pyridine-2,6-dicarboxylic acid hexa-hydrate.

The reaction of copper(II) nitrate hexa-hydrate with pyridine-2,6-dicarboxylic acid (pydcH(2)) and 2,4,6-triamino-1,3,5-triazine (melamine) in aqueous solution in a 1:2:2 molar ratio gave the title compound, (H(5)O(2))(C(3)H(7)N(6))(3)[Cu(C(7)H(3)NO(4))(2)](2)·C(7)H(5)NO(4)·6H(2)O. The hydroxonium hydrate (H(5)O(2))(+), also known as the Zundel cation, resides on a twofold rotation axis. The O-H distance is 1.274 (14) Å, the O⋯O distance is 2.518 (5) Å, and the O-H-O angle is 162 (8)°. One of the melamine H(+) cations, the uncoordinated pydcH(2), and two water mol-ecules also reside on crystallographic twofold axes. The Cu(II) atom has a tetra-gonally distorted octa-hedral coordination environment. The structure features extensive hydrogen bonding, with 21 distinct inter-actions. There is also a centrosymmetric C=O⋯π inter-action with an O⋯centroid distance of 3.288 (3) Å. The structure is similar to a mixed-valence manganese(II/III) structure but shows inter-esting differences in the metal-atom coordination. One of the water molecules is equally disordered with respect to a twofold axis.

4,4'-Bipyridine-2-hydroxy-propane-1,2,3-tricarboxylic acid (3/2).

The combination of 2-hydroxy-propane-1,2,3-tricarboxylic acid (H(3)hypta, also called citric acid) and 4,4'-bipyridine (4,4'-bipy) in a 1:1.5 molar ratio leads to the formation of the title mol-ecular cocrystal, 1.5C(10)H(8)N(2)·C(6)H(8)O(7). The asymmetric unit contains one and a half 4,4'-bipy units, with one lying across a centre of inversion, and one H(3)hypta mol-ecule. The significant differences in the C-O bond distances support the existence of the un-ionized acid mol-ecule and confirm the formation of a cocrystal. There are π-π and C-H⋯π stacking inter-actions between the aromatic rings of 4,4'-bipy [with inter-planar distances of 3.7739 (8) and 3.7970 (8) Å] and between CH groups of H(3)hypta [with an H⋯π distance of 2.63 Å]. In the crystal structure, intermolecular O-H⋯N hydrogen bonds occur and an O-H⋯O hydrogen bond occurs within the citric acid moiety.