Regular High-Nuclearity Species from Square Building Blocks: A Triangular 3 × [2 × 2] Ni12 Complex Generated by the Self-assembly of Three [2 × 2] Ni4 Molecular Grids

Crystal structure, Hirshfeld surface analysis and geometry optimization of 2-hydroxyimino-N-[1-(pyrazin-2-yl)ethylidene]propanohydrazide

The title compound, 2-hy­droxy­imino-N-[1-(2-pyrazin­yl)ethyl­idene]propane­hydrazide, is a ligand able to form polynuclear metal complexes. The mol­ecule is not planar due to a twist between the oxime and amide groups. In the crystal, mol­ecules are linked by O—H⋯O hydrogen bonds into supra­molecular chains.

In the mol­ecule of the title compound, C₉H₁₁N₅O₂, the oxime and hydrazide groups are situated in a cis-position in relation to the C—C bond linking the two functional groups. The CH₃C(=NOH)C(O)NH fragment deviates from planarity because of a twist between the oxime and amide groups. In the crystal, mol­ecules are linked by O—H⋯O hydrogen bonds, forming zigzag chains in the [013] and [03] directions.

Fascinating interlocked triacontanuclear giant nanocages

We report herein three air, thermal and solvent stable interlocked triacontanuclear giant nanocages, generated using a node and spacer concept. Interestingly, the crystal structures of the cages are not only nano-dimensional but also exist in the nano-dimension range, which was corroborated with microscopic images. The combination of microscopic and crystallographic data, in effect, led us to a unique advantageous situation of generating nanomaterials with hard-to-come-by structural information at the molecular level.

A ring of grids: a giant spin-crossover cluster

Mononuclear and icosanuclear spin-crossover complexes, [Fe^II(HL)₂](BF₄)₂ (1) and [FeII20(L)₂₄](BF₄)₁₆ (2), were synthesized using an asymmetric multidentate ligand (HL). 1 has a bis-chelate structure with two protonated ligands, while 2 has a ring-shape structure comprising four [2 × 2] grid moieties and four mononuclear units.

Crystal structure, Hirshfeld surface analysis and DFT studies of (E)-4-methyl-2-{[(4-methyl-phen-yl)imino]-meth-yl}phenol

In the title compound, C15H15NO, the configuration of the C=N bond of the Schiff base is E, and an intra-molecular O-H⋯N hydrogen bond is observed, forming an intra-molecular S(6) ring motif. The phenol ring is inclined by 45.73 (2)° from the plane of the aniline ring. In the crystal, mol-ecules are linked along the b axis by O-H⋯N and C-H⋯O hydrogen bonds, forming polymeric chains. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the packing arrangement are from H⋯H (56.9%) and H⋯C/C⋯H (31.2%) inter-actions. The density functional theory (DFT) optimized structure at the B3LYP/ 6-311 G(d,p) level is compared with the experimentally determined mol-ecular structure, and the HOMO-LUMO energy gap is provided. The crystal studied was refined as an inversion twin.

Tetranuclear MnII, CoII, CuII and ZnII grid complexes of an unsymmetrical ditopic ligand: synthesis, structure, redox and magnetic properties

Synthesis towards the preparation of an unsymmetrical binucleating Schiff-base ligand, (H₂L) is discussed. It has been synthesized by reacting methyl 6-(hydrazinecarbonyl)picolinate with 2-hydroxy acetophenone. The ligand (H₂L) comprises two different asymmetric binding pockets; however, when reacted with Mn(ii), Co(ii), Cu(ii) and Zn(ii) salts, very stable self-assembled [2 × 2] grid complexes form regardless of the employed metal-to-ligand ratio. The obtained complexes [Mn₄L₄]·(CH₃CN) (1), [Co₄L₄]·(CHCl₃) (2), [Cu₄L₄]·(CHCl₃) (3) and [Zn₄L₄] (4) have been fully characterized by physicochemical methods, including ESI mass spectrometry and X-ray crystallographic analyses, and their EPR, magnetic and redox properties are discussed. All discussed complexes self-assembled in a 'head-to-tail' fashion leading to [2 × 2] grid architectures. Mn, Co and Cu grid complexes show weak to moderate antiferromagnetic coupling among the four metal centers. The high stability of the grid structures is in line with the lack of any observable dissociation or exchange between metal ions in solution. Complexes 1 and 2 show four quasi-reversible to irreversible oxidative responses in cyclic voltammograms at a glassy carbon working electrode in 1,2-dichlorobenzene and at a platinum working electrode in dichloromethane, respectively.

Diaquabis[4-(dimethylamino)pyridine-κN 1]bis[2-(1,3-dioxo-2,3-dihydro-1H-isoindol-2-yl)acetato-κO 1]cobalt(II)

In the mononuclear title complex, [Co(C10H6NO4)2(C7H10N2)2(H2O)2], the CoII ion is located on an inversion centre and has a distorted octahedral coordination geometry of type CoN2O4 by two N atoms from the two 4-(dimethylamino)pyridine (DMAP) ligands, two carboxylate O atoms from the two deprotonated N-phthaloylglycine (Nphgly) ligands [systematic name: 2-(1,3-dioxo-2,3-dihydro-1H-isoindol-2-yl)acetate] and two coordination water molecules. In the crystal, O—H...O, C—H...O hydrogen bonds and π–π stacking interactions link the molecules into the supramolecular structure.

Crystal structure of 4-[(3-meth-oxy-2-oxidobenzyl-idene)azaniumyl]-benzoic acid methanol monosolvate

In the crystal of the title compound, C15H13NO4·CH3OH, the Schiff base mol-ecule exists in the zwitterionic form; an intra-molecular N-H⋯O hydrogen bond stabilizes the mol-ecular structure. The benzene rings are nearly co-planar, subtending a dihedral angle of 5.34 (2)°. In the crystal, classical O-H⋯O and weak C-H⋯O hydrogen bonds link the Schiff base mol-ecules and methanol solvent mol-ecules into a three-dimensional supra-molecular architecture. The crystal studied was refined as an inversion twin.

Crystal structure and Hirshfeld surface analysis of (E)-2,4-di-tert-butyl-6-[(3-chloro-4-methyl-phenyl-imino)-meth-yl]phenol

The title Schiff base compound, C22H28ClNO, shows mirror symmetry with all its non-H atoms, except the tert-butyl groups, located on the mirror plane. There is an intra-molecular O-H⋯N hydrogen bond present forming an S(6) ring motif. In the crystal, the mol-ecules are connected by C-H⋯π inter-actions, generating a three-dimensional supra-molecular structure. Hirshfeld surface analysis and two dimensional fingerprint plots were used to analyse the inter-molecular inter-actions present in the crystal, indicating that the most important contributions for the crystal packing are from H⋯H (68.9%) and C⋯H/H⋯C (11.7%) inter-actions.

Crystal structure of bis-[(S)-2-(2-hy-droxy-benzyl-amino)-4-methyl-penta-noato-κ2 N,O 1](1,10-phenanthroline-κ2 N,N')cadmium dihydrate

The asymmetric unit of the mononuclear mixed-ligand title complex, [Cd(C13H18NO3)2(C12H8N2)]·2H2O, contains two crystallographically independent mol-ecules that differ insignificantly in their geometrical parameters. In both, the CdII cation lies on a twofold rotation axis and is coordinated in a distorted octa-hedral fashion to two monodeprotonated residues of the l-leucine-derived ligand (S)-2-(2-hy-droxy-benzyl-amino)-4-methyl-penta-noic acid (L), as well as to a 1,10-phenanthroline ligand in a κ2 N,N' mode. The former coordinate in an N,O-chelating mode, exhibiting a trans-N,N' mutual disposition. The phenolic oxygen donor groups remain protonated and do not coordinate to the cation but take part in intra- and inter-molecular hydrogen bonds. In the crystal, O-H⋯O hydrogen bonding results in the formation of a three-dimensional network structure. The contribution to the electron density of two disordered water mol-ecules was removed with the SQUEEZE procedure in PLATON [Spek (2015 ▸). Acta Cryst. C71, 9-18]. The studied crystal was refined as a two-component inversion twin. The title complex was also characterized by IR and 1H NMR spectroscopic methods.

Crystal structure and Hirshfeld surface analysis of tetra-aqua-bis-(isonicotinamide-κN 1)nickel(II) fumarate

The reaction of NiCl2 with fumaric acid and isonicotinamide in a basic solution produces the title complex, [Ni(C6H6N2O)2(H2O)4](C4H2O4). The nickel(II) ion of the complex cation and the fumarate anion are each located on an inversion centre. The NiII ion is coordinated octa-hedrally by four water O atoms and two N atoms of isonicotinamide mol-ecules. The fumarate anion is linked to neighbouring complex cations via Owater-H⋯Ofumarate hydrogen bonds. In the crystal, the complex cations are further linked by O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds, forming a three-dimensional supra-molecular architecture. Hirshfeld surface analysis and two-dimensional fingerprint plots were used to analyse the inter-molecular inter-actions present in the crystal and indicate that the most important contributions for the crystal packing are from H⋯O/O⋯H (41.8%), H⋯H (35.3%) and H⋯C/C⋯H (10.2%) inter-actions.

Crystal structure and Hirshfeld surface analysis of (E)-N-[(2-eth-oxy-naphthalen-1-yl)methyl-idene]-5,6,7,8-tetra-hydro-naphthalen-1-amine

In the title Schiff base compound, C23H23NO, the two ring systems are twisted by 51.40 (11)° relative to each other. In the crystal, the mol-ecules are connected by weak C-H⋯π inter-actions, generating a three-dimensional supra-molecular structure. Hirshfeld surface analysis and two-dimensional fingerprint plots indicate that the most important contributions to the crystal packing are from H⋯H (67.2%), C⋯H/H⋯C (26.7%) and C⋯C (2.5%) inter-actions.

Structural characterization and DFT study of bis-{(S)-2-[(2-hy-droxy-benz-yl)amino]-3-(4-hy-droxy-phen-yl)propano-ato-κ2N,O}(1,10-phenanthroline-κ2N,N')cadmium(II) tetra-hydrate

In the title compound, [Cd(C16H16O3)2(C12H8N2)]·4H2O, the Cd ion lies on a twofold rotation axis and is chelated by two monodeprotonated residues of the l-tyrosine-derived ligand (S)-2-[(2-hy-droxy-benz-yl)amino]-3-(4-hy-droxy-phen-yl)propanoic acid (L) in a κ2N,O amino acid chelating mode, exhibiting an (N,N')-trans disposition, and by 1,10-phenanthroline in a κ2N,N' mode. The latter ligand is also located about the twofold rotation axis that bisects the central six-members ring. The phenolic groups remain protonated and non-coordinating and take part as acceptors in the intra-molecular hydrogen bonds with the amino groups of the acido ligands. The Cd ion is six-coordinated in a distorted octa-hedral environment. In the crystal, O-H⋯O hydrogen bonds result in the formation of three-dimensional network structures. The title complex has also been characterized by IR and 1H NMR spectroscopy and DFT studies. The crystal studied was refined as an inversion twin.

Synthesis, crystal structure and Hirshfeld surface analysis of a 1D coordination polymer catena-poly[[di-aqua-bis-(nicotinamide-κN1)nickel(II)]-μ-fumarato-κ2O1:O4]

The reaction of NiCl2 with fumaric acid and nicotinamide in basic solution produces the title polymeric complex, [Ni(C4H2O4)(C6H6N2O)2(H2O)2] n . The NiII cation, located on an inversion centre, is coordinated by two O atoms of the fumarate dianions, two N atoms from nicotinamide ligands and two water mol-ecules in a distorted octa-hedral fashion. In the crystal, the fumarate dianions bridge the NiII cations, forming polymeric chains propagating along the [101] direction; the polymeric chains are further linked by O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds, forming a three-dimensional supra-molecular architecture. Hirshfeld surface analyses and two-dimensional fingerprint plots were used to analyse the inter-molecular inter-actions present in the crystal, indicating that the most important contributions for the crystal packing are from H⋯O/O⋯H (35.9%), H⋯H (31.7%) and C⋯C (10.4%) inter-actions.

Crystal structure and Hirshfeld surface analysis of N,N'-bis-(3-tert-butyl-2-hy-droxy-5-methyl-benzyl-idene)ethane-1,2-di-amine

The title compound, C26H36N2O2, crystallizes in the phenol-imine form. In the mol-ecule, there are intra-molecular O-H⋯N hydrogen bonds forming S(6) ring motifs, and the two aromatic rings are inclined to each other by 37.9 (7)°. In the crystal, mol-ecules are linked by pairs of weak C-H⋯O hydrogen bonds, forming inversion dimers. Hirshfeld surface analysis and two-dimensional fingerprint plots indicate that the most important contributions to the crystal packing are from H⋯H (77.5%), H⋯C/C⋯H (16%), H⋯O/O⋯H (3.1%) and H⋯N/N⋯H (1.7%) inter-actions.

Anion coordination directed synthesis patterns for [Ni4] aggregates: structural changes for thiocyanate coordination and ligand arm hydrolysis

Competitive bridging modes of HO⁻ and NCS⁻ were explored for four Ni^II-based coordination aggregates in cubane and dicubane topology.

Crystal structure of N-hy-droxy-quinoline-2-carboxamide monohydrate

The title compound, C10H8N2O2·H2O, consists of an N-hy-droxy-quinoline-2-carboxamide mol-ecule in the keto tautomeric form and a water mol-ecule connected through an O-H⋯O hydrogen bond. The N-hy-droxy-quinoline-2-carboxamide mol-ecule has a nearly planar structure [maximum deviation = 0.062 (1) Å] and only the hy-droxy H atom deviates significantly from the mol-ecule plane. In the crystal, π-π stacking between the aromatic rings [inter-centroid distance = 3.887 (1) Å] and inter-molecular O-H⋯O hydrogen bonds organize the crystal components into columns extending along the b-axis direction.

Crystal structure of (2,2'-bi-pyridine-κ2N,N')bis-(3,5-di-tert-butyl-o-benzo-quinonato-κ2O,O')ruthenium(II)

In the title mononuclear complex, [Ru(C14H20O2)2(C10H8N2)], the RuII ion has a distorted octa-hedral coordination environment defined by two N atoms of the chelating 2,2'-bi-pyridine ligand and four O atoms from two 3,5-di-tert-butyl-o-benzo-quinone ligands. In the crystal, the complex mol-ecules are linked by inter-molecular C-H⋯O hydrogen bonds and π-π stacking inter-actions between the 2,2'-bi-pyridine ligands [centroid-centroid distance = 3.538 (3) Å], resulting in a layer structure extending parallel to the ab plane.

Valence directed binding mode of [2 × 2] iron grids of an unsymmetrical picolinic hydrazone based ligand

Valence directed binding mode of the unsymmetrical ditopic ligand was observed in tetranuclear trivalent (FeIII4) and mixed valent (FeII2FeIII2) [2 × 2] iron grid complexes.

Crystal structure of bis-(μ-N-hy-droxy-picolin-amid-ato)bis-[bis-(N-hy-droxy-picolinamide)-sodium]

The title compound, [Na2(C6H5N2O2)2(C6H6N2O2)4], is a centrosymmetric coordination dimer based on the sodium(I) salt of N-hy-droxy-picolinamide. The mol-ecule has an {Na2O6(μ-O)2} core with two bridging carbonyl O atoms and two hydroxamate O atoms of two mono-deprotonated residues of N-hy-droxy-picolinamide, while two neutral N-hy-droxy-picolinamide mol-ecules are coordinated in a monodentate manner to each sodium ion via the carbonyl O atoms [the Na-O distances range from 2.3044 (2) to 2.3716 (2) Å]. The penta-coordinated sodium ion exhibits a distorted trigonal-pyramidal coordination polyhedron. In the crystal, the coordination dimers are linked into chains along the c axis via N-H⋯O and N-H⋯N hydrogen bonds; the chains are linked into a two-dimensional framework parallel to (100) via weak C-H⋯O and π-π stacking inter-actions.

Crystal structure of poly[di-aqua-(μ-2-carb-oxy-acetato-κ(3) O,O':O'')(2-carb-oxy-acetato-κO)di-μ-chlorido-dicobalt(II)]

In the title coordination polymer, [Co(C₃H₃O₄)Cl(H₂O)]_n, the sixfold coordination environment of the Co^II atom consists of two O atoms from a chelating hydrogen malonate anion (HMal⁻), one O atom originating from a μ₂-bridging malonate ligand (HMal⁻), one O atom from a water mol­ecule and two μ₂-bridging Cl⁻ atoms, connecting neighbouring Co₂Cl₄ motifs into a two-dimensional polymer extending parallel to (001). Inter­layer O—H⋯O hydrogen bonds link the layers into a three-dimensional network.

The asymmetric unit of the title polymer, [Co₂(C₃H₃O₄)₂Cl₂(H₂O)₂]_n, comprises one Co^II atom, one water mol­ecule, one singly deprotonated malonic acid mol­ecule (HMal⁻; systematic name 2-carb­oxy­acetate) and one Cl⁻ anion. The Co^II atom is octa­hedrally coordinated by the O atom of a water mol­ecule, by one terminally bound carboxyl­ate O atom of an HMal⁻ anion and by two O atoms of a chelating HMal⁻ anion, as well as by two Cl⁻ anions. The Cl⁻ anions bridge two Co^II atoms, forming a centrosymmetric Co₂Cl₂ core. Each malonate ligand is involved in the formation of six-membered chelate rings involving one Co^II atom of the dinuclear unit and at the same time is coordinating to another Co^II atom of a neighbouring dinuclear unit in a bridging mode. The combination of chelating and bridging coordination modes leads to the formation of a two-dimensional coordination polymer extending parallel to (001). Within a layer, O—H_water⋯Cl and O—H_water⋯O hydrogen bonds are present. Adjacent layers are linked through O—H⋯O=C hydrogen bonds involving the carb­oxy­lic acid OH and carbonyl groups.

A carboxylate-bridged NiII8 cluster with a distorted cubane topology: structure, magnetism and density functional studies

An octanickel(ii) cluster supported solely by carboxylate-bridges has been achieved by a (2-pyridyl)ethylamine-appended dicarboxylate ligand. A study of magnetostructural analysis has been carried out and substantiated by theoretical calculations.

Crystal structure of 2-{[(E)-(4-anilinophen-yl)iminium-yl]meth-yl}-5-(di-ethyl-amino)-phenolate

The title compound, C₂₃H₂₅N₃O, crystallized with one single mol­ecule in the asymmetric unit and present in the zwitterionic form. In the crystal, mol­ecules are connected by N—H⋯O hydrogen bonds generating –A–B–A–B– zigzag chains extending along [010]. The chains are linked via C—H⋯π inter­actions and π–π inter­actions [with a centroid–centroid distance of 3.444 (3) Å)] between the benzene ring and the imino group of symmetry-related mol­ecules, forming slabs lying parallel to (100).

The title compound, C₂₃H₂₅N₃O, crystallized with one single mol­ecule in the asymmetric unit and is present in the zwitterionic form. There is an intra­molecular N—H⋯O hydrogen bond in the mol­ecule with the phenol ring being inclined to the central benzene ring by 20.67 (14)°. The terminal amino­phenyl ring forms a dihedral angle of 54.21 (14)° with the central benzene ring. The two outer aromatic rings are inclined to one another by 74.54 (14)°. In the crystal, the mol­ecules are connected by N—H⋯O hydrogen bonds, with adjacent molecules related by a 2₁ screw axis, generating –A–B–A–B– zigzag chains extending along [010]. The chains are linked via C—H⋯π and π–π inter­actions [with a centroid–centroid distance of 3.444 (3) Å] between the benzene ring and the imino group of symmetry-related mol­ecules, forming slabs lying parallel to (100).

Crystal structure of 2-amino-1,3-di-bromo-6-oxo-5,6-di-hydro-pyrido[1,2-a]quinoxalin-11-ium bromide monohydrate

In the title hydrated salt, C12H8Br2N3O(+)·Br(-)·H2O, which was synthesized by the reaction of the pyridine derivative Schiff base N (1),N (4)-bis-(pyridine-2-yl-methyl-ene)benzene-1,4-di-amine with bromine, the asymmetric unit contains a 2-amino-1,3-di-bromo-6-oxo-5,6-di-hydro-pyrido[1,2-a]quinoxalin-11-ium cation, with a protonated pyridine moiety, a bromide anion and a water mol-ecule of solvation. The cation is non-planar with the di-bromo-substituted benzene ring, forming dihedral angles of 24.3 (4) and 11.5 (4)° with the fused pyridine and pyrazine ring moieties, respectively. In the crystal, the cations are linked through a centrosymmetric hydrogen-bonded cyclic R 4 (2)(8) Br2(H2O)2 unit by N-H⋯Br, N-H⋯O and O-H⋯Br hydrogen bonds, forming one-dimensional ribbons extending along b, with the planes of the cations lying parallel to (100).

Crystal structure of N (1)-phenyl-N (4)-[(E)-(pyren-1-yl)methyl-idene]benzene-1,4-di-amine

In the title compound, C29H20N2, the dihedral angles subtended by the central p-phenyl-enedi-amine ring with respect to the mean plane of the terminal pyrenyl ring system (r.m.s. deviation = 0.027 Å) and the terminal N-phenyl ring are 29.34 (4) and 43.43 (7)°, respectively. The conformation about the C=N bond is E. In the crystal, mol-ecules are linked by N-H⋯π and C-H⋯π inter-actions forming chains propagating along the [10-2] direction. These chains are linked via π-π inter-actions [inter-centroid distances are in the range 3.5569 (11)-3.708 (1) Å], forming slabs lying parallel to (30-4).

Crystal structure of di-chlorido-{N (1)-phenyl-N (4)-[(quinolin-2-yl-κN)methylidene]benzene-1,4-diamine-κN (4)}mercury(II)

In the mononuclear title complex, [HgCl2(C22H17N3)], synthesized from the quinoline-derived Schiff base N (1)-phenyl-N (4)-[(quinolin-2-yl)methyl-idene]benzene-1,4-di-amine (PQMBD) and HgCl2, the coordination sphere around the Hg(2+) atom is distorted tetra-hedral, comprising two Cl atoms [Hg-Cl = 2.3487 (14) and 2.4490 (15) Å] and two N atom donors from the PQMBD ligand, viz. the quinolyl and the imine N atom [Hg-N = 2.270 (4) and 2.346 (4) Å, respectively]. The dihedral angle between the two benzene rings attached to the amino group is 43.7 (3)°. In the crystal, N-H⋯Cl and C-H⋯Cl hydrogen bonds, as well as π-π stacking inter-actions between one phenyl ring and the pyridine ring of the quinoline moiety of an adjacent mol-ecule [centroid-to-centroid separation = 3.617 (4) Å] are observed, resulting in a three-dimensional network.

Crystal structure of di-bromido-(N,N-di-methyl-formamide-κO){2-(1H-indol-3-yl)-N-[(quinolin-2-yl-κN)methyl-idene]ethanamine-κN}cadmium

In the mononuclear title complex, [CdBr2(C20H17N3)(C3H7NO)], synthesized from the quinoline-derived Schiff base 2-(1H-indol-3-yl)-N-(quinolin-2-yl-methyl-ene)ethan-amine (IQME), the coordination geometry around the Cd(2+) atom is distorted trigonal bipyramidal, the axial positions being occupied by the quinoline N atom [Cd-N = 2.401 (3) Å] and one di-methyl-formamide O-atom donor [Cd-O = 2.399 (2) Å]. The equatorial plane is formed by the imine N atom [Cd-N = 2.293 (3) Å] and two bromides [Cd-Br = 2.5621 (8) and 2.5676 (8) Å], with the deviation of the Cd(II) atom from the equatorial plane being 0.046 (1) Å. An intra-molecular C-H⋯Br inter-action occurs. In the crystal, N-H⋯Br inter-actions generate [101] chains.

Crystal structure of aqua[N-(2-oxidobenzyl-κO)-l-leucinato-κ(2) N,O](1,10-phenanthroline-κ(2) N,N')-nickel(II) penta-hydrate

In the title compound, [Ni(C13H17NO3)(C12H8N2)(H2O)]·5H2O, the Ni(II) atom is in a distorted octa-hedral coordination environment provided by the two N atoms of one bidentate phenanthroline ligand and two O atoms and one N atom from a tridentate 2-[(2-hy-droxy-benz-yl)amino]-4-methyl-penta-noic acid (HAMA) ligand and one water mol-ecule. The complex was prepared by the reaction of nickel(II) nitrate with HAMA in the presence of 1,10-phenanthroline in a 1:1:1 ratio. In the crystal, the complex mol-ecules and solvate water mol-ecules are associated via O-H⋯O hydrogen bonds into a three-dimensional network.

Crystal structure of 2-azaniumyl-3-bromo-6-oxo-5,6-dihydropyrido[1,2-a]quinoxalin-11-ium dibromide

The title salt, C₁₂H₁₀BrN₃O²⁺·2Br⁻, was synthesized from the reaction of N¹,N⁴-bis­(pyridin-2-yl­methyl­idene)benzene-1,4-di­amine and bromine in a methanol solution. All non-H atoms of the 2-aza­niumyl-3-bromo-6-oxo-5,6-di­hydro­pyrido[1,2-a]quinoxalin-11-ium cation are nearly coplanar, the maximum deviation being 0.114 (4) Å. In the crystal, the cations and anions are linked through N—H⋯Br hydrogen bonds and weak C—H⋯Br inter­actions, forming a three-dimensional supra­molecular architecture. A short Br⋯Br contact [3.3088 (9) Å] is observed in the crystal.

Crystal structure of (E)-2-{[(4-anilinophen-yl)imino]-meth-yl}phenol

The title compound crystallized with two independent mol­ecules (A and B) in the asymmetric unit, which differ essentially in the orientation of the terminal amino­phenyl ring with respect to the central benzene ring. In the crystal, mol­ecules are linked via N—H⋯O hydrogen bonds forming –A-B–A–B– zigzag chains propagating along [010].

The title compound, C₁₉H₁₆N₂O, crystallized with two independent mol­ecules (A and B) in the asymmetric unit. There is an intra­molecular O—H⋯N hydrogen bond in each mol­ecule with the phenol ring being inclined to the central benzene ring by 4.93 (14) and 7.12 (14)° in mol­ecules A and B, respectively. The conformation of the two mol­ecules differs essentially in the orientation of the terminal amino­phenyl ring with respect to the central benzene ring; this dihedral angle is 50.51 (4)° in mol­ecule A and 54.61 (14)° in mol­ecule B. The two outer aromatic rings are inclined to one another by 51.39 (14) and 49.88 (14)° in mol­ecules A and B, respectively. In the crystal, mol­ecules are connected by N—H⋯O hydrogen bonds generating –A-B–A–B– zigzag chains extending along [010]. The chains are linked via C—H⋯π inter­actions involving neighbouring A mol­ecules, forming slabs lying parallel to (100).

Crystal structure of meso-tetra-kis-(4-nitro-phen-yl)porphyrin nitro-benzene disolvate

The porphyrin core of the title centrosymmetric compound, C₄₄H₂₆N₈O₈·2C₆H₅NO₂, is approximately planar, the maximum deviation being 0.069 (3) Å. The planes of the benzene rings of the nitro­phenyl substituents are almost perpendicular to the porphyrin mean plane, making dihedral angles of 73.89 (9) and 89.24 (9)°. The two pyrrole ring H atoms are equally disordered over the four pyrrole ring N atoms. In the crystal, weak C—H⋯O and C—H⋯N hydrogen bonds link the porphyrin mol­ecules into a three-dimensional supra­molecular network. The nitro­benzene solvent mol­ecules are linked by weak C—H⋯O hydrogen bonds into supra­molecular chains propagating along the a-axis direction.

2-[(Pyridin-2-yl)amino]pyridinium 2,4,6-trinitrophenolate

In the cation of the title salt, C₁₀H₁₀N₃⁺·C₆H₂N₃O₇⁻, the pyridine and pyridinium rings are linked by an intra­molecular N—H⋯N hydrogen bond and are approximately coplanar, with a dihedral angle between their planes of 4.24 (6)°. In the crystal, the cations and anions are linked through N—H⋯O hydrogen bonds, forming supra­molecular chains propagating along the c-axis direction. π–π stacking is observed between neighbouring chains, the centroid–centroid distances being 3.7638 (11) (between pyridinium rings) and 3.5331 (11) Å (between benzene rings).

Tetra-kis[bis-(pyridin-2-yl)amine-κN (2)](nitrato-κO)silver(I)

In the title complex, [Ag(NO₃)(C₁₀H₉N₃)₄], the nitrate ligand is found to be disordered over two sets of positions, with occupancy factors of 0.473 (5) and 0.527 (5). The Ag^I ion is located in a square-pyramidal coordination environment formed by four N atoms from four bis­(pyridin-2-yl)amine ligands and one O atom from a nitrate ligand. Weak inter­actions between the Ag^I ions and the nitrate anions acting in a monodentate mode [Ag⋯O = 2.791 (13) and 2.816 (9) Å for the major component of the nitrate ligand, and 2.865 (8) and 2.837 (8) Å for the minor component] link the complex mol­ecules into a chain along [001]. N—H⋯O hydrogen bonds are observed.

Hydrazone-based switches, metallo-assemblies and sensors

The hydrazone functional group has been extensively studied and used in the context of supramolecular chemistry. Its pervasiveness and versatility can be attributed to its ease of synthesis, modularity, and most importantly unique structural properties, which enable its integration in different applications. This review provides an overview of the utilization of hydrazones in three supramolecular chemistry related areas: molecular switches, metallo-assemblies and sensors. These topics were chosen because they highlight the diversity of hydrazones, and emphasize their uniqueness vis-à-vis the imine functional group. Discussion entails (i) chemical and light activated switching of hydrazones, and how this can be used in controlling the properties of self-assembled systems, (ii) the use of hydrazones in the formation of dynamic and stimuli responsive metallogrids, and (iii) the use of hydrazones in detecting metal cations (Zn(2+), Cu(2+), Hg(2+), etc.), anions (F(-), CN(-), P2O7(4-), etc.) and neutral molecules (amines, water, Cys, etc.).

Cu(i) and Ag(i) complexes of 7,10-bis-N-heterocycle-diazafluoranthenes: programmed molecular grids?

Reactions of 7,10-disubstituted diazafluoranthene derivatives with three different silver(i) salts AgX (X = [PF₆]⁻, [SbF₆]⁻, [CB₁₁HCl₁₁]⁻) and [Cu(CH₃CN)₄]PF₆ afforded complexes exhibiting five different motifs.

(2,2'-Bi-pyridine-κ(2) N,N')tetra-kis-(dimethyl sulfoxide-κO)copper(II) bis-(perchlorate)

The title compound, [Cu(C₂H₆OS)₄(C₁₀H₈N₂)](ClO₄)₂, contains a Cu^II ion with a distorted octa­hedral coordination environment, bonded by four O atoms of the monodentate dimethyl sulfoxide ligands and two N atoms of the bidentate chelating 2,2′-bi­pyridine ligand. The equatorial Cu—N and Cu—O bond lengths are in the range 1.979 (2)-1.998 (3) Å. The axial Cu—O bond distances are 2.365 (2) and 2.394 (2) Å. In the crystal, the complex cations and perchlorate anions are connected by numerous C—H⋯O hydrogen bonds, which leads to additional stabilization of the structure. The perchlorate anion is disordered over two sets of sites with a 0.716 (3):0.284 (3) occupancy ratio.

Bis(2,2'-bipyridyl-κ(2) N,N')(sulfato-κ(2) O,O')nickel(II) 2.5-hydrate

The title compound, [Ni(SO₄)(C₁₀H₈N₂)₂]·2.5H₂O, is a nickel(II) complex with a distorted octa­hedral coordination geometry. The Ni^II atom is bonded by two O atoms of the bidentate chelating sulfate ligand and the four N atoms of two chelating 2,2′-bi­pyridine ligands. The Ni—N bond lengths range from 2.059 (3) to 2.075 (3) Å and the Ni—O bond lengths are 2.098 (3) and 2.123 (3) Å. The bipyridyl ligands are both close to planar (r.m.s. deviations of 0.254 and 0.0572 Å) and are almost orthogonal, making a dihedral angle of 82.77 (1)°. In the crystal, the complex and water mol­ecules are connected by O—H⋯O hydrogen bonds. Inter­estingly, six water mol­ecules form a chain linking two complex mol­ecules via sulfate O atoms. There are also stacking inter­actions between the aromatic rings of neighbouring 2,2′-bi­pyridine ligands with shortest non-covalent contacts of 3.268 (6), 3.393 (6) and 3.435 (5) Å. One of the three unique water molecules shows half-occupation.

A second monoclinic polymorph of 2-(3,5-dimethyl-1H-pyrazol-1-yl)-2-hy-droxy-imino-N'-[1-(pyridin-2-yl)ethyl-idene]acetohydrazide

The title compound, C14H16N6O2, is a second monoclinic polymorph of 2-[1-(3,5-dimeth-yl)pyrazol-yl]-2-hy-droxy-imino-N'-[1-(2-pyrid-yl)ethyl-idene] acetohydrazide, with two crystallographically independent mol-ecules per asymmetric unit. The non-planar mol-ecules are chemically equal having similar geometric parameters. The previously reported polymorph [Plutenko et al. (2012 ▶). Acta Cryst. E68, o3281] was described in space group Cc (Z = 4). The oxime group and the O atom of the amide group are anti with respect to the C-C bond. In the crystal, mol-ecules are connected by N-H⋯N hydrogen bonds into zigzag chains extending along the b axis.