Charge‐transfer complexes of 4‐(di­methyl­amino)­pyridine with 2,4‐, 3,4‐ and 3,5‐di­nitro­benzoic acid

In the three title crystal structures 4‐(di­methyl­amino)­pyridinium 2,4‐di­nitro­benzoate, (I), 4‐(di­methyl­amino)­pyri­dinium 3,4‐di­nitro­benzo­ate, (II), and 4‐(di­methyl­amino)pyri­din­ium 3,5‐di­nitro­benzo­ate, (III), all C₇H₁₁N₂⁺·C₇H₃N₂O₆^?, the ions are connected by an N—H?O hydrogen bond. Dihedral angles between the pyridine and phenyl rings are 69.9 (1), 26.7 (1) and 56.2 (1)° in (I), (II) and (III), respectively. Donor–acceptor π–π stacking is observed in (II) and (III), but not in (I).     

Charge‐transfer complexes of N‐methyl‐and N‐ethyl­carbazole with 3,5‐di­nitro­benzo­nitrile

In the two title compounds, N‐methyl­carba­zole–3,5‐di­nitro­benzo­nitrile (1/1), C₁₃H₁₁N·C₇H₃N₃O₄, (I), and N‐ethyl­carba­zole–3,5‐di­nitro­benzo­nitrile (1/1), C₁₄H₁₃N·C₇H₃N₃O₄, (II), the donor and acceptor mol­ecules are stacked alternately to form one‐dimensional columns. In (I), the N‐methyl group of the donor is nearly eclipsed with respect to one of the nitro groups of the neighboring acceptor in a column, whereas the N‐ethyl group is anti with respect to the cyano group of the neighboring acceptor in (II).     

2,4‐Di­nitro­phenyl­hydrazones of 2,4‐di­hydroxy­benz­aldehyde, 2,4‐di­hydroxy­aceto­phenone and 2,4‐di­hydroxy­benzo­phenone

In 2,4‐di­hydroxy­benz­aldehyde 2,4‐di­nitro­phenyl­hydrazone N,N‐di­methyl­form­amide solvate {or 4‐[(2,4‐di­nitro­phenyl)­hydrazono­methyl]­benzene‐1,3‐diol N,N‐di­methyl­form­amide solvate}, C₁₃H₁₀N₄O₆·C₃H₇NO, (X), 2,4‐di­hydroxy­aceto­phenone 2,4‐di­nitro­phenyl­hydrazone N,N‐di­methyl­form­am­ide solvate (or 4‐{1‐[(2,4‐di­nitro­phenyl)hydrazono]ethyl}benzene‐1,3‐diol N,N‐di­methyl­form­amide solvate), C₁₄H₁₂N₄O₆·C₃H₇NO, (XI), and 2,4‐di­hydroxy­benzo­phenone 2,4‐di­nitro­phenyl­hydrazone N,N‐di­methyl­acet­amide solvate (or 4‐­{[(2,4‐di­nitro­phenyl)hydrazono]phenyl­methyl}benzene‐1,3‐diol N,N‐di­methyl­acet­amide solvate), C₁₉H₁₄N₄O₆·C₄H₉NO, (XII), the molecules all lack a center of symmetry, crystallize in centrosymmetric space groups and have been observed to exhibit non‐linear optical activity. In each case, the hydrazone skeleton is fairly planar, facilitated by the presence of two intramolecular hydrogen bonds and some partial N—N double‐bond character. Each molecule is hydrogen bonded to one solvent mol­ecule.     

2‐Amino derivatives of 5‐nitro­phenyl­acet­amide

The structures of the potential non‐linear optical (NLO) materials N‐[2‐(iso­propyl­amino)‐5‐nitro­phenyl]­acet­amide, (I) C₁₁H₁₅N₃O₃, and N‐[2‐(butyl­amino)‐5‐nitro­phenyl]­acet­amide, (II) C₁₂H₁₇N₃O₃, have been investigated by X‐ray analysis. To compare them with the structure of N‐[2‐(di­methyl­amino)‐5‐nitro­phenyl]­acet­amide, (III) C₁₀H₁₃N₃O₃, a known NLO compound, we had to redetermine the structure of (III), since it was described only briefly in the literature. There are two mol­ecules in the asymmetric unit of compound (I), which have different orientations of the substituents with respect to the benzene ring. The packing of mol­ecules in (II) and (III) contains stacks but both (I) and (II) crystallize in a centrosymmetric space group, which renders them inappropriate for NLO applications.     

Hydro­gen bonding in substituted nitro­anilines: isolated nets in 1,3‐­diamino‐4‐nitrobenzene and continuously interwoven nets in 3,5‐­dinitro­aniline

Molecules of 1,3‐diamino‐4‐nitrobenzene, C₆H₇N₃O₂, are linked by N—H?O hydrogen bonds [N?O 2.964 (2) and 3.021 (2) Å; N—H?O 155 and 149°] into (4,4) nets. In 3,5‐di­nitro­aniline, C₆H₅N₃O₄, where Z′ = 2, the mol­ecules are linked by three N—H?O hydrogen bonds [N?O 3.344 (2)–3.433 (2) Å and N—H?O 150–167°] into deeply puckered nets, each of which is interwoven with its two immediate neighbours.     

The ternary complex 4‐(2‐pyridyl)pyridinium–3,5‐di­nitro­benzoate–3,5‐di­nitro­benzoic acid (1/1/1)

In the title ternary complex, C₁₀H₉N₂⁺·C₇H₃N₂O₆^?·C₇H₄N₂O₆, the pyridinium cation adopts the role of the donor in an intermolecular N—H?O hydrogen‐bonding interaction with the carboxyl­ate group of the 3,5‐di­nitro­benzoate anion. The mol­ecules of the ternary complex form molecular ribbons perpendicular to the b direction, which are stabilized by one N—H?O, one O—H?O and five C—H?O intermolecular hydrogen bonds. The ribbons are further interconnected by three intermolecular C—H?O hydrogen bonds into a three‐dimensional network.     

Di­aqua­bis­(di­methyl sulfoxide)­bis(3,5‐di­nitro­benzoato)­zinc(II) and the synthesis of the Cu,Ni and Co analogs

In order to model processes of chemisorption in organic salts formed between di­nitro­benzoic acids (DNBH) and secondary amines (R₂NH), a series of compounds of composition [M^II(3,5‐DNB)₂(DMSO)₂(H₂O)₂] (where M^II is Zn, Cu, Ni or Co, 3,5‐DNB is the 3,5‐di­nitro­benzoate ion, and DMSO is di­methyl sulfoxide) have been prepared. In di­aqua­bis­(di­methyl sulf­oxide)­bis(3,5‐DNB)­zinc(II), [Zn(C₇H₃N₂O₆)₂(C₂H₆OS)₂(H₂O)₂], the 3,5‐DNB ions and mol­ecules of DMSO are monodentate ligands that are coordinated to the Zn atom through their O atoms. These ligands, together with two mol­ecules of water, form a slightly distorted octahedral coordination environment for the Zn atom, which lies on a center of symmetry.     

A host–guest complex of di­aqua­bis­[1‐hydroxy‐2(1H)‐pyridine­thionato‐O,S]­magnesium(II) and 2,2′‐di­thio­bis­(pyridine N‐oxide)

The title compound, [Mg(C₅H₄NOS)₂(H₂O)₂]·C₁₀H₈N₂O₂S₂, is a two‐component host–guest material. The 2,2′‐di­thio­bis(pyridine N‐oxide) molecule has crystallographic twofold symmetry. The metal complex lies on an inversion centre and associates via C—H?S interactions into chains which thread the 2,2′‐di­thio­bis­(pyridine N‐oxide) lattice in perpendicular directions. Hydro­gen bonds exist between the water mol­ecules of the di­aqua­magnesium units and the N—O groups of the host lattice.     

Hydrogen bonding in nitroaniline analogues: hydrogen‐bonded sheets in 2‐amino‐4,6‐dimethoxy‐5‐nitropyrimidine and π‐stacked hydrogen‐bonded sheets in 4‐amino‐2,6‐dimethoxy‐5‐nitropyrimidine

In 2‐amino‐4,6‐di­methoxy‐5‐nitro­pyrimidine, C₆H₈N₄O₄, the mol­ecules are linked by one N—H⋯N and one N—H⋯O hydrogen bond to form sheets built from alternating R(8) and R(32) rings. In isomeric 4‐amino‐2,6‐di­methoxy‐5‐nitro­pyrimidine, C₆H₈N₄O₄, which crystallizes with Z′ = 2 in P, the two independent mol­ecules are linked into a dimer by two independent N—H⋯N hydrogen bonds. These dimers are linked into sheets by a combination of two‐centre C—H⋯O and three‐centre C—H⋯(O)₂ hydrogen bonds, and the sheets are further linked by two independent aromatic π–π‐stacking interactions to form a three‐dimensional structure.     

The proton‐transfer compounds of strychnine with achiral salicylic acids: strychninium 3,5‐dinitro­salicylate and the strychninium 5‐nitro­salicylate bis­(5‐nitro­salicylic acid) adduct

In the crystal structures of the proton‐transfer compounds of strychnine with 3,5‐dinitro­salicylic acid, namely strychninium 3,5‐dinitro­salicylate, C₂₁H₂₃N₂O₂⁺·C₇H₃N₂O₇⁻, (I), and 5‐nitro­salicylic acid, namely strychninium–5‐nitro­salicylate–5‐nitro­salicylic acid (1/1/2), C₂₁H₂₃N₂O₂⁺·C₇H₄NO₅⁻·2C₇H₅NO₅, (II), protonation of one of the N atoms of the strychnine mol­ecule occurs and this group is subsequently involved in inter­molecular hydrogen‐bonding inter­actions. In (I), this is four‐centred, the primary being with an adjacent strychninium carbonyl O‐atom acceptor in a side‐to‐side inter­action giving linear chains. Other inter­actions are with the phenolate and nitro O‐atom acceptors of the anionic species, resulting in a one‐dimensional polymer structure. In (II), the N⁺—H inter­action is three‐centred, the hydrogen bonding involving carboxyl O‐atom acceptors of the anion and both acid adduct species, giving unique discrete hetero‐tetramer units. The structure of (II) also features π‐bonding inter­actions between the two acid adduct mol­ecules.     

N,N‐Diethyl‐2,6,6‐trimethyl‐4‐(3‐nitrophenyl)‐5‐oxo‐1,4,5,6,7,8‐hexahydroquinoline‐3‐carboxamide

The title compound, C₂₃H₂₉N₃O₄, has potential calcium modulatory properties. The conformation of the 1,4‐di­hydro­pyridine ring is unusual in that it is planar, instead of the usual shallow boat. The 3‐nitro­phenyl substituent is in the synperiplanar orientation with respect to the di­hydro­pyridine ring plane. The oxo­cyclo­hexene ring has a distorted envelope conformation, with the out‐of‐plane atom being disordered on opposite sides of the ring plane. The mol­ecules are linked into chains by intermolecular hydrogen bonds.     

2,3‐Bis(4‐nitro­benzyl­thio)­maleo­nitrile

The maleo­nitrile moiety of the title compound, (2Z)‐2,3‐bis­[(4‐nitro­benzyl)­sulfanyl]­but‐2‐ene­di­nitrile, C₁₈H₁₂N₄O₄S₂, is almost planar. The two benzene rings are nearly parallel to each other and perpendicular to the maleo­nitrile plane. Intermolecular S?S and π–π interactions are observed in the crystal structure.     

3‐Methyl 5‐isopropyl 2‐methoxy­imino­methyl‐6‐methyl‐4‐(3‐nitro­phenyl)‐1,4‐di­hydro­pyridine‐3,5‐di­carboxyl­ate

The crystal structure of the title compound, C₂₀H₂₃N₃O₇, consists of relatively isolated mol­ecules. The substituted 1,4‐di­hydro­pyridine ring adopts a flattened boat conformation. Both ester groups, at positions 3 and 5, have cis,cis geometry. The phenyl ring is nearly planar and is approximately perpendicular to the 1,4‐di­hydro­pyridine ring (dihedral angle 87.70°).     

trans‐Bis­[1‐methyl‐3‐(p‐nitro­phenyl)­triazenido 1‐oxide‐κ2N3,O]­di­pyridine­nickel(II)

In the centrosymmetric title complex, [Ni(C₇H₇N₄O₃)₂(C₅H₅N)₂], the coordination geometry about the Ni²⁺ ion is octahedral, with two deprotonated 1‐methyl‐3‐(p‐nitro­phenyl)­triazenide 1‐oxide ions, viz. [O₂N­C₆H₄­NNN(O)­CH₃]^?, acting as bidentate ligands (four‐electron donors). Two neutral pyridine (py) mol­ecules complete the coordination sphere in positions trans to each other. The triazenide 1‐oxide ligand is almost planar, the largest interplanar angle of 8.80 (12)° being between the phenyl ring of the p‐nitro­phenyl group and the plane defined by the N₃O moiety. The Ni—N_triazenide, Ni—O and Ni—N_py distances are 2.0794 (16), 2.0427 (13) and 2.1652 (18) Å, respectively.     

Tetrakis(3,5‐di­methyl­pyridine)­dihydrido­silicon dibromide bis(aceto­nitrile) solvate and 3,5‐dimethylpyridinium bromide

In the course of an attempt to synthesize tetrakis(3,5‐di­methyl­pyridine)­dihydridosilicon dibromide, crystals of its aceto­nitrile disolvate, C₂₈H₃₈N₄Si²⁺·2Br^?·2C₂H₃N, (I), and of 3,5‐di­methyl­pyridinium bromide, C₇H₁₀N⁺·Br^?, (II), were obtained in the same reaction flask. They have both been structurally characterized.     

N‐Meth­yl‐N‐(2‐nitro­phen­yl)nitramine and N‐meth­yl‐N‐(3‐nitro­phen­yl)­nitramine

The structures of the two title isomeric compounds (systematic names: N‐meth­yl‐N,2‐dinitro­aniline and N‐meth­yl‐N,3‐di­nitro­aniline, both C₇H₇N₃O₄) are slightly different because they exhibit different steric hindrances and hydrogen‐bonding environments. The aromatic rings are planar. The –N(Me)NO₂ and –NO₂ groups are not coplanar with the rings. Comparison of the geometric parameters of the ortho, meta and para isomers together with those of N‐meth­yl‐N‐phenyl­nitramine suggests that the position of the nitro group has a strong influence on the aromatic ring distortion. The crystal packing is stabilized by weak C—H⋯O hydrogen bonds to the nitramine group.     

Hydro­gen‐bonded dimers in N‐(2‐nitro­phenyl­thio)­saccharin

In the title compound, 2‐(2‐nitro­phenyl­thio)‐1,2‐benzo­thia­zol‐3(2H)‐one 1,1‐dioxide, 2‐O₂NC₆H₄S(C₇H₄NO₃S) or C₁₃H₈N₂­O₅S₂, the planes of the saccharin and nitro­phenyl­thiol­ate portions are almost orthogonal. The mol­ecules are linked by C—H?O=S hydrogen bonds [C?O 3.308 (3) Å, H?O 2.44 Å and C—H?O 155°] into cyclic centrosymmetric R²₂(16) dimers, reinforced by aromatic π?π stacking interactions between the nitrated aryl rings.     

N‐(4‐Methyl­phenyl)‐N‐(5‐nitro­furfuryl)‐N‐prop‐2‐ynyl­amine

The title compound, C₁₅H₁₄N₂O₃, is the first example of a structurally determined tertiary amine with both N‐5‐nitro­furfuryl and N‐prop‐2‐ynyl moieties. The mol­ecule is not planar, i.e. the furan ring is inclined at an angle of 84.35 (4)° to the phenyl ring. The crystal structure is dominated by van der Waals forces. The terminal alkynyl group as the strongest C—H hydrogen‐bond donor is not involved in hydrogen‐bond formation.     

Methyl 4‐(2‐chloro‐5‐nitro­phenyl)‐2,7,7‐tri­methyl‐5‐oxo‐1,4,5,6,7,8‐hexa­hydro­quinoline‐3‐carboxyl­ate

The title compound, C₂₀H₂₁ClN₂O₅, has potential calcium modulatory properties. The 1,4‐di­hydro­pyridine ring has the usual shallow boat conformation. The 2‐chloro‐5‐nitro­phenyl ring is oriented such that the chloro substituent is in a synperiplanar orientation with respect to the 1,4‐di­hydro­pyridine ring plane, while the nitro substituent sits over the 1,4‐di­hydro­pyridine ring. The cyclo­hexenone ring has a conformation that is approximately half‐way between that of an envelope and that of a half‐chair. The mol­ecules are linked into chains by intermolecular N—H⋯O hydrogen bonds.     

Two‐component molecular crystals from N‐heteroaromatics and nitro­benzoic acids

Five two‐component molecular crystals, benzimidazolium 3‐nitro­benzoate, C₇H₇N₂⁺·C₇H₄NO₄^?, (I), benzimidazolium 4‐nitro­benzoate, C₇H₇N₂⁺·C₇H₄NO₄^?, (II), 1H‐benzotriazole–3‐nitro­benzoic acid (1/1), C₆H₅N₃·C₇H₅NO₄, (III), imidazol­ium 3‐nitro­benzoate, C₃H₅N₂⁺·C₇H₄NO₄^?, (IV), and imid­azolium 4‐nitro­benzoate, C₃H₅N₂⁺·C₇H₄NO₄^?, (V), were prepared with the aim of making chiral crystals. Only (I) crystallizes in a chiral space group. The mol­ecules of (I) and (II) are linked by hydrogen bonds to form 2₁ spiral chains. In (III), (IV) and (V), macrocyclic structures are formed from two acid and two base components, by an alternate arrangement of the acid and base moieties.