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).     

Bis(3,5‐di­methyl­pyrazole‐κN2)silver(I) nitrate

The two independent bis(3,5‐di­methyl­pyrazole)silver(I) cations in crystalline [Ag(C₅H₇N₂)₂]NO₃ display N—Ag—N angles of 175.51 (14) and 174.44 (13)°, and an average Ag—N distance of 2.124 (5) Å. The nitrate anion is situated between [Ag(C₅H₇N₂)₂]⁺ units and interacts via hydrogen bonds with the NH groups. The two 3,5‐di­methyl­pyrazole ligands are trans about the silver center. Only a small deviation from linearity is observed in the coordination around silver.     

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.     

(Z)‐2‐Methylbuten‐1‐yl(aryl)iodonium trifluoromethanesulfonates containing electron‐withdrawing groups on the aryl moiety

The crystal structures of [(Z)‐2‐methyl­but‐1‐en‐1‐yl]­[4‐(tri­fluoro­methyl)­phenyl]­iodo­nium tri­fluoro­methane­sulfonate, C₁₂H₁₃F₃I⁺·CF₃O₃S^?, (I), (3,5‐di­chloro­phenyl)­[(Z)‐2‐methyl­but‐1‐en‐1‐yl]­iodo­nium tri­fluoro­methane­sulfonate, C₁₁H₁₂­Cl₂I⁺·CF₃O₃S^?, (II), and bis{[3,5‐bis­(tri­fluoro­methyl)­phenyl][(Z)‐2‐methyl­but‐1‐en‐1‐yl]­iodo­nium} bis­(tri­fluoro­methane­sulfonate) di­chloro­methane solvate, 2C₁₃H₁₂F₆I⁺·­2CF₃­O₃S^?·CH₂Cl₂, (III), are described. Neither simple acyclic β,β‐di­alkyl‐substituted alkenyl­(aryl)­idonium salts nor a series containing electron‐deficient aryl rings have been described prior to this work. Compounds (I)–(III) were found to have distorted square‐planar geometries, with each I atom interacting with two tri­fluoro­methane­sulfonate counter‐ions.     

A complex containing both five‐ and six‐coordinate [bis(5‐bromosalicyli­dene)benzene‐1,2‐diimine]chloro­iron(III)

The title compound, aqua­chloro{4,4′‐di­bromo‐2,2′‐[o‐phenylenebis­(nitrilo­methyl­idyne)]­diphenolato‐O,N,N′,O′}iron(III)–chloro{4,4′‐di­bromo‐2,2′‐[o‐phenyl­enebis­(nitrilomethyli‐dyne)]diphenolato‐O,N,N′,O′}iron(III)–di­methyl­form­amide (1/1/1), [FeCl(C₂₀H₁₂Br₂N₂O₂)][FeCl(C₂₀H₁₂Br₂N₂O₂)(H₂O)]·C₃H₇NO, contains one independent five‐coordinate [FeCl(C₂₀H₁₂Br₂N₂O₂)] monomer, one six‐coordinate [FeCl(C₂₀H₁₂Br₂N₂O₂)(H₂O)] monomer and a non‐coordinating di­methyl­form­amide solvent mol­ecule in the asymmetric unit. In the five‐coordinate monomer, the Fe atom shows distorted square‐pyramidal geometry, with the N and O atoms of the ligand at the base and the Cl atom at the apex of the pyramid. In the six‐coordinate monomer, the Fe atom is in a distorted octahedral geometry and coordinated by the donor atoms of the tetrafunctional ligand in the horizontal plane, and the coordination sphere is completed by the O atom of the water mol­ecule and the Cl atom at the axial positions. The title compound contains intermolecular O—H?O hydrogen bonds. Apart from these hydrogen bonds, there are also intermolecular C—H?Cl and C—H?O contacts.     

Di‐μ‐iodo‐bis{[1,1′‐methyl­enebis(3,5‐dimethyl‐1H‐pyrazole‐κN2)]copper(I)}

In the title compound, [Cu₂I₂(C₁₁H₁₆N₄)₂], each of the two crystallographically equivalent Cu atoms is tetrahedrally coordinated by two N atoms from one 1,1′‐methyl­ene­bis(3,5‐di­methyl‐1H‐pyrazole) ligand and two bridging iodide anions. The mol­ecule has a crystallographic center of symmetry located at the mid‐point of the Cu·Cu line. One H atom of the CH₂ group of the 1,1′‐methyl­ene­bis(3,5‐di­methyl‐1H‐pyrazole) ligand interacts with an iodide ion in an adjacent mol­ecule to afford pairwise intermolecular C—H·I contacts, thereby forming chains of mol­ecules running along the [101] direction.     

[N,N′‐Bis(5‐bromo­salicyl­idene)‐o‐phenylene­diaminato]copper(II)

In the title compound, {4,4′‐di­bromo‐2,2′‐[o‐phenyl­ene­bis­(nitrilo­methyl­idene)]­di­phen­ol­ato‐O,N,N′,O′}copper(II), [Cu(C₂₀H₁₂Br₂N₂O₂], the Cu^II ion shows a slightly distorted square‐planar geometry with the N₂O₂ atoms of the Schiff base imine–phenol tetradentate ligand.     

3,5‐Di­fluoro‐4‐nitro­pyridine N‐oxide and 3,5‐di­amino‐4‐nitro­pyridine N‐oxide monohydrate

The mol­ecule of 3,5‐di­fluoro‐4‐nitro­pyridine N‐oxide, C₅H₂F₂N₂O₃, is twisted around the C—NO₂ bond by 38.5 (1)°, while the 3,5‐di­amino analogue, 3,5‐di­amino‐4‐nitro­pyridine N‐oxide monohydrate, C₅H₆N₄O₃·H₂O, adopts a planar conformation stabilized by intramolecular hydrogen bonds, with a significant redistribution of π electrons.     

Poly­[copper(I)‐μ‐bromo‐μ‐2,3‐di­methyl­pyrazine‐N:N′]

In the structure of the title compound, [CuBr(C₆H₈N₂)]_n, each Cu²⁺ cation is surrounded by two 2,3‐di­methyl­pyrazine ligands and two Br^? anions in a distorted tetrahedral arrangement. The Cu²⁺ cations and Br^? anions form (Cu₂Br₂)₂ rhomboid dimers located around a centre of inversion. The 2,3‐di­methyl­pyrazine ligands connect the Cu²⁺ cations in the dimers into sheets parallel to (010).     

Two N,N‐dimethylbiguanidium salts displaying double hydrogen bonds to the counter‐ions

The crystal structures of N,N‐di­methyl­biguanidium oxalate monohydrate, C₄H₁₃N₅²⁺·C₂O₄²⁻·H₂O, (I), and N,N‐di­methyl­biguanidium sulfate monohydrate, C₄H₁₃N₅²⁺·SO₄²⁻·H₂O, (II), show that both compounds contain the same N,N‐di­methyl­biguanidium dication. In (I), two independent oxalate ions lie about inversion centres. Strong double hydrogen bonds, with D⋯A distances of 2.658 (2) and 2.830 (3) Å in (I), and 2.722 (3) and 2.815 (3) Å in (II), are present between N atoms of the N,N‐di­methyl­biguanidium moieties and either the carboxyl­ate group of the oxalate anion or the sulfate anion.     

A structural hierarchy in the hydrogen‐bonded adduct N,N′‐di­methyl­piperazine–tartaric acid–water (1/2/2): an N‐component N‐dimensional structure (N = 3) with substructures having N = 1 and 2

In the hydrated adduct N,N′‐di­methyl­piperazine‐1,4‐diium bis(3‐carboxy‐2,3‐di­hydroxy­propanoate) dihydrate, [MeNH(CH₂CH₂)₂NHMe]²⁺·2(C₄H₅O₆)^?·2H₂O or C₆H₁₆N₂²⁺·2C₄H₅O₆^?·2H₂O, formed between racemic tartaric acid and N,N′‐di­methyl­piperazine (triclinic P, Z′ = 0.5), the cations lie across centres of inversion. The anions alone form chains, and anions and water mol­ecules together form sheets; the sheets are linked by the cations to form a pillared‐layer framework. The supramolecular architecture thus takes the form of a family of N‐dimensional N‐component structures having N = 1, 2 or 3.     

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).     

(6R*,16R*)‐9,14‐Dihydro‐6‐methyl‐6,16‐methano‐6H,16H‐[2,4]benzothiazepino[3,4‐d][1,3,5]benzoxadiazocine hydrobromide dimethylformamide hemisolvate

The title compound, C₁₉H₁₉N₂OS⁺·Br^?·0.5C₃H₇NO, is an oxygen‐bridged phenyl­pyrimidine derivative in which the heterocyclic ring is protonated, the positive charge being dispersed over both of the N atoms. Both mol­ecules in the asymmetric unit exist in an identical conformation, which consists of a central planar portion with the two terminal phenyl rings protruding from the same side of the plane. One of the independent mol­ecules forms a strong hydrogen bond with the bromide anion, while the other is hydrogen bonded to the di­methyl­form­amide solvent mol­ecule.     

4‐Di­methyl­amino­pyridinium bromide

The crystal and molecular structure of 4‐di­methyl­amino­pyridinium bromide, C₇H₁₁N₂^+.Br^?, (I), is built up by hydrogen‐bonded dimers of crystallographic 222 symmetry and four short C—H...halogen contacts. It is remarkable that (I) and 4‐di­methyl­amino­pyridinium chloride are not isostructural.     

cis‐[1,4‐Bis(di­phenyl­phosphino)­butane](μ‐tetra­thio­tungstato)­palladium(II) N,N′‐di­methyl­form­amide hemisolvate hemihydrate

In the title compound, [1,4‐bis(di­phenyl­phosphino)­butane‐2κ²P,P′]­di‐μ‐thio‐1:2κ⁴S‐di­thio‐1κ²S‐palladium(II)­tung­sten(VI) N,N′‐di­methyl­form­amide hemisolvate hemihydrate, [PdWS₄­(C₂₈H₂₈P₂)]·0.5C₃H₇NO·0.5H₂O, the Pd atom is coordinated by two S atoms from the distorted‐tetrahedral [WS₄]²⁻ anion and two P atoms from the dppb mol­ecule [dppb is 1,4‐bis(di­phenyl­phos­phino)­butane] in an approximately square‐planar configuration. A puckered seven‐membered ring is formed by the Pd atom and the dppb ligand.     

The diprotonated 2,2‐(propane‐1,3‐di­yl)bis­(1,1,3,3‐tetra­methyl­guanidinium) cation: packing and conformational changes

Subject to packing with different anions, the title cation undergoes various conformational changes with significantly different N—C—C—C torsion angles, as well as different angles between the NCN₂ guanidine planes. The 2,2‐(propane‐1,3‐di­yl)bis­(1,1,3,3‐tetra­methyl­guanidinium) salts reported here, viz. the dibromide, C₁₃H₃₂N₆²⁺·2Br⁻, the tetra­phenyl­borate chloride, C₁₃H₃₂N₆²⁺·C₂₄H₂₀B⁻·Cl⁻, the tetra­chloro­mercurate, (C₁₃H₃₂N₆)[HgCl₄], and the bis­(trifluoro­methanesulfonate), C₁₃H₃₂N₆²⁺·2CF₃SO₃⁻, are dominated by strong inter­molecular N—H⋯X hydrogen bonds, which form different packing patterns.     

[N,N′‐Bis(5‐bromo­salicyl­idene)‐1,3‐di­amino­propane]­nickel(II) and [N,N′‐­bis(5‐chloro­salicyl­idene)‐1,3‐­di­amino­propane]copper(II)

The title compounds, {4,4′‐di­bromo‐2,2′‐[1,3‐propane­diyl­bis(nitrilo­methyl­idyne‐N)]­diphenolato‐O,O′}nickel(II), [Ni(C₁₇­H₁₄­Br₂­N₂O₂)], and {4,4′‐di­chloro‐2,2′‐[1,3‐pro­pane­diyl­bis­(ni­trilo­methyl­idyne‐N)]­di­phen­ol­ato‐O,O′}­copper(II), [Cu­(C₁₇­H₁₄­Cl₂­N₂O₂)], lie on crystallographic twofold axes. In both structures, the metal coordination sphere is a tetrahedrally distorted square plane formed by the four‐coordinate N₂O₂ donor set of the Schiff base imine–phenol ligands. In the Ni compound, the Ni—O and Ni—N distances are 1.908 (3) and 1.959 (4) Å, respectively, while in the Cu compound, the Cu—O and Cu—N distances are 1.907 (2) and 1.960 (2) Å, respectively. The two Schiff base moieties, which themselves are nearly planar, are inclined at an angle of 29.26 (7)° for the Ni compound and 29.26 (5)° for the Cu compound.     

[N,N′‐Bis­(salicyl­idene)‐2,2‐di­methyl‐1,3‐propane­diaminato]­nickel(II) and [N,N′‐bis­(salicyl­idene)‐2,2‐di­methyl‐1,3‐propane­diaminato]copper(II)

In the title compounds, {2,2′‐[2,2‐di­methyl‐1,3‐propane­diyl­bis­(nitrilo­methyl­idyne)]­diphenolato‐κ⁴N,N′,O,O′}nickel(II), [Ni(C₁₉H₂₀N₂O₂)], and {2,2′‐[2,2‐di­methyl‐1,3‐propane­diyl­bis­(nitrilo­methyl­idyne)]­diphenolato‐κ⁴N,N′,O,O′}copper(II), [Cu(C₁₉H₂₀N₂O₂)], the Ni^II and Cu^II atoms are coordinated by two iminic N and two phenolic O atoms of the N,N′‐bis­(salicyl­idene)‐2,2‐di­methyl‐1,3‐propane­diaminate (SALPD^2?, C₁₇H₁₆N₂O₂^2?) ligand. The geometry of the coordination sphere is planar in the case of the Ni^II complex and distorted towards tetrahedral for the Cu^II complex. Both complexes have a cis configuration imposed by the chelate ligand. The dihedral angles between the N/Ni/O and N/Cu/O coordination planes are 17.20 (6) and 35.13 (7)°, respectively.     

rac‐ and meso‐3,3′‐Bis(3,5‐di­methyl­phenyl)‐3H,3′H‐2,2′‐biindenyl­idene‐1,1′(2H,2′H)‐dione

In the rac isomer of the title compound, C₃₄H₂₈O₂, the two C—Ph_{di­methyl­phenyl} bond axes make an angle of 58.7 (1)°. There is no short contact between the two 3,5‐di­methyl­phenyl rings, although the dihedral angle between them is 4.93 (7)°. The meso isomer has a center of symmetry at the middle of the C=C bond, and the two C—Ph_{di­methyl­phenyl} bond axes are antiparallel to one another.     

The 1:1 adduct of Kemp's triacid with 2‐aminopyridine

The crystal structure determination of the molecular proton‐transfer adduct of Kemp's triacid (cis‐cis‐1,3,5‐tri­methyl­cyclo­hexane‐1,3,5‐tri­carboxylic acid, KTA) with 2‐amino­pyridine (2‐APY), namely 2‐amino­pyridinium 3,5‐di­carboxy‐1,3,5‐tri­methyl­cyclo­hexane­carboxyl­ate, 2‐APY⁺·KTA^? or C₅H₇N₂⁺·C₁₂H₁₇O₆^?, has revealed a centrosymmetric hydrogen‐bonded cyclic KTA homodimer repeating unit [O?O 2.524 (4) Å] linked into a polymer structure through the pyridinium and amino groups of the 2‐APY mol­ecule [O?N 2.736 (4), 2.989 (4) and 2.999 (4) Å].