Polymorphism in 3‐acetyl‐4‐hydroxy‐2H‐chromen‐2‐one

A new polymorph (denoted polymorph II) of 3‐acetyl‐4‐hydroxy‐2H‐chromen‐2‐one, C₁₁H₈O₄, was obtained unexpectedly during an attempt to recrystallize the compound from salt–melted ice, and the structure is compared with that of the original polymorph (denoted polymorph I) [Lyssenko & Antipin (2001). Russ. Chem. Bull. 50 , 418–431]. Strong intramolecular O—H...O hydrogen bonds are observed equally in the two polymorphs [O...O = 2.4263 (13) Å in polymorph II and 2.442 (1) Å in polymorph I], with a slight delocalization of the hydroxy H atom towards the ketonic O atom in polymorph II [H...O = 1.32 (2) Å in polymorph II and 1.45 (3) Å in polymorph I]. In both crystal structures, the packing of the molecules is dominated and stabilized by weak intermolecular C—H...O hydrogen bonds. Additional π–π stacking interactions between the keto–enol hydrogen‐bonded rings stabilize polymorph I [the centres are separated by 3.28 (1) Å], while polymorph II is stabilized by interactions between α‐pyrone rings, which are parallel to one another and separated by 3.670 (5) Å.     

Crystal structures of the pyrazinamide–p‐aminobenzoic acid (1/1) cocrystal and the transamidation reaction product 4‐(pyrazine‐2‐carboxamido)benzoic acid in the molten state

The synthesis of pharmaceutical cocrystals is a strategy to enhance the performance of active pharmaceutical ingredients (APIs) without affecting their therapeutic efficiency. The 1:1 pharmaceutical cocrystal of the antituberculosis drug pyrazinamide (PZA) and the cocrystal former p‐aminobenzoic acid (p‐ABA), C₇H₇NO₂·C₅H₅N₃O, (1), was synthesized successfully and characterized by relevant solid‐state characterization methods. The cocrystal crystallizes in the monoclinic space group P2₁/n containing one molecule of each component. Both molecules associate via intermolecular O—H...O and N—H...O hydrogen bonds [O...O = 2.6102 (15) Å and O—H...O = 168.3 (19)°; N...O = 2.9259 (18) Å and N—H...O = 167.7 (16)°] to generate a dimeric acid–amide synthon. Neighbouring dimers are linked centrosymmetrically through N—H...O interactions [N...O = 3.1201 (18) Å and N—H...O = 136.9 (14)°] to form a tetrameric assembly supplemented by C—H...N interactions [C...N = 3.5277 (19) Å and C—H...N = 147°]. Linking of these tetrameric assemblies through N—H...O [N...O = 3.3026 (19) Å and N—H...O = 143.1 (17)°], N—H...N [N...N = 3.221 (2) Å and N—H...N = 177.9 (17)°] and C—H...O [C...O = 3.5354 (18) Å and C—H...O = 152°] interactions creates the two‐dimensional packing. Recrystallization of the cocrystals from the molten state revealed the formation of 4‐(pyrazine‐2‐carboxamido)benzoic acid, C₁₂H₉N₃O₃, (2), through a transamidation reaction between PZA and p‐ABA. Carboxamide (2) crystallizes in the triclinic space group P with one molecule in the asymmetric unit. Molecules of (2) form a centrosymmetric dimeric homosynthon through an acid–acid O—H...O hydrogen bond [O...O = 2.666 (3) Å and O—H...O = 178 (4)°]. Neighbouring assemblies are connected centrosymmetrically via a C—H...N interaction [C...N = 3.365 (3) Å and C—H...N = 142°] engaging the pyrazine groups to generate a linear chain. Adjacent chains are connected loosely via C—H...O interactions [C...O = 3.212 (3) Å and C—H...O = 149°] to generate a two‐dimensional sheet structure. Closely associated two‐dimensional sheets in both compounds are stacked via aromatic π‐stacking interactions engaging the pyrazine and benzene rings to create a three‐dimensional multi‐stack structure.     

Methyl 3,6‐di‐O‐pivaloyl‐α‐d‐manno­pyran­oside

The X‐ray crystal structure analysis of the title compound, C₁₇H₃₀O₈, revealed a ⁴C₁ conformation of the pyran­osyl ring [Cremer–Pople puckering parameters of Q = 0.568 (2) Å, θ = 5.1 (2) and ϕ = 218 (3)°]. The structure shows no deviations from the geometric parameters of pyran­oside carbohydrates. The hydroxyl groups participate in O—H⃛O hydrogen bonds, forming a two‐dimensional pattern [O⃛O = 2.811 (3) and 2.995 (3) Å].     

meso‐5,5,7,12,12,14‐Hexamethyl‐1,4‐diaza‐8,11‐diazoniacyclotetradecane bis(2‐naphthoate) ethanol disolvate: centrosymmetric five‐component aggregates linked into sheets by C—H⃛π(arene) hydrogen bonding

The title compound is an ethanol‐solvated salt, C₁₆H₃₈N₄²⁺·2C₁₁H₇O₂⁻·2C₂H₆O, in which the cation lies across a centre of inversion in P2₁/c. The ions are linked by N—H⃛O hydrogen bonds [H⃛O = 1.70 and 2.30 Å, N⃛O = 2.624 (2) and 3.136 (2) Å, and N—H⃛O = 178 and 151°], and the ethanol mol­ecule is linked to the anion by an O—H⃛O hydrogen bond [H⃛O = 1.90 Å, O⃛O = 2.728 (2) Å and O—H⃛O = 171°], to form a centrosymmetric five‐component aggregate. C—H⃛O hydrogen bonds and aromatic π–π‐stacking interactions are absent, but the aggregates are linked into sheets by a single C—H⃛π(arene) hydrogen bond.     

4‐Iodo­anilinium 3‐nitro­phthalate(1–): tripartite sheets built from O—H...O and N—H...O hydrogen bonds

In the title compound, 4‐iodoanilinium 2‐carboxy‐6‐nitrobenzoate, C₆H₇IN⁺·C₈H₄NO₆⁻, the anions are linked by an O—H...O hydrogen bond [H...O = 1.78 Å, O...O = 2.614 (3) Å and O—H...O = 171°] into C(7) chains, and these chains are linked by two two‐centre N—H...O hydrogen bonds [H...O = 1.86 and 1.92 Å, N...O = 2.700 (3) and 2.786 (3) Å, and N—H...O = 153 and 158°] and one three‐centre N—H...(O)₂ hydrogen bond [H...O = 2.02 and 2.41 Å, N...O = 2.896 (3) and 2.789 (3) Å, N—H...O = 162 and 105°, and O...H...O = 92°], thus forming sheets con­taining R(6), R(8), R(13) and R(18) rings.     

Assembling an isomer grid: the isomorphous 4‐, 3‐ and 2‐fluoro‐N′‐(4‐pyridyl)benzamides

The three title isomers, 4‐, (I), 3‐, (II), and 2‐fluoro‐N′‐(4‐pyridyl)benzamide, (III), all C₁₂H₉FN₂O, crystallize in the P2₁/c space group (No. 14) with similar unit‐cell parameters and are isomorphous and isostructural at the primary hydrogen‐bonding level. An intramolecular C—H...O=C interaction is present in all three isomers [C...O = 2.8681 (17)–2.884 (2) Å and C—H...O117–118°], with an additional N—H...F [N...F = 2.7544 (15) Å] interaction in (III). Intermolecular amide–pyridine N—H...N hydrogen bonds link molecules into one‐dimensional zigzag chains [graph set C(6)] along the [010] direction as the primary hydrogen bond [N...N = 3.022 (2), 3.049 (2) and 3.0213 (17) Å]. These are augmented in (I) by C—H...π(arene) and cyclic C—F...π(arene) contacts about inversion centres, in (II) by C—F...F—C interactions [C...F = 3.037 (2) Å] and weaker C—H...π(arene)/C—H...F contacts, and in (III) by C—H...π(arene) and C=O...O=C interactions, linking the alternating chains into two‐dimensional sheets. Typical amide N—H...O=C hydrogen bonds [as C(4) chains] are not present [N...O = 3.438 (2) Å in (I), 3.562 (2) Å in (II) and 3.7854 (16) Å in (III)]; the C=O group is effectively shielded and only participates in weaker interactions/contacts. This series is unusual as the three isomers are isomorphous (having similar unit‐cell parameters, packing and alignment), but they differ in their interactions and contacts at the secondary level.     

catena‐Poly[thorium(IV)‐tetrakis(μ2‐3‐carboxyadamantane‐1‐carboxylato)]: a quadruple helical strand driven by a synergy of coordination and hydrogen bonding

The title compound, [Th(C₁₂H₁₅O₄)₄]_n, is the first homoleptic thorium–carboxylate coordination polymer. It has a one‐dimensional structure supported by the bidentate bridging coordination of the singly charged 3‐carboxyadamantane‐1‐carboxylate (HADC⁻) anions. The metal ion is situated on a fourfold axis (site symmetry 4) and possesses a square‐antiprismatic ThO₈ coordination, including four bonds to anionic carboxylate groups [Th—O = 2.359 (2) Å] and four to neutral carboxyl groups [Th—O = 2.426 (2) Å], while a strong hydrogen bond between these two kinds of O‐atom donor [O...O = 2.494 (3) Å] affords planar pseudo‐chelated Th{CO₂...HO₂C} cycles. This combination of coordination and hydrogen bonding is responsible for the generation of quadruple helical strands of HADC⁻ ligands, which are wrapped around a linear chain of Th^IV ions [Th...Th = 7.5240 (4) Å] defining the helical axis.     

Synthesis and Structure Investigation of a Novel 3-Dimensional Potassium Supermolecular Compound Based on 2,4-Dinitro Resorcinol

A novel 3‐dimensional potassium supermolecular compound [K(HDNR)(H₂DNR)(H₂O)]_n (H₂DNR?2,4‐dinitro resorcinol) was synthesized and characterized by elemental analysis and FT‐IR spectroscopy. The crystal structure investigated by X‐ray single crystal diffraction shows that [K(HDNR)(H₂DNR)(H₂O)]_n crystallizes with a monoclinic unit cell in the space group P2(1)/c with unit cell dimensions of a=17.648(5) Å, b=12.527(3) Å, c=7.735(2) Å, β=94.33(2)°, V=1705.00(73) ų, Z=4. The structure was refined to the final R=0.0670 and wR=0.0722 for 2022 observed reflections with I>2σ(I). In the compound, potassium cation is assembled into one‐dimensional chains along c‐axis through oxygen atoms from water molecules, and the chains were connected by the bridged HDNR^? anions to form a two‐dimensional net structure. The two‐dimensional nets constructed a three‐dimensional supramolecular architecture via intermolecular hydrogen bonds and N–O···π interaction. Density functional theory (DFT) B3LYP was employed to optimize the structure and calculate energies for three tautomers of HDNR^? univalent anion. Three stable tautomers were located. It was found that the structure (I) with O(1) losing hydrogen atom is more stable than the structure (II) also with O(1) losing hydrogen atom and the structure (III) with O(4) losing hydrogen atom.     

Cobalt(II) and cadmium(II) square grids supported with 4,4′‐bipyrazole and accommodating 3‐carboxyadamantane‐1‐carboxylate

In poly[[bis(μ‐4,4′‐bi‐1H‐pyrazole‐κ²N²:N^2′)bis(3‐carboxyadamantane‐1‐carboxylato‐κO¹)cobalt(II)] dihydrate], {[Co(C₁₂H₁₅O₄)₂(C₆H₆N₄)₂]·2H₂O}_n, (I), the Co²⁺ cation lies on an inversion centre and the 4,4′‐bipyrazole (4,4′‐bpz) ligands are also situated across centres of inversion. In its non‐isomorphous cadmium analogue, {[Cd(C₁₂H₁₅O₄)₂(C₆H₆N₄)₂]·2H₂O}_n, (II), the Cd²⁺ cation lies on a twofold axis. In both compounds, the metal cations adopt an octahedral coordination, with four pyrazole N atoms in the equatorial plane [Co—N = 2.156 (2) and 2.162 (2) Å; Cd—N = 2.298 (2) and 2.321 (2) Å] and two axial carboxylate O atoms [Co—O = 2.1547 (18) Å and Cd—O = 2.347 (2) Å]. In both structures, interligand hydrogen bonding [N...O = 2.682 (3)–2.819 (3) Å] is essential for stabilization of the MN₄O₂ environment with its unusually high (for bulky adamantanecarboxylates) number of coordinated N‐donor co‐ligands. The compounds adopt two‐dimensional coordination connectivities and exist as square‐grid [M(4,4′‐bpz)₂]_n networks accommodating monodentate carboxylate ligands. The interlayer linkage is provided by hydrogen bonds from the carboxylic acid groups via the solvent water molecules [O...O = 2.565 (3) and 2.616 (3) Å] to the carboxylate groups in the next layer [O...O = 2.717 (3)–2.841 (3) Å], thereby extending the structures in the third dimension.     

New organic–inorganic frameworks incorporating iso‐ and heteropolymolybdate units and a 3,3′,5,5′‐tetramethyl‐4,4′‐bi‐1H‐pyrazole‐2,2′‐diium multiple hydrogen‐bond donor

Poly[bis(3,3′,5,5′‐tetramethyl‐4,4′‐bi‐1H‐pyrazole‐2,2′‐diium) γ‐octamolybdate(VI) dihydrate], {(C₁₀H₁₆N₄)₂[Mo₈O₂₆]·2H₂O}_n, (I), and bis(3,3′,5,5′‐tetramethyl‐4,4′‐bi‐1H‐pyrazole‐2,2′‐diium) α‐dodecamolybdo(VI)silicate tetrahydrate, (C₁₀H₁₆N₄)₂[SiMo₁₂O₄₀]·4H₂O, (II), display intense hydrogen bonding between the cationic pyrazolium species and the metal oxide anions. In (I), the asymmetric unit contains half a centrosymmetric γ‐type [Mo₈O₂₆]⁴⁻ anion, which produces a one‐dimensional polymeric chain by corner‐sharing, one cation and one water molecule. Three‐centre bonding with 3,3′,5,5′‐tetramethyl‐4,4′‐bi‐1H‐pyrazole‐2,2′‐diium, denoted [H₂Me₄bpz]²⁺ [N...O = 2.770 (4)–3.146 (4) Å], generates two‐dimensional layers that are further linked by hydrogen bonds involving water molecules [O...O = 2.902 (4) and 3.010 (4) Å]. In (II), each of the four independent [H₂Me₄bpz]²⁺ cations lies across a twofold axis. They link layers of [SiMo₁₂O₄₀]⁴⁻ anions into a three‐dimensional framework, and the preferred sites for pyrazolium/anion hydrogen bonding are the terminal oxide atoms [N...O = 2.866 (6)–2.999 (6) Å], while anion/aqua interactions occur preferentially viaμ₂‐O sites [O...O = 2.910 (6)–3.151 (6) Å].     

Syntheses and Structures of Two Selenite Chloride Hydrates: Co(HSeO3)Cl · 3 H2O and Cu(HSeO3)Cl · 2 H2O

The first selenite chloride hydrates, Co(HSeO₃)Cl · 3 H₂O and Cu(HSeO₃)Cl · 2 H₂O, have been prepared from solution and characterised by single‐crystal X‐ray diffraction. The cobalt phase adopts an unusual “one‐dimensional” structure built up from vertex‐sharing pyramidal [HSeO₃]^2–, and octahedral [CoO₂(H₂O)₄]^2– and [CoO₂(H₂O)₂Cl₂]^4– units. Inter‐chain bonding is by way of hydrogen bonds or van der Waals' interactions. The atomic arrangement of the copper phase involves [HSeO₃]^2– pyramids and Jahn‐Teller distorted [CuCl₂(H₂O)₄] and [CuO₄Cl₂]^8– octahedra, sharing vertices by way of Cu–O–Se and Cu–Cl–Cu bonds. Crystal data: Co(HSeO₃)Cl · 3 H₂O, M_r = 276.40, triclinic, space group P 1 (No. 2), a = 7.1657(5) Å, b = 7.3714(5) Å, c = 7.7064(5) Å, α = 64.934(1)°, β = 68.894(1)°, γ = 71.795(1)°, V = 337.78(7) ų, Z = 2, R(F) = 0.036, wR(F) = 0.049. Cu(HSeO₃)Cl · 2 H₂O, M_r = 263.00, orthorhombic, space group Pnma (No. 62), a = 9.1488(3) Å, b = 17.8351(7) Å, c = 7.2293(3) Å, V = 1179.6(2) ų, Z = 8, R(F) = 0.021, wR(F) = 0.024.     

Supramolecular Assemblies of Mononuclear and Polymeric Nickel(II) Glutarato Complexes via π‐π Stacking Interactions and Hydrogen Bonds: [Ni(H2O)3(phen)(C5H6O4)] · H2O and [Ni(H2O)2(phen)(C5H6O4)]

Syntheses of the sky blue complex compounds [Ni(H₂O)₃(phen)(C₅H₆O₄)] · H₂O ( 1 ) and [Ni(H₂O)₂(phen)(C₅H₆O₄)] ( 2 ) were carried out by the reactions of 1,10‐phenanthroline monohydrate, glutaric acid, NiSO₄ · 6 H₂O and Na₂CO₃ in CH₃OH/H₂O at pH = 6.9 and 7.5, respectively. The crystal structure of 1 (P 1 (no. 2), a = 14.289 Å, b = 15.182 Å, c = 15.913 Å, α = 67.108°, β = 87.27°, γ = 68.216°, V = 2934.2 ų, Z = 2) consists of hydrogen bonded [Ni(H₂O)₃‐ (phen)(C₅H₆O₄)]₂ dimers and H₂O molecules. The Ni atoms are octahedrally coordinated by two N atoms of one phen ligand, three water O atoms and one carboxyl O atom from one monodentate glutarato ligand (d(Ni–N) = 2.086, 2.090 Å; d(Ni–O) = 2.064–2.079 Å). Through the π‐π stacking interactions and intermolecular hydrogen bonds, the dimers are assembled to form 2 D layers parallel to (0 1 1). The crystal structure of 2 (P2₁/n (no. 14), a = 7.574 Å, b = 11.938 Å, c = 18.817 Å, β = 98.48°, V = 1682.8 ų, Z = 4) contains [Ni(H₂O)₂(phen)(C₅H₆O₄)_2/2] supramolecular chains extending along [010]. The Ni atoms are octahedrally coordinated by two N atoms of one phen ligand, two water O atoms and two carboxyl O atoms from different bis‐monodentate glutarato ligands with d(Ni–N) = 2.082, 2.105 Å and d(Ni–O) = 2.059–2.087 Å. The supramolecular chains are assembled into a 3 D network by π‐π stacking interactions and interchain hydrogen bonds. A TG/DTA of 2 shows two endothermic effects at 132 °C and 390 °C corresponding to the complete dehydration and the lost of phen.     

Three N2‐benzoyl­oxybenz­amidines: sheet structures built from hard and soft hydrogen bonds and aromatic π–π stacking interactions

Molecules of the title compounds N²‐(benzoyl­oxy)­benz­ami­dine, C₁₄H₁₂N₂O₂, (I), N²‐(2‐hydroxy­benzoyl­oxy)­benz­ami­dine, C₁₄H₁₂N₂O₃, (II), and N²‐benzoyloxy‐2‐hydroxybenzamidine, C₁₄H₁₂N₂O₃, (III), all have extended chain conformations, with the aryl groups remote from one another. In (I), the mol­ecules are linked into chains by a single N—H⋯N hydrogen bond [H⋯N = 2.15 Å, N⋯N = 3.029 (2) Å and N—H⋯N = 153°] and these chains are linked into sheets by means of aromatic π–π stacking interactions. There is one intramolecular O—H⋯O hydrogen bond in (II), and a combination of one three‐centre N—H⋯(N,O) hydrogen bond [H⋯N = 2.46 Å, H⋯O = 2.31 Å, N⋯N = 3.190 (2) Å, N⋯O = 3.146 (2) Å, N—H⋯N = 138° and N—H⋯O = 154°] and one two‐centre C—H⋯O hydrogen bond [H⋯O = 2.46 Å, C⋯O = 3.405 (2) Å and C—H⋯O = 173°] links the mol­ecules into sheets. In (III), an intramolecular O—H⋯N hydrogen bond and two N—H⋯O hydrogen bonds [H⋯O = 2.26 and 2.10 Å, N⋯O = 2.975 (2) and 2.954 (2) Å, and N—H⋯O = 138 and 163°] link the molecules into sheets.     

Dibenzylammonium hydrogen maleate and a redetermination at 120 K of bis(dibenzylamino)methane

In dibenzylammonium hydrogen maleate [or dibenzylammonium (2Z)‐3‐carboxyprop‐2‐enoate], C₁₄H₁₆N⁺·C₄H₃O₄⁻, (I), the anion contains a fairly short and nearly linear O—H...O hydrogen bond, with an O...·O distance of 2.4603 (16) Å, but with the H atom clearly offset from the mid‐point of the O...O vector. The counter‐ions in (I) are linked by two N—H...O hydrogen bonds to form C₂²(6) chains and these chains are weakly linked into sheets by a C—H...O hydrogen bond. Bis(dibenzylamino)methane, C₂₉H₃₀N₂, (II), crystallizes with two independent molecules lying across twofold rotation axes in the space group C2/c, and the molecules are conformationally chiral; there are no direction‐specific intermolecular interactions in the crystal structure of (II).     

Synthesis,crystal structure and magnetic properties of new MnIII–CuII heterometallic aggregates based on multidentate Schiff-base ligands

Reaction of copper powder, manganese(II) nitrates and multidentate Schiff-base ligands in hot methanol solution led to the isolation of two new Mn^III–Cu^II heterometallic aggregates, [Mn₂ ^IIICu₂ ^II(H₂L)₄] · (NO₃)₂ · 2CH₃OH (1) (H₄L=2-[(2-hydroxy-benzylidene)-amino]-2-hydroxymethyl-proane-1,3-diol) and [Mn^IIICu^II ₃(sae)₄(MeOH)(H₂O)₃] · NO₃ · MeOH (2) (H₂sae = salicylidene-2-ethanolamine). Both compounds were characterized by elemental analysis, IR, XPS, EPR, XRPD and single crystal X-ray diffraction. Compound 1 crystallizes in the triclinic space group P 1 with a = 11.1268(4) Å, b = 11.6153(4) Å, c = 11.8129(5) Å, α = 88.435(10)°, β = 80.203(10)°, γ = 77.572(10)°, V = 1469.13(10) ų, Z = 1, R1(wR2) =0.0300(0.0771). Compound 2 crystallizes in the monoclinic space group P2₁/n with a = 18.1715(7), b = 12.9931(5), c = 19.5903(8) Å, β = 97.1980(10)°, V = 4588.9(3) ų, Z = 4, R1(wR2) = 0.0667 (0.1998). The magnetic susceptibilities of 1 and 2 display the antiferromagnetic interactions in both compounds.     

3,3′,5,5′‐Tetramethyl‐4,4′‐bipyrazole–pentafluorophenol (2/3)

In the title compound, 2C₁₀H₁₄N₄·3C₆HF₅O, one of the pentafluorophenol molecules resides on a mirror plane bisecting the O...F axis. The components aggregate by N—H...N, N—H...O and O—H...N hydrogen bonds involving equal disordering of the H atoms into molecular ensembles based on a 2:1 pyrazole–phenol cyclic pattern [O...N = 2.7768 (16) Å and N...N = 2.859 (2) Å], crosslinked into one‐dimensional columns via hydrogen bonding between the outer pyrazole groups and additional pentafluorophenol molecules. The latter yields a 1:1 pyrazole–phenol catemer with alternating strong O—H...N [2.5975 (16) Å] and weaker N—H...O [2.8719 (17) Å] hydrogen bonds. This is the first reported molecular adduct of a pentafluorinated phenol and a nitrogen base, and suggests the utility of highly acidic phenols and pyrazoles for developing hydrogen‐bonded cocrystals.     

Two Modifications of NH4HPO3F: Synthesis and Crystal Structure

The α and β modifications of NH₄HPO₃F were synthesized and characterized with single crystal X‐ray diffraction. The crystal structure of α‐NH₄HPO₃F determined at 180 K is monoclinic, space group P2₁/n, with a = 7.4650(1), b = 15.586(2), c = 7.5785(9) Å, β = 108.769(9)°, V = 834.9(2) ų, Z = 8, and R₁ = 0.0376 and wR₂ = 0.0818. β‐NH₄HPO₃F measured at 310 K crystallizes in the triclinic space group, P 1, with a = 7.481(1), b = 7.511(1), c = 7.782(1) Å, α = 84.31(1), β = 84.20(1), γ = 68.67(2)°, V = 404.31(9) ų, Z = 4, and R₁ = 0.0254 and wR₂ = 0.0735. A phase transition was not observed between 180 and 310 K for β‐NH₄HPO₃F. Both modifications of NH₄HPO₄F consist of HPO₃F^– and NH₄⁺ units. Two pairs of two unique anions are linked to each other by O–H…O hydrogen bonds to form cyclic tetramers held together by N–H…O bonds. No O–H…F or N–H…F bonds were observed.     

Synthesis and Crystal Structures of Manganese(II) and ­Cobalt(II) Complexes with 2, 6‐Dimethoxybenzoic Acid and Additional N‐Donor Ligands

Three coordination compounds [Mn₃(dmb)₆(H₂O)₄(4, 4′‐bpy)₃(EtOH)]_n ( 1 ) and [M(dmb)₂(pyz)₂ (H₂O)₂] [M^II = Co ( 2 ), Mn ( 3 )] (Hdmb = 2, 6‐dimethoxybenzoic acid, 4, 4′‐bpy = 4, 4′‐bipyridine, pyz = pyrazine) were synthesized and characterized by single‐crystal X‐ray diffraction analysis. Compound 1 consists of infinite 1D polymeric chains, in which the metal entities are bridged by 4, 4′‐bpy ligands. There are four crystallographically independent Mn^II atoms in the linear chain with different coordination modes, which is only scarcely reported for linear polymers. The isostructural crystals of 2 and 3 are composed of neutral mononuclear complexes. In crystal the complexes are combined into chains by intermolecular O–H ··· N hydrogen bonds and π–π interactions between antiparallel pyrazine molecules.     

2,3:4,6‐Di‐O‐isopropylidene‐α‐l‐sorbofuranose and 2,3‐O‐isopropylidene‐α‐l‐sorbofuranose

In the title compounds, C₁₂H₂₀O₆, (I), and C₉H₁₆O₆, (II), the five‐membered furanose ring adopts a ⁴T₃ conformation and the five‐membered 1,3‐dioxolane ring adopts an E₃ conformation. The six‐membered 1,3‐dioxane ring in (I) adopts an almost ideal ^OC₃ conformation. The hydrogen‐bonding patterns for these compounds differ substantially: (I) features just one intramolecular O—H...O hydrogen bond [O...O = 2.933 (3) Å], whereas (II) exhibits, apart from the corresponding intramolecular O—H...O hydrogen bond [O...O = 2.7638 (13) Å], two intermolecular bonds of this type [O...O = 2.7708 (13) and 2.7730 (12) Å]. This study illustrates both the similarity between the conformations of furanose, 1,3‐dioxolane and 1,3‐dioxane rings in analogous isopropylidene‐substituted carbohydrate structures and the only negligible influence of the presence of a 1,3‐dioxane ring on the conformations of furanose and 1,3‐dioxolane rings. In addition, in comparison with reported analogs, replacement of the –CH₂OH group at the C1‐furanose position by another group can considerably affect the conformation of the 1,3‐dioxolane ring.