Self‐assembled supramolecular sheet‐ and channel‐type frameworks in the p‐phenetidinium hydrogen phthalate and cyclohexylaminium hydrogen phthalate hemihydrate salts

The title compounds, p‐phenetidinium hydrogen phthalate (or 4‐ethoxyanilinium 2‐carboxybenzoate), C₈H₁₂NO⁺·C₈H₅O₄⁻, (I), and cyclohexylaminium hydrogen phthalate hemihydrate (or cyclohexylaminium 2‐carboxybenzoate hemihydrate), C₆H₁₄N⁺·C₈H₅O₄⁻·0.5H₂O, (II), form two‐ and one‐dimensional supramolecular networks, respectively. In (I), the anionic–cationic network consists of R₃²(6) and R₄⁴(16) hydrogen‐bonded rings forming a two‐dimensional sheet along the (001) plane. In (II), O—H...O hydrogen bonds connect the glide‐related anions, generating a supramolecular chain running parallel to [001] to which the cations are linked to form one‐dimensional channels along [001]. The solvent water molecules, which reside on twofold axes, are trapped inside the molecular channels by N—H...O and O—H...O hydrogen bonds.     

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).     

Potassium salts of hypodiphosphoric acid

The synthesis and crystal structures of a series of six crystalline potassium salts of hypodiphosphoric acid, H₄P₂O₆, are reported, namely potassium hydrogen phosphonophosphonate, K⁺·H₃P₂O₆⁻, (I), dipotassium dihydrogen hypodiphosphate monohydrate, 2K⁺·H₂P₂O₆²⁻·H₂O, (II), dipotassium dihydrogen hypodiphosphate dihydrate, 2K⁺·H₂P₂O₆²⁻·2H₂O, (III), pentapotassium hydrogen hypodiphosphate dihydrogen hypodiphosphate dihydrate, 5K⁺·HP₂O₆³⁻·H₂P₂O₆²⁻·2H₂O, (IV), tripotassium hydrogen hypodiphosphate tetrahydrate, 3K⁺·HP₂O₆³⁻·4H₂O, (V), and tetrapotassium hypodiphosphate tetrahydrate, 4K⁺·P₂O₆⁴⁻·4H₂O, (VI). All the hypodiphosphate anions, viz. H₃P₂O₆⁻, H₂P₂O₆²⁻, HP₂O₆³⁻ and P₂O₆⁴⁻, adopt a staggered conformation. The P—P bond lengths [2.1722 (7)–2.1892 (10) Å] do not depend on the basicity of the anion. The compounds are organized into different types of one‐, two‐ or three‐dimensional polymeric hydrogen‐bonded networks, or simply exist in the form of isolated or dimeric units. The coordination numbers of the K⁺ cations range from 6 to 9, and the cationic sublattices are polymeric one‐, two‐ or three‐dimensional networks, or isolated [KO₆] or dimeric [K₂O₁₂] polyhedra.     

Hydrogen bonding in two ammonium salts of 5‐sulfosalicylic acid: ammonium 3‐carboxy‐4‐hydroxybenzenesulfonate monohydrate and triammonium 3‐carboxy‐4‐hydroxybenzenesulfonate 3‐carboxylato‐4‐hydroxybenzenesulfonate

The structures of two ammonium salts of 3‐carboxy‐4‐hydroxybenzenesulfonic acid (5‐sulfosalicylic acid, 5‐SSA) have been determined at 200 K. In the 1:1 hydrated salt, ammonium 3‐carboxy‐4‐hydroxybenzenesulfonate monohydrate, NH₄⁺·C₇H₅O₆S⁻·H₂O, (I), the 5‐SSA⁻ monoanions give two types of head‐to‐tail laterally linked cyclic hydrogen‐bonding associations, both with graph‐set R₄⁴(20). The first involves both carboxylic acid O—H...O_water and water O—H...O_sulfonate hydrogen bonds at one end, and ammonium N—H...O_sulfonate and N—H...O_carboxy hydrogen bonds at the other. The second association is centrosymmetric, with end linkages through water O—H...O_sulfonate hydrogen bonds. These conjoined units form stacks down c and are extended into a three‐dimensional framework structure through N—H...O and water O—H...O hydrogen bonds to sulfonate O‐atom acceptors. Anhydrous triammonium 3‐carboxy‐4‐hydroxybenzenesulfonate 3‐carboxylato‐4‐hydroxybenzenesulfonate, 3NH₄⁺·C₇H₄O₆S²⁻·C₇H₅O₆S⁻, (II), is unusual, having both dianionic 5‐SSA²⁻ and monoanionic 5‐SSA⁻ species. These are linked by a carboxylic acid O—H...O hydrogen bond and, together with the three ammonium cations (two on general sites and the third comprising two independent half‐cations lying on crystallographic twofold rotation axes), give a pseudo‐centrosymmetric asymmetric unit. Cation–anion hydrogen bonding within this layered unit involves a cyclic R₃³(8) association which, together with extensive peripheral N—H...O hydrogen bonding involving both sulfonate and carboxy/carboxylate acceptors, gives a three‐dimensional framework structure. This work further demonstrates the utility of the 5‐SSA⁻ monoanion for the generation of stable hydrogen‐bonded crystalline materials, and provides the structure of a dianionic 5‐SSA²⁻ species of which there are only a few examples in the crystallographic literature.     

A square two‐dimensional polymer of cobalt citrate cubanes

The structure of the title complex, poly[dicaesium(I) hexaaquacobalt(II) [octaaquatetra‐μ‐citrato‐hexacobalt(II)] dodecahydrate], {Cs₂[Co(H₂O)₆][Co₆(C₆H₄O₇)₄(H₂O)₈]·12H₂O}_n, at 100 (1) K is formed by layers of a square two‐dimensional polymer composed of Co^II citrate cubanes bridged by magnetically active six‐coordinate Co^II cations. The polymer has plane symmetry p4mm in the c‐axis projection. The cubanes reside on sites of crystallographic symmetry , while the bridging Co^II centres lie on twofold axes. The basic polymeric unit has a charge of 4−, balanced by two Cs⁺ and a [Co(H₂O)₆]²⁺ (symmetry ) cation, which lie in channels between the polymeric layers. Unligated water molecules, of which there are 12 per cubane, enter into an extended intralayer and layer‐bridging hydrogen‐bond pattern, which can be described in detail even though not all of the H atoms of the water molecules were located.     

Sodium hydrogen bis­(phenoxy­acetate)

In the title compound, Na⁺·H⁺·2C₈H₇O₃⁻, the anion contains a short Speakman-type hydrogen bond [O⃛O = 2.413 (2) Å]. The anions and the Na atoms lie across twofold axes.     

Six two‐ and three‐component ammonium carboxylate salt structures with a ladder‐type hydrogen‐bonding motif,three incorporating neutral carboxylic acid molecules

Six ammonium carboxylate salts are synthesized and reported, namely 2‐propylammonium benzoate, C₃H₁₀N⁺·C₇H₅O₂⁻, (I), benzylammonium (R)‐2‐phenylpropionate, C₆H₁₀N⁺·C₉H₉O₂⁻, (II), (RS)‐1‐phenylethylammonium naphthalene‐1‐carboxylate, C₈H₁₂N⁺·C₁₁H₇O₂⁻, (III), benzylammonium–benzoate–benzoic acid (1/1/1), C₆H₁₀N⁺·C₇H₅O₂⁻·C₇H₆O₂, (IV), cyclopropylammonium–benzoate–benzoic acid (1/1/1), C₃H₈N⁺·C₇H₅O₂⁻·C₇H₆O₂, (V), and cyclopropylammonium–ea‐cis‐cyclohexane‐1,4‐dicarboxylate–ee‐trans‐cyclohexane‐1,4‐dicarboxylic acid (2/1/1), 2C₃H₈N⁺·C₈H₁₀O₄²⁻·C₈H₁₂O₄, (VI). Salts (I)–(III) all have a 1:1 ratio of cation to anion and feature three N⁺—H...O⁻ hydrogen bonds which form one‐dimensional hydrogen‐bonded ladders. Salts (I) and (II) have type II ladders, consisting of repeating R₄³(10) rings, while (III) has type III ladders, in this case consisting of alternating R₄²(8) and R₄⁴(12) rings. Salts (IV) and (V) have a 1:1:1 ratio of cation to anion to benzoic acid. They have type III ladders formed by three N⁺—H...O⁻ hydrogen bonds, while the benzoic acid molecules are pendant to the ladders and hydrogen bond to them via O—H...O⁻ hydrogen bonds. Salt (VI) has a 2:1:1 ratio of cation to anion to acid and does not feature any hydrogen‐bonded ladders; instead, the ionized and un‐ionized components form a three‐dimensional network of hydrogen‐bonded rings. The two‐component 1:1 salts are formed from a 1:1 ratio of amine to acid. To create the three‐component salts (IV)–(VI), the ratio of amine to acid was reduced so as to deprotonate only half of the acid molecules, and then to observe how the un‐ionized acid molecules are incorporated into the ladder motif. For (IV) and (V), the ratio of amine to acid was reduced to 1:2, while for (VI) the ratio of amine to acid required to deprotonate only half the diacid molecules was 1:1.     

Picolinamidium squarate and di‐p‐toluidinium squarate dihydrate

The crystal structure determinations of picolinamidium squarate, C₆H₇N₂O⁺·C₄O₄⁻, (I), and di‐p‐toluidinium squarate dihydrate, 2C₇H₁₀N⁺·C₄O₄²⁻·2H₂O, (II), are reported. While salt formation occurs by donation of one H atom from squaric acid to the picolin­amide mol­ecule in (I), in compound (II), each squaric acid mol­ecule donates one H atom to the p‐toluidine N atom of two trans p‐toluidine molecules. In (I), the pyridine ring is coplanar with the squarate monoanion through imposed crystallographic mirror symmetry; in (II), the dihedral angle between the p‐toluidine moiety and the squarate dianion is 70.71 (1)°. In (I), a three‐dimensional structure is formed via van der Waals interactions between parallel planes of mol­ecules, with hydrogen‐bond interactions (N—H⋯O and O—H⋯O) acting within the planes; hydrogen bonds form a three‐dimensional network in (II).     

Bis(diisopropylammonium) thiosulfate and bis(tert‐butylammonium) thiosulfate

Two new dialkylammonium thiosulfates, namely bis(diisopropylammonium) thiosulfate, 2C₆H₁₆N⁺·S₂O₃²⁻, (I), and bis(tert‐butylammonium) thiosulfate, 2C₄H₁₂N⁺·S₂O₃²⁻, (II), have been characterized. The secondary ammonium salt (I) crystallizes with Z = 4, while the primary ammonium salt (II), with more hydrogen‐bond donors, crystallizes with Z = 8 and a noncrystallographic centre of inversion. In both salts, the organic cations and thiosulfate anions are linked within extensive N—H...O and N—H...S hydrogen‐bond networks, forming extended two‐dimensional layers. Layers are parallel to (10) in (I) and to (002) in (II), and have a polar interior and a nonpolar hydrocarbon exterior. The layered structure and hydrogen‐bond motifs observed in (I) and (II) are similar to those in related ammonium sulfates.     

New coordination modes in potassium edta salts: K2[H2edta]·2H2O,K3[Hedta]·2H2O and K4[edta]·3.92H2O

Three potassium edta (edta is ethylenediaminetetraacetic acid, H₄Y) salts which have different degrees of ionization of the edta anion, namely dipotassium 2‐({2‐[bis(carboxylatomethyl)azaniumyl]ethyl}(carboxylatomethyl)azaniumyl)acetate dihydrate, 2K⁺·C₁₀H₁₄N₂O₈²⁻·2H₂O, (I), tripotassium 2,2′‐({2‐[bis(carboxylatomethyl)amino]ethyl}ammonio)diacetate dihydrate, 3K⁺·C₁₀H₁₃N₂O₈³⁻·2H₂O, (II), and tetrapotassium 2,2′,2′′,2′′′‐(ethane‐1,2‐diyldinitrilo)tetraacetate 3.92‐hydrate, 4K⁺·C₁₀H₁₂N₂O₈⁴⁻·3.92H₂O, (III), were obtained in crystalline form from water solutions after mixing edta with potassium hydroxide in different molar ratios. In (II), a new mode of coordination of the edta anion to the metal is observed. The HY³⁻ anion contains one deprotonated N atom coordinated to K⁺ and the second N atom is involved in intramolecular bifurcated N—H...O and N—H...N hydrogen bonds. The overall conformation of the HY³⁻ anions is very similar to that of the Y⁴⁻ anions in (III), although a slightly different spatial arrangement of the –CH₂COO⁻ groups in relation to (III) is observed, whereas the H₂Y²⁻ anions in (I) adopt a distinctly different geometry. The preferred synclinal conformation of the –NCH₂CH₂N– moiety was found for all edta anions. In all three crystals, the anions and water molecules are arranged in three‐dimensional networks linked via O—H...O and C—H...O [and N—H...O in (I) and (II)] hydrogen bonds. K...O interactions also contribute to the three‐dimensional polymeric architecture of the salts.     

Conformational isomers of the [(5‐methyl‐2‐pyridinio)aminomethylene]diphosphonate dianion and [(5‐methyl‐2‐pyridyl)aminomethylene]diphosphonate trianion in salts with 4‐aminopyridine and ammonia

The crystal structures of two salts, products of the reactions between [(5‐methyl‐2‐pyridyl)aminomethylene]bis(phosphonic acid) and 4‐aminopyridine or ammonia, namely bis(4‐aminopyridinium) hydrogen [(5‐methyl‐2‐pyridinio)aminomethylene]diphosphonate 2.4‐hydrate, 2C₅H₇N₂⁺·C₇H₁₀N₂O₆P₂²⁻·2.4H₂O, (I), and triammonium hydrogen [(5‐methyl‐2‐pyridyl)aminomethylene]diphosphonate monohydrate, 3NH₄⁺·C₇H₉N₂O₆P₂³⁻·H₂O, (II), have been determined. In (I), the Z configuration of the ring N—C and amino N—H bonds of the bisphosphonate dianion with respect to the C_ring—N_amino bond is consistent with that of the parent zwitterion. Removing the H atom from the pyridyl N atom results in the opposite E configuration of the bisphosphonate trianion in (II). Compound (I) exhibits a three‐dimensional hydrogen‐bonded network, in which 4‐aminopyridinium cations and water molecules are joined to ribbons composed of anionic dimers linked by O—H...O and N—H...O hydrogen bonds. The supramolecular motif resulting from a combination of these three interactions is a common phenomenon in crystals of all of the Z‐isomeric zwitterions of 4‐ and 5‐substituted (2‐pyridylaminomethylene)bis(phosphonic acid)s studied to date. In (II), ammonium cations and water molecules are linked to chains of trianions, resulting in the formation of double layers.     

Water‐induced pseudo‐quadruple hydrogen‐bonding motifs in xanthine–inorganic acid complexes

In xanthinium nitrate hydrate [systematic name: 2,6‐dioxo‐1,2,3,6‐tetrahydro‐9H‐purin‐7‐ium nitrate monohydrate], C₅H₅N₄O₂⁺·NO₃⁻·H₂O, (I), and xanthinium hydrogen sulfate hydrate [systematic name: 2,6‐dioxo‐1,2,3,6‐tetrahydro‐9H‐purin‐7‐ium hydrogen sulfate monohydrate], C₅H₅N₄O₂⁺·HSO₄⁻·H₂O, (II), the xanthine molecules are protonated at the imine N atom with the transfer of an H atom from the inorganic acid. The asymmetric unit of (I) contains a xanthinium cation, a nitrate anion and one water molecule, while that of (II) contains two crystallographically independent xanthinium cations, two hydrogen sulfate anions and two water molecules. A pseudo‐quadruple hydrogen‐bonding motif is formed between the xanthinium cations and the water molecules via N—H...O and O—H...O hydrogen bonds in both structures, and leads to the formation of one‐dimensional polymeric tapes. These cation–water tapes are further connected by the respective anions and aggregate into two‐dimensional hydrogen‐bonded sheets in (I) and three‐dimensional arrangements in (II).     

Polysulfonylamine. CLXIII [1] Kristallstrukturen von Metall‐di(methansulfonyl)amiden. 12 [1] Das orthorhombische Doppelsalz Na2Cs2[(CH3SO2)2N]4·3H2O: Ein dreidimensionales Koordinationspolymer aus (Caesium‐Anion‐Wasser)‐Schichten und intercalierten Natriumionen

Polysulfonylamines. CLXIII. Crystal Structures of Metal Di(methanesulfonyl)amides. 12. The Orthorhombic Double Salt Na₂Cs₂[(CH₃SO₂)₂N]₄·3H₂O: A Three‐Dimensional Coordination Polymer Built up from Cesium‐Anion‐Water Layers and Intercalated Sodium Ions The packing arrangement of the three‐dimensional coordination polymer Na₂Cs₂[(MeSO₂)₂N]₄·3H₂O (orthorhombic, space group Pna2₁, Z′ = 1) is in some respects similar to that of the previously reported sodium‐potassium double salt Na₂K₂[(MeSO₂)₂N]₄·4H₂O (tetragonal, P4₃2₁2, Z′ = 1/2). In the present structure, four multidentately coordinating independent anions, three independent aquo ligands and two types of cesium cation form monolayer substructures that are associated in pairs to form double layers via a Cs(1)—H₂O—Cs(2) motif, thus conferring upon each Cs⁺ an irregular O₈N₂ environment drawn from two N, O‐chelating anions, two O, O‐chelating anions and two water molecules. Half of the sodium ions occupy pseudo‐inversion centres situated between the double layers and have an octahedral O₆ coordination built up from four anions and two water molecules, whereas the remaining Na⁺ are intercalated within the double layers in a square‐pyramidal and pseudo‐C₂ symmetric O₅ environment provided by four anions and the water molecule of the Cs—H₂O—Cs motif. The net effect is that each of the four independent anions forms bonds to two Cs⁺ and two Na⁺, two independent water molecules are involved in Cs—H₂O—Na motifs, and the third water molecule acts as a μ₃‐bridging ligand for two Cs⁺ and one Na⁺. The crystal cohesion is reinforced by a three‐dimensional network of conventional O—H···O=S and weak C—H···O=S/N hydrogen bonds.     

A 16‐connected three‐dimensional hydrogen‐bonding network in tetrakis(4‐aminopyridinium) perylene‐3,4,9,10‐tetracarboxylate octahydrate

The novel title organic salt, 4C₅H₇N₂⁺·C₂₄H₈O₈⁴⁻·8H₂O, was obtained from the reaction of perylene‐3,4,9,10‐tetracarboxylic acid (H₄ptca) with 4‐aminopyridine (4‐ap). The asymmetric unit contains half a perylene‐3,4,9,10‐tetracarboxylate (ptca⁴⁻) anion with twofold symmetry, two 4‐aminopyridinium (4‐Hap⁺) cations and four water molecules. Strong N—H...O hydrogen bonds connect each ptca⁴⁻ anion with four 4‐Hap⁺ cations to form a one‐dimensional linear chain along the [010] direction, decorated by additional 4‐Hap⁺ cations attached by weak N—H...O hydrogen bonds to the ptca⁴⁻ anions. Intermolecular O—H...O interactions of water molecules with ptca⁴⁻ and 4‐Hap⁺ ions complete the three‐dimensional hydrogen‐bonding network. From the viewpoint of topology, each ptca⁴⁻ anion acts as a 16‐connected node by hydrogen bonding to six 4‐Hap⁺ cations and ten water molecules to yield a highly connected hydrogen‐bonding framework. π–π interactions between 4‐Hap⁺ cations, and between 4‐Hap⁺ cations and ptca⁴⁻ anions, further stabilize the three‐dimensional hydrogen‐bonding network.     

Hydrogen‐bond‐directed supramolecular arrays in 4,4′‐bipyridinium tetrachloroterephthalate dihydrate and bis(1,10‐phenanthrolinium) tetrachloroterephthalate tetrachloroterephthalic acid trihydrate

The title compounds, C₁₀H₁₀N₂²⁺·C₈Cl₄O₄²⁻·2H₂O, (I), and 2C₁₂H₉N₂⁺·C₈Cl₄O₄²⁻·C₈H₂Cl₄O₄·3H₂O, (II), both crystallize as charge‐transfer organic salts with the dianionic or neutral acid components lying on inversion centres. The acid and base subunits in (I) arrange alternately to generate a linear tape motif via N—H...O hydrogen bonds; these tapes are further combined into a three‐dimensional architecture through multiple O—H...O and C—H...O interactions involving solvent water molecules. In contrast, the neutral and anionic acid components in (II) are linked to form a zigzag chain by means of O—H...O hydrogen bonds between acid groups, with dangling 1,10‐phenanthrolinium units connected to these chains by carboxylate–pyridinium interactions with R₂²(7) hydrogen‐bond notation. Adjacent chains are further extended to result in a two‐dimensional corrugated layer network viaπ–π interactions. Inter‐ion Cl...O interactions are also found in both (I) and (II).     

Three‐dimensional networks in bis(imidazolium) 2,2′‐dithiodibenzoate and 4‐methylimidazolium 2‐[(2‐carboxyphenyl)disulfanyl]benzoate

Cocrystallization of imidazole or 4‐methylimidazole with 2,2′‐dithiodibenzoic acid from methanol solution yields the title 2:1 and 1:1 organic salts, 2C₃H₅N₂⁺·C₁₄H₁₀O₄S₂²⁻, (I), and C₄H₇N₂⁺·C₁₄H₁₀O₄S₂⁻, (II), respectively. Compound (I) crystallizes in the monoclinic C2/c space group with the mid‐point of the S—S bond lying on a twofold axis. The component ions in (I) are linked by intermolecular N—H...O hydrogen bonds to form a two‐dimensional network, which is further linked by C—H...O hydrogen bonds into a three‐dimensional network. In contrast, by means of N—H...O, N—H...S and O—H...O hydrogen bonds, the component ions in (II) are linked into a tape and adjacent tapes are further linked by π–π, C—H...O and C—H...π interactions, resulting in a three‐dimensional network.     

Three‐dimensional hydrogen‐bonded structures in the guanidinium salts of the monocyclic dicarboxylic acids rac‐trans‐cyclohexane‐1,2‐dicarboxylic acid (2:1, anhydrous), isophthalic acid (1:1, monohydrate) and terephthalic acid (2:1, trihydrate)

The structures of bis(guanidinium) rac‐trans‐cyclohexane‐1,2‐dicarboxylate, 2CH₆N₃⁺·C₈H₁₀O₄²⁻, (I), guanidinium 3‐carboxybenzoate monohydrate, CH₆N₃⁺·C₈H₅O₄⁻·H₂O, (II), and bis(guanidinium) benzene‐1,4‐dicarboxylate trihydrate, 2CH₆N₃⁺·C₈H₄O₄²⁻·3H₂O, (III), all reveal three‐dimensional hydrogen‐bonded framework structures. In anhydrous (I), both guanidinium cations form classic cyclic R₂²(8) N—H...O,O′_carboxylate and asymmetric cyclic R₂¹(6) hydrogen‐bonding interactions, while one cation forms an unusual enlarged cyclic interaction with O‐atom acceptors of separate ortho‐related carboxylate groups [graph set R₂²(11)]. Cations and anions also associate across inversion centres, giving cyclic R₄²(8) motifs. In the 1:1 guanidinium salt, (II), the cation forms two separate cyclic R₂¹(6) interactions, one with a carboxyl O‐atom acceptor and the other with the solvent water molecule. The structure is unusual in that both carboxyl groups form short interanion O...H...O contacts, one across a crystallographic inversion centre [O...O = 2.483 (2) Å] and the other about a twofold axis of rotation [O...O = 2.462 (2) Å], representing shared sites on these elements for the single acid H atom. The water molecule links the cation–anion ribbon structures into a three‐dimensional framework. In (III), the repeating molecular unit comprises a benzene‐1,4‐dicarboxylate dianion which lies across a crystallographic inversion centre, two guanidinium cations and two solvent water molecules (each set related by twofold rotational symmetry), and a single water molecule which lies on a twofold axis. Each guanidinium cation forms three types of cyclic interaction with the dianions: one R₂¹(6), the others R₃²(8) and R₃³(10) (both of these involving the water molecules), giving a three‐dimensional structure through bridges down the b‐cell direction. The water molecule at the general site also forms an unusual cyclic R₂²(4) homodimeric association across an inversion centre [O...O = 2.875 (2) Å]. The work described here provides further examples of the common cyclic guanidinium–carboxylate hydrogen‐bonding associations, as well as featuring other less common cyclic motifs.     

Two threefold interpenetrated two‐dimensional frameworks based on a flexible imidazole‐containing ligand and benzene‐1,4‐dicarboxylate

The open‐chain polyether‐bridged flexible ligand 1,2‐bis[2‐(1H‐1,3‐imidazol‐1‐ylmethyl)phenoxy]ethane (L) has been used to create two two‐dimensional coordination polymers under hydrothermal reaction of L with Cd^II or Co^II, in the presence of benzene‐1,4‐dicarboxylic acid (H₂bdc). In poly[[(μ₂‐benzene‐1,4‐dicarboxylato){μ‐1,2‐bis[2‐(1H‐1,3‐imidazol‐1‐ylmethyl)phenoxy]ethane}cadmium(II)] dihydrate], {[Cd(C₈H₄O₄)(C₂₂H₂₂N₄O₂)]·2H₂O}_n, (I), and the cobalt(II) analogue {[Co(C₈H₄O₄)(C₂₂H₂₂N₄O₂)]·2H₂O}_n, (II), the Cd^II and Co^II cations are six‐coordinated by four carboxylate O atoms from two different bdc²⁻ dianions in a chelating mode and two N atoms from two distinct L ligands. The metal ions, bdc²⁻ dianions and L ligands each sit across crystallographic twofold axes. The bdc²⁻ coordination mode and the coordinating orientation of the L ligand play an important role in constructing the novel two‐dimensional framework. Complexes (I) and (II) are threefold interpenetrated two‐dimensional frameworks; their structures are almost isomorphous, while the bond lengths, angles and hydrogen bonds are different in (I) and (II).     

Multicomponent crystals of erlotinib

Erlotinib [systematic name: N‐(3‐ethynylphenyl)‐6,7‐bis(2‐methoxyethoxy)quinazolin‐4‐amine], a small‐molecule epidermal growth factor receptor inhibitor, useful for the treatment of non‐small‐cell lung cancer, has been crystallized as erlotinib monohydrate, C₂₂H₂₃N₃O₄·H₂O, (I), the erlotinib hemioxalate salt [systematic name: 4‐amino‐N‐(3‐ethynylphenyl)‐6,7‐bis(2‐methoxyethoxy)quinazolin‐1‐ium hemioxalate], C₂₂H₂₄N₃O₄⁺·0.5C₂O₄²⁻, (II), and the cocrystal erlotinib fumaric acid hemisolvate dihydrate, C₂₂H₂₃N₃O₄·0.5C₄H₄O₄·2H₂O, (III). In (II) and (III), the oxalate anion and the fumaric acid molecule are located across inversion centres. The water molecules in (I) and (III) play an active role in hydrogen‐bonding interactions which lead to the formation of tetrameric and hexameric hydrogen‐bonded networks, while in (II) the cations and anions form a tetrameric hydrogen‐bonded network in the crystal packing. The title multicomponent crystals of erlotinib have been elucidated to study the assembly of molecules through intermolecular interactions, such as hydrogen bonds and aromatic π–π stacking.     

2,6‐Diamino‐9H‐purine monohydrate and bis(2,6‐diamino‐9H‐purin‐1‐ium) 2‐(2‐carboxylatophenyl)acetate heptahydrate: two simple structures with very complex hydrogen‐bonding schemes

Two structures presenting an uncomplexed 2,6‐diaminopurine (dap) group are reported, namely 2,6‐diamino‐9H‐purine monohydrate, C₅H₆N₆·H₂O, (I), and bis(2,6‐diamino‐9H‐purin‐1‐ium) 2‐(2‐carboxylatophenyl)acetate heptahydrate, 2C₅H₇N₆⁺·C₉H₆O₄²⁻·7H₂O, (II). Both structures are rather featureless from a molecular point of view, but present instead an outstanding hydrogen‐bonding scheme. In compound (I), this is achieved through a rather simple independent unit content (one neutral dap and one water molecule) and takes the form of two‐dimensional layers tightly connected by strong hydrogen bonds, and interlinked by much weaker hydrogen bonds and π–π interactions. In compound (II), the fundamental building blocks are more complex, consisting of two independent 2,6‐diamino‐9H‐purin‐1‐ium (Hdap⁺) cations, one homophthalate [2‐(2‐carboxylatophenyl)acetate] dianion and seven solvent water molecules. The large number of hydrogen‐bond donors and acceptors produces 26 independent interactions, leading to an extended and complicated network of hydrogen bonds in a packing organization characterized by the stacking of interleaved anionic and cationic planar arrays. These structural characteristics are compared with those of similar compounds in the literature.