Decanedioic Acid (C10H18O4)/Dodecanedioic Acid (C12H22O4) System: Polymorphism of the Components and Experimental Phase Diagram

The experimental temperature/composition phase diagram of the binary system decanedioic acid (C₁₀H₁₈O₄)/dodecanedioic acid (C₁₂H₂₂O₄) was established by combining X‐ray powder diffraction (XRD), differential‐scanning calorimetry (DSC), infrared spectroscopy (IR), scanning electron microscopy (SEM), and thermo‐optical microscopy (TOM). Both compounds crystallize in the same ordered form, C (P2₁/c), which is the phase that melts in both cases. The C form melts in C₁₂H₂₂O₄ earlier than in C₁₀H₁₈O₄, in contrast to other unbranched‐chain compounds (alkanes, alkanols, and alkanoic acids) in which the melting temperatures increase as the C‐atom number rises. Contrary to what might be expected, total solid‐state miscibility is not observed. The C₁₀H₁₈O₄/C₁₂H₂₂O₄ binary system shows a complex phase diagram. At low temperatures, a new monoclinic form, C_i (P2₁/c), stabilizes as a result of the disorder of composition in the mixed samples; two [C+C_i] domains appear. Upon heating, four solid–solid and seven solid–liquid domains appear related by eutectic and peritectic invariants. All the crystallographic forms observed are isostructural.     

Covalent‐assisted supramolecular synthesis: the effect of hydrogen bonding in cocrystals of 4‐tert‐butylbenzoic acid with isoniazid and its derivatized forms

A series of cocrystals of isoniazid and four of its derivatives have been produced with the cocrystal former 4‐tert‐butylbenzoic acid via a one‐pot covalent and supramolecular synthesis, namely 4‐tert‐butylbenzoic acid–isoniazid, C₆H₇N₃O·C₁₁H₁₄O₂, 4‐tert‐butylbenzoic acid–N′‐(propan‐2‐ylidene)isonicotinohydrazide, C₉H₁₁N₃O·C₁₁H₁₄O₂, 4‐tert‐butylbenzoic acid–N′‐(butan‐2‐ylidene)isonicotinohydrazide, C₁₀H₁₃N₃O·C₁₁H₁₄O₂, 4‐tert‐butylbenzoic acid–N′‐(diphenylmethylidene)isonicotinohydrazide, C₁₉H₁₅N₃O·C₁₁H₁₄O₂, and 4‐tert‐butylbenzoic acid–N′‐(4‐hydroxy‐4‐methylpentan‐2‐ylidene)isonicotinohydrazide, C₁₂H₁₇N₃O₂·C₁₁H₁₄O₂. The co‐former falls under the classification of a `generally regarded as safe' compound. The four derivatizing ketones used are propan‐2‐one, butan‐2‐one, benzophenone and 3‐hydroxy‐3‐methylbutan‐2‐one. Hydrogen bonds involving the carboxylic acid occur consistently with the pyridine ring N atom of the isoniazid and all of its derivatives. The remaining hydrogen‐bonding sites on the isoniazid backbone vary based on the steric influences of the derivative group. These are contrasted in each of the molecular systems.     

The design of novel metronidazole benzoate structures: exploring stoichiometric diversity

The use of supramolecular synthons as a strategy to control crystalline structure is a crucial factor in developing new solid forms with physicochemical properties optimized by design. However, to achieve this objective, it is necessary to understand the intermolecular interactions in the context of crystal packing. The feasibility of a given synthon depends on its flexibility to combine the drug with a variety of coformers. In the present work, the imidazole–hydroxy synthon is investigated using as the target molecule benzoylmetronidazole [BZMD; systematic name 2‐(2‐methyl‐5‐nitro‐1H‐imidazol‐1‐yl)ethyl benzoate], whose imidazole group seems to be a suitable acceptor for hydrogen bonds. Thus, coformers with carboxylic acid and phenol groups were chosen. According to the availability of binding sites presented in the coformer, and considering the proposed synthon and hydrogen‐bond complementarity as major factors, different drug–coformer stoichiometric ratios were explored (1:1, 2:1 and 3:1). Thirteen new solid forms (two salts and eleven cocrystals) were produced, namely BZMD–benzoic acid (1/1), C₁₃H₁₃N₃O₄·C₇H₆O₂, BZMD–β‐naphthol (1/1), C₁₃H₁₃N₃O₄·C₁₀H₈O, BZMD–4‐methoxybenzoic acid (1/1), C₁₃H₁₃N₃O₄·C₈H₈O₃, BZMD–3,5‐dinitrobenzoic acid (1/1), C₁₃H₁₃N₃O₄·C₇H₄N₂O₆, BZMD–3‐aminobenzoic acid (1/1), C₁₃H₁₃N₃O₄·C₇H₇NO₂, BZMD–salicylic acid (1/1), C₁₃H₁₃N₃O₄·C₇H₆O₃, BZMD–maleic acid (1/1) {as the salt 1‐[2‐(benzoyloxy)ethyl]‐2‐methyl‐5‐nitro‐1H‐imidazol‐3‐ium 3‐carboxyprop‐2‐enoate}, C₁₃H₁₄N₃O₄⁺·C₄H₃O₄^?, BZMD–isophthalic acid (1/1), C₁₃H₁₃N₃O₄·C₈H₆O4, BZMD–resorcinol (2/1), 2C₁₃H₁₃N₃O₄·C₆H₆O₂, BZMD–fumaric acid (2/1), C₁₃H₁₃N₃O₄·0.5C₄H₄O₄, BZMD–malonic acid (2/1), 2C₁₃H₁₃N₃O₄·C₃H₂O₄, BZMD–2,6‐dihydroxybenzoic acid (1/1) {as the salt 1‐[2‐(benzoyloxy)ethyl]‐2‐methyl‐5‐nitro‐1H‐imidazol‐3‐ium 2,6‐dihydroxybenzoate}, C₁₃H₁₄N₃O₄⁺·C₇H₅O₄^?, and BZMD–3,5‐dihydroxybenzoic acid (3/1), 3C₁₃H₁₃N₃O₄·C₇H₆O₄, and their crystalline structures elucidated, confirming the robustness of the selected synthon.     

Favoured conformations of methyl isopropyl,ethyl isopropyl,methyl tert‐butyl,and ethyl tert‐butyl 2‐(triphenylphosphoranylidene)malonate

The conformations of organic compounds determined in the solid state are important because they can be compared with those in solution and/or from theoretical calculations. In this work, the crystal and molecular structures of four closely related diesters, namely methyl isopropyl 2‐(triphenylphosphoranylidene)malonate, C₂₅H₂₅O₄P, ethyl isopropyl 2‐(triphenylphosphoranylidene)malonate, C₂₆H₂₇O₄P, methyl tert‐butyl 2‐(triphenylphosphoranylidene)malonate, C₂₆H₂₇O₄P, and ethyl tert‐butyl 2‐(triphenylphosphoranylidene)malonate, C₂₇H₂₉O₄P, have been analysed as a preliminary step for such comparative studies. As a result of extensive electronic delocalization, as well as intra‐ and intermolecular interactions, a remarkably similar pattern of preferred conformations in the crystal structures results, viz. a syn–anti conformation of the acyl groups with respect to the P atom, with the bulkier alkoxy groups oriented towards the P atom. The crystal structures are controlled by nonconventional hydrogen‐bonding and intramolecular interactions between cationoid P and acyl and alkoxy O atoms in syn positions.     

Synthesis and characterization of a cadmium(II)–organic supramolecular coordination compound based on the multifunctional 2‐amino‐5‐sulfobenzoic acid ligand

Much attention has been paid by chemists to the construction of supramolecular coordination compounds based on the multifunctional ligand 5‐sulfosalicylic acid (H₃SSA) due to the structural and biological interest of these compounds. However, no coordination compounds have been reported for the multifunctional amino‐substituted sulfobenzoate ligand 2‐amino‐5‐sulfobenzoic acid (H₂asba). We expected that H₂asba could be a suitable building block for the assembly of supramolecular networks due to its interesting structural characteristics. The reaction of cadmium(II) nitrate with H₂asba in the presence of the auxiliary flexible dipyridylamide ligand N,N′‐bis[(pyridin‐4‐yl)methyl]oxamide (4bpme) under ambient conditions formed a new mixed‐ligand coordination compound, namely bis(3‐amino‐4‐carboxybenzenesulfonato‐κO¹)diaquabis{N,N′‐bis[(pyridin‐4‐yl)methyl]oxamide‐κN}cadmium(II)–N,N′‐bis[(pyridin‐4‐yl)methyl]oxamide–water (1/1/4), [Cd(C₇H₆NO₅S)₂(C₁₄H₁₄N₄O₂)₂(H₂O)₂]·C₁₄H₁₄N₄O₂·4H₂O, (1), which was characterized by single‐crystal and powder X‐ray diffraction analysis (PXRD), FT–IR spectroscopy, thermogravimetric analysis (TG), and UV–Vis and photoluminescence spectroscopic analyses in the solid state. The central Cd^II atom in (1) occupies a special position on a centre of inversion and exhibits a slightly distorted octahedral geometry, being coordinated by two N atoms from two monodentate 4bpme ligands, four O atoms from two monodentate 4‐amino‐3‐carboxybenzenesulfonate (Hasba⁻) ligands and two coordinated water molecules. Interestingly, complex (1) further extends into a threefold polycatenated 0D→2D (0D is zero‐dimensional and 2D is two‐dimensional) interpenetrated supramolecular two‐dimensional (4,4) layer through intermolecular hydrogen bonding. The interlayer hydrogen bonding further links adjacent threefold polycatenated two‐dimensional layers into a three‐dimensional network. The optical properties of complex (1) indicate that it may be used as a potential indirect band gap semiconductor material. Complex (1) exhibits an irreversible dehydration–rehydration behaviour. The fluorescence properties have also been investigated in the solid state at room temperature.     

Zirconium Complexes of Two Different Iminopyrrolyl Ligands – Syntheses and Structures

The reaction involving N‐aryliminopyrrolyl ligand, 2‐((p‐Me‐C₆H₃N=CMe)–C₄H₃NH) ( 1a ) (Imp^Me‐H), and Zr(OtBu)₄ in a 2:1 molar ratio in toluene at 90 °C afforded the corresponding bis(iminopyrrolyl) complex of zirconium, [(Imp^Me)₂Zr(OtBu)₂] ( 2a ) having two bidentate iminopyrrole groups in the coordination sphere. In contrast, the bulkier 2‐((2,6‐iPr₂C₆H₃N=CH)–C₄H₃NH) ( 1b ) (Imp^Dipp‐H) and Zr(OtBu)₄ in a 1:1 molar ratio under the same condition yielded the corresponding mono(iminopyrrolyl) complex of zirconium, [(Imp^Dipp)Zr(OtBu)₃(THF)] ( 2b ), which contains only one bidentate iminopyrrole moiety in the coordination sphere. Both complexes were characterized by single‐crystal X‐ray diffraction analysis. The solid‐state structures reveal that the bulky iminopyrrole ligands cause a steric crowding around the zirconium ion along with three tert‐butoxide ligands attached to the central metal atom.     

Structures of rhenium(I) complexes with 3‐hydroxyflavone and benzhydroxamic acid as O,O′‐bidentate ligands and confirmation of π‐stacking by solid‐state NMR spectroscopy

The synthesis and crystal structures of two new rhenium(I) complexes obtained utilizing benzhydroxamic acid (BHAH) and 3‐hydroxyflavone (2‐phenylchromen‐4‐one, FlavH) as bidentate ligands, namely tetraethylammonium fac‐(benzhydroxamato‐κ²O,O′)bromidotricarbonylrhenate(I), (C₈H₂₀N)[ReBr(C₇H₆NO₂)(CO)₃], 1 , and fac‐aquatricarbonyl(4‐oxo‐2‐phenylchromen‐3‐olato‐κ²O,O′)rhenium(I)–3‐hydroxyflavone (1/1), [Re(C₁₅H₉O₃)(CO)₃(H₂O)]·C₁₅H₁₀O₃, 3 , are reported. Furthermore, the crystal structure of free 3‐hydroxyflavone, C₁₅H₁₀O₃, 4 , was redetermined at 100 K in order to compare the packing trends and solid‐state NMR spectroscopy with that of the solvate flavone molecule in 3 . The compounds were characterized in solution by ¹H and ¹³C NMR spectroscopy, and in the solid state by ¹³C NMR spectroscopy using the cross‐polarization magic angle spinning (CP/MAS) technique. Compounds 1 and 3 both crystallize in the triclinic space group P with one molecule in the asymmetric unit, while 4 crystallizes in the orthorhombic space group P2₁2₁2₁. Molecules of 1 and 3 generate one‐dimensional chains formed through intermolecular interactions. A comparison of the coordinated 3‐hydroxyflavone ligand with the uncoordinated solvate molecule and free molecule 4 shows that the last two are virtually completely planar due to hydrogen‐bonding interactions, as opposed to the former, which is able to rotate more freely. The differences between the solid‐ and solution‐state ¹³C NMR spectra of 3 and 4 are ascribed to inter‐ and intramolecular interactions. The study also investigated the potential labelling of both bidentate ligands with the corresponding fac‐^99mTc‐tricarbonyl synthon. All attempts were unsuccessful and reasons for this are provided.     

A mixed crystal of imperatorin and phellopterin,with C—H...O,C—H...π and π–π interactions

The crystal structure of 9‐(3‐methyl­but‐2‐enyl­oxy)­‐7H‐furo­[3,2‐g]­chro­men‐7‐one–4‐methoxy‐9‐(3‐methyl­but‐2‐enyl­oxy)‐7H‐­furo­[3,2‐g]­chromen‐7‐one (0.926/0.074), 0.926C₁₆H₁₄O₄·0.074C₁₇H₁₆O₅, is characterized by two independent imperatorin mol­ecules in the asymmetric unit, which exhibit different side‐chain conformations. A small amount of phellopterin overlaps with one of the two imperatorin mol­ecules. The supramol­ecular structure is supported by C—H...O, C—H...π and π–π interactions.     

Preparation,characterization and luminescence‐sensing properties of two ZnII MOFs with mixed 5‐amino‐2,4,6‐tribromoisophthalic acid and bipyridyl‐type ligands

The bromo‐substituted aromatic dicarboxylic acid 5‐amino‐2,4,6‐tribromoisophthalic acid (H₂ATBIP), in the presence of the N‐donor flexible bipyridyl‐type ligands 1,3‐bis(pyridin‐4‐yl)propane (bpp) and N,N′‐bis(pyridin‐4‐ylmethyl)oxalamide (4‐bpme) and Zn^II ions, was used as an O‐donor ligand to assemble two novel luminescent metal–organic frameworks (MOFs), namely poly[[(μ‐5‐amino‐2,4,6‐tribromoisophthalato‐κ²O¹:O³)[μ‐1,3‐bis(pyridin‐4‐yl)propane‐κ²N:N′]zinc(II)] dimethylformamide monosolvate], {[Zn(C₈H₂Br₃NO₄)(C₁₃H₁₄N₂)]·C₃H₇NO}_n, ( 1 ), and poly[[(μ‐5‐amino‐2,4,6‐tribromoisophthalato‐κ²O¹:O³)diaqua[μ‐N,N′‐bis(pyridin‐4‐ylmethyl)oxalamide‐κ²N:N′]zinc(II)] monohydrate], {[Zn(C₈H₂Br₃NO₄)(C₁₄H₁₄N₄O₂)(H₂O)₂]·H₂O}_n, ( 2 ), using the solution evaporation method. Both ( 1 ) and ( 2 ) were characterized by FT–IR spectroscopy, elemental analysis (EA), solid‐state diffuse‐reflectance UV–Vis spectroscopy, and powder and single‐crystal X‐ray diffraction analysis. Complex ( 1 ) shows a two‐dimensional (2D) corrugated layer simplified as a 2D (4,4) topological network. The supramolecular interactions (π–π stacking, hydrogen bonding and C—Br…Br halogen bonding) play significant roles in the formation of an extended three‐dimensional (3D) supramolecular network of ( 1 ). Complex ( 2 ) crystallizes in the chiral space group P2₁2₁2₁ and exhibits a novel 3D homochiral framework, showing a diamond‐like topology with Schläfli symbol 6⁶. The homochirality of ( 2 ) is further confirmed by the solid‐state circular dichroism (CD) spectrum. The second harmonic generation (SHG) property of ( 2 ) was also investigated. The hydrogen and C—Br…Br/O halogen bonding further stabilize the framework of ( 2 ). The central Zn^II ions in ( 1 ) and ( 2 ) show tetrahedral and octahedral coordination geometries, respectively. The coordinated and uncoordinated water molecules in ( 2 ) could be removed selectively upon heating. Most importantly, ( 1 ) and ( 2 ) show rapid and highly sensitive sensing for a large pool of nitroaromatic explosives (NAEs).     

The role of π–π stacking and hydrogen‐bonding interactions in the assembly of a series of isostructural group IIB coordination compounds

The supramolecular chemistry of coordination compounds has become an important research domain of modern inorganic chemistry. Herein, six isostructural group IIB coordination compounds containing a 2‐{[(2‐methoxyphenyl)imino]methyl}phenol ligand, namely dichloridobis(2‐{(E)‐[(2‐methoxyphenyl)azaniumylidene]methyl}phenolato‐κO)zinc(II), [ZnCl₂(C₂₈H₂₆N₂O₄)], 1 , diiodidobis(2‐{(E)‐[(2‐methoxyphenyl)azaniumylidene]methyl}phenolato‐κO)zinc(II), [ZnI₂(C₂₈H₂₆N₂O₄)], 2 , dibromidobis(2‐{(E)‐[(2‐methoxyphenyl)azaniumylidene]methyl}phenolato‐κO)cadmium(II), [CdBr₂(C₂₈H₂₆N₂O₄)], 3 , diiodidobis(2‐{(E)‐[(2‐methoxyphenyl)azaniumylidene]methyl}phenolato‐κO)cadmium(II), [CdI₂(C₂₈H₂₆N₂O₄)], 4 , dichloridobis(2‐{(E)‐[(2‐methoxyphenyl)azaniumylidene]methyl}phenolato‐κO)mercury(II), [HgCl₂(C₂₈H₂₆N₂O₄)], 5 , and diiodidobis(2‐{(E)‐[(2‐methoxyphenyl)azaniumylidene]methyl}phenolato‐κO)mercury(II), [HgI₂(C₂₈H₂₆N₂O₄)], 6 , were synthesized and characterized by X‐ray crystallography and spectroscopic techniques. All six compounds exhibit an infinite one‐dimensional ladder in the solid state governed by the formation of hydrogen‐bonding and π–π stacking interactions. The crystal structures of these compounds were studied using geometrical and Hirshfeld surface analyses. They have also been studied using M06‐2X/def2‐TZVP calculations and Bader's theory of `atoms in molecules'. The energies associated with the interactions, including the contribution of the different forces, have been evaluated. In general, the π–π stacking interactions are stronger than those reported for conventional π–π complexes, which is attributed to the influence of the metal coordination, which is stronger for Zn than either Cd or Hg. The results reported herein might be useful for understanding the solid‐state architecture of metal‐containing materials that contain M^IIX₂ subunits and aromatic organic ligands.     

One barbiturate and two solvated thiobarbiturates containing the triply hydrogen‐bonded ADA/DAD synthon,plus one ansolvate and three solvates of their coformer 2,4‐diaminopyrimidine

A path to new synthons for application in crystal engineering is the replacement of a strong hydrogen‐bond acceptor, like a C=O group, with a weaker acceptor, like a C=S group, in doubly or triply hydrogen‐bonded synthons. For instance, if the C=O group at the 2‐position of barbituric acid is changed into a C=S group, 2‐thiobarbituric acid is obtained. Each of the compounds comprises two ADA hydrogen‐bonding sites (D = donor and A = acceptor). We report the results of cocrystallization experiments of barbituric acid and 2‐thiobarbituric acid, respectively, with 2,4‐diaminopyrimidine, which contains a complementary DAD hydrogen‐bonding site and is therefore capable of forming an ADA/DAD synthon with barbituric acid and 2‐thiobarbituric acid. In addition, pure 2,4‐diaminopyrimidine was crystallized in order to study its preferred hydrogen‐bonding motifs. The experiments yielded one ansolvate of 2,4‐diaminopyrimidine (pyrimidine‐2,4‐diamine, DAPY), C₄H₆N₄, (I), three solvates of DAPY, namely 2,4‐diaminopyrimidine–1,4‐dioxane (2/1), 2C₄H₆N₄·C₄H₈O₂, (II), 2,4‐diaminopyrimidine–N,N‐dimethylacetamide (1/1), C₄H₆N₄·C₄H₉NO, (III), and 2,4‐diaminopyrimidine–1‐methylpyrrolidin‐2‐one (1/1), C₄H₆N₄·C₅H₉NO, (IV), one salt of barbituric acid, viz. 2,4‐diaminopyrimidinium barbiturate (barbiturate is 2,4,6‐trioxopyrimidin‐5‐ide), C₄H₇N₄⁺·C₄H₃N₂O₃⁻, (V), and two solvated salts of 2‐thiobarbituric acid, viz. 2,4‐diaminopyrimidinium 2‐thiobarbiturate–N,N‐dimethylformamide (1/2) (2‐thiobarbiturate is 4,6‐dioxo‐2‐sulfanylidenepyrimidin‐5‐ide), C₄H₇N₄⁺·C₄H₃N₂O₂S⁻·2C₃H₇NO, (VI), and 2,4‐diaminopyrimidinium 2‐thiobarbiturate–N,N‐dimethylacetamide (1/2), C₄H₇N₄⁺·C₄H₃N₂O₂S⁻·2C₄H₉NO, (VII). The ADA/DAD synthon was succesfully formed in the salt of barbituric acid, i.e. (V), as well as in the salts of 2‐thiobarbituric acid, i.e. (VI) and (VII). In the crystal structures of 2,4‐diaminopyrimidine, i.e. (I)–(IV), R₂²(8) N—H…N hydrogen‐bond motifs are preferred and, in two structures, additional R₃²(8) patterns were observed.     

The relationship between Hirshfeld potential and cytotoxic activity: a study along a series of flavonoid and chromanone derivatives

The present study examines a series of six biologically‐active flavonoid and chromanone derivatives by X‐ray crystal structure analysis: (E)‐3‐benzylidene‐2‐phenylchroman‐4‐one, C₂₂H₁₆O₂, I , (E)‐3‐(4‐methylbenzylidene)‐2‐phenylchroman‐4‐one, C₂₃H₁₈O₂, II , (E)‐3‐(3‐methylbenzylidene)‐2‐phenylchroman‐4‐one, C₂₃H₁₈O₂, III , (E)‐3‐(4‐methoxybenzylidene)‐2‐phenylchroman‐4‐one, C₂₃H₁₈O₃, IV , (E)‐3‐benzylidenechroman‐4‐one, C₁₆H₁₂O₂, V , and (E)‐3‐(4‐methoxybenzylidene)chroman‐4‐one, C₁₇H₁₄O₃, VI . The cytotoxic activities of the presented crystal structures have been determined, together with their intermolecular interaction preferences and Hirshfeld surface characteristics. An inverse relationship was found between the contribution of C…C close contacts to the Hirshfeld surface and cytotoxic activity against the WM‐115 cancer line. Dependence was also observed between the logP value and the percentage contribution of C…H contacts to the Hirshfeld surface.     

Synthesis,structure and characterization of two new metal–organic coordination polymers based on the ligand 5‐iodobenzene‐1,3‐dicarboxylate

Two new coordination polymers (CPs) formed from 5‐iodobenzene‐1,3‐dicarboxylic acid (H₂iip) in the presence of the flexible 1,4‐bis(1H‐imidazol‐1‐yl)butane (bimb) auxiliary ligand, namely poly[[μ₂‐1,4‐bis(1H‐imidazol‐1‐yl)butane‐κ²N³:N^3′](μ₃‐5‐iodobenzene‐1,3‐dicarboxylato‐κ⁴O¹,O^1′:O³:O^3′)cobalt(II)], [Co(C₈H₃IO₄)(C₁₀H₁₄N₄)]_n or [Co(iip)(bimb)]_n, (1), and poly[[[μ₂‐1,4‐bis(1H‐imidazol‐1‐yl)butane‐κ²N³:N^3′](μ₂‐5‐iodobenzene‐1,3‐dicarboxylato‐κ²O¹:O³)zinc(II)] trihydrate], {[Zn(C₈H₃IO₄)(C₁₀H₁₄N₄)]·3H₂O}_n or {[Zn(iip)(bimb)]·3H₂O}_n, (2), were synthesized and characterized by FT–IR spectroscopy, thermogravimetric analysis (TGA), solid‐state UV–Vis spectroscopy, single‐crystal X‐ray diffraction analysis and powder X‐ray diffraction analysis (PXRD). The iip²⁻ ligand in (1) adopts the (κ¹,κ¹‐μ₂)(κ¹, κ¹‐μ₁)‐μ₃ coordination mode, linking adjacent secondary building units into a ladder‐like chain. These chains are further connected by the flexible bimb ligand in a trans–trans–trans conformation. As a result, a twofold three‐dimensional interpenetrating α‐Po network is formed. Complex (2) exhibits a two‐dimensional (4,4) topological network architecture in which the iip²⁻ ligand shows the (κ¹)(κ¹)‐μ₂ coordination mode. The solid‐state UV–Vis spectra of (1) and (2) were investigated, together with the fluorescence properties of (2) in the solid state.     

(E)‐4‐[2‐(3,4,5‐Trimethoxyphenyl)ethenyl]nitrobenzene and its `bridge‐flipped' analogues

The solid‐state structures of three push–pull acceptor‐π‐donor (A‐π‐D) systems differing only in the nature of the π‐spacer have been determined. (E)‐1‐Nitro‐4‐[2‐(3,4,5‐trimethoxyphenyl)ethenyl]benzene, C₁₇H₁₇NO₅, (I), and its `bridge‐flipped' imine analogues, (E)‐3,4,5‐trimethoxy‐N‐(4‐nitrobenzylidene)aniline, C₁₆H₁₆N₂O₅, (II), and (E)‐4‐nitro‐N‐(3,4,5‐trimethoxybenzylidene)aniline, C₁₆H₁₆N₂O₅, (III), display different kinds of supramolecular networks, viz. corrugated planes, a herringbone pattern and a layered structure, respectively, all with zero overall dipole moments. Only (III) crystallizes in a noncentrosymmetric space group (P2₁2₁2₁) and is, therefore, a potential material for second‐harmonic generation (SHG).     

Supramolecular hydrogen‐bonding patterns in salts of the antifolate drugs trimethoprim and pyrimethamine

Nine salts of the antifolate drugs trimethoprim and pyrimethamine, namely, trimethoprimium [or 2,4‐diamino‐5‐(3,4,5‐trimethoxybenzyl)pyrimidin‐1‐ium] 2,5‐dichlorothiophene‐3‐carboxylate monohydrate (TMPDCTPC, 1:1), C₁₄H₁₉N₄O₃⁺·C₅HCl₂O₂S⁻, ( I ), trimethoprimium 3‐bromothiophene‐2‐carboxylate monohydrate, (TMPBTPC, 1:1:1), C₁₄H₁₉N₄O₃⁺·C₅H₂BrO₂S⁻·H₂O, ( II ), trimethoprimium 3‐chlorothiophene‐2‐carboxylate monohydrate (TMPCTPC, 1:1:1), C₁₄H₁₉N₄O₃⁺·C₅H₂ClO₂S⁻·H₂O, ( III ), trimethoprimium 5‐methylthiophene‐2‐carboxylate monohydrate (TMPMTPC, 1:1:1), C₁₄H₁₉N₄O₃⁺·C₆H₅O₂S⁻·H₂O, ( IV ), trimethoprimium anthracene‐9‐carboxylate sesquihydrate (TMPAC, 2:2:3), C₁₄H₁₉N₄O₃⁺·C₁₅H₉O₂⁻·1.5H₂O, ( V ), pyrimethaminium [or 2,4‐diamino‐5‐(4‐chlorophenyl)‐6‐ethylpyrimidin‐1‐ium] 2,5‐dichlorothiophene‐3‐carboxylate (PMNDCTPC, 1:1), C₁₂H₁₄ClN₄⁺·C₅HCl₂O₂S⁻, ( VI ), pyrimethaminium 5‐bromothiophene‐2‐carboxylate (PMNBTPC, 1:1), C₁₂H₁₄ClN₄⁺·C₅H₂BrO₂S⁻, ( VII ), pyrimethaminium anthracene‐9‐carboxylate ethanol monosolvate monohydrate (PMNAC, 1:1:1:1), C₁₂H₁₄ClN₄⁺·C₁₅H₉O₂⁻·C₂H₅OH·H₂O, ( VIII ), and bis(pyrimethaminium) naphthalene‐1,5‐disulfonate (PMNNSA, 2:1), 2C₁₂H₁₄ClN₄⁺·C₁₀H₆O₆S₂²⁻, ( IX ), have been prepared and characterized by single‐crystal X‐ray diffraction. In all the crystal structures, the pyrimidine N1 atom is protonated. In salts ( I )–( III ) and ( VI )–( IX ), the 2‐aminopyrimidinium cation interacts with the corresponding anion via a pair of N—H…O hydrogen bonds, generating the robust R₂²(8) supramolecular heterosynthon. In salt ( IV ), instead of forming the R₂²(8) heterosynthon, the carboxylate group bridges two pyrimidinium cations via N—H…O hydrogen bonds. In salt ( V ), one of the carboxylate O atoms bridges the N1—H group and a 2‐amino H atom of the pyrimidinium cation to form a smaller R₂¹(6) ring instead of the R₂²(8) ring. In salt ( IX ), the sulfonate O atoms mimic the role of carboxylate O atoms in forming an R₂²(8) ring motif. In salts ( II )–( IX ), the pyrimidinium cation forms base pairs via a pair of N—H…N hydrogen bonds, generating a ring motif [R₂²(8) homosynthon]. Compounds ( II ) and ( III ) are isomorphous. The quadruple DDAA (D = hydrogen‐bond donor and A = hydrogen‐bond acceptor) array is observed in ( I ). In salts ( II )–( IV ) and ( VI )–( IX ), quadruple DADA arrays are present. In salts ( VI ) and ( VII ), both DADA and DDAA arrays co‐exist. The crystal structures are further stabilized by π–π stacking interactions [in ( I ), ( V ) and ( VII )–( IX )], C—H…π interactions [in ( IV )–( V ) and ( VII )–( IX )], C—Br…π interactions [in ( II )] and C—Cl…π interactions [in ( I ), ( III ) and ( VI )]. Cl…O and Cl…Cl halogen‐bond interactions are present in ( I ) and ( VI ), with distances and angles of 3.0020 (18) and 3.5159 (16) Å, and 165.56 (10) and 154.81 (11)°, respectively.     

Temperature‐induced pseudopolymorphism of molecular salts from a pyridyl bis‐urea macrocycle and naphthalene‐1,5‐disulfonic acid

Molecular salts, often observed as cocrystals, play an important role in the fields of pharmaceutics and materials science, where salt formation is used to tune the properties of active pharmaceutical ingredients (APIs) and improve the stability of solid‐state materials. Salt formation via a proton‐transfer reaction typically alters hydrogen‐bonding motifs and influences supramolecular assembly patterns. We report here the molecular salts formed by the pyridyl bis‐urea macrocycle 3,5,13,15,21,22‐hexaazatricyclo[15.3.1.1^7,11]docosa‐1(21),7(22),8,10,17,19‐hexaene‐4,14‐dione, ( 1 ), and naphthalene‐1,5‐disulfonic acid (H₂NDS) as two salt cocrystal solvates, namely 4,14‐dioxo‐3,5,13,15,21,22‐hexaazatricyclo[15.3.1.1^7,11]docosa‐1(21),7(22),8,10,17,19‐hexaene‐21,22‐diium naphthalene‐1,5‐disulfonate dimethyl sulfoxide disolvate, C₁₆H₂₀N₆O₂²⁺·C₁₀H₆O₆S₂²⁻·2C₂H₆OS, ( 2 ), and the corresponding monosolvate, C₁₆H₂₀N₆O₂²⁺·C₁₀H₆O₆S₂²⁻·C₂H₆OS, ( 3 ). This follows the ΔpK_a rule such that there is a proton transfer from H₂NDS to ( 1 ), forming the reported molecular salts through hydrogen bonding. Prior to salt formation, ( 1 ) is relatively planar and assembles into columnar structures. The salt cocrystal solvates were obtained upon slow cooling of dimethyl sulfoxide–acetonitrile solutions of the molecular components from two temperatures (363 and 393 K). The proton transfer to ( 1 ) significantly alters the conformation of the macrocycle, changing the formerly planar macrocycle into a step‐shaped conformation with trans–cis urea groups in ( 2 ) or into a bowl‐shape conformation with trans–trans urea groups in ( 3 ).     

Hydrogen‐bonded one‐dimensional networks in 1:1 complexes of N,N′‐bis(2‐pyridyl)aryldiamines with anilic acid

The 1:1 complexes N,N′‐bis(2‐pyridyl)­benzene‐1,4‐di­amine–anilic acid (2,5‐di­hydroxy‐1,4‐benzo­quinone) (1/1), C₁₆H₁₄N₄·C₆H₄O₄, (I), and N,N′‐bis(2‐pyridyl)­bi­phenyl‐4,4′‐di­amine–anilic acid (1/1), C₂₂H₁₈N₄·C₆H₄O₄, (II), have been prepared and their solid‐state structures investigated. The component mol­ecules of these complexes are connected via conventional N—H?O and O—H?N hydrogen bonds, leading to the formation of an infinite one‐dimensional network generated by the cyclic motif R(9). The anilic acid molecules in both crystal structures lie around inversion centres and the observed bond lengths are typical for the neutral mol­ecule. Nevertheless, the pyridine C—N—C angles [120.9 (2) and 120.13 (17)° for complexes (I) and (II), respectively] point to a partial H‐atom transfer from anilic aicd to the bispyridyl­amine, and hence to H‐atom disorder in the OHN bridge. The bispyridyl­amine mol­ecules of (I) and (II) also lie around inversion centres and exhibit disorder of their central phenyl rings over two positions.     

Alkyl levulinates as `green chemistry' precursors: butane‐1,4‐diyl bis(4‐oxopentanoate) and hexane‐1,6‐diyl bis(4‐oxopentanoate)

Levulinic acid derivatives are potential `green chemistry' renewably sourced molecules with utility in industrial coatings applications. Suitable single crystals of the centrosymmetric title compounds, C₁₄H₂₂O₆ and C₁₆H₂₆O₆, respectively, were obtained with difficulty. The data for the latter hexane‐1,6‐diyl compound were extracted from the major fragment of a three‐component twinned crystal. Both compounds crystallize in similar‐sized unit cells with identical symmetry, utilizing the same weak nonconventional attractive C—H...O(ketone) hydrogen bonds via C(4) and C(5) motifs, which expand to R²₂(30) ring and C²₂(14) chain motifs. Their different packing orientations in similar‐sized unit cells suggest that crystal growth involving packing mixes could lead to intergrowths or twins.     

Structural investigation of one‐ and two‐dimensional coordination polymers based on cobalt–bis(dioxolene) units and 1‐hydroxy‐1,2,4,5‐tetrakis(pyridin‐4‐yl)cyclohexane

The combination of cobalt, 3,5‐di‐tert‐butyldioxolene (3,5‐dbdiox) and 1‐hydroxy‐1,2,4,5‐tetrakis(pyridin‐4‐yl)cyclohexane (tpch) yields two coordination polymers with different connectivities, i.e. a one‐dimensional zigzag chain and a two‐dimensional sheet. Poly[[bis(3,5‐di‐tert‐butylbenzene‐1,2‐diolato)bis(1,5‐di‐tert‐butyl‐4‐oxocyclohexa‐2,5‐dien‐1‐yl‐3‐olato)[μ₄‐1‐hydroxy‐1,2,4,5‐tetrakis(pyridin‐4‐yl)cyclohexane]cobalt(III)]–ethanol–water 1/7/5], {[Co₂(C₁₄H₂₀O₂)₄(C₂₆H₂₄N₄O)]·7C₂H₅OH·5H₂O}_n or {[Co₂(3,5‐dbdiox)₄(tpch)}·7EtOH·5H₂O}_n, is the second structurally characterized example of a two‐dimensional coordination polymer based on linked {Co(3,5‐dbdiox)₂} units. Variable‐temperature single‐crystal X‐ray diffraction studies suggest that catena‐poly[[[(3,5‐di‐tert‐butylbenzene‐1,2‐diolato)(1,5‐di‐tert‐butyl‐4‐oxocyclohexa‐2,5‐dien‐1‐yl‐3‐olato)cobalt(III)]‐μ‐1‐hydroxy‐1,2,4,5‐tetrakis(pyridin‐4‐yl)cyclohexane]–ethanol–water (1/1/5)], {[Co(C₁₄H₂₀O₂)₂(C₂₆H₂₄N₄O)]·C₂H₅OH·5H₂O}_n or {[Co(3,5‐dbdiox)₂(tpch)]·EtOH·5H₂O}_n, undergoes a temperature‐induced valence tautomeric interconversion.