2‐[(E)‐(4‐Hydroxy‐3‐methoxybenzylidene)amino]‐N‐(2‐methylphenyl)‐4,5,6,7‐tetrahydro‐1‐benzothiophene‐3‐carboxamide

The title compound, C₂₄H₂₄N₂O₃S, exhibits antifungal and antibacterial properties. The compound crystallizes with two molecules in the asymmetric unit, with one molecule exhibiting `orientational disorder' in the crystal structure with respect to the cyclohexene ring. The o‐toluidine groups in both molecules are noncoplanar with the respective cyclohexene‐fused thiophene ring. In both molecules, there is an intramolecular N—H...N hydrogen bond forming a pseudo‐six‐membered ring which locks the molecular conformation and eliminates conformational flexibility. The crystal structure is stabilized by O—H...O hydrogen bonds; both molecules in the asymmetric unit form independent chains, each such chain consisting of alternating `ordered' and `disordered' molecules in the crystal lattice.     

Hydrogen bonding in meso‐4,5‐diphenyl‐3,6‐diaza­octane‐1,8‐diol: the formation of one‐dimensional linear chains of edge‐fused rings

The molecule of the title compound, C₁₈H₂₄N₂O₂, resides on a crystallographic inversion centre. The mol­ecule adopts a transoid conformation with respect to the central C—C single bond and is in the meso form. A polarimetric study of the compound did not show any optical activity, indicating that the compound is a racemic mixture entirely consistent with the centrosymmetric space group. In the mol­ecule, there is one intra­molecular N—H⋯O inter­action, resulting in the formation of a five‐membered ring. In the crystal structure, inter­molecular O—H⋯N and C—H⋯O inter­actions are also observed. These inter­actions form an R₂²(9) ring and one‐dimensional linear chains of edge‐fused rings running parallel to the [010] direction, which stabilize the crystal packing.     

The disordered molecular structure of (3aRS,7aRS)‐1,3‐dinitrosooctahydro‐1H‐benzimidazole

The title compound, C₇H₁₂N₄O₂, was obtained by nitrosation of the aminal cage (2R,7R,11S,16S)‐1,8,10,17‐tetraazapentacyclo[8.8.1.1^8,17.0^2,7.0^11,16]icosane. The crystal structure is a racemic mixture of RR and SS enantiomers. The asymmetric unit contains two crystallographically independent half‐molecules, one having two partially occupied conformers with refined occupancy factors of 0.747 (3) and 0.253 (3). The molecules sit across twofold axes. The unique molecules each form chains parallel to [001], with molecules connected by intermolecular C—H...O hydrogen bonds. The bonding between adjacent chains is weak. The analysis of eight different crystals confirmed the presence of disordered and nondisordered molecules in the same structure as a regular feature.     

On‐Surface Evolution of meso‐Isomerism in Two‐Dimensional Supramolecular Assemblies

Chiral structures created through the adsorption of molecules onto achiral surfaces play pivotal roles in many fields of science and engineering. Here, we present a systematic study of a novel chiral phenomenon on a surface in terms of organizational chirality, that is, meso‐isomerism, through coverage‐driven hierarchical polymorphic transitions of supramolecular assemblies of highly symmetric π‐conjugated molecules. Four coverage‐dependent phases of dehydrobenzo[12]annulene were uniformly fabricated on Ag(111), exhibiting unique chiral characteristics from the single‐molecule level to two‐dimensional supramolecular assemblies. All coverage‐driven phase transitions stem from adsorption‐induced pseudo‐diastereomerism, and our observation of a lemniscate‐type (∞) supramolecular configuration clearly reveals a drastic chiral phase transition from an enantiomeric chiral domain to a meso‐isomeric achiral domain. These findings provide new insights into controlling two‐dimensional chiral architectures on surfaces.     

N,N′‐Diethyl‐4‐nitrobenzene‐1,3‐diamine, 2,6‐bis(ethylamino)‐3‐nitrobenzonitrile and bis(4‐ethylamino‐3‐nitrophenyl) sulfone

N,N′‐Diethyl‐4‐nitrobenzene‐1,3‐diamine, C₁₀H₁₅N₃O₂, (I), crystallizes with two independent molecules in the asymmetric unit, both of which are nearly planar. The molecules differ in the conformation of the ethylamine group trans to the nitro group. Both molecules contain intramolecular N—H...O hydrogen bonds between the adjacent amine and nitro groups and are linked into one‐dimensional chains by intermolecular N—H...O hydrogen bonds. The chains are organized in layers parallel to (101) with separations of ca 3.4 Å between adjacent sheets. The packing is quite different from what was observed in isomeric 1,3‐bis(ethylamino)‐2‐nitrobenzene. 2,6‐Bis(ethylamino)‐3‐nitrobenzonitrile, C₁₁H₁₄N₄O₂, (II), differs from (I) only in the presence of the nitrile functionality between the two ethylamine groups. Compound (II) crystallizes with one unique molecule in the asymmetric unit. In contrast with (I), one of the ethylamine groups, which is disordered over two sites with occupancies of 0.75 and 0.25, is positioned so that the methyl group is directed out of the plane of the ring by approximately 85°. This ethylamine group forms an intramolecular N—H...O hydrogen bond with the adjacent nitro group. The packing in (II) is very different from that in (I). Molecules of (II) are linked by both intermolecular amine–nitro N—H...O and amine–nitrile N—H...N hydrogen bonds into a two‐dimensional network in the (10) plane. Alternating molecules are approximately orthogonal to one another, indicating that π–π interactions are not a significant factor in the packing. Bis(4‐ethylamino‐3‐nitrophenyl) sulfone, C₁₆H₁₈N₄O₆S, (III), contains the same ortho nitro/ethylamine pairing as in (I), with the position para to the nitro group occupied by the sulfone instead of a second ethylamine group. Each 4‐ethylamino‐3‐nitrobenzene moiety is nearly planar and contains the typical intramolecular N—H...O hydrogen bond. Due to the tetrahedral geometry about the S atom, the molecules of (III) adopt an overall V shape. There are no intermolecular amine–nitro hydrogen bonds. Rather, each amine H atom has a long (H...O ca 2.8 Å) interaction with one of the sulfone O atoms. Molecules of (III) are thus linked by amine–sulfone N—H...O hydrogen bonds into zigzag double chains running along [001]. Taken together, these structures demonstrate that small changes in the functionalization of ethylamine–nitroarenes cause significant differences in the intermolecular interactions and packing.     

meso–meso‐Linked Diarylamine‐Fused Porphyrin Dimers

A meso–meso‐linked diphenylamine‐fused porphyrin dimer and its methoxy‐substituted analogue were synthesized from a meso–meso‐linked porphyrin dimer by a reaction sequence involving Ir‐catalyzed β‐selective borylation, iodination, meso‐chlorination, and S_NAr reactions with diarylamines followed by electron‐transfer‐mediated intramolecular double C?H/C?I coupling. While these dimers commonly display characteristic split Soret bands and small oxidation potentials, they produced different products upon oxidation with tris(4‐bromophenyl)aminium hexachloroantimonate. Namely, the diphenylamine‐fused porphyrin dimer was converted into a dicationic closed‐shell quinonoidal dimer, while the methoxy‐substituted dimer gave a meso–meso, β‐β doubly linked porphyrin dimer.     

Two polymorphs of N‐(2‐methoxyphenyl)‐4‐oxo‐4H‐chromone‐3‐carboxamide

The title compound, C₁₇H₁₃NO₄, crystallizes in two polymorphic forms, each with two molecules in the asymmetric unit and in the monoclinic space group P2₁/c. All of the molecules have intramolecular hydrogen bonds involving the amide group. The amide N atoms act as donors to the carbonyl group of the pyrone and also to the methoxy group of the benzene ring. The carbonyl O atom of the amide group acts as an acceptor of the β and β′ C atoms belonging to the aromatic rings. These intramolecular hydrogen bonds have a profound effect on the molecular conformation. In one polymorph, the molecules in the asymmetric unit are linked to form dimers by weak C—H...O interactions. In the other, the molecules in the asymmetric unit are linked by a single weak C—H...O hydrogen bond. Two of these units are linked to form centrosymmetric tetramers by a second weak C—H...O interaction. Further interactions of this type link the molecules into chains, so forming a three‐dimensional network. These interactions in both polymorphs are supplemented by π–π interactions between the chromone rings and between the chromone and methoxyphenyl rings.     

Two polymorphs of 20‐desmethyl‐β‐carotene

Two polymorphs of 20‐desmethyl‐β‐carotene (systematic name: 20‐nor‐β,β‐carotene), C₃₉H₅₄, in monoclinic and triclinic space groups, were formed in the same vial by recrystallization from pyridine and water. Each polymorph crystallizes with the complete molecule as the asymmetric unit, and the two polymorphs show differing patterns of disorder. The β end rings of both polymorphs have the 6‐s‐cis conformation, and are twisted out of the plane of the polyene chain by angles of −53.2 (8) and 47.3 (8)° for the monoclinic polymorph, and −43.6 (3) and 56.1 (3)° for the triclinic polymorph. The cyclohexene end groups are in the half‐chair conformation, but the triclinic polymorph shows disorder of one ring. Overlay of the molecules shows that they differ in the degree of nonplanarity of the polyene chains and the angles of twist of the end rings. The packing arrangements of the two polymorphs are quite different, with the monoclinic polymorph showing short intermolecular contacts of the disordered methyl groups with adjacent polyene chain atoms, and the triclinic polymorph showing π–π stacking interactions of the almost parallel polyene chains. The determination of the crystal structures of the two title polymorphs of 20‐desmethyl‐β‐carotene allows information to be gained regarding the structural effects on the polyene chain, as well as on the end groups, versus that of the parent compound β‐carotene. The absence of the methyl group is known to have an impact on various functions of the title compound.     

meso‐Ester Corroles

The introduction of ester groups on the 5‐ and 15‐meso positions of corroles stabilizes them against oxidation and induces a redshift of their absorption and emission spectra. These effects are studied through the photophysical and electrochemical characterization of up to 16 different 5,15‐diester corroles, in which the third meso position is free or occupied by an aryl group, a long alkyl chain, or an ester moiety. Single‐crystal X‐ray structure analysis of five 5,15‐diestercorroles and DFT and time‐dependent DFT calculations show that the strong electron‐withdrawing character of the 5,15 ester substituents is reinforced by their π overlap with the macrocyclic aromatic system. The crystal packing of corroles 2 , 4 , 6 , 9 , and 15 features short distances between chromophores that are stacked into columns thanks to the low steric hindrance of meso‐ester groups. This close packing is partially due to intermolecular interactions that involve inner hydrogen and nitrogen atoms, and thereby, stabilize a single, identical corrole tautomeric form.     

meso‐Nitro‐ and meso‐Aminosubporphyrinatoboron(III)s and meso‐to‐meso Azosubporphyrinatoboron(III)s

meso‐Nitrosubporphyrinatoboron(III) was synthesized by nitration of meso‐free subporphyrin with AgNO₂/I₂. The subsequent reduction with a combination of NaBH₄ and Pd/C gave meso‐aminosubporphyrinatoboron(III). meso‐Nitro‐ and meso‐amino‐groups significantly influenced the electronic properties of subporphyrin, which has been confirmed by NMR and UV/Vis spectra, electrochemical analysis, and DFT calculations. Oxidation of meso‐aminosubporphyrinatoboron(III)s with PbO₂ cleanly gave meso‐to‐meso azosubporphyrinatoboron(III)s that exhibited almost coplanar conformations and large electronic interaction through the azo‐bridge.     

Triclinic and monoclinic polymorphs of meso‐(E,E)‐1,1′‐[1,2‐bis(4‐chlorophenyl)ethane‐1,2‐diyl]bis(phenyldiazene): the high‐yield synthesis of an unexpected product,concomitant polymorphism and configurational disorder

Pyrazolidine‐3,5‐diones and their derivatives exhibit a wide range of biological activities. Seeking to explore the effect of combining a hydrocarbyl ring substituent, as present in sulfinpyrazone (used to treat gout), with a chlorinated aryl ring, as present in muzolimine (a diuretic), we explored the reaction between 1‐phenylpyrazolidine‐3,5‐dione and 4‐chlorobenzaldehyde under mildly basic conditions in the expectation of producing the simple condensation product 4‐(4‐chlorobenzylidene)‐1‐phenylpyrazolidine‐3,5‐dione. However, the reaction product proved to be meso‐(E,E)‐1,1′‐[1,2‐bis(4‐chlorophenyl)ethane‐1,2‐diyl]bis(phenyldiazene), C₂₆H₂₀Cl₂N₄, and a tentative mechanism is proposed. Crystallization from ethanol produces two concomitant polymorphs, i.e. a triclinic form, (I), in the space group P, and a monoclinic form, (II), in the space group C2/c. In both polymorphs, the molecules lie across centres of inversion, but in (II), the molecules are subject to whole‐molecule disorder equivalent to configurational disorder with occupancies of 0.6021 (19) and 0.3979 (19). There are no hydrogen bonds in the crystal structure of polymorph (I), but the molecules of polymorph (II) are linked by C—H...π(arene) hydrogen bonds into complex chains, which are further linked into sheets by C—H...N interactions.     

Solvent influence on the crystal packing of 6‐aminothiocytosine

The crystal structures of 6‐aminothiocytosine (systematic name: 4,6‐diamino‐1,2‐dihydropyrimidine‐2‐thione, DAPMT, C₄H₆N₄S), its hemihydrate (0.5H₂O) and its dimethylformamide (DMF, C₃H₇NO) monosolvate were compared, and the influence of the type of solvent on the supramolecular motifs was analysed. In all three crystal structures, there are two symmetry‐independent molecules (A and B), and these molecules are connected by three relatively short and directional hydrogen bonds to form chains of alternating A and B molecules. A further organization of these chains is dependent on the nature of the solvent molecule. In the unsolvated form, two orientations of the neighbouring chains are observed, and similar motifs – but only one per structure – can be observed in the solvated structures. These two different motifs can be connected by two different kinds of contacts, i.e. either π–π (hemihydrate) or staple‐supported S…S (DMF). In the crystal structures, the O atoms of the solvent molecules are double acceptors of the same type of hydrogen bonds and bind the chains of DAPMT molecules into different motifs (dimeric or infinite chains). A Hirshfeld fingerprint analysis was used for visualization and additional interpretation of these results.     

Two polymorphs of N‐(2,6‐difluorophenyl)formamide

The structures of two distinct polymorphic forms of N‐(2,6‐difluorophenyl)formamide, C₇H₅F₂NO, have been studied using single crystals obtained under different crystallizing conditions. The two forms crystallize in different space groups, viz. form (Ia) in the orthorhombic Pbca and form (Ib) in the monoclinic P2₁ space group. Each polymorph crystallizes with one complete molecule in the asymmetric unit and they have a similar molecular geometry, showing a trans conformation with the formamide group being out of the plane of the aromatic ring. The packing arrangements of the two polymorphs are quite different, with form (Ia) having molecules that are stacked in an alternating arrangement, linked into chains of N—H...O hydrogen bonds along the crystallographic a direction, while form (Ib) has its N—H...O hydrogen‐bonded molecules stacked in a linear fashion. A theoretical study of the two structures allows information to be gained regarding other contributing interactions, such as π–π and weak C—H...F, in their crystal structures.     

Hydrogen‐bonded networks in 1‐(4‐methoxyphenyl)‐2,2‐dimethylpropan‐1‐ol

The asymmetric unit of the title compound, C₁₂H₁₈O₂, contains two independent molecules. They differ only slightly in conformation but form completely different intermolecular hydrogen‐bonded arrays. One molecule exhibits disorder in the hydroxy group region, but this does not influence the formation of hydrogen bonds. The bulky tert‐butyl group on one side of the carbinol C atom and the benzene ring on the other side promote the formation of discrete dimeric motifs via hydrogen‐bridged hydroxy groups. Dimers are further joined by strong hydroxy–methoxy O—H...O bonds to form chains with dangling alcohol groups. Weaker intermolecular C—H...O interactions mediate the formation of a two‐dimensional network.     

Large Porphyrin Squares from the Self‐Assembly of meso‐Triazole‐Appended L‐Shaped meso–meso‐Linked ZnII–Triporphyrins: Synthesis and Efficient Energy Transfer

meso‐Triazolyl‐appended Zn^II–porphyrins were readily prepared by Cu^I‐catalyzed 1,3‐dipolar cycloaddition of benzyl azide to meso‐ethynylated Zn^II–porphyrin (click chemistry). In noncoordinating CHCl₃ solvent, spontaneous assembly occurred to form tetrameric array ( 3 )₂ from meso–meso‐linked diporphyrins 3 , and dodecameric porphyrin squares ( 4 )₄ and ( 5 )₄ from the L ‐shaped meso–meso‐linked triporphyrins 4 and 5 . The structures of these assemblies were examined by ¹H NMR spectra, absorption spectra, and their gel permeation chromatography (GPC) retention time. Furthermore, the structures of the dodecameric porphyrin squares ( 4 )₄ and ( 5 )₄ were probed by small‐ and wide‐angle X‐ray scattering (SAXS/WAXS) measurements in solution using a synchrotron source. Excitation‐energy migration processes in these assemblies were also investigated in detail by using both steady‐state and time‐resolved spectroscopic methods, which revealed efficient excited‐energy transfer (EET) between the meso–meso‐linked Zn^II–porphyrin units that occurred with time constants of 1.5 ps^?1 for ( 3 )₂ and 8.8 ps^?1 for ( 5 )₄.     

Crystal structures of the anhydrous and two solvated forms of methyl 4‐(4‐fluorophenyl)‐6‐methyl‐2‐oxo‐1,2,3,4‐tetrahydropyrimidine‐5‐carboxylate

Methyl 4‐(4‐fluorophenyl)‐6‐methyl‐2‐oxo‐1,2,3,4‐tetrahydropyrimidine‐5‐carboxylate, ( I ), was found to exhibit solvatomorphism. The compound was prepared using a classic Biginelli reaction under mild conditions, without using catalysts and in a solvent‐free environment. Single crystals of two solvatomorphs and one anhydrous form of ( I ) were obtained through various crystallization methods. The anhydrous form, C₁₃H₁₃FN₂O₃, was found to crystallize in the monoclinic space group C2/c. It showed one molecule in the asymmetric unit. The solvatomorph with included carbon tetrachloride, C₁₃H₁₃FN₂O₃·0.25CCl₄, was found to crystallize in the monoclinic space group P2/n. The asymmetric unit revealed two molecules of ( I ) and one disordered carbon tetrachloride solvent molecule that lies on a twofold axis. A solvatomorph including ethyl acetate, C₁₃H₁₃FN₂O₃·0.5C₄H₈O₂, was found to crystallize in the triclinic space group P with one molecule of ( I ) and one solvent molecule on an inversion centre in the asymmetric unit. The solvent molecules in the solvatomorphs were found to be disordered, with a unique case of crystallographically induced disorder in ( I ) crystallized with ethyl acetate. Hydrogen‐bonding interactions, for example, N—H…O=C, C—H…O=C, C—H…F and C—H…π, contribute to the crystal packing with the formation of a characteristic dimer through N—H…O=C interactions in all three forms. The solvatomorphs display additional interactions, such as C—F…N and C—Cl…π, which are responsible for their molecular arrangement. The thermal properties of the forms were analysed through differential scanning calorimetry (DSC), hot stage microscopy (HSM) and thermogravimetric analysis (TGA) experiments.     

High-temperature phases of poly(p-xylylene)

The crystal structure of poly(p-xylylene), as polymerized, is the α form. This transforms irreversibly to the β from by annealing or drawing. To clarify the mechanism of this transition, structural changes of the α and β crystals were examined with a high-temperature stage in the electron microscope. Two high-temperature phases, β₁ and β₂, were found and their structures were analyzed. In these structures lattice distortions due to rotational and translational motions of chains are in troduced, especially in the β₂ form. The α → β transition is induced through such a disordered phase. The statistical arrangement of a molecule in the β-form unit cell results from freezing the disorder in the high-temperature phases.     

Twinning in 5‐fluorosalicylic acid: description of a new polymorph

The crystal structure of 5‐fluorosalicylic acid is known from the literature [Choudhury & Guru Row (2004). Acta Cryst. E 60 , o1595–o1597] as crystallizing in the monoclinic crystal system with space‐group setting P2₁/n and with one molecule in the asymmetric unit (polymorph I). We describe here a new polymorph which is again monoclinic but with different unit‐cell parameters (polymorph II). Polymorph II has two molecules in the asymmetric unit. Its structure was modelled as a twin, with a pseudo‐orthorhombic C‐centred twin cell.     

On the clathrate structures of syndiotactic poly(m-methylstyrene)

The crystal structures of clathrate forms of syndiotactic poly(m-methylstyrene) containing guest molecules having different steric hindrance (CS₂, benzene and orto-dichlorobenzene) are presented. The structures are all characterized by polymer chains in s (2/1)2 helical conformation and guest molecules packed in an orthorhombic unit cell according to the space group Pcaa. All the presented clathrates belongs to β class indipendently from the dimensions of the guest molecule. In this aspect they differ both from clathrate forms of syndiotactic polystyrene, all belonging to α class, and from clathrate forms of syndiotactic poly(p-methylstyrene) that belong to α or β class according to the steric hindrance of the guest molecule.