Search

Compared to the numerous X-ray crystal structures of protein-carbohydrate complexes, the successful elucidation of the crystal structures of complexes between artificial receptors and carbohydrates has been very rarely reported in the literature. In this work, we describe the binding modes of two complexes formed between methyl α-d-glucopyranoside and an artificial receptor belonging to the class of compounds consisting of a 1,3,5-trisubstituted 2,4,6-trialkylbenzene scaffold. It is particularly noteworthy that these two complexes are present in one crystal structure, as was observed by us for the first time in the case of the recently reported three crystal structures of the complexes with methyl β-d-glucopyranoside, each containing two different receptor-carbohydrate complexes. The noncovalent interactions stabilizing the new complexes are compared with those observed in the aforementioned crystalline complexes with methyl β-d-glucopyranoside.

In the title 1:1 co-crystal, [Cu(C24H24N8O6)]·C11H11N3O4, each of the crystal components forms undulating layers which stack alternately along the b-axis direction. Molecules of the CuII complex are connected via C—H...O hydrogen bonds involving the nitro and keto oxygen atoms, thus forming supramolecular networks. Molecules of the arylhydrazone component are linked by C—H...O interactions into zigzag strands showing no interstrand association.

Correction for ‘Binding modes of methyl α-d-glucopyranoside to an artificial receptor in crystalline complexes’ by Linda Köhler et al., RSC Adv., 2021, 11, 22221–22229. DOI: 10.1039/d1ra03390e.

The syntheses and crystal structures ofN-(7-bromomethyl-1,8-naphthyridin-2-yl)acetamide dioxane hemisolvate, C11H10BrN3O·0.5C4H8O2, (I), and bis[N-(7-dibromomethyl-1,8-naphthyridin-2-yl)acetamide] dioxane hemisolvate, 2C11H9Br2N3O·0.5C4H8O2, (II), are described. The molecules adopt a conformation with the N—H hydrogen pointing towards the lone electron pair of the adjacent naphthyridine N atom. The crystals of (I) are stabilized by a three-dimensional supramolecular network comprising N—H...N, C—H...N and C—H...O hydrogen bonds, as well as C—Br...π halogen bonds. The crystals of compound (II) are stabilized by a three-dimensional supramolecular network comprising N—H...N, C—H...N and C—H...O hydrogen bonds, as well as C—H...π contacts and C—Br...π halogen bonds. The structure of the substituent attached in the 7-position of the naphthyridine skeleton has a fundamental influence on the pattern of intermolecular noncovalent bonding. While the Br atom of (I) participates in weak C—Br...Oguestand C—Br...π contacts, the Br atoms of compound (II) are involved in host–host interactionsviaC—Br...O=C, C—Br...N and C—Br...π bonding.

X-ray analyses of a series of benzene-based tripodal molecules 1–9, bearing either bromo-substituted pyrazole groups or analogues lacking the bromo substituents, provide interesting insights into the molecular recognition phenomena and also give information about the different conformations which adopt the tripodal molecules in the solvent-free crystals and in solvates. The crystal packings are characterized by the presence of C–H⋯O, C–H⋯N, C–H⋯Br and C–H⋯Cl hydrogen bonds as well as C–Br⋯N, C–Br⋯Br, C–Br⋯Cl and C–Br⋯π halogen bonds. The conformations observed in the case of the triethyl- and trimethoxybenzene-based compounds can be defined as ab'ab'ab', ab'ab'ba', ab'ab'bb', ab'aa'ba', ab'aa'bb', aa'ab'ba' and aa'aa'aa' with the pyrazole-bearing arms arranged either in an aaa or an aab fashion.

A series of azines featuring differently halogen and protic group substituted pyridine, pyrimidine and pyridazine compounds have been synthesized and studied in terms of their crystal structures in order to develop a better understanding of the links between structural conditions and molecular packing behavior. Complemented by the structure results of related compounds known from the literature, intermolecular contact relationships connected to the present substance types were found, having potential use in future crystal engineering of similar compounds. This primarily involves the formation of N⋯I contacts aside from specific halogen⋯halogen and hydrogen bond type interactions.

Crystal structures of two 4-substituted derivatives of 2-acetyl­phenol are discussed comparatively with reference to modes of hydrogen bonding., In the title compounds, C10H8O2, (I), and C13H14O3, (II), the 2-acetyl-4-ethynylphenol unit displays a planar geometry, which is stabilized by an intra­molecular O—H⋯O hydrogen bond. The crystal structure of (I) is constructed of infinite strands, along [101], of C—H⋯O=C hydrogen-bonded mol­ecules, which in turn are linked by C—H⋯π inter­actions. In the crystal of (II), which crystallized with three independent mol­ecules per asymmetric unit, the non-polar parts of the mol­ecules form hydro­phobic layered domains, parallel to (10-1), which are separated by the polar groups. While the 2-acetyl­phenol part of the mol­ecules are involved in O—H⋯O=C hydrogen bonding, the ternary OH groups creates a cyclic pattern of O—H⋯O hydrogen bonds.

The title compound is composed of a bis­(hydrazoniminato)copper(II) complex and the basic hydrazone imine shows a mol­ecular framework with layers each constructed from one of the two components arranged in alternating order. Layer formation is supported by C—H⋯O inter­actions., In the title 1:1 co-crystal, [Cu(C24H24N8O6)]·C11H11N3O4, each of the crystal components forms undulating layers which stack alternately along the b-axis direction. Mol­ecules of the CuII complex are connected via C—H⋯O hydrogen bonds involving the nitro and keto oxygen atoms, thus forming supra­molecular networks. Mol­ecules of the aryl­hydrazone component are linked by C—H⋯O inter­actions into zigzag strands showing no inter­strand association.

Pyrazole-based artificial receptors have often been used in the recognition of ions, but in the area of sugar recognition the potential of pyrazole-based recognition groups has only been rarely examined. In this paper we describe the syntheses of twelve new pyrazole-bearing compounds, which are all potentially applicable for use as carbohydrate receptors. The prepared compounds enforce tripodal architecture and are based on a triethyl- or trimethoxybenzene scaffold. Representative complexation studies with selected carbohydrates showed interesting binding preferences of the new compounds.

Four new host compounds of dumbbell shape featuring bulky 2,3,4,5-tetraphenylcyclopenta-2,4-dien-1-ol moieties attached to both ends of a linear spacer element of different lengths comprising both 1,4-phenylene and ethynylene subunits are synthesized and corresponding crystal inclusions involving DMSO, DMF, MeCN, and THF as guest solvents (seven examples of inclusion compounds) are isolated. X-ray structural analysis shows the formation of 1:2 host/guest entities being a basic supramolecular motif of the crystal inclusions. Nevertheless, additional solvent molecules seem to be necessary for stabilization of the crystal structure in most cases of the inclusion species indicating the occurrence of unusually high stoichiometric ratios of included solvent as a specific characteristic of the new type of host molecule.

In the crystal structure of 2,2′′-bis­(2,7-di­chloro-9-hy­droxy-9-fluoren­yl)-1,1′:4′,1′′-terphenyl as the tris­(tri­ethyl­amine) solvate, the diol host mol­ecule possesses a ‘folded’ mol­ecular conformation with inversion symmetry. Two of the three solvent mol­ecules form O—H⋯N hydrogen bonds and the third one forms C—H⋯N hydrogen bonds with the host compound., In the title solvate, C44H26Cl4O2·3C6H15N, the asymmetric part of the unit cell comprises two halves of the diol mol­ecules, 2,2′′-bis­(2,7-di­chloro-9-hy­droxy-9H-fluoren-9-yl)-1,1′:4′,1′′-terphenyl, and three mol­ecules of tri­ethyl­amine, i. e. the diol mol­ecules are located on crystallographic symmetry centres. Two of the solvent mol­ecules are disordered over two positions [occupancy ratios of 0.567 (3):0.433 (3) and 0.503 (3):0.497 (3)]. In the diol mol­ecules, the outer rings of the 1,1′:4′,1′′-terphenyl elements are twisted with reference to their central arene ring and the mean planes of the fluorenyl moieties are inclined with respect to the terphenyl ring to which they are connected, the latter making dihedral angles of 82.05 (8) and 82.28 (8)°. The presence of two 9-fluoren-9-ol units attached at positions 2 and 2′′ of the terphenyl moiety induces a ‘folded’ geometry which is stabilized by intra­molecular C—H⋯O hydrogen bonds and π–π stacking inter­actions, the latter formed between the fluorenyl units and the central ring of the terphenyl unit [centroid–centroid distances = 3.559 (1) and 3.562 (1) Å]. The crystal is composed of 1:2 complex units, in which the solvent mol­ecules are associated with the diol mol­ecules via O—H⋯N hydrogen bonds, while the remaining solvent mol­ecule is linked to the host by a C—H⋯N hydrogen bond. The given pattern of inter­molecular inter­actions results in formation of chain structures extending along [010].

New crystalline complexes of hexapodal pyrazole-based hosts with NH4+PF6−and/or solvent molecules were obtained and detailed analysed. The binding motifs observed between the binding partners give valuable insights into the phenomena of molecular recognition processes. Analyses of the conformations of the hexasubstituted benzene derivatives have shown that both ababab as well as abbabb and aaabbb conformations of the haxapodal compounds 1–3 are observed in the crystal structures 1a–d, 2, 2a, 3a and 3b.

The ethynyl­pyrimidine moiety displays an almost planar geometry. In the crystal, mol­ecules are linked by O—H⋯N and C—Hpyrimidine⋯O hydrogen bonds, forming a three-dimensional supra­molecular architecture., In the title compound, C9H9ClN2O, the ethynyl­pyrimidine moiety displays an almost planar geometry. In the crystal, mol­ecules are linked by O—H⋯N and C—Hpyrimidine⋯O hydrogen bonds, forming a three-dimensional supra­molecular architecture.

In the title compound, C17H16O, the phenyl rings are twisted relative to each other at an angle of 85.9 (1)°. The crystal structure features weak C—H...π interactions, which connect the molecules into a three-dimensional supramolecular network.

Derived from the result of a previous crystallographic study regarding an ethynylene bridged bispyrimidine, the presence of two intramolecular C–H⋯N hydrogen bonding contacts being responsible for a fixation of the terminal t-butylthio units to the azine nitrogens was noticed. Acting as stimulus, a series of different pyridine and pyridazine derivatives also featuring this unusual functionality has been synthesized and structurally studied. In order to support the investigations concerning this particular bonding pattern performed via X-ray structure analysis, calculations based on the density functional theory were carried out. It was found that the formation of the intramolecular hydrogen bonding motif has not only impact on the molecular stability but in some cases also predictably influences the reactivity and the packing behavior of the different heterocycles.

Sixteen new bisurea compounds incorporating versatile proteinogenic amino acids as well as nipecotic acid have been synthesized via addition reaction to aryl diisocyanates. The products were analytically characterized and their ability for anion recognition was studied by UV/Vis spectroscopy. In the presence of fluoride, acetate or dihydrogenphosphate ions, hyperchromic and bathochromic peak shifts were determined. By way of contrast, bromide, iodide, or hydrogensulfate ions cause no significant change of absorbance. The special effect of heterocyclic derivatives was explained by molecular modeling calculations. In addition, the crystal structure of the byproduct dimethyl N,N′-(1,4-phenylene)dicarbamate is discussed.

Imitative of a supramolecular synthon moiety D comprising two 3,5-bis(hydroxymethyl) substituted benzoic acid moieties (2), the covalently linked surrogate molecule 1 has been designated and synthesized. Crystal structures have been compared including also substituted and molecularly elongated derivatives of 2. They show largely common structural features in planar geometry of the building units and layer formation in the crystal packing, while the hydrogen bonded patterns within the layers differ according to the structural molecular changes. Moreover, synthon robustness of the dimer carboxylic acid motif has been confirmed.

Four trityl compounds differing both in the functional group (OH, OMe, NH2) at the specific trityl carbon and a para substituent, being bromine or phenyl at one of the phenyl groups, have been prepared and structurally studied by means of single crystal X-ray diffraction and making use of Hirshfeld surface analysis. Compared to the structures of corresponding prototypes and analogues, specific interaction modes and packing motifs including cluster aggregates as well as non-cluster type structures depending on the substitution and involving polymorphism were found, opening potential trend prediction with reference to crystal engineering being useful in this compound class.

A series of azulenes derived from diethyl azulene-1,3-dicarboxylate (1) as the parent compound and featuring a systematic addition of polar substituents (Cl, Br, OH and NH2) both in the positions 2 and 6 of the azulene (2–6) were prepared and investigated with reference to their X-ray crystal structures, having occurrence and modes of π⋯π stacking of the azulene units particularly in view. Except the parent compound 1, all the other derivatives show typical π-stacked dimers in the crystal packing being modified in pattern under the influence of the specific substitution. This suggests that corresponding substitution of an azulene is not obstructive to π⋯π stacking formation and may even be used for a potential pattern design of azulene dimers in a crystalline material.

Crystalline inclusion compounds of diol hosts 1 and 2 typical of a basic 2,2″-[1,1′:4′,4″]-terphenyl moiety with two attached 9-fluorenol or tert-butyl-substituted 9-fluorenol units and a variety of aprotic guest molecules have been prepared and studied with reference to their crystal structures. Common and differing structural features among one another and including previously described host–guest complexes of 1 and 2 with protic instead of aprotic guest species are distinguished, indicating potential uses in promising supramolecular inclusion formation and underscoring solvent inclusion.

A series of bispyridines and bispyrimidines 1a, 1b, 1c, 1d, 1e showing the heterocycles attached to both ends of an ethynylene unit and being α-substituted with chloro, tert-butylthio, and methoxy groups have been synthesized via cross-coupling technique and their crystal structures studied by X-ray diffraction analysis. Supramolecular interactions of C–H···N and π···π stacking type were found to largely dominate the structures according to the compound species. A trial was given to deduce the markedly differing temperatures of melting among the compounds from special features of the crystal structures.

A rather easily structured permethylated dinitro calix[4]arene was found to exhibit large, stable and rigid channels in the solid state. These were obtained as guest free as well as solvent filled species and proved to reversibly adsorb selected organic solvents. Combined use of QMB measurements and X-ray powder diffraction revealed the predominantly reversible interaction of dichloromethane vapour with the channel structure as well as the integrity of the nanopores during adsorption and desorption. Examination of the flexible host component by NMR spectroscopy revealed a mixture of interchanging conformational isomers which could explain the high sensitivity of the crystallization process from the employed solvents.

The syntheses and X-ray structures of three methylated bisphenol F derivatives and one respective analogue are reported. A special emphasis lies on the influence of methyl groups on the conformation of the common diphenylmethane scaffold. The introduction of four methyl groups to bisphenol F was found not to disturb its typical strong hydrogen bond network, and yet, to change the pattern of the aromatic interactions in the overall packing. According to the isometricity comparison, the addition of methyl groups to the diphenylmethane core has a greater influence on the conformation of the individual molecules, than the presence or absence of hydrogen bonding donors or acceptors.

The diol host compound 2 featuring a structure with two 9-fluorenol moieties attached in 3,3′-position to a biphenyl core unit has been synthesized and is shown to form crystalline inclusion complexes with organic guest molecules. Aside from the single-crystal X-ray structures of unsolvated 2 in two polymorphous forms (2A, 2B), structures of five inclusion compounds with 1,4-dioxane (2a), DMSO (2b), diethylamine (2c), acetic acid (2d), and ethyl acetate (2e) are described and comparatively discussed in the interaction behavior including corresponding host compounds with different attachment mode of the biphenyl unit and the diphenylhydroxymethyl-substituted equivalent.

The synthesis, structural and chemosensing properties of several lower rim-dansylated calix[4]arenes bearing different methylene bridge substituents are described. Compared to bridge-unsubstituted pendants neither the conformational nor the fluorescence characteristics of the calixarene core are perceptibly influenced by the bridge substituent. X-ray structure as well as NMR measurements indicates the lower rim-propoxylated and-dansylated calixarenes to adopt the cone conformation capable of the complexation of Cu2+ ions at micromolar level. Fluorescent measurements point to selective 1:2 calixarene: Cu2+ complex formation with sensing parameters being of a suitable level to make the use as a potentially immobilisable chemosensor for the detection of Cu2+ ions promising.

Two new linker-type molecules 1a and 1b composed of o-hydroxyacetophenone coordinative groups attached to linear ethynylene or 1,4-phenylenediethynylene spacer units have been synthesised and structurally characterised. An X-ray crystallographic study for both compounds has shown structures with strong intramolecular hydrogen bonds fitting in the model of ‘Intramolecular Resonance Assisted Hydrogen Bond (IRHAB)’. Initial coordination experiments with Cu(II) were performed and the resulting materials characterised by PXRD. The similarity of the copper coordination between these compounds and copper(II) acetylacetonate complexes was demonstrated by XPS measurements. Based on the evidence of these studies, and on elemental analysis, the formation of the corresponding coordination polymers comprising Cu(II) and the linkers has been proposed

Two new crystalline host compounds of bisfluorenol type featuring an elongated core structure compared to a known parent molecule (2,2′′-[1,1′:4′,1′′]-terphenylyl versus 2,2′-biphenylyl) have been synthesized. Crystalline inclusion compounds involving protic guest molecules have been prepared and studied with reference to their crystal structures. Conformational changes as against the prototype compound due to prevention of the intramolecular hydrogen bond between the hydroxy groups give rise to a specific mode of host–guest association, showing preference to the formation of infinite hydrogen bonded chains instead of discrete host–guest units. Potentiality for crystal engineering using respective two-component molecular systems is indicated.

Fourteen new derivatives of 9,10-anthraquinone or 9,10-dimethoxyanthracene were designed, synthesised and characterised. Regarding the structure, the compounds are π-conjugated (cross and linear, respectively) and feature thiophene terminated side arms attached to five different positions of the anthraquinone or anthracene core. The synthesis of the compounds involves a cross-coupling procedure in the key reaction steps. Crystal structures of compounds 5 and 19 have been studied. The thiophene containing title compounds 1–5 can be reduced and oxidised by a two step redox process. The electrochemical parameters have been analysed by cyclic voltammetry (CV). Theoretical calculations in the framework of all-electron density functional theory (DFT) were used to investigate the electronic structure of the individual free molecules. Furthermore, calculations of the transport properties of model devices containing compounds 1–3 and respective reduced hydroquinone derivatives assembled at Au(111) electrodes were carried out to evaluate their potential for the application as redox-active switches.

The new linker-type ligand 1, featuring two L-phenylalanine-terminated urea moieties attached to the para positions of a central phenylene unit has been synthesized. Its coordination polymer formed with lead(II) and containing DMF and water as solvent molecules has been prepared and structurally studied by X-ray crystallography.

The diol host compound 2 has been synthesised and its behaviour to form crystalline inclusion compounds is discussed in comparison with an analogous ethynylene spaced host compound 1. The rotation around the fluorenol–anthracene bonds in 2 is highly restricted as indicated by solution NMR spectroscopy, molecular mechanics and semi-empirical calculations. Single-crystal X-ray structures of the inclusion complexes of 2 with 1-BuOH (2a), morpholine/H2O (2b) and DMSO (2c) are in agreement with the bent geometry of the anthracene ring system suggested by the calculations. The structures exhibit specific modes of hydrogen bond interactions.

Reaction of Cu(NO3)2·3H2O or Cu(CH3COO)2·H2O with the bis(2-hydroxyphenylimine) ligands H2L1-H2L4 gave four Cu(II) complexes of composition [Cu2(L1)(NO3)2(H2O)]·MeOH, [Cu2(L2)2], [Cu2(L3)2] and [Cu2(L4)2]·2MeOH. Depending on the spacer unit, the structures are characterized by a dinuclear arrangement of Cu(II) within one ligand (H2L1), by a double-stranded [2+2] helical binding mode (H2L2 and H2L3) and a [2 + 2] metallomacrocycle formation (H2L4). In these complexes, the Cu(II) coordination geometries are quite different, varying between common square planar or square pyramidal arrangements, and rather rare pentagonal bipyramidal and tetrahedral geometries. In addition, solution studies of the complex formation using UV/Vis and ESI-MS as well as solvent extraction are reported.

Three acetonitrile solvates of tetramethoxycalix[4]arenes equally substituted on opposite methylene bridges are described with respect to their conformation and packing behaviour. All of the host molecules adopt a 1,2-alternate conformation, their packing architecture seems to be affected by the spatial demand of the bridge substituents only. This results in the synthetically implemented fine-tuning of the molecular arrangement. The engineering of the relevant packing motif, the “synthon” may be discussed most appropriate by the term “synthon engineering” following the expression of crystal engineering.

Four new azulene derivatives featuring two π-conjugated and sulfur terminated rigid side arms in the 1,3-positions of the azulene core were designed, synthesized, and characterized. The syntheses were carried out on the basis of a palladium cross-coupling procedure in the key reaction step. The crystal structures of the target compound 3 and of the intermediate compounds 7 and 9 have been studied. Supporting density functional theory calculations reveal insights into the electronic properties of the particular azulenes. The comparison of measured UV–Vis, infrared, and Raman data to calculated values allowed assignment of major spectral features to the particular structural differences of the new compounds and comparison to plain azulene. Cyclic voltammetry measurements were performed showing the redox characteristics of the new azulene derivatives. Copyright © 2012 John Wiley & Sons, Ltd.

Si NMR shielding tensors of a series of triphenylsilanes Ph3SiR with R = Ph, Me, F, Cl, Br, OH, OMe, SH, NH2, SiPh3 ,C CPh were determined from 29 Si CP/MAS spectra recorded at low spinning rates. In addition the principal components of the shielding tensor were calculated employing the DFT-IGLO method. For most silanes experi- mental and calculated values are in good accordance. Larger differ- ences were observed for systems with hydrogen bridge forming sub

X-ray crystal structures of several novel diametrically bridge-disubstituted calix[4]arenes are presented, revealing the calixarene core in the rare 1,2-alternate conformation. Structural comparisons suggest a tunable inclusion behavior depending on the bridge substituents, which is a promising tool for supramolecular host guest design in terms of “synthon engineering”.

A series of partially fluorinated and specifically para-substituted tolanes (1–4) have been synthesized via palladium-catalyzed Sonogashira cross-coupling reaction. The single-crystal structures have been determined by X-ray diffraction. The molecules adopt a geometry being more or less disturbed from planarity due to crystal packing effects. The packing structures are characterized by the formation of molecular stacks achieved through different modes of π⋯π interaction and being accomplished by other types of weak interactions including hydrogen bonds as well as bromo and in particular fluoro involved contacts.

The formation of crystalline host–guest complexes of three constitutionally isomeric host compounds 1–3 featuring two diphenylhydroxymethyl groups attached in different positions to a biphenylylene central moiety is studied. Dependent on the connection mode (2,2′-, 3,3′-, or 4,4′-) with reference to the biphenylylene unit, a distinctly different complex behavior of the host compounds is observed. X-ray crystal structures of the solvent-free hosts are reported including a third polymorph with respect to already known polymorphous structures. The crystal structures of eight host–guest complexes of 1–3, including a pair of complexes differing only in the host/guest stoichiometry, are described and comparatively discussed covering the structures of known complex species of the isomeric hosts. Correlations between the constitutional isomerism of the host molecules and their conformational as well as packing structures in the crystalline state, both in unsolvated and solvent complexed form, are demonstrated pro...

Four new acetylacetonato disubstituted dihydrazones that feature different arylene and specifically spaced diaryl units between the hydrazone groups leading to different molecular geometries have been synthesized and comparatively studied with regard to their crystal structures. All structures show intramolecular N—H···O interactions to yield two six-membered hydrogen bonded chelate rings in the molecule. Dependent on the molecular geometry, intermolecular hydrogen bonding or offset π···π stacking contacts involving the aryl and chelate rings dominate the packing structure.

A series of calix[4]arenes bearing various substituents including alkyl, p-bromobenzyl, carboxy and allyl at opposite methylene bridges has been synthesized via successive metallation followed by nucleophilic substitution. In a first step, mono-lithiated calix[4]arenes react with terminal bromoalkanes to give 2-alkylated calix[4]arenes or with CO2 the respective calixarene-2-carboxylic acid in good yields. A second lithiation step of the monosubstituted products with subsequent attachment of both polar and non-polar substituents yields several new diametrally bridge-disubstituted calix[4]arenes. 2D-NMR measurements establish the disubstituted calixarenes to predominantly adopt the 1,2-alternate conformation in solution. First examples of X-ray crystal structures of the new type of disubstituted calix[4]arenes are described featuring the calix[4]arene also in the rare 1,2-alternate conformation.

A series of benzil monohydrazones (1a, 1d) and corresponding dibenzil azines (2a–2d) featuring different p-aryl substituents have been synthesized and studied in regard of their crystal structures. Configurational and conformational properties as well as non-covalent interaction and packing behaviour of the molecules connected with the different substitution are discussed. The dibenzil azine 2a was found as a polymorph with reference to a known crystal structure.

The X-ray crystal structure of an acetonitrile solvate of 5,11,17,23-tetra-tert-butyl-26,28-dihydroxy-25,27-dimethoxycalix[4]arene that is 1a, showing the unusual coexistence of two basic conformations in the crystal, that is, cone and 1,2-alternate, is analyzed. In contrast to this conformational coexistence of crystallographically independent molecules, the predominant conformation in solution and also in the related toluene (1b) and toluene/acetonitrile (1c) solvates is the cone conformation. With the help of calculations on the ground state energy of the single conformers and DSC measurements as well as crystallization experiments of 1 in toluene/acetonitrile mixtures of different ratio a possible explanation of this phenomenon is given.

Three solvate crystal structures of the laterally ethyl substituted tetra-tert-butyltetramethoxycalix[4]arene 1 [(1·THF (1a), 1·CHCl3 (1b) and 1·CH2Cl2 (1c)] are compared to the corresponding solvent-free structure (1) using single crystal X-ray structure determination, isostructurality and molecular isometricity calculations. To study the effect of the lateral substitution, the laterally non-substituted host with the guest THF (2a) is also included to the comparison. The calixarene molecules in the different structures all adopt the partial cone conformation with different affection of the respective guest molecules, always being positioned interstitially. Depending on the lateral substitution and the size of the included guests, the molecular conformation of the calix[4]arene shows small differences relating to the alignment of the arene units. The channels disposable of the solvent guest molecules in the crystal structures straighten as the effect of lateral substitution of the host calix[4]arene. The orthorhombic crystal structures of 1a–c are isostructural irrespective of the included solvent molecules, while 1 and 2a crystallise in the same monoclinic space group.

A new trigonal host molecule 1 featuring three 4-(9-hydroxy-9-fluorenyl)phenyl units symmetrically attached to a benzene core was synthesized and is shown to yield a 1:3 (host:guest) crystalline inclusion compound with DMSO (1a). The crystal structure of 1a is distinguished by a rare case of piedfort arrangement of host molecules and a unique hexameric cluster formation of DMSO.

Three upper rim site lipophilic calix[4]arenes 1–3 featuring different para-alkanoyl substituents at the phenolic moieties, i.e.n-hexanoyl, n-octanoyl and 3-cyclohexylpropanoyl groups, are reported to complex, aside from the common solvent molecule n-butanol, different keto and hydroxylic terpene guest molecules such as (−)-menthone, (−)-menthol or (+)-carvone in the solid state. Although for all six inclusion compounds described here, a strict 1 : 1 host : guest stoichiometry is observed, complementary size and polarity relationships between the cone shaped calixarene cavity and the guest molecule emerge from single crystal X-ray structural study. Dependent on the structure of the guest molecule, the calixarenes are arranged in a head-to-head or head-to-tail orientation in the crystalline packing, giving rise to capsular or otherwise deeply enclosed inclusion mode of the guest molecules, respectively. Furthermore, the O-acyl atoms of the calixarenes were found to be directly involved in host–guest interaction. In order to estimate the degree of isostructurality of the host frameworks and to examine the influence of the guest molecules on the solid-state conformation of these calixarene molecules, isostructurality comparison, cell similarity and molecular isometricity calculations were carried out revealing a rare case of supramolecular morphotropism for the pair of (−)-menthone and (−)-menthol inclusions of the n-hexanoyl substituted calixarene. Structure–inclusion property relationship was examined by QMB measurements of thin layers of the calixarenes. Vapor studies with different terpenes and common organic solvents show an increased affinity towards guest molecules with polar functionalities, whereas small solvent molecules like acetone are bound considerably better than the more bulky terpene molecules.

Crystal structures of the configurational isomers of benzil monoxime (1 and 2), a p-methoxy derivative (3) and its solvated species with triethylamine (3a) are reported showing specific influences of the molecular configuration, substitution and solvation on the conformational property and packing behaviour of the molecules. Based on the observed interdependences, in particular involving modes of interaction, potential utilization of the 1,2-dione monoxime functional unit for the purpose of crystal engineering seems promising.

Crystal structures of a series of p-halogenated 6,6-diphenylfulvenes 2–5 are reported and comparatively discussed including the known structure of the non-halogenate parent compound 1. The molecular structures show twisted conformations of the plane aryl and fulvene subunits against each other, rather unaffected by the different halogen substituents. The packing structures exclusively involve C–H···X (X = F, Cl, π) contacts while Hal···Hal and π-stacking interactions do not occur.