共查询到20条相似文献,搜索用时 23 毫秒
1.
Andreas Schultz Sabine Laschat Michael Morr Siegmar Diele Michael Dreyer Gerhard Bringmann 《Helvetica chimica acta》2002,85(11):3909-3918
The synthesis of chiral triphenylenes 7a , b bearing side chains derived from enantiomerically pure trimethyloctanoate 1a and tetramethyldecanoate 1b from the preen‐gland wax of domestic goose was achieved in 3 or 4 steps. Compounds 7a , b were nonmesogenic; however, mixtures of 7a , b with hexakis(octyloxy)triphenylene or hexakis(decyloxy)triphenylene displayed columnar mesophases or soft crystal G phases, as was shown by differential‐scanning calorimetry and optical‐polarizing microscopy. Circular‐dichroism measurements revealed weak associations of 7a , b in solution. 相似文献
2.
Andreas Lemmerer 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(12):o626-o629
The crystal structures and hydrogen‐bonding patterns of 3‐phenylpropylammonium benzoate, C9H14N+·C7H5O2−, (I), and 3‐phenylpropylammonium 3‐iodobenzoate, C9H14N+·C7H4IO2−, (II), are reported and compared. The addition of the I atom on the anion in (II) produces a different hydrogen‐bonding pattern to that of (I). In addition, the supramolecular heterosynthon of (II) produces a chiral crystal packing not observed in (I). Compound (I) packs in a centrosymmetric fashion and forms achiral one‐dimensional hydrogen‐bonded columns through charge‐assisted N—H...O hydrogen bonds. Compound (II) packs in a chiral space group and forms helical one‐dimensional hydrogen‐bonded columns with 21 symmetry, consisting of repeating R43(10) hydrogen‐bonded rings that are commonly observed in ammonium carboxylate salts containing chiral molecules. This hydrogen‐bond pattern, which has been observed repeatedly in ammonium carboxylate salts, thus provides a means of producing chiral crystal structures from achiral molecules. 相似文献
3.
Choudhury M. Zakaria George Ferguson Alan J. Lough Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(1):o1-o5
In the adduct 1,2‐bis(4‐pyridyl)ethane–1,1,1‐tris(4‐hydroxyphenyl)ethane (1/2), C12H12N2·2C20H18O3, the bipyridyl component lies across an inversion centre in P. The tris‐phenol molecules [systematic name: 4,4′,4′′‐(ethane‐1,1,1‐triyl)triphenol] are linked by O—H?O hydrogen bonds to form sheets built from R(38) rings, and symmetry‐related pairs of sheets are linked by the bipyridyl molecules via O—H?N hydrogen bonds to form open bilayers. Each bilayer is interwoven with two adjacent bilayers, forming a continuous three‐dimensional structure. In the adduct 1,2‐bis(4‐pyridyl)ethene–1,1,1‐tris(4‐hydroxyphenyl)ethane–methanol (1/1/1), C12H10N2·C20H18O3·CH4O, the molecules are linked by O—H?O and O—H?N hydrogen bonds into three interwoven three‐dimensional frameworks, generated by single spiral chains along [010] and [001] and a triple‐helical spiral along [100]. 相似文献
4.
Photochemically and Thermally Driven Full‐Color Reflection in a Self‐Organized Helical Superstructure Enabled by a Halogen‐Bonded Chiral Molecular Switch 下载免费PDF全文
Hao Wang Dr. Hari Krishna Bisoyi Dr. Ling Wang Dr. Augustine M. Urbas Dr. Timothy J. Bunning Prof. Quan Li 《Angewandte Chemie (International ed. in English)》2018,57(6):1627-1631
Supramolecular approaches toward the fabrication of functional materials and systems have been an enabling endeavor. Recently, halogen bonding has been harnessed as a promising supramolecular tool. Herein we report the synthesis and characterization of a novel halogen‐bonded light‐driven axially chiral molecular switch. The photoactive halogen‐bonded chiral switch is able to induce a self‐organized, tunable helical superstructure, that is, cholesteric liquid crystal (CLC), when doped into an achiral liquid crystal (LC) host. The halogen‐bonded switch as a chiral dopant has a high helical twisting power (HTP) and shows a large change of its HTP upon photoisomerization. This light‐driven dynamic modulation enables reversible selective reflection color tuning across the entire visible spectrum. The chiral switch also displays a temperature‐dependent HTP change that enables thermally driven red, green, and blue (RGB) reflection colors in the self‐organized helical superstructure. 相似文献
5.
Eduardo Beltrán Emma Cavero Dr. Joaquín Barberá Dr. José Luis Serrano Prof. Anabel Elduque Dr. Raquel Giménez Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(36):9017-9023
Chiral polycatenar 1H‐pyrazoles self‐assemble to form columnar mesophases that are stable at room temperature. X‐ray diffraction and CD studies in the mesophase indicate a supramolecular helical organization consisting of stacked H‐bonded dimers. The liquid‐crystalline compounds reported are 3,5‐bis(dialkoxyphenyl)‐1H‐pyrazoles that incorporate two or four dihydrocitronellyl chiral tails. It can be observed that the grafting of these branched chiral substituents onto the 3,5‐diphenyl‐1H‐pyrazole core has a beneficial role in inducing mesomorphism, because isomeric linear‐chain compounds are not liquid crystalline; this is not the usual scheme of behavior. Furthermore, the molecular chirality is transferred to the columnar mesophase, because preferential helical arrangements are observed. Films of the compounds are luminescent at room temperature and constitute an example of the self‐organization of nondiscoid units into columnar liquid‐crystalline assemblies in which the functional molecular unit transfers its properties to a hierarchically built superstructure. 相似文献
6.
Xiao-Qing Cai Bei Tian Jian-Nan Zhang Zhi-Min Jin 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(10):720-723
A fixed hydrogen‐bonding motif with a high probability of occurring when appropriate functional groups are involved is described as a `supramolecular hydrogen‐bonding synthon'. The identification of these synthons may enable the prediction of accurate crystal structures. The rare chiral hydrogen‐bonding motif R53(10) was observed previously in a cocrystal of 2,4,6‐trichlorophenol, 2,4‐dichlorophenol and dicyclohexylamine. In the title solvated salt, 2C4H12N+·C6H3Cl2O−·(C6H3Cl2O−·C6H4Cl2O)·2C4H8O, five components, namely two tert‐butylammonium cations, one 2,4‐dichlorophenol molecule, one 2,4‐dichlorophenolate anion and one 2,6‐dichlorophenolate anion, are bound by N—H…O and O—H…O hydrogen bonds to form a hydrogen‐bonded ring, with the graph‐set motif R53(10), which is further associated with two pendant tetrahydrofuran molecules by N—H…O hydrogen bonds. The hydrogen‐bonded ring has internal symmetry, with a twofold axis running through the centre of the 2,6‐dichlorophenolate anion, and is isostructural with a previous and related structure formed from 2,4‐dichlorophenol, dicyclohexylamine and 2,4,6‐trichlorophenol. In the title crystal, helical columns are built by the alignment and twisting of the chiral hydrogen‐bonded rings, along and across the c axis, and successive pairs of rings are associated with each other through C—H…π interactions. Neighbouring helical columns are inversely related and, therefore, no chirality is sustained, in contrast to the previous case. 相似文献
7.
Dr. Nabarun Roy Prof. Eric Buhler Prof. Jean‐Marie Lehn 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(27):8814-8820
Materials of supramolecular nature have attracted much attention owing to their interesting features, such as self‐reparability and material robustness, that are imparted by noncovalent interactions to synthetic materials. Among the various structures and synthetic methodologies that may be considered for this purpose, the introduction of extensive arrays of multiple hydrogen bonds allows for the formation of supramolecular materials that may, in principle, present self‐healing behavior. Hydrogen bonded networks implement dynamic noncovalent interactions. Suitable selection of structural units gives access to novel dynamic self‐repairing materials by incrementing the number of hydrogen‐bonding sites present within a molecular framework. Herein, we describe the formation of a tris‐urea based motif giving access to six hydrogen‐bonding sites, easily accessible through reaction of carbohydrazide with an isocyanate derivative. Extension towards the synthesis of multiply hydrogen‐bonded supramolecular materials has been achieved by polycondensation of carbohydrazide with a bis‐isocyanate component derived from poly‐dimethylsiloxane chains. Such materials underwent self‐repair at a mechanically cut surface. This approach gives access to a broad spectrum of materials of varying flexibility by appropriate selection of the bis‐isocyanate component that forms the polymer backbone. 相似文献
8.
Orde Q. Munro Colin Wilson 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(11):o535-o539
The crystal structures of two symmetrical pyridine‐2‐carboxamides, namely N,N′‐(propane‐1,3‐diyl)bis(pyridine‐2‐carboxamide), C15H16N4O2, (I), and N,N′‐(butane‐1,4‐diyl)bis(pyridine‐2‐carboxamide), C16H18N4O2, (II), exhibit extended hydrogen‐bonded sequences involving their amide groups. In (I), conventional bifurcated amide–carbonyl (N—H)...O hydrogen bonding favours the formation of one‐dimensional chains, the axes of which run parallel to [001]. Unconventional bifurcated pyridine–carbonyl C—H...O hydrogen bonding links adjacent one‐dimensional chains to form a `porous' three‐dimensional lattice with interconnected, yet unfilled, voids of 60.6 (2) Å3 which combine into channels that run parallel to, and include, [001]. 4% of the unit‐cell volume of (I) is vacant. Compound (II) adopts a Z‐shaped conformation with inversion symmetry, and exhibits an extended structure comprising one‐dimensional hydrogen‐bonded chains along [100] in which individual molecules are linked by complementary pairs of amide N—H...O hydrogen bonds. These hydrogen‐bonded chains interlock viaπ–π interactions between pyridine rings of neighbouring molecules to form sheets parallel with (010); each sheet is one Z‐shaped molecule thick and separated from the next sheet by the b‐axis dimension [7.2734 (4) Å]. 相似文献
9.
Christina A. Capacci-Daniel Jeffery A. Bertke Shoaleh Dehghan Rupa Hiremath-Darji Jennifer A. Swift 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(9):692-696
Hydrogen bonding between urea functionalities is a common structural motif employed in crystal‐engineering studies. Crystallization of 1,3‐bis(3‐fluorophenyl)urea, C13H10F2N2O, from many solvents yielded concomitant mixtures of at least two polymorphs. In the monoclinic form, one‐dimensional chains of hydrogen‐bonded urea molecules align in an antiparallel orientation, as is typical of many diphenylureas. In the orthorhombic form, one‐dimensional chains of hydrogen‐bonded urea molecules have a parallel orientation rarely observed in symmetrically substituted diphenylureas. 相似文献
10.
Virgil Percec Makoto Obata Jonathan G. Rudick Binod B. De Martin Glodde Tushar K. Bera Sergei N. Magonov V. S. K. Balagurusamy Paul A. Heiney 《Journal of polymer science. Part A, Polymer chemistry》2002,40(20):3509-3533
The synthesis of 2‐ethynyl‐9‐substituted carbazole and 3‐ethynyl‐9‐substituted carbazole monomers containing first‐generation chiral and achiral dendritic (i.e., minidendritic) substituents, 2‐ethynyl‐9‐[3,4,5‐tris(dodecan‐1‐yloxy)benzyl]carbazole (2ECz), 3‐ethynyl‐9‐[3,4,5‐tris(dodecan‐1‐yloxy)benzyl]carbazole (3ECz), 2‐ethynyl‐9‐{3,4,5‐tris[(S)‐2‐methylbutan‐1‐yloxy]benzyl}carbazole (2ECz*), and 3‐ethynyl‐9‐{3,4,5‐tris[(S)‐2‐methylbutan‐1‐yloxy]benzyl}carbazole (3ECz*), is presented. All monomers were polymerized and copolymerized by stereospecific polymerization to produce cis‐transoidal soluble stereoisomers. A structural analysis of poly(2ECz), poly(2ECz*), poly(3ECz), poly(3ECz*), poly(2ECz*‐co‐2ECz), and poly(3ECz*‐co‐3ECz) by a combination of techniques, including 1H NMR, ultraviolet–visible, and circular dichroism spectroscopy, thermal optical polarized microscopy, and X‐ray diffraction experiments, demonstrated that these polymers had a helical conformation that produced cylindrical macromolecules exhibiting chiral and achiral nematic phases. Individual chains of these cylindrical macromolecules were visualized by atomic force microscopy. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3509–3533, 2002 相似文献
11.
Polymeric fibers and microporous films by photo‐crosslinking of triphenylene‐derived liquid crystals
Takuji Hirose Zhe Xu Yuka Kikuchi Masahito Fukushima Kengo Kawamura Yosuke Kaguchi Koichi Kodama Mikio Yasutake 《Journal of polymer science. Part A, Polymer chemistry》2019,57(5):605-612
Two series of photoreactive discotic liquid crystals consisting of a triphenylene core and six cinnamate units with one ( TPC1 n ) or two ( TPC2 n ) n‐alkoxy groups (C nH2n+1O; n = 10–14), respectively, as peripheral groups are synthesized. Both of them are polymerized into fibers up to 2 mm long by UV irradiation in liquid paraffin in the columnar LC temperature ranges. The fiber structures seem to be preconstructed in liquid paraffin. In addition, TPC2 n are shown to form microporous films up to 15 μm in diameter by simply casting the solutions of some solvents followed by drying for several minutes in air at room temperature. Photoirradiation of the films in the LC temperature range converts them to polymeric ones while preserving the microporous and hexagonally ordered structure. From comparison with TPC1 n and the hydrogenated derivative of TPC2 12 , the porous film‐forming property is suggested to result from the combination of the double bond of the cinnamoyl group and the two long alkoxy chains on the phenyl ring. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 605–612 相似文献
12.
Guoxia Jin Jia Wang Qidi Wu Zheng Han Jianping Ma 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(12):1089-1095
Two new ZnII coordination polymers, namely, catena‐poly[[dibromidozinc(II)]‐μ‐[3,6‐bis(pyridin‐4‐yl)phenanthrene‐9,10‐dione‐κ2N:N′]], [ZnBr2(C24H14N2O2)]n, (1), and poly[[bromido[μ3‐10‐hydroxy‐3,6‐bis(pyridin‐4‐yl)phenanthren‐9‐olato‐κ3N:N′:O9]zinc(II)] hemihydrate], {[ZnBr(C24H15N2O2)]·0.5H2O}n, (2), have been synthesized through hydrothermal reaction of ZnBr2 and a 60° angular phenanthrenedione‐based linker, i.e. 3,6‐bis(pyridin‐4‐yl)phenanthrene‐9,10‐dione, in different solvent systems. Single‐crystal analysis reveals that polymer (1) features one‐dimensional zigzag chains connected by weak C—H...π and π–π interactions to form a two‐dimensional network. The two‐dimensional networks are further stacked in an ABAB fashion along the a axis through C—H...O hydrogen bonds. Layers A and B comprise left‐ and right‐handed helical chains, respectively. Coordination polymer (2) displays a wave‐like two‐dimensional layered structure with helical chains. In this compound, there are two opposite helical –Zn–HL– chains [HL is 10‐hydroxy‐3,6‐bis(pyridin‐4‐yl)phenanthren‐9‐olate] in adjacent layers. The layers are packed in an ABAB sequence and are further connected through O—H...Br and O—H...O hydrogen‐bond interactions to form a three‐dimensional framework. In (1) and (2), the mutidentate L and HL ligands exhibits different coordination modes. 相似文献
13.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(8):2194-2197
A new perylene bisimide (PBI) dye self‐assembles through hydrogen bonds and π–π interactions into J‐aggregates that in turn self‐organize into liquid‐crystalline (LC) columnar hexagonal domains. The PBI cores are organized with the transition dipole moments parallel to the columnar axis, which is an unprecedented structural organization in π‐conjugated columnar liquid crystals. Middle and wide‐angle X‐ray analyses reveal a helical structure consisting of three self‐assembled hydrogen‐bonded PBI strands that constitute a single column of the columnar hexagonal phase. This remarkable assembly mode for columnar liquid crystals may afford new anisotropic LC materials for applications in photonics. 相似文献
14.
Assembly of a New Cadmium(II)‐bis(Triazole) Coordination Polymer Templated by Keggin Polyoxometalate
Through utilizing the flexible bis(triazole) ligand 1,3‐bis(1,2,4‐triazol‐1‐y1)propane (btp), the new Keggin POM‐templated compound, [Cd2(H2O)2(btp)4(SiMo12O40)] · 2H2O ( 1 ), was synthesized under hydrothermal conditions. It was characterized by single‐crystal X‐ray diffraction, elemental analysis, IR spectroscopy, thermogravimetric analysis, photoluminescence spectroscopy, and cyclic voltammetry. In compound 1 , the [SiMo12O40]4– polyanions serving as template induce the Cd–bis(triazole) coordination polymer to construct a ladder‐like chain. In the 1D chain, two btp ligands act as “middle rails”. The template polyanions insert into the grids of the 1D chain. Furthermore, these chains can construct a 3D supramolecular structure through hydrogen bondings. 相似文献
15.
Helical Polyacetylene‐Based Switchable Chiral Columnar Phases: Frustrated Chain Packing and Two‐Way Shape Actuator 下载免费PDF全文
Jun Wang Dr. Xiao‐Qing Liu Dr. Xiang‐Kui Ren Dr. Ben Zhang Prof. Dr. Shuang Yang Yu Cao Prof. Dr. Feng Liu Prof. Dr. Bernard Lotz Prof. Dr. Er‐Qiang Chen 《化学:亚洲杂志》2016,11(17):2387-2391
Chiral columns formed by a helical cis‐polyphenylacetylene (PPA) derivative P1 are reversibly switched during a phase transition between two chiral columnar phases: the frustrated Φh3D‐SL phase containing four chains at low temperature and a hexagonal columnar phase Φh at high temperature, accompanied by a simultaneous conformational change. The helix–helix transition along the PPA backbone during the Φh3D‐SL‐Φh transition makes the uniaxially oriented P1 capable of reversibly and reproducibly elongating (132 %) upon heating and contracting upon cooling, exhibiting the behavior of a two‐way shape actuator. 相似文献
16.
The crystal structures of N‐aryl‐1,2,3,4‐tetrahydro‐3,3‐dimethyl‐2,4‐quinolinediones bearing methoxy‐ ( 1 ), methyl‐ ( 2 ), and chloro‐ ( 3 ) substituents in 2′‐position of the phenyl ring have been determined by X‐ray crystal structure analysis. The heterocyclic ring in 1–3 adopts an envelope conformation, with the smallest ring puckering in the ortho‐chloro derivative 3 . The N‐aryl ring is almost perpendicular with respect to the quinoline‐2,4‐dione ring. The corresponding dihedral angle values are 83.2(1)°, 80.0(9)°, and 83.4(2)° in 1, 2 and 3 , respectively. The hydrogen bond of C H⋅⋅⋅O type joins the molecules of the ortho‐methoxy derivative 1 into dimers. The supramolecular structure also contains two C H⋅⋅⋅π interactions that link the hydrogen‐bonded dimers into sheets. In ortho‐methyl derivative 2 , one C H⋅⋅⋅π interaction generates infinite chains, whereas two C H⋅⋅⋅O hydrogen bonds and three C H⋅⋅⋅π interactions in the ortho‐chloro derivative 3 form three‐dimensional framework. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:325–331, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20436 相似文献
17.
J. D. Sudha C. K. S. Pillai 《Journal of polymer science. Part A, Polymer chemistry》2003,41(2):335-346
Hydrogen‐bonded aromatic–aliphatic polyester–amides (PEAs) were prepared by solution/melt polycondensation of aromatic–aliphatic amidodiols 1,4‐bis(4‐hydroxybutyramide)benzene (BHBB), 1,4‐bis(5‐hydroxy pentamide)benzene, 1,4‐bis(6‐hydroxyhexamide)benzene, 1,4‐bis(4‐hydroxybutyramidexylene), 1,4‐bis(5‐hydroxypentamidexylene, 1,4‐bis(4‐hydroxybutyramide)benzene, and 1,4‐bis(6‐hydroxyhexamidexylene) with terephthaloyl chloride/dimethyl terephthalate. Aromatic–aliphatic amido diols were prepared by the aminolysis of γ‐butyrolactone, δ‐valerolactone, and ?‐caprolactone with aromatic diamines such as paraphenylene diamine and paraxylene diamine. The monomers and polymers were characterized by chemical analysis (hydroxyl value and elemental analysis), Fourier transform infrared spectroscopy, 1H NMR, and 13C NMR. The thermal‐ and phase‐transition behaviors of the polymers were investigated by differential scanning calorimetry in combination with hot‐stage optical microscopy. Crystallinity of polymers was examined with wide‐angle X‐ray diffraction. The polymers exhibited liquid crystallinity with layered structures formed by self‐organization of the hetero intermolecular hydrogen‐bonded networks indicating smectic phases except for PEAs prepared from BHBB. The hydrogen atom of the phenyl‐substituent group forces the neighboring carbonyl groups out of plane of the rings preventing formation of layered structures in the case of BHBB. The PEAs retained intermolecular hydrogen bonding even in the mesomorphic state, and variations in the hydrogen‐bonded lamellae/micelles might be responsible for the variations from one smectic to another texture. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 335–346, 2003 相似文献
18.
Supramolecular Columnar Liquid Crystals with Tapered‐Shape Simple Pyrazoles Obtained by Efficient Henry/Michael Reactions 下载免费PDF全文
Hugo Blanco Verónica Iguarbe Prof. Joaquín Barberá Prof. José Luis Serrano Dr. Anabel Elduque Dr. Raquel Giménez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(14):4924-4930
A straightforward synthesis of mesogenic pyrazoles starting from benzaldehydes by a combination of efficient Henry and Michael reactions led to novel supramolecular liquid crystals. The mesogens are fluorescent 3,5‐dimethyl‐4‐(di or trialkoxyphenyl)pyrazoles and, in spite of the tapered shape of these molecules and their structural simplicity (only one phenyl ring), columnar liquid‐crystal phases were formed that are stable at room temperature. The self‐assembled structure was studied by XRD and the columnar cross section contains two molecules on average with an antiparallel arrangement of pyrazoles interacting through hydrogen bonds. In contrast, the single‐crystal structure of a trimethoxy analog did not show hydrogen‐bonded pyrazoles but chains of head‐to‐tail arranged molecules. 相似文献
19.
The reaction of 4‐phenyl‐2‐aminothiazole or 2‐amino pyridine with α‐bromo acetic (–)‐menthyl ester ( 2c ) yields new N‐alkyl cycloimmonium bromides ( 1c , 3 ) with the chiral (–)‐menthyl substituent, which were isolated and fully characterized by 1H and 13C NMR spectroscopy for the first time. In addition, starting from 4‐phenyl‐2‐aminothiazole, two further N‐alkyl cycloimmonium bromides ( 1a , 1b ) were prepared. The molecular and crystal structures of all three thiazole derived N‐alkyl cycloimmonium bromides ( 1a – c ) were determined by single‐crystal X‐ray diffraction. In all cases the crystal structures are dominated by N–H ··· Br hydrogen bonds, which results in the formation of an extensive hydrogen bonded network in the crystal. Interestingly, in all structures S ··· Br– distances shorter than the sum of the van der Waals radii are observed. 相似文献
20.
Alexander Briceo Reinaldo Atencio Raquel Gil Alejandra Nobrega 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(8):o441-o444
The structure of trans‐3‐(3‐pyridyl)acrylic acid, C8H7NO2, (I), possesses a two‐dimensional hydrogen‐bonded array of supramolecular ribbons assembled via heterodimeric synthons between the pyridine and carboxyl groups. This compound is photoreactive in the solid state as a result of close contacts between the double bonds of neighbouring molecules [3.821 (1) Å] along the a axis. The crystal structure of the photoproduct, rctt‐3,3′‐(3,4‐dicarboxycyclobutane‐1,2‐diyl)dipyridinium dichloride, C16H16N2O42+·2Cl−, (II), consists of a three‐dimensional hydrogen‐bonded network built from crosslinking of helical chains integrated by self‐assembly of dipyridinium cations and Cl− anions via different O—H...Cl, C—H...Cl and N+—H...Cl hydrogen‐bond interactions. 相似文献