Unprecedented synthesis of 1,3-dimethylcyclobutadiene in the solid state and aqueous solution

Cyclobutadiene ( CBD ), the smallest cyclic hydrocarbon bearing conjugated double bonds, has long intrigued chemists because of its chemical characteristics. The question of whether the molecule could be prepared at all has been answered, but the parent compound and its unperturbed derivatives have eluded crystallographic characterization or synthesis “in water”. Different approaches have been used to generate and to trap cyclobutadiene in a variety of confined environments: a) an Ar matrix at cryogenic temperatures, b) a hemicarcerand cage enabling the characterization by NMR spectroscopy in solution, and c) a crystalline guanidinium–sulfonate–calixarene G₄C matrix that is stable enough to allow photoreactions in the solid state. In the latter case, the 4,6‐dimethyl‐α‐pyrone precursor, Me₂1 , has been immobilized in a guanidinium–sulfonate–calixarene G₄C crystalline network through a combination of non‐covalent interactions. UV irradiation of the crystals transforms the entrapped Me₂1 into a 4,6‐dimethyl‐Dewar‐β‐lactone intermediate, Me₂2 , and rectangular‐bent 1,3‐dimethylcyclobutadiene, Me₂CBD^R , which are sufficiently stable under the confined conditions at 175 K to allow a conventional structure determination by X‐ray diffraction. Further irradiation drives the reaction towards Me₂3&Me₂CBD^S /CO₂ (63.7 %) and Me₂CBD^R (37.3 %) superposed crystalline architectures and the amplification of Me₂CBD^R . The crystallographic models are supported by additional FTIR and Raman experiments in the solid state and by ¹H NMR spectroscopy and ESI mass spectrometry experiments in aqueous solution. Amazingly, the 4,6‐dimethyl‐Dewar‐β‐lactone, Me₂2 , the cyclobutadiene‐carboxyl zwitterion, Me₂3 , and 1,3‐dimethylcyclobutadiene, Me₂CBD , were obtained by ultraviolet irradiation of an aqueous solution of G₄C{Me₂1} . 1,3‐Dimethylcyclobutadiene is stable in water at room temperature for several weeks and even up to 50 °C as demonstrated by ¹H NMR spectroscopy.     

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.     

A new two‐dimensional ZnII coordination polymer based on 1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene and 5‐nitrobenzene‐1,3‐dicarboxylic acid: synthesis,crystal structure and physical properties

A novel two‐dimensional (2D) Zn^II coordination framework, poly[[μ‐1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene](μ‐5‐nitrobenzene‐1,3‐dicarboxylato)zinc(II)], [Zn(C₈H₃NO₆)(C₁₄H₁₄N₄)]_n or [Zn(NO₂‐BDC)(1,3‐BMIB)]_n [1,3‐BMIB is 1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene and NO₂‐H₂BDC is 5‐nitrobenzene‐1,3‐dicarboxylic acid], has been prepared and characterized by IR, elemental analysis, thermal analysis and single‐crystal X‐ray diffraction. Single‐crystal X‐ray diffraction analysis revealed that the compound is a new 2D polymer with a 6³ topology parallel to the (10) crystal planes based on left‐handed helices, right‐handed helical NO₂‐BDC–Zn chains and [Zn₂(1,3‐BMIB)₂]_n clusters. In the crystal, adjacent layers are further connected by C—H…O hydrogen bonds, C—H…π interactions, C—O…π interactions and N—O…π interactions to form a three‐dimensional structure in the solid state. In addition, the compound exhibits strong fluorescence emissions in the solid state at room temperature.     

Syntheses,Crystal Structures,and Fluorescence Properties of Two Transition Metal‐Organic Coordination Polymers Based on 4,4′‐Dimethyl‐2,2′‐bipyridine

Two transition metal‐organic coordination polymers, [Mn₂(1,3‐bdc)₂(Me₂bpy)₂] · Me₂bpy ( 1 ) and [Co(4,4′‐oba)(Me₂bpy)] ( 2 ) were hydrothermally synthesized and structurally characterized by elemental analysis, IR spectroscopy, TG, and single‐crystal X‐ray diffraction [1,3‐H₂bdc = benzene‐1,3‐dicarboxylic acid, H₂oba = 4,4′‐oxybis(benzoic acid) Me₂bpy = 4,4′‐dimethyl‐2,2′‐bipyridine]. Compound 1 crystallizes in the orthorhombic system, space group P2₁2₁2₁, with a = 23.371(5), b = 14.419(3), and c = 14.251(3) Å. Compound 2 crystallizes in the monoclinic system, space group P2₁/c, with a = 7.4863(15), b = 18.272(4), c = 16.953(5) Å, and β = 107.44(3)°. The crystal structure of complex 1 is a wave‐like layer with central Mn²⁺ atoms bridged by 1,3‐bdc ligands, whereas the structure of compound 2 presents a ladder chain of hexacoordinate Co²⁺ atoms, in which the metal atoms are bridged by 4,4′‐oba ligands and decorated by Me₂bpy ligands. The two compounds are further extended into 3D supramolecular structures through π–π stacking interactions. Additionally, the compounds show intense fluorescence in solid state at room temperature.     

固相β-环糊精包结物诱导7-羟基-2-甲氧基-2-甲基色满的不对称合成

研究了室温下间苯二酚和甲基乙烯基酮分别与β-环糊精（ β-CD）形成包结物后的几种不同固相反应,结果表明包结物A（间苯二酚/β-CD）与包结物B（甲基乙烯基酮/β-CD）反应能够很好地得到目的产物,产率及ee值分别为82.8%和78.4%;间苯二酚与包结物B反应仅得到低光学活性产物（ee值为19.5%）;包结物A与甲基乙烯基酮反应却没有得到手性目的产物。以熔点、X-粉末衍射、固相核磁碳谱及ROESY多种方法对所形成的包结物进行了表征,包结物中主客体的比例（1：1）通过¹H NMR (400 MHz)得以确定,文章对固相环加成反应的机制也进行了初步探讨。     

A Constrained Disorder Refinement: “Reinvestigation of “Single‐Crystal X‐ray Structure of 1,3‐Dimethylcyclobutadiene” by M. Shatruk and I. V. Alabugin”

Shatruk and Alabugin propose an alternative structural model for the observed electron density that we have attributed to the photochemical formation of 1,3‐dimethylcyclobutadiene in a protective solid crystalline matrix. The main criticism from Shatruk and Alabugin concerns the modeling of the disorder in the calixarene cavity and in particular the neglect of a residual electron density close to the O1 atom. We published (Chem. Eur. J. 2011 , 17, 10021) our opinion concerning this “ignored peak” in the Supporting Information of the paper. The current response to the Correspondence demonstrates that Shatruk and Alabugin have over‐modeled our data by assigning a small electron density peak, which is hardly more than the density corresponding to a hydrogen atom, to an under‐occupied oxygen site, using inappropriate refinement contraints.     

A Novel,One‐Pot Four‐Component Route to 2′‐Thioxo‐2′,3′‐dihydrospiro[indole‐3,6′‐[1,3]thiazin]‐2‐one Derivatives

An efficient route to 2′,3′‐dihydro‐2′‐thioxospiro[indole‐3,6′‐[1,3]thiazin]‐2(1H)‐one derivatives is described. It involves the reaction of isatine, 1‐phenyl‐2‐(1,1,1‐triphenyl‐λ⁵‐phosphanylidene)ethan‐1‐one, and different amines in the presence of CS₂ in dry MeOH at reflux (Scheme 1). The alkyl carbamodithioate, which results from the addition of the amine to CS₂, is added to the α,β‐unsaturated ketone, resulting from the reaction between 1‐phenyl‐2‐(1,1,1‐triphenyl‐λ⁵‐phosphanylidene)ethan‐1‐one and isatine, to produce the 3′‐alkyl‐2′,3′‐dihydro‐4′‐phenyl‐2′‐thioxospiro[indole‐3,6′‐[1,3]thiazin]‐2(1H)‐one derivatives in excellent yields (Scheme 2). Their structures were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and by elemental analyses.     

Isotactic rac‐Lactide Polymerization with Copper Complexes: The Influence of Complex Nuclearity

Diiminopyrrolide copper alkoxide complexes, LCuOR (OR¹=N,N‐dimethylamino ethoxide, OR²=2‐pyridyl methoxide), are active for the polymerization of rac‐lactide at ambient temperature in benzene to yield polymers with M_w/M_n=1.0–1.2. X‐ray diffraction studies showed bridged dinuclear complexes in the solid state for both complexes. While LCuOR¹ provided only atactic polylactide, LCuOR² produced partially isotactic polylactide (P_m=0.7). The difference in stereocontrol is attributed to a dinuclear active species for LCuOR² in contrast to a mononuclear species for LCuOR¹.     

The first example of a two‐coordinated AuI atom bonded to an FeII atom and an N‐heterocyclic carbene (NHC) ligand

The aurophilicity exhibited by Au^I complexes depends strongly on the nature of the supporting ligands present and the length of the Au–element (Au—E) bond may be used as a measure of the donor–acceptor properties of the coordinated ligands. A binuclear iron–gold complex, [1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene‐2κC²]dicarbonyl‐1κ²C‐(1η⁵‐cyclopentadienyl)gold(I)iron(II)(Au—Fe) benzene trisolvate, [AuFe(C₅H₅)(C₂₇H₃₆N₂)(CO)₂]·3C₆H₆, was prepared by reaction of K[CpFe(CO)₂] (Cp is cyclopentadienyl) with (NHC)AuCl [NHC = 1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene]. In addition to the binuclear complex, the asymmetric unit contains three benzene solvent molecules. This is the first example of a two‐coordinated Au atom bonded to an Fe and a C atom of an N‐heterocyclic carbene.     

Reduction of Thiocarbonyl Compounds with Lithium Diisopropylamide

Treatment of 4,4‐disubstituted 2‐phenyl‐1,3‐thiazole‐5(4H)‐thiones with lithium diisopropylamide (LDA; LiNⁱPr₂) in THF at ?78° yielded the corresponding 1,3‐thiazole‐5(4H)‐thioles in moderate yields. Sequential treatment with LDA and MeI under the same conditions led to the 5‐methylsulfanyl derivatives. Similarly, reaction of some cycloalkanethiones as well as diaryl thioketones with LDA and MeI gave cycloalkyl methyl sulfides and diarylmethyl methyl sulfides, respectively. A reaction mechanism via H transfer from LDA to the thiocarbonyl C‐atom via a six‐membered transition state is proposed for this unprecedented reduction of the C?S bond.     

Synthesis of Fluorescent 2,6‐Dicyano‐3,5‐Disubstituted Anilines Using Cellulose Sulfuric Acid in Aqueous Media

The synthesis of some fluorescent 2,6‐dicyano‐3,5‐disubstituted anilines using cellulose sulfuric acid (Cellulose‐SA) as an environmentally benign catalyst in H₂O is described. The one‐pot reaction of 1,3‐diketone and three equiv. of malononitrile was carried out in the presence of one equiv. of a secondary amine, Cellulose‐SA as catalyst, and H₂O as solvent. The photophysical properties (λ_Abs., λ_Flu.) of the synthesized compounds in CH₂Cl₂, MeCN, and MeOH have been measured. The emission spectra of the new compounds in the solid state are also reported.     

Synthesis,crystal structure and photophysical properties of 1,4‐bis(1,3‐diazaazulen‐2‐yl)benzene: a new π building block

A dimerized 1,3‐diazaazulene derivative, namely 1,4‐bis(1,3‐diazaazulen‐2‐yl)benzene [or 2,2′‐(1,4‐phenylene)bis(1,3‐diazaazulene)], C₂₂H₁₄N₄, (I), has been synthesized successfully through the condensation reaction between 2‐methoxytropone and benzene‐1,4‐dicarboximidamide hydrochloride, and was characterized by ¹H NMR and ¹³C NMR spectroscopies, and ESI–MS. X‐ray diffraction analysis reveals that (I) has a nearly planar structure with good π‐electron delocalization, indicating that it might serve as a π building block. The crystal belongs to the monoclinic system. One‐dimensional chains were formed along the a axis through π–π interactions and adjacent chains are stabilized by C—H…N interactions, forming a three‐dimensional architecture. The solid emission of (I) in the crystalline form exhibited a 170 nm red shift compared with that in the solution state. The observed optical bandgap for (I) is 3.22 eV and a cyclic voltammetry experiment confirmed the energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The calculated bandgap for (I) is 3.37 eV, which is very close to the experimental result. In addition, the polarizability and hyperpolarizability of (I) were appraised for its further application in second‐order nonlinear optical materials.     

A twofold interpenetrating three‐dimensional CdII coordination framework: poly[[μ2‐1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene](μ3‐5‐nitrobenzene‐1,3‐dicarboxylato)cadmium(II)]

A twofold interpenetrating three‐dimensional Cd^II coordination framework, [Cd(C₈H₃NO₆)(C₁₄H₁₄N₄)]_n, has been prepared and characterized by IR spectroscopy, elemental analysis, thermal analysis and single‐crystal X‐ray diffraction. The asymmetric unit consists of a divalent Cd^II atom, one 1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene (1,3‐BMIB) ligand and one fully deprotonated 5‐nitrobenzene‐1,3‐dicarboxylate (NO₂‐BDC²⁻) ligand. The coordination sphere of the Cd^II atom consists of five O‐donor atoms from three different NO₂‐BDC²⁻ ligands and two imidazole N‐donor atoms from two different 1,3‐BMIB ligands, forming a distorted {CdN₂O₅} pentagonal bipyramid. The NO₂‐BDC ligand links three Cd^II atoms via a μ₁‐η¹:η¹ chelating mode and a μ₂‐η²:η¹ bridging mode. The title compound is a twofold interpenetrating 3,5‐connected network with the {4².6⁵.8³}{4².6} topology. In addition, the compound exhibits fluorescence emissions in the solid state at room temperature.     

Reply to A Computational Evaluation of the Evidence for the Synthesis of 1,3‐Dimethylcyclobutadiene in Solid State and Aqueous Solution—Beyond the Experimental Reality

Following earlier reports on the photochemical synthesis of 1,3‐dimethylcyclobutadiene 8 , 10 in a protective host matrix, theoretical calculations for the formation of that adduct have been recently performed by Rzepa. 13 The author formulated criticisms based mainly on density functional theory calculations of ¹H NMR spectra. According to Rzepa the calculated spectra do not correspond with our measured spectra, which leads him to the conclusion that our interpretation is wrong, and that mainly cyclobutadiene has not been stabilized or even synthesized; we believe, however, that the initial model that Rzepa used for his calculations does not correspond to chemical reality or is at the very least a crude simplification of it, which implies that his calculations cannot match, in every point, our experimental spectra. Rzepa′s simplified models might be ‘reasonable’ from the theoretical point of view; however, in the case of assessment in the solid state, the theoretical setup does not force the system to preserve the confined stabilizing space defined by the crystalline matrix for encapsulated hosts in the solid state. Inversely, in the case of solution modeling, the theoretical setup is too rigid to properly assess the complex equilibria occurring in solution and to accurately determine the NMR spectra of exchanging species in solution. The inconsistency between our experimental results and the results of the theoretical models proposed by Rzepa is such that his conclusions are considered to be too far from experimental reality. Accurate modeling taking in account “reasonable” experimental details would be a worthwhile endeavor.     

Two new CoII coordination polymers with multifunctional 5‐amino‐2,4,6‐tribromoisophthalic acid and flexible isomeric bis(imidazole) ligands: preparation,crystal structure and characterization

Two new Co^II coordination polymers (CPs), namely, catena‐poly[[[(5‐amino‐2,4,6‐tribromobenzene‐1,3‐dicarboxylato‐κO)aquacobalt(II)]‐bis[μ‐1,3‐bis(imidazol‐1‐ylmethyl)benzene‐κ²N:N′]] 4.75‐hydrate], {[Co(C₈H₂Br₃NO₄)(C₁₄H₁₄N₄)₂(H₂O)]·4.75H₂O}_n, (1), and poly[(μ‐5‐amino‐2,4,6‐tribromobenzene‐1,3‐dicarboxylato‐κ²O¹:O³)[μ‐1,2‐bis(imidazol‐1‐ylmethyl)benzene‐κ²N:N′]cobalt(II)], [Co(C₈H₂Br₃NO₄)(C₁₄H₁₄N₄)]_n, (2), have been synthesized successfully by the assembly of multifunctional 5‐amino‐2,4,6‐tribromoisophthalic acid (H₂ATBIP) and Co^II ions in the presence of the flexible isomeric bis(imidazole) ligands 1,3‐bis(imidazol‐1‐ylmethyl)benzene (mbix) and 1,2‐bis(imidazol‐1‐ylmethyl)benzene (obix). The isomeric mbix and obix ligands have a big influence on the structures of CPs (1) and (2). CP (1) is composed of chains of nanometre‐sized elliptical rings, in which the Co^II atom exhibits a distorted octahedral coordination geometry and ATBIP²⁻ acts as a monodentate ligand. Two adjacent chains are interlinked by π–π stacking interactions and hydrogen bonds, resulting in a supramolecular double chain. Hydrogen‐bonded R₈⁶(16) rings extend adjacent supramolecular double chains into a two‐dimensional supramolecular layer. Halogen bonding and a hydrogen‐bonded R₄²(8) ring further link the two‐dimensional supramolecular layers, leading to the formation of a three‐dimensional supramolecular network. The Co^II ion in CP (2) is tetracoordinated, exhibiting a distorted tetrahedral configuration. The ATBIP²⁻ ligand exhibits a bis(monodentate) coordination bridging mode, linking adjacent Co^II ions into zigzag chains, which are further bridged by the auxiliary bridging obix ligand, resulting in a two‐dimensional (4,4) topological network. Interlayer hydrogen and halogen–halogen bonding further extend the two‐dimensional layers into a three‐dimensional supramolecular network. A detailed analysis of the solid‐state UV–Vis–NIR diffuse‐reflectance spectra of (1) and (2) indicates that a wide optical band gap exists in both (1) and (2). CP (1) exhibits an irreversible dehydration–rehydration behaviour.     

pH‐Controlled Molecular Switches and the Substrate‐Directed Self‐Assembly of Molecular Capsules with a Calix[4]pyrrole Derivative

10α,20α‐Bis(4‐nitrophenyl)calix[4]pyrrole ( 1 ) forms 1:1 complexes with anions of selected aromatic hydroxy acids in which the host orientation within the guest is controlled by a change in the pH value. Some bis‐anionic guests, including those obtained from 4‐hydroxybenzoic acid, 1,4‐ and 1,3‐benzenedicarboxylic acids, induce the self‐assembly of molecular capsules involving two molecules of the receptor. ¹H NMR data and solid‐state structures of the 1:1 complex of 1 with p‐C₆H₄(COOH)(COO^?)⁺NMe₄ and the 2:1 capsule [( 1 )₂m‐C₆H₄(COO^?)₂(⁺NMe₄)₂] provide structural details in solution and in the solid state.     

Two new isostructural mercury(II) complexes involving the N‐heterocyclic 1‐[(benzotriazol‐1‐yl)methyl]‐1H‐1,3‐imidazole ligand: syntheses,structures and properties

The unsymmetrical N‐heterocyclic ligand 1‐[(benzotriazol‐1‐yl)methyl]‐1H‐1,3‐imidazole (bmi) has three potential N‐atom donors and can act in monodentate or bridging coordination modes in the construction of complexes. In addition, the bmi ligand can adopt different coordination conformations, resulting in complexes with different structures due to the presence of the flexible methylene spacer. Two new complexes, namely bis{1‐[(benzotriazol‐1‐yl)methyl]‐1H‐1,3‐imidazole‐κN ³}dibromidomercury(II), [HgBr₂(C₁₀H₉N₅)₂], and bis{1‐[(benzotriazol‐1‐yl)methyl]‐1H‐1,3‐imidazole‐κN ³}diiodidomercury(II), [HgI₂(C₁₀H₉N₅)₂], have been synthesized through the self‐assembly of bmi with HgBr₂ or HgI₂. Single‐crystal X‐ray diffraction shows that both complexes are mononuclear structures, in which the bmi ligands coordinate to the Hg^II ions in monodentate modes. In the solid state, both complexes display three‐dimensional networks formed by a combination of hydrogen bonds and π–π interactions. The IR spectra and PXRD patterns of both complexes have also been recorded.     

A One‐Pot Synthesis of 1,3‐Dihydro‐1,3,3‐tris(perfluoroalkyl)isobenzofuran‐1‐olates and Their Complete NMR Spectroscopic Analysis on the Basis of 1D and 2D Experiments

A convenient synthesis of the 1,3‐dihydro‐1,3,3‐tris(perfluoroalkyl)isobenzofuran‐1‐ols 3a , b was elaborated starting from commercially available phthaloyl dichloride and trimethyl(perfluoroalkyl)silanes (Me₃SiR_f) 1a , b (R_f=CF₃, C₂F₅) in the presence of a fluoride source (Schemes 1 and 3). In a reaction analogous to alkyl Grignard reagents, double chloride substitution by two perfluoroalkyl groups and subsequent addition of one perfluoroalkyl group with concomitant ring closure led to this new class of compounds (Scheme 2). The syntheses of the alcohols and some alcoholates, as well as of the corresponding trimethylsilyl ethers are described. A combination of special 1D and 2D NMR experiments allowed the assignment of all atoms of the new compounds. The solid‐state structure of 1,3‐dihydro‐1,3,3‐tris(trifluoromethyl)isobenzofuran‐1‐ol ( 3a ) was elucidated by X‐ray diffraction methods.     

A new two‐dimensional ZnII coordination polymer constructed by a multidentate N‐heterocyclic ligand and 5‐carboxybenzene‐1,3‐dicarboxylate

In the coordination polymer, poly[[{μ‐1‐[(1H‐benzimidazol‐2‐yl)methyl]‐1H‐imidazole‐κ²N:N′}(μ‐5‐carboxybenzene‐1,3‐dicarboxylato‐κ²O¹:O³)zinc(II)] dimethylformamide monosolvate pentahydrate], {[Zn(C₉H₄O₆)(C₁₁H₁₀N₄)]·C₃H₇NO·5H₂O}_n, the Zn^II ion is coordinated by two N atoms from two symmetry‐related 1‐[(1H‐benzimidazol‐2‐yl)methyl]‐1H‐imidazole (bmi) ligands and two O atoms from two symmetry‐related 5‐carboxybenzene‐1,3‐dicarboxylate (Hbtc²⁻) ligands in a slightly distorted tetrahedral geometry. The Zn^II ions are bridged by Hbtc²⁻ and bmi ligands, leading to a 4‐connected two‐dimensional network with the topological notation (4⁴.6²). Adjacent layers are further connected by 12 kinds of hydrogen bonds and also by π–π interactions, resulting in a three‐dimensional supramolecular architecture in the solid state.     

One‐Pot,Pseudo‐Five‐Component Synthesis of Bis[2‐(arylimino)‐1,3‐thiazolidin‐4‐ones]

Synthesis and characterization of bis[2‐(arylimino)‐1,3‐thiazolidin‐4‐ones] are described. The one‐pot, pseudo‐five‐component reaction of an aliphatic diamine, isothiocyanatobenzene, and dialkyl but‐2‐ynedioate at room temperature in anhydrous CH₂Cl₂ gives the title compound in relatively high yield. Under the same conditions, aromatic 1,2‐diamines yield 2‐(arylimino)‐N‐(enaminoaryl)‐1,3‐thiazolidin‐4‐ones in a pseudo‐four‐component reaction. Their structures were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and by elemental analyses. A plausible mechanism for this type of cyclization is proposed (Scheme 3).