Host–Guest Complexation Using Pillar[5]arene Crystals: Crystal-Structure Dependent Uptake,Release, and Molecular Dynamics of an Alkane Guest

Host–guest complexation has been mainly investigated in solution, and it is unclear how guest molecules access the assembled structures of host and dynamics of guest molecules in the crystal state. In this study, we studied the uptake, release, and molecular dynamics of n-hexane vapor in the crystal state of pillar[5]arenes bearing different substituents. Pillar[5]arene bearing 10 ethyl groups yielded a crystal structure of herringbone-type 1:1 complexes with n-hexane, whereas pillar[5]arene with 10 allyl groups formed 1:1 complexes featuring a one-dimensional (1D) channel structure. For pillar[5]arene bearing 10 benzyl groups, one molecule of n-hexane was located in the cavity of pillar[5]arene, and another n-hexane molecule was located outside of the cavity between two pillar[5]arenes. The substituent-dependent differences in molecular arrangement influenced the uptake, release, and molecular dynamics of the n-hexane guest. The substituent effects were not observed in host–guest chemistry in solution, and these features are unique for the crystal state host–guest chemistry of pillar[5]arenes.     

Synthesis and Conformational Properties of Bis（calix [4] arene）

The bis(calix [4] arene)3 was synthesized in moderate yield by the reaction of p-tert-butylcalix [4] arene (1) with 1,4-bis(chloromethyl) benzene (2). The conformation of all alkylated product 4 was investigated by the variable-temperature ^1H-NMR.     

Synthesis and properties of p-per fluoroalkylcalix [4]arenes

p-Perfluoroalkylealix[4]arenes were prepared readily from the reaction of calix-[4]arene with perfluoroalkyl iodides in the presence of sodium dithionite or sodium hydroxy-methanesulfinate under mild conditions,These fluorine-containing calixarenes showed bettersolubilities in common organic solvents as compared to their nonperfluoroalkylation analogand formed inclusion complexes with many neutral molecules as well as fluorocarbons.     

Synthesis and Chiroptical Properties of Quinoxaline-Fused Polyaza[5]–[7]helicenes with Orange-Color CPL Emissions

We achieved a two-type synthesis of quinoxaline-fused polyaza[5]- and [7]helicenes through consecutive N−H/C−H coupling with a hypervalent iodine reagent as a key reaction. By fusing electron-deficient quinoxaline, these polyazahelicenes constitute an efficient donor-acceptor type of molecule with absorption edges that reach up to approximately 650 nm. Evaluating the chiroptical properties reveals that the polyazahelicene exhibits a rare orange circularly polarized glow with a luminescence dissymmetry factor (g_lum value) of 0.003.     

Smart Materials Based on Synthetic Host Molecules: The Role of Host–Guest Chemistry in the Fabrication and Application

Stimuli-responsive or smart materials have recently shown a significant impact on the frontier of material science and engineering. The exponential development of synthetic host molecules (SHMs) over the last decades and their corresponding host–guest chemistry, have empowered researchers with new opportunities to design and construct tailored or guest-specific smart materials. In this Minireview, we present the recent advancements in synthetic host based smart materials, ranging from the fabrication strategies to the state-of-art applications including adsorption, separation, luminescence, self-healing and actuation. The role that the host–guest chemistry plays in these systems is highlighted throughout to give a better prospective of the available possibilities for emerging materials of future economies.     

Synthesis, Characterization and Catalytic Properties of Zeolite [B, Al, Ga, Fe]-ZSM-5

Zeolite [B,Al, Ga, Fe]-ZSM-5, containing several heteroatoms, was synthesized for the first time under. hydrothermal conditions. Characterization of the sample using various techniques such as XRD, IR, ESR, TG-DTA, SEM and XRF indicates that the heteroatoms are located in the framework, similar to the situations of the heteroatoms present in the zeolites [B]-, [Al]-, [Ga]- and [Fe]-ZSM-5. The study of the catalytic properties for reactions of cracking and dehydrogenation of ethylbenzene reveals that the heteroatoms function independently and there are no mutual interactions between the heteroatoms.     

Structure–Properties Relations in Werner β-[Ni(NCS)2(4-MePy)4] Clathrates. Part 2. Host–Host Interactions as a Function of the Guest Molecular Size and Shape and the Amount of Absorbed Guest Compound

Careful analysis of changes in the geometry of the host lattice structure on inclusion of different guest molecules was performed for 11 -[Ni(NCS)₂(4-methylpyridine)₄] clathrates reported in the literature, and specific features were established for the geometry of the host crystal lattice structure, which are characteristic for different modes of location of the guest molecules. A new method is suggested for the analysis of the volume and shape of the empty space in clathrates. Experimental data are reported on the dependence of the a and c parameters of the unit cell of clathrate phases (with furan and dichloromethane as guest components) from the guest uptake. Consideration of these data permit us to construct a model of the changes of host–host interactions in the -[Ni(NCS)₂(4-methylpyridine)₄] clathrates with change of guest uptakes. Modeling of the process of diffusion of the guest molecule through the channel of the -[Ni(NCS)₂(4-methylpyridine)₄] clathrate allowed the nature of the rate-determining step of diffusion to be established. Part 1 of this series has been published as [3].     

A Diaminopillar[5]arene-Based Macrobicyclic Molecule: Synthesis,Characterization and A Lock–Key Story

A new macrobicyclic molecule ( BC-DAP5 ), consisting of a diaminopillar[5]arene cavity and a fused ring, was successfully constructed using a Grubbs metathesis reaction. Further studies indicated that BC-DAP5 possessed a unique molecular behavior, showing a response to acid/base stimuli. In BC-DAP5 , protons (acid) acted as a lock, locking the fused ring out of the cavity (pillar[5]arene), and a base served as the key, making the fused ring switch in or out freely. Reversible control of the molecular behavior was achieved simply by adding acid and base alternately.     

Synthesis of novel pillar-shaped cavitands “Pillar[5]arenes” and their application for supramolecular materials

In 2008, we reported a new class of macrocyclic hosts and named “Pillar[5]arenes”. They combine the advantages and aspects of traditional hosts and have a composition similar to those of typical calix[n]arenes. Pillar[5]arenes have repeating units connected by methylene bridges at the para-position, and thus they have a unique symmetrical pillar architecture differing from the basket-shaped structure of meta-bridged calix[n]arenes. Pillar[5]arenes show high functionality similar to cyclodextrins, and can capture electron accepting guest molecules within their cavity similarly to cucurbit[n]urils. In this review, the synthesis, structure, rotation, host–guest properties, planar chirality and functionality of pillar[5]arenes are discussed, along with pillar[5]arene-based supramolecular architectures and the challenges in synthesizing pillar[6]arenes.     

π-Extended Pyrrole-Fused Heteropine: Synthesis,Properties, and Application in Organic Field-Effect Transistors

Sulfur-embedded polycyclic aromatic compounds have been used as building blocks for numerous organic semiconductors over the past few decades. While the success is based on thiophene-containing compounds, aromatic compounds that contain thiepine, a sulfur-containing seven-membered-ring arene, has been less well investigated. Here we report the synthesis and properties of π-extended pyrrole-fused heteropine compounds such as thiepine and oxepine. A π-extended pyrrole-fused thiepine exhibited a “pitched π-stacking” structure in the crystal, and exhibited a high charge carrier mobility of up to 1.0 cm² V⁻¹ s⁻¹ in single-crystal field-effect transistors.     

Erratum to: “Asymmetric Calix[4]-thiacalix[4]arene Tubes: Synthesis and Ionophore Properties”

Russian Journal of Organic Chemistry -     

Synthesis of Electron-Deficient Corona[5]arenes and Their Selective Complexation with Dihydrogen Phosphate: Cooperative Effects of Anion–π Interactions

Reported here are the syntheses, conformational structures, electrochemical properties, and noncovalent anion binding of corona[5]arenes. A (3+2) fragment coupling reaction proceeded efficiently under mild reaction conditions to produce a number of novel heteroatom- and methylene-bridged corona[3]arene[2]tetrazine macrocycles. Selective oxidation of the sulfur atom between two phenylene rings afforded sulfoxide- and sulfone-linked corona[5]arenes in good yields. All corona[5]arenes synthesized adopted similar 1,2,4-alternate conformational structures, forming pentagonal cavities. The cavity sizes and the electronic properties such as redox potentials, were measured with CV and DPV, and were influenced by the different bridging units. As electron-deficient macrocycles, the acquired corona[3]arene[2]tetrazines served as highly selective hosts, forming complexes with the hydrogen-bonded dimer of dihydrogen phosphate through cooperative anion–π interactions.     

Synthesis of i-Corona[6]arenes for Selective Anion Binding: Interdependent and Synergistic Anion–π and Hydrogen-Bond Interactions

i-Corona[3]arene[3]tetrazines were synthesized from the nucleophilic aromatic substitution reaction of resorcinol and its derivatives with 3,6-dichlorotetrazine in a one-pot fashion under mild conditions. All of the resulting macrocycles adopted 1,3,5-alternate conformation irrespective of the nature of the substituents on both upper- and lower-rims. i-Corona[3]arene[3]tetrazine was found to self-regulate its macrocyclic conformation and cavity to recognize anions with binding constants spanning from 26 M⁻¹ to 2.2×10³ M⁻¹ depending on the structure of the anions. The selective binding resulted from a significant interdependent and synergistic effect between multiple tetrazine π/anion and C_aryl–H/anion hydrogen bond interactions. Taking advantage of synergistic effect revealed, a cyanobenzene-embedded i-corona[3]arene[3]tetrazine was designedly synthesized and highly selective and very strong affinity toward nitrate with a binding constant of 2.2×10⁵ M⁻¹ was achieved.     

1,4-Diphenyl-5H-[1,2,5]triazepino[5,4-a]benzimidazole—A New Heterocyclic System. Synthesis and Properties

Russian Journal of Organic Chemistry - The first representative of a new heterocyclic system, 1,4-diphenyl-5H-[1,2,5]triazepino[5,4-a]-benzimidazole, has been synthesized by condensation of ethyl...     

Polarographic Studies on Anion Coordination Chemistry. Host–Guest Interactions of Hexacyclen and Pentacyclen with Pyrophosphate, Selenite, Selenate, Molybdate and Tungstate Anions

The complexation of protonated hexacyclen and pentacyclen with pyrophosphate, selenite, selenate, molybdate and tungstate anions was studied by differential pulse polarography at 25 °C. The stoichiometry and stability of the resulting anion complexes were evaluated from the pH and concentration-dependence of the peak potentials, respectively. The results established 1 : 1 anion receptor complexation in all cases. In the case of all anions studied, hexacyclen was found to form more stable anion complexes than pentacyclen. The fact that the anion-receptor complexation depends on the structural features of both the anions and the macrocycles used is indicative of a steric controlled interaction.     

Triarylborane-Based Helical Donor–Acceptor Compounds: Synthesis,Photophysical, and Electronic Properties

The synthesis and characterization of 10-(dimesitylboryl)-N,N-di-p-tolylbenzo[c]phenanthren-4-amine (3-B(Mes)₂-[4]helix-9-N(p-Tol)₂ 1 ) and 13-(dimesitylboryl)-N,N-di-p-tolyldibenzo[c,g]phenanthren-8-amine (3-B(Mes)₂-[5]helix-12-N(p-Tol)₂ 2 ) are reported herein. Their electrochemical and photophysical properties have been studied experimentally and theoretically. The donor and acceptor-substituted helicene derivatives exhibit moderate fluorescence quantum yields in THF (Φ_f=0.48 and 0.61 for 1 and 2 , respectively), which are higher than unsubstituted ones (Φ_f=0.18 for [4]helicene; Φ_f<0.05 for [n]helicenes (n≥5)). In the solid state, the Φ_f values are higher (Φ_f=1.00 and 0.55 for 1 and 2 , respectively) than those in solution, most likely due to the restrictions of molecular motions. The S₁←S₀ transitions of 1 and 2 are predominately HOMO→LUMO transitions. Upon excitation with UV light, the interplanar angle between the two terminal aryl rings of the [5]helix core of 2 decreases (S₁ state compared with S₀ state), which is similar to placing a spring under an external force.     

[Fe2(μ-SC5H4N)2(NO)4] as a New Potential NO Donor: Synthesis,Structure, and Properties

A new potential donor of nitrogen monoxide, a binuclear iron sulfur nitroso complex, was prepared by exchange reaction of Na₂Fe₂(S₂O₃)₂(NO)₄ with pyridine-2-thiol in the presence of sodium thiosulfate at pH 12. The molecular and crystal structures of [Fe₂(-SC₅H₄N)₂(NO)₄] were studied by X-ray diffraction analysis. The type of iron coordination by pyridine-2-thiol in the presence of a coordinated NO molecule was determined. In vacuum, the structure of the complex is destroyed, which is accompanied by NO evolution, while exposure to UV radiation results in decomposition of the complex and in a release of N₂O.     

Host–Guest Chemistry in the Gas Phase: Complex Formation of Cucurbit[6]uril with Proton-bound Water Dimer

The hydration of cucurbit[6]uril (CB[6]) in the gas phase is investigated using electrospray ionization traveling wave ion mobility mass spectrometry (ESI-TWIM-MS). Highly abundant dihydrated and tetrahydrated species of diprotonated CB[6] are found in the ESI-TWIM-MS spectrum. The hydration patterns of the CB[6] ion and the dissociation patterns of the hydrated CB[6] ion indicate that two water molecules are bound to each other, forming a water dimer in the CB[6] complex. Ion mobility studies combined with the structures calculated by density functional theory suggest that the proton-bound water dimer is present as a Zundel-like structure in the CB[6] portal, forming a hydrogen bond network with carbonyl groups of the CB[6]. When a large guest molecule is bound to a CB[6] portal, water molecules cannot bind to the portal. In addition, the strong binding energy of the water dimer blocks the portal, hindering the insertion of the long alkyl chain of the guest molecule into the CB[6] cavity. With small alkali metal cations, such as Li⁺ and Na⁺, a single water molecule interacts with the CB[6] portal, forming hydrogen bonds with the carbonyl groups of CB[6]. A highly stable Zundel-like structure of the proton-bound water dimer or a metal-bound water molecule at the CB[6] portal is suggested as an initial hydration process for CB[6], which is only dissolved in aqueous solution with acid or alkali metal ions.

Synthesis and Properties of Biodegradable Copolymers of 9-Phenyl-2, 4, 8, 10-tetraoxaspiro-[5, 5]undcane-3-one and Ethylene Ethyl Phosphate

Novel biodegradable copolymer poly（CC-co-EEP） was synthesized by ring-opening copolymerization of cyclic carbonate 9-phenyl-2, 4, 8, 10-tetraoxaspiro-[5, 5]undcane-3-one （CC） and ethylene ethyl phosphate （EEP）. The obtained poly （CC-co-EEP）s were characterized by FTIR, ^1H NMR, ^13C NMR and gel permeation chromatography （GPC）. In vitro hydrolytic degradation of the copolymers were investigated in phosphate buffer solution （pH=7.4）. Hydrophilic phosphate units apparently improved the degradability of poly（carbonate-phosphate）.