Catalytic Vapor Phase Pyridine Synthesis: A Process Review

The present work is an attempt to compile and analyze the literature pertaining to catalytic vapor phase pyridine synthesis. In the beginning pyridine deriving from coal tar and subsequent years it was developed as catalytic vapor phase synthesis using acetaldehyde, formaldehyde and ammonia provides best prospect for the growing demand. HZSM-5 is the best catalyst present in market to for catalytic pyridine bases; it has unique structural and acidity properties over other catalysts. It is probable that the reactants are adsorbed at catalytic sites, formation of imines precedes cyclisation and desorption from catalytic pores. In this review detail summary of the inventions in chronological order and with their postulates is narrated.     

Syntheses of shuttlecock- and bowl-equipped phenylazopyridines and photomodulation of their coordination ability to Zn-porphyrin

Shuttlecock- and bowl-equipped 4-(phenylazo)pyridine derivatives, which bear substituents that allow the pyridine moiety to protrude in the trans form but hinder it in the cis form, have been designed and synthesized. These molecules show cis/trans photoisomerization despite the presence of bulky substituents. ¹H NMR titration with Zn-porphyrin showed that the trans isomers coordinate to Zn-porphyrin much stronger than the cis isomers.     

Synthesis,some properties,and crystalline modifications of <Emphasis Type="Italic">fac</Emphasis>-[Ru(NO)(Py)<Subscript>2</Subscript>Cl<Subscript>3</Subscript>]

According to the data of ¹H NMR spectroscopy, trans-hydroxochloro complexes containing from two to four pyridine molecules in the internal sphere are formed on the heating of a dilute aqueous solution of K₂[Ru(NO)Cl₅] with pyridine. The evaporation of the reaction solution with concentrated hydrochloric acid gives fac-[Ru(NO)(Py)₂Cl₃] (I) in a yield of ~90%. The structures of two crystalline modifications of this complex are determined by X-ray diffraction analysis (CIF files ССDС nos. 1452208 (Ia) and 1452207 (Ib)). IR spectroscopy shows that the irradiation of complex I (λ ~ 450 nm, T = 80 K) results in photoisomerization with the formation of the metastable state MS1 in which the nitroso group is coordinated by the oxygen atom. The activation parameters of the photoisomerization are determined from the data of differential scanning calorimetry (DSC). Compound trans-[Ru(NO)Py₄(OH)]Cl₂ ? H₂O is isolated in a yield of ~70% on reflux of complex I with a pyridine excess in an aqueous solution, and the presence of molecules of water of crystallization in this compound is confirmed by thermal gravimetry (TG) and IR spectroscopy.     

Photo-induced structural changes of azobenzene Langmuir-Blodgett films

Structural changes of the Langmuir-Blodgett (LB) films of azobenzene accompanied by photoisomerization are described. First, photoisomerization is explained in terms of 'free volume'. In the polyion complex monolayers of amphiphiles having two azobenzene units at the air-water interface, the area per molecule depends on the polycation species. The fraction of cis-azobenzene in the LB films at the photostationary state under the illumination with UV light increased with increasing area per molecule, which is consistent with the concept of free volume. Second, a counter example of the concept of free volume is presented. Three-dimensional cone-shaped structures developed with trans-to-cis photoisomerization in the polyion complex LB film of a water-soluble amphiphilic azobenzene. These structures appeared and disappeared reversibly by alternate illumination with UV and visible light. The results indicate that the two-dimensional LB film structure exerts significant modification by photoisomerization. This is against the concept of free volume because this concept does not consider the possibility that the two-dimensional LB film structures may change into three-dimensional ones. Finally, photo-induced J-aggregate formation of non-photochromic and photochromic dyes is described. Two cyanine dyes were each mixed with an amphiphilic azobenzene in the LB films. These cyanine dyes are known to form J-aggregates in single-component LB films. In the mixed LB films, the J-aggregate formation was suppressed to some extent. The alternate illumination of the films with UV and visible light caused the photoisomerization of azobenzene in the mixed LB films, which triggered the J-aggregate formation of the cyanine dyes. The J-aggregate formation was accompanied by the development of three-dimensional cone-shaped structures from the film surface. When an amphiphilic merocyanine was mixed with the azobenzene in the LB films, J-aggregate formation was also induced by the alternate illumination with UV and visible light. This J-aggregate formation was also accompanied by a large morphological change: circular domains changed into fractal-like ones. The J-aggregate formation of the dyes and the concomitant morphological change were irreversible. In these cases, the photoisomerization of azobenzene served as a trigger to induce self-organization of the dye molecules.     

Selective Metal‐vapor Deposition on Organic Surfaces

Selective metal‐vapor deposition signifies that metal‐vapor atoms are deposited on a hard organic surface, but not on a soft (low glass transition temperature, low T_g) surface. In this paper, we introduce the origin, extension, and applications of selective metal‐vapor deposition. An amorphous photochromic diarylethene film shows light‐controlled selective metal‐vapor deposition, which is caused by a large T_g change based on photoisomerization, but various organic surfaces, including organic crystal and polymers, can be utilized for achieving selective metal‐vapor deposition. Various applications of selective metal‐vapor deposition, including cathode patterning of organic light‐emitting devices, micro‐thin‐film fuses, multifunctional diffraction gratings, in‐plane electrical bistability for memory devices, and metal‐vapor integration, have been demonstrated.     

Photodegradation of Hydrophobic Pyridineketoximes in Toluene and Heptane

The goal of the research was to study the reactivity of the hydrophobic 2‐ and 3‐pyridineketoximes under exposure to UV‐VIS light. The photodegradation was conducted in both toluene and heptane for 10 h under atmosphere of argon. Ten‐hour irradiation experiments demonstrated that the pyridineketoximes underwent the facile E‐Z photoisomerization, photo‐Beckmann rearrangement, and to a lesser extent, the photosubstitution to the pyridine ring. From LC‐MS and NMR analysis of the irradiated solutions, it was found that the photosubstitution proceeded to give the corresponding 6‐substituted 2‐ or 3‐pyridylketoxime via the replacement of the ring hydrogen by the benzyl or heptyl group. The photo‐Beckmann rearrangement led to the formation of the corresponding amides, but also other products formed in the photo‐decomposition reaction.     

Model study on the pyridine-Dewar pyridine and some related photoisomerization reactions

The potential energy surfaces corresponding to the photochemical reactions of pyridine, phosphinine, and arsabenzene have been investigated by employing the CAS(6,6)/6-311G(d,p) and MP2-CAS-(6,6)/6-311++G(3df,3pd)//CAS(6,6)/6-311G(d,p) methods. The thermal (or dark) reactions of these reactant species have also been examined using the same level of theory. The mechanisms of drastic structural change in the excited- and ground-state reactions of pyridine, phosphinine, and arsabenzene and the differences between them are elucidated. The theoretical investigations suggest that conical intersections play a crucial role in their photoisomerization reactions. The results obtained allow a number of predictions to be made.     

Reversible Photoisomerization from Borepin to Boratanorcaradiene and Double Aryl Migration from Boron to Carbon

B(npy)Ar₂ (npy=2‐(naphthalen‐1‐yl)pyridine) compounds bearing various nonbulky aryl groups undergo a clean and sequential two‐step photoisomerization in which two aryl substituents on boron migrate to a carbon atom of the naphthyl moiety. The second isomerization step is the first example of a reversible photoisoermization between a borepin and a borirane. Both steric and electronic factors have been found to have a great impact on this photoreactivity. Furthermore, the borirane isomer reacts with oxygen, forming a rare oxaborepin dimer.     

Supramolecular hydrogen-bonded liquid–crystalline polymer complexes. Design of side-chain polymers and a host–guest system by noncovalent interaction

Supramolecular liquid–crystalline polymeric complexes based on a backbone that contains vinyl pyridine units and azobenzene or biphenyl derivatives that posses alkyl chains terminated by carboxylic acid have been obtained by the formation of intermolecular hydrogen bonds between the carboxylic acid and the pyridyl moieties. The polymeric complexes behave as side-chain liquid–crystalline polymers and exhibit smectic phases. A new type of H-bonded host-guest liquid–crystalline system is also reported. The liquid–crystalline host copolymers contain both mesogenic acrylate and 4-vinylpyridine units. The guest molecule is an azobenzene that has a carboxylic acid moiety at one of its extremities. The H-bonded polymeric host–guest complexes exhibit nematic phases. Sequential UV and visible light irradiation of the polymeric complex causes reversible photochemically induced phase transitions. The isothermal nematic–isotropic and isotropic–nematic transitions result from the trans-cis and cis-trans photoisomerization of the guest azobenzene in the host–guest system. © 1996 John Wiley & Sons, Inc.     

Photodegradation of pyridylketoximes in methanolic solutions under UV–Vis radiation

Photodegradation of the oximes of alkyl-2-, -3-, and -4-pyridylketones and identification of possible degradation products using LC–MS/MS and GC–MS techniques were performed. The influence of copper(II) and iron(III) ions on the stability of the oxime under UV–Vis radiation exposure were also studied. It was found that the photodegradation of the pyridylketoximes resulted in the photoisomerization, photofragmentation and photosubstitution to a pyridine ring. Based on these results, a hypothetical mechanism of photodegradation of pyridylketoximes was proposed.     

Photochromism of new unsymmetrical isomeric diarylethenes bearing a pyridine group

A new class of unsymmetrical isomeric diarylethenes bearing a terminal pyridine group was synthesized and their structures were determined by single-crystal X-ray diffraction analysis. The effects of the nitrogen atom position in the pyridine group on their properties including photochromism, acidchromism, and fluorescence were investigated systematically. Among the three isomeric derivatives, the cyclization quantum yield and the absorption maxima of the ortho-substituted diarylethene were the biggest, while the fluorescence quantum yield of the para-substituted diarylethene was the biggest. Furthermore, the three isomeric diarylethenes exhibited multi-addressable switching behaviors by the stimulation of acid/base and light. Addition of trifluoroacetic acid to solutions of these diarylethenes produced the protonated derivatives, which also showed excellent photochromic behaviors, but only the para-substituted diarylethene exhibited a notable color change of solution from crimson to violet. The results revealed that the effects of the nitrogen atom position in the terminal pyridine group played a very important role during the process of photoisomerization for these isomeric diarylethene derivatives.     

Halogen Bonding Adsorbent Pyridine N-oxides for Iodine Capture in Water

Rapid capture of ¹²⁹I with high volatility and toxicity in the environment has attracted much attention. Herein we reported a firstly synthesized nonporous material: pyridine N-oxides (NTPO and ATPO) as iodine adsorbent. Both of NTPO and ATPO exhibit remarkable performance on the adsorption of iodine in aqueous solution, vapor state and organic solvents. Upon the capture of iodine, pyridine N-oxides were transformed to binary cocrystals combined with the pyridine N-oxides and iodine which is driven by halogen bond between iodine and oxygen atoms. Moreover, pyridine N-oxides shows high chemical, thermal and moisture stability.     

Regioselective E(trans)-Z(cis) photoisomerization in naphthyldiene derivatives

Naphthyldiene derivatives,1-4, carrying electron-donating groups at one end and electron-withdrawing groups at the other, were synthesized to study the photoisomerization process. All the compounds showed efficient photoisomerization upon direct excitation leading to the formation of 4-Z isomer with high selectivity. Triplet sensitization studies indicated inefficientE-Z isomerization process. Room temperature fluorescence of1 and2 displayed fine structure in hexane solvent and the same was replaced by broad or structureless fluorescence in acetonitrile and methanol solvents. A mechanism involving a polarized or charge transfer singlet excited state is proposed for the observed photoisomerization in these naphthyldiene derivatives.     

A Multi‐Addressable Switch Based on the Dimethyldihydropyrene Photochrome with Remarkable Proton‐Triggered Photo‐opening Efficiency

A series of photochromic derivatives based on the trans‐10b,10c‐dimethyl‐10b,10c‐dihydropyrene (DHP, “closed form”) skeleton has been synthesized and their photoisomerization leading to the corresponding cyclophanediene (CPD, “open form”) isomers has been investigated by UV/Vis and ¹H NMR spectroscopies. Substitution of the DHP core with electron‐withdrawing pyridinium groups was found to have major effects on the photoisomerization efficiency, the most remarkable examples being to enhance the quantum yield of the opening reaction and to allow fast and quantitative conversions at much lower radiant energies. This effect was rationalized by theoretical calculations. We also show that the reverse reaction, that is, going from the open form to the closed form, can be electrochemically triggered by oxidation of the CPD unit and that the photo‐opening properties of pyridine‐substituted DHPs can be efficiently tuned by protonation, the system behaving as a multi‐addressable molecular switch. These multi‐addressable photochromes show promise for the development of responsive materials.     

吡啶预处理抑制煤热解过程中交联反应的研究

采用吡啶蒸气、吡啶溶液两种溶胀方式对伊泰褐煤进行了预处理,用热重结合在线质谱仪考察了两种处理方式对煤热解过程中交联反应的抑制效果。结果表明,两种预处理方法对煤热解过程的交联反应都有不同程度的抑制,但其作用温度和机理不同。吡啶蒸气预处理可能通过与煤形成N—OH氢键、断开煤本身含氧官能团之间的氢键,从而在400℃以前抑制煤本身含氧官能团之间的氢键交联反应;吡啶溶液预处理主要是通过改变煤的结构,减少煤小分子同大分子网络结构之间缔合,提高氢的传递效率等因素来抑制小分子同煤大分子网络结构及其热解过程中间碎片之间的交联反应。     

The exciplexes of thioindigo with durene and hexamethylbenzene and their influence on photoisomerization

The quenching of thioindigo flourescence by hexamethylbenzene and durene in solvents of low polarity is accompanied by exciplex emission. The exciplex formation and dissociation rate constants and its photophysical properties are determined. Thiondigo photoisomerization can proceed via exciplex formation.     

双(苯并噁唑)芪的光物理行为及其异构化反应的研究

研究了双(苯并噁唑)芪的光物理行为和光顺反异构化反应,对这类化合物的发光光谱不依赖于溶剂极性的原因进行了初步讨论。异构化反应中,发现乙二醇引入时会加速该化合物反-顺异构化和抑制顺-反过程的回复,其原因可能是与生成了顺式异构体两个苯基苯并噁唑间的氢键有关。     

Theoretical investigation of formation mechanism of bipyridyl molecule on Ni(111) surface: implication for synthesis of N-doped graphene from pyridine

The formation mechanism of bipyridyl molecule catalyzed by nickel catalyst with pyridine precursor has been studied using density functional theory calculations. The formation of bipyridyl on Ni(111) surface from two pyridine molecules is considered as the initial process of N-doped graphene growth, and the minimum energy pathway for the formation has been investigated in detail. The whole formation processes mainly includes three steps, i.e., the dehydrogenation of the first pyridine, adsorption and dehydrogenation of the second pyridine, and formation of the bipyridyl molecule. It is found that the C-H bond of pyridine could be selectively dissociated while the C-C and C-N bond connections are retained during the catalytic processes. The N-doped graphene formed by pyridine only contains pyridine-like nitrogen atoms, suggesting a possible way to produce N-doped graphene with pure pyridine-like nitrogen atoms. The comparison of formation mechanisms between bipyridyl and biphenyl molecules was carried out, and the results imply a lower temperature process for synthesis of N-doped graphene from pyridine than that for graphene from benzene.     

The energies of dissociation of the N—O bonds in pyridine 1-oxide derivatives

The enthalpies of combustion of some pyridine derivatives in the solid state have been measured by precision bomb calorimetry, and their enthalpies of formation have been calculated. The enthalpies of sublimation of these compounds have been determined from the experimental temperature dependences of saturated vapor pressure using the Clausius-Clapeyron equation. The enthalpies of combustion, formation, and sublimation are the following (kJ mol^–1): -3360.9±2.1, -0.5±2.1, and 79.1±1.3, respectively, for 4-methylpyridine 1-oxide; -2551.0±1.7, 11.7±1.7, and 89.1±2.5, respectively, for 4-nitropyridine 1-oxide;-2355.6±1.3, 102.1±1.3, and 106.3±2.9 for 2,4,6-trinitropyridine 1-oxide; and -2287.6±1.3, 34.3±1.3, and 101.7±2.9 for 2,4,6-trinitropyridine. The enthalpies of formation in the solid state and the enthalpies of sublimation of pyridine derivatives obtained together with the literature data allowed the energies of dissociation of the donor-acceptor N—O bonds in pyridine 1-oxides to be calculated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 660–662, April, 1995.     

The photochemistry of a bis-crown ether based on benzobis(thiazole) and its alkaline earth metal cation complexes

Irradiation of acetonitrile solutions of the bis-crown ether E,E-2,7-bis[2-(6,7,9,10,12,13,15,16-octahydro-5,8,11,14,17-pentaoxabenzocyclopentadecen-2-yl)vinyl]-benzo[1,2-d;3,4-d']bisthiazole (hereafter, 1) gives efficient E --> Z photoisomerization (initial phi(trans --> cis) = 0.48), leading to lambda(exc)-dependent quasi-photostationary states composed primarily of E,Z and E,E isomer mixtures. Further irradiation gives [2 + 2]-cycloadducts of 1. In the presence of Ba2+ ions, essentially quantitative formation of 2:2 complexes, 1(2) x (Ba2+)2 controls the photochemical outcome. E --> Z photoisomerization of the ligand is entirely suppressed and efficient intramolecular [2 + 2]-photocycloaddition in the complexes leads to cyclobutane dimers of 1 (phiCB = 0.26). The reactivity of 1 in the presence of Mg2+ ions for which 1:2 complex formation dominates gives both cis-trans photoisomerization and enhanced photocycloaddition.