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1.
Dr. Katharina Kaleta Frank Strehler Dr. Alexander Hildebrandt Dr. Torsten Beweries Dr. Perdita Arndt Dr. Tobias Rüffer Dr. Anke Spannenberg Prof. Dr. Heinrich Lang Prof. Dr. Uwe Rosenthal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(40):12672-12680
The reaction of different metallocene fragments [Cp2M] (Cp=η5‐cyclopentadienyl, M=Ti, Zr) with diferrocenylacetylene and 1,4‐diferrocenylbuta‐1,3‐diyne is described. The titanocene complexes form the highly strained three‐ and five‐membered ring systems [Cp2Ti(η2‐FcC2Fc)] ( 1 ) and [Cp2Ti(η4‐FcC4Fc)] ( 2 ) (Fc=[Fe(η5‐C5H4)(η5‐C5H5)]) by addition of the appropriate alkyne or diyne to Cp2Ti. Zirconocene precursors react with diferrocenyl‐ and ferrocenylphenylacetylene under C? C bond coupling to yield the metallacyclopentadienes [Cp2Zr(C4Fc4)] ( 3 ) and [Cp2Zr(C4Fc2Ph2)] ( 5 ), respectively. The exchange of the zirconocene unit in 3 by hydrogen atoms opens the route to the super‐crowded ferrocenyl‐substituted compound tetraferrocenylbutadiene ( 4 ). On the other hand, the reaction of 1,4‐diferrocenylbuta‐1,3‐diyne with zirconocene complexes afforded a cleavage of the central C? C bond, and thus, dinuclear [{Cp2Zr(μ‐η1:η2‐C?CFc)}2] ( 6 ) that consists of two zirconocene acetylide groups was formed. Most of the complexes were characterized by single‐crystal X‐ray crystallography, showing attractive multinuclear molecules. The redox properties of 3 , 5 , and 6 were studied by cyclic voltammetry. Upon oxidation to 3 n+, 5 n+, and 6 n+ (n=1–3), decomposition occured with in situ formation of new species. The follow‐up products from 3 and 5 possess two or four reversible redox events pointing to butadiene‐based molecules. However, the dinuclear complex 6 afforded ethynylferrocene under the measurement conditions. 相似文献
2.
Yuheng Yang Prof. Dr. Yongshu Xie Dr. Qiong Zhang Prof. Dr. Keitaro Nakatani Prof. Dr. He Tian Prof. Dr. Weihong Zhu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(37):11685-11694
Three photochromic compounds—2‐butyl‐5,6‐bis[5‐(4‐methoxyphenyl)‐2‐methylthiophen‐3‐yl]‐1 H‐benzo[de]isoquinoline‐1,3(2 H)‐dione (BTE‐NA), 4,5‐bis[5‐(4‐methoxyphenyl)‐2‐methylthiophen‐3‐yl]benzo[c][1,2,5]thiadiazole (BTA), and BTTA, which contain naphthalimide, benzothiadiazole, and benzobisthiadiazole as six‐membered ethene bridges with different aromaticities—were systematically studied in solution, sol–gel, and single‐crystal states. They exhibit typical photochromic performance with considerably high cyclization quantum yields. BTE‐NA, BTA, and BTTA form a typical donor–π–acceptor (D –π–A) system with significant intramolecular charge transfer (ICT) between HOMO and LUMO upon excitation, thus realizing the fluorescence modulation by both photochromism and solvatochromism. The three ethene bridges with different degrees of aromaticity can provide a systematic comparison of the thermal stability evolution for their corresponding closed forms (c‐BTE‐NA, c‐BTA, and c‐BTTA). c‐BTE‐NA shows first‐order decay in various solvents from cyclohexane to acetonitrile. c‐BTA only shows first‐order decay in polar solvents such as chloroform, whereas it is stable in nonpolar solvents like toluene. In contrast, the less aromatic property of BTTA gives rise to its unprecedented thermal stability in various solvents even at elevated temperatures in toluene (328 K). Moreover, the small energy barrier between the parallel and antiparallel conformers allows the full conversion from BTTA to c‐BTTA. In well‐ordered crystal states, all three compounds adopt a parallel conformation. Interestingly, BTTA forms a twin crystal of asymmetric nature with interactions between the electron‐rich oxygen atom of the methoxy group and the carbon atom of the electron‐deficient benzobisthiadiazole moiety. This work contributes to the understanding of aromaticity‐controlled thermal stability of photochromic systems based on a six‐membered ring as an ethene bridge, and a broadening of the novel building blocks for photochromic bisthienylethene systems. 相似文献
3.
Olexyj M. Huta Ihor O. Patsaj Antoni Konitz Joanna Meszko Jerzy Baejowski 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(5):o295-o297
The title compound, C15H11N2+·HN2O6?, crystallizes in the monoclinic space group C2/c with four molecules in the unit cell. The planar 9‐cyano‐10‐methylacridinium cations lie on crystallographic twofold axes and are arranged in layers, almost perpendicular to the ac plane, in such a way that neighbouring molecules are positioned in a `head‐to‐tail' manner. These cations and the hydrogen dinitrate anions are linked through C—H?O interactions involving four of the six O atoms of the anion and the H atoms attached to the C atoms of the acridine moiety in ring positions 2 and 4. The H atom of the hydrogen dinitrate anion appears to be located on the centre of inversion relating two of the four O atoms engaged in the above‐mentioned C—H?O interactions. In this way, columns of either anions or cations running along the c axis are held in place by the network of C—H?O interactions, forming a relatively compact crystal lattice. 相似文献
4.
Brian Frstrup Dan Peters Andrew D. Bond 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(8):o298-o301
The title compound, C15H16NS+·C2H3O2−, has been crystallized as both a pure enantiomer (1S,5R) and a racemate. The racemate crystallizes in the space group Cc, with molecules of opposite handedness related to each other by the action of the c‐glide. The enantiomer is essentially isostructural with the racemate, except that the glide symmetry is violated by interchange of CH and CH2 groups within the seven‐membered ring. The space‐group symmetry is reduced to P1 with two molecules in the asymmetric unit. The enantiomer structure shows disorder of the thiophene ring for one of the molecules in the asymmetric unit. The major component of the disorder has the thiophene ring in the same position as in the racemate, but generates a higher‐energy molecular conformation. The minor disorder component has different intermolecular interactions but retains a more stable molecular conformation. 相似文献
5.
Nikolaos C. Papandreou Stella Makedonopoulou Ekaterini A. Antoniadou‐Vyza Irene M. Mavridis Stavros J. Hamodrakas 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(12):o730-o732
The title salt, C18H22N5+·Cl?, is a member of a new series of lipophilic 4,6‐diamino spiro‐s‐triazines which are potent inhibitors of dihydrofolate reductase. The protonated triazine ring deviates from planarity, whereas the cyclohexane ring adopts a chair conformation. A rather unusual hydrogen‐bonding scheme exists in the crystal. There is a centrosymmetric arrangement involving two amino groups and two triazine ring N atoms, with graph‐set R(8) and an N?N distance of 3.098 (3) Å, flanked by two additional R(8) systems, involving two amino groups, a triazine ring N atom and a Cl? anion, with N?Cl distances in the range 3.179 (2)–3.278 (2) Å. Furthermore, the Cl? anion, the protonated triazine ring N atom and an amino group form a hydrogen‐bonding system with graph‐set R(6). 相似文献
6.
Steffen Styra Dr. Mohand Melaimi Dr. Curtis E. Moore Prof. Arnold. L. Rheingold Timo Augenstein Prof. Dr. Frank Breher Prof. Guy Bertrand 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(23):8441-8446
A stable cyclic (alkyl)(amino)carbene (CAAC) 1 inserts into the para‐CF bond of pentafluoropyridine, and after fluoride abstraction, the iminium‐pyridyl adduct [ 3 ]+ was isolated. A cyclic voltammetry study shows a reversible three‐state redox system involving [ 3 ]+, [ 3 ] ? , and [ 3 ] ? . The CAAC‐pyridyl radical [ 3 ] ? , obtained by reduction of [ 3 ]+ with magnesium, has been spectroscopically and crystallographically characterized. In contrast to the lack of π communication between the CAAC and the pyridine units in cation [ 3 ]+, the unpaired electron of [ 3 ] ? is delocalized over an extended π system involving both heterocycles. 相似文献
7.
Daniel Schmidt Bernhard Häupler Martin D. Hager Ulrich S. Schubert 《Journal of polymer science. Part A, Polymer chemistry》2016,54(13):1998-2003
Redox‐active anthraquinone based polymers are synthesized by the introduction of a polymerizable vinyl and ethynyl group, respectively, resulting in redox‐active monomers, which electrochemical behaviors are tailored by the modification of the keto groups to N‐cyanoimine moieties. These monomers can be polymerized by free radical polymerization and Rh‐catalyzed polymerization methods, respectively. The resulting polymers are obtained in molar masses (Mn) of 4,400 to 16,800 g mol?1 as well as high yields of up to 97%. The monomers and polymers are furthermore electrochemically characterized by cyclic voltammetry. The monomers exhibit two one‐electron redox reactions at about ?0.6 and ?1.0 V versus Fc+/Fc. The N‐cyanoimine units are, however, partially hydrolyzed during the polymerization step or during the electrochemical measurements and degenerate to carbonyl groups, resulting in a new reduction signal at ?1.26 V versus Fc+/Fc. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1998–2003 相似文献
8.
Redox‐Active Metal–Organic Frameworks: Highly Stable Charge‐Separated States through Strut/Guest‐to‐Strut Electron Transfer
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Nivedita Sikdar Dr. Kolleboyina Jayaramulu Dr. Venkayala Kiran Dr. K. Venkata Rao Prof. Srinivasan Sampath Prof. Subi J. George Prof. Tapas Kumar Maji 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(33):11701-11706
Molecular organization of donor and acceptor chromophores in self‐assembled materials is of paramount interest in the field of photovoltaics or mimicry of natural light‐harvesting systems. With this in mind, a redox‐active porous interpenetrated metal–organic framework (MOF), {[Cd(bpdc)(bpNDI)] ? 4.5 H2O ? DMF}n ( 1 ) has been constructed from a mixed chromophoric system. The μ‐oxo‐bridged secondary building unit, {Cd2(μ‐OCO)2}, guides the parallel alignment of bpNDI (N,N′‐di(4‐pyridyl)‐1,4,5,8‐naphthalenediimide) acceptor linkers, which are tethered with bpdc (bpdcH2=4,4′‐biphenyldicarboxylic acid) linkers of another entangled net in the framework, resulting in photochromic behaviour through inter‐net electron transfer. Encapsulation of electron‐donating aromatic molecules in the electron‐deficient channels of 1 leads to a perfect donor–acceptor co‐facial organization, resulting in long‐lived charge‐separated states of bpNDI. Furthermore, 1 and guest encapsulated species are characterised through electrochemical studies for understanding of their redox properties. 相似文献
9.
Dr. Satoshi Muratsugu Masa‐aki Kishida Dr. Ryota Sakamoto Prof. Dr. Hiroshi Nishihara 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(51):17314-17327
The photochemical properties and the mixed‐valence state of bis(ferrocenylethynyl)benzodimethyldihydropyrene ( 1 ) and other benzodimethyldihydropyrene (BzDHP) derivatives were investigated to understand the reversible photoswitching in the electronic communication of 1 . Absorption spectra of 1 were characterized by UV/Vis spectroscopy and calculated by using time‐dependent density functional theory (TD‐DFT), and the d orbitals of the ferrocene (Fc) moieties were shown to contribute to the occupied valence orbitals that were responsible for the photochromic behavior. 1 exhibited reversible photoisomerization in THF; however, photochromic behavior was not observed in dichloromethane. Analysis of redox potentials showed that the mixed‐valence state of 1 was more stable in dichloromethane than in THF. This is consistent with the observation that chemical oxidation led to an intervalence charge‐transfer (IVCT) band between the Fc moieties in the mixed‐valence state of 1 in dichloromethane, whereas such a band was not observed for one‐electron‐oxidized 1 in THF. Bis(pentamethylferrocenylethynyl)benzodimethyldihydropyrene ( 2 ) did not show photochromic behavior even in THF. The mixed‐valence state of 2 was much less stable than that of 1 in dichloromethane, and no obvious IVCT band was observed for one‐electron‐oxidized 2 in dichloromethane. The difference in the redox contribution of Fc and pentamethylferrocene (Me5Fc) to BzDHP played an important role for these redox and photochromic behaviors; this was supported by analysis of valence orbital energies from DFT calculations. Designing molecules that connect redox centers through the use of a photochromic linker with a redox potential close to that of the redox centers could constitute a useful approach for the production of photochromic redox‐active metal complexes with strong electronic communication. 相似文献
10.
Wafaa S. Hamama Hamada G. El‐Gohary Mamdouh Soliman Hanfi H. Zoorob 《Journal of heterocyclic chemistry》2012,49(3):543-554
This research work describes the synthesis and biological properties of some novel isolated or fused heterocyclic ring systems with pyrazole, for example; enaminones containing pyrazolone ring photochromic functional unit, 4‐[(4‐chlorophenylamino)methylene]‐3‐methyl‐1‐phenyl‐1H‐pyrazol‐5(4H)‐one (3) and some analogous derivatives 4, 9, and 10, also as pyrazolo[3,4‐b]pyridine, pyrazolo[3,4‐b]quinoline, pyrazolo[3′,4′:4,5]thieno[2,3‐c]pyrazoline and pyrazolo[3,4‐c]pyrazole were synthesized and characterized. Newly synthesized compounds were characterized by IR, 1H NMR, 13C NMR, mass spectral data and quantum mechanical calculations. Selected products were tested for their antibacterial and antitumor agents. 相似文献
11.
Rolf Huisgen Grzegorz Mlostoń Peter Pöchlauer Lubor Fišera Henry Giera 《Helvetica chimica acta》2007,90(1):1-18
The cycloadditions of methyl diazoacetate to 2,3‐bis(trifluoromethyl)fumaronitrile ((E)‐ BTE ) and 2,3‐bis(trifluoromethyl)maleonitrile ((Z)‐ BTE ) furnish the 4,5‐dihydro‐1H‐pyrazoles 13 . The retention of dipolarophile configuration proceeds for (E)‐ BTE with > 99.93% and for (Z)‐ BTE with > 99.8% (CDCl3, 25°), suggesting concertedness. Base catalysis (1,4‐diazabicyclo[2.2.2]octane (DABCO), proton sponge) converts the cycloadducts, trans‐ 13 and cis‐ 13 , to a 94 : 6 equilibrium mixture (CDCl3, r.t.); the first step is N‐deprotonation, since reaction with methyl fluorosulfonate affords the 4,5‐dihydro‐1‐methyl‐1H‐pyrazoles. Competing with the cis/trans isomerization of 13 is the formation of a bis(dehydrofluoro) dimer (two diastereoisomers), the structure of which was elucidated by IR, 19F‐NMR, and 13C‐NMR spectroscopy. The reaction slows when DABCO is bound by HF, but F? as base keeps the conversion to 22 going and binds HF. The diazo group in 22 suggests a common intermediate for cis/trans isomerization of 13 and conversion to 22 : reversible ring opening of N‐deprotonated 13 provides 18 , a derivative of methyl diazoacetate with a carbanionic substituent. Mechanistic comparison with the reaction of diazomethane and dimethyl 2,3‐dicyanofumarate, a related tetra‐acceptor‐ethylene, brings to light unanticipated divergencies. 相似文献
12.
Dr. Dipanwita Das Hemlata Agarwala Dr. Abhishek Dutta Chowdhury Tuhin Patra Dr. Shaikh M. Mobin Prof. Dr. Biprajit Sarkar Prof. Dr. Wolfgang Kaim Prof. Dr. Goutam Kumar Lahiri 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(23):7384-7394
The complex series [Ru(pap)(Q)2]n ([ 1 ]n–[ 4 ]n; n=+2, +1, 0, ?1, ?2) contains four redox non‐innocent entities: one ruthenium ion, 2‐phenylazopyridine (pap), and two o‐iminoquinone moieties, Q=3,5‐di‐tert‐butyl‐N‐aryl‐1,2‐benzoquinonemonoimine (aryl=C6H5 ( 1+ ); m‐(Cl)2C6H3 ( 2+ ); m‐(OCH3)2C6H3 ( 3+ ); m‐(tBu)2C6H3 ( 4 +)). A crystal structure determination of the representative compound, [ 1 ]ClO4, established the crystallization of the ctt‐isomeric form, that is, cis and trans with respect to the mutual orientations of O and N donors of two Q ligands, and the coordinating azo N atom trans to the O donor of Q. The sensitive C? O (average: 1.299(3) Å), C? N (average: 1.346(4) Å) and intra‐ring C? C (meta; average: 1.373(4) Å) bond lengths of the coordinated iminoquinone moieties in corroboration with the N?N length (1.292(3) Å) of pap in 1 + establish [RuIII(pap0)(Q.?)2]+ as the most appropriate electronic structural form. The coupling of three spins from one low‐spin ruthenium(III) (t2g5) and two Q.? radicals in 1 +– 4 + gives a ground state with one unpaired electron on Q.?, as evident from g=1.995 radical‐type EPR signals for 1 +– 4 +. Accordingly, the DFT‐calculated Mulliken spin densities of 1 + (1.152 for two Q, Ru: ?0.179, pap: 0.031) confirm Q‐based spin. Complex ions 1 +– 4 + exhibit two near‐IR absorption bands at about λ=2000 and 920 nm in addition to intense multiple transitions covering the visible to UV regions; compounds [ 1 ]ClO4–[ 4 ]ClO4 undergo one oxidation and three separate reduction processes within ±2.0 V versus SCE. The crystal structure of the neutral (one‐electron reduced) state ( 2 ) was determined to show metal‐based reduction and an EPR signal at g=1.996. The electronic transitions of the complexes 1 n– 4 n (n=+2, +1, 0, ?1, ?2) in the UV, visible, and NIR regions, as determined by using spectroelectrochemistry, have been analyzed by TD‐DFT calculations and reveal significant low‐energy absorbance (λmax>1000 nm) for cations, anions, and neutral forms. The experimental studies in combination with DFT calculations suggest the dominant valence configurations of 1 n– 4 n in the accessible redox states to be [RuIII(pap0)(Q.?)(Q0)]2+ ( 1 2+– 4 2+)→[RuIII(pap0)(Q.?)2]+ ( 1 +– 4 +)→[RuII(pap0)(Q.?)2] ( 1 – 4 )→[RuII(pap.?)(Q.?)2]? ( 1 ?– 4 ?)→[RuIII(pap.?)(Q2?)2]2? ( 1 2?– 4 2?). 相似文献
13.
n‐Dopants Based on Dimers of Benzimidazoline Radicals: Structures and Mechanism of Redox Reactions
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Evgheni V. Jucov Prof. Sean Parkin Eric G. B. Evans Glenn L. Millhauser Tatiana V. Timofeeva Dr. Chad Risko Prof. Jean‐Luc Brédas Prof. Zhenan Bao Dr. Stephen Barlow Prof. Seth R. Marder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(30):10878-10885
Dimers of 2‐substituted N,N′‐dimethylbenzimidazoline radicals, (2‐Y‐DMBI)2 (Y=cyclohexyl (Cyc), ferrocenyl (Fc), ruthenocenyl (Rc)), have recently been reported as n‐dopants for organic semiconductors. Here their structural and energetic characteristics are reported, along with the mechanisms by which they react with acceptors, A (PCBM, TIPS‐pentacene), in solution. X‐ray data and DFT calculations both indicate a longer C?C bond for (2‐Cyc‐DMBI)2 than (2‐Fc‐DMBI)2, yet DFT and ESR data show that the latter dissociates more readily due to stabilization of the radical by Fc. Depending on the energetics of dimer (D2) dissociation and of D2‐to‐A electron transfer, D2 reacts with A to form D+ and A? by either of two mechanisms, differing in whether the first step is endergonic dissociation or endergonic electron transfer. However, the D+/0.5 D2 redox potentials—the effective reducing strengths of the dimers—vary little within the series (ca. ?1.9 V vs. FeCp2+/0) (Cp=cyclopentadienyl) due to cancelation of trends in the D+/0 potential and D2 dissociation energy. The implications of these findings for use of these dimers as n‐dopants, and for future dopant design, are discussed. 相似文献
14.
Dr. Elizabeth Castillo‐Martínez Dr. Javier Carretero‐González Prof. Michel Armand 《Angewandte Chemie (International ed. in English)》2014,53(21):5341-5345
The redox entity comprising two Schiff base groups attached to a phenyl ring (? N?CH? Ar? HC?N? ) is reported to be active for sodium‐ion storage (Ar=aromatic group). Electroactive polymeric Schiff bases were produced by reaction between non‐conjugated aliphatic or conjugated aromatic diamine block with terephthalaldehyde unit. Crystalline polymeric Schiff bases are able to electrochemically store more than one sodium atom per azomethine group at potentials between 0 and 1.5 V versus Na+/Na. The redox potential can be tuned through conjugation of the polymeric chain and by electron injection from donor substituents in the aromatic rings. Reversible capacities of up to 350 mA h g?1 are achieved when the carbon mixture is optimized with Ketjen Black. Interestingly, the “reverse” configuration (? CH?N? Ar? N?HC? ) is not electrochemically active, though isoelectronic. 相似文献
15.
Spectroscopic Capture and Reactivity of a Low‐Spin Cobalt(IV)‐Oxo Complex Stabilized by Binding Redox‐Inactive Metal Ions
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Seungwoo Hong Florian F. Pfaff Eunji Kwon Yong Wang Mi‐Sook Seo Eckhard Bill Dr. Kallol Ray Prof. Dr. Wonwoo Nam 《Angewandte Chemie (International ed. in English)》2014,53(39):10403-10407
High‐valent cobalt‐oxo intermediates are proposed as reactive intermediates in a number of cobalt‐complex‐mediated oxidation reactions. Herein we report the spectroscopic capture of low‐spin (S=1/2) CoIV‐oxo species in the presence of redox‐inactive metal ions, such as Sc3+, Ce3+, Y3+, and Zn2+, and the investigation of their reactivity in C? H bond activation and sulfoxidation reactions. Theoretical calculations predict that the binding of Lewis acidic metal ions to the cobalt‐oxo core increases the electrophilicity of the oxygen atom, resulting in the redox tautomerism of a highly unstable [(TAML)CoIII(O.)]2? species to a more stable [(TAML)CoIV(O)(Mn+)] core. The present report supports the proposed role of the redox‐inactive metal ions in facilitating the formation of high‐valent metal–oxo cores as a necessary step for oxygen evolution in chemistry and biology. 相似文献
16.
本文合成了一种新型配位聚合物[Cu(pa)(vim)2]n(pa为邻苯二甲酸阴离子,vim为1-乙烯基-1H-咪唑),并用x射线单晶衍射仪和元素分析表征了其单晶结构。晶体属单斜晶系,C2/c空间群,晶胞参数分别为:a=1.6527(3) nm, b=0.81800(16) nm, c=1.4463(3) nm, β=113.19(3)°, V=1.7973(7) nm3, Z=4, Dc=1.537 g?cm-3。 [I>2σ(I)]时:R1=0.0476, wR2=0.1235,对所有数据:R1=0.0693, wR2=0.1355。配合物的结构中存在沿着c轴的zigzag聚合链。每个铜原子位于晶体中心,与两个N原子和两个O原子进行配位,形成了扭曲的平面结构。电化学研究表明在配合物中Cu2+/Cu+的氧化还原是一个单电子的准可逆过程。 相似文献
17.
Matthias Prall Alexander Wittkopp Andrey A. Fokin Peter R. Schreiner 《Journal of computational chemistry》2001,22(13):1605-1614
The effects of several substituents (? BH2, ? BF2, ? AlH2, ? CH3, ? C6H5, ? CN, ? COCH3, ? CF3, ? SiH3, ? NH2, ? NH3+, ? NO2, ? PH2, ? OH, ? OH2+, ? SH, ? F, ? Cl, ? Br) on the Bergman cyclization of (Z)‐1,5‐hexadiyne‐3‐ene (enediyne, 3 ) were investigated at the Becke–Lee–Yang–Parr (BLYP) density functional (DFT) level employing a 6‐31G* basis set. Some of the substituents (? NH3+, ? NO2, ? OH, ? OH2+, ? F, ? Cl, ? Br) are able to lower the barrier (up to a minimum of 16.9 kcal mol?1 for difluoro‐enediyne 7rr ) and the reaction enthalpy (the cyclization is predicted to be exergonic for ? OH2+ and ? F) compared to the parent system giving rise to substituted 1,4‐dehydrobenzenes at physiological temperatures. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1605–1614, 2001 相似文献
18.
Juna Bae Jung Cho Jeong Hwan Lee Sung Man Seo Suk Bong Hong 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(26):7495-7499
Zeolite EU‐12, the framework structure of which has remained unsolved during the past 30 years, is synthesized at a specific SiO2/Al2O3 ratio using choline as an organic structure‐directing agent, with both Na+ and Rb+ ions present. Synchrotron powder X‐ray diffraction and Rietveld analyses reveal that the EU‐12 structure has a two‐dimensional 8‐ring channel system. Among the two distinct 8‐ring (4.6×2.8 and 5.0×2.7 Å) channels along c axis, the smaller one interconnects with the sinusoidal 8‐ring (4.8×3.3 Å) channel along a axis. The other large one is simply linked up with the sinusoidal channel by sharing 8‐rings (4.8×2.6 Å) in the ac plane. The proton form of EU‐12 was found to show a considerably higher ethene selectivity in the low‐temperature dehydration of ethanol than H‐mordenite, the best catalyst for this reaction. 相似文献
19.
20.
Juna Bae Jung Cho Jeong Hwan Lee Dr. Sung Man Seo Prof. Suk Bong Hong 《Angewandte Chemie (International ed. in English)》2016,55(26):7369-7373
Zeolite EU‐12, the framework structure of which has remained unsolved during the past 30 years, is synthesized at a specific SiO2/Al2O3 ratio using choline as an organic structure‐directing agent, with both Na+ and Rb+ ions present. Synchrotron powder X‐ray diffraction and Rietveld analyses reveal that the EU‐12 structure has a two‐dimensional 8‐ring channel system. Among the two distinct 8‐ring (4.6×2.8 and 5.0×2.7 Å) channels along c axis, the smaller one interconnects with the sinusoidal 8‐ring (4.8×3.3 Å) channel along a axis. The other large one is simply linked up with the sinusoidal channel by sharing 8‐rings (4.8×2.6 Å) in the ac plane. The proton form of EU‐12 was found to show a considerably higher ethene selectivity in the low‐temperature dehydration of ethanol than H‐mordenite, the best catalyst for this reaction. 相似文献