Complexes of acridine and 9-chloroacridine with I2: formation of unusual I6 chains through charge-transfer interactions involving amphoteric I2

Acridine and 9-chloroacridine form charge-transfer complexes with iodine in which the nitrogen-bound I2 molecule is amphoteric; one end serves as a Lewis acid to the heterocyclic donor, while the other end acts as a Lewis base to a second I2 molecule that bridges two acridine.I2 units. In the acridine derivative [(acridine.I2)2.I2, 1], the dimer has a "zigzag" conformation, while in the 9-chloroacridine derivative [(9-Cl-acridine.I2)2.I2, 2], the dimer is "C-shaped". The thermal decomposition of the two complexes is very different. Compound 1 loses one molecule of I2 to form an acridine.I2 intermediate, which has not been isolated. Further decomposition gives acridine as the form II polymorph, exclusively. Decomposition of 2 involves the loss of two molecules of I2 to form a relatively stable intermediate [(9-Cl-acridine)2.I2, 3]. Compound 3 consists of two 9-Cl-acridine molecules bridged through N...I charge-transfer interactions by a single I2 molecule. This compound represents the first known example, in which both ends of an I2 molecule form interactions in a complex that is not stabilized by the extended interactions of an infinite chain structure. The ability of the terminal iodine of an N-bound I2 to act either as an electron donor (complexes 1 and 2) or as an electron acceptor (complex 3) can be understood through a quantum mechanical analysis of the systems. Both electrostatic interactions and the overlap of frontier molecular orbitals contribute to the observed behavior.     

过渡金属原子对掺杂g-CN单层作为高效氮电催化剂性能

由于氨是药物、肥料和树脂等领域的基础,氨合成一直广受关注.工业中主要通过Haber-Bosch反应制备氨,反应需要在高温高压下进行.因此,探索其它氨合成技术对减轻能源消耗和缓解温室效应具有重大意义.在溶液条件下,采用水作为氢质子源,电化学还原氮合成氨方法受到了极大关注.然而,大多数电催化剂难以活化氮气分子且电催化氮气还...     

Theoretical study on molecular property of protactinium(V) and uranium(VI) oxocations: why does protactinium(V) form monooxo cations in aqueous solution?

The stability of Pa(V) and U(VI) oxocations in aqueous solution were theoretically investigated by means of density functional theory calculations. As a result, the present calculations clearly supported an experimental result from an energetic point of view that monooxo protactinyl cation, PaO3+, is a preferable species for Pa(V) in aqueous solution, although dioxo protactinyl cation, PaO2+, is not a feasible form. By an analysis of molecular orbitals, we revealed that 6d orbitals of Pa(V) destabilize the pi orbitals of PaO2+, because 6d-2p antibonding orbital conflicts with another 5f-2p bonding orbital. For stable dioxo uranyl cation, UO2(2+), we found that 6d orbitals of U(VI), in contrast, form a bonding orbital with the 2p orbitals, and this bonding orbital coexists at an angle with the 5f-2p bonding orbital due to an electron correlation.     

Formal Synthesis of Solanoeclepin A: Enantioselective Allene Diboration and Intramolecular [2+2] Photocycloaddition for the Construction of the Tricyclic Core

An enantioselective synthesis of an intermediate in the Tanino total synthesis of solanoeclepin A has been developed. The key step was an intramolecular [2+2] photocycloaddition, which led to the tricyclo[5.2.1.0^{1, 6}]decane core in six steps. The first photosubstrate, prepared through an indium‐mediated Barbier‐type reaction, gave an excellent [2+2] cycloaddition, but it could not be obtained in sufficient enantiopurity. The second photosubstrate, prepared through an asymmetric allene diborylation in high enantiomeric excess, gave the [2+2] cycloaddition product in high yield on irradiation at 365 nm on 20 g scale in a flow system. Other important steps were the replacement of a boronate group at the quaternary carbon by a vinyl group and diastereoselective cyclopropanation of an allylic alcohol.     

An efficient synthesis of the anti-asthmatic agent T-440: a selective N-alkylation of 2-pyridone

6,7-Diethoxy-1-[1-(2-methoxyethyl)-2-oxo-1,2-dihydropyridin- 4-yl]naphthalene-2,3-dimethanol [T-440, (1)] is a potential anti-asthmatic agent based on selective phosphodiesterase 4 inhibition. It was necessary for the further evaluation of 1 to develop an efficient synthetic route for 1, especially the construction of the 1-(2-methoxyethyl)-2-pyridone moiety. We examined an N-selective alkylation of pyridone derivative (2) in basic media. 2-Methoxyethylation of 2 with 2-methoxyethyl iodide utilizing LiH as the base gave predominantly an N-alkyl pyridone derivative (3a) in 82% yield (N/O-alkylation=92/8), which is compatible with an ab initio calculation of transition-state structures for the methylation of 2-pyridone. Single crystallization of a crude mixture of 3a and 4a furnished pure 3a, which is a key synthetic intermediate of 1.     

Synthesis and reactivity of 4-(2-chloro-5-nitrophenyl)-1,2,3-thiadiazole. A novel one-pot synthesis of N-substituted indole-2-thiols

4-(2-Chloro-5-nitrophenyl)-1,2,3-thiadiazole undergoes ring opening to produce a thioketene intermediate that reacts with an O- or N-nucleophile, forming an ester or an amide of the aryl-substituted thioacetic acid. Intermolecular cyclization of the thioacetic acid derivative via nucleophilic substitution of halogen in the aromatic ring gives an N-substituted indole-2-thiol (in case of an N-nucleophile) or a 2-alkoxy-substituted benzo[b]thiophene (in case of an O-nucleophile). The reaction is also applicable to the synthesis of heterocyclic analogues of N-substituted indole-2-thiols: 1-butyl-1,3-dihydropyrrolo[2,3-b]pyridine-2-thione was synthesized as an example. In the presence of potassium thioacetate (an S-nucleophile) 4-nitro-2-(1,2,3-thiadiazol-4-yl)benzenethiol is formed more quickly than thiadiazole ring opening occurs, making the heterocyclic ring tolerant toward the base.     

In-situ fabrication of dual porous titanium dioxide films as anode for carbon cathode based perovskite solar cell

We develop a dual porous(DP) TiO_2 film for the electron transporting layer(ETL) in carbon cathode based perovskite solar cells(C-PSCs). The DP TiO_2 film was synthesized via a facile PS-templated method with the thickness being controlled by the spin-coating speed. It was found that there is an optimum DP TiO_2 film thickness for achieving an effective ETL, a suitable perovskite/TiO_2 interface, an efficient light harvester and thus a high performance C-PSC. In particular, such a DP TiO_2 film can act as a scaffold for complete-filling of the pores with perovskite and for forming high-quality perovskite crystals that are seamlessly interfaced with Ti_O2 to enhance interfacial charge injection. Leveraging the unique advantages of DPTiO2 ETL, together with a dense-packed and pinhole-free TiO_2 compact layer, PCE of the C-PSCs has reached 9.81% with good stability.     

氧化碘苯间氨基苯甲酸锰(IV)四苯基卟啉配合物的合成

高价锰卟啉配合物在温和条件下分解水,释放氧,是植物光体体II的可能模型化合物.我们选择间氨基苯甲酸作为轴向配体,在二氯甲烷中用氧化碘苯氧化H2NC6H4COOMn(III)TPP相似文献   

Investigation of the asymmetric ionic Diels-Alder reaction for the synthesis of cis-decalins

The ionic Diels-Alder reaction, whereby an alpha,beta-unsaturated acetal in combination with a Lewis or Bronsted acid forms an equilibrium concentration of an activated dienophile, has been developed to provide an enantioselective synthesis of cis-decalins. Cyclohex-2-enone type chiral acetals of (2R,3R)-butane-2,3-diol have been screened against Lewis and Br?nsted acids with a variety of dienes and are efficient for the synthesis of a limited subset of cis-decalin structures. Diastereoselectivities of 73% and 82% have been found for the asymmetric ionic Diels-Alder reaction between the chiral acetal derivatives of cyclohex-2-enone (6) and 2-methylcyclohex-2-enone (18) with 2,3-dimethyl-1,3-butadiene (7). Terminal substituents on the diene partner in general render the system unreactive. However a synthetically useful cis-decalin 31, derived from the reaction of 2-methylcyclohex-2-enone and Z-3-t-butyldimethyl-silyloxypenta-1,3-diene has been prepared in enantiomerically pure form in 74% isolated yield using this asymmetric ionic Diels-Alder protocol.     

A general one-pot synthesis for elusive 2-substituted indenes: does bis[2-(tert-butyl)indenyl]zirconium(IV) dichloride/MAO polymerise ethene?

Among the 2-substituted indenes, 2-trifluoroindene and 2-tert-butylindene are poorly or incompletely described in the open literature. We herein describe an efficient one-pot synthesis of these compounds as a variation of the Perkin reaction which allows us to refute an earlier claim that bis(2-tert-butylindenyl)zirconium(IV) dichloride (2a) will not polymerise ethene. In fact, 2a/MAO polymerises ethene to extremely high molecular weights. Extensive DFT calculations on the polymerisation mechanism revealed an unprecedented suppression of the otherwise predominant chain termination by beta-hydride transfer due to steric congestion of the active site.     

Electricity from low-level H2 in still air--an ultimate test for an oxygen tolerant hydrogenase

We demonstrate an extreme test of O(2) tolerance for a biological hydrogen-cycling catalyst: the generation of electricity from just 3% H(2) released into still, ambient air using an open fuel cell comprising an anode modified with the unusual hydrogenase from Ralstonia metallidurans CH34, that oxidizes trace H(2) in atmospheric O(2), connected via a film of electrolyte to a cathode modified with the fungal O(2) reductase, laccase.     

Observation of anomalous C-O bond weakening on discandium and activation process to CO dissociation

Sc2[eta2(mu2-C,O)], the first homoleptic dinuclear metal carbonyl with an unprecedented bridging and side-on-bonded CO, generated from the reaction of laser-ablated Sc atoms with CO in a solid argon matrix, exhibits an unusually low C-O stretching frequency at 1193.4 cm-1, characteristic of an anomalously weakened C-O bond. This CO-activated molecule undergoes ultraviolet-visible photoinduced rearrangement to the CO-dissociated molecule, c-Sc2(mu-C)(mu-O). The infrared absorptions of the new molecules are accurately predicted by quantum chemical calculations, and the activation energy for the isomerization of Sc2[eta2(mu2-C, O)] to c-Sc2(mu-C)(mu-O) is calculated to be 15.10 kcal/mol. Our experimental and theoretical results schematically depict an activation process to CO dissociation.     

Highly coupled dyads based on phthalocyanine-ruthenium(II) tris(bipyridine) complexes. Synthesis and photoinduced processes

A new series of multicomponent ZnPc-Ru(bpy)(3) systems, 1a-c, consisting of a zinc-phthalocyanine linked through conjugated and/or nonconjugated connections to a ruthenium(II) tris(bipyridine) complex, has been synthesized. The ruthenium complexes 1a-c were prepared from phthalocyanines 2a-c, bearing a 4-substituted-2,2'-bipyridine ligand by treatment with [Ru(bpy)2Cl2].2H2O. Different synthetic strategies have been devised to prepare the corresponding dyad precursors (2a-c). Compound 2a, for example, with an ethenyl bridge, was synthesized by statistical condensation of 4-tert-butylphthalonitrile and 5-[(E)-2-(3,4-dicyanophenyl)ethenyl]-2,2'-bipyridine (3) in the presence of zinc chloride. Compounds 2b and 2c, having, respectively, an amide or an ethynyl bridge, were prepared following a different synthetic approach. The method involves the coupling of an appropriate 5-substituted-2,2'-bipyridine to an unsymmetrical phthalocyanine suitably functionalized with an amino (4) or an ethynyl group (5). The photophysical properties of the dyads that are ZnPc-Ru(bpy)3 1a-c and related model compounds have been determined by a variety of steady-state (i.e., fluorescence) and time-resolved methods (i.e., fluorescence and transient absorption). Clearly, intramolecular electronic interactions between the two subunits dominate the photophysical events following the initial excitation of either chromophore. These intramolecular interactions lead, in the case of photoexcited ZnPc, to faster intersystem crossing kinetics compared to a ZnPc reference, while photoexcited [Ru(bpy)3]2+) undergoes a rapid and efficient transduction of triplet excited-state energy to the Pc.     

Preparation of functionalized alkylmagnesium derivatives using an I/Mg-exchange

Functionalized alkylmagnesium reagents bearing an acetal, a ketal, an ester, or a pyridine ring were prepared by an I/Mg-exchange using iPr2Mg.LiCl or ClMg(CH2)5MgCl.2LiCl starting from functionalized primary alkyl iodides.     

Synthèse de quelques alcoxy-2 et aryloxy-2 dioxolannes-1,3

2-Methoxy, 2-ethoxy, and 2,2-diethoxy-1,3-dioxolanes, substituted in the 4,5 and in the 2 position by methyl or phenyl groups were obtained by an uncatalyzed reaction between a vicinal diol and an orthoester. An acid catalyst (p-toluene sulfonic acid) was necessary in order to obtain the 2-phenyl-2-methoxydioxolanes. 2-Phenoxydioxolanes were prepared by an exchange reaction between phenol and the corresponding 2-ethoxydioxolane.     

Asymmetric alternating copolymerization of cyclohexene oxide and CO2 with dimeric zinc complexes

Dimeric zinc complex 2a [ = Et(2)Zn(2)(1a)(2)] has been synthesized by the reaction of Et(2)Zn and (S)-diphenyl(pyrrolidin-2-yl)methanol (1a-H). X-ray crystallography revealed that the alkoxide ligand replaced one of the two ethyl groups of Et(2)Zn and formed a five-membered chelate ring through a Zn-N dative bond. Two zinc centers were bridged by oxygen atoms to form a Zn(2)O(2) four-membered ring with a syn relationship between the two ethyl groups on the zinc centers. Dimeric zinc complex 2a was an active catalyst for asymmetric alternating copolymerization of cyclohexene oxide and CO(2). An MALDI-TOF mass spectrum of the obtained copolymer showed that the copolymerization was initiated by the insertion of CO(2) into Zn-alkoxide to give [(S)-diphenyl(pyrroridin-2-ly)methoxy]-[C(=O)O-(1,2-cyclohexylene)-O](n)-H (copolymer I), including chiral ligand 1a as an initiating group. Complex 3a-OEt ( = EtZn(1a)(2)ZnOEt), in which an ethoxy group replaced one of the two ethyl groups in 2a, also polymerized cyclohexene oxide and CO(2) with higher catalytic activity and enantioselectivity than 2a and afforded EtO-[C(=O)O-(1,2-cyclohexylene)-O](n)-H ( = copolymer III), including an ethoxy group as an initiating group. Throughout the studies, dimeric zinc species are indicated to be the active species for the copolymerization. It is also depicted that the substituent on the aryl moiety in diaryl(pyrrolidin-2-yl)methanol 2b-e influenced the polymerization activity.     

并流淤浆混合法制备铜基甲醇合成催化剂及助剂Al2O3的作用研究

采用并流淤浆混合法制备了一系列具有不同铜锌铝比的铜基甲醇合成催化剂CuO/ZnO/Al2O3,测试了其催化性能(甲醇收率和CO转化率)及物相结构,并对该制备方法进行评价。Cu∶Zn∶Al摩尔比为4∶5∶1 的铜基催化剂显示了最好的催化活性。通过对催化剂前驱物煅烧过程进行DTA分析及对前驱物进行XRD分析表明, 催化剂前驱物的物相与Al2O3的量有关。当Al2O3的量较低时,前驱物的物相以(Cu0.3 Zn0.7)5(CO3)2(OH)6为主;当Al2O3的量较高时,前驱物中物相(Cu0.3Zn0.7)5(CO3)2(OH)6的量下降,而物相Cu2CO3(OH)2的量增加。物相(Cu0.3 Zn0.7)5(CO3)2(OH)6对终态催化剂的活性是十分有利的 。     

Pressure-induced structural, magnetic, and transport transitions in the two-legged ladder Sr3Fe2O5

The layered compound SrFeO(2) with an FeO(4) square-planar motif exhibits an unprecedented pressure-induced spin state transition (S = 2 to 1), together with an insulator-to-metal (I-M) and an antiferromagnetic-to-ferromagnetic (AFM-FM) transition. In this work, we have studied the pressure effect on the structural, magnetic, and transport properties of the structurally related two-legged spin ladder Sr(3)Fe(2)O(5). When pressure was applied, this material first exhibited a structural transition from Immm to Ammm at P(s) = 30 ± 2 GPa. This transition involves a phase shift of the ladder blocks from (1/2,1/2,1/2) to (0,1/2,1/2), by which a rock-salt type SrO block with a 7-fold coordination around Sr changes into a CsCl-type block with 8-fold coordination, allowing a significant reduction of volume. However, the S = 2 antiferromagnetic state stays the same. Next, a spin state transition from S = 2 to S = 1, along with an AFM-FM transition, was observed at P(c) = 34 ± 2 GPa, similar to that of SrFeO(2). A sign of an I-M transition was also observed at pressure around P(c). These results suggest a generality of the spin state transition in square planar coordinated S = 2 irons of n-legged ladder series Sr(n+1)Fe(n)O(2n+1) (n = 1, 2, 3, ...). It appears that the structural transition independently occurs without respect to other transitions. The necessary conditions for a structural transition of this type and possible candidate materials are discussed.     

Titanium(III) trisamidotriazacyclononane: reactions with C60 and radicals

The reaction of titanium trisamidotriazacyclononane, [Ti{N(Ph)SiMe2}3tacn] (1), with C60 led to the synthesis of [Ti{N(Ph)SiMe2}3tacn]C60 (2) in high yield. Treatment of 2 with PhCH2Br led to the formation of [Ti{N(Ph)SiMe2}3tacn]Br and the radical PhCH2C60 (3). The reaction of CH3I with 1 gives two products. One is [Ti{N(Ph)SiMe2}3tacn]I (4), which results from the oxidation of 1 by an I radical. The other product, 5, resulting from a multistep reaction scheme that involves redox and nucleophilic reactions, presents an imido ligand formed by ligand rearrangement upon C-N bond cleavage. In solution, an exchange process that corresponds to a reversible 1,3-silyl shift between two Ti-bonded N atoms leads to isomers 5a and 5b. This equilibrium transforms an imido (TiNPh) into an amido ligand (Ti{NPh}SiMe2CH2Ph) with concomitant generation of an anionic moiety in the originally neutral triazacyclononane ring. In solution, either 5a or 5b displays additional fluxional processes that consist of its corresponding racemization processes.     

Synthesis of functionalized hydroquinones via [Cp*RuCl2]2-catalyzed cocyclization of alkynes, alpha,beta-unsaturated carbonyl compounds, and carbon monoxide

[reaction: see text] Catalytic [2 + 2 + 1 + 1] cocyclization reaction of an alkyne, an alkene, and two molecules of carbon monoxide, leading to functionalized hydroquinones, was studied. Using [Cp*RuCl2]2 as a catalyst, we found that a variety of electron-deficient alkenes, such as alpha,beta-unsaturated ketones, esters, amides, and nitriles, can be employed as an alkene coupling partner to give the corresponding hydroquinones.