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161.
2-Oxa-7-azaspiro[4.4]nonane-8,9-diones were newly synthesized in good yields by the Mn(III)-based reaction of a mixture of 1,1-diarylethenes and 4-acylpyrrolidine-2,3-diones. Under the stated reaction conditions, the pyrrolidinedione ring remained intact and became one of the two rings of the 2-oxa-7-azaspiro[4.4]nonanedione scaffold. The procedure was simple and the product was easily separated. The structure determination and the mechanism for the formation of the 2-oxa-7-azaspiro[4.4]nonanediones were also discussed. 相似文献
162.
Can Tetrylone Act in a Similar Fashion to Tetrylene in Ni(CO)2 Complexes? A Theoretical Study based on a Comparison using DFT Calculations
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Thi Ai Nhung Nguyen Duc Sy Tran Thi Phuong Loan Huynh Thi Hoa Le Tuan Quang Duong Tien Trung Nguyen Thanh Cong Vo Van Tat Pham Tan Hiep Dang 《无机化学与普通化学杂志》2017,643(13):826-838
A comparison was made to investigate the structures and bonding of nickel complex that carry tetrylone and tetrylene ligands [(CO)2Ni‐{E(PH3)2}] ( Ni1E ) and [(CO)2Ni‐{NHEMe}] ( Ni2E ) (E = C to Pb) using quantum chemical calculations at the BP86 level with various basis sets (SVP, TZVPP, TZ2P+). The nature of the Ni–E bonds was analyzed with charge‐ and energy decomposition methods. The structures of tetrylone complexes Ni1E exhibit an interesting trend with the ligands E(PH3)2 are bonded in a tilted orientation relative to the fragment Ni(CO)2. In contrast, the calculated equilibrium structures of complexes Ni2E exhibit the NHEMe ligands (E = C to Sn) bonded in a head‐on way to the Ni(CO)2 fragment, while the bending angle gives the strongest side‐on bonded ligand NHPbMe when E = Pb. The interesting trend of the bond dissociation energy (BDE) is observed for the tetrylone, which has the same trend BDEs compared with tetrylene complexes. The EDA‐NOCV results indicate that the tetrylone ligands {E(PH3)2} in complexes are similar to the tetrylene ligands NHEMe as strong σ‐donors and weak π‐acceptors. The BDEs calculated for the Ni–E bonds in Ni1E and Ni2E show that the effect of bulky ligands may obscure the intrinsic Ni–E bond strength. The bonding analysis shows that the tetrylone ligands in Ni1E may act in a similar fashion to the tetrylene ligands in Ni2E . All complexes Ni1E and Ni2E are suitable targets for synthesis. 相似文献
163.
The first pyrazolin-4-ylidene complexes of palladium(II) have been synthesized by oxidative addition of 4-iodopyrazolium salts to Pd(2)(dba)3/PPh(3) and were fully characterized by multinuclear NMR spectroscopies, ESI mass spectrometry and X-ray diffraction studies. 相似文献
164.
Pascual Winter MF Rozas G Fainstein A Jusserand B Perrin B Huynh A Vaccaro PO Saravanan S 《Physical review letters》2007,98(26):265501
Femtosecond pump-probe experiments on a Ga0.85In0.15As nanocavity enclosed by two Ga(0.85)In(0.15)As/AlAs phonon Bragg mirrors reveal selective generation of terahertz confined acoustic modes and regular folded phonons. Selective generation of the confined modes alone is achievable for laser excitation at certain energies below the mirror absorption edges, corresponding to electronic transitions within the cavity layer only. Calculations based on the photoelastic effect explain the experimental results. Decay times of cavity and regular modes evidence longer decay times and anharmonic effects for the cavity mode. 相似文献
165.
We prepare CdS/CdSe/ZnS thin films by successive ionic layer adsorption and reaction method. Results show a wider photoresponse range of TiO2 mesopores from the ultraviolet region to the visible light region. Sequentially assembled CdS/CdSe/ZnS quantum and photocurrent efficiency. A high efficiency of dots exhibit significantly improved light-harvesting ability 1.059354% is obtained. 相似文献
166.
Text
We compare the L-Function Ratios Conjecture?s prediction with number theory for quadratic twists of a fixed elliptic curve, showing agreement in the 1-level density up to for test functions supported in (−σ,σ), giving a power-savings for σ<1. This test introduces complications not seen in previous cases (due to the level of the elliptic curve). The results here are a key ingredients in Dueñez et al. (preprint) [DHKMS2], which determine the effective matrix size for modeling zeros near the central point. The resulting model beautifully describes the behavior of these low lying zeros for finite conductors, explaining data observed in Miller (2006) [Mil3]. A key ingredient is generalizing Jutila?s bound for quadratic character sums restricted to fundamental discriminant congruent to non-zero squares modulo a square-free integer. Another application is determining the main term in the 1-level density of quadratic twists of a fixed GLn form; this generalization was implicitly assumed in Rubinstein (2001) [Rub].Video
For a video summary of this paper, please click here or visit http://www.youtube.com/watch?v=-Cbj1n5y-WE. 相似文献167.
Reaction of phosphine oxides R(3)P═O [R = Me (1a), Et (1c), (i)Pr (1d) and Ph (1e)], with the bromophosphoranimines BrPR'R'P═NSiMe(3) [R' = R' = Me (2a); R' = Me, R' = Ph (2b); R' = R' = OCH(2)CF(3) (2c)] in the presence or absence of AgOTf (OTf = CF(3)SO(3)) resulted in a rearrangement reaction to give the salts [R(3)P═N═PR'R'O-SiMe(3)]X (X = Br or OTf) ([4]X). Reaction of phosphine oxide 1a with the phosphoranimine BrPMe(2)═NSiPh(3) (5) with a sterically encumbered silyl group also resulted in the analogous rearranged product [Me(3)P═N═PMe(2)O-SiPh(3)]X ([8]X) but at a significantly slower rate. In contrast, the direct reaction of the bulky tert-butyl substituted phosphine oxide, (t)Bu(3)P═O (1b) with 2a or 2c in the presence of AgOTf yielded the phosphine oxide-stabilized phosphoranimine cations [(t)Bu(3)P═O·PR'(2)═NSiMe(3)](+) ([3](+), R' = Me (d), OCH(2)CF(3) (e)). A mechanism is proposed for the unexpected formation of [4](+) in which the formation of the donor-stabilized adduct [3](+) occurs as the first step. 相似文献
168.
Density functional and coupled cluster calculations on neutral monodehydro[12]annulenes (C(12)H(10)) reveal a global minimum that should be kinetically stable. At the CCSD(T)/cc-pVDZ//BHLYP/6-31G* level, the unsymmetrical CTCTC conformer 1a lies at least 3 kcal/mol below all other isomers studied. The two isomers closest in energy to 1a are Mo?bius structure 5a (CCTCC) and all-cis 6a. Isomer 1a can undergo conformational automerization with E(a) = 3.9 kcal/mol, implying that this process would be rapid on the NMR time scale, and computed (1)H NMR parameters (GIAO-B3LYP/6-311+G**//RHF/6-31G*) are presented. Cumulenic dehydro[12]annulene isomers, with 1,2,3-butatriene subunits, were found to be reactive intermediates in the interconversion of different configurations of the alkyne forms. Pathways for configuration change of 1a, and for subsequent rearrangement to biphenyl, were investigated. The 28 kcal/mol overall barrier for the lowest energy pathway connecting 1a to biphenyl suggests that 1a is kinetically stable with respect to valence isomerization. 相似文献
169.
Bridge cleavage reactions of the dimeric monocarbene complex [PdBr(2)((i)Pr(2)-bimy)](2) can be effectively used to end-cap pyridine containing pseudorotaxanes affording stable [2]rotaxanes. 相似文献
170.
Villano SM Huynh LK Carstensen HH Dean AM 《The journal of physical chemistry. A》2011,115(46):13425-13442
The reactions of alkyl peroxy radicals (RO(2)) play a central role in the low-temperature oxidation of hydrocarbons. In this work, we present high-pressure rate estimation rules for the dissociation, concerted elimination, and isomerization reactions of RO(2). These rate rules are derived from a systematic investigation of sets of reactions within a given reaction class using electronic structure calculations performed at the CBS-QB3 level of theory. The rate constants for the dissociation reactions are obtained from calculated equilibrium constants and a literature review of experimental rate constants for the reverse association reactions. For the concerted elimination and isomerization channels, rate constants are calculated using canonical transition state theory. To determine if the high-pressure rate expressions from this work can directly be used in ignition models, we use the QRRK/MSC method to calculate apparent pressure and temperature dependent rate constants for representative reactions of small, medium, and large alkyl radicals with O(2). A comparison of concentration versus time profiles obtained using either the pressure dependent rate constants or the corresponding high-pressure values reveals that under most conditions relevant to combustion/ignition problems, the high-pressure rate rules can be used directly to describe the reactions of RO(2). 相似文献