Carbene Rearrangements Unsurpassed: Details of the C(7)H(6) Potential Energy Surface Revealed

The rearrangement of phenylcarbene (1) to 1,2,4,6-cycloheptatetraene (3) has been studied theoretically, using SCF, CASSCF, CASPT2N, DFT (B3LYP), CISD, CCSD, and CCSD(T) methods in conjunction with the 6-31G, 6-311+G, 6-311G(2d,p), cc-pVDZ, and DZd basis sets. Stationary points were characterized by vibrational frequency analyses at CASSCF(8,8)/6-31G and B3LYP/6-31G. Phenylcarbene (1) has a triplet ground state ((3)A") with a singlet-triplet separation (DeltaE(ST)) of 3-5 kcal mol(-)(1). In agreement with experiment, chiral 3 is the lowest lying structure on this part of the C(7)H(6) potential energy surface. Bicyclo[4.1.0]hepta-2,4,6-triene (2) is an intermediate in the rearrangement of 1 into 3, but it is unlikely to be observable experimentally due to a barrier height of only 1-2 kcal mol(-)(1). The enantiomers of 3 interconvert via the (1)A(2) state of cycloheptatrienylidene (4) with an activation energy of 20 kcal mol(-)(1). The "aromatic" (1)A(1) state, previously believed to be the lowest singlet state of 4, is roughly 10 kcal mol(-)(1) higher in energy than the (1)A(2) state, and, in violation of Hund's rule, (3)A(2) is also calculated to lie above (1)A(2) in energy. Thus, even if (3)A(2) were populated, it is likely to undergo rapid intersystem crossing to (1)A(2). We suggest (3)B(1)-4 is the metastable triplet observed by EPR.     

Electronic effects of 1-(1, 7-B6H6C2H) and 1-(1,6-B7H7C2H) groups

Conclusions 1-[1,7-Dicarbaclozooctaboran(8)yl] (induction constant _i=0.08 and resonance constant _R°=–0.02) and 1-[1,6-dicarbaclozononaboran(9)yl] (=0.09 and _R°=0.05) groups are weak electron-acceptor groupings.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 574–576, March, 1972.     

Theoretical Investigation of the C2H2B2 Potential Energy Surface

Fifteen unique energy minima and thirteen transition states on the C ₂H₂B₂ potential surface have been located and optimized at the MP2 level of theory with the 6-311G(d,p) basis set. The planar four-membered ring isomer , 1, an analog of cyclobutadiene, is a transition state lying 37 kcal/mol above the nonplanar four-membered ring , 3. The planar , 10, is the second most stable species found, lying 72.2 kcal/mol below 3. The nonplanar, butterfly-shaped ring, 4, is a local minimum 33.7 kcal/mol more stable than 3. A four-membered ring isomer with alternating boron–carbon locations, , 5, lies 67.0 kcal/mol below 3 and 33.3 kcal/mol below 4. The ring of 5 is planar with one hydrogen above and one below the plane (C _2h symmetry). The borylene-substituted boracyclopropene, , 8, is a planar local minimum lying 36.0 kcal/mol above 5. The most stable C₂H₂B₂ isomer found was the planar, four-membered ring system 22 (D _2h symmetry) composed of two BCC three-membered rings fused across the C-C bond. Structure 22 lies 22.2 kcal/mole below 10, 105.4 kcal/mol below 3, 71.7 kcal/mol below 4, and 38.2 kcal/mol below 5. Isomer 22 is the structural analog of the trialene form of C₄H₂. The most stable linear isomer, HB BH, 26, was surprisingly 50.5 kcal/mol less stable than 22. The stabilities of the two most stable cyclic isomers 10 and 22 may be explained by aromaticity.     

乙烯基自由基(C2H·3)与羟基自由基(OH·)反应势能面的理论研究

在QCISD（T）/6-311G（2df,p)//B3LYP/6-311G（d,p)水平上对自由基反应C2H3^. OH^.进行了计算，结果表明，经过缔合、多步H转移、CH3转移和离解等复杂过程，最终要得到8种产物（P1-P8），茯中产物P2（H2CCO H2）和P6（CH3CO^. H^.）是主要产物。本文得到的CH2CHOH（1或1‘），CH3CHO（2）和CH3COH（3）之间的过渡态TS1/2，TS1‘/3和TS2/3的能量顺序与Wesdemiotis等的实验推测相反，而与Smith等的计算结果一致。     

Investigation of the Crystal Structure,Characterization, Hirshfeld Surface,and Theoretical Study of (C6H14N)5[HP2Mo5O23]·4H2O

The synthesis of an organoammonium diphosphopentamolybdates(VI), (C₆H₁₄N)₅[HP₂Mo₅O₂₃] · 4H₂O ( 1 ), is reportet. The molecular structure and spectroscopic analysis were performed using experimental techniques like X‐ray diffraction, FT‐IR, and UV/Vis. The single crystal analysis of the title compound shows that the compound crystallizes in the monoclinic crystal system with space group P2₁/c and cell constants of a = 12.7934(2) Å, b = 14.8145(2) Å, c = 27.2637(5) Å, and β = 92.9298(14)°. The Hirshfeld surfaces and the associated 2D fingerprint plots were investigated to study the intermolecular interactions in the crystal packing and this study has confirmed that the hydrogen bonding interactions play a dominating role in the stability of crystal structure. The theoretical calculations were done using PM3 semi‐empirical model and several properties were studied.     

乙炔基自由基(C2H·)与二氧化氮(NO2)气体反应势能面的理论研究

在 CCSD(T)/6-311G(d,p)//B3LYP/6-311G(d,p)+ZPE 水平上对反应C2H+NO2 进行了计算, 建立了反应势能面并得到了3种产物. 利用RRKM理论估算了反应的总速率和分支比. 总速率为1.427×10-12×T0.556×exp(190.547/T) cm3*molecule-1*s-1, 其中主要产物P1(HCCO+NO)比例大于96%, 次要产物P2(HCNO+CO)和P3(HCN+CO2)小于4%.     

H+HCNO反应势能面的理论研究

在CCSD(T)/6-311G(d,p)//B3LYP/6-311G(d,p)+ZPVE水平下, 对反应H＋HCNO进行了研究. 建立了反应势能面, 揭示了该反应的反应机理, 通过H迁移、N—O键或C—N键断裂等多步反应, 得到4种产物, 其中最主要产物为P1(HCN+OH).     

[C6H6, C3H7 +]and [C6H7 +, C3H6] ion-neutral complexes intermediate in the reactions of protonated propylbenzenes

From the mass-analysed ion kinetic energy spectra of labelled ions, kinetic energy releases and thermodynamic data, it is proved that protonated n-propylbenzene (1) isomerizes into protonated isopropyl benzene (2). It is also shown that the dissociation of the less energetic metastable ions of (2), leading to [iso-C₃H₇]⁺ and [C₆H₇]⁺ product ions, is preceded by H exchange. This H exchange involves two interconverting ion-neutral complexes [C₆H₆, iso-C₃H₇⁺] (2π) and [C₆H₇⁺, C₃H₆] (2α).     

二氧化钛(TiO2)表面能的理论研究

用密度泛函理论和虚拟原子轨道方法对二氧化钛-金红石(TiO2)(110)表面的表面能进行了理论计算. 结果表明, 二氧化钛的表面能与表面缺陷的百分率相关. 完整的表面具有最低的表面能, 表面能随着表面缺陷百分率的增大而升高, 这与自然环境下二氧化钛-金红石(TiO2)具有规整的(110)表面一致. 在光催化实验中利用二氧化钛表面的缺陷作催化剂需要考虑到表面的稳定性. 另一方面, 在完整的表面五配位Ti4+上填加氧原子与表面作用时, 表面能起初变化很小, 直到50%的五配位Ti4+被填充后表面能才开始升高.     

叠氮化合物C6H6-n(N3)n(n=1~6)的密度泛函理论研究

运用密度泛函理论, 在B3LYP/6-31G*水平上, 对叠氮化合物C6H6-n(N3)n(n=1~6)进行理论计算, 并对所得到的几何结构进行了振动频率分析. 计算结果表明, 这些化合物是热力学稳定的. 基于自然键轨道理论, 分析了稳定结构的电荷分布及成键情况. 在不破坏苯环和叠氮基的原则下, 设计等键反应计算了这些化合物的生成热, 结果表明, 标题化合物的生成热都很高, 且随着叠氮基数目的增加而线性增大.     

Theoretical study of the structure of protonated ethane (C2H 7 + )

The floating spherical gaussian orbital method is employed for predicting the shape of C₂H ₇ ⁺ . The pentavalency of carbon may be explained by the presence of a two-electron three-centre bond in addition to the standard two-electron two-centre bonds in this ion.Aided by a research grant to The Johns Hopkins University from the National Institutes of Health.The auther is grateful to Professor Robert G. Parr for his kind interest in this work.     

A new method for investigating infrared spectra of protonated benzene (C6H7+) and cyclohexadienyl radical (c-C6H7) using para-hydrogen

We use protonated benzene (C(6)H(7)(+)) and cyclohexadienyl radical (c-C(6)H(7)) to demonstrate a new method that has some advantages over other methods currently used. C(6)H(7)(+) and c-C(6)H(7) were produced on electron bombardment of a mixture of benzene (C(6)H(6)) and para-hydrogen during deposition onto a target at 3.2 K. Infrared (IR) absorption lines of C(6)H(7)(+) decreased in intensity when the matrix was irradiated at 365 nm or maintained in the dark for an extended period, whereas those of c-C(6)H(7) increased in intensity. Observed vibrational wavenumbers, relative IR intensities, and deuterium isotopic shifts agree with those predicted theoretically. This method, providing a wide spectral coverage with narrow lines and accurate relative IR intensities, can be applied to larger protonated polyaromatic hydrocarbons and their neutral species which are difficult to study with other methods.     

Theoretical study of the low-lying States of Fe2-(C6H6)3

Using the gradient-corrected BPW91 method and 6311++G(2d,2p) basis sets, it was found that adsorption of benzene by iron atoms forms a multiple-decker sandwich (MDS) geometry for the ground state (GS) of Fe(2)-(C(6)H(6))(3), as Fe(2) is broken. Though decoordination occurs, the ligands are bonded symmetrically to the Fe sites by η(6) (for the two external rings) and two η(3) (for the central ring) Fe-C coordinations; this big amount of Fe-C bonds enhances the stability of the MDS GS. This is unexpected, as the experiment suggests MDS for TM(n)-(C(6)H(6))(m) species of earlier transition metals (TMs) and clusters covered with benzene, i.e., rice-ball (RB) structures, for late 3d atoms. However, preserving Fe(2), an RB state was found, quasi-degenerate with the GS, with a smaller amount of Fe-C contacts and a stronger Fe(2) bond. The MDS shows higher stability for electron attachment and deletion events, but its adiabatic electron affinity, 1.11 eV, differs more from the experiment (0.80 ± 0.1 eV) than the one (0.97 eV) for RB. Thus, MDS and RB states can appear in a sample of Fe(2)-(C(6)H(6))(3). Like the electron affinity, the ionization energy of the complex is also smaller than those of the metal and benzene moieties, but closer to the former, signifying that the electron, delocalized through the 3d-π bonds, is mainly deleted from the metallic units.     

M+(C6H6复合物结构与成键性质的理论研究

应用密度泛函理论和多体微扰理论,对阳离子与苯形成的配合物M+-C6H6 (M = H+、Li+、Na+、K+、B+、Al+、Ga+、Mg+、Ca+、Mg2+、Ca2+)的平衡几何构型、稳定性和成键性质进行了研究。计算结果表明,H+-C6H6只能形成稳定的s配合物,而其它阳离子体系只能形成稳定的p 配合物。基于自然键轨道和相关前线分子轨道分析,讨论了阳离子-p 相互作用的本质。