Vibrational Spectra, DFT Calculations, and Assignments of the syn and the gauche Forms of Vinylphosphine

Infrared spectra (3500-600 cm(-1)) of vinylphosphine and its P-dideuterated derivative in the gas phase were recorded at 1 cm(-1) resolution. Both the infrared absorption bands of the syn and gauche conformers of the vinylphosphine were observed and assigned. The assignment was based on density functional theory calculations performed at the B3LYP/6-311G(d) level. The agreement between calculated and observed frequencies for both CH(2)&dbond;CHPH(2) and CH(2)&dbond;CHPD(2) was fairly good. The integrated intensities of isolated and overlapping vibrational bands were determined experimentally. Copyright 2001 Academic Press.     

Generation, Microwave Spectrum, Barrier to Internal Rotation of Methyl Group, and ab Initio MO Calculation of syn-2-Nitrosopropene, syn-CH(2)&dbond;C(CH(3))&bond;N&dbond;O

syn-2-Nitrosopropene was generated, in the gas phase, by chemical reaction of 1-chloro-2-(hydroxyimino)propane with K(2)CO(3) and identified by microwave spectroscopy. The microwave spectrum of the reaction product was observed in the frequency range from 8.0 to 40.0 GHz. The rotational constants (MHz) were determined as A = 8744.09(6), B = 4846.07(2), and C = 3177.84(3) for CH(2)&dbond;C(CH(3))&bond;(14)NO (normal species) and A = 8664.36(5), B = 4822.15(3), and C = 3157.04(3) for CH(2)&dbond;C(CH(3))&bond;(15)NO ((15)N species) in the ground vibrational state. The values of the planar moment (P(cc) = (I(a) + I(b) - I(c))/2) obtained for the normal and (15)N species were 1.525(1) and 1.526(1) u ?(2), respectively. This suggests that the nitrogen atom lies in or is close to the ab inertial plane of the molecule and shows also that only two hydrogen atoms are located symmetrically out of the symmetry plane. The reaction product was determined to be syn-2-nitrosopropene by comparing the observed and calculated rotational constants, kappa (Ray's asymmetry parameter) and r(s) coordinates of the nitrogen atom. The dipole moments (D) were determined to be μ(a) = 2.43(5), μ(b) = 1.12(7), and μ(total) = 2.67(7). The barrier heights of the internal rotation owing to the methyl group of the normal species in the ground and first excited torsional states were determined to be 1750(50) and 1740(50) cal/mol (1 cal/mol = 4.184 J/mol), respectively. The (14)N nuclear quadrupole coupling constants (MHz) were determined to be chi(aa) = 0.25(21), chi(bb) = -7.11(40), and chi(cc) = 6.85(61). Two vibrational excited states were observed and the vibrational frequencies (cm(-1)) of the C-N and C-C torsional modes were determined to be 160(40) and 175(40), respectively. The lifetime of syn-2-nitrosopropene was found to be ca. 2 min in the waveguide cell. Copyright 2000 Academic Press.     

Infrared and EPR Spectroscopic Studies of 2-C(2)H(2)F and 1-C(2)H(2)F Radicals Isolated in Solid Argon

2-fluorovinyl radicals were generated in solid argon by solid-state chemical reactions of mobile F atoms with acetylene and its deuterated analogues. Highly resolved EPR spectra of the stabilized radicals CHF&dbond;(*)CH, CDF&dbond;(*)CD, CHF&dbond;(*)CD, and CDF&dbond;(*)CH were obtained for the first time. The observed spectra were assigned to cis-2-fluorovinyl radical based on excellent agreement between the measured (a(F) = 6.50, a(betaH) = 3.86, a(alphaH) = 0.25 mT) hyperfine constants and those calculated using density functional (B3LYP) theory. Analogous experiments carried out using infrared spectroscopy yielded a complete assignment of the vibrational frequencies. An unusual reversible photochemical conversion is observed in which cis-2-fluorovinyl radicals can be partially converted to 1-fluorovinyl radicals by pulsed laser photolysis at 532 nm. Photolysis at 355 nm converts 1-fluorovinyl back to cis-2-fluorovinyl. High-resolution EPR and infrared spectra of 1-fluorovinyl were obtained for the first time. The measured hyperfine constants (a(F) = 13.71, a(H1) = 4.21, a(H2) = 1.16 mT) are in good agreement with calculated values. Copyright 2001 Academic Press.     

Characterization of microporous aluminophosphate IST-1 using (1)H Lee-Goldburg techniques

The presence of two independent methylamine species in microporous aluminophosphate IST-1 (|(CH(3)NH(2))(4)(CH(3)NH(+)(3))(4)(OH(-))(4)|[Al(12)P(12)O(48)]) has been shown previously by synchrotron powder X-ray diffraction. One of these species, [N(1)-C(1)], links to a six-coordinated framework Al-atom [Al(1)], while the other methylamine [N(2)-C(2)] is protonated and hydrogen-bonded to three O-atoms [O(1), O(2) and O(12)]. We revisit the structure of IST-1 and report the complete assignment of the (1)H NMR spectra by combining X-ray data and high-resolution heteronuclear/homonuclear solid-state NMR techniques based on frequency-switched Lee-Goldburg homonuclear decoupling and (31)P-(31)P homonuclear recoupling. Careful analysis of the 2D (1)H-X homonuclear correlation (X=(1)H) and 2D heteronuclear correlation (X=(13)C, (31)P and (27)Al) spectra allowed the distinction of both methylamine species and the assignment of all (31)P and (13)C resonances. For the first time at a relatively high (9.4 T) magnetic field, symmetric doublet patterns have been observed in the (13)C spectra, caused by the influence of the (14)N second-order quadrupolar interaction.     

Geometry‐based analysis of azulene and azulene‐like systems with H‐ or Li‐bonding

B3LYP/6–311+G** optimization was carried out for azulene and its analogs, in which CH? CH? CH fragment was replaced with O···X···O (X = H or Li). π‐electron delocalization in four possible derivatives with H‐bonding and three possible derivatives with Li‐bonding was described by the use of HOMA index. All derivatives with Li‐bonding exhibit high π‐electron delocalization similar to that found for azulene. Among four H‐bonded systems, two exhibit lower π‐electron delocalization (HOMA < 0.39) and higher total electron energy than the other two derivatives. Copyright © 2007 John Wiley & Sons, Ltd.     

Substituent effect on electron affinity,gas‐phase basicity,and structure of monosubstituted propargyl radicals and their anions: a theoretical study

The substituent effect of electron‐withdrawing groups on electron affinity and gas‐phase basicity has been investigated for substituted propargyl radicals and their corresponding anions. It is shown that when a hydrogen of the α‐CH₂ group or acetylenic CH in the propargyl system is substituted by an electron‐withdrawing substituent, electron affinity increases, whereas gas‐phase basicity decreases. The calculated electron affinities are 0.95 eV (CH?C? CH₂?), 1.15 eV (CH?C? CHF?), 1.38 eV (CH?C? CHCl?), 1.48 eV (CH?C? CHBr?) for the isomers with terminal CH and 1.66 eV (CF?C? CH₂?), 1.70 eV (CCl?C? CH₂?), 1.86 eV (CBr?C? CH₂?) for the isomers with terminal CX at B3LYP level. The calculated gas‐phase basicities for their anions are 378.4 kcal/mol (CH?C? CH₂:^?), 371.6 kcal/mol (CH?C? CHF:^?), 365.1 kcal/mol (CH?C? CHCl:^?), 363.5 kcal/mol (CH?C? CHBr:^?) for the isomers with terminal CH and 362.6 kcal/mol (CF?C? CH₂:^?), 360.4 kcal/mol (CCl?C? CH₂:^?), 356.3 kcal/mol (CBr?C? CH₂:^?) for the isomers with terminal CX at B3LYP level. It is concluded that the larger the magnitude of electron‐withdrawing, the greater is the electron affinity of radical and the smaller is the gas‐phase basicity of its anion. This tendency of the electron affinities and gas‐phase bacisities is greater in isomers with the terminal CX than isomers with the terminal CH. Copyright © 2009 John Wiley & Sons, Ltd.     

Trends in adsorption of open-shell atoms and small molecular fragments on the Ag(1 1 1) surface

The chemisorption of various atoms (C, N, O, Cl) and molecular fragments (OH, NH, CH, NH₂, CH₂) on the Ag(1 1 1) surface has been studied by employing the embedded cluster and multireference single- and double-excitation configuration interaction (MRD-CI) methods. Ground and excited states of the cluster-adsorbate systems have been computed and molecular orbitals (MOs) as well as electronic charge density distributions and Mulliken populations have been analyzed in order to extract general trends in chemisorption properties for different adsorbates. It has been found that the adsorbate-surface bond is energetically most favorable when a maximum of two electrons of the metal are shared with a given adsorbate. As a result atomic/molecular fragments with less than six valence electrons (N, CH, C) retain some open shells upon adsorption, whereas oxygen as well as chlorine isovalent species form a singlet ground state on the surface. All species considered except for Cl have mainly covalent bonding character to the surface, with an electronic charge of up to 1.0 transferred to the adsorbate from the silver cluster. It has been shown that the ionicity of the bond is strongly correlated with the electron affinity of the adsorbed species. Binding energies, equilibrium geometry and adsorbate location on the cluster have been computed and compared with available experimental data. In addition, the characteristic properties of chemisorption on Ag(1 1 1) and Pt(1 1 1) surfaces have been compared.     

Substituent effects on the 13C NMR chemical shifts of the imine carbon in N‐(4‐X–benzylidene)‐4‐(4‐Y–styryl) anilines

Long‐range electronic substituent effects were targeted using the substituent dependence of δ_C(C═N), and specific cross‐interactions were explored extendedly. A wide set of N‐(4‐X–benzylidene)‐4‐(4‐Y–styryl) anilines, p‐X–C₆H₄CH═NC₆H₄CH═CHC₆H₄–p‐Y (X = NMe₂, OMe, Me, H, Cl, F, CN, or NO₂; Y = NMe₂, OMe, Me, H, Cl, or CN) were prepared for this study, and their ¹³C NMR chemical shifts δ_C(C═N) of C═N bonds were measured. The results show that both the inductive and resonance effects of the substituents Y on the δ_C(C═N) of p‐X–C₆H₄CH═NC₆H₄CH═CHC₆H₄–p‐Y are less than those of the substituents Y in p‐X–C₆H₄CH═NC₆H₄–p‐Y. Moreover, the sensitivity of the electronic character of the C═N function to electron donation/electron withdrawal by the substituent X or Y attenuates as the length of the conjugated chain is elongated. It was confirmed that the substituent cross‐interaction is an important factor influencing δ_C(C═N), not only when both X and Y are varied but also when either X or Y is fixed. The long‐range transmission of the specific cross‐interaction effects on δ_C(C═N) decreases with increasing conjugated distance between X and Y. The results of this study suggest that there is a long‐range transmission of the substituent effects in p‐X–C₆H₄CH═NC₆H₄CH═CHC₆H₄–p‐Y. Copyright © 2012 John Wiley & Sons, Ltd.     

双轴应变调控二维单层C2X2TM（X = O, H; TM=Fe, Cr） 的多铁性研究

基于密度泛函理论的第一性原理计算,系统地研究了过渡金属原子插层的单层氧化/氢化石墨烯的磁学性质和铁电性质.在考虑了电子在位库仑作用和自旋轨道耦合作用下,得到了过渡金属Fe、Cr插层形成的C₂X₂TM二维单层膜的稳定结构以及基态磁性结构,研究了不同应变作用下C₂X₂TM的磁性、能带、铁电极化以及电子结构的变化.结果发现,对于任何应变下的C₂X₂TM其基态磁性都为手性逆时针反铁磁结构.在无应变时体系存在一个较大的离子翻转势垒,通过外加双轴应变,可有效调控体系的势垒高度和能隙,发现25%应变下C₂O₂Cr和30%应变时C₂O₂Fe单层薄膜具有与GeS等二维铁电材料相近的铁电极化和翻转势垒,这些研究结果表明C₂O₂Fe(Cr)单层薄膜是一种新型二维多铁性材料.     

取代基效应对二芳基硝酮CH=N(O)桥基1H NMR化学位移的影响

合成一系列取代二芳基硝酮XArCH=N（O）ArY化合物,测定其核磁共振氢谱（¹H NMR）,指认出桥基CH=N（O）上质子的化学位移δH[CH=N（O）],定量研究取代基效应对δH[CH=N（O）]的影响.得到一个4参数定量方程,标准偏差（S）为0.020,较好地表达了δH[CH=N（O）]的变化规律.结果表明,该类化合物的δH[CH=N（O）]主要受4个因素影响：X基团的场/诱导效应[σ_F（X）];Y基团的共轭效应[σ_R（X）];基团X和Y之间的特殊交叉作用（Δσ²）;以及基团X和O^-之间的特殊交叉作用[Δσ²_（X-O^-）].其中,Δσ²_（X-O^-）对δ_{H[CH=N（O）]}变化的贡献超过70%.通过δH[CH=N（O）]与二芳基希夫碱XArCH=NArY桥基CH=N上质子化学位移的δH（CH=N）比较发现,这两类化合物桥基上质子的化学位移之间没有良好的线性关系.因而,在应用NMR谱图解析有机化合物分子结构时,不能简单地用δH（CH=N）的变化去类比δ_{H[CH=N（O）]}的变化.     

Excited‐state hydrogen bonding dynamics of pyruvic acid and geminal‐diol, 2,2‐dihydroxypropanoic acid in aqueous solution: a DFT/TDDFT study

In this work, we present the optimized ground state geometrical structures, electronic excitation energies and corresponding oscillation strengths of the low‐lying electronically excited states for the isolated Tce‐CH3COCOOH and Tce‐CH3C(OH)2COOH as well as their corresponding hydrogen‐bonded dimers Tce‐CH3COCOOH‐H2O and Tce‐CH3C(OH)2COOH‐H2O through time‐dependent density functional theory method. It is found that the intermolecular hydrogen bonds C=O···H‐O are strengthened in the electronically excited states of the hydrogen‐bonded dimers Tce‐CH3COCOOH‐H2O and Tce‐CH3C(OH)2COOH‐H2O, in that the excitation energies of the related excited states for the hydrogen‐bonded dimers are decreased compared with those of the corresponding monomers. The calculated results are consistent with the rules that are first demonstrated by Zhao on the excited‐state hydrogen bonding dynamics. Copyright © 2012 John Wiley & Sons, Ltd.     

时间分辨红外发射光谱法对自由基反应的研究

在过去的 15年中 ,傅立叶变换红外发射光谱法广泛应用于研究气相自由基反应 .Sloan首先研究了O(1D)的反应 ,随后Leone和Hancock研究了O(3 P)的反应 .此后 ,孔繁敖和朱起鹤等研究了小自由基 ,包括CH、CH2 、CH3 、C2 H3 、C2 H5、C2 H、C3 H3 和C3 H5与O2 、NO、N2 O、NO2 等分子的反应。在红外光谱中观察到各个反应的初生产物和初步反应通道 ,和从头算的理论研究结合起来 ,这些反应的机理已基本弄清 .     

利用发射光谱研究脉冲电晕放电中的自由基

利用发射光谱技术在大气压下测量了以氮气为载气的不饱和水蒸气体系针-板式正脉冲电晕放电产生的OH(A^2∑→X^2Ⅱ0—O)自由基和O(3p^5P→3s^5S^02777．4nm),Ha(3P→2S 656．3nm)活性原子的发射光谱,并由N2(C^3Ⅱu→B^3Ⅱg)的△v=-3和△v=-4振动带序发射光谱强度计算得出N2(C,v)的相对振动布居及其振动温度,进而采用高斯分布拟合准确地求出了N2(C^3Ⅱu→B^3Ⅱg)的△v= 1振动带序发射光谱强度,从而可以由N2(C^3Ⅱu→B^3Ⅱg)的△v= 1振动带序与OH(A^2∑→X^2Ⅱ0—0)的重叠发射光谱中准确求出OH(A^2∑→X^2Ⅱ0—0)自由基的发射光谱强度。由发射光谱强度得到了激发态OH(A^3∑)自由基和O(3p^5P),Ha(3P)活性原子的布居。还研究了激发态OH(A^2∑)自由基和O(3p^5P),Ha(3P)活性原子的布居随放电电压和放电频率的变化以及氧气对激发态OH(A^2∑)自由基和O(3p^5P),Ha(3P)活性原子布居的影响。     

金属-糖胺配合物的合成,光谱表征及催化酯类水解的动力学研究

合成了4种新的糖胺 金属配合物,分别为[Ni(HL) (H2 O) 2 ]2 Cl2 ·CH3OH·2H2 O ,[Cu(HL) ]2 Cl2 ·CH3CH2 OH·3H2 O ,[Zn(HL) ]2 Cl2 ·H2 O ,[Co(HL) (H2 O) (OH) ]2 Cl2 ·CH3OH·2H2 O (HLN ,N′ 二βD 葡萄糖基乙二胺) ,并用元素分析、红外、紫外、核磁共振氢谱对其结构进行了表征。结果表明,Ni(Ⅱ) ,Co(Ⅲ)配合物为八面体构型,而Cu(Ⅱ) ,Zn(Ⅱ)配合物为四面体构型。最后研究了其对对硝基苯吡啶甲酸酯(PNPP)催化水解的催化速率常数。     

原子分子在Ni(100)表面吸附的第一性原理研究

本文采用密度泛函理论,结合周期性平板模型,通过对原子H、N、O、S和C,分子CO、N2、NH3、NO,以及自由基CH3、CH、CH2、OH在Ni(100)表面吸附的研究,比较了它们的吸附能,稳定吸附位点,吸附结构及扩散能垒等信息. 这些吸附质与表面结合能力从小到大依次是N2相似文献   

Temperature controlled synthesis of SrCO3 nanorods via a facile solid-state decomposition rout starting from a novel inorganic precursor

Strontium carbonate nanorods have been successfully synthesized via solid-state decomposition of a new precursor, [Sr(Pht)(H₂O)₂]. The obtained nanorods were found to be orthorhombic with the length of 70-100 nm and the diameter of about 10-15 nm. The Effect of calcinations temperature on morphology and purity of the products has been investigated. Strontium carbonate nanorods were formed at 500 °C. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy. In addition, further evidence for the purity and stoichiometry of the product was obtained by XPS (X-ray photoelectron spectroscopy) spectrum.     

低介电常数非晶氟碳薄膜光谱表征

以C4F8和CH4为原料气,通过等离子体增强化学气相淀积的方法制备了非晶氟碳薄膜,在实验条件下所得薄膜的介电常数为2.3。薄膜的傅里叶变换红外光谱表明该薄膜中除了含有CFn(n=1-3）基团外,还含有少量的C=O,C=C等不饱和双键,没有迹象表明C-H和O-H的存在。X射线光电子能谱进一步证明了薄膜中的碳元素有六种不同的化学状态分别为CF3（8%）、CF2（19%）,CF（26.7%)、C↓-—CF。（42.5%),C↓-—C(3.3%)和C=O（0.5%),表明薄膜中大约54%的碳原子与氟成键,大约43%的碳原子不是与氟成键,而是与碳氟基团CFn中的碳原子成键,毗连的两个碳原子上均没有氟参与成键的几率很小。     

Synthesis and characterization of CdS nanoparticles in the presence of oleic acid as solvent and stabilizer

Oleic acid (OA)-capped CdS nanoparticles (NPs) have been successfully synthesized via the direct reaction of Cd(CH₂COO)₂·2H₂O with S powder in OA solvent at 230 °C under nitrogen flow, which was a kind of clean and air-stable solvent. The morphologies and structures of the as-synthesized CdS NPs are examined by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffractometer (XRD), and Fourier transform infrared (FTIR) spectroscopy, and the typical Ostwald ripening growth mechanism is concluded. Moreover, the collected ultraviolet–visible (UV–vis) absorption spectroscopy and photoluminescence (PL) spectroscopy demonstrate good optical properties of CdS NPs.     

原子分子在Ni(100)表面吸附的第一性原理研究

本文采用密度泛函理论,结合周期性平板模型,通过对原子H、N、O、S和C,分子CO、N2、NH3、NO,以及自由基CH3、CH、CH2、OH在Ni(100)表面吸附的研究,比较了它们的吸附能,稳定吸附位点,吸附结构及扩散能垒等信息.这些吸附质与表面结合能力从小到大依次是N2NH3COCH3NOHOHCH2CNSONCHC.在所有的原子中,O原子倾向于吸附在桥位,而其余的原子则倾向于吸附在空位.除N2之外的分子吸附物(CO、NO、NH3),最佳吸附位点均为四重空位,而N2的最稳定吸附位置为顶位.对于自由基吸附物(CH、CH2、CN、OH)而言,它们倾向于吸附在四重空位,而CH3则稳定吸附在桥位.     

N-取代酰胺-二苯酮体系光化夺氢反应活泼自由基的ESR研究

本文用自由基捕捉剂2,3,5,6-四甲基亚硝基苯(ND)及苯亚甲基叔丁基氮氧化物(PBN)与ESR相结合的方法研究了十二种取代酰胺RC₆H₄NHC(0)CH₃(R-CH₃、Cl、Br、H、NO₂)、C₆H₅N(R)C(0)CH₃(R=CH₃、C₂H₅)及HC(0)NR₂(R-CH₃、C₂H₅)与二苯酮光化夺氢反应中的活泼自由基。结果表明: 1.对于RC₆H₄NHC(0)CH₃,二苯酮夺取氮上H形成R-C₆H₄NC(0)CH₃自由基。 2.对C₆H₅N(R)C(0)CH₃及HC(O)NR₂,二苯酮夺取与羰基相连的甲基氢、羰基上氢及与N相连碳上的氢分别形成 C₆H₅N(R)C(0)CH₂、C(0)NR₂、C₆H₅N(CHR')C(0)CH₃及。