苯氰基衍生物气相HeI紫外光电子能谱研究

气相Hel（21．22eV）紫外光电子能谱（UPS）能从孤立分子的分子轨道特性上，给出研究分子的轨道能量、电子结构以及成键特性的大量信息．UPS谱的特性揭示了被电离分子轨道的成键性质，而量子化学计算能正确地指认UPS谱带的归属，从而化合物的UPS研究从分子轨道的属性上提供了研究体系的实验和理论基础．苯基腈（C6H5CN）的UPS已有过研究［1-3］，但作为系列分子的间-二氰基苯（1）、对-二氰基苯（2）、1；2，4，5-四氰基苯（3）的HeI光电子能谱未见报道．这一系列分子的特点是-CN取代的数目和位置不同，通过这些分子UPS的研究找…     

B(OCH3)3电子结构的Hel紫外光电子能谱研究

人们知道，Hel紫外光电子能借（PES）提供研究分子轨道能量、能级次序、成键类型以及由光电子峰强度所反映的电离轨道特性等信息是其他手段没有的，因而PES技术已广泛地用于众多化合物分子电子结构的研究中．有机础化合物由于它们高的反应活性作为合成试剂而信受人们重视［‘－     

3-硝基-1,2,4-三唑-5-酮的锰钴和镍配合物的分子轨道研究

用EHMO方法计算研究3－硝基－1，2，4－三唑－5－酮（NTO）的锰、钴和镍配合物［M（H2O）6］（NTO）2·2H2O（M＝Mn、Co和Ni）的电子结构，通过比较原子上净电荷、原子间重叠布居、前沿分子轨道能级和组成等电子结构参数，阐明了标题物的配位键特征和热解实验．     

Lien元素簇合物的成键作用

镇元素簇合物是人们最感兴趣的簇合物之一l‘－’］．已有的。作主要是研究它的稳定性和电子结构，对其成键性质还研究得不多·为止匕我们对Lkin为元素簇合物中所含原子个数，e为该化合物的电荷）进行了定域化研究，并得出一些有意义的结果·1计算我4rl采用GAMESS90程序m，在4－31G基组下进行了正则分子轨道SCFi十算（闭壳层采用RHF，开壳层采用UHF）．然后，以QSU90程序问，用B0yS方法进行了定域化计算，得到定域分子轨道（LM），再根据LMO的系数和集居数分析，判断各分子中原子的成键情况问．共计算了18个簇合物．它们的原子数…     

噻吩多烯基噻吩酮系列化合物的气相紫外光电子能谱研究

本文提供了噻吩多烯基噻吩酮系列化合物的气相HeI光电子能谱(UPS), 并进行了每个研究分子的MNDO量子化学计算。 表明乙烯基基团的数目与其分子的HOMO实验电离能(L~p)呈线性递降关系。MNDO计算结果不但很好地指认了每个研究分子UPS谱的归属, 而且从分子轨道特性上提供了该类化合物分子为三岔共轭体系的理论基础。     

几种硫醚化合物的紫外光电子能谱及量子化学研究

报导了硫酸系列化合物DMS（二甲基硫酸），DpCPS（二对氯苯硫酸），DpTS（二对甲基苯硫醚）气相HcI紫外光电子能谱（UPs），其中DpCPS，DpTS的UPS谱为首次获得．对各体系利用MNDO方法进行了分子构型优化，对优化得到的优势构型实施RHF／6－31G量子化学计算，并利用计算结果对各个分子体系的UPS谱进行了指认，计算结果分析显示：a）S原子的孤对电厂在DpCPS和DpTS中起到阻碍形成遍及整个分子体系π轨道的阻断作用，故此不存在遍及整个分子体系的π轨道；b）通过对三体系第一电高能的对比分析表明，第一电高能所激发出的电子主要是受S原子的束缚；c）还得到另一个有意义的结论──各分子体系的第一电离能大小与HOMO中3Pz轨道所占成份成有很好的线性关系．表明体系的第一电离出的电子主要是受S原子的3Pz轨道束缚     

氯化稀土冠醚配合物的电子结构和化学键

合成了LnCl_3·L(Ln=La、Pr、Nd和Sm。L=15-C-5、18-C-6)系列配合物,用XPS和量子化学计算研究了它们的分子构型、电子结构和化学键性质。计算与实验结果一致。在LnCl_3·15-C-5中三个Cl在Ln的一侧,形成8配位配合物。LnCl_3·15-C-5在空气中容易潮解。高层占据分子轨道由Cl 3P和O2P-组成,低层未占据分子轨道由Ln的原子轨道组成。     

同位素氧-18分子的HeⅠ紫外光电子能谱

气体分子的HeI紫外光电子能谱（UPS）可提供分子不同能级的振动结构、能量以及成健类型上的大量信息．其中在探讨稳态分子的UPS研究中，人们对氧分子的研究已十分详尽门，但尚未计及同位素氧-18分子的UPS报导．涉及同位素分子的UPS研究，迄今为止仅有氛分子及其少数由氛原子组成的个别小分子，如DH，D2O和ND3等[2－4].鉴于同位素氧-18在高能物理、生物、医学以及化学等领域的重要作用，近期我国科学工作者已成功地制得高纯度的氧-18分子．研究它的性质及其与电子结构间的关系是十分紧迫的课题．为儿我们在开展与氧一18分子有关的UP…     

二—(2,2''''—联吡啶)—三—(硝酸)合镧(Ⅲ)La(C_(10)H_8N_2)_2(NO_3)_3的电子结构和化学键

引 言 希土化合物由于涉及f轨道,用分子轨道方法有一定困难,前人曾采用过多种处理方法。文献[8]报导了希土-2,2’-联吡啶配位方法和性质研究。文献[8],[9]对镧与2,2—联吡啶,硝酸配合物的合成,性质和结构亦作过研究。本文采用适用于镧系元素化合物电子结构计算的自旋非限制的INDO方法来研究La(C_(10)H_8N_2)_2(NO_3)_3的电子结构和化学键。     

哌嗪二酮的气相Hel光电子能谱及其量化计算

给出了哌嗪二酮的气相HeI紫外光电子能谱(UPS), 并进行了化合物分子的HAM/3, MNDO, MINDO/3, INDO, CNDO/2和EHMO等量子化学计算研究. UPS谱低电离能(<11.00 eV)区的四重峰被指认为分子体系中氧-氧, 氮-氮原子孤对轨道间的通过键相互作用导致的分裂峰. 表明HAM/3和MNDO计算法是预指该化合物实验电离能正确次序、轨道对称性类型以及通过键相互作用导致分裂大小的较好方法.     

HeI photoelectron spectroscopic (PES) studies of the electronic structure in ω-heterocycle a-cyano polyenic ethyl ester compounds

HeI photoelectron spectra of w-heterocycle a-cyano polyenic ethyl ester compounds (1-6) have been given in this paper. Assignment of the spectra is also done with the aid of HeI photoelectron spectroscopic (PES) results of smaller molecules which have similar atomic group to the molecules studied, and the aid of MNDO molecules orbital calculations. The lowest PES experimental ionization potentials (IPs in eV) of different molecules reduce gradually with the increasing number of ethylenic group. The -CO2C2H5 group can be only considered as a substituent.     

HeI photoelectron spectroscopic (PES) studies of the electronic structure in ω-heterocycle α-cyano polyenic ethyl ester Compounds

Hel photoelectron spectra of ω-heterocycle α-cyano polyenic ethyl ester compounds (1–6) have been given in this paper. Assignment of the spectra is also done with the aid of HeI photoelectron spectroscopic (PES) results of smaller molecules which have similar atomic group to the molecules studied, and the aid of MNDO molecules orbital calculations. The lowest PES experimental ionization potentials (IPs in eV) of different molecules reduce gradually with the increasing number of ethylenic group. The -CO₂C₂H₅ group can be only considered as a substituent.     

Probing weak molecular orbital interactions in non-conjugated diene molecules by means of near-edge X-ray absorption spectroscopy

Carbon and oxygen near-edge X-ray absorption fine structure (NEXAFS) spectra of 1,4-cyclohexadiene, p-benzoquinone, norbornadiene, norbornadienone, and cis-cis-[4,4,2]propella-3,8-diene-11,12-dione were calculated by means of Hartree-Fock and hybrid density functional theory using the static-exchange (STEX) approximation. The NEXAFS spectra are used as a probe to identify weak molecular interactions between the two non-conjugated ethylenic pi* orbitals present in these molecules. We show that the X-ray absorption spectrum of 1,4-cyclohexadiene exhibits some particular spectral structures in the discrete energy region that evidence diene through-bond orbital interaction, whereas absorption peaks are identified in the norbornadiene and norbornadienone spectra that indicate effective through-space orbital interactions. The molecular structure of the cis-cis-[4,4,2]propella-3,8-diene-11,12-dione isomer is such that the indirect through-bond or through-space diene orbital interactions are too weak to be assigned by its C1s NEXAFS spectrum.     

Etude des fragmentations en spectrographie de masse de dithiannes-1,3 substitués en 2 par des groupements insaturés

The mass spectra of the title compounds always show an intense molecular ion. Some fissions involve loss of the ethylenic group, while others are related to cleavage of the dithiane ring, eventually followed by recyclizations involving the ethylenic chain stabilized by the resonance possibilities. If a phenyl group is present in the ethylenic chain, the spectra are modified by the formation of the very stable benzothiopyrylium ion.     

Etude des fragmentations en spectrographie de masse de dithiolannes-1,3 substitués en 2 par des groupements insaturés

The mass spectra of the title compounds always show an intense molecular ion. Some fissions involve loss of the ethylenic group, while others are related to cleavage of the dithiolane ring, eventually followed by recyclizations involving the ethylenic chain, due to which resonance structures can be written. If a phenyl group is present in the ethylenic chain, the spectra are modified due to the formation of the very stable benzothiopyrylium ion.     

Resonance Raman Structural Evidence that the Cis-to-Trans Isomerization in Rhodopsin Occurs in Femtoseconds

Picosecond time-resolved resonance Raman spectroscopy is used to probe the structural changes of rhodopsin's retinal chromophore as the cis-to-trans isomerization reaction occurs that initiates vision. Room-temperature resonance Raman spectra of rhodopsin's photoproduct with time delays from -0.7 to 20.8 ps are measured using 2.2 ps, 480 nm pump and 1.5 ps, 600 nm probe pulses. Hydrogen-out-of-plane (HOOP) modes at 852, 871, and 919 cm(-1), fingerprint peaks at 1272, 1236, 1211, and 1166 cm(-1), and a broad red-shifted ethylenic band at 1530 cm(-1) are present at the earliest positive pump-probe time delay of 0.8 ps, indicating that the chromophore is already in a strained, all-trans configuration. Kinetic analyses of both the HOOP and ethylenic regions of the photoproduct spectra reveal that these features grow in with fast ( approximately 200 fs) and slow ( approximately 2-3 ps) components. These data provide the first structural evidence that photorhodopsin has a thermally unrelaxed, torsionally strained all-trans chromophore within approximately 1 ps, and possibly within 200 fs, of photon absorption. Following this ultrafast product formation, the all-trans chromophore cools and conformationally relaxes within a few picoseconds to form bathorhodopsin. This cooling process is revealed as an ethylenic frequency blue-shift of 6 cm(-1) (tau approximately 3.5 ps) as well as an ethylenic width narrowing (tau approximately 2 ps). The ultrafast production of photorhodopsin is likely accompanied by an impulsively driven, localized protein response. More delocalized protein modes are unable to relax on this ultrafast time scale enabling the chromophore-protein complex to store the large amounts of photon energy (30-35 kcal/mol) that are subsequently used to drive activating protein conformational changes.     

Complete 1H and 13C NMR assignment of trans,trans-2,3-divinylfuran derivatives

1H and 13C NMR spectra of trans, trans-2,3-divinylfuran derivatives (1-4) in CDCl3 were fully assigned using one- and two-dimensional NMR techniques. The 1H NMR resonances of ethylenic protons in position 2 with regard to the corresponding protons in position 3 of the furan ring are discussed.     

Cooperativity of hydrogen-bonded networks in 7-azaindole(CH3OH)n (n=2,3) clusters evidenced by IR-UV ion-dip spectroscopy and natural bond orbital analysis

IR-UV ion-dip spectra of the 7-azaindole (7AI)(CH(3)OH)(n) (n=1-3) clusters have been measured in the hydrogen-bonded NH and OH stretching regions to investigate the stable structures of 7AI(CH(3)OH)(n) (n=1-3) in the S(0) state and the cooperativity of the H-bonding interactions in the H-bonded networks. The comparison of the IR-UV ion-dip spectra with IR spectra obtained by quantum chemistry calculations shows that 7AI(CH(3)OH)(n) (n=1-3) have cyclic H-bonded structures, where the NH group and the heteroaromatic N atom of 7AI act as the proton donor and proton acceptor, respectively. The H-bonded OH stretch fundamental of 7AI(CH(3)OH)(2) is remarkably redshifted from the corresponding fundamental of (CH(3)OH)(2) by 286 cm(-1), which is an experimental manifestation of the cooperativity in H-bonding interaction. Similarly, two localized OH fundamentals of 7AI(CH(3)OH)(3) also exhibit large redshifts. The cooperativity of 7AI(CH(3)OH)(n) (n=2,3) is successfully explained by the donor-acceptor electron delocalization interactions between the lone-pair orbital in the proton acceptor and the antibonding orbital in the proton donor in natural bond orbital (NBO) analyses.     

Vibrational spectra of 2 (3H) benzofuranone studied by Raman,IR spectroscopy and AM1 semiempirical molecular orbital calculations

Raman spectra of 2 (3H) benzofuranone have been recorded in the region 400-3200 cm(-1) and the IR spectra have been recorded in the region 200-4000 cm(-1). Vibrational frequencies for the fundamental modes of this bicyclic heteroatomic molecule have also been calculated using Austin method 1 (AM1) semiempirical molecular orbital method. Vibrational assignments have been made for the fundamental modes and the observed combination and overtone bands are also assigned. A splitting in the carbonyl group (C=O stretching) frequency observed at 1640-1660 cm(-1) in both Raman and IR spectra, is explained as Fermi-resonance. Net atomic charges for each atom of this molecule along with its heat of formation were also calculated. It is evident from the calculations that the 2 (3H) benzofuranone is more stable than the 3 (2H) benzofuranone in contrast to earlier estimates.