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1.
The linear dichroic absorption spectrum of 1,3,6,8-trans-15, 16-hexamethyl-dihydropyrene has been measured in stretched polyethylene at 77K, and CNDO-CI calculations with inclusion of singly and doubly excited configurations have been carried out on a series of alkyl bridged [14] annulenes with pyrene- and anthracene-shaped perimeters. Transitions to e3g → e4u type 1B states are well described, and the results indicate that additional low-energy excited states originate from e3g→ e5g and e2u → e4u type configurations interacting strongly with doubly excited configurations of the e3g, e3g → e4u, e4u type. The second excited singlet state responsible for the weak transition observed between the 1L bands may be assigned to one of these additional states, but it is probably of complex nature, similar to the ‘phantom’ state in linear polyenes. 相似文献
2.
Rolf Gleiter Jens Spanget-Larsen Erik W. Thulstrup Ichiro Murata Kazuhiro Nakasuji Christian Jutz 《Helvetica chimica acta》1976,59(5):1459-1468
The photoelectron (PE.) spectra of azuleno[l, 2, 3-cd]phenalene ( 1 ) and azuleno- [5,6,7-cd]phenalene( 2 ) have been recorded. The first five bands of both compounds could be assigned to transitions corresponding to removal of electrons from 4a2, 6b1, 5b1, 3a2 and 4bl orbitals. This assignment is based mainly on a comparison between the observed ionization potentials and orbital energies calculated in a HMO and a PPP model. The UV./VIS. polarized absorption spectrum of 1 in the region 10000–45000 cm?1 has been measured by means of the stretched film technique. The measurements were performed in polyethylene sheets at 77°K. Several bands could be assigned to π* ← π transitions calculated by a PPP-CI method. A comparison between the electronic structures of 1 and 2 is made by means of a simple HMO diagram. 相似文献
3.
Crystals of bicyclo [2.2.2] octane-1, 4-dicarboxylic acid are monoclinic, a = 6.01 Å, b = 16.73 Å, c = 10.29 Å, β = 115.08°, space group P21/c, with 4 molecules in the unit cell. The structure was solved with the help of direct methods and refined by full-matrix least-squares analysis of the three-dimensional intensity data. Within experimental error the bicyclo [2.2.2]-octane (BCO) skeleton has apparent D3h-symmetry, corresponding to the totally eclipsed conformation. Analysis of the thermal ellipsoids in terms of the translational and rotational motion of the BCO skeleton leads to an r.m.s. amplitude of 5.9 ± 0.2° for rotation about the threefold axis. On the assumption that the bond lengths remain effectively constant during a torsional vibration of BCO, the potential energy surface has been calculated for a range of semi-empirical potential functions. These calculations show that the energy minimum may be slightly displaced from D3h symmetry, but if so the barrier between the two such equivalent minima is only about 0.1 kcal mole?1. The energy eigenvalues and eigenfunctions for a typical variation of potential energy vs torsion angle have been calculated. From the form of the eigenfunction of the ground vibrational state we conclude that BCO has effective D3h symmetry at all temperatures as far as diffraction methods are concerned. 相似文献
4.
The previously unknown polycyclic heterocyclic ring systems, namely, [1]benzothieno[2,3-c]naphtho[1,2-h]-quinoline and [1]benzothieno[2,3-c]naphtho[1,2-h][1,2,4]triazolo[4,3-a]quinoline were synthesized via photocyclization of 3-chloro-N-(1′-phenanthryl)benzo[b]thiophene-2-carboxamide. 相似文献
5.
The crystal structures of [4.4.4]propellane (monoclinic, a=12.053, b=7.832, c=13.001 Å, β=104.89°, space group C2/c, Z=4) and [4.4.4]propellatriene (monoclinic, a=7.876, b=12.651, c=13.164 Å, β=122.81°, space group P21/c,Z=4) have been determined by X-ray analysis. In propellane the six-membered rings are in the chair conformation, in propellatriene they adopt the ‘half-chair’ conformation with a twofold axis passing through the centre of each double bond. In both cases the observed parameters correspond to virtual D3(32) molecular symmetry. Corrections have been applied for the effect of molecular libration. Strain-minimization calculations based on semi-empirical potential functions have been carried out and the molecular parameters so derived are compared with the experimental values. 相似文献
6.
Single crystals of dihydrodibenzo[b, i]-1, 4, 8, 11-tetraazacyclotetradecinenickel iodide show metallic conductivity between room temperature and approx. 110 K. The crystals are orthorhombic, space group Ibam with four formula units per cell of the following dimensions: a = 20.245, b = 13.416, c = 6.418 Å. The analogous palladium complex is isomorphous, the cell constants being a = 20.452, b = 13.430 and c = 6.499 Å. A number of other partially oxidized metal tetraaza [14]annulenes also show electrical conductivity. 相似文献
7.
Yusuke Matsuo Dr. Takayuki Tanaka Prof. Dr. Atsuhiro Osuka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(36):8144-8152
N,N’-Diarylated tetrabenzotetraaza[8]circulenes 3 a and 3 b were synthesized in good yields by a reaction sequence involving oxidation of tetrabenzodiazadithia[8]circulene 5-Oct and SNAr reaction with aniline derivatives. The obtained aza[8]circulenes 3 a and 3 b were easily oxidized to give their radical cations 3 a+ and 3 b+ , which are highly stable under ambient conditions. X-ray diffraction analysis of radical cation 3 a+ showed a face-to-face dimer arrangement with an interplanar separation of 3.320 Å. The spin density of 3 a+ was calculated to be delocalized over the whole circulene π-systems with spin–spin exchange integral (J=−144 cm−1) in the dimeric part. These radical cations displayed far red-shifted absorption bands reaching to 2000 nm. Thus this study has proved the hetero[8]circulene scaffold to be a new entry of promising electronics and spin materials. 相似文献
8.
Ab initio molecular orbital theory using basis sets up to 6-311G* *, with electron correlation incorporated via configuration interaction calculations with single and double substitutions, has been used to study the structures and energies of the C3H2 monocation and dication. In agreement with recent experimental observations, we find evidence for stable cyclic and linear isomers of [C3H2]+ ˙. The cyclic structure (, a) represents the global minimum on the [C3H2]+ ˙ potential energy surface. The linear isomer (, b) lies somewhat higher in energy, 53 kJ mol?1 above a. The calculated heat of formation for [HCCCH]+ ˙ (1369 kJ mol?1) is in good agreement with a recent experimental value (1377 kJ mol?1). For the [C3H2]2+ dication, the lowest energy isomer corresponds to the linear [HCCCH]2+ singlet (h). Other singlet and triplet isomers are found not to be competitive in energy. The [HCCCH]2+ dication (h) is calculated to be thermodynamically stable with respect to deprotonation and with respect to C? C cleavage into CCH+ + CH+. The predicted stability is consistent with the frequent observation of [C3H2]2+ in mass spectrometric experiments. Comparison of our calculated ionization energies for the process [C3H2]+ ˙ → [C3H2]2+ with the Qmin values derived from charge-stripping experiments suggests that the ionization is accompanied by a significant change in structure. 相似文献
9.
Treatment of 1,2,3-trichloropentamethyltrisilane (1) with H2S/NEt3 results in the formation of a mixture of two isomers of (Me5Si3)2S3 with a bicyclo[3.3.1]nonane (2a) and a bicyclo[3.2.2]nonane (2b) skeleton, while the reaction of 1 with Li2Se yields one product only, (Me5Si3)2Se3 (3a), with a bicyclo[3.3.1]nonane structure. Besides 1H, 13C, 29Si and 77Se NMR spectroscopy 3a has also been characterized by a crystal structure analysis.Compounds Si(SiMe2EMR2E)2 (5a-h: MR2: SiMe2 (5a, c, d), SiPh2 (5b), GeMe2 (5e, f), SnMe2 (5g, h); E=S (5a, b, e, g), Se (5c, f, h), Te (5d)) with a spiro[4.4]nonane skeleton have been obtained in mixture with varying amounts of the corresponding six-membered rings (R2ME)3 by reactions of mixtures of 1,2,2,3-tetrachlorotetramethyltrisilane (4) and diorganodichlorosilanes, Me2GeCl2 or Me2SnCl2, with H2S/NEt3, Li2Se or Li2Te and have been characterized in situ by multinuclear NMR spectroscopy (1H, 13C, 29Si, 119Sn, 77Se, 125Te) and GC-MS. 相似文献
10.
Hari K. Gakhar Sushma Kiran Sashi Bhushan Gupta 《Monatshefte für Chemie / Chemical Monthly》1982,113(10):1145-1150
4H,6H-[1,3,4]Thiadiazino[2,3-b]quinazolin-6-one with a methyl group in position 3 (6a) has been synthesised by the condensation of 3-amino-2-mercapto-3H-quinazolin-4-one (1) with allyl bromide (2) followed by treatment with bromine and subsequent dehydrohalogenation of the brominated product (4) with ethanolic sodium hydroxide. Its isomeric 3-methyl-2H,6H-[1,3,4]thiadiazino[2,3-b]quinazolin-6-one (6b) has also been obtained by condensation of1 and bromoacetone (7) followed by cyclisation of the intermediates (8 or9) with hydrobromic acid or with concentrated sulphuric acid. The structures have been established on the basis of IR and PMR data.
3-Methyl[1,3,4]thiadiazino[2,3-b]chinazolin-6-one
Zusammenfassung Zur Synthese von 4H,6H-[1,3,4]thiadiazino[2,3-b]chinazolin-6-on (6a) wurde die Kondensation von 3-Amino-2-mercapto-3H-chinazolin-4-on (1) mit Allylbromid mit nachfolgender Behandlung mit Brom und Dehydrohalogenierung des bromierten Produktes4 mit ethanolischer Natronlauge herangezogen. Das zu6a isomere 2H,6H-Produkt6b wurde ebenfalls durch Kondensation von1 mit Bromaceton und nachfolgender Cyclisierung der Zwischenprodukte8 bzw.9 mit HBr oder H2SO4 erhalten. Die Strukturen wurden mittels IR und NMR abgesichert.相似文献
11.
Hans-Herbert Schmidtke 《Theoretical chemistry accounts》1971,20(2):92-104
Zusammenfassung Eine kurze Ableitung des Angular Overlap-Modells wird gegeben. Das Modell wird auf zweikernige Übergangsmetallkomplexe vom Typ L5M-O-ML5 angewandt. Die Parametrisierung vond-Orbitalwechselwirkungen liefert fürD
4h-Symmetrie die Orbitalreihenfolgee
g<b
2g=b
1u<e
u
*
<a
1g
*
<b
1g=b
2u<a
2u
*
. Aus dem Orbitalschema lassen sich die magnetischen (intramolekularer Antiferromagnetismus) und die optischen Eigenschaften (Elektronenspektren) erklären, die sich von den gewinkelten Molekülen wesentlich unterscheiden. Der im linearen Cr-Komplex neu auftretende Bandentyp wird einem Übergang einesd-Elektrons in ein Molekülorbital zugeordnet, das über die Cr-O-Cr-Bindungsregion delokalisiert ist.
Dem Andenken von Herrn Professor Hans-Ludwig Schläfer gewidmet.
Herrn Prof. Dr. Hans-Ludwig Schläfer, der das Thema dieser Arbeit anregte, danke ich an dieser Stelle nochmals herzlich für viele wertvolle Diskussionen. Der Deutschen Forschungsgemeinschaft, Bad Godesberg, sei für die Bereitstellung finanzieller Mittel gedankt. 相似文献
Angular overlap treatment of low symmetry complexesII. Binuclear complexes with a linear oxygen bridge
A short derivation of the Angular Overlap model is presented. It is applied on binuclear transition metal complexes of the type L5M-O-ML5. A parametrization ofd-orbital interactions forD 4h symmetry yields the energy ordere g<b 2g=b 1u<e u * <a 1g * <b 1g=b 2u<a 2u * . From the orbital scheme the magnetic (intra molecular antiferromagnetism) and optical properties (electron spectra) are explained, which are different from corresponding molecules with angled structure. The new type of bands found in the spectrum of the linear Cr complex is assigned to a transition of ad electron into a molecular orbital which is delocalized over the Cr-O-Cr bond moiety.
Résumé Une brève représentation du modèle Angular Overlap est donnée. Le modèle est appliqué aux composés binucléaires de groupes de transition du type L5M-O-ML5. La parametrization des interactions des orbitalesd pour la symétrieD 4h donne les énergies d'orbitalese g<b 2g=b 1u<e u * <a 1g * <b 1g=b 2u<a 2u * . Cette série peux expliquer les propriétés magnétiques (antiferromagnétisme intramoléculaire) et optiques, qui sont différent de molécules avec structure angulaire. Le nouveau type des bandes trouvé dans le spectre du complex linéaire Cr est assigné à la transition d'un électrond dans une orbitale moléculaire qui est délocalisée sur la région de liaison Cr-O-Cr.
Dem Andenken von Herrn Professor Hans-Ludwig Schläfer gewidmet.
Herrn Prof. Dr. Hans-Ludwig Schläfer, der das Thema dieser Arbeit anregte, danke ich an dieser Stelle nochmals herzlich für viele wertvolle Diskussionen. Der Deutschen Forschungsgemeinschaft, Bad Godesberg, sei für die Bereitstellung finanzieller Mittel gedankt. 相似文献
12.
The vertical valence ionization potentials of trans-N2F2 and cis-N2F2 have been computed by a many-body Green function method. For trans-N2F2 the agreement with experiment is very satisfactory in general and the calculations permit an analysis and assignment of the experimental photoelectron spectrum. The ionization potentials of cis-N2F2 are predictions. The ordering of the ionization potential is for trans-N2F2 5ag(n+), 2au(π), 4bu(n?), 4ag, 1bg(π), 1au(π), 3bu, 3ag, 2bu and for cis-N2F2 4b2 (n?), 2b1 (π) + 5a1(n+), 3b2, 1a2 (π), 1b1(π), 4a1, 3a1, 2b2, n+ and n? denote lone pairs on the N atoms except for the 4bu(n?) orbital which has the largest contribution from the F atoms. 相似文献
13.
Kisun'ko D. A. Zabalov M. V. Myshakin E. M. Oprunenko Yu. F. Lemenovskii D. A. 《Russian Journal of General Chemistry》2001,71(11):1751-1753
The regioselectivity in reactions of the lithium salt of 4H-cyclopenta[2,1-b:3,4-b']dithiophene with various electrophilic agents [SiMe3Cl, SnMe3Cl, D2O, Re(CO)5Br] is discussed in terms of the charge and orbital control concepts. 相似文献
14.
A New Conformation With an Extraordinarily Long, 3.04 Å Two‐Electron,Six‐Center Bond Observed for the π‐[TCNE]22− Dimer in [NMe4]2[TCNE]2 (TCNE=Tetracyanoethylene)
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Adora G. Graham Dr. Fernando Mota Dr. Endrit Shurdha Prof. Arnold L. Rheingold Prof. Juan J. Novoa Prof. Joel S. Miller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(38):13240-13245
[NMe4]2[TCNE]2 (TCNE=tetracyanoethenide) formed from the reaction of TCNE and (NMe4)CN in MeCN has νCN IR absorptions at 2195, 2191, 2172, and 2156 cm?1 and a νCC absorption at 1383 cm?1 that are characteristic of reduced TCNE. The TCNEs have an average central C?C distance of 1.423 Å that is also characteristic of reduced TCNE. The reduced TCNE forms a previously unknown non‐eclipsed, centrosymmetric π‐[TCNE]22? dimer with nominal C2 symmetry, 12 sub van der Waals interatomic contacts <3.3 Å, a central intradimer separation of 3.039(3) Å, and comparable intradimer C???N distances of 3.050(3) and 2.984(3) Å. The two pairs of central C???C atoms form a ?C?C???C?C of 112.6° that is substantially greater than the 0° observed for the eclipsed D2h π‐[TCNE]22? dimer possessing a two‐electron, four‐center (2e?/4c) bond with two C???C components from a molecular orbital (MO) analysis. A MO study combining CAS(2,2)/MRMP2/cc‐pVTZ and atoms‐in‐molecules (AIM) calculations indicates that the non‐eclipsed, C2 π‐[TCNE]22? dimer exhibits a new type of a long, intradimer bond involving one strong C???C and two weak C???N components, that is, a 2e?/6c bond. The C2 π‐[TCNE]22? conformer has a singlet, diamagnetic ground state with a thermally populated triplet excited state with J/kB=1000 K (700 cm?1; 86.8 meV; 2.00 kcal mol?1; H=?2 JSa?Sb); at the CAS(2,2)/MBMP2 level the triplet is computed to be 9.0 kcal mol?1 higher in energy than the closed‐shell singlet ground state. The results from CAS(2,2)/NEVPT2/cc‐pVTZ calculations indicate that the C2 and D2h conformers have two different local metastable minima with the C2 conformer being 1.3 kcal mol?1 less stable. The different natures of the C2 and D2h conformers are also noted from the results of valence bond (VB) qualitative diagram that shows a 10e?/6c bond with one C???C and two C???N bonding components for the C2 conformer as compared to the 6e?/4c bond for the D2h conformer with two C???C bonding components. 相似文献
15.
The sequential reaction of selected polycyclic aromatic hydrocarbons with butyllithium/TMEDA/hexane and sulfur allows preparation of ring-fused dithiins, dithioles, and thiophenes. In this manner, phenanthrene has been converted to phenanthro[4,5-cde][1,2]dithiin and phenanthro[1,10cd]-1,2-dithiole. Yellow crystals of the dithiin form in C2/c (#15) space group with Z = 4, a = 13.537(3) Å, b = 8.933(2) Å, c = 9.601(4) Å, and β = 116.19 (2)°; while orange crystals of the dithiole form in P212121 (#19) space group with Z = 4, a = 4.1507(5) Å, b = 14.436(3) Å, and c = 16.972(3) Å. Full structures have been determined for both compounds. 相似文献
16.
Mehmet Somer Mehmet Nuri Kütükcü Raul Cardoso Gil Horst Borrmann Wilder Carrillo‐Cabrera 《无机化学与普通化学杂志》2004,630(7):1015-1021
The title compounds have been synthesized at 1473 K from stoichiometric mixtures of the binary components Mg3N2, MgX2 (X = Cl, I) and BN in arc‐welded steel ampoules encapsulated in evacuated silica tubes. Mg2[BN2]Cl ( 1 ) and Mg8[BN2]5I ( 2 ) crystallize in the orthorhombic space groups Pbca (no. 61) and Imma (no. 74), respectively, with a = 6.6139(8)Å, b = 9.766(1)Å, c = 10.600(1)Å, Z = 8 for 1 and a = 13.535(3)Å, b = 9.350(2)Å, c = 11.194(2)Å, Z = 4 for 2 . The crystal structures are characterized mainly by Mg6 trigonal prisms which are condensed to 3D frameworks in different ways. Part of the trigonal prisms are centered by the [N—B—N]3— anions and other voids in the framework by the X— anions. The magnesium environment around Cl— is a very distorted monocapped trigonal prism (CN = 6+1) and that of I— is a bicapped heptagonal prism (CN = 14+2). The bond lengths and bond angles for the relevant [BN2]3— anions are d(B—N) = 1.330 — 1.338Å, ∠N—B—N = 175.8° in 1 and d(B—N) = 1.330 — 1.339Å, ∠N—B—N = 176.8° — 178.0° in 2 . The vibrational spectra of the title compounds have been recorded and interpreted based on the D∞h symmetry of the relevant [N—B—N]3— groups considering the site symmetry splitting. 相似文献
17.
Scrambling data for the three observed [C2H3O]+ isomers, namely [CH3CO]+ (a), [CH2COH]+ (b) and (c), are rationalized by using ab initio molecular orbital calculations. For ions a and c, processes leading to scrambling of the carbon atoms require substantially more energy than the threshold for decomposition to [CH3]+ + CO. Accordingly, little or no carbon scrambling is predicted nor is any observed in the metastable dissociation of a and c. The observed carbon scrambling in b prior to metastable dissociation to [CH3]+ + CO has previously been explained in terms of a mechanism involving the oxiranyl cation (c). However, this mechanism is shown to be unlikely because of the high energies involved. An alternative lower-energy pathway involving the intermediacy of protonated oxirene (h) is proposed. Such a mechanism is fully compatible with the experimental data. 相似文献
18.
Constantin A. Kavounis 《Structural chemistry》1997,8(4):287-292
The title compound was synthesized by the reaction of cyclooctane-1,5-dione and N-methyl-phenylenediamine in ethanol solution and an X-ray analysis has been carried out. The crystals belong to the monoclinic space groupC2/c, witha=20.032(4) å,b=7.936(1) å,c=17.316(2) å,b=109.73(2),V=2591.2(7) å,Z=8, and Dcalc=1.253 M g–3. The final discrepancy factor isR=0.039 for 866 observed reflections. The analysis showed the synchronous formation of a heterobicyclo[3.3.1]nonane skeleton, and the five-membered ring of the benzoimidazoline presents an envelope conformation flapping at C1. 相似文献
19.
[BuN(CH2CH2)3NBu]3[Pb5I16] · 4 DMF – an Iodoplumbate Anion with approximately D 5h Symmetry The star‐shaped anion of [BuN(CH2CH2)3NBu]3‐[Pb5I16] · 4 DMF ( 1 ) consists of a cyclic arrangement of five PbI6 octahedra sharing one common I atom in the centre of an almost planar Pb5 ring. Compound 1 crystallizes in space group P21 with a = 1657.2(1), b = 2029.2(1), c = 1773.6(1) pm, β = 113.238(8)°, Z = 2. 相似文献
20.
The magnetic circular dichroism (MCD) and absorption spectra of the mononegative and dinegative ions of [16] annulene have been measured in the 16000–30000 cm?1 region. The results are interpreted using a PPP molecular orbital calculation. It is found that the D4h symmetry, using Slater type atomic orbitals excellent agreement between experiment and calculations is obtained. The excited 2Eg and 1Eu states of the mono- and dinegative ions have experimental averaged angular monomenta of 1.0 h and 2.3 h respectively and we conclude to planar ring structures for the ions. Variations in the parameters for the PPP calculations, i.e. B, do not influence the MCD values to any great extent.In addition, from temperature dependent measurements between 20°C and ?150°C, the thermodynamic parameters ΔH and ΔS for the equilibrium observed between molecule and ions in solution have been determined. 相似文献