Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Articles: DFG German National Licenses  (28)
  • Organic Chemistry  (28)
  • 1
    Electronic Resource
    Electronic Resource
    Persistance of the Cyclopnane Radical Anions and its Relation to Structure (1982)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 65 (1982), S. 1391-1397 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of [2N]cyclophanes (N = 2,⃛6) with solvated electrons in 1,2-di-methoxyethane at 193 K have been studied by ESR. and ENDOR. spectroscopy. All but the two most highly bridged cyclophanes (N = 5 and 6) are reduced to paramagnetic species under these conditions. Whereas the radical anions of [2.2]-paracyclophane and [23](1,2,4)- and [24](l,2,4,5)cyclophanes are sufficiently persistent to be characterized by their hyperfine data, those of the remaining five cyclophanes undergo a rapid cyclization to the radical anions of 4,5,9,10-tetrahydropyrenes. These have been identified as the unsubstituted tetrahydropyrene (from [2.2]-metacyclophane and [23](l,2,3)cyclophane), the 2,7-dimethyl-derivative (from [23](1,3,5)- and [24](l,2,3,5)cyclophanes) and the 1,8-dimethyl-derivative (from (24l,2,3,4)cyclophane). The persistence of the cyclophane radical anions seems to depend on the numbers, nmeta and npara, of the meta-and para-positions of the bridging ethano groups in the two benzene rings. The prerequisite for the radical anion to be persistent is nmeta≤npara.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19820650510
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    The Radical Anions of Some Substituted [2.2]Paracyclophanes (1979)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2569-2576 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The radical anions of the following substituted [2.2]paracyclophanes have been characterized by ESR. and ENDOR. spectroscopy: 4, 16-dicyano- (o-2), 4, 12-dicyano- (p-2), 4,5,12,13-tetracyano- (3) and 4,5,12,13-tetrakis (alkoxycarbonyl)- [2.2]paracyclophanes (4-R, where R = Me, Et, iPr or tBu is the ester alkyl group); 4,5-bis(methoxycarbonyl)[2.2]paracyclophane-12, 13-dicarboxylic anhydride (5); [2.2]paracyclophane-4,5:12, 13-tetracarboxylic bisanhydride (6) and bisimides (7-R, where R = H, D, Me or Ph is the substituent at the imide N-atom). Comparison of the hyperfine data for these radical anions with those for analogously substituted derivatives of benzene indicates that the most prominent coupling constants are approximately halved on passing from the latter to the former. Lowering of the symmetry, as a consequence of ion pairing, has been observed for the radical anions 4-iPr\documentclass{article}\pagestyle{empty}\begin{document}$^{\ominus \atop \dot{}}$\end{document} and 4-tBu\documentclass{article}\pagestyle{empty}\begin{document}$^{\ominus \atop \dot{}}$\end{document} associated with the counterion K⊕ in 1,2-dimethoxyethane at 183 K, but not for 4-Me\documentclass{article}\pagestyle{empty}\begin{document}$^{\ominus \atop \dot{}}$\end{document} and 4-Et\documentclass{article}\pagestyle{empty}\begin{document}$^{\ominus \atop \dot{}}$\end{document} under the same conditions. This result suggests that the migration of K⊕ between the preferred sited in two equivalent ion pairs is slowed down by the steric hindrance arising from the bulky iPr and tBu ester groups.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19790620810
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Ionization Energies of Methyl-substituted[2.2]Paracyclophanes (1981)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 1991-2001 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photoelectron (PE.) spectra of thirteen methyl-substituted [2.2]paracyclophanes have been recorded and analyzed, to assess the influence of methyl-substitution on their ionization energies. It is shown that this influence is qualitatively and quantitatively the same as for benzenes and other π-systems. Comparison with the previous results obtained for the [2r]cyclophanes (r=2 to 6) strongly suggests that the hyperconjugative model for alkyl-group/π-system interactions is more appropriate than the inductive one.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19810640704
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    The Radical Cations of 4,5,7,13,15,16-Hexamethyl- and 4,5,7,8,12,13,15,16-Octamethyl [2.2]paracyclophane (1982)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 65 (1982), S. 1398-1403 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 4,5,7,13,15,16-Hexamethyl- (3) and 4,5,7,8,12,13,15,16-octamethyl[2.2]paracyclophane (4) have been oxidized to their radical cations in solution under relatively mild conditions. Substantial hyperfine splittings in the ESR. spectra of 3⊕. and 4⊕. arise from the methyl protons, whereas those from methylene protons are very small. This result indicates that the ethano bridges, unlike the methyl substituents, are rather ineffective in delocalizing the positive charge in 3⊕. and 4⊕. It is in line with the interpretation proposed previously to rationalize the gas-phase ionization potentials of multiply bridged [2N]cyclophanes and methyl derivatives of [2.2]paracyclophane. The π-spin distributions in 3⊕. and 4⊕. are discussed in terms of a simple model in which the singly occupied orbitals are represented as the antibonding combinations of two benzene HOMO's.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19820650511
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Data bank: The PE Spectra of Paracyclophanes with Unsaturated Bridges and of Related Molecules (1987)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 299-307 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The PE spectroscopic data for a series of [2.2]paracyclophanes with olefinic and/or aromatic bridges, and of a few related molecules are reported, together with tentative assignments based on simple MO models.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19870700205
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Solution Structure of One-Electron Reduced and Oxidized Molecules with Twisted Donor and Acceptor Moieties (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1466-1474 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solution structures of the radical anion and the radical cation of the donor-acceptor molecules 3,4-di(1,3-dithiol-2-ylidene)-4-phenylbut-1-ene-1,1-dicarbonitrile (1) and 3,4-di(1,3-dithiol-2-ylidene)-4-phenylbut-1-ene-1,1,2-tricarbonitrile (2) are discussed based on cyclovoltammetric and ESR/ENDOR measurements. It is shown that the spin population of the radical anions is limited to the di- and tricyanoethene moiety and the coplanar 1,3-dithiole at C(3), whereas that of the radical cations resides mainly inside the two 1,3-dithiole rings. The energies of the long-wave bands in the electronic-absorption spectra of 1 and 2 correspond to the differences between the oxidation and reduction potentials and thus point to a charge-transfer character of these transitions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770524
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Planar chiral systems, IV. An efficient route for the preparation of 5-formyl-4-hydroxy[2.2]paracyclophane (FHPC) (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 449-451 
    Details
    ISSN: 0947-3440
    Keywords: Cyclophanes, multifunctionalized ; Auxiliaries, chiral ; Metalation, ortho-directed ; Fries rearrangement ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the preparation of the title compound, 4-hydroxy[2.2]paracyclophane (1) is first converted to the carbamate 2. Metalation of 2 with sec-butyllithium yields an ortho-anion which after trapping with dimethylformamide and acidic work-up provides 6 in 64% yield. Further application of the cyclophane anion include its capture by trimethylsilyl chloride to the trimethylsilyl derivative 3 (76%) and its Fries rearrangement to the phenol 4 (78%). The spectroscopic and analytical data of the new compounds are described in full detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199519950259
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Cyclophanes, XXXIX. The Structure of the Dicyanoacetylene Adducts of [2.2]Paracyclophane (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 609-612 
    Details
    ISSN: 0947-3440
    Keywords: Cyclophanes ; Diels-Alder reactions ; Cyanoacetylenes ; [2+4] Cycloadditions ; Barrelenophanes ; Semibullvalenophanes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structures of the 1:1 and 1:2 addition products of dicyanoacetylene (2) to [2.2]paracyclophane (1) have been determined by X-ray structural analysis as 3 and 5, respectively. In contrast to literature reports, the latter possesses the „crossed“ double barrelene configuration. On irradiation 3 isomerizes to the semibullvalenophane 4 as was also shown by X-ray structural analysis.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199519950484
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Photoactive cyclophanes, I. Synthesis, photophysical and photochemical properties of cinnamophanes (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1949-1956 
    Details
    ISSN: 0947-3440
    Keywords: Cinnamates ; Spectroscopy ; Photocycloaddition ; Paracyclophanes ; X-ray structures ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to transfer the so-called topochemical control established by Schmidt and coworkers to fluid solutions, the [2.2]paracyclophane framework was substituted with two acryloyl substituents, one on each of the two decks. The 4 products thus formed are termed cinnamophanes. The pseudo-gem derivative, 1, was shown to undergo a very efficient stereospecific [2 + 2] photocycloaddition to form 5 with the highest quantum yield (0.8) ever observed for such a reaction. Whereas 2, 3 and 4, the regioisomers of 1, undergo a trans-cis photoisomerisation, compound 1 leads to the photocycloadduct as the sole photoproduct. This unusually fast cycloaddition reaction is not sensitive to oxygen and is largely unaffected by temperature variations. It is believed to be a singlet state reaction. The synthesis and a spectroscopic (absorption and fluorescence emission) study of 1-4 and 5 are described.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199511274
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    From p-Dimethoxybenzene to Crown-benzenophanes, 4Part 3: Ref.[11].- Cation-Complexing Properties of Bis(p-phenylene-34-crown-10) - A Structural and Spectrophotometric Study (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 97-106 
    Details
    ISSN: 0947-3440
    Keywords: Binding constants of metal cations ; Crown ethers ; Fluorescence ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compound 2, an electron-rich macrocyclic paracyclophane of the coronand type, known to form a charge-transfer complex with paraquat, was found to encapsulate strontium cations and to bind to magnesium cations. X-ray analysis revealed that 2 forms a 2:1 (metal/substrate) complex with Sr(ClO4)2, in which the two benzene rings weakly overlap, whereas in the single crystals grown from Mg(ClO4)2, the metal cation prefers to lie outside the coronand (1:1 stoichiometry). In acetonitrile solution, cations were observed to trigger an hypsochromic shift of the UV absorption spectra, proportional to their size and charge density. The stoichiometries and binding constants were also determined by UV absorption titration in acetonitrile using the LETAGROP-SPEFO program for several monovalent and divalent cations. For Na+, Ca2+, and Sr2+, 1:1 and 2:1 complexes were shown to be formed. In the free ligand, a weak interaction between the benzene rings was detected by fluorescence decay kinetic analysis, indicating the presence of two conformer populations within the nanosecond time scale. In solution, metal cations neither induce detectable excimer formation nor seem to have a strong influence on the fluorescence emission spectra, except a heavy atom quenching with Sr2+ and Ba2+, in contrast to the effect observed in absorption. However, Sr2+ and Mg2+induce a clear hypsochromic shift in the single crystal fluorescence spectra. Compound 2 was prepared by a new and efficient route which is compared to the previous procedures.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970115
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...