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  • 1
    Electronic Resource
    Electronic Resource
    Molecular mechanics of bridged ferrocene derivatives: Conformational energy surfaces of [3]-, [4]- and [45] ferrocenophanes (1992)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 5 (1992), S. 382-394 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A molecular mechanical model is presented which allows computational interpretation of stereodynamics in ferrocenophanes by using a simple form of bending potential for angles involving the central iron atom and extended to carbon atoms of different cyclopentadienyl rings. Potential energy surfaces of [3] -, [4] - and [45] ferrocenophanes were studied in detail. For [3] ferrocenophane, the calculated energy barrier of the bridge reversal process agrees well with the experimental value. The previous interpretation of a rigid bridge in [4] ferrocenophane is questioned on the basis of the calculated low barriers. The predominance of experimentally indistinguishable enantiomeric pairs may be responsible for the misinterpretation. [45] Ferrocenophane is estimated to interconvert into D5-symmetric global energy minima over barriers of 13-15 kcal mol-1 through one-by-one flipping of five tetramethylene bridges.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610050703
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  • 2
    Electronic Resource
    Electronic Resource
    Energy-minimum structure of the hydrocarbon portion of [45] (1,2,3,4,5)ferrocenophane (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 602-610 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In order to assist in the interpretation of the D5h molecular structure of [45] (1,2,3,4,5)ferrocenophane (1) obtained from x-ray crystallographic analysis, a hypothetical hydrocarbon C30H40 (2) was derived from 1 by removing the iron atom and subjected to geometry optimization by molecular mechanics. A stable D5 conformer was found for 2, which has a g+ g- g+ helical bridge conformation and a ring-ring distance almost identical with that in 1 and ferrocene itself. Optimization of a perhydrogenated hydrocarbon model gave a highly strained C1 structure.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610020803
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  • 3
    Electronic Resource
    Electronic Resource
    Re-evaluation of 1,4-Non-bonded interactions in molecular mechanics (1992)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 5 (1992), S. 567-574 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Analysis of the sum of two-centre terms obtained from semi-empirical molecular orbital calculations into atom-pair interactions revealed a unique behaviour of 1,4-non-bonded atom-pair interactions compared with 1,5- and longer range interactions. Explicit inclusion of a special 1,4-non-bonded interaction term in an MM2-like molecular mechanics scheme gave a test force field with good performance.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610050903
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  • 4
    Electronic Resource
    Electronic Resource
    Conformational interconversion of [1.1] ferrocenophane: A molecular mechanics study (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 107-112 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A molecular mechanics scheme developed for bridged ferrocene derivatives was applied to study the conformational energy surface of [1.1] ferrocenophane (1). The mechanism of the intramolecular interconversion of 1 is shown to be different from the mechanism of the syn-syn exchange proposed earlier for this ‘molecular acrobat’.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060207
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  • 5
    Electronic Resource
    Electronic Resource
    An empirical extension of the karplus equationFor a preliminary communication, see Ref. 1. (1990)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 28 (1990), S. 668-674 
    Details
    ISSN: 0749-1581
    Keywords: Karplus equation ; Vicinal proton-proton coupling ; Non-additive substituent effects ; MM2 ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Karplus equation is expanded to contain 11 mutually independent structural terms and 22 adjustable parameters. These terms are selected on an empirical basis and combined linearly (Eqn 4). The new equation reproduces 198 NMR vicinal 1H-1H coupling constants determined in less polar solvents with a standard deviation of 0.33 Hz. The equation can be applied to norbornene derivatives, for which some of the previous modifications did not work well. Among new factors introduced in this modification to the Karplus-type equation are Mullay's group electro-negativity used in the evaluation of the α- and β-substituent effects, the C—C length and the C—C—H valence angles of the coupled H—C—C—H system, and the through-space interactions between a coupled proton and a non-bonded atom within the molecule. The four most important terms are the two cosine functions, originally used by Karplus, one form of the α-substituent effect and the C—C—H valence angles. These four terms alone give an accuracy of 0.42 Hz.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260280803
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    Paper (German National Licenses)
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