NMR at cryogenic temperatures: A {sup 13}C NMR study of ferrocene

Journal Article · Thu Sep 24 04:00:00 EDT 1998 · Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory

DOI:https://doi.org/10.1021/jp981079l· OSTI ID:655335

Orendt, A M; Facelli, J C; Jiang, Y J; Grant, D M ^[1]

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1. Univ. of Utah, Salt Lake City, UT (United States)

A new cryogenic apparatus is described that can be used to obtain NMR spectra at temperatures down to 8--10 K. The static solid {sup 13}C NMR spectrum of ferrocene is recorded at that temperature. Spectra recorded at higher temperatures show that ferrocene is still freely rotating about its 5-fold symmetry axis on the {sup 13}C NMR time scale at 45--50 K. A comparison of the principal values of the {sup 13}C chemical-shift tensor obtained from the room- and low-temperature spectra of ferrocene indicates that the lowest frequency chemical shift principal component, {delta}{sub 33}, is tilted off this symmetry axis by approximately 12{degree}. Quantum chemical calculations of the chemical-shift tensor, completed on structures of ferrocene from the literature as well as on optimized structures with the cyclopentadienyl rings locked in both the staggered and eclipsed arrangements, predict the angle between the {delta}{sub 33} direction and the rotation axis to be between 11 and 15{degree}, depending upon the geometry used in the calculation. The calculations also predict the sign of the angular perturbation, information not obtained from the experiment. An explanation of this angular change in the {delta}{sub 33} direction is provided by the composition of the molecular orbitals.

• Sponsoring Organization: USDOE, Washington, DC (United States); National Science Foundation, Washington, DC (United States)
• DOE Contract Number: FG03-94ER14452
• OSTI ID: 655335
• Journal Information: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 39 Vol. 102; ISSN 1089-5639; ISSN JPCAFH
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ATOMIC MODELS
CARBON 13
FERROCENE
MOLECULAR STRUCTURE
MOLECULES
NUCLEAR MAGNETIC RESONANCE
QUANTUM MECHANICS
TEMPERATURE RANGE 0000-0013 K
TEMPERATURE RANGE 0013-0065 K