Optically detected magnetic resonance studies of photoexcited /sup 17/O-benzophenone. Orbital rotation in the lowest triplet state

Journal Article · Mon Mar 01 04:00:00 EST 1982 · J. Chem. Phys.; (United States)

OSTI ID:5808413

Waeckerle, G; Baer, M; Zimmermann, H; Dinse, K H; Yamauchi, S; Kashmar, R J; Pratt, D W

The magnetically active isotope of oxygen /sup 17/O has been used to probe the changes in the electron charge and spin density distributions in oxygen valence orbitals which occur when benzophenone is excited to its lowest triplet state. The data obtained include the optically detected magnetic resonance (ODMR) and electron-nuclear double resonance spectra at both zero and high magnetic fields. New methods of analysis of zero-field ODMR spectra, appropriate when the second-order hyperfine splitting exceeds the quadrupole coupling, are described. This analysis yields the principal values of the electron fine-structure (D), oxygen hyperfine (A), and oxygen quadrupole (Q) tensors, and the orientation of their principal axes with respect to the molecular frame. It is found, consistent with expectations for an n..pi..( state, that the direction of the largest component of Q is different from that of the ground state. It is also found, by two independent methods, that the principal transverse axes of A and Q do not conform to the local C/sub 2v/ symmetry axes of the carbonyl group. This result is interpreted to mean that the axis of the n-type oxygen 2p orbital is rotated out of the carbonyl plane, a rotation which appears to be direct consequence of n..pi..(/..pi pi..( configurational mixing. In agreement with this, the principal values of D, A, and Q are different from those expected for a ''pure'' n..pi..( state. Other consequences of n..pi..(/..pi pi..( mixing, not only in benzophenone but also in the lowest triplet states of other aromatic carbonyls, are discussed briefly.

• Research Organization: Max-Planck-Institut fuer Medizinische Forschung, D-6900 Heidelberg, West Germany
• OSTI ID: 5808413
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 76:5; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
BENZOPHENONE
EVEN-ODD NUCLEI
FINE STRUCTURE
ISOTOPE EFFECTS
ISOTOPES
KETONES
LIGHT NUCLEI
MAGNETIC RESONANCE
NUCLEI
ORGANIC COMPOUNDS
OXYGEN 17
OXYGEN ISOTOPES
RESONANCE
STABLE ISOTOPES