Molecular and Electronic Stucture of the Phenoxyl
Radical
Methodology
MNDO/AM1/PM3 (Semiempirical MO)
Techniques Used
Building, Optimization, Analysis of Bonding Parameters,
Output Analysis,
UHF-SCF-MO calculation
Abstract. You will optimize the structure of the
phenoxyl radical. You will then examine the bond lengths and bond orders
in the radical. Finally, you will examine the HOMO of the radical, to estimate
the spin density distribution.
Procedure. Build and
optimize the phenoxyl radical using a semiempirical method. You would typically
use an Unrestricted Hartree Fock (UHF) method -- do not forget to change
the molecular multiplicity to doublet (2). Record the bond lengths and orders
for the molecule. Compute the HOMO of the molecule, and note where the major
coefficients are found. Where do you expect most of the unpaired electron
spin to be in this molecule (remember that the singly occupied HOMO or SOMO
controls the spin distribution)? [You may alternatively carry out a spin
density map for the molecule.]
Benchmarks. Based upon
electron spin resonance studies, phenoxyl radical is believed to have a
C=O (not a single bond), and to have its position of largest spin density
in the 4-position, para to the oxygen.
Results.
Copyright 1995 by Paul M. Lahti. All Rights Reserved.