Low-Energy States of Manganese–Oxo
Corrole
and Corrolazine: Multiconfiguration Reference ab Initio Calculations
ZhaoHailiang
PierlootKristine
H. G. LangnerErnie
SwartsJannie
C.
ConradieJeanet
GhoshAbhik
2012
Manganese(V)–oxo corrole and corrolazine have
been studied
with ab initio multiconfiguration reference methods (CASPT2 and RASPT2)
and large atomic natural orbital (ANO) basis sets. The calculations
confirm the expected singlet d<sub>δ</sub><sup>2</sup> ground
states for both complexes and rule out excited states within 0.5 eV
of the ground states. The lowest excited states are a pair of Mn(V)
triplet states with d<sub>δ</sub><sup>1</sup>d<sub>π</sub><sup>1</sup> configurations 0.5–0.75 eV above the ground state.
Manganese(IV)–oxo macrocycle radical states are much higher
in energy, ≥1.0 eV relative to the ground state. The macrocyclic
ligands in the ground states of the complexes are thus unambiguously
‘innocent’. The approximate similarity of the spin state
energetics of the corrole and corrolazine complexes suggests that
the latter macrocycle on its own does not afford any special stabilization
for the Mn<sup>V</sup>O center. The remarkable stability of an Mn<sup>V</sup>O octaarylcorrolazine thus appears to be ascribable to the
steric protection afforded by the β-aryl groups.