The crystal structures of four different conformers of the
sterically encumbered porphyrins ZnDPP,
H2DPP,
and NiDPP are reported (DPP =
2,3,5,7,8,10,12,13,15,17,18,20-dodecaphenylporphyrin).
In combination
with two previously published structures of H2DPP and
NiDPP, the crystallographic results illustrate the
remarkable range of different conformational surfaces possible within a
single family of compounds with the
same peripheral substituents. These results establish that the
multiple conformational landscapes inferred
from the excited-state dynamics of the molecules already exist in the
ground state and thus offer previews
into the conformations that may also be accessible in excited states.
Electron paramagnetic resonance (EPR)
results for the ZnDPP and NiDPP π cation radicals indicate that the
radicals retain a2u spin-density profiles
despite the extensive peripheral substitutions and the significant
nonplanarity of the parent compounds.
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