MULTICONFORMATIONAL SURFACES IN PORPHYRINS - PREVIEWS INTO EXCITED-STATE LANDSCAPES

The crystal structures of four different conformers of the sterically encumbered porphyrins ZnDPP, H2DPP, and NiDPP are reported (DPP = 5,7, 8,10,12,13,15,17,18,20-dodecaphenylporphyrin). In combination with two previously published structures of H2DPP and NiDPP, the crystallograp hic results illustrate the remarkable range of different conformationa l surfaces possible within a single family of compounds with the same peripheral substituents. These results establish that the multiple con formational landscapes inferred from the excited-state dynamics of the molecules already exist in the ground state and thus offer previews i nto the conformations that may also be accessible in excited states. E lectron paramagnetic resonance (EPR) results for the ZnDPP and NiDPP p i cation radicals indicate that the radicals retain sl, spin-density p rofiles despite the extensive peripheral substitutions and the signifi cant nonplanarity of the parent compounds.