Conformational landscapes of nonplanar porphyrins: superstructure, ligation, binding pockets and oxidation effects in Cu(II) porphyrins

摘要: Abstract The crystal structure of the porphyrin π cation radical Cu(II)OETPP + pyl 3 − ·py is reported (OETPP = 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenylporphyrin; py pyridine). compound readily prepared by oxidation in CH 2 Cl with excess I presence py. exhibits following features: (1) oxidized, not Cu(II). (2) Cu(II) pentacoordinated one as axial ligand. (3) sterically crowded macrocycle saddle shaped. This distortion and peripheral substituents combine to form superstructural, orthogonal ‘trenches’ above below plane. (4) trenches impose a specific orientation on ligated along NCuN axis also ‘distal’ binding pocket that traps second molecule (5) diamagnetic because antiferromagnetic coupling between unpaired electrons Cu d x -v orbitals which favored nonplanarity macrocycle. (6) more distorted than its nonplanar parent provides additional support for thesis porphyrins can easily undergo structural excursions. Conformational changes type here may influence reactivities radicals formed (photo)catalytic cycles photosynthetic hemoproteins comprised porphyrins. Crystallographic data: Cc ( No. 9), 21.706(2) A , b 16.077(2) c 19.993(2) β 103.34(1)°, V 6789(1) Z 4 .