Ring-strain release in neutral and dicationic 7,8,17,18-tetra-bromo-5,10,15,20-tetra-phenyl-porphyrin: crystal structures of C44H26Br4N4 and C44H28Br4N4 (2+)·2ClO4 (-)·3CH2Cl2.
Two porphyrin complexes were studied to determine the effects of protonation on ring deformation within the porphyrin. The porphyrin 7,8,17,18-tetra-bromo-5,10,15,20-tetra-phenyl-porphyrin, C44H26Br4N4, was selected because the neutral species is readily doubly protonated to yield a dication, which was crystallized here with perchlorate counter-ions as a di-chloro-methane tris-olvate, C44H28Br4N4 (2+)·2ClO4 (-)·3CH2Cl2. The centrosymmetric neutral species is observed to have a mild 'ruffling' of the pyrrole rings and is essentially planar throughout; intra-molecular N-H⋯N hydrogen bonds occur. In contrast, the dication exhibits considerable deformation, with the pyrrole rings oriented well out of the plane of the porphyrin, resulting in a 'saddle' conformation of the ring. The charged species forms N-H⋯O hydrogen bonds to the perchlorate anions, which lie above and below the plane of the porphyrin ring. Distortions to the planarity of the pyrrole rings in both cases are very minor. The characterization of the neutral species represents a low-temperature redetermination of the previous room-temperature analyses [Zou et al. (1995 ▸). Acta Cryst. C51, 760-761; Rayati et al. (2008 ▸). Polyhedron, pp. 2285-2290], which showed disorder and physically unrealistic displacement parameters.
235 Nieuwland Science Hall, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
W Robert
WR
Scheidt
235 Nieuwland Science Hall, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
Hugues F
HF
Duval
235 Nieuwland Science Hall, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
Allen G
AG
Oliver
crystal structure; hydrogen bonding; prophyrin; ring puckering