A planar dodecasubstituted porphyrin

Journal Article · Wed Apr 28 00:00:00 EDT 1993 · Inorganic Chemistry; (United States)

DOI:https://doi.org/10.1021/ic00061a030· OSTI ID:6259429

Senge, M O; Medforth, C J; Smith, K M ^[1]; Sparks, L D; Shelnutt, J A ^[2]

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1. Univ. of California, Davis (United States)
2. Sandia National Laboratories, Albuquerque, NM (United States)

Structural investigations of copper and nickel complexes of dodecasubstituted porphyrins bearing aryl groups at the meso positions and propano rings at the pyrrole [beta] positions reveal considerable differences in their macrocycle conformations. While the nickel complex NiTC5T(3,4,5-OMeP)P was found to exhibit a nonplanar conformation which is considerably more planar than that of other dodecasubstituted porphyrins, the corresponding copper complex CuTC5T(3,4,5-OMeP)P was planar. CuTC5T(3,4,5-OMeP)P thus represents the first example of a completely planar dodecasubstituted porphyrin. The crystal structures of both porphyrins reveal that the C[sub b]-C[sub b]-CH[sub 2] angle is 13[degrees] smaller than in OEP derivatives. This change, which moves the methylene and aryl substituents further apart, effectively removes the steric repulsion responsible for the very nonplanar conformations observed for other dodecasubstituted porphyrins. Molecular mechanics calculations using a porphyrin force field correctly predict a planar macrocycle conformation. The possible reasons for the discrepancy between the observed moderately nonplanar structure and the calculated planar structure for NiTC5T(3,4,5-OMeP)P are discussed. The usefulness of spectroscopic probes (NMR, resonance Raman, electronic absorption) in predicting the planarity of dodecasubstituted porphyrins is also examined. The identification of a planar dodecasubstituted porphyrin further indicates the flexibility of the tetrapyrrole macrocycle and has implications for the study of nonplanarity in synthetic porphyrins and metallotetrapyrrole containing biomolecules. 32 refs., 6 figs., 7 tabs.

• DOE Contract Number: AC04-76DP00789
• OSTI ID: 6259429
• Journal Information: Inorganic Chemistry; (United States), Vol. 32:9; ISSN 0020-1669
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
14 SOLAR ENERGY
COPPER COMPLEXES
MOLECULAR STRUCTURE
NICKEL COMPLEXES
ABSORPTION
ABSORPTION SPECTROSCOPY
CRYSTAL STRUCTURE
FLEXIBILITY
MATHEMATICAL MODELS
NUCLEAR MAGNETIC RESONANCE
PORPHYRINS
RAMAN SPECTROSCOPY
RESONANCE
X-RAY DIFFRACTION
CARBOXYLIC ACIDS
COHERENT SCATTERING
COMPLEXES
DIFFRACTION
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
LASER SPECTROSCOPY
MAGNETIC RESONANCE
MECHANICAL PROPERTIES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
SCATTERING
SORPTION
SPECTROSCOPY
TENSILE PROPERTIES
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties
140505 - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)