Representation of nonplanar structures of nickel(II) 5,15-disubstituted porphyrins in terms of displacements along the lowest-frequency normal coordinates of macrocycle
- Sandia National Lab., Albuquerque, NM (United States)
- Sandia National Lab., Albuquerqe, NM (United States)
- Univ. of California, Davis, CA (United States)
The influence of substituents with increasing steric demands on the structure of nickel(II) 5,15-disubstituted porphyrins has been investigated with X-ray crystallography, UV-visible absorption spectroscopy, resonance Raman spectroscopy, molecular energy optimization calculations, and INDO/s molecular orbital calculations. Nickel 5,15-diphenylporphyrin is predicted by molecular mechanics calculations to be a mixture of planar and nonplanar conformers. All of the nickel dialkylporphyrins (where the alkyl group is propyl, isopropyl, and tert-butyl) are calculated to be in predominantly gabled (gab) conformation resulting from an {alpha}{alpha} orientation of the constituents with respect to the macrocycle. This nonplanar gab distortion is made up of a linear combination of distortions along the lowest-frequency out-of-plane macrocycle normal coordinates of A{sub 2u} (doming) and B{sub 1u} (ruffling) symmetry types. A higher energy stable {alpha}{beta} conformer is also predicted for dialkylporphyrins, and its nonplanar structure can be represented as an equal combination of distortions along the x- and y-components of the lowest-frequency E{sub g} (waving) normal coordinate. The nonpolar structures calculated by using molecular mechanics have been structurally decomposed into the displacements along the lowest-frequency normal coordinate of each symmetry type, and the contributions of each type to the total distortion in the calculated structures agree well with contributions obtained from structural decompositions of the available X-ray crystal structures. 42 refs., 10 figs., 4 tabs.
- Research Organization:
- Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 458647
- Journal Information:
- Journal of the American Chemical Society, Vol. 118, Issue 51; Other Information: PBD: 25 Dec 1996
- Country of Publication:
- United States
- Language:
- English
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