Crystallographic and EXAFS studies of conformationally designed nonplanar nickel(II) porphyrins

Journal Article · Wed May 05 04:00:00 EDT 1993 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00062a029· OSTI ID:6260770

Barkigia, K M; Renner, M W; Furenlid, L R; Fajer, J ^[1]; Medforth, C J; Smith, K M ^[2]

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1. Brookhaven National Lab., Upton, NY (United States)
2. Univ. of California, Davis (United States)

A series of Ni(II) tetraphenylporphyrins with varying [beta] substituents was examined by X-ray crystallography and EXAFS to assess peripheral steric effects on the conformations of the macrocycles. Crystallographic results establish that ethyl, propyl, and cyclohexenyl substitutions lead to saddle conformations of the macrocycle skeletons that minimize steric interactions between the [beta] and meso substituents. We have also taken advantage of the sensitivity of Ni-N distances to the planarity or ruffling of Ni porphyrins to establish that the saddle distortions of three compounds are maintained in solution. The Ni-N distances in solution agree well with the crystallographic values, within the precision of the EXAFS measurements, 0.02 A. The EXAFS results also establish that another compound is very distorted in solution. Although a structure of this compound has not been determined, the results are consistent with the crystallographic saddle structure of the free base analog, H[sub 2]DPP. The different conformations of the cyclopentenyl derivatives thus point to the high sensitivity of the skeletal distortions to steric interactions between [beta] and meso substituents. The present results, previous crystallographic determinations, and ongoing studies unambiguously establish that the skeletons of porphyrins and hydroporphyrins are highly flexible in vitro and in vivo. 31 refs., 3 tabs.

• DOE Contract Number: AC02-76CH00016; FG05-89ER45384
• OSTI ID: 6260770
• Journal Information: Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 115:9; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102* -- Chemical & Spectral Procedures
400201 -- Chemical & Physicochemical Properties
AROMATICS
CARBOXYLIC ACIDS
COMPLEXES
CRYSTALLOGRAPHY
DATA
EXPERIMENTAL DATA
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INFORMATION
MOLECULAR STRUCTURE
NICKEL COMPLEXES
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PORPHYRINS
REDOX POTENTIAL
SPECTROSCOPY
STEREOCHEMISTRY
TRANSITION ELEMENT COMPLEXES
X-RAY SPECTROSCOPY