Structure and conformation of photosynthetic pigments and related compounds 7. On the conformation of the methyl ester of (20-methyl-phytochlorinato)nickel(II)--a bacteriochlorophyll c model compound.
The crystal and molecular structure of the title compound 4 have been determined by single crystal X-ray crystallography. The structure shows the typical S4-ruffled conformation observed for Ni(II) tetrapyrroles. Compared to the structure of the methyl ester of (13(2)-demethoxycarbonyl-pheophorbidato a)nickel(II), 4 shows a smaller Ca-Cm-Ca angle and a higher degree of conformational distortion at the methyl-substituted C20 position. This local distortion of the macrocycle might account for the bathochromic shifted absorption spectra of the bacteriochlorophylls c compared to the d-series. Crystal data: C35H38N4NiO3; tetragonal, P4(3)2(1)2, a = 15.335(7) A, c = 25.11(2) A, V = 5904, Z = 8, lambda(Mo K alpha) = 0.71069 A, mu = 0.701 mm-1, F(000) = 2624, 130 K, R = 0.058 for 5700 reflections with F > 4.0 sigma(F).
Senge
M O
MO
Department of Chemistry, University of California, Davis 95616.
Smith
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KM
D001426:Bacterial Proteins / Q000737:chemistry*; D001429:Bacteriochlorophylls / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008956:Models, Chemical; D008968:Molecular Conformation; D015394:Molecular Structure; D010788:Photosynthesis; D010860:Pigments, Biological / Q000737:chemistry
D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D010860:Pigments, Biological; C089924:nickel(II) 20-methyl-phytochlorin methyl ester; C002084:bacteriochlorophyll c