D. L. Cullen

syn- and anti-Conformation in oxodipyrromethenes: crystal and molecular structure of 3,4-dimethyl-2,2′-pyrromethen-5(1H)-one and its N-methyl derivative

The structure of two oxodipyrromethenes have been determined from three-dimensional diffractometer data. One is 3,4-dimethyl-2,2′-pyrromethen-5(1H)-one, C11H12N2O (I), which crystallizes in the monoclinic space group P21/n with a= 13.597(1), b= 5.809(1), c= 12.558(1)A, β= 101.29(1)°, Z= 4. The second is a derivative of this compound in which one of the pyrrole nitrogen atoms is methylated. This is 1′,3,4-trimethyl-2,2′-pyrromethen-5(1H)-one, C12H14N2O, (II). It also crystallizes in P21/n with a= 7.122(1), b= 22.873(1), c= 7.012(1)A, β= 104.64(2)°, Z= 4. Both structures were solved by direct methods and refined by full-matrix least squares. The isomers obtained both had the Z-configuration, but in (I), the nitrogen atoms are syn, while in (II), they are anti. Both compounds show relatively small deviation from planarity, but (II) shows larger deviations than (I). Both form hydrogen-bonded dimers between the lactam oxygen atom and pyrrole nitrogen atoms. A comparison of the structures in the solid state and in solution indicates the difference in energy between a planar and twisted conformation is small.

Unusual metalloporphyrins. Structure of the product from the reaction of dodecacarbonylruthenium with meso-tetraphenylporphine: ‘dicarbonyltetraphenylporphinatoruthenium(II)’

The product of a reaction of Ru3(CO)12 and meso-tetraphenylporphine, previously believed to be an ethanol adduct of a monocarbonyl derivative of ruthenium(II) tetraphenylporphine, has been found by a single crystal X-ray analysis to be a centrosymmetrical octahedral complex of dicarbonyltetraphenylporphinatoruthenium (II).

Conformational Analysis of the Non-Planar Deformations of Cobalt Porphyrin Complexes in the Cambridge Structural Database

Principal component analysis, cluster analysis, and various structural parameters have been used to differentiate the nonplanar deformations of cobalt(III) porphyrins. The results were compared with normal-coordinate structural decomposition analysis. Cobalt(III) porphyrins discussed in this paper do not undergo large wav, dom, and pro deformations and they were not considered in our analysis. The cis Cα-N-N-Cα dihedral angle is the best structural measure of ruffling and it is the only structural parameter that does not overestimate the extent of ruffling due to the presence of saddling. The average distance between the Cβ carbons and the plane comprising the four nitrogens, the four meso carbons and the cobalt ion is the best structural measure of saddling. No structural parameters were found that could be used in principal component analysis to find PCs that quantified the nonplanar deformations in cobalt(III) porphyrins. Cluster analysis was able to separate the sad, ruf, and planar structures, however, the preparation and symmetry adaptation of all the structures was complicated and was no more informative than the use of some of the univarient structural parameters. The NSD deformations are related to the vibrational energies and motions of the macrocycle and are thus the preferred description, but the more easily obtained structural parameters are useful measures of the normal coordinate deformations whenever a full NSD analysis is not possible.

Crystal and molecular structure of a 4,5-dimethyoxbilindione derived from etiobiliverdin-IVγ: a possible model compound for the phytochrome chromophore

The structure of a synthetic bile pigment, 3,8,12,17-tetraethyl-4,5-dimethoxy-2,7,13,18-tetramethyl-4,5-dihydrobilin-1,19(21H,24H)-dione, C33H44N4O4, has been determined using three-dimensional diffractometer data. It crystallizes in the triclinic space group P with a= 12,755 (2), b= 12.944(s), c= 12.615(2)A, α= 112.27°(2), β= 113.76°(2), γ= 75.45°(2), Z= 2. There is one-half of an n-hexane molecule of crystallization present per formula unit. The structure was solved by direct methods and refined by full-matrix least squares to yield a final R factor of 0.105. The compound, which could be considered as a model for the far-red form (Pfr) of the phytochrome chromphore, belongs to the class of bile pigments known trivially as bilipurpurins. Three of the four pyrrole rings form a conjugated system which is not strictly planar, but is quasi-helical in nature. The fourth ring which is joined to the others by an sp3 carbon atom, is considerably out of the plane of the other three. Bond lengths and angles show a large degree of bond fixation. There is intermolecular hydrogen bonding so that the molecules form hydrogen-bonded dimers.

Crystal and molecular structure of a photoisomer of an oxodipyrromethene: the E-isomer of 3,4-dimethyl-2,2′-pyrromethen-5(1H)-one

The structure of the E-isomer of an oxodipyrromethene, 3,4-dimethyl-2,2′-pyrromethen-5(1H)-one, C11H12N2O, has been determined. This was obtained by photoisomerization from the Z-isomer. It crystallizes in the monoclinic space group P21/a with a= 10.479(3), b= 8.643(2), c= 11.926(2)A, β= 114.07(1)°, Z= 4. The structure was solved by direct methods and refined by full-matrix least-squares to an R factor of 0.064. The molecule is in an anticlinal conformation with a dihedral angle of 49.8° about the methine single bond. Each oxygen atom is hydrogen-bonded to two nitrogen atoms which are located on two different molecules. Bond lengths and angles are similar to those found in the Z-isomer.

Crystal and molecular structure of 3,8,12-triethyl-14-formyl-2,7,13-trimethyl-1(15H)-tripyrrinone, a tripyrrolic aldehyde derived from aetiobiliverdin-IVγ

The structure of the title compound, a tripyrrolic compound derived from aetiobiliverdin-IVγ has been determined from three-dimensional X-ray diffractometer data. The tripyrrolic skeleton shows only small deviations from planarity. Adjacent rings assume the Z-configuration with the nitrogen atoms syn. Bond lengths in the three rings are quite different. No intra- or inter-molecular hydrogen bonding is observed. The compound crystallizes in the orthorhombic space group Pna21 with cell dimensions a= 9.773(2), b= 11.468(2), c= 19.402(3)A, Z= 4. The structure was solved by direct methods and refined by least-squares techniques to R 0.063 for 1 037 observed reflections.