A Solvate of the Diacetate Salt of the Octaethyltetraphenylporphyrin Dication, H\u3csub\u3e4\u3c/sub\u3eOETPP\u3csup\u3e2+\u3c/sup\u3e.2CH\u3csub\u3e3\u3c/sub\u3eCOO\u3csup\u3e-\u3c/sup\u3e.3CH\u3csub\u3e3\u3c/sub\u3eCOOH.- CH\u3csub\u3e2\u3c/sub\u3eCI\u3csub\u3e2\u3c/sub\u3e

The structure of 2,3,7,8,12,13,17,18-octaethyl-5,10,15,-20-tetraphenylporphyrin(2+) diacetate acetic acid dichloromethane solvate, C60H64N42+.2C2H3O2-.3C2H4-O2.CH2CI2, has been determined at 200K. The molecule is severely non-planar and adopts an $4 saddle shape. It is the most distorted member of the OETPP series reported to date, with displacements of the β- pyrrole C atoms from the plane of the four N atoms as great as 1.42 Å, and acute tilts of the phenyl rings relative to the porphyrin plane. The two acetate counterions act as bidentate ligands which bond to the H atoms on opposite pairs of N atoms. The crystal lattice also contains three acetic acid molecules of solvation per porphyrin molecule, all of which are involved in hydrogen bonds to the acetate molecules. An \u27innocent\u27 molecule of CH2CI2 is also present

Crystal and Molecular Structure of Methyl Bacteriopheophorbide a. A Model for a Primary Electron Acceptor in Bacterial Photosynthesis

Bacteriopheophytin is a key component in the mechanism by which photosynthetic bacteria transduce solar energy into chemical form. The structure of methyl bacteriopheophorbide a, a bacteriopheophytin derivative, has been determined by three-dimensional X-ray diffraction. The compound crystallizes in space group PI in a unit cell containing a molecule of methyl bacteriopheophorbide and a benzene molecule of crystallization, with lattice constants a = 7.2502 (8) Å, b = 8.1070 (9) Å, c = 17.224 (5) Å, α = 90.80 (2)°, β = 94.17 (2)°, and 7 = 110.38 (1)°. The structure has been refined with isotropic thermal parameters on F by full-matrix least squares to RF = 0.110, based on 860 reflections. The molecules associate in chains via π-π interactions with ring I of one molecule overlapping ring III of its neighbor with a vertical separation of 3.6 Å. The one-dimensional chains form two-dimensional layers without the intervention of the hydrogen bonding by water molecules previously reported for chlorophyllides. This work represents the first crystallographic determination of a bacteriochlorin and confirms the canonical structures and relative orientations of the five chiral centers of bacteriochlorophyll a derivatives. © 1981, American Chemical Society. All rights reserved

Self-assembled zinc pheoporphyrin dimers. Models for the supramolecular antenna complexes of green photosynthetic bacteria?

The molecular structure of the zinc porphyrin analog of methyl-8,12-diethylbacteriopheophorbide d has been determined by X-ray diffraction. The crystallographic study was undertaken to provide structural foundations for the several models proposed for the supramolecular organization of bacteriochlorophyll (BChl) c, d and e antenna chromophores in vivo and in vitro. Surprisingly, the Zn porphyrins form hydrogen-bonded dimers with extended π-π interactions without the expected ligation of the Zn by the 3-(1-hydroxyethyl) group that distinguishes the BChls c, d and e from all other photosynthetic (bacterio) chlorophylls. The crystallographic results provide the first structural benchmarks for this class of metalloporphyrin derivatives and set structural boundaries for other modes of aggregation considered for the chromophores in vitro and in vivo. © 1997 Elsevier Science B.V

XAFS and Crystallographic Studies of Ni(II) Porphyrins in Single Crystals and Solution

Nickel porphyrins serve as models for the active sites of several biological processes. Crystallographic and EXAFS results for a Ni meso-tetrapropyl porphyrin (NiTPrP) yield different Ni-N distances in solution and in the solid state. The Ni-N distances determined by single crystal polarized XAS and X-ray diffraction agree well. Polarized XANES experiments further establish that the pre-edge feature observed in square planar Ni(H) complexes is a ls-4pz transition. The single crystal and solution EXAFS results demonstrate that conformational variations of the porphyrin macrocycle can readily be imposed by environmental and/or packing forces and can thereby modulate the chemical and physical properties of porphyrinic chromophores and prosthetic groups