title: Regioisomerically controlled self-aggregation of zinc 3-hydroxymethyl-13-formyl-chlorin/porphyrin and their 3,13-inverted pigments.
abstract: Zinc 3-hydroxymethyl-13-formyl-chlorin, 1, and its 3,13-inverted (3-formyl-13-hydroxymethyl) regioisomer, 2, and their corresponding 17,18-dehydrogenated porphyrins, 3 and 4, were synthesized for models of natural bacteriochlorophylls-c/d/e possessing 3(1)-OH and 13-C=O groups which self-aggregate in main light-harvesting antenna systems of green photosynthetic bacteria. Zinc chlorins 1 and 2 were monomers in neat THF and gave an obvious difference in their visible absorption spectra, indicating that sole inversion of the 3- and 13-substituents in a chlorin chromophore controlled their optical properties. In an aqueous Triton X-100 solution (a nonionic surfactant), zinc 3(1)-OH-13-CHO-chlorin 1 and porphyrin 3 self-aggregated as do natural bacteriochlorophylls, while zinc 3-CHO-13(1)-OH chlorin 2 and porphyrin 4 (the 3,13-inverted regioisomers of 1 and 3) hardly formed such large oligomers, showing that the inversion of the peripheral 3,13-substituents made their oligomerization unfavorable. FT-IR spectra of aggregated 1-4 in the solid film and their molecular modeling calculations suggested that the 17(2)-C=O moiety in inverted 2/4 interacted with its own 13(1)-OH group to disturb further aggregation.
authors.affiliation: Department of Bioscience and Biotechnology, Faculty of Science and Engineering, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
authors.forename: Michio
authors.initials: M
authors.lastname: Kunieda
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tamiaki
mesh_terms: D008665:Metalloporphyrins / Q000737:chemistry*; D008823:Micelles; D015394:Molecular Structure; D017830:Octoxynol; D011166:Porphyrins / Q000737:chemistry*; D012996:Solutions; D013057:Spectrum Analysis; D013237:Stereoisomerism
chemical_list: D008665:Metalloporphyrins; D008823:Micelles; D011166:Porphyrins; D012996:Solutions; C519420:zinc 3-hydroxymethyl-13-formyl-chlorin; D017830:Octoxynol