Helimeric Porphyrinoids: Stereostructure and Chiral Resolution of meso-Tetraarylmorpholinochlorins

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• 作者：Christian Br眉ckner ; Daniel C. G. G枚tz ; Simon P. Fox ; Claudia Ryppa ; Jason R. McCarthy ; Torsten Bruhn ; Joshua Akhigbe ; Subhadeep Banerjee ; Pedro Daddario ; Heather W. Daniell ; Matthias Zeller ; Ross W. Boyle ; Gerhard Bringmann
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：June 8, 2011
• 年：2011
• 卷：133
• 期：22
• 页码：8740-8752
• 全文大小：1366K
• 年卷期：v.133,no.22(June 8, 2011)
• ISSN：1520-5126

文摘

The synthesis and chiral resolution of free-base and Ni(II) complexes of a number of derivatives of meso-tetraphenylmorpholinochlorins, with and without direct 尾-carbon-to-o-phenyl linkages to the flanking phenyl groups, is described. The morpholinochlorins, a class of stable chlorin analogues, were synthesized in two to three steps from meso-tetraphenylporphyrin. The conformations and the relative stereostructures of a variety of free-base and Ni(II) complexes of these morpholinochlorins were elucidated by X-ray diffractometry. Steric and stereoelectronic arguments explain the relative stereoarray of the morpholino-substituents, which differ in the free-base and Ni(II) complexes, and in the monoalkoxy, 尾-carbon-to-o-phenyl linked morpholinochlorins, and the dialkoxy derivatives. The Ni(II) complexes were all found to be severely ruffled whereas the free-base chromophores are more planar. As a result of the helimeric distortion of their porphyrinoid chromophores, the ruffled macrocycles possess a stable inherent element of chirality. Most significantly, resolution of the racemic mixtures was achieved, both by classical methods via diastereomers and by HPLC on a chiral phase. Full CD spectra were recorded and modeled using quantum-chemical computational methods, permitting, for the first time, an assignment of the absolute configurations of the chromophores. The report expands the range of known pyrrole-modified porphyrins. Beyond this, it introduces large chiral porphyrinoid 蟺-systems that exist in the form of two enantiomeric, stereochemically stable helimers that can be resolved. This forms the basis for possible future applications, for example, in molecular-recognition systems or in materials with chiroptic properties.