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Enantiomerically Pure Alleno–Acetylenic Macrocycles: Synthesis, Solid‐State Structures, Chiroptical Properties, and Electron Localization Function Analysis
Author(s) -
RiveraFuentes Pablo,
AlonsoGómez José Lorenzo,
Petrovic Ana G.,
Seiler Paul,
Santoro Fabrizio,
Harada Nobuyuki,
Berova Nina,
Rzepa Henry S.,
Diederich François
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201001087
Subject(s) - chemistry , molecular orbital , enantiomer , computational chemistry , atomic orbital , topology (electrical circuits) , electron , stereochemistry , molecule , organic chemistry , physics , quantum mechanics , combinatorics , mathematics
New enantiomerically pure alleno–acetylenic macrocycles were prepared by oxidative homocoupling of optically active 1,3‐diethynylallenes. Enantiomer separation resulted from a combined strategy of synthesis and chiral HPLC techniques. Two other achiral stereoisomers were also isolated and fully characterized. In addition, the X‐ray structures of the chiral D 4 ‐ and C 2 ‐symmetric macrocycles are reported. The chiroptical properties of these macrocycles are discussed on the basis of quantum chemical calculations, by using the CAM‐B3LYP functional. Studies were carried out to investigate the vibronic fine structure observed experimentally in the UV/Vis and CD spectra. The origin of the intense chiroptical response of the chiral alleno–acetylenic macrocycles is explained by considering the topology of the molecular orbitals involved, thus relating electronic properties to structural features. Further analysis of the canonical molecular orbitals and the electron localization function (ELF) shows that these macrocycles belong to a relatively rare class of highly stable and formally anti‐aromatic Hückel compounds.