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Bis(N‐Confused Porphyrin) as a Semirigid Receptor with a Chirality Memory: A Two‐Way Host Enantiomerization through Point‐to‐Axial Chirality Transfer
Author(s) -
Chmielewski Piotr J.,
Siczek Marta,
Stępień Marcin
Publication year - 2015
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.201405598
Subject(s) - enantiopure drug , diastereomer , chemistry , chirality (physics) , adduct , porphyrin , enantiomer , circular dichroism , enantiomeric excess , zinc , stereochemistry , absolute configuration , crystallography , photochemistry , organic chemistry , enantioselective synthesis , catalysis , chiral symmetry , nambu–jona lasinio model , physics , quantum mechanics , quark
Abstract The adduct formation of protonated bis(N‐confused porphyrin) (BNCP, 3,3′‐bis( meso ‐tetratolyl‐2‐aza‐21‐carbaporphyrin) with chiral anions, carboxylic acids, and alcohols was studied in solution by means of 1 H NMR and circular dichroism (CD) spectroscopic analysis and DFT methods. The addition of enantiopure guests to the acidified BNCP resulted in optical activity that vanished after neutralization. Pairs of the 1 H NMR‐distinguishable diastereomers were formed when enantiopure guests were applied, although a single form was observed upon the addition of the racemic mixtures in each case. Unidirectional configuration change that led to diastereomeric excess was observed in several instances. Such an excess was memorized by metalation of the adducts with AgBF 4 , thus resulting in optically active silver(III) complexes of BNCP with some enantiomeric excess. Absolute configurations of BNCP cations and bis(zinc) and bis(silver(III)) complexes were determined on the basis of time‐dependent (TD)‐DFT calculations of their CD spectra. It was shown that some of the chiral carboxylates induced opposite directions of enantiomerization of di‐ and tetracations or di‐/tetracation and bis(zinc) complexes. The source of the optical activity of the equimolar diastereomeric mixture of adducts is discussed.