Highly Efficient Chirality Transfer from Diamines Encapsulated within a Self‐Assembled Calixarene–Salen Host |
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Authors: | Luis Martínez‐Rodríguez Dr. Nuno A. G. Bandeira Prof. Dr. Carles Bo Prof. Dr. Arjan W. Kleij |
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Affiliation: | 1. Institute of Chemical Research of Catalonia (ICIQ), Av. Pa?sos Catalans 16, 43007 Tarragona (Spain);2. Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcel?lí Domingo s/n, 43007 Tarragona (Spain);3. Catalan Institute of Research and Advanced Studies (ICREA), Pg. Lluís Companys 23, 08010 Barcelona (Spain) |
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Abstract: | A calix[4]arene host equipped with two bis‐[Zn(salphen)] complexes self‐assembles into a capsular complex in the presence of a chiral diamine guest with an unexpected 2:1 ratio between the host and the guest. Effective chirality transfer from the diamine to the calix–salen hybrid host is observed by circular dichroism (CD) spectroscopy, and a high stability constant K2,1 of 1.59×1011 M ?2 for the assembled host–guest ensemble has been determined with a substantial cooperativity factor α of 6.4. Density functional calculations are used to investigate the origin of the stability of the host–guest system and the experimental CD spectrum compared with those calculated for both possible diastereoisomers showing that the M,M isomer is the one that is preferentially formed. The current system holds promise for the chirality determination of diamines, as evidenced by the investigated substrate scope and the linear relationship between the ee of the diamine and the amplitude of the observed Cotton effects. |
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Keywords: | calixarenes chirality transfer encapsulation host– guest systems salens |
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