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Synthesis, Structural Characterization and Complexation Properties of the First “Crowned” Dipyrrolylquinoxalines
Author(s) -
Kirkovits Gregory J.,
Zimmerman Rebecca S.,
Huggins Michael T.,
Lynch Vincent M.,
Sessler Jonathan L.
Publication year - 2002
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200211)2002:22<3768::aid-ejoc3768>3.0.co;2-r
Subject(s) - chemistry , crown ether , hydrogen bond , supramolecular chemistry , crystallography , molecule , tetramer , crystal structure , single crystal , intermolecular force , 18 crown 6 , stereochemistry , ion , organic chemistry , enzyme
The synthesis of four crown‐substituted dipyrrolylquinoxalines 1−4 is reported. The key step in the synthesis is reaction of a 1,2‐diaminobenzocrown with 1,2‐bis(1 H ‐pyrrol‐2‐yl)ethanedione ( 20 ). A single crystal X‐ray diffraction analysis of the 18‐crown‐6‐dipyrrolylquinoxaline 1 revealed that this molecule forms a tetramer centered around a single molecule of water, with no fewer than 10 hydrogen bonds holding the supramolecular structure together. In the case of the 15‐crown‐5‐dipyrrolylquinoxaline 2 , however, X‐ray diffraction analysis revealed that this species exists as a dimeric pair in the solid state, with the NH protons of one pyrrole lying within hydrogen‐bonding distance of two oxygen atoms on an adjacent crown ether. A second single crystal structure of 2 was solved; it demonstrated that this system is able to coordinate a potassium cation, thereby forming an intermolecular sandwich complex, at least in the solid state. In [D 6 ]acetone solution receptor 2 and congeners 1 , 3 and 4 were also found to complex sodium and potassium cations within the crown diethyl ether binding sites, in a 1:1 manner as judged by 1 H NMR spectroscopic analyses. Although systems 1 − 4 appear to bind fluoride anion as well as cations, the inability to obtain quantitative binding affinities of 1 − 4 with fluoride anion rendered the evaluation of the systems for cooperative binding impossible. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)