Charge-Transfer Probes for Molecular Recognition via Steric Hindrance in Donor-Acceptor Pairs

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American Chemical Society

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Journal of the American Chemical Society

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DOI: 10.1021/ja9720319


Molecular association of various aromatic hydrocarbons (D, including sterically hindered donors) with a representative group of diverse acceptors (A = quinone, trinitrobenzene, tetracyanoethylene, tropylium, tetranitromethane, and nitrosonium) is visually apparent in solution by the spontaneous appearance of distinctive colors. Spectral (UV−vis) analyses of the colored solutions reveal their charge-transfer origin (λCT), and they provide quantitative information of the intermolecular association in the form of the KDA and εCT values for the formation and visualization, respectively, of different [D,A] complexes. Importantly, such measurements establish charge-transfer absorption to be a sensitive analytical tool for evaluating the steric inhibition of donor−acceptor association. For example, the steric differences among various hindered aromatic donors in their association with quinone are readily dramatized in their distinctive charge-transfer (color) absorptions and verified by X-ray crystallography of the charge-transfer crystals and/or QUANTA molecular modeling calculations of optimum intermolecular separations allowed by van der Waals contacts.


Accepted version. Journal of the American Chemical Society, Vol. 119, No. 40 (1997): 9393-9404. DOI. © 1997 American Chemical Society. Used with permission.

Sergey V. Lindeman and Rajendra Rathore were affiliated with the University of Houston at the time of publication.