Title: Supramolecular Ex plorations: Ex hibiting the Ex tent of Ex tended Cationic Cyclophanes

Abstract

Acting as hosts, cationic cyclophanes, consisting of π-electron-poor bipyridinium units, are capable of entering into strong donor–acceptor interactions to form host–guest complexes with various guests when the size and electronic constitution are appropriately matched. A synthetic protocol has been developed that utilizes catalytic quantities of tetrabutylammonium iodide to make a wide variety of cationic pyridinium-based cyclophanes in a quick and easy manner. Members of this class of cationic cyclophanes with boxlike geometries, dubbed ExnBoxm4+ for short, have been prepared by altering a number of variables: (i) n, the number of “horizontal” p-phenylene spacers between adjoining pyridinium units, to modulate the “length” of the cavity; (ii) m, the number of “vertical” p-phenylene spacers, to modulate the “width” of the cavity; and (iii) the aromatic linkers, namely, 1,4-di- and 1,3,5-trisubstituted units for the construction of macrocycles (ExBoxes) and macrobicycles (ExCages), respectively. This Account serves as an exploration of the properties that emerge from these structural modifications of the pyridinium-based hosts, coupled with a call for further investigation into the wealth of properties inherent in this class of compounds. By variation of only the aforementioned components, the role of these cationic receptors covers ground that spans (i) synthetic methodology, (ii) extraction and sequestration,more » (iii) catalysis, (iv) molecular electronics, (v) physical organic chemistry, and (vi) supramolecular chemistry. Ex1Box4+ (or simply ExBox4+) has been shown to be a multipurpose receptor capable of binding a wide range of polycyclic aromatic hydrocarbons (PAHs), while also being a suitable component in switchable mechanically interlocked molecules. Additionally, the electronic properties of some host–guest complexes allow the development of artificial photosystems. Ex2Box4+ boasts the ability to bind both π-electron-rich and -poor aromatic guests in different binding sites located within the same cavity. ExBox24+ forms complexes with C60 in which discrete arrays of aligned fullerenes result in single cocrystals, leading to improved material conductivities. When the substitution pattern of the ExnBox4+ series is changed to 1,3,5-trisubstituted benzenoid cores, the hexacationic cagelike compound, termed ExCage6+, exhibits different kinetics of complexation with guests of varying sizes—a veritable playground for physical organic chemists. The organization of functionality with respect to structure becomes valuable as the number of analogues continues to grow. With each of these minor structural modifications, a wealth of properties emerge, begging the question as to what discoveries await and what properties will be realized with the continued exploration of this area of supramolecular chemistry based on a unique class of receptor molecules.« less

Authors:

Dale, Edward J. ^[1]; Vermeulen, Nicolaas A. ^[1]; Juríček, Michal ^[2]; Barnes, Jonathan C. ^[3]; Young, Ryan M. ^[4]; Wasielewski, Michael R. ^[4]; Stoddart, J. Fraser ^[1]

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+ Show Author Affiliations

1. Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
2. Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
3. Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
4. Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States, Argonne−Northwestern Solar Energy Research (ANSER) Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States

Publication Date:

2016-01-19

Research Org.:

Northwestern Univ., Evanston, IL (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division

OSTI Identifier:

1248415

Alternate Identifier(s):

OSTI ID: 1434641

Grant/Contract Number:  

FG02-99ER14999

Resource Type:

Published Article

Journal Name:

Accounts of Chemical Research

Additional Journal Information:

Journal Name: Accounts of Chemical Research Journal Volume: 49 Journal Issue: 2; Journal ID: ISSN 0001-4842

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY