Please use this identifier to cite or link to this item: https://hdl.handle.net/10356/93798
Title: Rigidity-stability relationship in interlocked model complexes containing phenylene-ethynylene-based disubstituted naphthalene and benzene
Authors: Goddard III, William A.
Yoon, Il.
Miljanić, Ognjen Š.
Benítez, Diego
Zhao, Yanli
Tkatchouk, Ekaterina
Stoddart, J. Fraser
Keywords: DRNTU::Science::Chemistry::Crystallography::Crystal structure and growth
Issue Date: 2009
Source: Yoon, I., Benítez, D., Miljanić, O. S., Zhao, Y. L., Tkatchouk, E., Goddard, W. A., & Stoddart, J. F. (2009). Rigidity−Stability Relationship in Interlocked Model Complexes Containing Phenylene-Ethynylene-Based Disubstituted Naphthalene and Benzene. Crystal Growth & Design, 9(5), 2300-2309.
Series/Report no.: Crystal growth & design
Abstract: Structural rigidity has been found to be advantageous for molecules if they are to find applications in functioning molecular devices. In the search for an understanding of the relationship between the rigidity and complex stability in mechanically interlocked compounds, the binding abilities of two π-electron-rich model compounds (2 and 4), where rigidity is introduced in the form of phenylacetylene units, toward the π-electron deficient tetracationic cyclophane, cyclobis(paraquat-p-phenylene) (CBPQT4+), were investigated. 1,4-Bis(2-(2-methoxyethoxy)ethoxy)-2,5-bis(2-phenylethynyl)benzene 2 and 1,5-bis(2-(2-methoxyethoxy)ethoxy)-2,6-bis(2-phenylethynyl)naphthalene 4 were synthesized, respectively, from the appropriate precursor dibromides 1 and 3 of benzene and naphthalene carrying two methoxyethoxyethoxy side chains. The rigid nature of the compounds 2 and 4 is reflected in the reduced stabilities of their 1:1 complexes with CBPQT4+. Binding constants for both 2 (100 M−1) and 4 (140 M−1) toward CBPQT4+ were obtained by isothermal titration microcalorimetry (ITC) in MeCN at 25 °C. Compounds 1−4 were characterized in the solid state by X-ray crystallography. The stabilization within and beyond these molecules is achieved by a combination of intra- and intermolecular [C−H···O], [C−H···π], and [π−π] stacking interactions. The diethyleneglycol chains present in compounds 1−4 are folded as a consequence of both intra- and intermolecular hydrogen bonds. The preorganized structures in both precursors 1 and 3 are repeated in both model compounds 2 and 4. In the structures of compounds 2 and 4, the geometry of the rigid backbone is differentthe two terminal phenyl groups are twisted with respect to the central benzenoid ring in compound 2 and roughly perpendicular to the plane central naphthalene core in compound 4. To understand the significantly decreased stabilities of these complexes toward rigid guest molecules, relative to more flexible systems, we performed density functional theory (DFT) calculations using the newly developed M06-suite of density functionals. We conclude that the reduced binding abilities are a consequence of electronic and not steric factors, originating from the extended delocalization of the aromatic system.
URI: https://hdl.handle.net/10356/93798
http://hdl.handle.net/10220/7044
ISSN: 1528-7483
DOI: 10.1021/cg801106h
Rights: © 2009 American Chemical Society
Fulltext Permission: none
Fulltext Availability: No Fulltext
Appears in Collections:SPMS Journal Articles

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