Endo and exo phenylene-bridged hetero (O,S) silacrown ether rotors including an unexpected structural example of the chloromethyl exchange rule for 1,4-bis(X2methylsilyl)- benzene, XCl, Me

• Published in: Applied organometallic chemistry 2010-12, Vol.24 (12), p.872-877
• Main Authors: Metta-Magana, Alejandro J., Vargas-Pineda, Diana G., Martinez-Perez, Carlos A., Lopez-Cardoso, Marcela, Pannell, Keith H.
• Format: Article
• Language: English
• Subjects: chloro-methyl exchange rule; crystal structure; molecular rotor; silacrown ether
• ISSN: 0268-2605; 1099-0739
• DOI: 10.1002/aoc.1721

Artificial molecular rotors are of current interest because of the various applications that they could have as materials. However, many of them have the common problem of interdigitation and solvent inclusion in the crystal structure. In this work, we prepare a potential rotor with a stator formed by a sila‐hetero(O, S) crown ether moiety and the phenylene bridge as rotator. The use of the sulfur atoms in the stator allows the formation of HB avoiding those common problems. The study of the potential activity as molecular rotors was done via structural analysis by single crystal X‐ray diffraction, comparing them with previously reported rotors for which the activation energies have been reported. A comparison between the exo and endo diastereoisomers was done, showing that the change in stereochemistry affects the conformation, making one of them a better rotor. In addition, we found that the crystal structure of the intermediate 1,4‐bis(dichloro‐methylsilyl)‐benzene represents an example of the non‐applicability of the so‐called chloro‐methyl exchange rule, with four groups substituted. Copyright © 2010 John Wiley & Sons, Ltd. A structural analysis by SC‐XRD of two potential molecular rotors was done. They were compared with other rotors for which the activation energies have been reported, showing that one isomer is a better rotor than the other.