On the possibility to accelerate the thermal isomerizations of overcrowded alkene-based rotary molecular motors with electron-donating or electron-withdrawing substituents
2016 (English)In: Journal of Molecular Modeling, ISSN 1610-2940, E-ISSN 0948-5023, Vol. 22, no 9, 219- p.Article in journal (Refereed) Published
We employ computational methods to investigate the possibility of using electron-donating or electron-withdrawing substituents to reduce the free-energy barriers of the thermal isomerizations that limit the rotational frequencies achievable by synthetic overcrowded alkene-based molecular motors. Choosing as reference systems one of the fastest motors known to date and two variants thereof, we consider six new motors obtained by introducing electron-donating methoxy and dimethylamino or electron-withdrawing nitro and cyano substituents in conjugation with the central olefinic bond connecting the two (stator and rotator) motor halves. Performing density functional theory calculations, we then show that electron-donating (but not electron-withdrawing) groups at the stator are able to reduce the already small barriers of the reference motors by up to 18 kJ mol(-1). This result outlines a possible strategy for improving the rotational frequencies of motors of this kind. Furthermore, exploring the origin of the catalytic effect, it is found that electron-donating groups exert a favorable steric influence on the thermal isomerizations, which is not manifested by electron-withdrawing groups. This finding suggests a new mechanism for controlling the critical steric interactions of these motors.
Place, publisher, year, edition, pages
SPRINGER , 2016. Vol. 22, no 9, 219- p.
Electronic effects; Molecular motors; Quantum chemistry; Rotary rates; Steric effects
IdentifiersURN: urn:nbn:se:liu:diva-131672DOI: 10.1007/s00894-016-3085-yISI: 000382748100024PubMedID: 27553304OAI: oai:DiVA.org:liu-131672DiVA: diva2:1014929
Funding Agencies|Linkoping University; Swedish Research Council [621-2011-4353]; Olle Engkvist Foundation; Carl Trygger Foundation2016-10-032016-09-302016-11-16