74251-58-4Relevant articles and documents
Supramolecular Recognition: Protonmotive-Driven Switches or Motors?
Crowley, James D.,Goshe, Andrew J.,Steele, Ian M.,Bosnich, Brice
, p. 1944 - 1955 (2004)
A dicationic molecular receptor bearing two cofacially disposed terpyridyl-Pd-Cl units forms stable 1:1 host-guest complexes with planar, neutral platinum(II) complexes. When the guest is modified to incorporate a pyridine group, the now basic guest is protonated by trifluoroacetic acid in acetonitrile solutions. The basic yellow guest forms a stable, deep red 1:1 host-guest complex with the yellow palladium receptor. Addition of trifluoroacetic acid to this host-guest complex leads to the displacement of the guest from the receptor. It is proposed that the dissociation of the guest is caused by electrostatic repulsion between the dicationic receptor and the positively charged protonated guest. Addition of base restores the host-guest complex. This protonmotive translocation of the guest from the host to the solution is discussed in terms of the mechanisms that drive molecular motors, the power stroke and the Brownian ratchet. It is concluded that the system is best described as a molecular switch that operates by the same mechanism as one stroke of a molecular motor.
Vinylogous Acyl Compounds. XIX. Vinylogous Acyl Group Migration in 2-Aminophenol. A Contribution to the Isomerization Mechanism of Mixed Diacyl Derivatives of 2-Aminophenol
Fischer, Gerhard W.
, p. 99 - 124 (2007/10/02)
Starting with 2-acylaminophenols 5 and 2-(2-acylvinylamino)-phenols 6 the N-acyl O-acylvinyl derivatives 7 of 2-aminophenol and their N-acylvinyl O-acyl isomers 8 were prepared and characterized.These vinylogous acyl compounds are able to isomerize in the same manner as simple O,N-diacylated 2-aminophenols 3 and 4, which under suitable conditions easily rearrange to give a dynamic equilibrium 34.Contrary to 3 and 4, however, the isomerization of 7 and 8 can be followed directly by spectroscopic methods, so that vinylogs of this type are useful model systems forstudying acyl group migrations in 2-aminophenol.Kinetic measurements show that the mutual rearrangement of 7 and 8 is a reversible general based catalyzed reaction, being first order with respect to substrate and catalyst.The isomerization of the N-acetyl derivatives 7a-h as well as the N-benzoyl derivatives 7i-p results in strictly linear HAMMETT correlations with positive reaction constant ρ.In the case of 7a-h the equilibrium constant K and the forward and reverse velocity constants k1 and k2 (including activation parameters) could be determined.The kinetic investigations and additional non-kinetic experiments indicate that the catalyst acts as proton acceptor and not - as hitherto supposed - as acyl group transferring nucleophile.Based on the findings an isomerization mechanism for mixed diacyl derivatives of 2-aminophenol is suggested.
