Structural, Electrochemical, and Photophysical Properties of a Molecular Shuttle Attached to an Acid-Terminated Self-Assembled Monolayer

Abstract

Structural, electrochemical, and photophysical properties of a molecular shuttle attached to an acid-terminated self-assembled monolayer Cecchet, F; Rudolf, Petra; Rapino, S; Margotti, M; Paolucci, F; Baggerman, J; Kay, ER; Wong, JKY; Leigh, DA; Kay, Euan R. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. March 30, 2004; In Final Form: July 6, 2004 A benzylic amide macrocycle containing a pyridine moiety (macrocycle 2) and a related benzylic amide macrocycle-based molecular shuttle (naphthalimide rotaxane) with two pyridine moieties on the macrocyclic unit were grafted onto a self-assembled monolayer (SAM) of 11-mercaptoundecanoic acid (11-MUA) on gold. X-ray photoelectron spectroscopy (XPS) indicates that the molecules are linked to the SAM by hydrogenbonding. Electrochemical investigations show that the self-assembled monolayer is densely packed and well ordered and allows the estimation of the average thickness of the SAM alone and of the SAM functionalized with either macrocycle 2 or with naphthalimide rotaxane. The estimated thickness values suggest that the 11-MUA chains in the SAM are tilted with respect to the surface normal, as expected for ordered and stable SAMs, whereas the rotaxane molecules are oriented with the thread parallel to the SAM surface and macrocycle plan preferentially perpendicular to the surface. The photophysical studies of the naphthalimide rotaxane grafted onto the SAM on gold demonstrated that fluorescence is partially quenched but still remains easily measurable because the presence of the SAM reduces the quenching effect of the metal substrate. Moreover, the photophysical analysis clearly indicates that the naphthalimide part of the rotaxane strongly interacts with the carboxylic groups of the SAM, in agreement with the orientation of the molecule obtained from the electrochemistry.

Three State Redox-Active Molecular Shuttle That Switches in Solution and on a Surface

“…14 The relatively large, negative potentials required to cause switching, however, prevented the operation of such devices on surfaces. 20 Here, we report on a second member of this series, in which a naphthalene-1,4,5,8-diimide station can be switched between three different oxidation states. At each oxidation level, the naphthalene diimide exhibits a different binding affinity for the macrocycle, which leads to a different distribution of rings between two stations in a molecular shuttle.…”

Electron Transfer and Switching in Rigid [2]Rotaxanes Adsorbed on TiO2 Nanoparticles

“…The first one is that crown ether molecules form strong complexes with TBA + cations. [76] The presence of the macrocycle does not appear to disrupt the EDL, [77] so the TBA + concentration profile calculated for axle TiO 2 ·2 is also applicable (c.f. Figure 4).…”

Electroactive Rotaxanes and Catenanes

“…32 The grafting is achieved because of the formation of hydrogen bonds between the pyridine moiety of the rotaxane molecules and the carboxylic groups at the top of the Au-SAM. Cyclic voltammetric and electrochemical impedance spectroscopic measurements showed that the resulting SAM is densely packed and well ordered, and allowed the estimation of the average thickness of the monolayer.…”