Mercury-Mediated Attachment of Metal-Sandwich-Based Altitudinal Molecular Rotors to Gold Surfaces

Abstract

Gold surface attachment of altitudinal molecular rotors provided with ten -HgSCH 2 CH 2 SCH 3 "tentacles" has been monitored with ellipsometry, scanning tunneling microscopy, and X-ray photoelectron spectroscopy (XPS). The rotors appear to adsorb on the gold surface in the intended orientation, with rotor axle parallel to the surface, without any inclination for multilayer growth. According to XPS data, the sulfur-containing tentacles start to be detectably oxidized within hours of exposure to air and can be ultimately removed by washing. The rotor molecules nevertheless remain firmly attached in the desired orientation, apparently due to a direct interaction of their Hg atoms with the gold surface. When the tentacles are simplified to -HgOCOCF 3 substituents, the molecules adhere to the surface as well, but not always in the desired orientation.

The preparation, spectroscopy, structure and electrochemistry of some [Co(η4-C4Ph4)(η5-C5H4R)] complexes

“…We had hoped to prepare the bromo-analogue of 5 directly from 1 by reaction with N-bromosuccinimide and dibenzoylperoxide or azobisisobutyronitrile (AIBN), but both reactions failed. 5 proved an excellent precursor for the triphenyl phosphonium salt [7]Cl, but it failed to react with P(OEt) 3 . The HornereWadswortheEmmons reagent 6 [25] was obtained in the same way as its ferrocene counterpart [26] by a modification of the basic Michaelis reaction [27] in which Na[P(O)(OEt) 2 ] is reacted with the alcohol 4.…”

“…However this has not been reported despite [Fc 3 COH] being first prepared in 1962 [47] and studied intensively more recently [36,39,48], though there have been investigations of the electrochemistry of other multiferrocenyl compounds [45,49]. We were able to carry out our comparison because of a gift of [Fc 3 DE ox ¼ 200 mV). Application of increased anodic potential to [Fc 3 COH] 2þ generates the distinctive adsorption/stripping waveform.…”

“…A lot of recent work has been application driven, with several different foci: asymmetric synthesis and catalysis [2], molecular rotors [3] and as a Tamoxifen analogue [4]. The chemistry of [Co(h 4 -C 4 Ph 4 )(h 5 -C 5 H 5 )] complexes however is not as well-developed as that of the ferrocenyl analogues.…”

“…[Co(h 4 -C 4 Ph 4 )(h 5 3 Cl] and then Ph 2 C 2 (R ¼ CHO and CO 2 Me) [6e9], and we have found them to be effective entry compounds. Here they are used in a variety of reactions to prepare a diverse range of [Co(h 4 -C 4 Ph 4 )(h 5 -C 5 H 4 R)] complexes, some of which have been foreshadowed in our study of [Co(h 4 -C 4 R 4 ) (h 5 -C 5 H 4 R)] (R ¼ Me and Et) derivatives [10].…”

Chemistry of the highly stable hindered cobalt sandwich compound (η5-Cp)Co(η4-C4Ph4) and its derivatives

“…XPS data indicated that the rotors 206 and 208, which contain sulfur containing tentacles start to oxidize within hours of air exposure and can be ultimately removed by washing but the rotor molecules remain firmly attached in the desired orientation due to direct interaction of Hg atoms with the gold surface. Compounds having HgOCOCF 3 as tentacles also adhere to the surface but not always in the desired orientation [86].…”