Self-assembled monolayers of organosulphur molecules bearing calix[4]arene moieties.
We investigate the self-assembly of modified calix[4]arene on gold surfaces. Calix[4]arene was modified through a reaction sequence which led to assembling of the crown-5 moiety and to the insertion of two thioether groups into the starting molecule. The so-obtained calix[4]arene-crown-5 bis(7-thiatridecyloxy) (hereafter called calix[4]arene) was in the stable 1,3-alternate conformation. The calix[4]arene/gold interface was investigated by means of spectroscopic ellipsometry (SE), scanning tunneling microscopy (STM) and cyclic voltammetry (CV). SE data indicate a layer thickness compatible with the formation of a monomolecular layer. This result is confirmed by STM imaging which shows the formation of a high density of small pits, one gold layer deep, a typical feature of self-assembled organosulphur monolayers on gold. CV measurements performed in presence of the [Ru(NH(3))(6)(2+/3+)] redox couple indicate a passivation of the metal electrode, resulting in a reduction of the redox current, after the layer deposition. CV has also been used to investigate the selectivity properties of calix[4]arene-covered gold electrodes by measuring the redox current decrease in the presence of different salt solutions. It is found that calix[4]arene-covered electrodes are able to complex K(+) and Ba(2+), while no complexation is observed in the case of Li(+), Na(+), Cs(+), Mg(2+) and Ca(2+).
Cavalleri
O
O
INFM, Unità di Genova, Italy.
Vignolo
M
M
Strano
G
G
Natale
C
C
Rolandi
R
R
Thea
S
S
Prato
M
M
Gonella
G
G
Canepa
M
M
Gliozzi
A
A
D000327:Adsorption; D047250:Calixarenes / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D003460:Crystallization / Q000379:methods*; D017097:Electric Impedance; D004563:Electrochemistry / Q000379:methods*; D008422:Materials Testing; D009930:Organic Chemicals / Q000737:chemistry; D010636:Phenols / Q000737:chemistry*; D013457:Sulfur Compounds / Q000737:chemistry
D020099:Coated Materials, Biocompatible; D009930:Organic Chemicals; D010636:Phenols; D013457:Sulfur Compounds; C121325:calix(4)arene; D047250:Calixarenes