Molecular junctions and switches are a focus of considerable current interest as possible basic components of future molecular electronic devices. [1,2] During the past decades molecular switches based on different concepts and mechanisms have been proposed, synthesized and investigated. [3] These include reversible bond breaking, [1,4,5] translocation of part of multi-components molecular assemblies, [6,7] proton transfer, [1,4,8] or reversible conformational changes of a system with geometry-dependent electronic properties. [9][10][11] The interplay of the cation-binding properties of crown-ether and conformational changes has already been investigated. Thus, Shinkai used the photoisomerization of azobenzene units inserted in crown ether systems to modulate the cation binding properties of the cavity. [12] From a different viewpoint, we have shown that the cation-binding ability of a polyether loop Accepted to 2 attached at two fixed points of an oligothiophene chain can serve as driving force to generate changes in the geometry and hence electronic properties of the conjugated system. [13] A similar approach has been previously used for the synthesis of polythiophene-based sensors [14] and more recently for the control of the intramolecular photoinduced electron transfer in crown ether bridged oligothiophenes. [15] In this context, we now report on the surface immobilization by double fixation on gold surface of a dithiol quaterthiophene 1-SH derivatized with a polyether loop (Scheme 1). In recent years we have extensively studied the structural conditions and synthetic approaches allowing the horizontal double fixation of conjugated oligothiohenes as monolayers on gold surface. [16] After an analysis of the cation complexation properties of the related acetylprotected dithiol molecule 1 in solution by UV-Vis spectroscopy and cyclic voltammetry, the preparation of monolayers by double fixation of the oligothiophene chain on gold surface will be described, the structure properties of these monolayers will be investigated using cyclic voltammetry, ellipsometry, water contact angle measurement, XPS and their electrical properties will be assessed by contacting the monolayer with a conducting eutectic GaIn drop.Finally preliminary results on the cation binding properties of the monolayer and investigations on the use of the immobilized molecule as a switchable molecular junction will be presented and possible transport mechanisms will be discussed. Scheme 1Compound 1 has been synthesized by deprotection/functionalization of the appropriately protected thiolate groups according to the already published method. [16b] The detailed synthesis of this molecule and of some parent compounds will be reported elsewhere. [17] The identity and purity of compound 1 were established by 1 H and 13 C NMR spectrometry and HR mass spectrometry giving satisfactory results (see Supporting Information). Dithiol 1-SH was prepared by reduction of the thioester groups of 1 using DIBAl-H. Monolayers were Accepted to 3 elabo...