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Large organic molecules doted of complex architectures have attracted an increasing interest during the last decade due to their important applications as sensors and in the fields of adhesion, catalysis, molecular recognition, optoelectronics and lithography1. When deposited on surfaces, the molecules may self-organize into well-ordered structures over the entire substrate. In order to define suitable molecular architectures, fundamental studies on self-organized molecular overlayers have to be carried out in order to understand the steering mechanisms of 2D self-arrangement, as well as intermolecular and molecules-metal interactions. In this paper, organic molecules, namely, the 4-tert-butylcalix[4]arenes2, deposited on Au(110) will be discussed. This study has been carried out in ultra-high-vacuum (UHV) using Scanning Tunneling Microscopy (STM) and Low Energy Electron Diffraction (LEED). This molecule, formed by four phenol rings with a tert-butyl group attached in para-position, offers a high flexibility and, as a consequence, various conformational shapes. At room temperature, perfect self-organized overlayers on Au(110) are observed. Each molecular unit can be unambiguously identified by STM as well as the conformer and the relative position of each molecule with respect to the others. The LEED and STM analyses concluded that the molecules self-organize into the troughs of the (1x2) missing row of the substrate. This 2D arrangement is steered by the hydrogen bonding of the –C-(CH3)3 groups between neighboring molecules. In this system, the intermolecular interactions govern the orientation, conformation and the two-dimensional organization of these molecules at the metal surface although the molecule-metal interaction is so strong that the original (1x2) reconstruction is lifted to be replaced by a (1x3) missing row reconstruction. These results are of importance for interfacial supramolecular assemblies since such a molecular network could be used as host to grow smaller organic molecules or inorganic materials. |