Conformational behavior of naphtho-merocyanine dimers on Au(111)

Abstract

Thin film growth of molecules on substrates are governed by the convolution of inter-molecular forces and template-adsorbate interactions. Often the initial dimer formation plays a crucial role in the outcome of the molecular structure on the surface. Here, the behavior of naphtho-merocyanine on an Au(111) substrate was investigated using computational chemistry methods and Scanning Tunneling Microscopy. The experiments show a strong preference of dimer formation of the merocyanine molecules. Topographical measurements are used to identify two distinguished configurations, an elongated/oval dimer and a compact/rectangular dimer. With the addition of computational chemistry calculations including Density Functional Theory (DFT) and Molecular Mechanics calculations using the AMBER 3 force field, these two configurations of two specific merocyanine conformers, namely CTC and CTT, could be identified. Intermolecular binding energy calculations could be performed. This is a first step in understanding the possible island/thin film growth of naphtho-merocyanine and subsequently possible pathways toward the switching behavior of merocyanine and spiropyran on this substrate.