Abstract
The interaction between the silver ion and the cyclic aromatic molecules, namely, the helicenes, is the subject of this paper. In fact, a silver complexation system based on quartz crystal microbalance (QCM) sensor with a functional film of helicenes has been designed and developed at four temperatures. The developed system, in which the sensor response reflects the adsorption of the hexahelicene and the heptahelicene, was able to control the complexed mass of silver for each concentration. Experimental outcomes indicated that the quartz crystal coated with heptahelicene is the adequate material for silver adsorption. Then, a theoretical study has been performed through two statistical physics models (SMPG and SMRG) in order to analyze the experimental adsorption isotherms of the two helicenes at the ionic scale. The SMRG model was developed using the real gas law and was satisfactorily applied for the microscopic investigation of the hexahelicene isotherms indicating that the lateral interactions between the adsorbates are responsible of the decrease of the adsorbed quantity at saturation. The interpretation of the two models’ parameters indicated that the adsorption of the two helicenes is an endothermic phenomenon. Interestingly, the heptahelicene is recommended for silver complexation because it shows the highest adsorption energies involving chemical bonds during the complexation process. The SMPG model and the SMRG model also allow prediction of three thermodynamic functions (configurational entropy, Gibbs free enthalpy, and internal energy) which govern the adsorption mechanism of silver on the two helicenes.
Highlights
The hexahelicene and the heptahelicene are interesting members of the carbohelicene family which provide a central cavity suitable for complexing cationic ions [1, 2]
The adsorption of silver onto helicene molecules is studied by the grand canonical ensemble in statistical physics, to find new microscopic interpretations
Through the experimental result discussion, it is discovered that the heptahelicene is the best complexing adsorbent of silver because it shows the highest adsorption capacities
Summary
The hexahelicene and the heptahelicene are interesting members of the carbohelicene family which provide a central cavity suitable for complexing cationic ions [1, 2]. These molecules are characterized by their helical geometry and their extraordinary electronic properties It is intriguing to check if these small molecules have the adequate adaptability to complex the cationic metals [13, 14]
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