Molecular Description of Grafted Supramolecular Assemblies on Gold Surfaces: Effect of Grafting Points and Chain Lengths

L Garnier and C Bonal and P Malfreyt, ACS OMEGA, 5, 16628-16634 (2020).

DOI: 10.1021/acsomega.0c01453

The association of 4 aminoazobenzene (4AA) with two different water- soluble hosts, beta-cyclodextrins (beta-CD) and calixarenesulfonates (CnS), was studied in heterogeneous conditions using molecular simulations. This situation is achieved by immobilization of macrocycles onto a gold Au(111) surface. Several factors that can influence the binding properties are investigated here through the chain length of alkylthiols spacer of the surfaceimmobilized host and the number of attachment points to the surface. A conformational change of beta-CD as a function of the chain length is evidenced upon grafting on the gold surface, whereas CnS does not show any changes. It is then possible to tune the thermodynamic properties of beta-CD by changing the grafted chain length and forming a larger hydrophobic region. The mechanisms of insertion of guests into the cavities are similar to those obtained in a homogeneous system. 4AA is included longitudinally in the beta-CD cavity, and it interacts rather with the sulfonate groups of the CnS located at the outer edge of the cavity.

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