Dynamic phase change and adsorption–desorption of 4-pyridyl terminated amphiphiles possessing an amide functionality at a Au(1 1 1) electrode as tracked by electrochemical measurements

Adsorption of N-4-pyridinyl-hexadecanamide (C15-CONH-Py) and N-pentadecyl-4-pyridinecarboxamide (C15-NHCO-Py) onto a Au(1 1 1) electrode was described as a function of electrode potential using the results of electrochemical measurements. The results were compared with the behavior of 4-pentadecylpyridine (C15-Py) described in previous reports. A simple molecular calculation also was used for the comparison. Experimentally, a Au(1 1 1) electrode was horizontally touched once or twice to the spread films of these compounds at a gas ∣ solution interface. Both C15-CONH-Py and C15-NHCO-Py tended to be desorbed at sufficiently negative potentials, but their desorption were not perfect, in contrast to C15-Py. Changes of adsorption states due to reorientation of the terminal pyridyl group occurred at less negative potentials. The presence of an amide functionality and its direction with respect to the 4-pyridyl group markedly affected the potential dependences of the molecular assembling structures. A great extent of hysteresis in the phase changes was observed for the films prepared by the double-touch procedure. The possible effect of the lateral interaction due to hydrogen bonding was discussed.