Micromechanical Redox Actuation by Self-Assembled Monolayers of Ferrocenylalkanethiolates: Evens Push More Than Odds

Abstract

Microcantilever transducers can be valuable tools for the investigation of physicochemical processes in organized molecular films. Gold-coated cantilevers are used here to investigate the electrochemomechanics of redox-active self-assembled monolayers (SAMs) of ferrocenylalkanethiolates (Fc(CH) S) of different alkyl chain lengths. A significant odd-even effect is observed in the surface stress and cantilever movement generated by the oxidation of the SAM-confined ferrocenes as the number of methylene units n in the SAM backbone is varied. We demonstrate that stronger alkyl chain-chain interactions are at the origin of the larger surface stresses generated by SAMs with an even versus odd n. The findings highlight the impact of subtle structural effects and weak van der Waals interactions on the mechanical actuation produced by redox reactions in self-assembled systems.

Molecular Origin of the Odd–Even Effect of Macroscopic Properties of n-Alkanethiolate Self-Assembled Monolayers: Bulk or Interface?

“…Organic self-assembled monolayers (SAMs) formed on semiconductor, metal or metal oxide surfaces are an integral component of molecular electronic devices, for electrical insulation, charge storage, and charge transport. − A recent series of investigations of the charge transport properties of large-area, solid-state tunnel junctions comprised of SAMs of the redox-active ferrocenyl­alkanethiolates (Fc­(CH 2 ) n S) , or insulating n -alkanethiolates (CH 3 (CH 2 ) n S) − have sparked renewed interest in the odd–even (or parity) effect, − which refers to the alternation of a material’s structure and/or property due to an odd or even number of repeat units in the molecule. Parity effects in solid condensed phases often arise from differences in the intermolecular interactions and molecular packing.…”

Crystal structure of bis(1,8-dibenzoyl-7-methoxynaphthalen-2-yl)terephthalate: Terephthalate phenylene moiety acts as bidentate hydrogen acceptor of bidirectional C-H···π non-classical hydrogen bonds

“…Weak interactions in the solid of organic molecular substances have acquired interests and the revaluation in the scientific area over the last two decades [1][2][3]. Indeed, weak interactions have been established as essential features in influencing the chemical, physical, and biological activity properties of materials [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], by determining their threedimensional single molecular structure and spatial organization of molecular assembly. A number of papers and reviews have been dedicated to the crystallographic and theoretical study and consequently the analysis of halogen interactions and nonclassical hydrogen bonds such as C-H•••X (X = Polar atom) and C-H•••π hydrogen bonds have drastically increased over recent years, emphasizing the applicability and usefulness of weak interactions to scientific disciplines [22][23][24][25][26][27][28][29][30].…”

Odd‐Even Effect on Luminescence Properties of Europium Aliphatic Dicarboxylate Complexes

“…[1,2] In addition, there are other intrinsic physico-chemical properties of the α,ω,-alkanedicarboxylic acids due to the oddeven effect, which is quite well established in the literature. [3][4][5] This effect plays an important role in the regular variations of different properties of compounds: melting points, [3,5,6] solubility, [3] nanocalorimetry, [7] electrochemical, [8,9] the emulsifying ability of some surfactants [9] or structural selfassembling. [8,[10][11][12] It is noteworthy that the odd-even effect arises from a difference in the packing mode between odd-odd or even-even carbon members of a given homologous series.…”

“…[3][4][5] This effect plays an important role in the regular variations of different properties of compounds: melting points, [3,5,6] solubility, [3] nanocalorimetry, [7] electrochemical, [8,9] the emulsifying ability of some surfactants [9] or structural selfassembling. [8,[10][11][12] It is noteworthy that the odd-even effect arises from a difference in the packing mode between odd-odd or even-even carbon members of a given homologous series. [4][5][6]13] According to the "parallelogram-trapezoid model" proposed by Thalladi et al, [3] the even carbon members are arranged in such a way that the repulsive interactions between chains are decreased, leading to a more stable packing pattern.…”

“…[5] The odd-even effect has been used in studies of selfassembled monolayers (SAMs) and fully controls the ability of molecules to form highly ordered structures such as the effect in molecular self-assembled packing. [8,11,12,14] This zigzag conformation [2] plays a key role in the structural organization of SAMs based on carboxylic acid structures, [4,15] which present a potential for molecular electronic applications.…”