Electrochemical and spectral studies of auto-assembled arrays of calix[4]arenequinhydrone charge-transfer complex on indium–tin oxide (ITO) glass

Abstract

A sensing materiel based on calix[4]arene molecules is electrochemically deposited on ITO electrode coated. A brown film was electrodeposited at a potential Eimp = –1.00 V versus SCE in acetonitrile solvent, however in dichloromethane solvent, a bluish film auto-assembled on the ITO electrode coated at a potential Eimp = −0.65 V versus SCE. Both films are subsequently analyzed by cyclic voltammetry and UV–Vis spectroscopy. This investigation shows that in acetonitrile solvent, the charge-transfer complex, calix[4]arenequinhydrone was formed in electrolytic solution and it was not self-assembled on the ITO electrode. The related UV–Vis spectrum shows a single absorption band towards a wavelength about 350 nm. The optical behaviour of the blue film shows two absorption bands: the first one appears on the first absorption band of the acceptor at 305 nm and the second one in the visible range at 502 nm. The band situated in the visible range correspond to a well-defined charge-transfer band indicating the presence of the charge-transfer complex, the calix[4]arenequinhydrone.

Multimodal switching of a redox-active macrocycle

“…Hydroquinone and benzoquinone form a deep purple C-T complex by simple grinding (see Supplementary Figure 14; crystals of the complex are green). Calix[4]arenequinones 25 were also eventually found to form quinhydrone-type complexes possessing a broad electronic absorption characteristic of C-T in their electronic absorption spectra 26,27 . However, the physical properties of C-T interactions between phenols and hemiquinones have not been previously reported, and therefore we set about determining the origin of the observation in the series 2 compounds.…”

Nanomolecular singlet oxygen photosensitizers based on hemiquinonoid-resorcinarenes, the fuchsonarenes

“…It has been reported that calixarene and resorcinarene macrocycles, and other molecules containing both quinone and hydroquinone or hemiquinone/phenol groups undergo intramolecular charge transfer (C-T) interactions. 22,34,35 Thus, we speculate that reduction in electron density on phenol groups caused by their proximity to electron decient hemiquinones in the same molecule eliminates formation of phenoxyl radical in rccc-1[Ox 2 ] while two phenol groups of rctt-1[Ox 1 ] are sufficiently remote (see Fig. 3(a)) from its hemiquinone that reaction with singlet oxygen is permitted.…”

Self-Assembly of Partially Oxidized Pillar[5]arene into Fibrous Structures

“…The electrochemical behavior of these films on indium tin oxide electrodes was also investigated. 7 More recently, Ogoshi and co-workers have pushed the field forward using pillar[n]arenes, 8 a family of macrocyclic hosts (see Figure 1B) that was initially prepared in their laboratory and has attracted considerable attention in the last decade. Primarily working with pillar [6]arenes, they partially oxidized them to generate macrocycles containing both hydroquinone and benzoquinone units, which self-assemble into fibrous materials.…”

“…The same group has described the formation of calix–quinhydrone complexes, formed by the interactions of calixarenes containing quinone units with their reduced counterparts, giving rise to solvatochromic, self-organized films. The electrochemical behavior of these films on indium tin oxide electrodes was also investigated …”