Mixed‐Valent Molecular Triple Deckers

Abstract

Two phenothiazine (PTZ) moieties were connected via naphthalene spacers to a central arene to result in stacked PTZ-arene-PTZ structure elements. Benzene and tetramethoxybenzene units served as central arenes mediating electronic communication between the two PTZ units. Based on cyclic voltammetry, UV/Vis-NIR absorption, EPR spectroscopy, and computational studies, the one-electron oxidized forms of the resulting compounds behave as class II organic mixed-valence species in which the unpaired electron is partially delocalized over both PTZ units. The barrier for intramolecular electron transfer depends on the nature of the central arene sandwiched between the two PTZ moieties. These are the first examples of rigid organic mixed-valent triple-decker compounds with possible electron-transfer pathways directly across a stacked structure, and they illustrate the potential of oligo-naphthalene building blocks for long-range electron transfer and a future molecular electronics technology.

Synthesis, Structures, and Properties of Neutral and Radical Cationic S,C,C-Bridged Triphenylamines

“…During our challenging program to develop the chemistry of para -unsubstituted triphenylamines, we focused on N -arylphenothiazine derivatives such as N -phenylphenothiazine (NPPTZ), , as these generate stable radical cations. − In the radical cationic state, the π-plane of the benzene ring at the N -position is almost perpendicular to that of the phenothiazine moiety and, as a result, the spin and positive charge are inherently localized on the phenothiazine moiety. Consequently, the electronic spin-structures of NPPTZ radical cations are different from those of triphenylamine radical cations.…”

Evaluation of Through‐Space Electronic Coupling in the Cofacially Aligned π‐Stacked Organic Mixed‐Valence System

“…This feature is clearly different from that of 2 • + in our previous work in which the spectrum was optically transparent below 10000 cm −1 30 . Nevertheless, this new absorption band is not strange in light of many precedents observed for the similar type of MVS with π – π stacked aromatic units, and was regarded as IVCT band a priori 14,24,27,31,57 . The spectroelectrochemical data were analyzed by multipeak Gaussian deconvolution (Figure 7(b)).…”

“…A number of representative structural motifs used for through‐space electronic interactions have been reported: cyclophanes, 13–17 1,2‐phenylene derivatives, 18–21 bicycloalkanes, 16,22,23 various kinds of sp 3 hydrocarbons, 24–29 1,8‐naphthalene, 30–33 and metal–organic frameworks 34,35 . The magnitudes of H 12 range from tens to thousands of wavenumbers depending on the bridge systems.…”