Oxidation of Electron Donor-Substituted Verdazyls: Building Blocks for Molecular Switches

Abstract

Species that can undergo changes in electronic configuration as a result of an external stimulus such as pH or solvent polarity can play an important role in sensors, conducting polymers, and molecular switches. One way to achieve such structures is to couple two redox-active fragments, where the redox activity of one of them is strongly dependent upon environment. We report on two new verdazyls, one subsituted with a di-tert-butyl phenol group and the other with a dimethylaminophenyl group, that have the potential for such behavior upon oxidation. Oxidation of both verdazyls with copper(II) triflate in acetonitrile gives diamagnetic verdazylium ions characterized by NMR and UV-vis spectroscopies. Deprotonation of the phenol-verdazylium results in electron transfer and a switch from a singlet state to a paramagnetic triplet diradical identified by electron spin resonance. The dimethylaminoverdazylium 9 has a diamagnetic ground state, in line with predictions from simple empirical methods and supported by density functional theory calculations. These results indicate that verdazyls may complement nitroxides as spin carriers in the design of organic molecular electronics.

Suzuki–Miyaura Coupling of Verdazyl Radicals

“…We are particularly interested in the development of verdazyl‐containing conducting materials, in which the verdazyl spin interacts with the conducting “backbone”. Previous results show that verdazyls interact ferromagnetically with the spins at the 3‐position, and, thus, the introduction of further conjugated substituents at this position may be a useful way to synthesize new organic conductors and spintronic materials. Palladium‐catalyzed coupling reactions are particularly useful in this regard, as they use mild reaction conditions and are tolerant of numerous functional groups.…”

The syntheses, structures and spectroelectrochemical properties of 6-oxo-verdazyl derivatives bearing surface anchoring groups

“…S8, ESI †). 56,57 For these compounds, a 25-line pattern is predicted (Fig. 9), although in the experimental data line broadening reduces the number of observed peaks to 19.…”

Spectroscopic and thermodynamic characterization of a cobalt-verdazyl valence tautomeric system. influence of crystal structure, solvent and counterion

“…Other spectral measurements also hint at the complexity of the electronic structure of this species. Based on the analysis of the solution IR for [Co(dipyvd) 2 ] 2+ [BAr F 29 suggesting that in solution, or in the environment provided by the [BAr F 4 ] − counterions, the high spin form of [Co(dipyvd) 2 ] 2+ has some degree of positive charge on the verdazyl ligands. It is possible that this reflects contributions to the electronic structure of this system where the metal ion is formally d 8 Co (I).…”