Triplet Diradical‐Cation Salts Consisting of the Phenothiazine Radical Cation and a Nitronyl Nitroxide

Abstract

The spin–spin and magnetic properties of two (nitronyl nitroxide)‐(di‐p‐anisylamine‐phenothiazine) diradical cation salts, (DAA‐PTZ)+‐NN⋅MBr4− (M=Ga, Fe), have been investigated. These diradical‐cation species were prepared by the cross‐coupling of iodophenothiazine DAA‐PTZ‐I with NN‐AuPPh3 followed by oxidation with the thianthrenium radical cation (TA+⋅MBr4−). These salts were found to be highly stable under aerobic conditions. For the GaBr4 salt, large ferromagnetic intramolecular and small antiferromagnetic intermolecular interactions (J1/kB=+320 K and J2/kB=−2 K, respectively) were observed. The magnetic property of the Fe3+ salt was analyzed by using a six‐spin model assuming identical intramolecular exchange interaction (J3/kB=+320 K) and the other exchange interactions (J4/kB=−7 K and J5/kB=−4 K). A significant color change was observed in the UV/Vis/NIR absorption spectra upon electrochemical oxidation of the doublet DAA‐PTZ‐NN to the triplet (DAA‐PTZ)+‐NN.

Syntheses and Properties of (Nitronyl nitroxide)‐substituted Tri‐phenylamine ortho‐Bridged by Two Oxygen and Sulfur Atoms

“…A broad signal due to the Δ M s=±1 transition was observed and a spin‐forbidden signal (Δ M s=±2) appeared at a g =4 region. The observed EPR signal in the g =2 region was similar to those of the stable NN ‐substituted radical cation species [8b,d] . DFT‐calculations (UB3LYP/6‐31**) estimated ferromagnetic interaction with J / k B =+995 K between a NN and DOTT + spins (Figure 5b, Table S3) [14]…”

Dithienopyrrole Derivatives with Nitronyl Nitroxide Radicals and Their Oxidation to Cationic High‐Spin Molecules

“…[4a,b, 5] Thus, the mixeds table radicalw ith radical-cation molecules were provided for high-spin triplet ground state molecules. [1d, 6] As eries of nitronyl nitroxide (NN) substituted triarylamine (TAA-NN), [7] fused arylamine (FTAA-NN), [8] pyrazine (NNDPP), [9] thianthrene (TA-NN) [10] phenothiazine (PTZ-NN) [11] and pyrrole-based [2b] molecules and their radical-cationic forms were reported (FigureS1, Supporting Information( SI)), most of them afforded ground-state triplet diradicals upon one electron oxidation. In particular, 1-phenyl NN 4substituted-2,5-di(thiophen-2-yl)-1H-pyrrole derivatives (TPT-Ph-NN), [12] and NN-substituted conjugated oligomerso fd ithienyl-N-methylpyrrole with methoxys ubstituents at the inner b-position of thiophene rings type of molecules (DTP-P-NN), [13] were utilized for the synthesis of cationic high-spinm olecules.…”

Redox‐Induced Modulation of Exchange Interaction in a High‐Spin Ground‐State Diradical/Triradical System

“…In relation to these studies, we previously designed, synthesized, and isolated nitronyl nitroxide radical (NN . )‐substituted radical cationic systems, based on diphenyldihydrophenazine (DPP .+ ‐NN . ), trioxytriphenylamine (TOT .+ ‐NN .…”

“…), and phenothiazine (PTZ .+ ‐NN . ), which were stable diradical systems in the triplet ground states with strong exchange interactions (2 J / k B > +300 K) (Scheme ). These experimental results also suggested that a strong donor π‐conjugated system substituted with NN .…”

“…In relation to these studies, we previously designed, synthesized, and isolated nitronyl nitroxider adical( NNC)-substituted radicalc ationic systems, [12][13][14][15] based on diphenyldihydrophenazine (DPPC + -NNC), [12] trioxytriphenylamine (TOTC + -NNC), [13] and phenothiazine (PTZC + -NNC), [14] which were stable diradical systems in the triplet ground states with strong exchangei nterac-tions (2J/k B > + 300 K) (Scheme 2). These experimental results also suggested that as trong donor p-conjugated system substitutedw ith NNC moietiesc ould be stable, even in both neutral and one-electrono xidation states, which helped us to experimentally investigate their fundamentalm agnetic properties.…”