A nitroxide diradical containing a ferrocen-1,1 '-diyl-substituted 1,3-diazetidine-2,4-diimine coupler

作者：Bagryanskaya Irina; Fedin Matvey; Gorbunov Dmitry; Gritsan Nina^*; Gurskaya Larisa; Kazantsev Maxim; Polienko Yuliya; Stass Dmitri; Tretyakov Evgeny^*

来源：Tetrahedron Letters, 2017, 58(5): 478-481.

DOI：10.1016/j.tetlet.2016.12.068

• Diradical
• Nitroxide
• Ferrocenophane
• Aza-Wittig reaction
• 1,3-Diazetidine

An Aza-Wittig reaction of 1,1'-bis(triphenylphosphoranylidenamino)-ferrocene with 3-isocyanato-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrol-1-oxyl and subsequent intramolecular [2+2]-cycloaddition of the bis(carbodiimide) intermediate was used for the synthesis of a 1,3-diazetidine-2,4-diimine moiety bearing two radical groups and bridging the cyclopentadienyl (Cp) rings. According to single-crystal X-ray data, the planar 2,4-diimino-1,3-diazetidine moiety adopts a perpendicular orientation with respect to the eclipsed Cp rings. One of the radical groups lies almost within the plane of the four-membered 1,3-diazetidine ring, while the other has a conformationally preferred orientation with dihedral angles +/- 62.3 degrees. The two Cp rings are constricted by the 1,3-diazetidine-2,4-diimine moiety so that the angle between their planes is 11.0 degrees. The synthesized diradical contains ferrocene and nitroxide redox signaling units that can be oxidized step-by-step at E-1/2 = 0.26 and 0.48 V (vs Fc/Fc(+)), respectively. Electron spin resonance spectroscopy revealed a moderate exchange interaction (vertical bar J vertical bar similar to a(N)) between the two nitroxide radical moieties and the following values of zero-field splitting parameters: vertical bar D vertical bar = 3.5 mT and E/D = 0 were obtained. These data were in agreement with density functional theory calculations. The newly developed approach to multispin systems may be interesting for the construction of weakly coupled rigid polyradicals for quantum technologies, the molecular design of magnets, and the creation of ferrocene-based electron-paramagnetic-resonance-active chemical sensors.

• 出版日期2017-2-1