TY - JOUR

T1 - A nitroxide diradical containing a ferrocen-1,1′-diyl-substituted 1,3-diazetidine-2,4-diimine coupler

AU - Bagryanskaya, Irina

AU - Fedin, Matvey

AU - Gorbunov, Dmitry

AU - Gritsan, Nina

AU - Gurskaya, Larisa

AU - Kazantsev, Maxim

AU - Polienko, Yuliya

AU - Stass, Dmitri

AU - Tretyakov, Evgeny

PY - 2017/2/1

Y1 - 2017/2/1

N2 - 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°. 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°. The synthesized diradical contains ferrocene and nitroxide redox signaling units that can be oxidized step-by-step at E1/2= 0.26 and 0.48 V (vs Fc/Fc+), respectively. Electron spin resonance spectroscopy revealed a moderate exchange interaction (|J| ∼ aN) between the two nitroxide radical moieties and the following values of zero-field splitting parameters: ∣D∣ = 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.

AB - 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°. 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°. The synthesized diradical contains ferrocene and nitroxide redox signaling units that can be oxidized step-by-step at E1/2= 0.26 and 0.48 V (vs Fc/Fc+), respectively. Electron spin resonance spectroscopy revealed a moderate exchange interaction (|J| ∼ aN) between the two nitroxide radical moieties and the following values of zero-field splitting parameters: ∣D∣ = 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.

KW - 1,3-Diazetidine

KW - Aza-Wittig reaction

KW - Diradical

KW - Ferrocenophane

KW - Nitroxide

KW - CRYSTAL-STRUCTURE

KW - CORRELATION-ENERGY

UR - http://www.scopus.com/inward/record.url?scp=85008465496&partnerID=8YFLogxK

U2 - 10.1016/j.tetlet.2016.12.068

DO - 10.1016/j.tetlet.2016.12.068

M3 - Article

AN - SCOPUS:85008465496

VL - 58

SP - 478

EP - 481

JO - Tetrahedron Letters

JF - Tetrahedron Letters

SN - 0040-4039

IS - 5

ER -