Forced proximity of nitroxide groups in pincer compounds with a xanthene spacer

Exploiting exciton coupling of ligand radical intervalence charge transfer transitions to tune NIR absorption

“…Both the weak intensity and position suggest that the zero-field splitting (ZFS) parameters are small. 35 The signal at ca. g = 2 contains two contributions.…”

Galvinoxyl-inspired dinitronyl nitroxide: structural, magnetic, and theoretical studies

“…1b. However, since both nitrones and nitroxides have an N–O length of about 1.3 Å, 16,19,37,48–85 the bond length between the N and neighbouring sp 2 carbon atoms is important to determine the electron state of the N–O site. In fact, there is a difference in the N–C sp 2 length; the average lengths for nitrones are 1.31 Å (N–O: 1.29 Å), 48–53 those for aryl tert -butyl nitroxides are 1.43 Å (N–O: 1.29 Å), 16,19,37,45,54–71 and those for 10-oxy-9(10 H )acridines are 1.41 Å (N–O: 1.29 Å).…”

“…However, since both nitrones and nitroxides have an N-O length of about 1.3 Å, 16,19,37, the bond length between the N and neighbouring sp 2 carbon atoms is important to determine the electron state of the N-O site. In fact, there is a difference in the N-C sp 2 length; the average lengths for nitrones are 1.31 Å (N-O: 1.29 Å), [48][49][50][51][52][53] those for aryl tert-butyl nitroxides are 1.43 Å (N-O: 1.29 Å), 16,19,37,45,[54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71] and those for 10-oxy-9(10H)acridines are 1.41 Å (N-O: 1.29 Å). [72][73][74][75] The compound 4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl, known as nitronyl nitroxide, has both nitrone and nitroxide moieties and thus an N-C sp 2 length of 1.34 Å (N-O: 1.28 Å), 41,54,55,[76][77][78][79][80][81][82]…”

Molecular S = 2 High-Spin, S = 0 Low-Spin and S = 0 ⇄ 2 Spin-Transition/-Crossover Nickel(II)-Bis(nitroxide) Coordination Compounds

“…We have utilized nitroxides o aminoxyls as a 2p spin source, because nitroxides are persistent enough when sterically bulky and/or π-conjugate substituents are attached at appropriate positions [38,39]. Ni troxides are highly accessible and chemically modifiable in many ways [40][41][42][43][44][45], and actu ally various spin label agents, such as TEMPO and PROXYL, are commercially available and derivatized by users [39,40,46,47]. The new nickel(II)-bis(nitroxide) coordination com pounds of the present work were synthesized in a rational manner, since the molecules are designable.…”