Free radicals with large negative spin densities

Abstract

We have taken the nmr spectra of a series of nitronyl nitroxide radicals with aromatic substituent in order to measure the sign and magnitude of the hyperfine coupling constants and spin densities. These radicals are unusual in that the ortho and para positions of the aromatic rings are found to have negative spin densities. The spin density at the meta position is smaller and positive. A series of molecular orbital calculations were carried out in order to theoretically determine the spin distribution in these radicals. A second-order perturbation calculation was undertaken to analyze the mode of spin propagation from the nitronyl nitroxide ring to the aromatic ring. This calculation yielded a qualitative technique for predicting the sign and relative magnitude of the spin densities in radicals of this type. Hyperfine coupling constants of organic free radicals are generally measured by analysis of electron spin resonance spectra. This technique yields the magnitude (4)

Construction of Nitronyl Nitroxide‐Based 3d–4f Clusters: Structure and Magnetism

“…The radical ligand NIT3py was prepared according to previously described methods. [22] Elemental analyses for C, H, and N were carried out by using a PerkinElmer 240 elemental analyzer at the Institute of Elemental Organic Chemistry, Nankai University. Magnetic measurements were performed on a SQUID VSM magnetometer.…”

Two Novel Diamagnetic-metal Coordination Polymers of Nitronyl Nitroxide Radical Incorporating Isophthalate Bridges

“…2-(4¢-Pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (NIT4py) was prepared according to the literature method [38].…”

Magnetic Slow Relaxation in Cyclic TbIII‐Nitronyl Nitroxide Radical Complexes

“…The radical ligands NIT-3Py and NIT-4Py were prepared according to literature methods. [25] Physical Measurements: Elemental analyses (C, H, N) were carried out with a Perkin-Elmer 240 elemental analyzer. The infrared spectra were recorded from KBr pellets in the range 4000-400 cm X-Ray Crystallography: Diffraction intensity data were collected on a Rigaku Saturn CCD diffractometer for 1 at 113 K and Rigaku SCXmini diffractometer for 2 at room temperature employing graphite-monochromated Mo-K α radiation (λ = 0.71073 Å).…”