Luminescence of the nitronyl nitroxide radical group in a spin-labelled pyrazolylquinoline

Terbium(III) and Yttrium(III) Complexes with Pyridine-Substituted Nitronyl Nitroxide Radical and Different β-Diketonate Ligands. Crystal Structures and Magnetic and Luminescence Properties

“…Several studies concerning visible luminescence of uncoordinated and coordinated nitroxides were reported 32,33,78,86−88 The electronic structure of nitronyl nitroxide radicals has been probed through luminescence spectroscopy, most recently in solution, and discussed in terms of molecular orbitals calculated with DFT theory. 40 In the following, we focus on the vibronic structure and its temperature variation observed for the title compounds. The luminescence spectra at variable temperature for 1, 2, 3, and 4 show an unusual decrease of the energy difference between luminescence maxima as the temperature increases.…”

“…29 Similar band maxima have been reported for uncoordinated NIT radicals in the solid state. 40 The maxima for uncoordinated NIT2Py radical are at somewhat different energy than when coordinated to Tb(III) ions. The maxima for 1 are shifted to 14 525 and 13 070 cm −1 at 80 K, differences of approximately 435 and 500 cm −1 , respectively.…”

Revisiting the Ullman's Radical Chemistry for Phthalocyanine Derivatives

“…[7] Condensationp roducts suffer from low solubility.C onsequently,t heir purificationa nd characterization are always ad ifficult task and the Ullman's synthesis is general-ly continued withoutf urtherp urification. Their lows olubility in methanol as well as the stabilization of the aldehyde function by resonance prevents the condensation with 6 in an appropriate manner.D espite these constraints, the Ullman radicals were introduced in numerous molecules like pyrene, [10] quinoline, [11] 1,2,4-triazole, [12] calixarene [13] or ferrocene [14] or even in the axial position of tetraphenylporphinatozinc(II) coordinated by p-pyridyl nitronyl nitroxide. In case of excess of oxidant [8] or if the solution is acidic, [2] nitronyln itroxides are converted spontaneously to imino nitroxide in an on-reversiblew ay (Way III), as described in Scheme 1.…”

“…[9] Although imino and nitronyl nitroxide free-radical derivatives are obtained satisfactorily with numerous substituents, the Ullman routes uffers from major drawbacks in the case of highly aromatic aldehydew hich requirem ulti-step synthesis. Their lows olubility in methanol as well as the stabilization of the aldehyde function by resonance prevents the condensation with 6 in an appropriate manner.D espite these constraints, the Ullman radicals were introduced in numerous molecules like pyrene, [10] quinoline, [11] 1,2,4-triazole, [12] calixarene [13] or ferrocene [14] or even in the axial position of tetraphenylporphinatozinc(II) coordinated by p-pyridyl nitronyl nitroxide. [15] Our interest in the phthalocyanine dyes as ap romising group of fluorophore derivatives with highq uantum yield, used in numerous applications( chemical sensor,s olarc ell, PDT, etc.…”

“…Their low solubility in methanol as well as the stabilization of the aldehyde function by resonance prevents the condensation with 6 in an appropriate manner. Despite these constraints, the Ullman radicals were introduced in numerous molecules like pyrene, quinoline, 1,2,4‐triazole, calixarene or ferrocene or even in the axial position of tetraphenylporphinatozinc(II) coordinated by p ‐pyridyl nitronyl nitroxide …”