Thomas Fabrice, Jarjayes Olivier, Duboc Carole, Philouze Christian, Saint-Aman Eric, Pierre Jean-Louis
Laboratoire de Chimie Biomimetique, LEDSS, UMR CNRS 5616, ICMG FR CNRS 2607, Universite J. Fourier, BP 53, 38041 Grenoble cedex 9, France.
Dalton Trans. 2004 Sep 7(17):2662-9. doi: 10.1039/b406009a. Epub 2004 Aug 5.
Ligands bearing two salicylidene imine moieties substituted in ortho and para positions by tert-butyl groups have been electrochemically oxidized into mono- and bis-phenoxyl radicals. The process involves an intramolecular proton coupled to electron transfer and affords a radical in which the oxygen atom is hydrogen-bonded to a protonated ammonium or iminium group. A weak intramolecular dipolar interaction exists between the two phenoxyl moieties in the bis-radical species. The copper(II) complexes of these ligands have been characterized and electrochemically oxidized. The mono-phenoxyl radical species are X-band EPR silent. The bis-phenoxyl radical species exhibits a (S= 3/2) ground state: it arises from a ferromagnetic exchange coupling between the two spins of the radicals and that of the copper(II) when the spacer is rigid enough; a flexible spacer such as ethylidene induces decomplexation of at least one phenoxyl group. Metal coordination is more efficient than hydrogen-bonding to enhance the chemical stability of the mono-phenoxyl radicals.
在邻位和对位被叔丁基取代的带有两个水杨醛亚胺部分的配体已被电化学氧化为单酚氧基和双酚氧基自由基。该过程涉及分子内质子耦合电子转移，并产生一种自由基，其中氧原子通过氢键与质子化的铵或亚胺鎓基团相连。在双自由基物种中，两个酚氧基部分之间存在弱的分子内偶极相互作用。这些配体的铜（II）配合物已被表征并进行了电化学氧化。单酚氧基自由基物种在X波段电子顺磁共振中无信号。双酚氧基自由基物种呈现出（S = 3/2）基态：当间隔基团足够刚性时，它源于自由基的两个自旋与铜（II）自旋之间的铁磁交换耦合；诸如亚乙基这样的柔性间隔基团会导致至少一个酚氧基解络合。金属配位比氢键更有效地增强了单酚氧基自由基的化学稳定性。
