Efficient near-UV photosensitization of the Tb(III) green luminescence by use of 2-hydroxyisophthalate ligands

The first examples of lanthanide complexes with a 2-hydroxyisophthalate ligand are reported; the blue-emitting ligand acts as a very efficient sensitizer of the Tb(III) green emissions and does so in the near-UV region

Insights into the nature of the hydrogen bonding of ^·Tyr₂₇₂ in apo-galactose oxidase

The synthesis and structure of an o-methylthio-phenol-imidazole, 2-(2′-(4′-tert-butyl-6′-methylsulfanyl)-hydroxyphenyl))-4,5-diphenyl-imidazole (MeSLH), is reported; X-ray crystallographic studies have shown that MeSLH involves an O–H···N+ hydrogen bond between the phenol and an imidazole nitrogen. MeSLH undergoes a reversible, one-electron, oxidation to form the radical cation [MeSLH]·+ the EPR spectrum of which is remarkably similar to that of ·Tyr272 in Cu-free, oxidized, apo-GO. Density Functional Theory calculations, have shown that the proton-transferred (R–O····H–N+) form of [MeSLH]·+ has a spin density distribution – with a substantial delocalization of the unpaired electron spin density onto the ortho sulfur atom – and EPR properties that are in good agreement with those of ·Tyr272 in Cu-free, oxidized, apo-GO whereas the non-proton-transferred (R–O·+–H···N) form does not. The results reported herein are a further demonstration of the influence of hydrogen bonding on the nature and properties of phenoxyl radicals and strongly suggest that the phenoxyl oxygen of ·Tyr272 in Cu-free, oxidized, apo-GO is involved in a O····H–O/N hydrogen bond