Determining the site of reduction of 4-NO2-2,2′-bipyridine and [Pt(4-NO2-2,2′-bipyridine)Cl2]

Abstract

In situ UV/Vis and EPR spectroelectrochemistry experiments show that the unpaired electron in [4-NO₂-bpy]¹⁻ sits in an orbital which is based on the 4-NO₂-py moiety and not spread over both py rings. The unpaired electron in [Pt(4-NO₂-bpy)Cl₂]¹⁻ is based on the 4-NO₂-bpy ligand with some [bpy]¹⁻ character. Labelling the NO₂ group of 4-NO₂-bpy with ¹⁵N revealed that the larger coupling constant in the EPR spectrum of [4-NO₂-bpy]¹⁻ can be assigned to the N atom of the NO₂ group. This coupling constant is significantly smaller in the EPR spectrum of [Pt(4-NO₂-bpy)Cl₂]¹⁻.