Structural features and electronic properties of a cupric complex with redox active 1-(2-pyridylazo)-2-phenanthrol (papl)

We report the structural properties and electronic structure of a neutral homoleptic copper(II) complex bearing the anion of 1-(2-pyridylazo)-2-phenanthrol (papl). In the solid state the complex is disordered and this presents itself as a nearly equal mixture of five and six coordinate copper ions with the ligand bound in two different configurations, with one of the terminal pyridine rings uncoordinated in the case of the five coordinate ion, which also features a very short Cu–Nazo coordinate bond. The six coordinate complex features a Jahn–Teller elongated octahedron with one of the ligands coordinated in a typical fashion with coordinate bond distances typical of other divalent ion–papl complexes while the distances to the other donor atoms are much longer.

Graphical abstractWe present the structure and properties of a cupric complex with the redox-active ligand 1-(2-pyridylazo)-2-phenanthrol (papl). The complex features a disordered coordination geometry, either five or six-coordinate copper in a ratio of 53:47 with the minor component being five-coordinate. The six-coordinate geometry features the expected Jahn–Teller elongated axis and in the five-coordinate complex one equivalent of papl binds through a different azo N donor atom than is typical and the terminal pyridine ring is not coordinated. This is the first instance of this coordination mode for the papl ligand. The electronic and magnetic properties of the complex are as anticipated.Figure optionsDownload full-size imageDownload as PowerPoint slide