Copper(I) and silver(I) complexes of 9,9-dimethyl-4,5-bis(di-tert-butylphosphino)xanthene: photophysical properties and structural perturbation under pressure

The heteroleptic complexes [Cu( t Bu-xantphos)(bpy)][PF 6 ] and [Ag( t Bu-xantphos)(bpy)][PF 6 ], where t Bu-xantphos = 9,9-dimethyl-4,5-bis(di- tert -butylphosphino)xanthene and bpy = 2,2'-bipyridine have been synthesized and their photophysical properties investigated. Single crystal X-ray diffraction studies of the compounds under ambient and increased pressure allow are presented; increase in pressure results in little structural perturbation. For the copper(I) complexes, the effects of changing the N^N ligand from bpy to 6-methyl-2,2'-bipyridine (6-Mebpy), 6-bromo-2,2'-bipyridine (6-Brbpy), and 4,4'-di( tert -butyl)-2,2'-bipyridine (4,4'- t Bu 2 bpy) were also investigated. Emissions from the copper(I) complexes are weak, both in solution and the solid state and this is attributed to vibrational quenching effects of the tert -butyl substituents of the t Bu-xantphos ligands