Emissive Mononuclear Cu(I) Triphenylphosphine Complexes with Functionalized 6-tert-Butoxycarbonyl-2,2'-bipyridine

Two new emissive mononuclear copper(I) triphenylphosphine complexes with functionalized 6-tert- butoxycarbonyl-2,2'-bipyridine chelating ligands were prepared and characterized. Each Cu(I) cation has a markedly distorted P₂N₂ tetrahedral array with two different Cu—N bond distances, due to the addition of the bulky tert-butoxycarbonyl group at the 6-position of the 2,2'-bipyridyl ring. A weak low-energy broad absorption band appears at 330—500 nm in their CH₂Cl₂ solutions, which is influenced by the methylation of the 2,2'-bipyridyl ring. At room temperature, the photoluminescence can be clearly observed both in degassed CH₂Cl₂ solution and in the solid state, because of the introduction of the bulky tert-butoxycarbonyl substituent, and the emission properties are remarkably affected by both the methylation and the alkoxycarbonyl variation of the 2,2'-bipyridyl ring. It is shown that the introduction of the bulky tert-butoxycarbonyl group is favorable for improving the emission properties of the 6-alkoxycarbonyl-2,2'-bipyridine-based cuprous complexes.