Cooperativity in luminescent heterobimetallic diphosphine-β-diketiminate complexes

Abstract

The bis(phosphine)-functionalized β-diketiminate ligand [HC{(CH₃)C}₂{(o-[P(C₆H₅)₂]₂C₆H₄)N}₂]⁻ (PNac) was used for the synthesis of luminescent closed-shell bimetallic complexes. The PNNP pocket combining both soft and hard donor sites can act as an orthogonal ligand scaffold to selectively coordinate two different metal ions. Deprotonation and subsequent salt elimination with [AuCl(tht)] (tht = tetrahydrothiophene) or AgI yielded the mononuclear complexes [PNacAu] (1) or [PNacAg] (2), respectively. The Au^I ion is linearly coordinated by the two phosphines, forming a 12-membered metalla-macrocycle with an empty β-diketiminate pocket available for complexation of hard d¹⁰ metal ions (Zn^II, Cd^II, and Hg^II). According to this synthetic protocol, a series of heterobimetallic complexes were isolated. The complexation of the second metal ion in close spatial proximity has led to drastic changes in the photophysical properties. For further studies and understanding, quantum chemical calculations were performed.