Au(I) and Ag(I) formamidinate tetranuclear complexes and coordination polymers: Synthesis, structures and luminescent properties

Reactions of AuCIS(CH3)(2) and Ag(I) salts (AgSCN, AgOAc and AgSbF6) with the lithiated formamidines afforded the tetranuclear complexes [Au-4(4-pyf)(4)]center dot 4CH(3)OH [4-Hpyf = N,N'-bis(pyridine-4-yl)formamidine], 1, [Au-4(pmf)(4)] [Hpmf = N,N'-bis(pyrimidine-2-yl)formamidine], 2, and [Ag-4(pmf)(4)], 3, and the coordination polymers [Ag-2(OAc)(4-pyf)](n), 4, and {[Ag-2(4-pyf)(2)]center dot THF}(n), 5, which have been structurally characterized by X-ray crystallography. The intramolecular Au center dot center dot center dot Au separations in 1 and 2 are in the range 2.8832(2)-3.3338(10) angstrom and the Ag center dot center dot center dot Ag separations in 3-5 are 2.7927(3)-2.9819(19) angstrom, indicating the existence of aurophilicity and argentophilicity, respectively. Complex 3 is a unique tetranuclear complex of the type Ag-4(form)(4) in which "form" represents the formamidinate ligands. The short lifetimes of 1.06-49.15 ns for 1-5 indicate that the emissions belong to fluorescence. Moreover, complex 4 emits white luminescence in the solid-state and the CIE coordinate appears at (0.30, 0.38), which represents the first single-emitting component white phosphor in the class of formamidinate coordination polymers.