Five- and Six-Coordinated Silver(I) Complexes Formed by a Metallomacrocyclic Ligand with a “Au2N2” Donor Group: Observation of Pendulum and Linear Motions and Dual Phosphorescence

The six-coordinated silver­(I) complex [Au2Ag­(μ-(PPh2)2py)2­(OTf)2]­(OTf), 4 (py = pyridine, OTf = CF3SO3), and the five-coordinated silver­(I) complex [Au2Ag­(acetone)­(μ-(PPh2)2py)2]­(PF6)3, 6, were prepared by the reaction of the precursor complexes 1(OTf)2 and 1(PF6)2, in which 1 = [Au2(μ-(PPh2)2py)2]2+, with 1 equiv of Ag­(OTf) in dichloromethane and excess of Ag­(PF6) in a mixture of dichloromethane/acetone, respectively. Also, the five-coordinated silver­(I) complex [Au2Ag­(μ-(PPh2)2py)2(py)­(OTf)]­(OTf)2, 5, was obtained by the reaction of 4 with pyridine. The clusters 4–6 were characterized using multinuclear NMR spectroscopy and elemental microanalysis. The single-crystal X-ray diffraction analysis revealed the octahedral and distorted square pyramidal geometries around the silver­(I) centers in the crystal structures of 4 and 6, respectively; a dynamic structure was observed for cluster 5 due to pendulum motion of the Ag­(pyridine) moiety, which was anchored in the metallomacrocyclic unit [Au2(μ-(PPh2)2py)2]2+. Although the crystal structure of 6 did not display disorders for the silver atom and the acetone ligand similar to that observed for 5, the low-temperature NMR spectroscopies and calculations show a dynamic structure for cluster 6 due to linear motion of the Ag­(acetone) moiety. The reaction of the precursor complex 1(PO2F2)2 with 2 equiv of Ag­(PO2F2) yielded the tetranuclear Au2Ag2 cluster [Au2Ag2(PO2F2)2­(μ-(PPh2)2py)2]­(PO2F2)2, 7, with a planar-shaped {Au2Ag2} metal core in which alternating Au and Ag atoms occupy the tetragon vertices and showed a strong argentophillic interaction between the silver­(I) centers. All clusters 4–7 are emissive in the solid state, and the origins of their emissive excited states were determined using time-dependent density functional theory calculations. Cluster 7 showed a dual phosphorescence emission, which displays strong dependence of the contributions of each emissive component onto the excitation wavelength.