Room-temperature phosphorescence and dual-emission behavior of simple biphenyl derivatives unlocked by intermolecular interactions with cyclic silver pyrazolate†

The complexation of 4,4′-halogen-substituted biphenyls (BPs) with a trinuclear silver(I) 3,5-bis(trifluoromethyl)pyrazolate adduct ([AgL]₃) is observed in the solution and solid states. Infinite stacks are formed by alternating BPs and [AgL]₃ molecules via multiple metal–π interactions in a crystal. Encapsulation of the biphenyl derivatives between the [AgL]₃ units allows room-temperature phosphorescence in the solid state. Furthermore, the intercalation of BPs results in the formation of planar geometry, which allows the reduction of non-radiative relaxation and enhances luminescence due to the planar geometry of the excited states. Another crucial factor in efficient light emission is the asymmetry of the intermolecular complexes. The obtained complexes exhibited both phosphorescence and fluorescence bands spanning a wide spectral range. Furthermore, fine-tuning of emissions by varying excitation energy could produce white light.