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

Abstract

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 the solid state. The infinite stacks are formed by alternatingly 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. Complexes obtained exhibit both phosphorescent and fluorescent bands, spanning a wide covering wide spectral range. Fine-tuning of emission by varying the excitation energy could produce white light