Solution versus solid-state dual emission of the Au(i)-alkynyl diphosphine complexes via modification of polyaromatic spacers†
Single molecule luminophores capable of multiple emissions are essential for the development of new materials with unconventional photophysical behavior. In this work, a family of diphosphine ligands PPh2–PAH–PPh2 with variable polyaromatic hydrocarbon (PAH) spacers (PAH = 9,10-anthracene L1, 1,4-naphthalene L2, 2,6-naphthalene L3, and their diethynyl congeners L4–L6) were employed to prepare gold(I) complexes (RC2Au)PPh2–PAH–PPh2(AuC2R) (1–22), containing a selection of alkynyl groups. Investigation of their optical properties indicates that compounds with anthracene-based diphosphines (1–4 and 13–16) display only 1IL (ππ*) fluorescence with Φem up to 93%. The naphthalene and diethynyl-naphthalene diphosphine complexes (5–12 and 17–22), however, demonstrate panchromatic emission in the solid state and in solution featuring well-separated low and high energy signals, which originate from 1IL (ππ*) and 3IL (ππ*) transitions along with certain contribution from metal to ligand and ligand to ligand charge transfers.