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 PPh 2 –PAH–PPh 2 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 (RC 2 Au)PPh 2 –PAH–PPh 2 (AuC 2 R) ( 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 1 IL (ππ*) fluorescence with Φ em 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 1 IL (ππ*) and 3 IL (ππ*) transitions along with certain contribution from metal to ligand and ligand to ligand charge transfers.