Vapochromic behaviour of a gold(i)–lead(ii) complex as a VOC sensor

Abstract

The reaction among [Au₂Ag₂(C₆F₅)₄(OEt₂)₂]_n, PbCl₂ and terpyridine leads to the polymeric complex [{Au(C₆F₅)₂}₂{Pb(terpy)}]_n (1). Its crystal structure reveals potential voids close to the lead centres large enough to hold different molecules. The availability of these free sites allows complex 1 to act as a VOC sensor. Thus, when 1 is exposed to different solvent vapours such as acetonitrile, toluene or THF, variations in its solid appearance and its photophysical properties are observed as a consequence of the formation of the new polymorphs [{Au(C₆F₅)₂}₂{Pb(terpy)(CH₃CN)₂}]_n (2), [{Au(C₆F₅)₂}₂{Pb(terpy)}]_n·Tol (3) and [{Au(C₆F₅)₂}₂{Pb(terpy)(THF)}]_n·THF (4). Each polymorph displays a different emission energy depending on its structure and the presence of metallophilic interactions. In addition, the reversible solvent molecule exchange allows the tuning of the luminescence emissions in the greenish yellow–red range. DFT and TD-DFT calculations were performed to explain the origin of the luminescence of all these complexes.