Quaternary metal thiophosphates containing
second-order Jahn–Teller distorted d10 Ag+ and lone-pair cations, Ag3Bi(PS4)2 (1), Ag7Sn(PS4)3 (2), and Ag7Pb(PS4)3 (3), were obtained by solid-state synthesis. The structural
frameworks of 2 and 3 feature an infinite
1-D interchiral double helix ∞1(Ag3P2S11),
which is rare in inorganic compounds. Compound 3 undergoes
a significant first-order structural phase transition from monoclinic
to hexagonal at ∼204 °C. This can be ascribed to the significant
mismatch in the expansion coefficients between Pb–S (Ag–S)
and P–S bonds evaluated by bond valence theory. The three compounds
are Ag+ ionic conductors, and Ag+ ion migration
pathways are proposed by calculating maps of low bond valence mismatch.
Moreover, the optical properties of the three compounds were studied,
and electronic structure calculations were performed. The combination
of second-order Jahn–Teller distorted d10 cation
and lone-pair cation provides a new strategy to explore new metal
thiophosphates with interesting structures and promising properties.