Ce/Au(CN)₂^--Based Coordination Polymers Containing and Lacking Aurophilic Interactions

New members of the Ln[Au(CN)₂]₃·3H₂O and [nBu₄N]₂[Ln(NO₃)₄Au(CN)₂] series Ln = Ce (CeAu₃ and CeAu respectively) are reported herein where their synthesis, structure and photoluminescence properties are discussed. The first is a 3-D coordination polymer with aurophilic interactions of 3.35 Å and the latter is a 1-D coordination polymer that lacks them. At 293 K both CeAu₃ and CeAu display characteristic Ce^III-based emission at λ_max = 393 nm (5d→²F_J), however in CeAu₃ Au^I-based emission (λ_max = 410, ¹MLCT) dominates the spectrum. At 77 K however, the dominant emission is Au^I-based with characteristic emissions of λ_max = 430 nm (¹MLCT) and 490 nm (³MLCT). The key difference in the luminescence of these two materials can be rationalized in terms of their respective structures, through either the aurophilic network and lack thereof and/or the rigidity offered in the 3-D structure of CeAu₃.