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

Abstract

New members of the Ln[Au(CN) 2 ] 3 ·3H 2 O and [nBu 4 N] 2 [Ln(NO 3 ) 4 Au(CN) 2 ] series Ln = Ce (CeAu 3 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 CeAu 3 and CeAu display characteristic Ce III -based emission at λ max = 393 nm (5d→ 2 F J ), however in CeAu 3 Au I -

Lanthanide Photoluminescence in Heterometallic Polycyanidometallate-Based Coordination Networks

“…In addition, they are photoluminescent in the visible range due to their metal-to-ligand charge transfer (MLCT) transition [27,28]. They were found to be attractive for the sensitization of lanthanide(3+) luminescence, which was precisely investigated for the family of classical three-dimensional [Ln III (H 2 O) 3 ][M I (CN) 2 ] 3 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy; M = Ag, Au) coordination polymers (Figure 1, Table 1) [55,56,57,58,59,60,61,62,63,64,65,66,67,68,69]. These compounds are composed of the alternately arranged Ln III and M I (M = Ag, Au) centres bonded through cyanide bridges (Figure 1a).…”

“…Moreover, the composition-dependent visible photo- luminescence was presented for the mixed trimetallic LaAgAu and TbAgAu compounds [62,63]. For Ce 3+ and Sm 3+ , the very weak energy transfer from 4d/5d to 4f metal centres was detected, resulting in the complex UV-Vis emission signal of the mixed Ln 3+ and [M I (CN) 2 ] − origins [66,67,68,69]. In the case of Sm 3+ , even the reverse Sm(III) to Au(I) energy transfer could be postulated [69].…”

“…The combination of dicyanidoaurates(I) with lanthanide(3+) ions in the non-aqueous solution hampered the crystallization of the 3D network, and gave cyanido-bridged ( n Bu 4 N) 2 [Ln III (NO 3 ) 4 ] [Au I (CN) 2 ] (Ln = Ce, Nd, Sm, Gd, Eu, Tb, Dy) zig-zag chains (Figure 2) [67,68,69,70]. For this coordination topology, unlike to the related 3D LnAu networks, there is no efficient energy transfer between [Au I (CN) 2 ] − and Ln III complexes, and both entities act as two separate emissive sources.…”

“…It causes the lack of aurophilic Au–Au interactions (Figure 2a), playing the presumably important role in the ET process within the 3D LnAu networks [67]. Therefore, taking advantage of the intrinsic properties of both luminescent 5d and 4f (Sm, Eu, Tb, Dy) metal complexes embedded in such cyanido-bridged chains, the multi-coloured composition-dependent emission, including the white light, was fruitfully achieved (Figure 2b) [67,68,69,70]. Moreover, the related trimetallic mixed 5d-4f-4f’ compounds enabled the adjustment of the emission colour to the very broad range of the visible spectrum between red colour characteristic of EuAu chains, green emission typical for TbAu chains, up to the deep violet detected for CeAu analogues, for which mainly the UV-violet Ce III -centred emission was found (Figure 2b) [68,69].…”

“…Therefore, taking advantage of the intrinsic properties of both luminescent 5d and 4f (Sm, Eu, Tb, Dy) metal complexes embedded in such cyanido-bridged chains, the multi-coloured composition-dependent emission, including the white light, was fruitfully achieved (Figure 2b) [67,68,69,70]. Moreover, the related trimetallic mixed 5d-4f-4f’ compounds enabled the adjustment of the emission colour to the very broad range of the visible spectrum between red colour characteristic of EuAu chains, green emission typical for TbAu chains, up to the deep violet detected for CeAu analogues, for which mainly the UV-violet Ce III -centred emission was found (Figure 2b) [68,69]. In addition, the selective excitation of the Au I - or Ln III -based emission transitions was also achievable, as exemplified by the multi-coloured photoluminescence of the mixed Ce 0.33 Eu 0.17 Tb 0.5 Au chains (Figure 2b) [69].…”