Lanthanide Loading of Luminescent Multi-Tridentate Polymers under Thermodynamic Control

This work illustrates the use of basic statistical mechanics for rationalizing the loading of linear multitridentate polymers with trivalent lanthanides, Ln­(III), and identifies the specific ionic sizes of europium and yttrium as promising candidates for the further design of organized heterometallic f–f′ materials. Using [Ln­(hfac)3] (hfac = hexafluoroacetylacetonate) as lanthanide carriers, the thermodynamically controlled formation of Wolf type-II lanthanidopolymers [{Ln­(hfac)3}m(L4)] is modeled with the help of two simple microscopic descriptors: (i) the intrinsic affinity of Ln­(III) for the tridentate binding sites fN3Ln and (ii) the intermetallic interactions ΔE1–2Ln,Ln operating between two occupied adjacent sites. Selective complexation (fN3La ≪ fN3Eu > fN3Y) modulated by anticooperative interactions (ΔE1–2La,La ≃ ΔE1–2Eu,Eu > ΔE1–2Y,Y ≈ 0) favors the fixation of Eu­(III) in semiorganized lanthanidopolymers [{Eu­(hfac)3}m(L4)] displaying exploitable light-downshifting.