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 f_N3^Ln and (ii) the intermetallic interactions ΔE_1–2^Ln,Ln operating between two occupied adjacent sites. Selective complexation (f_N3^La ≪ f_N3^Eu > f_N3^Y) modulated by anticooperative interactions (ΔE_1–2^La,La ≃ ΔE_1–2^Eu,Eu > ΔE_1–2^Y,Y ≈ 0) favors the fixation of Eu(III) in semiorganized lanthanidopolymers [{Eu(hfac)₃}_m(L4)] displaying exploitable light-downshifting.

Metal loading of multi-terdentate receptors with [Eu(pbta) ₃ ] provides the first anti-cooperative factors large enough for programming metal alternation in lanthanidopolymers at room temperature.