Upconversion in a d–f [RuYb₃] Supramolecular Assembly

Abstract

We have prepared a hetero-tetrametallic assembly consisting of three ytterbium ions coordinated to a central [Ru­(bpm)3]2+ (bpm = 2,2′-bipyrimidine) motif. Irradiation into the absorption band of the peripheral ytterbium ions at 980 nm engenders emission of the 3MLCT state of the central [Ru­(bpm)3]2+ core at 636 nm, which represents the first example of f → d molecular upconversion (UC). Time-resolved measurements reveal a slow rise of the UC emission, which was modeled with a mathematical treatment of the observed kinetics according to a cooperative photosensitization mechanism using a virtual Yb centered doubly excited state followed by energy transfer to the Ru centered 1MLCT state.

Distributive Nd-to-Yb Energy Transfer within Pure [YbNdYb] Heterometallic Molecules

“…). In this respect, an optimal mode of implementing it is building up the antenna and the emissive center into discrete molecules. ,,− This is advantageous because chemical synthesis and design allow incorporating a large variety of organic sensitizers, tuning the distances between energy donors and acceptors, incorporating other functional properties, or tailoring the molecular properties for their processability. In this regard, probing Ln-to-Ln′ (Ln ≠ Ln′) ET within molecules is not an easy task because it requires the preparation of pure heterometallic species with the different Ln metal ions positioned selectively at specific locations of the molecular architecture. , Since the 4f valence electrons of lanthanides are strongly shielded by 5p and 5s electrons, they exhibit very similar reactivity; therefore, site-selective heterometallic Ln molecules are generally obtained via sequential methodologies that are very tedious. , These include (i) step-by-step deprotection/opening of coordination sites, (ii) covalent linkage of different preformed coordination complexes, − (iii) sequential activation and complexation of coordination sites, − or (iv) enantiomeric self-recognition and mutual binding of chiral components .…”

“…In this respect, an optimal mode of implementing it is building up the antenna and the emissive center into discrete molecules. 10 , 12 , 36 − 38 This is advantageous because chemical synthesis and design allow incorporating a large variety of organic sensitizers, tuning the distances between energy donors and acceptors, incorporating other functional properties, or tailoring the molecular properties for their processability. In this regard, probing Ln-to-Ln′ (Ln ≠ Ln′) ET within molecules is not an easy task because it requires the preparation of pure heterometallic species with the different Ln metal ions positioned selectively at specific locations of the molecular architecture.…”

Symmetry and Rigidity for Boosting Erbium‐Based Molecular Light‐Upconversion in Solution

“…\kern-\nulldelimiterspace} {k_{\rm{A}}^{1 \to 0} }}}$ in Scheme 1) due to a massive increase in non‐radiative relaxation processes produced by the considerable thermal vibrational bath found in molecules [24] . Consequently, the few dozens of lanthanide‐containing molecular complexes displaying detectable (linear) light upconversion under weak excitation intensity powers ( P ≤40 W ⋅ cm −2 ) [12,25–34] relied mainly on ETU [35–38] or on related multicenter Cooperative Upconversion (CU) processes [39–43] . However, the synthetic difficulties associated with the non‐statistical combination of sensitizers and activators within a single molecular entity for programming ETU or CU mechanisms, particularly when both partners are open‐shell labile lanthanide cations, [33,39–43] pave the way for the single‐center ESA to rise as the ultimate fully controlled upconversion process programmed at the molecular level in the absence of statistical doping [44–47] …”

Distributive Nd-to-Yb Energy Transfer within Pure [YbNdYb] Heterometallic Molecules

“…In this respect, an optimal mode of implementing it is building up the antenna and the emissive centre into discrete molecules. 10,12,[36][37][38] This is advantageous because chemical synthesis and design allows incorporating a large variety of organic sensitizers, tuning the distances between energy donors and acceptors, incorporating other functional properties or tailoring the molecular properties for their processability. In this regard, probing Ln-to-Ln' (Ln ≠ Ln') ET within molecules is not an easy task because it requires the preparation of pure heterometallic species with the different Ln metal ions positioned selectively at specific locations of the molecular architecture.…”