A Photophysical Interpretation of the Thermochromism of a Polyfluorene Derivative–Europium Complex

Abstract

The thermochromism of a polyfluorene derivative complexed with a europium ion was interpreted using the photophysical properties of the noncomplexed polymer and a low molecular mass model compound having the same structure of the complexed site in the polymer. To the naked eye, the thermochromism was characterized by a strong red at low temperatures (170− 260 K, due to Eu 3+ ion) and a blue color at higher ones (280−330 K, due to fluorene). Absorption and emission spectra, time-resolved measurements, and theoretical simulations showed that the polymer chain does not affect the europium photophysical properties, but the opposite occurred: the ion insertion precluded interchain aggregation, and the backbone emission did not vary with temperature variation, in the range of 170−330 K. To the best of our knowledge, this effect is reported for the first time and opened a new avenue for the design of nanothermometers, since the polymer can act as a "built-in standard", thus allowing the construction of much simpler devices.

Magnetic properties of a polyfluorene derivative containing complexed neodymium ions

“…Morphological effects on the packing of conjugated polymer chains have been addressed in a number of publications. 44,45,61,62 In the present case, the inter-chain stacking was evidenced by the classic behavior found in the photophysical behavior of conjugated polymers, which is a progressive red shift with concentration, going from diluted conditions to the solid, as it can be clearly shown in Figure S5 of Supporting Information. The red shift is so pronounced that the first peak at 370 nm completely disappears in concentrated conditions, whereas the one in the region centered at 390 nm attributed to the stacked chains is prominent in the whole spectra.…”

“…Also, the metallopolymer shows two glass transitions, one of which matches that of the pristine, noncomplexed material and is therefore qualitatively consistent with the relatively low‐complex content. The complex content, determined by TGA (oxide residue) gave a value of 21%, in a molar basis, meaning that for each 100 repeating unit is, 21 are complexed …”

“…This argument was also used to account for the magnetic results reported in a recent publication for similar systems, indicating that π stacking is a favorable factor for the enhancement of the magnetic properties. Morphological effects on the packing of conjugated polymer chains have been addressed in a number of publications …”

“…The complex content, determined by TGA (oxide residue) gave a value of 21%, in a molar basis, meaning that for each 100 repeating unit is, 21 are complexed. 42,44 Regarding the FTIR for LaPPS75 and its complexes, the main absorption bands appear at 1425 cm −1 and 1566 cm −1 , assigned to the ν(C C) and ν(C N) stretching vibrations, 45,46 respectively ( Fig. S3 in the Supporting Information).…”

Energy Transfer‐Assisted Whispering Gallery Mode Lasing in Conjugated Polymer/Europium Hybrid Microsphere Resonators

“…These results indicate that energy transfer from F8tpy to Eu 3 + takes place efficiently. [1,6,[31][32][33][34] To authenticate energy transfer takes place from F8tpy polymer to Eu 3 + ,e xcitation spectra of 1 and 3 were measured by monitoring PL at 404 nm for 1 and 612 nm for 3.A ss hown in Figure S1 a, absorption bands at 314 nm and 350 nm for 1 and 3, respectively,c orrespond well with their absorption spectra (Figure 2a). Furthermore, the PL spectrum of 1 overlapsw ell with the absorption spectrum of 3 (FigureS1b), indicating that energy transfer should takes place from polymer to Eu 3 + .T he energy transfer efficiency from polymert oE u 3 + ion is evaluated as 0.90, using the following equation, h DA = 1À(I DA /I D )w here I DA and I D are the PL intensity with and without energy acceptor,respectively.…”