Abstract:
We report p-conjugated polymer–Eu3+ ion complexes as new potential luminescent thermo-sensitive
molecular probes. Carboxylic acid functionalized segmented p-conjugated polymers having
oligophenylenevinylene (OPV) chromophores in the poly(ethyleneoxide) or polymethylene backbones
were custom designed, synthesized and utilized as efficient photosensitizers for Eu3+ ions. These pconjugated
polymer–Eu3+ ion complexes were found to be thermo-sensitive and behaved as reversible
‘turn-on’ or ‘turn-off’ luminescent switches in solution and in solid state. Luminescent decay studies
revealed that the red-emission from the Eu3+ ion excited state was highly sensitive to temperature
which drove the functioning of optical switches. The decay rate constants followed a typical Arrhenius
trend over a wide temperature range having similar activation energies. Both the nature as well as
length of the segmented polymer chain that tied the OPV optical chromophores in the backbone
determine the temperature range of the luminescent on–off process. The emission characteristics of the
oligomer–Eu3+ ion complex were found to be non-thermosensitive which emphasized the need for the
segmented p-conjugated polymer ligand structure for the probes based on Eu3+ ion complexes. The
present strategy opens up new concept and molecular design principles for p-conjugated polymer–
lanthanide ion complexes as potential candidates for temperature sensitive luminescent molecular probes.
