Energy transfer and excitation processes in thin films of rare-earth organic complexes for NIR emission

We have synthesized and studied the excitation-emission properties of three erbium-coordinating porphyrin-based complexes for solid state films with emission in the 1530-nm band. In two of these complexes the C-H groups of the organic part (ligand) have been substituted with C-F and/or C-Br ones in order to assess the role of the deactivation by the vibronic levels in the strong quenching of NIR emission. Time-resolved phosphorescence measurements have also been carried out in gadolinium analogues to verify the influence of substitution on the singlet-triplet intersystem crossing processes. The observed increase in the NIR emission is not consistent with the complete removal of quenching and the presence of other mechanisms for deactivation should be investigated.