Novel erbium(iii) complexes with 2,6-dimethyl-3,5-heptanedione and different N,N-donor ligands for ormosil and PMMA matrices doping

Abstract

Three novel complexes, [Er(dmh)₃(bipy)], [Er(dmh)₃bath] and [Er(dmh)₃(5NO₂phen)], with 2,6-dimethyl-3,5-heptanedione (Hdmh) as the main sensitizer and either 2,2′-bipyridine (bipy), bathophenanthroline (bath) or 5-nitro-1,10-phenanthroline (5NO₂phen) as synergistic ligands were synthesized. Upon excitation at the maximum absorption of the ligands, the complexes show the characteristic near-infrared (NIR) luminescence of the Er³⁺ ions, due to efficient energy transfer from the ligands to the central Er³⁺ ion via the antenna effect. Single crystals were grown and their structures were determined showing different Er–N distances. The compound with shorter Er–N distances, [Er(dmh)₃(5NO₂phen)], was found to be the best light harvester and the best for transferring the energy to the lanthanide among the three studied compounds. Finally, the novel complexes have been assessed for their application in sol–gel and polymer-based waveguides and optical amplifiers through their inclusion into ormosil and polymethylmethacrylate matrices. The dispersion was successful in the bipy and 5NO₂phen cases, with the properties of the hybrid materials mimicking those of the pure complexes.