Photoluminescent hybrid alumina and titania gels linked to rare earth complexes and polymer units through coordination bonds

Series of alumina and titania hybrid gels are assembled with both RE3+ (RE = Eu, Tb) pyridine-3,5(4)-dicarboxylate complexes (3,5- for M1 and 3,4 for M2) and polymer unit (polyacrylic acid, PA) though coordination bonds. Here two pyridine dicarboxylate ligands behave as the molecular bridges both coordinated to RE3+ and aluminium or titanium gels with their active functional groups (pyridine N and COO–). Meanwhile, polymer unit and beta-diketonates (1,1,1-trifluoroacetylacetone (TFAA) and acetylacetone (AA)) are introduced through the coordination bonds to these gels and RE3+, respectively. Physical characterization reveals that all kinds of units can be assembled into the whole hybrid system to obtain the homogeneous gel. Photoluminescence property indicates that hybrid alumina gels are more favorable for the luminescence of RE3+ than hybrid titania gels, while different linkages (M1, M2) only have little influence on the luminescence of hybrid gels.