Highly homogeneous, transparent and luminescent SiO2 glassy layers containing a covalently bound tetraazacyclododecane-triacetic acid-Eu(III)-acetophenone complex

The preparation of sol-gel glasses is described wherein highly stable Eu(III) centres are anchored to the silica glass upon acidic hydrolysis and by using tetraethylorthosilicate (TEOS) as a silica source. The complex employed is Eu?1 and is obtained from bipartite ligand 1, which features a DO3A macrocycle as a hosting unit for the Eu(III) centre, a methoxy-acetophenone unit as an antenna chromophore, and an alkyl chain bearing one primary hydroxy group (DO3A is 1,4,7,10- tetraazacyclododecane-1,4,7-triacetic acid). Eu?1 is linked to the forming silica glass through the -OH groups and a uniform distribution of the luminescent centres is obtained, as indicated by results from secondary ion mass spectrometry in-depth profiling. The luminescent efficiency of the Eu(III) centres in the solid matrix is evaluated to be 10%, which is comparable to that of Eu?1 in water solution and of a convenient reference complex, Eu?2 (2 is a ligand featuring the same hosting and antenna functionalities of 1, wherein the -OH residue is replaced by an unreactive group, a benzoylmethyl residue). A discussion is given of the photophysical properties exhibited by the complexes in the film and in solution.