Circularly Polarized Luminescence of Silica-Grafted Europium Chiral Derivatives Prepared through a Sequential Functionalization

Abstract

We describe a new organic/inorganic material emitting circularly polarized luminescence (CPL). The hybrid system was obtained by the following steps: (i) preliminary grafting of the europium N,N-dibutylcarbamate [Eu(OCNBu)] complex onto silica, (ii) substitution of the residual carbamato groups with anionic 1,3-diphenyl-1,3-propanedionato ligands (dbm), and (iii) subsequent introduction of the neutral tridentate chiral ligand 2,6-bis(isopropyl-2-oxazolin-2-yl)pyridine (Pr-PyBox) in the metal coordination sphere. The solid material is stable to air and does not leach either the metal or the ligand. Samples of both enantiomers have been studied, showing mirror-image CPL spectra. The molecular compounds [Eu(dbm)-(S)-(Pr-PyBox)] and [Eu(dbm)-(R)-(Pr-PyBox)] were prepared for comparison purposes and their molecular structures studied by single-crystal X-ray diffraction, showing mononuclear derivatives with a coordination number of 9 for europium. Powder X-ray diffraction showed a single crystalline phase. Photoluminescence and CPL evidenced the presence of a single emitting species.

Circularly Polarized Luminescence from Inorganic Materials: Encapsulating Guest Lanthanide Oxides in Chiral Silica Hosts

“…Unfortunately, the development of solid‐state, chiral lanthanide‐based systems is quite slow so far. For example, there were only limited attempts made to incorporate lanthanide complexes into achiral solid hosts such as SiO 2 . Some examples on chiral lanthanide‐doped oxides have been recently reported.…”

Recent Advances in the Chemistry of Metal Carbamates

“…Recently, the study of the reactivity of homoleptic N,N-dialkylcarbamates with silica has been extended to Cu(II), Nb(III), Nb(V), Ta(V), Tb(III) and Eu(III) derivatives [131,153,362,363]. Silica grafting has been also realized with non-homoleptic complexes of group 4 and 5 metals, wherein the carbamato ligands are the most reactive ones [166,234,290].…”

“…For instance, noble metals such as Cu, Pd and Pt can be chemically or thermally reduced to give the respective silica-supported metal nanoparticles [361,362,365]. Another post-functionalization strategy entails the introduction of additional ligands by replacement of the residual carbamates, and for instance this method has been adopted to introduce chiral β-diketonates on lanthanide-grafted carbamates for chiroptical luminescence applications [153,363].…”

Near-infrared circularly polarized luminescence from chiral Yb(iii)-diketonates

“…The coordination sphere of such tris diketonate lanthanide complexes can be easily completed by using chiral neutral ancillary ligands, such as PyBox (pyridine bisoxazoline). [20][21][22] This strategy permits high tunability and modularity as allows one to tune independently the antenna (diketonate) and the chiral inducer (ancillary ligand). Therefore, we prepared both the enantiomers of Yb(TTA)3 i PrPyBox and Yb(TTA)3PhPyBox (scheme 1) and we studied their NIR-CPL properties.…”