Azido-Functionalized Aromatic Phosphonate Esters in ^RPOSS-Cage-Supported Lanthanide Ion (Ln = La, Nd, Dy, Er)...

Within this work, a modified preparation of diethyl 4-azidobenzylphosphonate (L1) is presented and the family of 4- or 4'-azido-substituted aromatic phosphonate esters is increased by three new ligand platforms: diisopropyl 4-azidobenzylphosphonate (L2), diisopropyl ((4'-azido-[1,1'-biphenyl]-4-yl)methyl)phosphonate (L3), and diisopropyl 4-azido-2,3,5,6-tetrafluorobenzylphosphonate (L4), which exhibit an anomalous splitting of the N₃ stretching vibrations. Subsequent coordination to the in situ generated ^RPOSS (polyhedral oligomeric silsesquioxane)-cage-supported lanthanide precursors [(Ln{^RPOSS})₂(THF)] (P1-P6) (Ln = La, Nd, Dy, Er; R = iBu, Ph; m = 0, 1) yields complexes of the general formula [Ln{^RPOSS}(L1-L4)(S1)(THF)] (1-30) (n = 2, 3; x = 0, 1; m = 0-2) retaining the azide unit for future semiconductor surface immobilization. Because the latter compounds are mostly oils or viscous waxes, preliminary solution-state structure elucidations via DOSY-ECC-MW estimations have been carried out which are in accordance with ¹H NMR integral ratios as well as solid-state structures, where available. Moreover, the optical properties of the Nd, Dy, and Er derivatives of complexes 1-30 are examined in the visible and NIR spectral regions, where applicable.