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

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 N 3 stretching vibrations. Subsequent coordination to the in situ generated R POSS (polyhedral oligomeric silsesquioxane)-cage-supported lanthanide precursors [(Ln{ R POSS}) 2 (THF) m ] ( P1 - P6 ) (Ln = La, Nd, Dy, Er; R = i Bu, Ph; m = 0, 1) yields complexes of the general formula [Ln{ R POSS}( L1 - L4 ) n ( S1 ) x (THF) m ] ( 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 1 H 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.