A series of phosphonate ester supported lanthanide complexes bearing functionalities for subsequent immobilisation on semi-conductor surfaces have been prepared. Six phosphonate ester ligands (L1-L6) with varying aromatic residues were synthesised....

The predominant reason for the damaging power of high-energy radiation is multiple ionization of a molecule, either direct or via the decay of highly excited intermediates, as e.g., in the case of X-ray irradiation. Consequently, the molecule is irreparably damaged by the subsequent fragmentation in a Coulomb explosion. In an aqueous environment, however, it has been observed that irradiated molecules may be saved from fragmentation presumably by charge and energy dissipation mechanisms. Here, we show that the protective effect of the environment sets in even earlier than hitherto expected, namely immediately after single inner-shell ionization. By combining coincidence measurements of the fragmentation of X-ray-irradiated microsolvated pyrimidine molecules with theoretical calculations, we identify direct intermolecular electronic decay as the protective mechanism, outrunning the usually dominant Auger decay. Our results demonstrate that such processes play a key role in charge delocalization and have to be considered in investigations and models on high-energy radiation damage in realistic environments.

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 = iBu, 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 solidstate 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.

This study examines the synthesis of two geminal bisphosphonate ester-supported Ln3+ complexes [Ln(L3)2(NO3)3] (Ln = Nd3+ (5), La3+ (6)) and optical properties of the neodymium(III) complex. These results are compared to known mono-phosphonate ester-based Nd3+ complexes [Nd(L1/L2)3X3]n (X = NO3-, n = 1; Cl-, n = 2) (1–4). The optical properties of Nd3+ compounds are determined by micro-photoluminescence (µ-PL) spectroscopy which reveals three characteristic metal-centered emission bands in the NIR region related to transitions from 4F3/2 excited state. Additionally, two emission bands from 4F5/2, 2H9/2 → 4IJ (J = 11/2, 13/2) transitions were observed. PL spectroscopy of equimolar complex solutions in dry dichloromethane (DCM) revealed remarkably higher emission intensity of the mono-phosphonate ester-based complexes in comparison to their bisphosphonate ester congener. The temperature-dependent PL measurements enable assignment of the emission lines of the 4F3/2 → 4I9/2 transition. Furthermore, low-temperature polarization-dependent measurements of the transitions from R1 and R2 Stark sublevel of 4F3/2 state to the 4I9/2 state for crystals of [Nd(L3)2(NO3)3] (5) are discussed.