Coordination Polymers based on the Neutral Ditopic Ligand (C₆H₄PO(OCH₃)₂)₂ Involving some f‐Block Elements

Abstract

An improved synthesis using microwave heating affords (C6H4PO(OCH3)2)2 in excellent isolated yield (95 %). The ligand properties of this bisphosphonateester were explored towards hard metal centers M 2+ (M = Ca, UO2) and M 3+ (M = La, Ce, Sm, Eu) resulting in coordination polymers, for which the reduction of ionic size of the central metal atom resulted in lower‐dimensional structural motifs as opposed to higher dimensional networks obtained for the larger ions. All coordination polymers were characterized by single‐crystal X‐ray diffraction, IR spectroscopy, and combustion analysis. The ligand was furthermore characterized with multinuclear NMR spectroscopy.

Functionalised phosphonate ester supported lanthanide (Ln = La, Nd, Dy, Er) complexes

“…The 31 P-NMR shifts of L1-L6 are in-between 19.0 ppm (L6) and 24.4 ppm (L5) ( Table 2) and are located within the range of related compounds found in the literature. [7][8][9] Lanthanide complexes 1-32…”

“…Despite of the phosphonate esters L1-L6 being potential three-dentate chelate ligands, all obtained lanthanide complexes exhibit only a mono-dentate coordination by the oxygen atom of the P + -O − moieties like it is observed in related structures. [7][8][9] Except for the L4and L5-supported complexes 21 and 25, the 31 P-NMR signal of the free ligands experiences a 0.1-0.4 ppm shift to higher field upon complex formation with the lanthanum chloride precursors ( Table 2). This effect is even more pronounced upon com-plexation with the lanthanum nitrates causing a high-field shift of 1.1 ppm (1) and 1.3 ppm (9), respectively.…”

“…6 Our group has focussed on this topic during the last years preparing a variety of efficiently luminescent lanthanide based MOFs. [7][8][9] Moreover, different poly-fluoroaryl substituted mono- 10,11 and bis-phosphanes, 12 and phosphinic acids 13 with enhanced rigidity have been prepared and investigated in terms of reactivity and coordination behaviour. Now, to obtain distinct molecular lanthanide complexes with enhanced excited state lifetimes in the context of a future attachment to semiconductor surfaces, our research focusses on preparation of aryl-sub-stituted mono phosphonate ester ligands.…”

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

“…A similar trend can be derived for the corresponding M−O μ 2 -OSi distances, which decrease from 2.396(6) Å in [Nd{ Ph POSS}(THF) 2 ] 2 over 2.295(4) Å in 31 to 2.277(4) Å in 32, which is in accordance with the successively decreasing effective ionic radii of the lanthanide ions: Nd 3+ (98 pm) > Dy 3+ (91 pm) > Er 3+ (89 pm). 49 The considered OP−C angles experience a slight shortening from an average of 113.7 (11)°in the free phosphonate esters to an average of 111.6 (10)°in the complexed ligands. The shortest M−O−P angles with an average of 152.7(7)°are found in the monomeric complex [Er{ Ph POSS}(L1) 3 ] (8), while this angle decreases in the tetrameric compounds from 158.0(4)°i n the Dy 3+ species 31 to 157.5(3)°in the Er 3+ species 32.…”

“…In comparison to their carboxylic acid counterparts, the advantage of phosphonate esters arises from their lower vibrational frequencies, resulting in diminished nonemissive excited-state quenching and improved quantum yields . Our group has focused on these ligands in recent years, synthesizing several highly luminescent lanthanide-based MOFs − as well as mono- and dimeric lanthanide complexes showing interesting splitting features in their NIR emission spectra …”