Versatile Para‐Substituted Pyridine Lanthanide Coordination Complexes Allow Late Stage Tailoring of Complex Function

Abstract

A series of cationic and neutral p−Br and p−NO2 pyridine substituted Eu(III) and Gd(III) coordination complexes serve as versatile synthetic intermediates. Nucleophilic aromatic substitution occurs readily at the para position under mild conditions, allowing C−N and C−C bond forming reactions to take place, permitting the introduction of azide, amino and alkynyl substituents. For Eu(III) complexes, this approach allows late stage tuning of absorption and emission spectral properties, exemplified by the lowering of the energy of an LMCT transition accompanied by a reduction in the Eu−Npy bond length. Additionally, these complexes provide direct access to the corresponding Eu(II) analogues. With the Gd(III) series, the nature of the p‐substituent does not significantly change the EPR properties (linewidth, relaxation times), as required for their development as EPR spin probes that can be readily conjugated to biomolecules under mild conditions.

Structure and Reactivity of Polynuclear Divalent Lanthanide Disiloxanediolate Complexes

“…The X-band EPR spectra of 1-Eu 3 L 3 and 3-Eu 2 L 4 were collected at 10 and 298 K on ground solid samples (Figures S19 and S20). The spectrum of 1-Eu 3 L 3 at 10 K shows a single EPR feature, centered at g eff = 2.1, consistent with the presence of Eu­(II) ions . A more complex spectrum with strong features at g eff = 5.0 and 3.6 was recorded for the tetrametallic complex 3-Eu 2 L 4 at 10 K. Highly anisotropic g -values were already observed in complex EPR spectra of Eu 2+ -containing compounds .…”

Unlocking same‐sign CPL: solvent effects on spectral form and racemisation kinetics in nine‐coordinate chiral europium(III) complexes

“…This result is interesting for applications, as it allows the structure of the complex to be tailored more easily, e. g . by late‐stage functionalisation of the simpler, single arm pyridyl donor moiety [25] …”

Synthesis of bright water-soluble circularly polarized luminescence emitters as potential sensors

“…These results show the potential of our simple, easily accessible complexes for future sensing applications, and open the gates for the design of other simple CPL-based sensors. For example, longer excitation wavelengths can be achieved by substitution at the para -position of the pyridine ring, 17 and given the response of our complexes to manganese, sensing of other paramagnetic metals can be envisioned.…”