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Doctoral thesis
English

Rigidifying N-donor Scaffolds and its Consequence on Thermodynamics and Photophysics of Mononuclear Ln(III) Coordination Complexes

ContributorsNaseri, Soroush
Number of pages306
Imprimatur date2023
Defense date2023
Abstract

From the known case of 2,2ꞌ-bipyridine and its rigid counterpart, 1,10-phenantroline, it has been established that rigidification in polyaromatic didentate diimine ligands can increase the stability of d-metal complexes by an average of 1.4 log units. However, the extension towards terdentate terimine homologues adapted for the complexation of f-block cations with larger coordination numbers remains more restricted. Later on, Thummel, Hancock, and co-workers demonstrated that preorganization caused by reinforcing benzo groups in the backbone of polypyridyl-type ligands can boost the affinities of d- and f-block metal ions towards these ligands, regardless of the intrinsic affinity for pyridyl donors. Yet, the lack of a comprehensive study on the complexation of d- and f-block cations with rigidified terdentate terimine ligands is exasperating. In this work, hence, the rigidification of 2,6-bis(1-methyl-1H-benzo[d]imidazol-2-yl)pyridine L6 to give highly preorganized benzo[4',5']imidazo[1',2':1,2]pyrido[3,4-b]benzo[4,5]imidazo[1,2-h][1,7]naphthyridines (L1L4) offer a novel and rare opportunity for efficiently complexing trivalent lanthanides with polyaromatic terimine ligands. Thermodynamic data collected in dichloromethane at room temperature using the NMR titration method exhibit a largely improved affinity for capturing Ln(hfac)3 (up to three orders of magnitude) when L6 is replaced with its preorganized analogues L1 and L2. Next, to investigate the effect of rigidification on the photophysical properties of rigid ligands, the electronic UV-Vis absorption spectra of planar and extended π-conjugated systems found in L1 and L2 were recorded in dichloromethane solution at room temperature, revealing a large shift in the ligand-centered absorption bands towards lower energies by circa 8000 cm-1 compared to L6.

eng
Keywords
  • Coordination chemistry
  • Lanthanide
  • Rare-earth
  • Thermodynamics
  • Photophysics
Research group
Citation (ISO format)
NASERI, Soroush. Rigidifying N-donor Scaffolds and its Consequence on Thermodynamics and Photophysics of Mononuclear Ln(III) Coordination Complexes. 2023. doi: 10.13097/archive-ouverte/unige:169757
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Creation06/26/2023 9:27:46 AM
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