Reactivity of aqua coordinated monoporphyrinate lanthanide complexes: synthetic, structural and photoluminescent studies of lanthanide porphyrinate dimers

Abstract

Dimerization of monoporphyrinate lanthanide complexes [Yb(Por)(H₂O)₃]Cl, (Por = TTP²⁻, TMPP²⁻ and TPP²⁻) in the presence of sterically hindered tripodal ligand, zinc Schiff-base, dilute HCl, K₂CO₃ solution, 4,4′-bipyridine (bipy), and basic 8-hydroxyquinaldine (HQ) solution was observed in CH₂Cl₂ at room temperature. Six neutral dimeric lanthanide porphyrinate complexes, [Yb(TTP)(µ-OH)]₂(µ-THF) (1), [Yb(TMPP)(µ-OH)(H₂O)]₂ (2), [Yb(TPP)(µ-OH)(µ-H₂O)]₂ (4), [Yb(TMPP)(µ-Cl)(H₂O)]₂ (5), [Yb(TMPP)(µ-OH)]₂(THF) (6) and [Yb(TPP)]₂(µ-OH)(µ-Q) (7), were obtained. X-Ray diffraction studies showed that for the dimers, the two lanthanide ions were bridged by OH⁻, Cl⁻ or H₂O. Photoluminescent studies showed that the porphyrinate dianion acted as an antenna, transferred its absorbed visible energy to the lanthanide ion and enabled the latter emitting in the near-infrared (NIR) region. In general, the NIR emission is more intense for the dimers than for the monomers, and the NIR emission intensity decreases as the number of O–H oscillators present in the molecule increases.