Study on the radiative 5D4→7Fj relaxation dynamics of Tb(III) in electrochemically excited self-assembled dimeric heterodinuclear Tb(III)–Ln(III)′ chelates Original Research Article

A study has been conducted to explore the inter-lanthanide(III) energy interactions in self-assembled dimeric heterodinuclear 1-Tb(III)–Ln(III)′-1 chelates (Ln(III)′ = Dy(III), Nd(III), Y(III), Yb(III)) (1 = 2,6-bis[N,N-bis(carboxymethyl)-aminomethyl]-4-benzoylphenol]) and their effects on the electrochemically initiated radiative 5D4→7Fj transitions of Tb(III) of these dinuclear chelates at a cathodically pulse-polarized oxide-covered aluminium electrode. From the selected heterodinuclear Tb(III)–Ln(III)′ edifices, (i) the Tb(III)–Dy(III) edifice initiates the exceptionally short-lived 5D4→7Fj transitions of Tb(III) with ki ≈ 9.0 ms−1 mainly due to the competitive inter-lanthanide(III) Tb(III)–Dy(III) 5D4→4F9/2 back energy transfer, (ii) likewise, the Tb(III)–Y(III) edifice initiates the 5D4→7Fj transitions of Tb(III) with ki ≈ 1.4 ms−1 caused by the absence of any Y(III)-specific energy level capable of acting as the acceptor level for the ligand-specific 3ππ* and/or Tb(III)-specific 5D4 relaxations and, finally, (iii) the Tb(III)–Nd(III) and Tb(III)–Yb(III) edifices do not generate these radiative Tb(III) specific transitions; in the case of Ln(III)′ = Nd(III), this inhibition originates from the preferential ligand-specific 3ππ* relaxation to the Nd(III)-specific acceptor levels while in the case of Ln(III)′ = Yb(III), this 3ππ* relaxation seems to occur directly to the excited 2F5/2 state of Yb(III) by the ET intermediate.