Study on the radiative D-5(4) -> F-7(j) relaxation dynamics of Tb(III) in electrochemically excited self-assembled dimeric heterodinuclear Tb(III)-Ln(III)' chelates

A study has been conducted to explore the inter-lanthanide(III) energy inte ractions in self-assembled dimeric heterodinuclear 1-Tb(III)-Ln(III)'-1 che lates (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 elec trochemically initiated radiative D-5(4) --> F-7(j) 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)' ed ifices, (i) the Tb(III)-Dy(III) edifice initiates the exceptionally shea-li ved D-5(4) --> F-7(j) transitions of Tb(III) with k(i) approximate to 9.0 m s(-1) mainly due to the competitive inter-lanthanide(III) Tb(III)-Dy(III) D -5(4) --> F-4(9/2) back energy transfer, (ii) likewise, the Tb(III)-Y(III) edifice initiates the D-5(4) --> F-7(j) transitions of Tb(III) with k(i) ap proximate to 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 (3)p i pi* and/or Tb(III)-specific D-5(4) 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 inhib ition originates from the preferential ligand-specific 3 pi pi* relaxation to the Nd(III)-specific acceptor levels while in the case of Ln(III)' = Yb( III), this 3 pi pi* relaxation seems to occur directly to the excited F-2(5 /2) state of Yb(III) by the ET intermediate. (C) 2000 Elsevier Science B.V. All rights reserved.