Time‐resolved luminescence of terbium complexes with poly(2‐ and 4‐vinylpyridine N ‐oxide)s in aqueous solution

Terbium complexes with polymer ligands of poly(2‐ and 4‐vinylpyridine N ‐oxide)s (P2VPNO, P4VPNO) in aqueous solution were prepared and characterized. Multi‐exponential decays of the 5 D 4 → 7 F 5 terbium transition at 545 nm of [P2VPNO‐Tb 3+ ] and [P4VPNO‐Tb 3+ ] complexes were measured. The non‐linearity of semi‐logarithmic plots of time‐resolved luminescence was more pronounced in [P4VPNO‐Tb 3+ ] than in [P2VPNO‐Tb 3+ ], being reduced by addition of salts such as sodium formate or acetate. We assume that multi‐exponential decays of Tb 3+ in the complexes are caused by a back metal‐to‐ligand energy transfer via triplet state of N ‐oxide polymer ligand. By carrying out separate experiments in water and deuterium oxide, the number of coordinated water molecules in the [P4VPNO‐Tb 3+ ] complex was estimated as 4‐5, assuming that the Tb 3+ aqua complex contains nine water molecules.