Premium
On the Mechanism of d–f Energy Transfer in Ru II /Ln III and Os II /Ln III Dyads: Dexter‐Type Energy Transfer Over a Distance of 20 Å
Author(s) -
Lazarides Theodore,
Sykes Daniel,
Faulkner Stephen,
Barbieri Andrea,
Ward Michael D.
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200800600
Subject(s) - superexchange , chemistry , luminescence , lanthanide , crystallography , ion , bridging ligand , electron transfer , quenching (fluorescence) , ligand (biochemistry) , analytical chemistry (journal) , atomic physics , physics , fluorescence , crystal structure , biochemistry , receptor , optoelectronics , organic chemistry , chromatography , quantum mechanics
We have used time‐resolved luminescence methods to study rates of photoinduced energy transfer (PEnT) from [M(bipy) 3 ] 2+ (M=Ru, Os) chromophores to Ln III ions with low‐energy f–f states (Ln=Yb, Nd, Er) in d–f dyads in which the metal fragments are separated by a saturated CH 2 CH 2 spacer, a p‐ C 6 H 4 spacer, or a p ‐(C 6 H 4 ) 2 spacer. The finding that d→f PEnT is much faster across a conjugated p‐ C 6 H 4 spacer than it is across a shorter CH 2 CH 2 spacer points unequivocally to a Dexter‐type energy transfer, involving electronic coupling mediated by the bridging ligand orbitals (superexchange) as the dominant mechanism. Comparison of the distance dependence of the Ru→Nd energy‐transfer rate across different conjugated spacers [ p‐ C 6 H 4 or p ‐(C 6 H 4 ) 2 groups] is also consistent with this mechanism. Observation of Ru→Nd PEnT (as demonstrated by partial quenching of the Ru II ‐based 3 MLCT emission (MLCT=metal‐to‐ligand charge transfer), and the growth of sensitised Nd III ‐based emission at 1050 nm) over approximately 20 Å by an exchange mechanism is a departure from the normal situation with lanthanides, in which long‐range energy transfer often involves through‐space Coulombic mechanisms.