Jp. Collin et al., Synthesis and photophysical properties of iridium(III) bisterpyridine and its homologues: a family of complexes with a long-lived excited state, J AM CHEM S, 121(21), 1999, pp. 5009-5016
A new synthetic procedure has been developed which makes possible the prepa
ration of IrLL'3+ complexes (L, L' = terpyridine derivative) in good yields
. In a first step, IrLCl3 is obtained under relatively mild conditions as a
n intermediate. Subsequent reaction with L' (a few minutes in refluxing eth
ylene glycol) affords IrLL'3+. The electrochemical behavior and ground- and
excited-state spectroscopic properties of four IrLL'3+ complexes in nitril
e solvents are reported. The X-ray structure of one of these complexes is a
lso described. The complexes have been designed keeping in mind their incor
poration in linearly arranged multicomponent arrays, according to a templat
ing strategy based on the assembly of tpy-type ligands by the Ir(III) cente
r. The complexes feature a high-lying level for the luminescent excited sta
te (>2.5 eV), with a satisfactory room-temperature luminescence intensity (
phi(em) approximate to 10(-2)) and lifetime on the microsecond time scale.
These favorable properties indicate that the Ir(III)-tpy center will not be
the final recipient of the energy-harvesting processes in multipartite sys
tems built around them. Temperature-dependent studies of the luminescence p
roperties in the 95-298 K range indicate that the higher-lying levels of th
ese complexes are not efficient pathways for deactivation of the luminescen
t states. For these reasons, it is concluded that the studied Ir-tpy-type c
omplexes are well suited (i) to play the role of photoactive center and to
gather photo- and electroactive units or (ii) to act as electron relays in
linearly arranged multicomponent arrays.