Photosensitized generation of singlet oxygen from rhenium(i) and iridium(iii) complexes

Abstract

Photophysical properties in dilute acetonitrile solution are reported for a number of iridium(III) and rhenium(I) complexes. The nature of the lowest excited state of the complexes under investigation is either metal-to-ligand charge transfer ((3)MLCT) or a ligand centred ((3)LC) state. Rate constants, k(q), for quenching of the lowest excited states by molecular oxygen are in the range 1.5 x 10(8) to 1.4 x 10(10) M(-1) s(-1). Efficiency of singlet oxygen production, f(Delta)(T), following oxygen quenching of the lowest excited states of these complexes, are in the range of 0.27-1.00. The rate constants and the efficiency of singlet oxygen formation are quantitatively reproduced by a model that assumes the competition between a non-charge transfer (nCT) and a CT deactivation channel. The balance between CT and nCT deactivation channels, which is described by the relative contribution p(CT) of CT induced deactivation, is discussed. The kinetic model is found to be successfully applied in the case of quenching of the excited triplet states of coordination compounds by oxygen in acetonitrile, as was proposed for the quenching of pi-pi* triplet states by oxygen.

Re(I) carbonyl complexes: Multimodal platforms for inorganic chemical biology

“…Although Ru(II) polypyridyl species have been shown to be efficient photosensitizers for 1 O 2 , there are only scarce examples of use of Re(I) complexes for this application. In a pioneering work, Abdel-Shafi and co-workers studied three Re carbonyl complexes bearing either a 1,10-phenanthroline, a 2,2'-bipyridine, or a benzo[h]-quinoline ligand [68] and showed that these complexes were good sensitizers for singlet oxygen. More recently, others complexes with improved properties (higher irradiation wavelengths, higher absorption coefficient…) have been developed [69].…”

Underestimated Potential of Organometallic Rhenium Complexes as Anticancer Agents

“…The type II reaction is defined as generation of singlet oxygen via PS-oxygen interaction. 83 Although many more Re compounds have been identified as efficient triplet photosensitizers, 39,[84][85][86][87][88] this property has been more applied in photo-catalysis than in anti-cancer drug development.…”

A Tripodal Ruthenium(II) Polypyridyl Complex with pH Controlled Emissive Quenching

“…It is envisaged that a similar hydration sphere with water/D 2 O being included within the cavity lying along the C 3 axis is occurring in this situation. [32] In the presence of a large excess of small cations as chloride salts capable of occupying the cavity, such as Li + , Na + , K + , NH 4 + , the emission was not significantly perturbed, remaining comparable to that of [Ru(4) 3 ](OH) 2 in aqueous solution (Table 1). The addition of stoichiometric amounts of monovalent cations Li + , Na + , K + , NH 4 + as hexafluorophosphate salts to [Ru(4) 3 ](PF 6 ) 2 in acetonitrile resulted in no significant perturbation in the UV/Vis absorption spectra ( Figure S6).…”