Photophysics, rhenium diimine complexes

Photophysics and Photochemistry of Organometallic Rhenium Diimine Complexes... 

Understandably, there is an enormous richness in the photophysical and photochemical behavior of the excited states present in diimine rhenium tricarbonyl complexes. Indeed, this plethora of molecular photophysical characteristics has led to a wide range of interesting and important applications, including their use as catalysts [21-25], sensors [26-33], probes for photo-polymerization [10, 34, 35], optical switches [36 15], light-emitting materials [46-52], nonlinear optical materials [53-56], binding or photocleavage of DNA [57-61], and radiopharmaceuticals [62-66], Under the purview of this article our focus will be to cover photophysical and photochemical properties and hence other aspects, such as synthetic, catalytic, pharmaceutical, etc., will not be discussed. 

Photophysics of Rhenium(I) Diimine Complexes A. Electronic Structure of Rhenium(I) Diimine Complexes Photophysical Relaxation Process of Rhenium(I)... 

Lo and co-workers reported the synthesis, characterisation, photophysical and electrochemical properties of luminescent rhenium(I) diimine indole complexes [Re(N"N)(CO)3(py-indole)]+ (36) [75,76]. Upon visible-fight irradiation, the complexes exhibited 3MLCT (dTt(Re) —> Tt (N N)) emission in fluid solutions at 298 K and in low-temperature glass. When these com-... 

This case study deals with different photophysical properties of a variety of diimine rhenium(I) tricarbonyl complexes. The exceptionally diverse photophysical behavior of these complexes is largely dependent on the nature of their lowest excited states. Varying the substituents on either the diimine ligands or ancillary ligands can easily change the relative order of these excited states and provides a way to tune the excited-state characteristics. A range of important applications is now becoming apparent, based on the richness of the photophysical and photochemical properties of diimine rhenium(I) tricarbonyl complexes. 

The robustness of the rhenium(i) diimine alkynyl systems and rich photophysical behavior have rendered them suitable as metalloligands for the synthesis of mixed-metal complexes. It is well-known that organometallic alkynes exhibit rich coordination chemistry with Cu(i), Ag(i) and Au(i) [214-218], however, photophysical properties of these r-coordinated compounds are rare. Recent work by Yam and coworkers has shown that luminescent mixed-metal alkynyl complexes could be synthesized by the metalloligand approach using the rhenium(i) diimine alkynyl complexes as the z -ligand. Reaction of the rhenium(i) diimine alkynyl complex [Re(bpy)(CO)3C=CPh] with [M(MeCN)4]PF6 in THF at room temperature in an inert atmosphere afforded mixed-metal Re(i)-Cu(i) or -Ag(i) alkynyl complexes (Scheme 10.31) [89]. Their photophysical properties have also been studied. These luminescent mixed-metal complexes were found to emit from their MLCT[d7i(Re) —> 7i (N N)] manifolds with emission bands blue-shifted relative to their mononuclear precursors (Table 10.5). This has been attributed to the stabilization of the dTi(Re) orbital as a consequence of the weaker t-donating ability of the alkynyl unit upon coordination to the d metal centers. 

In recent years, this section of this report has been dominated by the photochemical and photophysical properties of Re(CO)3(diimine)X complexes. Although the main deluge of research is over, there are still examples to be found. The photochemical/physical properties of monomer and polymer species with ReI(CO)3(phen) chromophores has been investigated by Wolcan and Ferraudi, and proton-controlled photoisomerisation of rhenium(I) tricarbonyl bipyridine linked to amine or azacrown ether groups by a styryl pyridine bridging ligand has been discovered by Perutz et alP... 

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