Diimine rhenium tricarbonyl

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. 

Metal-Directed Macrocyclic Complexes Incorporating Diimine Rhenium Tricarbonyl Moieties... 

Villaume S, Daniel C (2005) Emission spectroscopy of metal-to-ligand-charge-transfer states of HRe(CO)3(H-DAB), model system for alpha-diimine rhenium tricarbonyl complexes. Comptes Rendus Chimie 8 1453-1460... 

L. Sacksteder, A. P. Zipp, E. Brown, J. Streich, J. N. Demas, and B. A. DeGraff, Luminescence studies of pyridine a-diimine rhenium(I) tricarbonyl complexes, Inorg. Chem. 29, 4335-4340... 

These complexes also usually exhibit substantial photostability under visible light irradiation and, due to their relatively long-lived triplet excited-state characteristics, the emission lifetimes are easily quenched by bimolecular electron- and/or energy-transfer processes in solution [6, 76], The electronic structures of MLCT excited molecules of diimine rhenium(I) tricarbonyl complexes can be viewed as a charge-separated species, [LRen(CO)3(diimine ")], with an essentially oxidized... 

EXCITED-STATE PROPERTIES OF DIIMINE RHENIUM(I) TRICARBONYL COMPLEXES INTERRELATIONSHIPS BETWEEN MLCT, LLCT, AND IL EXCITED STATES... 

Another important type of LLCT state arising in diimine rhenium(I) tricarbonyl complexes is found in IRe (CO)3(diimine) complexes. When I replaces Cl or Br, the lowest excited states changes from being MLCT in nature to that of XLCT (halide-to-ligand charge transfer) in character. Figure 2 clearly shows that the lowest energy band of the transient absorption... 

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. 

These bands show negative solvatochromism as revealed by band shifts to lower energy in less polar solvents [5, 7, 8, 12], The direction of the solvent dependence is associated with a reduced (and reversed) molecular dipole in their MLCT excited states. Emissions from these complexes are typically broad and structureless, and they also often exhibit a rigidochromic effect [7-12], Tables 1 and 2 summarize the luminescence characteristics and environmental effects on absorption and emission maxima for rhenium(I) tricarbonyl diimine complexes. 

Fig. 16 Rhenium(I) tricarbonyl diimine complexes with crown ether pendants as metal cation...

Fig. 17 Luminescent rhenium(I) tricarbonyl diimine-biotin complexes as probes for avidin...

Fig. 18 The structure of rhenium(I) tricarbonyl diimine complex for anion sensing and the absorption spectral changes of this probe molecule (2.5 x 10 5 M) in CII )CN upon addition of n-Bu4NF, (a) [F ] = 0 - 2.8 x 10 5 M and (b) [F ] = 2.8 x 10 5 - 1.1 x 10 4 M. (reproduced with permission from [155])...

Fig. 4. Plots of In of various rhenium(I) diimine tricarbonyl complexes versus Eoo( MLCT) at 25 °C in a degassed CH3CN solution.

Z)-Stilbene]Cr(CO)3 showed three optically accessible excited states. One of these excited states caused (E)-(Z) isomerization and the other resulted in a slow release of carbon monooxide. " Tetranuclear rhenium(I) tricarbonyl diimine complexes (20) with a stilbene-like bridging ligand showed efficient photoswitching properties. The accurate quantum yields of the photoisomerization of the mononuclear rhenium(I) tricarbonyl diimine complex could be determined readily by the H NMR technique in eombination with absorption spectroscopy. ... 

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... 

---