Mechanism of the Photochemical Ligand Substitution Reactions of fac-[Re(bpy)(CO)₃(PR₃)]⁺ Complexes and the Properties of Their Triplet Ligand-Field Excited States

Abstract

We report herein the mechanism of the photochemical ligand substitution reactions of a series of fac-[Re(X(2)bpy)(CO)(3)(PR(3))](+) complexes (1) and the properties of their triplet ligand-field ((3)LF) excited states. The reason for the photostability of the rhenium complexes [Re(X(2)bpy)(CO)(3)(py)](+) (3) and [Re(X(2)bpy)(CO)(3)Cl] (4) was also investigated. Irradiation of an acetonitrile solution of 1 selectively gave the biscarbonyl complexes cis,trans-[Re(X(2)bpy)(CO)(2)(PR(3))(CH(3)CN)](+) (2). Isotope experiments clearly showed that the CO ligand trans to the PR(3) ligand was selectively substituted. The photochemical reactions proceeded via a dissociative mechanism from the (3)LF excited state. The thermodynamical data for the (3)LF excited states of complexes 1 and the corrective nonradiative decay rate constants for the triplet metal-to-ligand charge-transfer ((3)MLCT) states were obtained from temperature-dependence data for the emission lifetimes and for the quantum yields of the photochemical reactions and the emission. Comparison of 1 with [Re(X(2)bpy)(CO)(3)(py)](+) (3) and [Re(X(2)bpy)(CO)(3)Cl] (4) indicated that the (3)LF states of some 3- and 4-type complexes are probably accessible from the (3)MLCT state even at ambient temperature, but these complexes were stable to irradiation at 365 nm. The photostability of 3 and 4, in contrast to 1, can be explained by differences in the trans effects of the PR(3), py, and Cl(-) ligands.

Effect of Substituent Groups in Rhenium Bipyridine Complexes on Photocatalytic CO2 Reduction

“…The rhenium bipyridine complex Re(bpy)(CO) 3 Cl (bpy = 2,2′-bipyridine) has been reported to act as a photocatalyst that photochemically reduces CO 2 to CO and/or COOH in the presence of electron donors, such as triethanolamine (TEOA), under UV light irradiation [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] (Scheme 1). Many researchers have focused on increasing the reaction efficiency of the photoreduction of CO 2 to CO by substituting Cl with a certain ligand.…”

Materials for Organic Light Emitting Diode (OLED)

“…The reaction quantum yields (Φ react ) decreases by decreasing reaction temperature. Comparing temperature dependence of isomerization of mer-Ir(F 2 ppy) 3 [12] and carbonyl ligand and solvent acetonitrile exchange reaction of renium carbonyl complex showed similarity [30]. Emission quantum yields (Φ em ) and Φ react behave complementary, therefore, Φ em are increasing by decreasing temperature, however, Φ react are decreasing by decreasing temperature.…”

Ultrafast 2D–IR Spectroscopy of Transient Species

“…MLCT in rhenium(I)polypyridyl carbonyls has been extensively studied with regard to electronic structure changes, [29][30][31] solvation dynamics, [32] photochemistry, [33,34] nonlinear optical properties [35] or as luminescent markers. [36] Static and Time-Resolved 1D-IR Figure 3 b shows the IR absorption spectrum of the electronic ground state.…”