Electrogenerated chemiluminescence. 52. Binuclear iridium(I) complexes

Abstract

estimates relying on metal-metal distance and size or alternancy of the bridging ligand.5b The contributions from very different kinds of metal fragments to the overlap with one specific ligand bridge are certainly more difficult to predict; however, intensities of pertinent charge-transfer transitions can serve as useful guidelines.25b This approach has triggered the successful search for organometallic d1 2345/d6 7(µ-pyrazine) analogues of the Creutz-Taube ion that display more intense charge-transfer transitions and much larger values of Kc than the inorganic parent system.25 Considering these more practically oriented rules for electronic coupling in addition to the well-known statistical and solvational contributions to Kc, it should thus be possible for experimentally working chemists to rationally design and synthesize new mixed-valence systems with very large stability constants.7,25 Acknowledgment. This work was generously supported by the Deutsche Forschungsgemeinschaft and Stiftung Volkswagenwerk.We also thank Degussa AG for donations of precious metal chemicals and Dr. Sylvia Ernst (Frankfurt) for preliminary experiments.

Electrochemical Reduction of 4‐Nitrobenzyl Phenyl Thioether for Activation and Capture of CO2

“…The new peak at E pa =+0.26 V (vs SCE) is related to the oxidation of oxalate in aprotic media, which is in agreement with that of tetrabutylammonium oxalate, TBA 2 O x (Figure 5b), and in the literature [35–37] …”

“…The reduction potential value of CO 2 decreases to almost 1.0 V. On the other hand, the reduction potential of CO 2 in aprotic media is À 2.2 V (vs SCE) in inert electrodes, which is very negative potential, [29] and also is reduced the potential in which CO 2 is directly reduced into its radical anion form, in almost 1 V. The new peak at E pa = + 0.26 V (vs SCE) is related to the oxidation of oxalate in aprotic media, which is in agreement with that of tetrabutylammonium oxalate, TBA 2 Ox (Figure 5b), and in the literature. [35][36][37] In order to determine the nature of the products obtained after the catalytic process, a control potential electrolysis was performed at E ap = À 1.2 V (vs SCE). The CO 2 reduction products were characterized in situ by Fourier transform infraredattenuated total reflectance (FTIR-ATR) spectroscopy (Figure 6a) after the passage of 1 F. The IR data show new peaks at frequencies υ = 1594 cm À 1 , υ = 1380 cm À 1 , and υ = 1337 cm À 1 , which would correspond with the formation of formate, HCOO À .…”

Electronic structures and photophysics of d8-d8 complexes

“…Rh(TMB) + (in MeCN) displayed bands at 740 and 570 nm, similar to those detected by flash photolysis upon reductive quenching. Reversible one-electron electrochemical reduction (as well as oxidation) was observed for Ir 2 (µ-3,5-R 2 -pyrazolyl) 2 (1,5cyclooctadiene) 2 complexes (R = H or Me); and electrochemiluminescence was detected upon cation/anion recombination [131]. (Electrochemiluminescence upon potential switching was seen also in the case of Pt(pop) that, however, shows neither reversible oxidation nor reduction [62,63].…”

“…In contrast, Ir 2 (µ-3,5-R,R'-pyrazolyl) 2 (1,5-cyclooctadiene) 2 (R,R' = H or Me) complexes undergo nearly reversible 1-electron oxidation in THF [131] or CH 2 Cl 2 [132]. A second irreversible oxidation, which occurs in CH 2 Cl 2 at more positive potentials, is facilitated by adding Lewis bases such as H 2 O (moisture) or MeCN.…”

Enhancing and inhibiting effects of benzenediols on chemiluminescence of a novel cyclometallated iridium(III) complex

“…In recent years, spurred by the success of CL and ECL detection with tris(2,2′)‐bipyridyl ruthenium(II), there is great interest in the development of new inorganic complex CL reagents by modifying the ligands or using different metals. Much of the literature on the luminescent complexes is concerned with several types of inorganic complex, such as Ru , Ir , Mo and La complexes, etc. Among them, cyclometallated iridium(III) complexes are seen as the most promising option, due to their relatively high photoluminescence efficiencies, wide range of emission wavelengths and stable redox characteristics .…”