Photochemical and Photophysical Reactions of fac-Rhenium(I) Tricarbonyl Complexes. Effects from Binucleating Spectator Ligands on Excited and Ground State Processes

Abstract

Ground and excited state properties of the newly prepared complexes Re(CO) 3 (2,2′-biquinoline)L S + , L S ) pyrazine or 4,4′-bipyridine, and Re(CO) 3 (2,2′-bipy)(2-pyrazinecarboxylate) were investigated by steady state and time-resolved spectroscopy. The X-ray structure of the latter compound showed that the spectator ligand 2-pyrazinecarboxylate is coordinated through the carboxylate group to Re(I). A component of the complexes' luminescence was associated with long-lived Re to ligand, 2,2′-biquinoline or 2,2′-bipy, charge transfer, while a fast component of the emission was associated with intraligand excited states. Quenching of the luminescence by CuCl 2 involved energy transfer via dynamic and static mechanisms. The complexes in their excited states were reduced by 2,2′,2′′-nitrilotriethanol with the formation of Re(I) ligand-radical species. Similar products were generated by the pulse radiolytic reduction of the complexes. The photochemical properties of the 2,2′-biquinoline complexes and Re(CO) 3 (1,10-phen)4-nitrobenzoate are compared, and the mechanisms of their photochemical reactions are discussed.

Reactivity of Molybdenum and Rhenium Hydroxo‐Carbonyl Complexes toward Organic Electrophiles

“…Elemental analyses were obtained by using a Perkin-Elmer 240-B microanalyzer. The IR spectra were recorded on a Perkin-Elmer FT 1720-X spectrophotometer, while the 1 [14] and [Re-(OTf)(CO) 3 (NÀN)] [44] were synthesized according to literature procedures.…”

On the Ligand‐to‐Metal Charge‐Transfer Photochemistry of the Copper(II) Complexes of Quercetin and Rutin

“…Absorbance changes, DA, occurring on a time scale longer than 15 ns were investigated at r.t. with a flash-photolysis apparatus described elsewhere [31]. In these experiments, 15 ns flashes of 351 nm light were generated with a Lambda-Physik-SLL-200 excimer laser.…”

Shielding of Electron Acceptors Coordinated to Rhenium(I) by Carboxylato Groups. Intraligand and Charge-Transfer Excited-State Properties of fac-(‘Anthraquinone-2-carboxylato')(2,2′-bipyridine)tricarbonylrhenium (fac-[ReI(aq-2-CO2)(2,2′-bipy)(CO)3])

“…Interest in the properties that L S imposes on the ÀRe I L A (CO) 3 moiety is brought about by possible applications of the Re complexes to biochemical processes [8 ± 11] and to CO 2 reduction [12]. Also, the derivatization of polymers with chromophores, e.g., with pendant ÀRe I L A (CO) 3 groups [13] has prompted investigation of the role of L S in the reactivity of some Re I monomers [14]. Literature reports show, for example, that the function of L S is to exert small perturbations that alter the electronic structure of the chromophore and modify its photophysics [6].…”

“…The photophysical and photochemical properties of [Re I (NO 2 Bz)L A (CO) 3 ] [7] and [Re I (pz-2-CO 2 )(2,2'-bipy)(CO) 3 ] ((2,2-bipyridine)tricarbonyl(pyrazine-2-carboxylato)rhenium) [14] have strongly suggested that the carboxylato group electronically insulates the Re I chromophore from the pendant 4-nitrophenyl and pyrazine moieties. In this work, we have studied the photophysics and redox reactivity of the 9,10-dihydro-9,10-dioxoanthracene-2-carboxylate x( anthraquinone-2-carboxylate; aq-2-CO 2 ) and its complex [Re I (aq-2-CO 2 )(2,2'-bipy)(CO) 3 ], to learn how such insulation by the carboxylato group of the ligand affects photoreactions initiated in Re I -to-L A and Re Ito-L S charge-transfer excited states MLCT and intraligand excited states IL.…”

“…± Flash-Photochemical Procedures. Optical-density changes occurring on a time scale longer than 10 ns were investigated with a flash-photolysis apparatus (FP) by procedures described elsewhere [14] [15]. In these experiments, 10-ns flashes of 351-nm light were generated with a Lambda-Physik SLL-200 excimer laser, or 1-ns flashes of 355-nm light were generated with a Continuum-Powerlite Nd-YAG laser [14 ± 16].…”