Quantitative Photochemistry and Mechanisms for a Series of Rhodium Dicarbonyl Derivatives

Abstract

A comparison of the electronic properties and photochemical reactivity efficiencies for a series of rhodium dicarbonyl complexes with the general formula XRh(CO)2, where X = Cp (η5-C5H5), Cp‘ (η5-C5H4Me), Cp‘ ‘ (η5-C5HMe4), Cp* (η5-C5Me5), ind (η5-C9H7), and acac (C5H7O2), has been achieved. The photochemical reactions of these molecules have been studied under a variety of experimental conditions, where binucleation, intermolecular Si−H and C−H bond activation, and ligand substitution processes occur. Modifications of the unique ligand in this system enable the photoefficiency of the CO dissociation reaction to be substantially changed. The absolute reaction quantum efficiencies (φcr) are markedly different and strongly wavelength dependent for each of the molecules studied. The values of φcr decrease in the order CpRh(CO)2 > Cp‘Rh(CO)2 > Cp*Rh(CO)2 ≫ (acac)Rh(CO)2 > (ind)Rh(CO)2 and vary by over 3 orders of magnitude depending on the complex chosen and the excitation wavelength employed. The results obtained indicate that the photoefficiencies of these complexes are predominantly determined by radiative and nonradiative decay processes of neighboring excited states and the electronic and steric properties of the unique ligand.

Platinum‐Group Chelate Complexes with 9‐Hydroxyphenalenone Derivatives: Synthesis, Structures, Spectroscopic Properties and Cytotoxic Activities

“…The lowest energy absorption bands for the metal complexes were found at lower energies than those of the ligands: λ max = 498 (2a), 497 (2b), 477 (3), and 461 nm (4) in DMF, and at around λ max = 460 nm for 1a-c in dichloromethane. Compounds 1a-c decomposed [16] when heated in DMF or DMSO.…”

“…Solid [Rh I (acac) 2 (CO) 2 ] also exhibits weak π-π* emission as a structured band in the 430-530 region. [16] Dinuclear Rh I complexes often exhibit a strong red emission between 650 and 850 nm because of metal-metal interactions, [21] but, in the case of 1b, the emission was very weak. This might be a consequence of the highly conjugated nature of the ligand.…”

Excited state properties of (acetylacetonato)dicarbonyliridium(I)

“…The electronic spectrum ( Fig. 1) in CH 3 CN shows absorptions at k max = 375 nm (sh, e = 800 M À1 cm À1 ), 336 (sh, 3800), 298 (9500), 262 (12,200) 237 (13,200) greenish photoluminescence (Fig. 1) at k max = 480 nm which is independent of the concentration.…”

“…Moreover, solutions of Rh(CO) 2 acac have not been reported to be emissive. However, solid Rh(CO) 2 acac shows the acac IL emission [12] since the rigid lattice apparently prevents a photodissociation. The new longwavelength absorptions of Ir (CO) 2 acac at higher concentrations which appear above 400 nm are probably caused by an association.…”

“…Indeed, it is known that in contrast to Rh I (CO) 2 acac, our target complex is much less light sensitive [10,11]. In the Rh(I) complex reactive LF states are apparently low enough to dominate the excited state behavior of the complex [12].…”