Acid−Base and Electrochemical Properties of the MLCT Excited States and One-Electron-Reduced Forms of Ruthenium(II) Complexes Containing 2-(2‘-Pyridyl)pyrimidine and 2,2‘-Bipyridine in Aqueous Solution

Abstract

The acid-base and electrochemical properties of the MLCT excited states and the one-electron-reduced forms of the three Ru(bpy)(3)(-)()(p)()(pypm)(p)()(2+) complexes, where bpy = 2,2'-bipyridine, pypm = 2-(2'-pyridyl)pyrimidine, and p = 1-3, have been examined in aqueous solution; a determination has been made of the ground- and excited-state electrochemical potentials, the values of the pK(a) and deprotonation rate constants of the conjugate acids of the excited states and the one-electron-reduced complexes, and the kinetics of the second-order decays of the reduced species. Comparison is made with the behavior of the analogous 10 complexes of the form Ru(bpy)(3)(-)()(m)()(-)()(z)()(bpm)(m)()(bpz)(z)()(2+), where bpm = 2,2'-bipyrimidine, bpz = 2,2'-bipyrazine, m and z = 0-3, and m + z </= 3, which have been studied in detail before.

Application of Pulse Radiolysis to Mechanistic Investigations of Catalysis Relevant to Artificial Photosynthesis

“…+ and [Ru(bpy) 2 (pypmHC À )] 2 + (pypm = 2-(2'-pyridyl)pyrimidine) species produced by PR, [25] the mechanism for the formation of [Ru(bpy) 2 …”

Synthesis, Spectra and Electrochemistry of Isomeric DichloroBis-[1-Alkyl-2-(Naphthyl-(α/β)-Azo)Imidazole]Osmium(II): Single Crystal X-Ray Structure of Blue-Violet DichloroBis-[1-Ethyl-2-(Naphthyl-α-Azo) Imidazole]Osmium(II)

“…Bands in the 700-850 and 1050-1150 nm regions are weak (" $ 10 3 M À1 cm À1 ) and systematically shifted to higher energy on going from ctc to ccc-isomer. In d 6 -metal complexes, multiple charge transitions can arise from low-symmetry splitting of the metal levels, from the mixing of singlet and triplet configurations in excited states via spin-orbit coupling and from the presence of more than one interacting ligand, each contributing one * level [23][24][25][26]. The absorption properties of the present complexes have been compared with the spectra of ruthenium(II) analogues and it is concluded that the bands are blue shifted by 80-100 nm in the osmium(II) complexes along with appearance of a low energy band in the near-IR region.…”

“…This is in agreement with the -acidity order arylazopyridine > arylazoimidazole > naphthylazoimidazole. The presence of an additional aromatic ring in naphthyl derivatives may increase the electron density in the molecule and is one reason for reduced -acidity [26,27]. 1 H NMR spectra of the complexes were examined to determine isomeric structure.…”

Cyclometalated iridium(III) complex of 6‐hydroxydipyrido[3,2‐a:2′,3′‐c]phenazine: synthesis, and acid–base and avid DNA binding properties

“…[8,9] Many life processes, such as enzymes, operate within a very narrow pH window, but more work is required to broaden pH windows, and to improve the sensitivity of pH responses. For example, the complex [Ru(η 6 -p-cymene)Cl 2 (pta)] (pta = 1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane) was reported to exhibit interesting pH-dependent DNA damage and selectivity towards cancer cells.…”