Ruthenium complexes in different oxidation states: synthesis, crystal structure, spectra and redox properties

Abstract

The reactions of a mother solution of RuCl(3) with benzimidazole derivatives 2-(2'-pyridyl)benzimidazole (2,2'-PyBIm, L(1)) and 2-hydroxymethylbenzimidazole (2-CH(2)OHBIm, L(2)) yielded three novel ruthenium complexes: (H(2)L(1))(2)[Ru(III)Cl(4)(CH(3)CN)(2)](2)[Ru(IV)Cl(4)(CH(3)CN)(2)]·2Cl·6H(2)O (1), mer-[Ru(III)Cl(3)L(1)(CH(3)CN)]·L(1)·3H(2)O (2), and (HL(2))(4)[Ru(IV)Cl(6)]·2Cl·4H(2)O (3). The isolated compounds were characterised by elemental analyses, UV-Vis and IR spectroscopy, and magnetic measurements. The nature of the ligands bound to the metal ions of these compounds and the experimental conditions significantly influenced the ruthenium complexes in different oxidation states. The N,N-donor ligand bound to the metal centre is a recognised stabiliser of the +III state of ruthenium, whereas the lack of ligand coordination promotes the formation of a mixed (Ru(III)/Ru(IV)) complex. In the case of complex 3, the absence of a N,O-donor ligand in the coordinate sphere facilitates the formation of the compound in a higher oxidation state. X-ray single crystal analyses revealed an octahedral geometry in each of the complexes. The crystal structure of ruthenium complexes is formed by a network of intermolecular classical and unconventional (C-H···π) hydrogen bonds. The most interesting feature of the supramolecular architecture of complexes is the existence of a very rare Cl(-)···π interaction and π···π stacking, which also contribute to structural stabilisation. Ruthenium compounds 2 and 3 behave as paramagnets with an octahedral geometry, corresponding to the presence of one or two unpaired electrons, respectively. The cyclic voltammetric data of complex 2 show three one-electron redox processes. The first redox couple is reversible, whereas the two other couples have a quasi-reversible nature. In the case of complex 3, two redox couples are reversible and the electrode processes are connected with exchange of one electron.

Synthesis, Structural Characterization and Antimicrobial Evaluation of Ruthenium Complexes with Heteroaromatic Carboxylic Acids

“…Crystals of Ru complexes were obtained using a 0.1 m mother solution as precursor. The prepared solution contained chloride ruthenium complexes in the +III and +IV oxidation states . During complexation.…”

“…The prepared solution contained chloride ruthenium complexes in the + III and + IV oxidation states. [29,41] During complexation. four or six chloride ions were exchanged for organic ligands.…”

“…Having regard to the above, the main objective of our studies is to engage in research that aims to solve the problem of resistant antibiotic pathogens. We have previously reported studies on the series of the benzimidazole derivatives ruthenium complexes and their interesting structural and physicochemical properties . Moreover, the investigation of the interactions of the (HL 2 ) 4 [Ru IV Cl 6 ] ⋅ 2Cl ⋅ 4H 2 O (L 2 =2‐hydroxymethylbenzimidazole) with P. aeruginosa PAO1 biofilm was also evaluated .…”

“…We have previously reported studies on the series of the benzimidazole derivatives ruthenium complexes and their interesting structural and physicochemical properties. [29] Moreover, the investigation of the interactions of the (HL 2 ) 4 [Ru IV Cl 6 ] · 2Cl · 4H 2 O (L 2 = 2hydroxymethylbenzimidazole) with P. aeruginosa PAO1 biofilm was also evaluated. [30] The results of the experiments showed that the hydroxymethyl-substituted benzimidazole ruthenium(IV) complex reduces P. aeruginosa PAO1 biofilm formation by 84 %, and alters biofilm morphology and the living-to-dead cell ratio.…”

RuII and RuIII Chloronitrile Complexes: Synthesis, Reaction Chemistry, Solid State Structure, and (Spectro)Electrochemical Behavior

“…Crystallographic data and details of the data collection and structure determination for 3, 4a,b and 6. [29,32,[58][59][60][61][62][63] The average Ru-Cl bonds in the cationic part [RuCl(NϵCR) 5 ] + (4a, R = Me; 4b, R = Ph) are with 17Å], which is attributed to the chloride being in trans position to an acetonitrile ligand. [[29, 32,58] The respective N-Ru-N, N-Ru-Cl, Cl-Ru-Cl, Ru-N-C and N-C-C bond angles are in accordance with literature values (Table 2).…”