31378-26-4Relevant articles and documents
Multiple one-electron oxidation and reduction of trinuclear bis(2,4-pentanedionato)ruthenium complexes with substituted diquinoxalino[2,3-a:2′,3′-c]phenazine ligands
Ghumaan, Sandeep,Sarkar, Biprajit,Patil, Mahendra P.,Fiedler, Jan,Sunoj, Raghavan B.,Kaim, Wolfgang,Lahiri, Goutam Kumar
, p. 3409 - 3418 (2007)
The complexes (μ3-L1/L2)[Ru(acac)2]3, acac- = 2,4-pentanedionato, L1 = 2,3,8,9,14,15-hexachlorodiquinoxalino[2,3-a:2′,3′-c]phenazine and L2 = 2,3,8,9,14,15- hexamethyldiquinoxalino[2,3-a:2′,3′-c]phenazine, undergo stepwise one-electron oxidation involving a total of three electrons and stepwise one-electron reduction with three (L2) or four electrons (L1). All reversibly accessible states were characterized by UV-Vis-NIR spectroelectrochemistry. Oxidation leads to mixed-valent intermediates {(μ3-L)[Ru(acac)2]3}+ and {(μ3-L)[Ru(acac)2]3}2+ of which the RuIIIRuIIRuII combinations exhibit higher comproportionation constants Kc than the RuIIIRuIIIRuII states - in contrast to a previous report for the unsubstituted parent systems {(μ3-L3)[Ru(acac)2]3}+/2+, L3 = diquinoxalino[2,3-a:2′,3′-c]phenazine. No conspicuous inter-valence charge transfer absorptions were observed for the mixed-valent intermediates in the visible to near-infrared regions. The monocations and monoanions were characterized by EPR spectroscopy, revealing rhombic ruthenium(III) type signals for the former. Electron addition produces ruthenium(II) complexes of the reduced forms of the ligands L, a high resolution EPR spectrum with 14N and 35,37Cl hyperfine coupling and negligible g anisotropy was found for {(μ3-L1)[Ru(acac)2]3}-. DFT calculations of (μ3-L1)[Ru(acac)2]3 confirm several ligand-centered low-lying unoccupied MOs for reduction and several metal-based high-lying occupied MOs for electron withdrawal, resulting in low-energy metal-to-ligand charge transfer (MLCT) transitions.
The metal complex, a chiral nematic liquid crystal composition and crystal (by machine translation)
-
Paragraph 0062; 0063, (2019/03/01)
[Problem] helical twisting power (βM ) Is increased, and, compatibility with a large metal complex of a nematic liquid crystal, chiral nematic liquid crystal composition using the same, and a liquid crystal element. (1) Or formula (2) represented by the formula [a] complex. (1) Or formula (2) in the metal complex represented by formula having chirality, nematic liquid crystal compounds containing chiral nematic liquid crystal compositions. Chiral nematic liquid crystal composition is filled between a pair of liquid crystal element. (R is C1 a-20 straight chain alkyl group or an alkoxy group of straight chain C1 a-20)[Drawing] no (by machine translation)
Inversion of axial chirality in coordinated bis-β-diketonato ligands
Sato, Hisako,Mori, Yukie,Kitazawa, Takafumi,Yamagishi, Akihiko
, p. 232 - 237 (2013/04/10)
Mononuclear and dinuclear ruthenium(iii) complexes with bis-β-diketonato ligands (denoted by [Ru(acac)2(L-LH)] and [Ru(acac)2(L-L)Ru(acac)2], respectively) were synthesized, where acac, L-LH- and L-L2- denote acetylacetonato, monoprotonated and unprotonated bis-β-diketonato ligands, respectively. The following three ligands were used as the bis-β-diketonato ligand (L-L 2-): 1,2-diacetyl-1,2-dibenzoylethanato (denoted by dabe 2-), 1,2-diacetyl-1,2-bis(3-methylbutanoyl)ethanato (baet 2-) and 1,2-diacetyl-1,2-dipropanoylethanato (dpe2-). For the mononuclear and the meso-type dinuclear complexes, a pair of diastereomeric species were identified as Δ- (or Λ-) [Ru(acac)2(R- or S-L-LH)] and [Δ-Ru(acac)2(R- or S-L-L)Λ-Ru(acac) 2], respectively. The possibility of thermal inversion in coordinated L-LH- (mononuclear) or L-L2- (dinuclear) was pursued by monitoring the changes in the electronic circular dichroism or the 1H NMR spectra. No inversion occurred for the dinuclear complexes, when their chloroform solutions were kept at 50 °C for ca. 100 h. In contrast, some of the mononuclear complexes underwent the inversion of axial chirality to give an equilibrium mixture under the same conditions. The reaction followed the first-order rate law and the overall first-order rate constants (k) of [Ru(acac)2(L-LH)] were determined to be k = 0.13, 0.0048 and less than 0.001 h-1 for L-LH- = dabeH-, baetH - and dpeH-, respectively. The results suggest that the main factor determining the barrier height of the internal rotation is not the steric but the electronic properties of the carbon-carbon bond connecting the two β-diketonato moieties. The Royal Society of Chemistry 2013.
