Mehrstufige organische Redoxysteme — ein allgemeines Strukturprinzip

Deuchert, K.; Hünig, Siegfried

doi:10.1002/ange.19780901204

Cited by 159 publications

(36 citation statements)

References 136 publications

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“…The briefly mentioned oxidation processes of compound 1 occur at 0.84(60) and 1.00(60) V (Table II). This behavior is not unexpected for an organic two-step redox system of the Wurtz type [23], i.e. two oxidizable dimethylamino groups are weakly coupled via the 7r ligand.…”

Section: E Lectroch Em Istry An D Uv/vis Sp Ectroscopymentioning

confidence: 72%

Polychlorinated Biaryl Heterocycles as Potential Ligands. Reactions between Octachloro-1,10-phenanthroline and -2,2′-bipyridine with Copper(I) and Other Metal Ions

Titze

Kaim

1996

Zeitschrift Für Naturforschung B

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C hlorinated A rom atics, C opper C om pounds, C rystal Structure, Electrochem istry, H eterocycles Perchlorinated derivatives o f the com m on a -d iim in e chelate ligands 2,2'-bipyridine and 1,10-phenanthroline w ere synthesized and tested fo r their coordination behavior tow ards metal ions. O ctachloro-l.lO -ph en an th ro lin e (ocp) was o b tained via chlorination with P C I5 under pressure (300°C, 18 h). It fails to form stable com plexes w ith e.g. Fe2+, M n2+, Ru2+, N i2+, Z n 2+ or Cd~+, but yields com plex cations [M (ocp)2]+ w ith M = Cu, Ag. The crystal structure an aly sis o f the red tetrafluoroborate o f the copper(I) com plex cation reveals a distorted tetrahedral coordination at the metal w ith a slight tendency tow ards the trigonal-pyram idal arrangem ent; two essentially planar ligands w ith sm all bite angles intersect at alm ost right angle. Relative to conventional bis( 1,10-phenanthroline)copper(I) com plexes with sim ilar structures, [C u(ocp)2]+ has oxidation and reduction potentials shifted positively by about 1 V which leaves the energy o f the m ain M LC T absorption features little changed. A ttem pts to synthesize R u C h (o c p )2 in D M F produced as substituted product a sym m etrical b is(dim ethylam ino)-hexachloro-l,10-phenanthroline w hich can be oxidized electrochem ically in tw o steps. In contrast to ocp, octachloro-2,2'-bipyridine (ocb) show ed no detectable com plexation with C u+ and a very neg ative reduction potential, most probably due to its inability to exhibit a low -energy coplanar conform ation.Transition metal complexes with perhalogenated ligands have been investigated as potential oxida tion catalysts [1], The reason is the lower activation of C-Hal vs. C-H bonds in highly oxidized interme diates towards dissociation, Hal+ ions being much poorer leaving groups than H+. Examples include especially macrocyclic ligands such as the por phyrins [1], Small perchlorinated aromatic ligands were also used to investigate unusual and normally very reactive oxidation states such as Pt(III) [2].Perhalogenated derivatives of the standard adiimine chelate ligands 2,2'-bipyridine (bpy) and 1, 10-phenanthroline (phen) have not yet been systematically studied although the parent com pounds and their organosubstituted derivatives were employed as ligands in arrangements for oxidation catalysis [3]. In particular, (1,10-phenanthroline)copper(I) complexes with their low-lying metal(d)-to-ligand(7r*) charge transfer * R eprint requests to Prof. Dr. W. Kaim.(MLCT) excited states have received wide attention because of their long-standing application in ana lytical chemistry [4] and their more recent uses as "chemical nucleases" in site-specific DNA cleavage [51 and as photoactivated catalysts [6]. The struc tures of such molecules are also of relevance for supramolecular chemistry, e.g. for the synthesis of catenates and knotted molecules [7], for the under standing of the coordination and functioning of cop per centers in proteins [8] and for potential medical applications [9],...

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Section: E Lectroch Em Istry An D Uv/vis Sp Ectroscopymentioning

confidence: 72%

Polychlorinated Biaryl Heterocycles as Potential Ligands. Reactions between Octachloro-1,10-phenanthroline and -2,2′-bipyridine with Copper(I) and Other Metal Ions

Titze

Kaim

1996

Zeitschrift Für Naturforschung B

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“…In a detailed analysis, Fawcett et al [64] allowed for this complication by postulating that (t%~v~) be proportional to " 91 -a, with 0 < a < 1. In an attempt to overcome these problems in analyzing the solvent dynamical effects, Weaver [65] proposed to plot the logarithm of k~t (14) (K"elVn)obs = KA exp(--2, / 4RT) versus log(~/2rL -1) as follows directly from Eqs. (5) and (13).…”

Section: Rl Vi6~rt 'mentioning

confidence: 99%

“…(11) can be combined with the observed experimental rate constants to yield an "observed" preexponential factor (tr s according to Eq. (14). Examining the plot of logQr Vn)ob s versus log(f/2 rL -1) yields insights about the extent to which the rates are influenced by solvent dynamics.…”

Section: Rl Vi6~rt 'mentioning

confidence: 99%

“…In addition, the well-resolved ESR spectrum of methyl viologen has been used to demonstrate the applicability of the Fast Fourier transform in order to extract the hyperfine coupling constants from the autocorrelation [13]. Hª et al [14] pointed out that the viologen radical cations belong to the so-called Weitz-type radicals, i.e., radicals deduced from a two-step, organic redox system with the active group being part of a cyclic rc-system, which is aromatic in the oxidized state.…”

Section: Introductionmentioning

confidence: 99%

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ESR and ENDOR investigations of the degenerate electron exchange reactions of various viologens in solution. Solvent dynamical effects

et al. 2006

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The temperature dependences of the rates of the degenerate electron transfer of various viologens (l,l'-di(hydrocarbyl)-4,4'-bipyridinium salts) are measured in seven different solvents by means of electron spin resonance (ESR) line broadening. Rates vary between 1.7.10 s and 1.1 -l0 9 M-~s -~ at room temperature and clearly show a solvent dynamical effect, which is inferred from the dependence of the rate constants on the longitudinal relaxation time of the solvent. Activation energies ranging from 5.3 to 24.4 kJ mol -l are found. For the first time, hyperfine coupling constants are reported for the radical cations of the hydroxyethyl viologen and the amino viologen based on both continuous-wave ESR and electron-nuclear double resonance spectroscopy. Furthermore, the temperature and the solvent dependence of the hyperfine coupling constants of the methyl viologen radical cation are reported.

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“…[3b, 16]) and thus belongs to an electrochemically privileged family of Weiz-type structures. [18] To demonstrate the flexibility of the described synthetic protocol, a variety of helquats (Table 1) was synthesized. End-capped triyne 9 was transformed readily to hexasubstituted benzene derivative 10 showing that internal alkyne arms are well tolerated.…”

mentioning

confidence: 99%

Helquats: A Facile, Modular, Scalable Route to Novel Helical Dications

Adriaenssens¹,

Severa²,

Šálová³

et al. 2009

Chemistry A European J

104

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Mehrstufige organische Redoxysteme — ein allgemeines Strukturprinzip

Abstract: Ein allgemeines Strukturprinzip fur organische Verbindungen, die zur zweistufigen Elektronenubertragung befahigt sind, geht aus der folgenden Reaktionssequenz hervor:

Cited by 159 publications

References 136 publications

Polychlorinated Biaryl Heterocycles as Potential Ligands. Reactions between Octachloro-1,10-phenanthroline and -2,2′-bipyridine with Copper(I) and Other Metal Ions

Polychlorinated Biaryl Heterocycles as Potential Ligands. Reactions between Octachloro-1,10-phenanthroline and -2,2′-bipyridine with Copper(I) and Other Metal Ions

ESR and ENDOR investigations of the degenerate electron exchange reactions of various viologens in solution. Solvent dynamical effects

Helquats: A Facile, Modular, Scalable Route to Novel Helical Dications

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