Untersuchungen der Symmetrieverhältnisse in äquatorial koordinierten 2:1‐Arylazo‐Co^III‐Komplexen mit Hilfe der Protonenresonanz

Abstract

The magnetic equivalence of ligand protons was examined with aid of NMR. spectroscopy for a large number of 1 :2 CoIII-complexes of tridentated azo dyestuffs forming a representative cross section of the whole class of substances. It was established by this investigation that ligands with a moderately polarised azo group have a particular inclination to form asymmetrical complexes in which the protons of the two ligands are not magnetically equivalent. On the other hand, ligands having a non-polarised or a strongly polarised azo group tend to form symmetrical complexes. In three cases both symmetrical and asymmetrical complexes were isolated. As in previous investigations [I], up to a total of 5 complexes were again observed, which indicates a t least two causes governing the symmetry conditions. The phenomena described here could be explained with an alternative coordination of the two azo nitrogen atoms. On the basis of the NMR. results, however, preference is given to an exchange of the azo with the hydrazone form.

Current Developments in Optical Data Storage with Organic Dyes

“…[63,109] Bond isomerism (N a ,N b isomerism) occurs in both the planar [110,111] and the octahedral structure. [112,113] If the third substituent is, for example, an OH group, N a ,N b isomers are formed with different combinations of 5/6 and 6/5 chelate rings, such as in 24-26, which exhibit different absorption spectra. [113] This was a first starting point.…”

Aktuelle Entwicklungen in der optischen Datenspeicherung mit organischen Farbstoffen

“…Auch ein Verfahren für die Bromierung alkoxysubstituierter Phthalocyanine wurde beansprucht, [104] und Ferrocen wurde chemisch an die Phthalocyanine gebunden. [105][106][107] [63,109] Die Bindungsisomerie (N a ,N b -Isomerie), kommt sowohl bei planarer [110,111] als auch bei oktaedrischer Struktur [112,113] vor. Ist der dritte Substituent beispielsweise eine OH-Gruppe, so bilden sich N a ,N b -Isomere mit verschiedenen Kombinationen von 5/6-und 6/5-Chelatringen, wie 24-26 illustrieren, die unterschiedliche Absorptionsspektren aufweisen.…”

Molecular Structures and Redox Properties of Homoleptic Aluminum(III) Complexes with Azobisphenolate (azp) Ligands

“…2,2 -Azobisphenol (H 2 azp) is one of the azo dyes known as intense coloring and/or fluorometric reagents that can quantitatively analyze for specific ions such as magnesium [4][5][6][7], aluminum [4,[8][9][10], and gallium [4,8,9]. The molecular structures of homoleptic 1:2 Cr III and Co III complexes with azp derivatives were extensively studied by Schetty [11][12][13][14][15][16]. The meridional ONO-tridentate coordination to metal ions was confirmed by the crystal structure analysis for homoleptic 1:2 Cr III [17] and Mn IV [18] complexes with a non-substituted azp ligand.…”