520 535 544 532 543 542The pigment of the blue cornflower, protocyanin, is a complex of high molecular weight. Iron(III) and aluminum ions combine with the anhydro base of the cyanin to form deep-blue complexes, which are stable in the physiological p H range. Complexes of this type also have been synthesized. Alkali iiretal salts play no part in blue flower pigments. Formation of blue complexes can be prevented by sequestration of the metal ions with stronger complexing agents, e.g. flavonols. The variuticn of flower colurs can be explained to a large extent on the basis of the complex formation of anthocyanins. In delphinidin glycosides, the color base or airhydro base is stable even in slightly acidic media.

SYNOPSISThe metal-complexing properties of five different polyaziridines-poly[I-(2-aminoethyl)aziridine], poly( 1-acetylaziridine), poly[ 1-(2-hydroxyethyl)aziridine], poly[l-(2-hy-droxyethy1)aziridine-co-1-acetylaziridine], and poly[ 1-(2-aminoethyl)aziridine] oxine-were investigated in an aqueous solution with regard to the side-chain effects using membrane filtration. The results are discussed and compared with the stability constants of metal complexation of the corresponding functional moieties. Poly[ 1-(2-aminoethyl)aziridine], a poly(aziridine) with neutral nitrogen donors in the side chains, showed similar complexing properties to those of ammonia. The only exceptions are Fe(II1) and Cr(III), which cannot form complexes with ammonia but can be retained in the membrane filtration process due to the formation of Fe(II1)-colloidal species and hydroxides. The complexing properties of polyaziridines containing hydroxyl groups in the side chains (i.e., poly[l-(2-hydroxy-ethy1)aziridinel and poly[ 1 -(2-hydroxyethyl)aziridine-co-l-acetylaziridine] can be explained and described by the formation constants with the corresponding hydroxides. The introduction of a carbonyl moiety in the polyaziridine side chain, e.g., polyacetylaziridine, reduces the complexing ability for metal ions because the carbonyl group cannot form complexes with the metal ions investigated. Poly[ 1-(2-aminoethyl)aziridine]oxine showed the strongest complexing ability in the series of metal ions due to the strong complexing ligand 8-hydroxy quinoline attached to the polymer backbone.

Der Farbstoff der blauen Kornblume, Protocyanin, ist ein Komplex von hohem Molekulargewicht. Eisen(III)‐ und Aluminium‐Ionen bilden mit der Anhydrobase des Cyanins tiefblaue Chelate, die im physiologischen pH‐Bereich beständig sind. Solche Komplexe sind auch synthetisch hergestellt worden. Alkalisalze spielen bei blauen Blütenfarben keine Rolle. Die Bildung blauer Komplexe kann durch Markierung der Metallionen mit stärkeren Komplexbildnern, z.B. Flavonolen, verhindert werden. Auf der Grundlage der Komplexbildung von Anthocyanen läßt sich die Variation der Blütenfarben in breitem Umfang erklären. Bei Delphinidinglykosiden ist die Farbbase oder Anhydrobase auch bei schwach saurem pH beständig.