Metallkomplexe von Farbstoffen. VI. Phosphan‐Nickel‐, Palladium‐ und Platin‐Komplexe sowie Pentamethyl‐cyclopentadienyl‐Rhodium‐ und Iridium‐Komplexe von Bis(2‐hydroxyaryl)azo‐Farbstoffen

Abstract

Die dreizähnigen Dianionen von 2,2′‐Dihydroxyazobenzol (L1H2), 1‐(2‐Hydroxy‐4‐nitrophenylazo)‐2‐naphthol (L2H2), 1‐(2‐Hydroxy‐5‐nitrophenylazo)‐2‐naphthol (L3H2) und 1‐Phenyl‐3‐methyl‐4‐(2‐hydroxy‐5‐nitrophenylazo)‐5‐pyrazolon (L4H2) bilden mit den chloroverbrückten Komplexen [(R3P)MCl2]2 (M = Pd, Pt; R = Ph, nBu), [(n5‐C5Me5)MCl2]2 (M = Rh, Ir) sowie mit (nBu3P)2NiCl2 die Farbstoff‐Komplexe (R3P)ML (M = Ni, Pd, Pt) und (n5‐C5H5)ML (M = Rh, Ir). Die Strukturen von (Ph3P)PtL1 und (nBu3P)PdL3 wurden röntgenographisch bestimmt. Für die Komplexe (n5‐C5Me5)ML (M = Rh, Ir) mit „asymmetrischem”︁ Metallatom lassen sich NMR‐spektroskopisch zwei Diastereoisomere nachweisen, was für den „Hydrazon”︁‐Charakter der Azoliganden mit pyramidalisiertem N‐Atom spricht.

An Organometallic Chemosensor for the Sequence‐Selective Detection of Histidine‐ and Methionine‐Containing Peptides in Water at Neutral pH

“…It appears likely that the indicator is attached to the metal through the diazo and the phenolate groups as Cp*Rh complexes are known to form stable N,O-chelates with azophenolates. [14] At room temperature, the reaction between 1 (12.5 mm) and 2 (25 mm) proceeds with a half-life of t 1/2 = 2.5 min; at 50 8C, the reaction is complete within 5 min. The interaction between the indicator and the rhodium complex is very strong: fitting of the titration data to a 1:1 binding algorithm yielded a binding constant of 3.2(AE 1.0) 10 7 m À1 .…”

An Organometallic Chemosensor for the Sequence‐Selective Detection of Histidine‐ and Methionine‐Containing Peptides in Water at Neutral pH

“…So far, 3d transition-metal ions have been used almost exclusively for this purpose. [14] At room temperature, the reaction between 1 (12.5 mm) and 2 (25 mm) proceeds with a half-life of t 1/2 = 2.5 min; at 50 8C, the reaction is complete within 5 min. On the other hand, they may show very high binding constants which would allow the detection of analytes at low concentrations.…”

“…[14] At room temperature, the reaction between 1 (12.5 mm) and 2 (25 mm) proceeds with a half-life of t 1/2 = 2.5 min; at 50 8C, the reaction is complete within 5 min. Clear isosbestic points are observed at l = 554 and 443 nm which indicate that a single species is formed.…”