Neuartige Pyrrol/Pyrazol-Bausteine für die Synthese von Hybrid-Makrozyklen, azyklischen Ligandsystemen und bimetallischen Komplexen

Abstract

The present work focussed on the synthesis of a versatile pyrrole-pyrazole key building block (3,5-bis-(3,4-diethyl-1-formylpyrrol-2-ylmethyl)-1H-pyrazol), and its application in the synthesis of a novel class of pyrrole-pyrazole-containing hybrid macrocycles and acyclic diimine ligands. The novel hybrid Schiff-base macrocycles can be regarded as pyrazole-analogues of the well-known texaphyrinogen and represent the first example of this type of macrocycle described. The pyrrole-pyrazole-containing Schiff-base compounds were structurally characterized by X-ray analysis, mass spectrometry, UV-vis, NMR and IR spectroscopy. Their acid-base properties as well as anion recognition abilities were investigated and discussed. The novel versatile building blocks were also used to synthesize a series of pyrrole-pyrazole-containing acyclic diimine-ligands to form bimetallic metal complexes. It could be shown that only metal-ions that prefer a square planar coordination sphere, such as Pd(II), Ni(II) or Cu(II), were able to form stable complexes with the tridentate ligand. X-ray analysis of the resulting metal complexes demonstrated the existence of a bridging-ligand (µ-OH- or Cl-ion) between the metal-ions, which could easily be exchanged by other bridging-ligands. These exchange reactions were extensively investigated by mass spectrometry (ESI-MS) as well as NMR and IR spectroscopy.