PUB - Publikationen an der Universität Bielefeld

The triplesalen ligand system based on three salen-like coordination environments bridged by a common phloroglucinol ring had been designed and successfully applied for the rational synthesis of single-molecule magnets from two trinuclear triplesalen complexes and one hexacyanometallate by supramolecular recognition. In order to optimize this system with respect to magnetic anisotropy, the triplesalophen ligand system has been identified, which should allow for the synthesis of nonanuclear complexes comprised of two trinuclear triplesalophen complexes and three connecting units. Herein, the convergent synthesis of the triplesalophen ligand system is described, which differs form the divergent strategy for the triplesalen ligand system. The molecular and electronic structures of the triplesalophen ligands H6baronR (R = Me, Cl, Br) have been established by single-crystal X-ray diffraction, NMR spectroscopy, FTIR, and UV-vis spectroscopy. These complementary methods allowed the assignment of the central compartment not to be in the O-protonated tautomer but in the N-protonated tautomer with the prevalence of a keto-enamine resonance description, which we term hetero-radialene. Furthermore, the comparison with the mononucleating unsymmetrical salophen reference ligand H2carlCl and with compounds from the literature provides unique signatures for the appearance of the hetero-radialene motive not only in NMR spectra and structural parameters but also in IR and UV-vis spectra. These signatures form the basis for the interpretation and understanding of the electronic structures of transition metal complexes with the triplesalophen ligand system.