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RESEARCH PRODUCT

Synthesis and Magnetic Properties of Novel Azamacrocyclic LnIII, CuII, FeIII, and SrII Complexes and Conformational Analysis of the Ligands

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Hexaalkoxy-substituted azamacrocyclic metal complexes 1 · MXn [MXn = FeCl3, CuCl2, SrCl2, Ln(NO3)3; Ln = La, Pr, Eu, Ho, Er] with various chain lengths were prepared by a convergent approach using 1,2-bisalkoxy-4,5-diamines 3 and 4-alkoxy-pyridine-2,6-dicarbaldehydes 4 as key building blocks for template-assisted cyclocondensation. Metal complexes 1 · MXn were considered as potential metallomesogens. However, differential scanning calorimetry and optical polarizing microscopy of 1 · MXn did not reveal any mesomorphism. The magnetic susceptibility shows deviation from Curie-like behavior. Due to ligand field effects the effective magnetic moments are a function of the temperature. In order to obtain structural informations on the free ligand 1, which is synthetically not accessible, theoretical calculations were carried out. For the free azamacrocycle 2a and the free hexamethoxy-substituted azamacrocycle 1a the IR spectra were computed at the level of density functional theory. A planar and a saddle-shaped conformation was considered. The IR spectra and especially the dependence of the C=N vibration on the structural parameters and the charge distribution are discussed.