Structurally Reinforced Chiral Macrocyclic Polyamine Copper (II) Complexes as Studied by ESR and Squid Measurements

We have synthesized structurally reinforced chiral pentaaza-fifteen-membered polyamines 1 and 2 with a dibridge for the purposes of studying the size-match selectivity of the macrocyclic cavity. Particularly, an attempt has been made to synthesize copper(II) complexes of 1 and 2 to characterize the size-match selectivity of the polyamines in term of microscopic details of the metal-ion binding site. For this purpose the use of ESR spectroscopy has been invoked before X-ray structural analyses of the complexes are carried out. Powder-pattern ESR spectra of the copper(II) complex of 1 in crystalline solid have revealed a temperature dependence of the copper hyperfine structure. This finding suggests that a vibronic effect features in the hyperfine spectra, showing that the pentaaza-macrocycle under study accommodates copper(II) ion and the macrocycle is flexible to exert "genuine" size-match selectivity.