NMR thermosensing properties on binuclear triple-decker complexes of terbium(III) and dysprosium(III) with 15-crown-5-phthalocyanine

Abstract

In this paper, we have firstly demonstrated the thermosensing properties of binuclear triple-decker terbium(III) and dysprosium(III) complexes with 15-crown-5-phthalocyanine Tb2[(15C5)4Pc]3 (I) and Dy2[(15C5)4Pc]3 (II) in the physiological temperature range (303–323 K). Measuring the LIS values for I and II in CDCl3 has revealed high temperature sensitivity for the signals of the aromatic protons of the inner deck of the complexes: ∂δ/∂T = 1.1 and 0.55 ppm/K for I and II, respectively. Terbium-containing complex I has the highest sensitivity of the LIS among the published complexes of 4f and d elements with polydentate ligands in organic media. A significant impact of the Curie-spin contribution to the paramagnetic spin–spin relaxation rate enhancement has been found, which has a pronounced temperature dependence.The results obtained for kinetically and thermodynamically stable Ln2[(15C5)4Pc]3 complexes allow one to consider them pronounced NMR thermosensors in nonpolar solutions. The possibility of the solubilization of complex I in aqueous media due to the presence of crown ether moieties has been also demonstrated.