Gd-complexes of DTPA-bis(amides) functionalized by pyridine and picolinamide: Synthesis, thermodynamic stability, and relaxivity properties

Abstract

A series of DTPA-bis(amides) functionalized by pyridine (1a-c) and N-phenylpicolinamide) (1d-e) and their Gd(III)-complexes of the type [Gd(1)(H2O)]·xH2O (2a-e) were prepared and characterized by analytical and spectroscopic techniques. Potentiality of 2a-e as contrast agents for magnetic resonance imaging (MRI CA) was investigated by measuring relevant physicochemical properties and relaxivities and compared with [Gd(DTPA-BMA)(H2O)] (DTPA-BMA=N,N″-di(methylcarbamoylmethyl) diethylenetriamine-N,N′,N″-triacetate) (Omniscan®). The R 1 relaxivities of aqueous solutions of 2a-c are in the range of 3.33 -5.02 mM-1sec-1, which are comparable with those of Omniscan® (r1 = 4.58 mM-1sec-1). Complexes 2d-e, insoluble in water, exhibit relatively higher R1 values (8.1- 8.3 mM-1sec-1) in HP-β-CD solutions.