The ligand N,N -bis [(6-carboxy-2-pyridylmethyl]ethylenediamine-N,N -diacetic acid (H 4 bpeda) was synthesised using an improved procedure which requires a reduced number of steps and leads to a higher yield with respect to the published procedure. It was obtained in three steps from diethylpyridine-2,6-dicarboxylate and commercially available ethylenediamine-N,N -diacetic acid with a total yield of ∼20%. The crystal structure of the hexa-protonated form of the ligand which was determined by X-ray diffraction shows that the four carboxylates and the two amines are protonated. The crystal structure of the polynuclear complex [Gd(bpeda)(H 2 O) 2 ] 3 [Gd(H 2 O) 6 ] 2 Cl 3 (2), isolated by slow evaporation of a 1 : 1 mixture of GdCl 3 and H 4 bpeda at pH ∼ 1, was determined by X-ray diffraction. In complex 2 three [Gd(bpeda)(H 2 O) 2 ] units, containing a Gd(III) ion ten-coordinated by the octadentate bpeda and two water molecules, are connected in a pentametallic structure by two hexa-aquo Gd 3+ cations through four carboxylato bridges. The protonation constants (pK a1 = 2.9(1), pK a2 = 3.5(1), pK a3 = 5.2(2), and pK a4 = 8.5(1)) and the stability constants of the complexes formed between Gd(III) and Ca(II) ions and H 4 bpeda (log b GdL = 15.1(3); log b CaL = 9.4(1)) were determined by potentiometric titration. The unexpected decrease in the stability of the gadolinium complex and of the calcium complex of the octadentate ligand bpeda 4− with respect to the hexadentate ligand edta 4− has been interpreted in terms of an overall lower contribution to stability of the metal-nitrogen interactions. The EPR spectra display very broad lines (apparent DH pp ∼800-1200 G at X-band and 90-110 G at Q-band depending on the temperature), indicating a rapid transverse electron spin relaxation. At X-band, Gd(bpeda) is among the fastest relaxing Gd 3+ complexes to date suggesting that the presence of pyridinecarboxylate chelating groups in itself does not lead to slow electron relaxation.