The use of the complexes of the compounds of general formula (I) with paramagnetic bi-trivalent metal ions selected from the group consisting of Fe?(2+), Fe(3+), Cu(2+), Cr(3+), Gd(3+), Eu(3+), Dy(3+), Yb(3+) or Mn(2+)¿, as well as the salts thereof with physiologically compatible organic bases selected from primary, secondary, tertiary amines or basic amino acids, or with inorganic bases whose cations are sodium, potassium, magnesium, calcium or mixtures thereof. In formula (I) X-L-Y wherein: X is the residue of a polyaminopolycarboxylic ligand and the derivatives thereof, selected from the group consisting of: EDTA, DTPA, DOTA, DO3A, BOPTA; Y is the derivative of a bile acid selected from the group consisting of residues of cholic, chenodeoxycholic, deoxycholic, ursodeoxycholic, lithocholic acids, both as they are and functionalized at the positions having the hydroxy group as the reactive group; L is a chain linked at any position of X and the C-3, C-7, C-12 positions of Y, for the preparation of diagnostic formulations for the imaging of the blood system of the human and animal body, by means of nuclear magnetic resonance; novel compounds of general formula (I) and the diagnostic compositions containing them.