Relaxation enhancement of water protons by manganese(III) porphyrins: influence of porphyrin aggregation

Relaxometric Investigation of Functional Group Placement on MnTPP Derivatives Supports the Role of the Molecular Electrostatic Potential Maps as a Tool to Design New Metalloporphyrins with Larger Relaxivities

“…The T1 NMRD profile of MnT(4-S)PP is qualitatively and quantitatively in agreement with previously published reports [3]. The authors also reported that the T1 NMRD profile of MnT(4-S)PP was the same as MnT(4-C)PP, which has a carboxylate instead of a sulfonato group in the para position.…”

“…In the context of MRI (magnetic resonance imaging) contrast agents, there has been much effort in studying the relaxometric properties of metalloporphyrins in an effort to understand and increase their water proton relaxation efficiencies [3][4][5]. It has been suggested, based on molecular electrostatic potential (MEP) calculations [6], that substitution of the sulfonato group in the para position in MnT(4-S)PP with carboxylate groups in the ortho position of the phenyl rings attached to the meso carbons, MnT(2-C)PP, may result in an increase in the water proton relaxation enhancement of the metalloporphyrin.…”

The gadolinium complexes with polyoxometalates as potential MRI contrast agents

“…Moreover, the relaxivities of Gd(BW 11 ) 2 and Gd(CuW 11 ) 2 were much higher than that of Gd(SiW 11 ) 2 and Gd(PW 11 ) 2 [21,22], and this result can be rationalized that the larger negative charge on the complex will orient water molecules with hydrogen atoms closer to the complex. Similar effect was observed in other heteropoly complexes [26] and metal porphyrins [27].…”

Mn(II)-monosubstituted polyoxometalates as candidates for contrast agents in magnetic resonance imaging

“…Those may be attributed to (a) a longer rotational correlation time due to their higher molecular weight and the rigidity of their structure and (b) a shorter distance between the inner-sphere water molecule and Mn stemming from the larger negative charge. Similar effect was observed in other heteropoly complexes [37] and metal porphyrins [38].…”