A homogeneous series of polynuclear structures containing from 2 to 6 GdAAZTA complexes(AAZTA=6-amino-6-methylperhydro-1,4-diazepine tetraacetic acid)were synthesized covering a broad range of molecular weights,ca.120...A homogeneous series of polynuclear structures containing from 2 to 6 GdAAZTA complexes(AAZTA=6-amino-6-methylperhydro-1,4-diazepine tetraacetic acid)were synthesized covering a broad range of molecular weights,ca.1200-6000 Da.A frequency and temperature dependent 1H and 17O NMR relaxometric study on the Gd(III)polynuclear complexes clearly highlights a considerable gain of relaxivity(per Gd)passing from the monomer to the hexanuclear complex,with an enhancement of+370%at 1.5 T and 298 K(+470%at 310 K).In particular,the relaxivity of the hexamer reaches a remarkable value of 28.2 mM^(−1)s^(−1)at 1.5 T and 298 K(23.8 mM^(−1)s^(−1)at 310 K).The NMR study,supported by DFT calculations,allows analysis in detail of the dependence of the rotational dynamics on the size and molecular geometry of the multimers,considering both the global tumbling of the system and the local motions of the monomer units.In addition,T1-weighted phantom MR-images at 1,3 and 7 T on selected polynuclear complexes highlighted the effective signal enhancement of the new MRI probes at clinically relevant magnetic field strengths in comparison with the clinically approved contrast agent ProHance®.Finally,the results obtained enable us to highlight effective strategies for relaxation enhancement,each suitable for a well-defined range of applied magnetic field strength.展开更多
The substitution of an acetate pendant arm on the endocyclic or exocyclic nitrogen atoms of AAZTA with a hydroxybenzyl group results in two regioisomeric Gd(III)complexes with different hydration numbers,thermodynamic...The substitution of an acetate pendant arm on the endocyclic or exocyclic nitrogen atoms of AAZTA with a hydroxybenzyl group results in two regioisomeric Gd(III)complexes with different hydration numbers,thermodynamic stabilities differing by 5.5 log K units and remarkably different kinetic inertness.The ligand functionalized with the phenol group on the exocyclic N atom(AAZ3A-exoHB)forms a Gd(III)complex with remarkably high stability(log K_(GdL)=25.06)thanks to the tight coordination of the phenol group,which presents a rather low protonation constant(log K_(GdHL)=3.22).展开更多
基金the financial support from Universitàdel Piemonte Orientale(Ricerca locale 2019)This work was carried out within the framework of the COST CA15209 Action‘European Network on NMR Relaxometry’.
文摘A homogeneous series of polynuclear structures containing from 2 to 6 GdAAZTA complexes(AAZTA=6-amino-6-methylperhydro-1,4-diazepine tetraacetic acid)were synthesized covering a broad range of molecular weights,ca.1200-6000 Da.A frequency and temperature dependent 1H and 17O NMR relaxometric study on the Gd(III)polynuclear complexes clearly highlights a considerable gain of relaxivity(per Gd)passing from the monomer to the hexanuclear complex,with an enhancement of+370%at 1.5 T and 298 K(+470%at 310 K).In particular,the relaxivity of the hexamer reaches a remarkable value of 28.2 mM^(−1)s^(−1)at 1.5 T and 298 K(23.8 mM^(−1)s^(−1)at 310 K).The NMR study,supported by DFT calculations,allows analysis in detail of the dependence of the rotational dynamics on the size and molecular geometry of the multimers,considering both the global tumbling of the system and the local motions of the monomer units.In addition,T1-weighted phantom MR-images at 1,3 and 7 T on selected polynuclear complexes highlighted the effective signal enhancement of the new MRI probes at clinically relevant magnetic field strengths in comparison with the clinically approved contrast agent ProHance®.Finally,the results obtained enable us to highlight effective strategies for relaxation enhancement,each suitable for a well-defined range of applied magnetic field strength.
文摘The substitution of an acetate pendant arm on the endocyclic or exocyclic nitrogen atoms of AAZTA with a hydroxybenzyl group results in two regioisomeric Gd(III)complexes with different hydration numbers,thermodynamic stabilities differing by 5.5 log K units and remarkably different kinetic inertness.The ligand functionalized with the phenol group on the exocyclic N atom(AAZ3A-exoHB)forms a Gd(III)complex with remarkably high stability(log K_(GdL)=25.06)thanks to the tight coordination of the phenol group,which presents a rather low protonation constant(log K_(GdHL)=3.22).
