NMR approach of the electronic properties of the hydrated trivalent rare earth ions in solution

A Gadolinium Complex Confined in Silica Nanoparticles as a Highly Efficient T1/T2 MRI Contrast Agent

“…complexes. Indeed, the relaxivity r 1 has a nearly constant, small value of about 0.5 s À1 mm À1 , characteristic of the very short electronic relaxation time of the Dy 3+ ion, [14,18] whereas r 2 rises sharply with frequency as the Dy 3+ Curie spin, [18] since it is 5.4, 137, and 182 s À1 mm À1 at the above frequencies, respectively.…”

“…This interpretation is further supported by the relaxivities measured at ν I =50, 500, and 800 MHz for the large nanoparticles (NPDy50, diameter=50 nm) doped with [Dy(ebpatcn)(H 2 O)] complexes. Indeed, the relaxivity r 1 has a nearly constant, small value of about 0.5 s −1 m M −1 , characteristic of the very short electronic relaxation time of the Dy 3+ ion,14, 18 whereas r 2 rises sharply with frequency as the Dy 3+ Curie spin,18 since it is 5.4, 137, and 182 s −1 m M −1 at the above frequencies, respectively.…”

“…Above 500 MHz, r 2 exceeds 150 s À1 mm À1 in the case of the large NPs and even 227 s À1 mm À1 in the case of the small ones. Here, using the Gd III concentration in the solution measured either from the NMR paramagnetic susceptibility shift [14] or by ICPMS, [11] the NPGd50 were shown to contain about 1,000 [GdA For instance, NPGd60 (diameter = 60 AE 5 nm) contains about 3,000 Gd chelates, whereas the incorporation of 1000 chelates produces NPGd50 (diameter 50 AE 5 nm). Accordingly, when passing from NPGd50 to NPGd60, the relaxivities r 1 per NP increase from 3.3 10 4 to 7,2 10 4 s À1 ·A C H T U N G T R E N N U N G (mm of NP) À1 at 35 MHz, near their local maxima, and the relaxivities r 2 rise from 1.4 10 5 to 2.7 10 5 s À1 ·A C H T U N G T R E N N U N G (mm of NP) À1 above 400 MHz.…”

“…Above 500 MHz, r 2 exceeds 150 s −1 m M −1 in the case of the large NPs and even 227 s −1 m M −1 in the case of the small ones. Here, using the Gd III concentration in the solution measured either from the NMR paramagnetic susceptibility shift14 or by ICPMS,11 the NPGd50 were shown to contain about 1,000 [Gd(ebpatcn)(H 2 O)] complexes (see the Supporting Information) so that their relaxivities on a per NP basis are r 1 ≅1,9×10 4 s −1 ⋅(m M of NP) −1 at 50 MHz and r 2 >1,5×10 5 s −1 ⋅(m M of NP) −1 for above 500 MHz. Larger NPs are obtained when a larger number of complexes are incorporated in the NP (see the Supporting Information).…”

Determination of the rate of a fast exchanging coordinated molecule in a lanthanide(iii) complex by proton NMR

“…Let m eff be the Ln 3+ effective electronic magnetic moment. 16 For both IS and OS relaxation mechanisms, the Curie and SBM terms are proportional to [o I m 2 eff /(k B T)] 2 and g 2 I g 2 J m 2 B J(J + 1), respectively. The Curie terms depend on the equilibrium spatial distribution and random motion of the Ln 3+ ion with respect to the observed proton.…”