Structure and Dynamics of Lanthanide Complexes of Triethylenetetramine‐N,N,N′,N″,N′′′,N′′′‐hexaacetic Acid (H₆ttha) and of Diamides H₄ttha(NHR) Derived from H₆ttha as Studied by NMR, NMRD, and EPR

Nano assembly and encapsulation; a versatile platform for slowing the rotation of polyanionic Gd3+‐based MRI contrast agents

“…(1,2,15) But, for GdTTHA 3− this contribution makes up almost the entire relaxivity of the chelate. (16) In every case this is expected to disappear once the chelate is encapsulated and no longer diffusing close to solvent water. GdDOTP 5− is a “second sphere chelate” – relaxivity arises from exchange of water between the bulk and a second hydration sphere of water molecules closely associated with the chelates through hydrogen bonding to the phosphonate groups.…”

“…GdDOTA − , GdTTHA 3− and GdDOTP 5− were prepared by previously published methods. (16,23,24) Silica nanoparticles were purchased from Nissan chemicals Snowtex O type as a 20.2 w/w suspension in water (pH 3.5).…”

Lanthanide(III) Complexes of Phosphorus Acid Analogues of H4DOTA as Model Compounds for the Evaluation of the Second‐Sphere Hydration

“…[52] and H 8 DOTP due to the lack of an inner-sphere water molecule, which leads to larger deformation of the complexes upon collision with solvent molecules. As a result, the electronic relaxation rates of the presently studied complexes are lower than that of [Gd(H 2 O)(DOTA)]…”

“…[52] The 1 H NMRD data were then fitted simultaneously with the X-band EPR data by using a set of equations suitable for complexes with an extended second hydration sphere. [22,27b] (5)…”

Joint analysis of ESR lineshapes and 1H NMRD profiles of DOTA-Gd derivatives by means of the slow motion theory

“…Powell et al 48 were the first to apply the SBM theory to the combined data sets for a number of Gd(III) complexes, with moderate success. Similar approaches were also adopted for other Gd(III) chelates by Toth et al 49 and, more recently ZithaBovens et al 50 The improved perturbation theory for electron spin relaxation 19,20 turned out to be more successful for the aqueous Gd(III) ion 21,22,51,52 and other small Gd(III) complexes. 53 Larger complexes, with electron spin relaxation outside of the Redfield limit, can be expected to be more difficult.…”