Field-dependent proton relaxation in aqueous solutions of some manganese(II) complexes: a new interpretation

Kruk, Danuta; Kowalewski, Józef

doi:10.1007/s00775-003-0444-9

Cited by 24 publications

(21 citation statements)

References 15 publications

(59 reference statements)

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“…To calculate the IS relaxivity, we used the following IS parameters: The number q = 1 of metal-bound water molecules introduced in Equation (6) was derived from independent luminescence decay studies. The Gd-proton distance r H = 3.23 Å used to calculate 1/T 1M according to Equations (18) and (19) was taken to be in the range of the values [5,73] generally obtained for the Gd III complexes and compatible with the known X-rays crystal structures. The lifetime t M was determined so as to be compatible with general features of the experimental longitudinal and transverse relaxivities r 1 and r 2 of the water protons.…”

Section: Nmrd Interpretationmentioning

confidence: 99%

“…Then, the theoretical relaxivity r 1 can no longer be expressed in terms of simple analytical expressions as in the SBM approach. It has to be computed either by setting up and inverting the very large matrices of the superoperator Liouville formalism of the general slow-motion theory [19] or by numerical simulation. [20][21][22] Rather than using the questionable SBM formalism at low field, Troughton et al [60] contented themselves with interpreting the experimental relaxivity above 0.2 T. Indeed, in this "high"-field region, it depends practically only on the longitudinal electronic relaxation rate 1/T 1e , which is given by general expressions of the McLachlan type.…”

Section: Relaxivity Theorymentioning

confidence: 99%

“…[5,18] Though large efforts have been devoted to the understanding of the molecular parameters that govern the relaxivity, the mechanisms and the coordination properties underlying the electronic relaxation of Gd III complexes still remain poorly understood. [19][20][21][22] This prevents the ligand design required to optimise the electronic relaxation, which becomes especially important in the new generation macromolecular complexes with long rotational correlation times.…”

Section: A C H T U N G T R E N N U N G Ane Framework Affords the Monomentioning

confidence: 99%

“…Step three is to check whether the experimental water proton relaxivity r 1 is satisfactorily represented by the usual Equations (5), (6), (18), (19), and (7)- (13), but with the relaxation rates 1/T 1e and 1/T 2e,i given by Equations (8)-(10).…”

mentioning

confidence: 99%

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Lanthanide Complexes of a Picolinate Ligand Derived from 1,4,7‐Triazacyclononane with Potential Application in Magnetic Resonance Imaging and Time‐Resolved Luminescence Imaging

Nonat

Gateau

Fries

et al. 2006

Chemistry A European J

107

101

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The new potentially octadentate ligand, 1-(carboxymethyl)-4,7-bis[(6-carboxypyridin-2-yl)methyl]-1,4,7-triazacyclononane (H(3)bpatcn), in which two picolinate arms and one acetate arm are connected to the 1,4,7-triazacyclonane core, has been prepared. Potentiometric studies show an increased stability of the Gd(III) complex of H(3)bpatcn (logK(GdL)=15.8(2)) with respect to the Gd(III) complex of the analogous ligand 1,4,7-triazacyclononane-N,N',N''-triacetic acid (H(3)nota) (logK(GdL)=13.7), associated with an increased selectivity of H(3)bpatcn for gadolinium over calcium. The H(3)bpatcn ligand sensitises the terbium ion very efficiently, leading to a long-lived and highly luminescent terbium complex (quantum yield=43 %), in spite of the presence of a coordinated water molecule. (1)H proton NMR studies indicate that the metal ion is rigidly encapsulated by the three arms of the octadentate ligand H(3)bpatcn and that the macrocycle framework remains bound (through the five nitrogen and the three oxygen atoms) even at high temperature. A new theoretical method for interpreting the water proton relaxivity is presented. It is based on recent progresses in the description of the electronic spin relaxation and on an auxiliary probe solute. It replaces the Solomon, Bloembergen and Morgan (SBM) framework, which is questionable at low field, while avoiding resorting to simulations and/or sophisticated theories with additional unknown zero-field splitting (ZFS) parameters. The inclusion of two picolinate groups on a triazacyclononane framework affords the mono-aquo gadolinium complex [Gd(bpatcn)(H(2)O)] with favourable electron-relaxation properties (tau(eff)(S0)=125 ps). The optimisation of the electronic relaxation by ligand design is especially important to achieve high relaxivity in the new generation macromolecular complexes with long rotational correlation times.

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Section: Nmrd Interpretationmentioning

confidence: 99%

Section: Relaxivity Theorymentioning

confidence: 99%

Section: A C H T U N G T R E N N U N G Ane Framework Affords the Monomentioning

confidence: 99%

mentioning

confidence: 99%

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Lanthanide Complexes of a Picolinate Ligand Derived from 1,4,7‐Triazacyclononane with Potential Application in Magnetic Resonance Imaging and Time‐Resolved Luminescence Imaging

Nonat

Gateau

Fries

et al. 2006

Chemistry A European J

107

101

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“…The motion modulating the orientation of the molecular frame and the spin relaxation can be still treated as uncorrelated, because of timescale separation, and the corresponding correlation functions can be separated. This motional regime has been discussed in the context of electron spin relaxation and rotational modulations of the I−S dipole-dipole interaction in [28] and called the "moderatory slow rotation". The treatment breaks down starting from the high field limit since the S spin relaxation is here slower than at low field and therefore more close to the timescale of the motion responsible for the momentary orientation of the molecular and the laboratory frames.…”

Section: And Hmentioning

confidence: 99%

Field Dependent Electron and Quadrupole Spin Relaxation: A Unified Treatment

Kruk

2007

Acta Phys. Pol. A

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This article reviews recent theoretical treatments of field dependent relaxation processes in complex systems containing mutually coupled dipolar, quadrupole, and electron spins. The presented approaches are based on an analogy between the Hamiltonian formalisms for quadrupole and zero field splitting interactions. Limitations of the presented treatments, resulting from the validity conditions of the second-order perturbation theory are discussed in detail.

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Manganese(II) Complexes as Potential Contrast Agents for MRI

2012

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Mn2+ has five unpaired d electrons, a long electronic relaxation time, and labile water exchange, which make it an attractive alternative to Gd3+ in the design of contrast agents for medical Magnetic Resonance Imaging. In order to ensure in vivo safety and high contrast agent efficiency, the Mn2+ ion has to be chelated by a ligand that provides high thermodynamic stability and kinetic inertness of the complex and has to have at least one free coordination site for a water molecule. Unfortunately, these two requirements are contradictory, as lower denticity of the ligands, which leads to more inner‐sphere water molecules often implies a decreased stability of the complex, and, therefore, it is necessary to find a balance between both requirements. In the last decade, a large amount of experimental data has been collected to characterize the physico‐chemical properties of Mn2+ chelates with variable ligand structures. They now allow for establishing trends of how the ligand structure, the rigidity of the ligand scaffold, and its donor–acceptor properties influence the thermodynamic, kinetic, and redox stability of the Mn2+ complex. This microreview surveys the current literature in this field.

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Field-dependent proton relaxation in aqueous solutions of some manganese(II) complexes: a new interpretation

Cited by 24 publications

References 15 publications

Lanthanide Complexes of a Picolinate Ligand Derived from 1,4,7‐Triazacyclononane with Potential Application in Magnetic Resonance Imaging and Time‐Resolved Luminescence Imaging

Lanthanide Complexes of a Picolinate Ligand Derived from 1,4,7‐Triazacyclononane with Potential Application in Magnetic Resonance Imaging and Time‐Resolved Luminescence Imaging

Field Dependent Electron and Quadrupole Spin Relaxation: A Unified Treatment

Manganese(II) Complexes as Potential Contrast Agents for MRI

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