Publications de Alain Borel | EPFL Graph Search

ChemCalc: a building block for tomorrow’s chemical infrastructure

Web services, as an aspect of cloud computing, are becoming an important part of the general IT infrastructure, and scientific computing is no exception to this trend. We propose a simple approach to develop chemical web services, through which servers cou ...

2013

Electronic fine structure calculation of [Gd(DOTA)(H2O)]- using LF-DFT: The zero field splitting

Lothar Helm, Alain Borel

Zerfo field splitting plays an important role in determining the electron spin relaxation of Gd(III) in solution. We understand the ZFS as an effect depending on the f electron structure and treat it in the framework of ligand field-density functional theo ...

2012

Multiple Frequency and Variable Temperature EPR study of Gd(III) polyaminocarboxylates: analysis and comparison of the magnetically dilute powder and the frozen solution spectra

André Merbach, Lothar Helm, Alain Borel

An Electron Paramagnetic Resonance (EPR) study of glasses and magnetically dilute powders of [Gd(DTPA)(H2O)]2−, [Gd(DOTA)(H2O)]-, and macromolecular Gd-P792 complexes was carried out at X-, Q-band and 240 GHz DTPA=diethylenetriaminepentaacetato; DOTA=1,4,7 ...

Wiley-VHCA AG2009

A ruthenium-based metallostar: synthesis, sensitized luminescence and 1H relaxivity

Jean-Claude Bünzli, Loïck Moriggi, Lothar Helm, Alain Borel, Annina Aebischer

Ru-based metallostars Na4{Ru[Ln2bpy-DTTA2(H2O)4]3} (Ln = Y, Gd, and Eu) have been self-assembled in aqueous solution and their relaxivity and optical properties unravelled. The ynthesis and the purification of the new, highly stable heptametallic entities ...

2009

Towards the Rational Design of MRI Contrast Agents: Electron Spin Relaxation Is Largely Unaffected by the Coordination Geometry of Gadolinium(III)-DOTA-Type Complexes

Loïck Moriggi, Lothar Helm, Alain Borel

Electron-spin relaxation is one of the determining factors in the efficacy of MRI contrast agents. Of all the parameters involved in determining relaxivity it remains the least well understood, particularly as it relates to the structure of the complex. On ...

2008

Design of Gd(III)-Based Magnetic Resonance Imaging Contrast Agents: Static and Transient Zero-Field Splitting Contributions to the Electronic Relaxation and Their Impact on Relaxivity

André Merbach, Loïck Moriggi, Lothar Helm, Alain Borel

A multiple-frequency (9.4-325 GHz) and variable-temperature (276-320 K) electron paramagnetic resonance (EPR) study on low molecular weight gadolinium(III) complexes for potential use as magnetic resonance imaging (MRI) contrast agents has been performed. ...

2007

Stochastic Liouville equation treatment of the electron paramagnetic resonance line shape of an S-state ion in solution

Alain Borel

The current approaches used for the analysis of electron paramagnetic resonance spectra of Gd3+ complexes suffer from a number of drawbacks. Even the elaborate model of [Rast et al., J. Chem. Phys. 113, 8724 (2000)] where the electron spin relaxation is ex ...

2007

Multiple-frequency EPR spectra of two aqueous Gd3+ polyaminopolypyridinecarboxylate complexes: a study of high field effects

Lothar Helm, Alain Borel, Sabrina Laus, Marinella Mazzanti

In the search for highly efficient magnetic resonance imaging contrast agents, polyaminopolypyridinecarboxylate complexes of Gd3+ have shown unusual properties with both very rapid and very slow electron spin relaxation in solution observed by electron par ...

2007

Multiplets of free d- and f-metal ions: A systematic DFT study

Alain Borel

In this work we apply in a systematic way our multi-determinantal model to calculate the fine structure of the whole atomic multiplet manifold. The key feature of this approach is the explicit treatment of near-degeneracy correlation using ad hoc configura ...

2006

A Theoretical Characterization of Covalency in Rare Earth Complexes through Their Absorption Electronic Properties: f-f Transitions

Alain Borel

Experimental uncertainties concerning the coordination mode of trivalent plutonium in concentrated LiCl have led us to theoretically evaluate the f-f transitions of a series of rare earth aquo and chloro complexes. The calculation of Pr(III), U(III), Np(II ...

2006

A High-Frequency EPR Study of Frozen Solutions of Gd(III) Complexes: Straightforward Determination of the Zero-Field Splitting Parameters and Simulation of the NMRD Profiles

André Merbach, Lothar Helm, Alain Borel

Gd(III) (S = 7/2) polyaminocarboxylates, used as contrast agents for Magnetic Resonance Imaging (MRI), were studied in frozen solutions by High-Frequency-High-Field Electron Paramagnetic Resonance (HF-EPR). EPR spectra recorded at 240 GHz and temperatures ...

2006

A Starburst-Shaped Heterometallic Compound Incorporating Six Densely Packed Gd3+ Ions

André Merbach, Alain Borel, Eva Jakab Toth, Joao Bruno Livramento Fig.

The heterotritopic ligand [bpy(DTTA)2]8- has two diethylenediamine-tetraacetate units for selective lanthanide(III) coordination and one bipyridine function for selective FeII coordination. In aqueous solution and in the presence of these metals, the ligan ...

2006

Water-Soluble Gadofullerenes: Toward High-Relaxivity, pH-Responsive MRI Contrast Agents

André Merbach, Lothar Helm, Alain Borel, Eva Jakab Toth

The water-soluble endohedral gadofullerene derivatives, Gd@C60(OH)x and Gd@C60[C(COOH)2]10, have been characterized with regard to their MRI contrast agent properties. Water-proton relaxivities have been measured in aqueous solution at variable temperature ...

2005

High Relaxivity Confined to a Small Molecular Space: A Metallostar-Based, Potential MRI Contrast Agent

André Merbach, Alain Borel, Eva Jakab Toth, Joao Bruno Livramento Fig.

Good things come in small packages: For its moderate molecular weight, the metallostar complex [Fe{Gd2L(H2O)4}3]4− (see picture; L is a bipyridine–poly(aminocarboxylate) derivative) displays exceptionally high proton relaxivity, which is explained in terms ...

Wiley-VCH Verlag GmbH2005

The effect of pyridinecarboxylate chelating groups on the stability and electronic relaxation of gadolinium complexes

André Merbach, Lothar Helm, Alain Borel, Marinella Mazzanti

The ligand N,N'-bis[6-carboxy-2-pyridylmethyl]ethylenediamine-N,N'-diacetic acid (H4bpeda) was synthesized using an improved procedure which requires a reduced no. of steps and leads to a higher yield with respect to the published procedure. It was obtaine ...

2005