Home

Person

Lothar Helm

About
Privacy
Disclaimer

Graph Chatbot

Related publications (91)

Page 2 of 5

Complexation of [Gd(DTTA–Me)(H2O)2]− by Fluoride and Its Consequences to Water Exchange

Lothar Helm, Loïck Moriggi, Shima Karimi

The displacement of water molecule(s) from the inner coordination sphere of [Gd(DTTA–Me)(H2O)2]− (DTTA = ethylenetriamine-N,N,N″,N″-tetraacetate) by fluoride has been studied by multinuclear NMR relaxation (1H, 17O, 19F) and DFT calculations. Fluoride anio ...

American Chemical Society2016

A benzene-core trinuclear GdIII complex: towards the optimization of relaxivity for MRI contrast agent applications at high magnetic field

André Merbach, Lothar Helm, Joao Bruno Livramento Fig.

A novel ligand, H12L, based on a trimethylbenzene core bearing three methylenediethylenetriamine-N,N,N,N- tetraacetate moieties (–CH2DTTA4–) for Gd3+ chelation has been synthesized, and its trinuclear Gd3+ complex [Gd3L(H2O) 6]3– investigated with respect ...

2008

Hyperfine interactions in aqueous solution of Cr3+: an ab initio molecular dynamics study

Lothar Helm, Oleg Yazyev

We performed an ab initio mol. dynamics simulation of the paramagnetic transition metal ion Cr3+ in aq. soln. Isotropic hyperfine coupling consts. between the electron spin of the chromium ion and nuclear spins of all water mols. have been detd. for instan ...

2006

A Pyridine-Based Ligand with Two Hydrazine Functions for Lanthanide Chelation: Remarkable Kinetic Inertness for a Linear, Bishydrated Complex

Lothar Helm

To study the influence of hydrazine functions in the ligand skeleton, we designed the heptadentate HYD ligand (2,2',2 '',2 ''-(2,2'-(pyridine-2,6-diyl)bis(2-methylhydrazine-2,1,1-triyl)) tetraacetic acid) and compared the thermodynamic, kinetic, and relaxa ...

American Chemical Society2015

Early stages of radiation damage in graphite and carbon nanostructures: A first-principles molecular dynamics study

Ursula Röthlisberger, Lothar Helm, Oleg Yazyev, Ivano Tavernelli

Understanding radiation-induced defect formation in carbon materials is crucial for nuclear technology and for the manufacturing of nanostructures with desired properties. Using first-principles molecular dynamics, we perform a systematic study of the none ...

2007

Gd(III)-EPTPAC16, a new self-assembling potential liver MRI contrast agent: in vitro characterization and in vivo animal imaging studies

Lothar Helm

The recently reported amphiphilic chelate,

[Gd(EPTPAC_{16})(H_2O)]^{2-}

, forms supramolecular aggregates in aqueous solution by self-assembly of the monomers with a relaxometrically determined critical micellar concentration (CMC) of 0.34 mM. The effect ...

2008

Transient versus Static Electron Spin Relaxation in Mn2+ Complexes Relevant as MRI Contrast Agents

Lothar Helm

The zero,-field splitting (ZFS) parameters of the Mn(EDTA)(H2O).2H(2)O. and [Mn(MeNO(2)A)(H2O)].2H(2)O systems were estimated by using DFT and ab initio CASSCF/NEVPT2 calculations (EDTA = (ethane-1,2-41bis(azanetriy1))tetraatetate; MeNO2A = 2,2'-(7-m ...

American Chemical Society2016

Synthesis, complexation and NMR relaxation properties of Gd3+ complexes of Mes(DO3A)3

Lothar Helm, Pascal Miéville, Hugues Jaccard

Medium sized molecules endowed with multiple Gd3+ complexes are efficient high magnetic field MRI contrast agents. The novel ligand Mes(DO3A)3, presenting three DO3A (1,4,7,10-tetraazacyclododecane-N,N′,N′′-triacetatic acid) units grafted on the methyl pos ...

Royal Society of Chemistry2011

Mechanism of Pyridine-Ligand Exchanges at the Different Labile Sites of 3d Heterometallic and Mixed Valence μ3-oxo Trinuclear Clusters

Rosario Scopelliti, André Merbach, Lothar Helm, Fabrice Riblet

The syntheses and single crystal X-ray structural analysis of five novel hetero- and homometallic μ3-oxo trinuclear cluster with the formula [FeIII2MII(μ3-O)(μ-O2CCH3)6(4-Rpy)3] · x(4-Rpy) · y(CH3CN) where R ) Ph for 1(Fe2Mn),2(Fe2Fe), 3(Fe2Co), 4(Fe2Ni) a ...

2008

Optimization of gadolinium-based MRI contrast agents for high magnetic‑field applications

Lothar Helm

The search for higher spatial resolution and better sensitivity stimulates the development of high-field (3 T) and ultrahigh field (>3 T) MRI scanners. Gadolinium-based MRI contrast agents, commercial ones used in clinics, as well as recently developed mor ...

2010

Evaluation of Water Exchange Kinetics on [Ln(AAZTAPh–NO2)(H2O)q]x Complexes Using Proton Nuclear Magnetic Resonance

Lothar Helm, Shima Karimi

Water exchange kinetics on [Ln(AAZTAPh–NO2)(H2O)q]− (Ln = Gd3+, Dy3+, or Tm3+) were determined by 1H nuclear magnetic resonance (NMR) measurements. The number of inner-sphere water molecules was found to change from two to one when going from Dy3+ to Tm3+. ...

American Chemical Society2016

Positively Charged GdIII Cryptates: Slow, Associative Water Exchange

André Merbach, Lothar Helm

A combined variable-temp. and multiple field 17O NMR, EPR and NMRD study was performed for the 1st time on Gd(III) complexes of cryptand ligands, L1 and L2, where L1 contains three 2,2'-bipyridine units ([bpy.bpy.bpy]) and L2 is the disubstituted Me ester ...

2006

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

First in vivo MRI assessment of a self-assembled metallostar compound endowed with a remarkable high field relaxivity

André Merbach, Lothar Helm, Joao Bruno Livramento Fig.

{Fe[Gd2bpy(DTTA)2(H2O)4]3}4- is a self-assembled, metallostar-structured potential MRI contrast agent, with six efficiently relaxing Gd3+ centers confined into a small mol. space. Its proton relaxivity is particularly remarkable at very high magnetic field ...

2006

Gadolinium(III) ion in liquid water: structure, dynamics and magnetic interactions from first principles

Lothar Helm, Oleg Yazyev

We applied first principles molecular dynamics (MD) technique to study structure, dynamics, and magnetic interactions of the

Gd^{3+}

aqua ion dissolved in liquid water, a prototypical system for Gd-based complexes used as contrast agents for magnetic res ...

2007

Self-Assembled Nanomicelles as MRI Blood-Pool Contrast Agent

Lothar Helm, Anne-Sophie Chauvin

Gadolinium‐loaded nanomicelles show promise as future magnetic resonance imaging (MRI) contrast agents (CAs). Their increased size and high gadolinium (Gd) loading gives them an edge in proton relaxivity over smaller molecular Gd‐complexes. Their size and ...

2017

Nuclear Spin Relaxation Parameters of MRI Contrast Agents – Insight from Quantum Mechanical Calculations

Lothar Helm, Oleg Yazyev

Nuclear magnetic relaxation in the presence of paramagnetic centres has gained increasing interest in recent years partly due to its importance for contrast agents in magnetic resonance imaging. Rational design of new more efficient agents is possible as a ...

Wiley-Blackwell2008

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

André Merbach, Lothar Helm, Alain Borel

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

Dinuclear DOTA-Based Gd-III Chelates - Revisiting a Straightforward Strategy for Relaxivity Improvement

Lothar Helm, Shima Karimi

The need for magnetic resonance imaging (MRI) contrast agents with improved relaxivity maintains the development of new Gd-III chelates as an intensive and demanding field of research. In this work, we introduce the new dimeric chelators bis{1,4,7,10-tetra ...

Wiley-Blackwell2015

Kinetics of Yttrium-Ligand Complexation Monitored Using Hyperpolarized 89Y as a Model for Gadolinium in Contrast Agents

Geoffrey Bodenhausen, Lothar Helm, Sami Jannin, Pascal Miéville

Hyperpolarization by dissolution dynamic nuclear polarization (DNP) enhances Y-89 spin magnetization by 3 to 4 orders of magnitude and provides a way to monitor yttrium-ligand complexation "on the fly" by means of Y-89 NMR. In this communication, we show a ...

American Chemical Society2010