André Merbach | EPFL Graph Search

André Merbach was born in Lausanne in 1940. He studied at the Polytechnical School of the University of Lausanne (Pelet and A3E2PL Awards), where he obtained in 1962 his degree in Chemical Engineering with a diploma research work in organic chemistry. In 1964, the University of Lausanne awarded him a PhD for his research on quaternary solubility systems with formation of mixed crystals. He spent then a Postdoctoral Fellowship in the Lawrence Radiation Laboratory at the University of California, Berkeley, where he studied the ionisation of strong electrolytes by NMR.

Upon his return in 1965 to the Institute of Inorganic and Analytical Chemistry at the University of Lausanne, he was asked to create a research and teaching program in Coordination Chemistry. He was appointed Assistant Professor in 1971.

In 1973, the Swiss Chemical Society awarded him the Werner Prize and Medal for his research on the structure, the stability and the dynamics of metal halogen adducts by NMR and, the same year, was nominated Professor of Inorganic and Analytical Chemistry.

He was a member of the Swiss National Foundation for Scientific Research in the division of Mathematics, Natural Sciences and Engineering from 1985 until 1996. He represents Switzerland on the COST Chemistry Technical Committee (European Co-operation in the Field of Scientific and Technical Research: 35 countries and 1000 research groups in chemistry) and has chaired this Committee from 1998 to 2000. He was the Chairman of the Management Committee of the COST Action D6 on Chemical Processes and Reactions under Extreme or Non-Classic Conditions (1992-1997).

He has organised the XXIXth International Conference in Coordination Chemistry (ICCC) in Lausanne in 1992. He has been awarded an honoris causa doctorate from the Lajos Kossuth University of Debrecen (Hungary) in 1993 for his work on elucidating reaction mechanisms in coordination chemistry utilising high pressure NMR. He has been called at the presidency of the Swiss Chemical Society (2001-2004). The University of Geneva awarded him an honoris causa doctorate in 2003.

The Periodic Table and Kinetics?

Lothar Helm, André Merbach

Mendeleev in his first publication ordered the chemical elements following an apparent periodicity of properties such as atomic volume and valence. The reactivity of the elements was only studied systematically many years later. To illustrate the systematic variation of kinetics across the periodic table we compare water residence times for monoatomic ions in aqueous solution. A tremendous variation of tau(H2O) by over 20 orders of magnitude is found, ranging from similar to 10 ps to about 200 years. Apart from some small +2 and +3 cations, all main group elements have very short residence times

2019

Metal Complexes as MRI Contrast Enhancement Agents

Lothar Helm, Eva Jakab Toth, André Merbach

Magnetic resonance imaging is one of the most efficient diagnostic modalities in clinical radiology and biomedical research. To enhance image contrast, paramagnetic complexes, mainly Gd3+ chelates, are used. Today, around one third of all medical MR images are generated with the use of a contrast medium and this number is expected to increase with the development of new applications and new agents. Recently, molecular imaging has emerged as a new area aiming at non-invasive visualisation of expression and function of bioactive molecules at the cellular level. Since any molecular imaging application requires a specific imaging probe, new chemical approaches become increasingly important. In this chapter, we discuss first proton relaxivity, the parameter that directly translates to the effectiveness of an MRI contrast agent. Many microscopic factors, including the hydration number, the water exchange rate, the rotational dynamics, as well as the electron spin relaxation, influence proton relaxivity for Gd3+ complexes. We show how the structure, the charge or the size of the chelate affects these factors. We also review the different strategies derived to obtain high-relaxivity probes. Non-toxicity of these agents is primordial for their application; therefore we also address the main physico-chemical aspects related to the in vivo stability of Gd3+-based agents, such as thermodynamic stability and kinetic inertness. The second part of the chapter is devoted to new-generation MRI contrast media, such as smart or responsive contrast agents that are capable of reporting on the physico-chemical environment in tissues. Among the huge number of systems reported in the field of smart MRI probes, we focus only on sensing of pH, redox state and metal ions. Many pathologies, such as stroke, infections, kidney disease and cancer are associated with significant pH variations. Accurate, high resolution, in vivo MRI pH mapping would be of great interest not only for diagnostic purposes but also for monitoring disease progression, choice and response to therapy. The partial oxygen pressure, pO2, is also significant in metabolic processes of cells, and its variation from normal values often indicates pathologies (ischemic diseases, strokes, tumors). As for metal ions, several of them play a crucial role in biological processes, whereas others are toxic. Alteration of the metal concentration in the body can often be correlated to disease states. Our objective here is to illustrate, via a few selected examples of Gd3+-based or Paramagnetic Chemical Exchange Saturation Transfer (PARACEST) agents, the major design principles in coordination chemistry to derive smart MRI probes using lanthanide complexes.

Elsevier2015

Metal Complexes as MRI Contrast Enhancement Agents

Lothar Helm, Eva Jakab Toth, André Merbach

Elsevier2015