Page 14 - Strategies and Applications in Quantum Chemistry From Molecular Astrophysics to Molecular Engineer

At the Dawn of Quantum Chemistry:
The Role of Gaston Berthier

The active involvement of french scientists in the development of quantum chemistry started
rather late. Strangely, as is may seem to be, the native country of Louis de Broglie was for
a long time rather insensitive, if not resistant, to the possible significance and usefulness of
quantum theories for the development of chemical knowledge. The strangest opponents
were found, as can be guessed, among... the chemists. When we were students, the highly
popular series of courses leading to the Certificate of General Chemistry, which implied a
whole year of studies, hardly mentioned the existence of an electronic structure in atoms or
molecules. The situation was somewhat better in the Certificate of Physical Chemistry in
which the foundations of the quantum theory were studied in more details but even there the
practical incidence of the theory was limited to the case of the molecule. Nobody seemed
to have considered seriously that quantum theory could be of practical use in contributing to
the solution of chemical problems involving larger molecules.

It is on this background of indifference, if not of open animosity, that a group of young
research workers have undertaken, in the forties, the courageous, but rather risky for their
career, task of promoting the development of quantum chemistry in France, with the well-
conceived goal of exploring its capacity for studying realistic problems related to the
exploration of molecular properties, without any a priori limitation as to the size of the
molecules involved. Gaston Berthier was one of the earliest members of these local
pioneers.
A crucial event which greatly helped to stimulate the interest of the french scientific
community in the potentialities of quantum chemistry was the holding in Paris, in 1948, of
an international symposium on the methods, achievements and status of quantum
chemistry, which was attended by the most eminent specialists in this field. Suffice it to
mention the presence of Linus Pauling and Robert Mulliken. It is that year that Gaston
Berthier joined our group.
This happened at an interesting moment in our activities. These were concentrated at that
period on the structure and properties of polynuclear aromatic hydrocarbons, in particular
but far from exclusively, in relation with their carcinogenic activity. For purely historical
reasons, due to a large extent to the international prestige of Linus Pauling, the method
which we have been using for this sake, was the valence bond method. By 1948 we have
clearly realized the practical limitations of this procedure for the exploration of large
molecular systems and turned our attention to the molecular orbital method much more
suitable for such an endeavour. Berthier joined our laboratory just at this methodologically
turning point. He was thus immediately associated with what were the first works and
publications ever performed in France by this method. They dealt with the electronic
structure of aromatic hydrocarbons composed of four and five benzene rings, a tremendous
task at that time.

We may say that from that period on, Berthier became one of the best experts in France of
the molecular orbital method and an acknowledged pioneer in its application and
development.
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