Granting
institution:
ERA-Chemistry
(administered by OTKA, the Scientific Research Fund of Hungary)
Grant no.:
NN
81072
Title of the
proposal:
Tunneling
in novel hydroxycarbenes
Duration:
Three
years (2009–2012)
Principal
investigators:
Attila G. Császár and Peter R. Schreiner
(Giessen, Germany)
Project description:
Building
on the complementary backgrounds and expertise of the Giessen
(experimental organic chemists and spectroscopists) and the Budapest
(computational quantum chemists) groups, a joint program is proposed that
uniquely combines the preparation, detection, and spectroscopic as well as
computational characterization of designed novel carbenes
exhibiting enhanced hydrogen and possibly heavy-atom tunnelling under large
barriers at low cryogenic temperatures (down to 6 K). The very low temperatures and the noble gas
environment of cryogenic matrices are ideally suited for quantum chemical
reaction rate and tunnelling (quantum reaction dynamics) studies on single
ground-state surfaces. The proposed
full- and reduced-dimensionality reaction dynamics computations are expected to
guide new experiments and, when augmented with sophisticated electronic
structure computations, should shed light on the factors that govern enhanced
quantum mechanical tunnelling under large barriers near 0 K on timescales of
minutes to days.
Questions
the proposed research aims to answer include:
(a)
how do electronic substituent effects alter the rates
of H-tunnelling in novel unsaturated hydroxycarbenes;
(b)
how large a barrier can be afforded for observable
H-tunnelling;
(c)
can hydrogen bonding be used to tune the rate of H-tunneling?
Novel aspects of the proposed
research program include:
(a) systematic
preparation of a series of electronically related substituted, currently
unknown hydroxycarbenes;
(b) development
of synthetic routes to substituted hydroxycarbenes;
(c) studying
the electronic effects on tunnelling, utilizing the most advanced levels of
quantum chemistry (including ground-breaking electronic structure, nuclear
motion, and reaction dynamics computations);
(d) variational
determination of rovibrational spectra of carbenes containing five or more atoms and/or multiple
minima on their PES;
(e) quantum
chemical computation of microcanonical rate constants
based on the availability of a time-independent machinery similar to that which
allows determination of a nearly complete set of stationary
rotational-vibrational wave functions and energy levels.
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