Quantum Chemical Investigation on Indole: Vibrational
Force Field and Theoretical Determination of Its Aqueous p<i>K</i><sub>a</sub> Value
Andrea Pietropolli Charmet
Giuseppe Quartarone
Lucio Ronchin
Claudio Tortato
Andrea Vavasori
10.1021/jp4049692.s001
https://acs.figshare.com/articles/journal_contribution/Quantum_Chemical_Investigation_on_Indole_Vibrational_Force_Field_and_Theoretical_Determination_of_Its_Aqueous_p_i_K_i_sub_a_sub_Value/2389111
Indole and its derivatives are molecules
which play important roles
in different fields, from biology to pharmacology. Here we report
a thorough investigation on the anharmonic force fields of indole
as well as the ab initio determinations of its gas phase basicity
and aqueous p<i>K</i><sub>a</sub> value. For the geometry
optimizations, the calculations have been performed using both density
functional (DFT) and second-order Møller–Plesset (MP2)
levels of theory employing different basis sets. Anharmonic force
fields have been obtained employing both the B3LYP and the B97-1 functionals
and an hybrid approach: the best agreement to the experimental data
has been determined employing the B3LYP functional combined with the
recently developed N07D basis set (mean unsigned error, MUE, of 5.1
cm<sup>–1</sup> and a root-mean-square error, RMSE, of 7.2
cm<sup>–1</sup>). Gas phase basicity and proton affinity have
been computed employing several computational schemes, namely the
G3 and G4 Gaussian models, the complete basis set (CBS) extrapolation
methods of Petersson and co-workers, several DFT calculations, and
different hybrid extrapolation schemes based on combining single-point
energy calculations performed at MP2 as well as at coupled cluster
level of theory with single, double and perturbative triple excitations,
CCSD(T). Regarding the aqueous p<i>K</i><sub>a</sub> computations,
two implicit solvation models (SMD and SM8) have been employed to
determine the free energy of solvation and the corresponding p<i>K</i><sub>a</sub> value.
2013-08-08 00:00:00
Anharmonic force fields
solvation
Vibrational Force Field
quantum Chemical Investigation
CCSD
CBS
pKa value
MP
cm
MUE
SMD
Aqueous pKa ValueIndole
gas phase basicity
scheme
DFT
SM
calculation
anharmonic force fields
RMSE
ab initio determinations
N 07D basis
B 3LYP
extrapolation
model