4 research outputs found
Expanding and Testing a Computational Method for Predicting the Ground State Reduction Potentials of Organic Molecules on the Basis of Empirical Correlation to Experiment
A method for predicting the ground state reduction potentials
of
organic molecules on the basis of the correlation of computed energy
differences between the starting S<sub>0</sub> and one-electron-reduced
D<sub>0</sub> species with experimental reduction potentials in acetonitrile
has been expanded to cover 3.5 V of potential range and 74 compounds
across 6 broad families of molecules. Utilizing the conductor-like
polarizable continuum model of implicit solvent allows a global correlation
that is computationally efficient and has improved accuracy, with <i>r</i><sup>2</sup> > 0.98 in all cases and root mean square
deviation
errors of <90 mV (mean absolute deviations <70 mV) for either
B3LYP/6-311+GÂ(d,p) or B3LYP//6-31GÂ(d) with an appropriate choice of
radii (UAKS or UA0). The correlations are proven to be robust across
a wide range of structures and potentials, including four larger (27–28
heavy atoms) and more conformationally flexible photochromic molecules
not used in calibrating the correlation. The method is also proven
to be robust to a number of minor student “mistakes”
or methodological inconsistencies
Synthesis and Structural Investigation of an “Oxazinoquinolinespirohexadienone” That Only Exists as Its Long-Wavelength Ring-Opened Quinonimine Isomer
The spirocyclic oxazinoquinolinespirohexadienone (OSHD)
“photochromes”
are computationally predicted to be an attractive target as electron
deficient analogues of the perimidinespirohexadienone (PSHD) photochromes,
for eventual application as photochromic photooxidants. We have found
the literature method for their preparation unsuitable and present
an alternative synthesis. Unfortunately the product of this synthesis
is the long wavelength (LW) ring-opened quinonimine isomer of the
OSHD. We have found this isomer does not close to the spirocyclic
short wavelength isomer (SW) upon prolonged standing in the dark,
unlike other PSHD photochromes. The structure of this long wavelength
isomer was found by NMR and X-ray crystallography to be exclusively
the quinolinone (keto) tautomer, though experimental cyclic voltammetry
supported by our computational methodology indicates that the quinolinol
(enol) tautomer (not detected by other means) may be accessible through
a fast equilibrium lying far toward the keto tautomer. Computations
also support the relative stability order of keto LW over enol LW
over SW
Synthesis and Structural Investigation of an “Oxazinoquinolinespirohexadienone” That Only Exists as Its Long-Wavelength Ring-Opened Quinonimine Isomer
The spirocyclic oxazinoquinolinespirohexadienone (OSHD)
“photochromes”
are computationally predicted to be an attractive target as electron
deficient analogues of the perimidinespirohexadienone (PSHD) photochromes,
for eventual application as photochromic photooxidants. We have found
the literature method for their preparation unsuitable and present
an alternative synthesis. Unfortunately the product of this synthesis
is the long wavelength (LW) ring-opened quinonimine isomer of the
OSHD. We have found this isomer does not close to the spirocyclic
short wavelength isomer (SW) upon prolonged standing in the dark,
unlike other PSHD photochromes. The structure of this long wavelength
isomer was found by NMR and X-ray crystallography to be exclusively
the quinolinone (keto) tautomer, though experimental cyclic voltammetry
supported by our computational methodology indicates that the quinolinol
(enol) tautomer (not detected by other means) may be accessible through
a fast equilibrium lying far toward the keto tautomer. Computations
also support the relative stability order of keto LW over enol LW
over SW
Synthesis and Structural Investigation of an “Oxazinoquinolinespirohexadienone” That Only Exists as Its Long-Wavelength Ring-Opened Quinonimine Isomer
The spirocyclic oxazinoquinolinespirohexadienone (OSHD)
“photochromes”
are computationally predicted to be an attractive target as electron
deficient analogues of the perimidinespirohexadienone (PSHD) photochromes,
for eventual application as photochromic photooxidants. We have found
the literature method for their preparation unsuitable and present
an alternative synthesis. Unfortunately the product of this synthesis
is the long wavelength (LW) ring-opened quinonimine isomer of the
OSHD. We have found this isomer does not close to the spirocyclic
short wavelength isomer (SW) upon prolonged standing in the dark,
unlike other PSHD photochromes. The structure of this long wavelength
isomer was found by NMR and X-ray crystallography to be exclusively
the quinolinone (keto) tautomer, though experimental cyclic voltammetry
supported by our computational methodology indicates that the quinolinol
(enol) tautomer (not detected by other means) may be accessible through
a fast equilibrium lying far toward the keto tautomer. Computations
also support the relative stability order of keto LW over enol LW
over SW