Chemistry - A European Journal
10.1002/chem.202004481
FULL PAPER
acclimatized room (17°C) in spectroscopic dichloromethane. UV-Vis
with auxiliary basis set.[50] For the BODIPY- terminated oligomers (nPEC4-
By), the HF-3c geometries were further optimized with CAM-B3LYP[51]
functional using the def2-SVP basis set. The Hessians were obtained for
all of the structures showing no negative frequencies, i.e. all optimized
structures are true minima. The DLPNO-STEOM-CCSD method, which
previously showed a remarkable precision for nPEC4-By oligomers,[52] was
applied to predict photophysical properties of nPEC4-X oligomers, using
the first six singlet excited states to calculate the excitation energies and
transition dipoles on the optimized ground state geometry taking into
account the solvent (dichloromethane) effect by using the conductor-like
polarizable continuum model (C-PCM). The vertical gradient was applied
to compute the excited state geometry and Hessian. This procedure is part
of the excited-state-dynamic (ESD) module, which admits that Hessian of
the excited state is equal to the ground state one and extrapolates the
excited state geometry from the excited state gradient.
spectra were obtained with
a
Shimadzu 2401 PC UV/VIS
spectrophotometer. The extinction coefficient ε was determined from the
slope of the absorbance vs. molar concentration of at least four solutions.
The excitation and emission spectra were obtained with an Horiba PTI
Quantamaster QM-8450-22-c spectrofluorimeter equipped with an
integrating sphere for the determination of the quantum yield. All of the
spectra were obtained with background correction and with the same slits
and bias between the sample and the solvent. Slits were established in
order to keep the uncorrected spectra under the linear range of detection
(
106 counts). The excitation wavelength was 10 nm below the main
absorption peak and the absorbance at that wavelength was adjusted to be
lower than 0.1. At least four solutions were analysed for each complex and
the quantum yield was averaged and reported as φ. Stokes’ shift (∆ν)
values were calculated from the absorption and fluorescence maximums in
wavenumbers (λemis-λabs). CIE 1931 coordinates were found by the
fluorimeter software and the CIE colour diagram was constructed with
goCIE free software. The colour purity was calculated based on the
following equation:
Acknowledgements
We wish to acknowledge the Mexican National Council for Science
and Technology CONACYT for the financial support through the
projects CB-2015: 256716 and 256709. G.C. thanks CONACYT
for the Cathedra’s initiative. Authors also acknowledge,
Guadalupe Méndez, Carlos de la Peña and Gilberto Hurtado for
their technical help. All of the Authors are grateful to Dr. Romain
Berraud-Pache from Max-Plank-Institut fur Kohlenforschung
Mülheim for his technical support all through the theoretical
analyses.
c c d c d c
colour purity=√((x-x )^2+(y-y )^2 )/√((x -x )^2+(y -y )^2 )
d d
where (x;y) are the colour coordinates for the material, x and y are those
of the dominant colour, which are obtained from the intersection of the line
connecting the (x,y) point with perfect white light (xc, yc) = (0.33, 0.33).
Average fluorescence lifetimes (τ) were obtained by the time correlated
single photon counting (TCSPC) technique on an Horiba Jobin Yvon
TemPro instrument with a nanoLED laser of a wavelength close to the
wavelength used for the emission spectra. Fits were performed on the
DAS6 software of the instrument. Radiative (kr) constants were calculated
from the equation: kr=φ/τ. A 0.01% suspension of Ludox AS40 (Aldrich) in
ultrapure water was used for the prompt signal. Calibration of the
Keywords: BODIPY, conjugated oligomers, Density Functional
Theory, dual emission.
equipment was realized with
oxazolyl)benzene] methanol solution (optical density 0.1 and lifetime of
.93 ns).[42] The electrochemical properties of all of the compounds were
a POPOP [4-bis(4-methyl-5-phenyl-2-
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)
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version 4.2.1.[43] The molecular structures were drawn by using the free
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geometries of nPEC4-X oligomers were further optimized in vacuum using
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