9648
K. Panthi et al. / Tetrahedron 66 (2010) 9641e9649
combined filtrates were evaporated. The residue was purified by
flash column chromatography (silica gel, 10% ethyl acetate in pe-
troleum ether) to give pure 3 (78% yield) as a yellow solid. Mp:
88 ꢀC. Mass spectrum (MALDI-TOF) m/z Mþ¼845. 1H NMR
129.4, 141.7, 143.1, 146.1, and 148.1.MS (EIþ) for C43H30N3F3 calcu-
lated 645.2391, measured 645.2391.
4.2. Computational methodology
(500 MHz, CDCl3): d 7.03 (d, 4H), 7.09 (t, 4H), 7.14 (d, 8H), 7.3 (t, 8H),
7.4 (d, 4H), 7.5 (dd, 2H), 7.57 (dd, 2H), 7.77 (d, 2H), 7.96 (d, 2H), and
8.1 (d, 2H). 13C NMR (500 MHz, CDCl3): 106.3, 117.8, 119.4, 119.8,
120.6, 121.0,121.1,122.5,122.6,123.6,123.8,124.0,126.4,127.0,127.1,
127.2, 127.3, 127.4, 141.7, 143.1, 146.0, and 148.1.
Unconstrained geometry optimization was used to locate the
global minima of compounds (1e6) on the ground state potential
energy surface. Geometry optimization was first performed using
the B3LYP density functional in combination with the commonly
used 6-31G
basis set.26 These calculations were performed in the
*
4.1.5. Synthesis of 4-({7-(diphenylamino)-9-[4-(trifluoromethyl)-
phenyl]-9H-carbazol-2-yl}ethynyl)benzaldehyde (4). Compound 14
(200 mg, 0.38 mmol) and diphenylamine (60 mg, 0.38 mmol) were
mixed with dry toluene (80 ml) in a two necked round bottomed
flash containing a stir bar. The Pd(OAc)2 (3 mol %), P(t-Bu)3
(7 mol %), and Cs2CO3 (495 mg, 1.52 mmol) were also added and the
mixture was stirred under argon at 110 ꢀC for about 10 h. The re-
action mixture was then cooled to room temperature and toluene
was removed completely under vacuum. The solid mixture was
dissolved in tetrahydrofuran, and unreacted Cs2CO3 was removed
under gravity filtration. The organic residue was then purified by
column chromatography (silica gel, 10% ethyl acetate in petroleum
ether) to give the yellow compound 4 (180 mg, 77% yield). Mp:
vacuum, hexanes, and DCMdthe solvent environments treated
using the polarizable continuum solvation (PCM) model. Using the
fully optimized B3LYP/6-31G
*
minima, vertical transition energies
level of theory, Table S1 of
were computed at the TD B3LYP/6-31G
*
the ‘Supplementary data’ section of this work. The B3LYP functional
is the standard methodology for simulating various processes in
organic chemistry because it offers a good compromise between
computational cost and accuracy in the prediction of a variety of
molecular properties.27 However, as the low-lying electronic tran-
sitions in these compounds involve a large change in electron
density or intramolecular charge transfer (vide infra), the approxi-
mation in the level of theory used in this work has little to do with
the choice of basis set and mainly comes from the density func-
tional.28 This is especially true for the first electronic (HOMO/LUMO)
transition in the reported DeA complexes where electron density
shifts across these molecules from the donor moiety (D) to the ac-
142 ꢀC. 1H NMR (500 MHz, CDCl3):
d 7.05 (t, 2H), 7.1 (dd, 1H), 7.13(d,
4H), 7.14 (d, 1H), 7.27 (d, 4H), 7.51 (dd, 1H), 7.57 (s, 1H), 7.64 (d, 2H),
7.7 (d, 2H), 7.7.83 (d, 2H), 7.89 (d, 2H), 8.0 (d, 1H), 8.4 (d, 1H), and
10.03 (s, 1H). 13C NMR (500 MHz, CDCl3): 82.5, 88.7, 90.6, 96.9,
105.2, 112.9, 118.4, 118.7, 118.9, 119.9, 121.5, 123.0, 124.2, 124.8, 126.9,
127.3, 129.1, 129.3, 130.0, 130.2, 130.7, 132.3, 140.3, 142.3, 147.8, and
158.5. HRMS (EI) calculated for C40H25ON2F3 606.1919, measured
606.1910.
ceptor moiety (A) through different lengths of
p-conjugated me-
diators. However, these calculations provide a framework for
a qualitative comparative description of the electronic transitions in
compounds (1e6) in terms of molecular orbitals and the changes in
electron density accompanying electronic transitions. These results
are discussed in the ‘Results and discussion’ section of this work.
There is a growing need to obtain more quantitative agreement
between the calculated and experimental spectra of such DA type
compounds. This is why we also tested a more recently developed
long range corrected version of the B3LYP hybrid functional,
4.1.6. Synthesis of [4-({7-(diphenylamino)-9-[4-(trifluoromethyl)ph-
enyl]-9H-carbazol-2-yl}ethynyl)benzylidene]malononitrile (5). The
synthetic procedure is exactly same as for the synthesis of 2, but
using 4 as the starting material. The product was obtained after
purification by column chromatography (silica gel, 20% ethyl ace-
tate in petroleum ether) as an orange solid 5 (82% yield). Mp:
namely the CAM-B3LYP functional.29 The CAM-B3LYP/6-31G
cal-
*
culations yield a more quantitative agreement with the experi-
mental spectra, Table S1 and S2 of the ‘Supplementary data’
section of this work. All calculations reported in this work were
performed using the methodologies developed in the Gaussian
2009 package.30
212 ꢀC. 1H NMR (500 MHz, CDCl3):
d 7.05 (t, 2H), 7.1 (dd, 1H), 7.14 (d,
4H), 7.15 (d, 1H), 7.27 (d, 4H), 7.51 (dd, 1H), 7.57 (s, 1H), 7.66 (d, 2H),
7.68 (d, 2H), 7.75 (s, 1H), 7.84 (d, 2H), 7.92 (d, 2H), 8.0 (d, 1H), and
8.05 (d, 1H). 13C NMR (500 MHz, CDCl3): 82.5, 88.7, 90.6, 96.9, 105.2,
112.9, 118.4, 118.7, 118.9, 119.9, 121.5, 123.0, 124.2, 124.8, 126.9, 127.3,
129.1, 129.3, 130.0, 130.2, 130.7, 132.3, 140.3, 142.3, 147.8, and 158.5.
HRMS (TOF MS ESþ) calculated for C43H26N4F3 655.21, measured
655.20.
Acknowledgements
This present work has been partially supported by Grant NSF-
EXP 40000/10380080. We thank the donors of these funds. An al-
location of computing time from the Ohio Supercomputer Center is
acknowledged.
4.1.7. Synthesis of N,N,N0,N0-tetraphenyl-9-[4-(trifluoromethyl)phe-
nyl]-9H-carbazole-2,7-diamine (6). Compound 13 (200 mg,
0.38 mmol) and diphenylamine (120 mg, 0.77 mmol) were mixed
with dry toluene (80 ml) in a two necked round bottomed flash
containing a stir bar. The Pd(OAc)2 (3 mol %), P(t-Bu)3 (7 mol %), and
Cs2CO3 (495 mg, 1.52 mmol) were also added and stirred under
argon at 110 ꢀC for about 18 h. The reaction mixture was then
cooled to room temperature and toluene was removed completely
under vacuum. The solid mixture was dissolved in tetrahydrofuran
and unreacted Cs2CO3 was removed under gravity filtration. The
organic residue was then purified by column chromatography
(silica gel, 10% ethyl acetate in petroleum ether) to give the yel-
lowish white product (180 mg, 77% yield). 1HMR (500 MHz, CDCl3):
Supplementary data
1H and 13C NMR spectra of compound 1e6 and 14, and the
calculated TD DFT vertical transition energies of compounds 1e6.
Supplementary data associated with this article can be found in
References and notes
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d
7.01 (t, 4H), 7.07 (dd, 2H), 7.10 (dd, 8H), 7.15 (d, 2H), 7.25 (t, 8H),
7.7.52 (d, 2H), 7.69 (d, 2H), and 7.93 (d, 2H). 13C NMR (500 MHz,
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123.6, 123.8, 124.0, 126.4, 127.0, 127.1, 127.2, 127.3, 127.4, 141.7, 143.1,
146.0, and 148.1. 13C NMR (500 MHz, CDCl3): 106.3, 117.9, 119.4,
119.8, 120.6, 121.1, 122.5, 123.6, 123.8, 126.4, 127.0, 127.3, 129.2,
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