Dicationic Heteroacenes Containing Thio- or Selenopyrylium Moieties

Article abstract of DOI:10.1021/acs.organomet.9b00100

Dicationic heteroacenes that bear thio- or selenopyrylium moieties were synthesized by addition reactions of the corresponding diones with a Grignard reagent, followed by a dehydration reaction of the resulting diols with Br?nsted acid. Alternatively, these dicationic heteroacenes were obtained from two-electron oxidations of the corresponding sulfur- or selenium-containing quinoids. The electronic structures of these dicationic heteroacenes were examined by NMR and UV-vis-NIR spectroscopy in conjunction with density functional theory calculations. The results of this combined experimental and theoretical approach strongly imply effective conjugation of 22π-electrons in a system that is distributed over the entire pentacene framework.

Full text of DOI:10.1021/acs.organomet.9b00100

Article
pubs.acs.org/Organometallics
Cite This: Organometallics XXXX, XXX, XXX−XXX
Dicationic Heteroacenes Containing Thio- or Selenopyrylium
Moieties
Noriyoshi Nagahora,* Tomoko Kushida, Kosei Shioji, and Kentaro Okuma
Department of Chemistry, Faculty of Science, Fukuoka University, Jonan-ku, Fukuoka 814-0180, Japan
S
* Supporting Information
ABSTRACT: Dicationic heteroacenes that bear thio- or selenopyrylium
moieties were synthesized by addition reactions of the corresponding diones
with a Grignard reagent, followed by a dehydration reaction of the resulting
diols with Brønsted acid. Alternatively, these dicationic heteroacenes were
obtained from two-electron oxidations of the corresponding sulfur- or
selenium-containing quinoids. The electronic structures of these dicationic
heteroacenes were examined by NMR and UV−vis−NIR spectroscopy in
conjunction with density functional theory calculations. The results of this
combined experimental and theoretical approach strongly imply effective conjugation of 22π-electrons in a system that is
distributed over the entire pentacene framework.
containing thio- or selenopyrylium moieties. For that purpose,
we designed synthetic routes to 1a and 1b (Figure 2) via
intramolecular Friedel−Crafts cyclizations of suitable precur-
sors, which are based on a previous report on the synthesis of
2,5-arylchalcogenoterephthalic acid derivatives.10 More re-
cently, Chi and co-workers have independently reported the
synthesis of linear acenic derivative G, which bears
thiopyrylium subunits, by two-electron oxidation of the
corresponding quinoidal precursor, and revealed its solid-
state structure.11 As reports on the synthesis of pentacene
analogues that contain sulfur atoms have remained scarce over
the last decades, investigations on such synthetic approaches
still remain a great challenge. Furthermore, synthetic
investigations into dicationic pentacenes that bear selenium
atoms have not been reported so far. Heteroacene 1b is the
first example of its kind and provides valuable photophysical
information on this class of compounds.
INTRODUCTION
■
The synthesis of linearly fused polycyclic aromatic hydro-
carbons has received considerable attention owing to their
potential utility in organic photovoltaics, organic light-emitting
diodes, and organic field-effect transistors. Among these
promising small organic molecules, pentacene and its
derivatives are known to be key components of high-
performance organic thin-film devices.1 Azapentacenes, i.e.,
isoelectronic analogues of pentacene containing nitrogen
atoms, have recently attracted particular interest as a new
and promising class of organic materials. Numerous synthetic
routes to diaza- and tetraazapentacenes as well as their
applications in organic field effect transistors materials have
been reported.2 Furthermore, diazadiborapentacene and
thiaborin derivatives have been reported (Figure 1) and their
unique structures and properties have been probed.3
Meanwhile, thio- and selenopyrylium salts represent a
fundamental class of molecules in the field of organic chemistry
that has attracted much attention in the last decade.4 To date,
the synthesis of thio- or selenopyrylium-based acenic
molecules, such as chalcogenpyrylium-containing naphtha-
lenes,5 anthracenes,6 and tetracenes,7 has been reported.
Theoretical investigations into these molecules have been
also performed, and these predict characteristically small
highest occupied molecular orbital (HOMO)−lowest unoccu-
pied molecular orbital (LUMO) gaps.8 Thus, it was postulated
that the electronic communication of p-orbitals between
carbon and chalcogen atoms can decrease the optical band
gap. In 1994, dicationic pentacene derivative F, which includes
two thiopyrylium units, had been synthesized via a dehydration
reaction of the corresponding thiopyranol precursor with a
Herein, we report our concerted experimental and
theoretical approach to develop a synthetic route to novel
dicationic linear heteroacenes 1a and 1b, which bear thio- or
selenopyrylium units (Figure 2), respectively, and we describe
their electronic structures.
RESULTS AND DISCUSSION
■
Synthesis of Dicationic Heteroacenes 1a and 1b.
Synthetic access to dicationic heteroacenes 1a and 1b was
established via the following two pathways (Scheme 1): (i)
treatment of dione derivatives 5a and 5b with arylmagnesium
bromides, followed by dehydration reactions of the corre-
sponding diol derivatives (6a and 6b) with a Brønsted acid;
(ii) two-electron oxidation of conjugated quinoidal molecules
7a and 7b.
9
1
Brønsted acid. The H NMR as well as UV−vis absorption
spectra were recorded, and the latter revealed a red-edge
absorption maximum at 778 nm. The result inspired us to
explore the synthesis of new dicationic heteroacenes
Received: February 14, 2019
© XXXX American Chemical Society
A
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Figure 1. Structures of selected diaza-, tetraazapentacenes, and pentacene analogues that contain nitrogen, boron, and/or sulfur atoms.
diffraction analysis (Figure S1). The results obtained indicate
that the Friedel−Crafts reaction of phthaloyl dichloride 4b′
involves an aryl migration via intermediate G through ipso-
acylation (Scheme 3).12 Treatment of diones 5a and 5b with
tetramethylphenylmagnesium bromide in the presence of zinc
chloride furnished diol derivatives 6a and 6b as diastereomeric
mixtures in 51 and 28% yield, respectively (Scheme 4).
Meanwhile, treatment of diones 5a and 5b with
tetramethylphenylmagnesium bromide, followed by a reaction
with tin(II) chloride dihydrate afforded the corresponding
quinoids 7a and 7b in 31 and 63% yield, respectively (Scheme
4). Prior to the chemical oxidations of 7a and 7b, the
electrochemical behavior of 7a and 7b was examined by cyclic
and differential pulse voltammetry. The corresponding
voltammograms are shown in Figure 3. Reversible stepwise
one-electron oxidation couples were observed between −0.10
and +0.41 V for 7a and 7b (Table 1), suggesting that quinoids
Figure 2. Chemical structures of 1a and 1b.
Initially, the nucleophilic substitutions of dibromophthalic
acid ethyl ester 2 with benzenethiol 3a or benzeneselenol 3b
provided phthalic acids 4a or 4b, which bear thioaryl or
selenoaryl groups, in 72 and 20% yield, respectively (Scheme
2). Subsequent chlorination and Friedel−Crafts acylation of 4a
afforded dione 5a in 91% yield. In the case of selenium
analogue 4b, the sequence of chlorination and Friedel−Crafts
acylation provided exclusively dione 5b in 25% yield and its
molecular structure was confirmed by single-crystal X-ray
Scheme 1. Synthetic Pathways to Dicationic Heteroacenes 1a and 1b
B
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Scheme 2. Synthesis of 5a and 5b
Scheme 3. Formation of 5b
Scheme 4. Synthesis of 1a and 1b
7a and 7b feature low oxidative potentials and that the
resulting oxidized species are relatively stable in solution.
To synthesize dicationic heteroacenes 1a and 1b, we initially
tried dehydrations of diols 6a and 6b using the Brønsted acid,
tetrafluoroboric acid (Scheme 4). Upon adding an ethereal
solution of tetrafluoroboric acid to a solution of 6a and 6b in
dichloromethane at room temperature, the absorption for 6a
and 6b in their UV−vis spectra disappeared. The solution was
added dropwise to cooled hexane, and the brownish stable
powder that precipitated was isolated by centrifugation. An
elemental analysis of this brown powder (1a) or reddish purple
powder (1b) revealed an elemental composition consistent
with dication bis(tetrafluoroborate)s 1a and 1b, respectively,
and this assignment was corroborated by multinuclear NMR
spectroscopic analyses (vide infra).
Subsequently, oxidation reactions of quinoids 7a and 7b
using (NO)[BF4] were monitored using UV−vis−NIR
absorption spectroscopy. Upon treating 7a and 7b with one
equivalent of (NO)[BF4] in CH2Cl2/CH3CN (v/v = 9:1) at
room temperature, the absorption bands for 7a and 7b
disappeared in their UV−vis−NIR absorption spectra (Figure
S2). Simultaneously, intense absorptions emerged in the NIR
C
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Figure 3. Cyclic (black) and differential pulse (red) voltammograms of 7a (left) and 7b (right).
a
Table 1. Observed Redox Potentials [V vs Fc/Fc+] for 7a
and 7b
7a
7b
compd
first
second
first
second
Epa
Epc
E1/2
−0.08
−0.20
−0.14
+0.49
+0.34
+0.41
−0.02
−0.19
−0.10
+0.48
+0.30
+0.39
a
Supporting electrolyte: 0.1 M [n-Bu4N][PF6]; [7a]: 1.2 × 10−3 mol/
L; [7b]: 5.0 × 10−3 mol/L (both in CH2Cl2); scan rate: 100 mV/s;
room temperature.
region, which were assigned to the corresponding radical
cations 8a (λmax = 896/1094 nm) and 8b (λmax = 922/1128
nm). These absorptions were attributed to π−π* electron
transitions of the pentacene chromophores, which is supported
by theoretical calculations (vide infra). Moreover, the red-edge
absorption at λmax = 1094 nm for sulfur analogue 8a is
comparable to that of previously reported radical cation E
(λmax = 1092 nm in CH2Cl2). The ESR spectra of 8a and 8b
exhibited a broad signal at g = 2.004 and 2.010, respectively
(Figure S3), which supports the presence of such radical
species in solution.
Figure 4. UV−vis−NIR absorption spectra of (a) 7a and (b) 7b upon
addition of (NO)[BF4] (1.0, 2.0, 3.0, 4.0, and 5.0 equivalents) in
CH2Cl2/CH3CN (v/v = 9:1) at room temperature.
Upon adding an excess of (NO)[BF4], the bands for 8a and
8b completely disappeared, under concomitant emergence of
weak absorptions at 706/784 nm (8a) or 742/824 nm (8b)
(Figure 4). These new bands can be attributed to dications 1a
and 1b and are consistent with those of theoretically calculated
dications 1a′ and 1b′ (vide infra). The red-edge absorptions
correspond to π−π* electron transitions of the dicationic
pentacene chromophore for sulfur and selenium analogues 1a
and 1b, respectively. The red-edge absorption of the former is
comparable to those of the previously reported dications F
(λmax = 778 nm in 0.05 M TfOH−CH3CN) and G (λmax = 780
nm in CH2Cl2). The observed bathochromic shift for the red-
edge absorption maxima for 1a and 1b is larger than that
between heteropentacene analogues A (λmax = 661 nm in
hexane), C (λmax = 681 nm in hexane), D (λmax = 523 nm in
cyclohexane), and E (λmax = 499 nm in cyclohexane) (Figure
1) and also between thiophene- and/or selenophene-
containing heterocycles, such as I13 (λmax = 489 nm in
CH2Cl2), J13 (λmax = 481 nm in CH2Cl2), K14 (λmax = 344 nm
in tetrahydrofuran (THF)), and L14 (λmax = 356 nm in THF)
(Figure 5). Thus, the observed decrease of the optical band
gap can be reasonably rationalized in terms of a weak overlap
of the π orbitals between the carbon-2p and sulfur-3p/
selenium-4p orbitals in the pentacene core of 1a and 1b.
NMR Spectroscopic Characterization of 1a and 1b.
The molecular structures of 1a and 1b in solution were
investigated by NMR spectroscopy. The NMR spectra of 1a
Figure 5. Molecular structures of I−L.
and 1b are shown in Figures S8−S10. The 1H NMR spectra of
1a and 1b revealed deshielded resonances for all aromatic
protons (<8 ppm) except for the tetramethylphenyl groups
(Table 2), which are comparable to those of previously
reported sulfur-containing acenes F and G. The most low-field-
shifted signals for 1a and 1b can be assigned to the H6 protons
at 9.58 and 9.68 ppm, respectively (cf. Table 2). Moreover, the
resonances for the ortho-methyl groups of the tetramethyl-
phenyl groups in 1a and 1b at 1.69 and 1.68 ppm, respectively,
are upfield shifted, whereas the methyl groups at the meta-
position resonate at 2.46 and 2.45 ppm, respectively. In their
entirety, these results suggest the presence of a significant
diatropic ring current in the pentacene subunits of 1a and 1b.
The 13C NMR spectra of 1a and 1b indicate a C2 symmetric
structure in solution (Figure S9), which is similar to those of
the reported compounds F and G. Signals for atoms C1−C12
in 1a and 1b were observed at 127.5−167.2 ppm, whereas the
D
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1
Table 2. Observed and Calculated H NMR Chemical Shifts [ppm] for 1a/1b and 1a′/1b′
c
d
compd
H1
H2
H3
H4
H6
CH3
CH3
C(CH3)3
a
1a
8.06
8.42
8.26
8.48
8.69
8.91
8.89
8.53
9.02
8.64
9.58
9.41
9.67
9.32
1.69
1.39
1.69
1.20
2.46
2.28
2.45
2.26
1.34
1.10
1.55
1.34
b
1a′
a
1b
8.01
8.18
b
1b′
a
b
Experimentally observed chemical shifts were recorded in CDCl3/CD3CN (v/v = 4:1). Calculations were carried out at the GIAO-B3LYP/6-
311+G(2d,p)//B3LYP/6-311+G(2d,p) level of theory. Methyl groups are located at the 2,6-positions of the duryl substituents. Methyl groups
c
d
are located at the 3,5-positions of the duryl substituents.
most low-field-shifted signals at 176.3 ppm (for 1a) and 175.8
ppm (for 1b) were attributed to the C8 atoms of the
chalcogenopyrylium ring (cf. Table S4). These experimentally
observed chemical shifts of the pentacene core are substantially
inconsistent with those of carbocations,15 such as the
diphenylmethylium (δ = 201) and triphenylcarbenium (δ =
212) cations, indicating that 1a and 1b do not exhibit a
localized carbocationic character in solution.
framework, respectively, whereas the HOMO to HOMO − 3
are localized exclusively on the π-electrons of the tetramethyl-
phenyl groups (Figures S5 and S6). The results of TD-DFT
calculations on 1a′ and 1b′ revealed that the predicted intense
π−π* transitions can be assigned to the HOMO − 4 →
LUMO and HOMO − 6 → LUMO transitions (Figure 6 and
Although we could not detect 77Se NMR resonance for 7b in
CDCl3 at room temperature, we observed a singlet for dication
1b at 727.1 ppm in CDCl3/CD3CN (v/v = 4:1) at room
temperature (Figure S10). The resonance observed for 1b is
low-field-shifted relative to neutral selenophene16 (δ = 613)
and benzo[b]selenophene16 (δ = 526), as well as slightly
upfield shifted relative to that of monocationic selenopyrylium
derivatives, such as selenopyrylium perchlorate17 (δ = 976 in
CF3COOD), selenopyrylium tetrafluoroborate18 (δ = 975.7 in
CD3CN), and 3-tert-butyl-2-benzoselenopyrylium tetrafluor-
oborate18 (δ = 890 in CD3CN). The results of the 77Se NMR
analysis thus clearly suggest that 1b should be considered a
cationic aromatic molecule. Accordingly, on the basis of this
multinuclear NMR analysis, it seems feasible to conclude that
in solution, 1a and 1b represent aromatic chalcogenopyrylium-
containing dicationic pentacenes.
Figure 6. HOMO − 6, HOMO − 4, and LUMOs (isovalue: 0.020) of
dications 1a′ and 1b′ calculated at the B3LYP/6-311+G(2d,p) level
of theory. Hydrogen atoms are omitted for clarity.
Table 3) and that the transition energies of selenium analogue
1b′ are narrower than those of sulfur analogue 1a′, which is in
good agreement with the experimentally observed results.
Theoretical Investigations. To gain further insight into
the electronic structures of 1a and 1b, we carried out
theoretical calculations on radical cations 8a′ and 8b′ as well
as dications 1a′ and 1b′, where the counter anions were
omitted for simplicity. These molecules were optimized using
density functional theory (DFT) methods implemented in the
Gaussian 16 program,19 leading to C2h symmetric optimized
structures for 1a′ and 1b′ as well as 8a′ and 8b′. For radical
cations 8a′ and 8b′, assignment of the UV−vis−NIR
absorption spectra was based on the results of time-dependent
(TD)-DFT calculations at the UB3LYP/6-311+G(2d,p) level
of theory. The experimentally observed absorption bands of 8a
and 8b were assigned to singly occupied molecular orbital
(SOMO) → LUMO and SOMO − 1 → SOMO transitions,
i.e., symmetry-allowed π−π* transitions in the heteropenta-
cene framework (Figure S4).20 Thus, the theoretically
predicted wavelengths match sufficiently well with the
experimentally observed absorption bands in the UV−vis−
NIR spectra.
Table 3. Summary of the TD-DFT Calculations on
a
Dications 1a′ and 1b′
b
c
d
compd
E (eV)
λ (nm)
f
transition
1a′
1.632
2.838
1.550
2.683
759.7
436.8
799.7
462.1
0.0558
0.8282
0.0510
1.0403
HOMO − 4 → LUMO
HOMO − 6 → LUMO
HOMO − 4 → LUMO
HOMO − 6 → LUMO
1b′
a
Calculations were carried out at the TD-B3LYP(PCM-CH2Cl2)/6-
b
311+G(2d,p)//B3LYP/6-311+G(2d,p) level of theory. Excitation
energy. Wavelength. Oscillator strength.
c
d
1
The calculated H and 13C NMR chemical shifts of 1a′ and
1b′ are summarized in Tables 2 and S4, respectively, together
with the experimental results. The 1H NMR resonances for the
H1−H6 protons on the pentacene core were calculated to
resonate < 8.18 ppm. Although resonances for the methyl
groups, which are located at the 2,6-positions of the
tetramethylphenyl subunits, are upfield shifted to 1.39 (1a′)
and 1.20 (1b′) ppm, those at the 3,5-positions were shifted to
2.28 (1a′) and 2.26 (1b′) ppm. The calculated 13C NMR shifts
In dicationic heteroacenes 1a′ and 1b′, the theoretically
derived LUMOs and HOMO − 4 to HOMO − 7 are
delocalized over the π*- and π-orbitals of the heteropentacene
E
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(Table S4) for the pentacene framework of 1a′/1b′ are in
good agreement with the experimentally observed chemical
shifts. These results strongly suggest that dications 1a′ and 1b′,
which contain thio- or selenopyrylium moieties, exhibit a
diatropic ring current in the pentacene core.
subunits and that exhibits a substantially decreased optical
band gap. Our study thus provides a reliable strategy for the
fine-tuning of the molecular and electronic structure of
aromatic ring systems by replacing individual atoms.
The results of nucleus-independent chemical shift
(NICS)21,22 calculations on 1a′ and 1b′ are summarized in
Table 4 and show that the NICS(1)zz values of the inner
EXPERIMENTAL SECTION
General. All solvents were purified by standard methods.
Preparative thin-layer chromatography was performed on Merck
silica gel 60 PF254. Column chromatography was performed on silica
■
1
Table 4. Calculated Nucleus-Independent Chemical Shifts
gel 60N (Kanto Chemical) under an ambient atmosphere. H (400
a
(NICS) [ppm] of 1a′ and 1b′
MHz) and 13C NMR (101 Hz) spectra were recorded in CDCl3 on a
Bruker Avance spectrometer using the residual resonances of CHCl3
(δH = 7.26) and CDCl3 (δC = 77.0) as well as of DMSO-d6 (δH
=
C
2.50; δC = 39.5) as the internal standards to reference the 1H and 13
NMR spectra. 19F (376 MHz) and 77Se (76.3 MHz) NMR spectra
were recorded on a Bruker Avance spectrometer using CFCl3 (δF =
0.00) and 90% Me2Se in C6D6 (δSe = 0.00) as the external standards.
The assignment of the signals was typically accomplished on the basis
of one-dimensional (homodecoupling and DEPT) and two-dimen-
sional (COSY, HMQC, and HMBC) NMR techniques. Unless
otherwise stated, all 13C and 19F NMR experiments were performed
using broad-band 1H decoupling. Electron ionization (EI) and
electrospray ionisation time-of-flight (ESI-TOF) mass spectral data
were obtained on a JEOL JMS-GCmateII and a JEOL JMS-T100CS
spectrometer, respectively. Absorption spectra were recorded on a
JASCO V-550 UV−vis or a Shimadzu UV-3600 UV−vis−NIR
spectrometer. Electrochemical experiments were carried out with an
ALS 617D electrochemical analyzer using a glassy carbon disk
working electrode, a Pt wire counter electrode, and Ag/0.01 M (1 M
= 1 mol/dm3) AgNO3 reference electrode. The measurements were
carried out at ambient temperature in CH2Cl2 containing 0.1 M [n-
Bu4N][PF6] as the supporting electrolyte using a scan rate of 100
mV/s. Elemental analyses were carried out on a JM11 CHN analyzer
by J-Science Lab. All melting points were determined on a Yanaco
micro-melting point apparatus or a Mettler Toledo MP90 melting
point system and are uncorrected.
compd
A
B
C
1a′
1b′
−11.60
−10.86
−6.77
−5.72
−9.70
−9.20
a
Calculations were carried out at the GIAO-B3LYP/6-311+G-
(2d,p)//B3LYP/6-311+G(2d,p) level of theory.
benzene rings are increased relative to those of the outer
benzene and chalcogenopyrylium rings, reflecting that the
heteropentacene framework of 1a′ and 1b′ exhibits a diatropic
ring current due to their 22π-electron system.
A natural population analysis23 of dications 1a′ and 1b′
revealed highly positive charges of +0.82 (1a′) and +0.72
(1b′) at the chalcogen atoms (Figure S7), whereas the
pentacene framework consists of less polar carbon atoms; the
observed charges (+0.14 to −0.23) indicate that form M
should be the dominant resonance structure for 1a′ and 1b′
(Scheme 5). Therefore, the combined results of the theoretical
survey suggest that 1a′ and 1b′ exhibit a cation-localized
dicationic aromatic character with 22π-electrons.
Materials. Unless stated otherwise, all materials were purchased
from common commercial chemical suppliers and used without
further purification. All reactions were carried out under an inert
atmosphere of argon or nitrogen. The synthesis of 4a and 5a was
accomplished using modified procedures reported previously.10,11
Di(4-tert-butylphenyl)diselenide24 and 3-bromo-1,2,4,5-tetramethyl-
benzene25 were prepared according to previously reported proce-
dures.
CONCLUSIONS
■
We have reported the synthesis of pentacyclic dicationic
heteroacenes 1a and 1b, which bear thio- or selenopyrylium
moieties, via (i) addition reactions of the corresponding diones
with a Grignard reagent followed by a dehydration reaction
with Brønsted acid and (ii) via two-electron oxidation
reactions of quinoids 7a and 7b. Heteroacenes 1a and 1b
are thermally robust, which is due to the incorporation of
tetramethylphenyl and tert-butyl groups. Heteroacenes 1a and
1b could potentially be used to build more complex
thiopyrylium- or selenopyrylium-based heteroacene derivatives
and also to synthesize promising prospective organic functional
materials. The cationic sp2-type sulfur or selenium atoms
introduced to replace the CH moieties in the pentacene unit
lead to bathochromically shifted red-edge absorption and 22π-
electron aromaticity. Selenium analogue 1b is the first example
of a heteropentacene that contains two selenopyrylium
Synthesis of Phthalic Acid 4a.10 Diethyl 2,5-dibromoterephthalate
(1.00 g, 2.63 mmol), 4-tert-butylbenzenethiol (2.30 mL, 13.2 mmol),
and potassium carbonate (2.18 g, 15.8 mmol) were dissolved in
dimethylformamide (DMF) (15 mL) and stirred for 20 h at 120 °C,
before the reaction mixture was poured into water (150 mL). The
aqueous layer was washed with ethyl acetate and acidified by addition
of a solution of hydrochloric acid. The resulting yellow suspension
was filtered, and the thus obtained solid was washed with water and
dried under reduced pressure to afford phthalic acid 4a (0.932 g, 1.88
1
mmol, 72%) as a yellow solid. 4a: mp > 300 °C; H NMR (DMSO-
d6) δ 7.52 (d, J = 8.0 Hz, 4H, ArH), 7.44 (d, J = 8.0 Hz, 4H, ArH),
7.29 (s, 2H, ArH), 1.31 (s, 18H, CH3); 13C NMR (DMSO-d6) δ
166.3 (C), 152.1 (C), 137.6 (C), 134.4 (CH), 131.0 (C), 129.3
(CH), 128.4 (C), 127.0 (CH), 34.5 (C), 30.9 (CH3); HRMS (EI,
positive mode) (m/z): [M]+ calcd for C28H30O4S2, 494.1586; found,
494.1574.
Scheme 5. Conceivable Resonance Structures for Dications 1a′ and 1b′
F
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1
Synthesis of Phthalic Acid 4b. Diethyl 2,5-dibromoterephthalate
(1.00 g, 2.63 mmol), di(4-tert-butylphenyl)diselenide (2.23 g, 1.58
mmol), and potassium carbonate (2.18 g, 15.8 mmol) were dissolved
in DMF (20 mL). Sodium borohydride (0.597 g, 15.8 mmol) was
added to the solution at room temperature, and the solution was
stirred for 20 h at 120 °C. The solution was allowed to cool to room
temperature and then poured into water (20 mL). After the solution
was filtered, the filtrate was washed with ethyl acetate. The aqueous
layer was acidified by addition of a solution of hydrochloric acid, and
the resulting yellow suspension was filtered. The thus obtained solid
was washed with water and dried under reduced pressure to afford
phthalic acid 4b (0.317 g, 0.36 mmol, 20%) as a yellow solid. 4b: mp
51%). 6a: orange solid; mp 190−191 °C; H NMR (CDCl3) δ 7.17
(dd, J = 8.2 Hz, 2.1 Hz, 1H, ArH), 7.09 (dd, J = 8.2 Hz, 2.1 Hz, 1H,
ArH), 7.04−7.02 (m, 3H, ArH), 6.97 (d, J = 8.2 Hz, 1H, ArH), 6.85
(d, J = 2.1 Hz, 1H, ArH), 6.55 (d, J = 2.0 Hz, 1H, ArH), 6.44 (s, 1H,
ArH), 4.86 (s, 1H, ArH), 2.32−2.21 (m, 15H, CH3), 1.92−1.87 (m,
9H, CH3), 1.05 (s, 9H, CH3), 1.03 (s, 9H, CH3); HRMS (ESI-TOF,
positive mode) (m/z): ([M − OH]+) calcd for C48H53OS2, 709.3532;
found, 709.3524; anal. calcd for C48H54O2S2: C, 79.29; H, 7.49%;
found: C, 79.01; H, 7.28%.
Synthesis of Diol 6b. A suspension of bromo-2,3,5,6-tetramethyl-
benznene (0.465 g, 2.18 mmol), magnesium turnings (0.106 g, 4.36
mmol), and zinc chloride (0.036 g, 0.26 mmol) in THF (10 mL) was
stirred for 4 h under reflux. After cooling to room temperature, the
suspension was added to a solution of dione 5b (0.100 g, 0.181
mmol) in THF (30 mL) at room temperature. The reaction mixture
was stirred for 20 h under reflux, before being poured into a saturated
solution of ammonium chloride. The resulting suspension was filtered,
and the organic layer of the filtrate was extracted with ether. The
combined organic layers were dried over anhydrous sodium sulfate,
filtered, and dried under reduced pressure to give a crude brown solid.
Separation of the crude brown solid by column chromatography on
silica gel (eluent: dichloromethane) afforded diol 6b as a
diastereomeric mixture (0.041 g, 0.45 mmol, 28%). 6b: orange
solid; mp 165−167 °C; 1H NMR (CDCl3) δ 7.23 (d, J = 2.0 Hz, 1H,
ArH), 7.17 (d, J = 2.0 Hz, 1H, ArH), 7.02 (s, 2H, ArH), 6.95 (dd, J =
8.4, 2.0 Hz, 1H, ArH), 6.88 (dd, J = 8.8, 2.0 Hz, 1H, ArH), 6.75 (d, J
= 8.4 Hz, 1H, ArH), 6.60 (s, 1H, ArH), 6.49 (d, J = 8.8 Hz, 1H, ArH),
5.10 (s, 1H, ArH), 2.31−2.21 (m, 15H, CH3), 1.91 (s, 3H, CH3), 1.89
(s, 3H, CH3), 1.87 (s, 3H, CH3), 1.23 (s, 18H, CH3); 77Se NMR
(CDCl3) δ 359.7 (s), 345.0 (s); HRMS (ESI-TOF, positive mode)
(m/z): ([M − OH]+) calcd for C48H53O80Se2, 805.2421; found,
805.2429; anal. calcd for C48H54O2Se2: C, 70.23; H, 6.63%; found: C,
70.41; H, 6.80%.
Synthesis of Quinoid 7a. A suspension of bromo-2,3,5,6-
tetramethylbenznene (0.465 g, 2.18 mmol), magnesium turnings
(0.106 g, 4.36 mmol), and zinc chloride (0.020 g, 0.15 mmol) in THF
(10 mL) was stirred for 4 h under reflux. After cooling to room
temperature, the suspension was added to a solution of dione 5a
(0.100 g, 0.218 mmol) in THF (10 mL) at room temperature. Then,
the reaction mixture was stirred for 20 h under reflux, before being
poured into a solution of tin(II) chloride dihydrate (0.984 g, 4.36
mmol), 1.0 mol/L hydrochloric acid (3.0 mL), and water (1.0 mL) at
room temperature. After the solution was stirred for 2 h at room
temperature, the solution was extracted with dichloromethane. The
organic layer was dried over anhydrous sodium sulfate, filtered, and
concentrated under reduced pressure. Separation of the crude residue
was accomplished by column chromatography on silica gel (hexane/
dichloromethane = 10:1, v/v), which afforded quinoid 7a (0.047 g,
1
> 300 °C; H NMR (DMSO-d6) δ 7.57 (d, J = 8.4 Hz, 4H, ArH),
7.50 (d, J = 8.4 Hz, 4H, ArH), 7.44 (s, 2H, ArH), 1.31 (s, 18H, CH3);
13C NMR (DMSO-d6) δ 166.8 (C), 152.2 (C), 136.6 (CH), 135.3
(C), 131.1 (C), 131.0 (C), 127.0 (CH), 124.8 (C), 34.5 (C), 31.0
(CH3); 77Se NMR (DMSO-d6) δ 447.4 (s); HRMS (ESI-TOF,
negative mode) (m/z): ([M − H]−) calcd for C28H29O480Se2,
589.0396; found, 589.0388; anal. calcd for C28H30O4Se2: C, 57.15; H,
5.14%; found: C, 56.92; H, 5.26%.
Synthesis of Dione 5a.11 A solution of phthalic acid 4a (0.500 g,
1.01 mmol) in DMF (1 mL) and thionyl chloride (10 mL) was stirred
for 4 h at room temperature, before all volatile substances were
removed under reduced pressure. After a solution of titanium
tetrachloride (3.0 mL, 10 mmol) in dichloromethane (20 mL) was
added, the resulting reaction mixture was stirred for 16 h at room
temperature. Then, the reaction mixture was poured into water (20
mL) and the organic layer was extracted with dichloromethane. The
combined organic layers were dried over anhydrous sodium sulfate,
filtered, and dried under reduced pressure to afford dione 5a (0.424 g,
1
0.924 mmol, 91%) as an orange powder. 5a: H NMR (CDCl3) δ
8.85 (s, 2H, ArH), 8.64 (d, J = 2.0 Hz, 2H, ArH), 7.74 (dd, J = 2.0, 8.4
Hz, 2H, ArH), 7.56 (d, J = 8.4 Hz, 2H, ArH), 1.42 (s, 18H, CH3); MS
(EI, positive mode) (m/z): [M]+ calcd for C28H26O2S2, 459; found,
459.
Synthesis of Dione 5b. A solution of phthalic acid 4b (0.250 g,
0.424 mmol) in DMF (1 mL) and thionyl chloride (5.1 mL) was
stirred for 4 h at room temperature, before all volatiles were removed
under reduced pressure. A solution of aluminum trichloride (1.40 g,
10.5 mmol) in carbon disulfide (10 mL) was added, and the resulting
mixture was stirred for 16 h at room temperature. Then, the reaction
mixture was poured into water (20 mL) and the organic layer was
extracted with dichloromethane. The combined organic layers were
dried over anhydrous sodium sulfate, filtered, and dried under
reduced pressure to give an orange solid (0.278 g). Purification of the
crude orange solid by recrystallization from dichloromethane afforded
dione 5b (0.059 g, 0.12 mmol, 25%) as an orange powder. 5b: mp >
300 °C; 1H NMR (CDCl3) δ 8.93 (s, 2H, ArH), 8.59 (d, J = 8.4 Hz,
2H, ArH), 7.63 (d, J = 2.0 Hz, 2H, ArH), 7.53 (dd, J = 8.4, 2.0 Hz,
2H, ArH), 1.40 (s, 18H, CH3); 13C NMR (CDCl3) δ 81.1 (C), 156.9
(C), 135.6 (C), 132.6 (C), 131.9 (C), 131.5 (CH), 131.4 (CH),
128.4 (C), 125.0 (C), 124.8 (C), 35.4 (C), 30.9 (CH3); 77Se NMR
(CDCl3) δ 340.5 (s); HRMS (ESI-TOF, positive mode) (m/z): ([M
+ Na]+) calcd for C28H26NaO280Se2, 577.0161; found, 577.0175; anal.
calcd for C28H26O2Se2: C, 60.88; H, 4.74%; found: C, 60.99; H,
4.55%.
Synthesis of Diol 6a. A suspension of 3-bromo-1,2,4,5-
tetramethylbenznene (0.465 g, 2.18 mmol), magnesium turnings
(0.106 g, 4.36 mmol), and zinc chloride (0.009 g, 0.07 mmol) in THF
(10 mL) was stirred for 4 h under reflux. After cooling to room
temperature, the suspension was added to a solution of dione 5a
(0.100 g, 0.218 mmol) in THF (30 mL) at room temperature. The
reaction mixture was stirred for 20 h under reflux, before being poured
into a saturated solution of ammonium chloride. The resulting
suspension was filtered, and the organic layer of the filtrate was
extracted with ether. The combined organic layers were dried over
anhydrous sodium sulfate, filtered, and dried under reduced pressure
to give a crude brown solid. Separation of the crude brown solid by
column chromatography on silica gel (eluent: dichloromethane)
afforded diol 6a as a diastereomeric mixture (0.081 g, 1.1 mmol,
1
0.33 mmol, 31%) as a red powder. 7a: mp > 300 °C; H NMR
(CDCl3) δ 7.01 (s, 2H, ArH), 6.92 (dd, J = 8.2, 2.0 Hz, 2H, ArH),
6.81 (d, J = 8.2 Hz, 2H, ArH), 6.34 (d, J = 2.0 Hz, 2H, ArH), 5.72 (s,
2H, ArH), 2.28 (s, 12H, CH3), 1.96 (s, 12H, CH3), 1.01 (s, 18H,
CH3); HRMS (ESI-TOF, positive mode) (m/z): ([M + Na]+) calcd
for C48H52NaS2, 715.3408; found, 715.3412; anal. calcd for C48H52S2:
C, 83.19; H, 7.56%; found: C, 82.90; H, 7.30%. Satisfactory 13C NMR
data of 7a could not be obtained due to its low solubility in common
organic solvents.
Synthesis of Quinoid 7b. A suspension of bromo-2,3,5,6-
tetramethylbenznene (0.386 g, 1.81 mmol), magnesium turnings
(0.088 g, 3.6 mmol), and zinc chloride (0.020 g, 0.15 mmol) in THF
(10 mL) was stirred for 4 h under reflux. After cooling to room
temperature, the suspension was added to a solution of dione 5b
(0.100 g, 0.218 mmol) in THF (10 mL) at room temperature. Then,
the reaction mixture was stirred for 20 h under reflux, before being
poured into a solution of tin(II) chloride dihydrate (0.816 g, 3.62
mmol), 1.0 mol/L hydrochloric acid (3.0 mL), and water (1.0 mL) at
room temperature. After stirring for 2 h at room temperature, the
solution was extracted with dichloromethane. The organic layer was
separated and dried over anhydrous sodium sulfate, filtered, and
concentrated under reduced pressure. Separation of the crude residue
G
DOI: 10.1021/acs.organomet.9b00100
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
by column chromatography on silica gel (eluent: hexane) afforded
quinoid 7b (0.089 g, 1.0 mmol, 63%) as a red powder. 7b: mp > 300
°C; 1H NMR (CDCl3) δ 7.09 (d, J = 2.0 Hz, 2H, ArH), 7.02 (s, 2H,
ArH), 6.82 (dd, J = 8.4, 2.0 Hz, 2H, ArH), 6.34 (d, J = 8.4 Hz, 2H,
ArH), 6.04 (s, 2H, ArH), 2.28 (s, 12H, CH3), 1.95 (s, 12H, CH3),
1.21 (s, 18H, CH3); 13C NMR (CDCl3) δ 150.2 (C), 137.7 (C),
133.9 (C), 132.9 (C), 132.4 (C), 130.9 (C), 130.7 (CH), 130.0 (C),
128.6 (C), 128.3 (CH), 128.1 (C), 124.2 (CH), 124.0 (CH), 121.5
(CH), 34.4 (C), 30.9 (CH3), 20.2 (CH3), 16.3 (CH3); MS (ESI-
TOF, positive mode) (m/z): [M]+ calcd for C48H5280Se2, 788; found,
788; anal. calcd for C48H52Se2: C, 73.27; H, 6.66%; found: C, 73.30;
H, 6.79%.
Reaction of Diol 6a with Tetrafluoroboric Acid. An ethereal
solution of tetrafluoroboric acid (53%, 0.044 g, 0.27 mmol) was added
to a solution of diol 6a (0.020 g, 0.028 mmol) in dichloromethane (5
mL) at room temperature. After stirring the solution for 30 min, the
absorption bands of 6a in the UV−vis−NIR spectrum had
disappeared and those for 1a were detected. The solution was
added dropwise to cooled hexane (50 mL) to afford a brown
suspension. Separation of the suspension using a centrifuge afforded
dicationic salt 1a (6.2 mg, 0.061 mmol, 23%) as a brown powder. 1a:
mp 280 °C (dec.); anal. calcd for C48H52B2F8S2: C, 66.52; H, 6.05%;
found: C, 66.32; H, 6.08%.
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.9b00100.
■
S
X-ray diffraction analysis; ESR spectra of 8a and 8b;
1
theoretical calculations; H, 13C, and 77Se NMR spectra
of 1a and 1b (PDF)
Accession Codes
CCDC 1896933 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The Cam-
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Author
*E-mail: nagahora@fukuoka-u.ac.jp.
ORCID
■
Reaction of Quinoid 7a with Nitrosonium Tetrafluoroborate. A
0.43 mol/L solution of nitrosonium tetrafluoroborate in CD3CN (100
μL) was added to a solution of quinoid 7a (5.0 mg, 7.2 μmol) in
CDCl3 (448 μL) and CD3CN (12 μL) at room temperature. The
Noriyoshi Nagahora: 0000-0002-9663-0677
Notes
The authors declare no competing financial interest.
1
formation of 1a was detected by NMR spectroscopy. 1a: H NMR
ACKNOWLEDGMENTS
■
(CDCl3/CD3CN = 8:2) δ 9.58 (s, 2H, ArH), 8.89 (d, J = 8.8 Hz, 2H,
ArH), 8.69 (dd, J = 9.0 Hz, 2.0 Hz, 2H, ArH), 8.06 (d, J = 2.0 Hz, 2H,
ArH), 7.51 (s, 2H, ArH), 2.46 (s, 12H, CH3), 1.69 (s, 12H, CH3),
1.34 (s, 18H, CH3); 13C NMR (CDCl3/CD3CN = 8:2) δ 176.3 (C),
156.6 (C), 152.9 (C), 141.6 (CH), 139.6 (C), 136.4 (CH), 135.3
(C), 134.5 (CH), 132.6 (C), 132.1 (C), 131.6 (C), 130.9 (C), 129.7
(CH), 128.4 (CH), 35.7 (C), 29.8 (CH3), 19.3 (CH3), 16.9 (CH3);
19F NMR (CDCl3/CD3CN = 8:2) δ −146.67 (s, [10BF4]−), −146.71
(s, [11BF4]−); HRMS (ESI-TOF, positive mode) (m/z): ([M −
BF4]+) calcd for C48H52BF4S2, 779.3540; found, 779.3543.
This work was partially supported by the Collaborative
Research Program of the Institute for Chemical Research,
Kyoto University (grants 2017-101 and 2018-111) and a
Grant-in-Aid for Scientific Research (C) (JP16K05709) from
the Japan Society for the Promotion of Science. The authors
are grateful to Dr Y. Yamada (Fukuoka University, Japan) for
the theoretical investigations. The computation was carried out
using a computer resource offered by the Research Institute for
Information Technology, Kyushu University.
Reaction of Diol 6b with Tetrafluoroboric Acid. An ethereal
solution of tetrafluoroboric acid (53%, 0.044 g, 0.27 mmol) was added
to a solution of diol 6b (0.041 g, 0.050 mmol) in dichloromethane (5
mL) at room temperature. After the solution had been stirred for 30
min, the absorption for diol 6b disappeared in the UV−vis−NIR
spectrum and 1b was detected. The solution was added dropwise to
cooled hexane (50 mL) to give a brown suspension. Separation of the
suspension using a centrifuge afforded dicationic salt 1b (0.015 g,
0.092 mol, 34%) as a reddish purple powder. 1b: mp 256 °C (dec.);
anal. calcd for C48H52B2F8Se2: C, 60.03; H, 5.46%; found: C, 59.82;
H, 5.29%.
REFERENCES
■
(1) Anthony, J. E. The Larger Acenes: Versatile Organic Semi-
conductors. Angew. Chem., Int. Ed. 2008, 47, 452−483.
(2) (a) Weng, S.-Z.; Shukla, P.; Kuo, M.-Y.; Chang, Y.-C.; Sheu, H.-
S.; Chao, I.; Tao, Y.-T. Diazapentacene Derivatives as Thin-Film
Transistor Materials: Morphology Control in Realizing High-Field-
Effect Mobility. ACS Appl. Mater. Interfaces 2009, 1, 2071−2079.
(b) Islam, M. M.; Pola, S.; Tao, Y.-T. High Mobility n-Channel
Single-crystal Field-effect Transistors Based on 5,7,12,14-Tetrachloro-
6,13-diazapentacene. Chem. Commun. 2011, 47, 6356−6358.
(c) Miao, S.; Appleton, A. L.; Berger, N.; Barlow, S.; Marder, S. R.;
Hardcastle, K. I.; Bunz, U. H. F. 6,13-Diethynyl-5,7,12,14-
tetraazapentacene. Chem.-Eur. J. 2009, 15, 4990−4993.
Reaction of Quinoid 7b with Nitrosonium Tetrafluoroborate. A
0.43 mol/L solution of nitrosonium tetrafluoroborate in CD3CN (88
μL) was added to a solution of quinoid 7b (5.0 mg, 6.4 μmol) in
CDCl3 (448 μL) and CD3CN (24 μL) at room temperature. The
(3) (a) Agou, T.; Kobayashi, J.; Kawashima, T. Syntheses, Structure,
and Optical Properties of Ladder-Type Fused Azaborines. Org. Lett.
2006, 8, 2241−2244. (b) Agou, T.; Kobayashi, J.; Kawashima, T.
Electronic and Optical Properties of Ladder-Type Heteraborins.
Chem.-Eur. J. 2007, 13, 8051−8060.
1
formation of 1b was detected by NMR spectroscopy. 1b: H NMR
(CDCl3/CD3CN = 8:2) δ 9.67 (s, 2H, ArH), 9.02 (d, J = 2.0 Hz, 2H,
ArH), 8.26 (d, J = 9.2 Hz, 2H, ArH), 8.02 (dd, J = 9.2 Hz, 2.0 Hz, 2H,
ArH), 7.47 (s, 2H, ArH), 2.45 (s, 12H, CH3), 1.69 (s, 12H, CH3),
1.55 (s, 18H, CH3); 13C NMR (CDCl3/CD3CN = 8:2) δ 175.8 (C),
167.2 (C), 161.8 (C), 143.5 (C), 139.4 (CH), 137.4 (CH), 135.1 (C
× 2), 133.9 (CH), 131.5 (CH), 130.7 (C), 130.5 (C), 127.5 (CH),
37.5 (C), 29.3 (CH3), 19.0 (CH3), 16.7 (CH3) (one quaternary 13C
NMR signal for 1b cannot be assigned due to its low solubility in
common organic solvents.); 19F NMR (CDCl3/CD3CN = 8:2) δ
−146.12 (s, [10BF4]−), −146.17 (s, [11BF4]−); 77Se NMR (CDCl3/
CD3CN = 8:2) δ 727.1 (s); HRMS (ESI-TOF, positive mode) (m/z):
([M − BF4]+) calcd for C48H52BF480Se2, 875.2429; found, 875.2438.
(4) Hetarenes and Related Ring Systems, Six-Membered Hetarenes
with One Chalcogen. In Science of Synthesis; Thomas, E. J., Ed.;
Thieme, 2004; Vol. 14, pp 1−854.
(5) (a) Price, C. C.; Hori, M.; Parasaran, T.; Polk, M. Thiabenzenes.
IV. 1- and 2-Thianaphthalenes and 10-Thiaanthracenes. Evidence for
Cyclic Conjugation. J. Am. Chem. Soc. 1963, 85, 2278−2282.
́
́
(b) Renson, M.; Pirson, P. Isoselenochromannone et Cation
́
́
́
Selena-2 Naphtalenium. Bull. Soc. Chim. Belg. 1966, 75, 456−464.
(c) Hori, M.; Kataoka, T.; Shimizu, H. Stability of Thiabenzenes.
Chem. Pharm. Bull. 1974, 22, 2485−2487. (d) Sashida, H.; Minamida,
H
DOI: 10.1021/acs.organomet.9b00100
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
H. Studies on Tellurium-containing Heterocycles. Part 12. 2-
Substituted 1-Benzotelluropyrylium Salts: Synthesis and Reactions
with Nucleophiles. J. Chem. Soc., Perkin Trans. 1 1999, 1665−1670.
(e) Sashida, H.; Minamida, H. A Facile Preparation of 1-
Benzoselenopyrylium Salts. J. Chem. Res. 2000, 569−571. (f) Sashida,
H.; Yoshida, M.; Minamida, H.; Teranishi, M. Reaction of 1-
Benzoselenopyrylium Salts with Grignard Reagents: Formation of 2,4-
Disubstituted Selenochromenes and Their Conversion into the
Corresponding 1-Benzoselenopyrylium Salts. J. Heterocycl. Chem.
2002, 39, 405−409. (g) Sashida, H.; Yoshida, M. A Simple and
Practical Preparation of 2,4-Disubstituted 1-Benzotelluropyrylium
Salts. Heterocycles 2002, 57, 649−656.
(13) Nakano, M.; Niimi, K.; Miyazaki, E.; Osaka, I.; Takimiya, K.
Isomerically Pure Anthra[2,3-b:6,7-b′]-difuran (anti-ADF), -dithio-
phene (anti-ADT), and -diselenophene (anti-ADS): Selective Syn-
thesis, Electronic Structures, and Application to Organic Field-Effect
Transistors. J. Org. Chem. 2012, 77, 8099−8111.
(14) Okamoto, T.; Kudoh, K.; Wakamiya, A.; Yamaguchi, S. General
Synthesis of Thiophene and Selenophene-Based Heteroacenes. Org.
Lett. 2005, 7, 5301−5304.
(15) Kalinowski, H.-O.; Berger, S.; Braun, S. Carbon-13 NMR
Spectroscopy; John Wiley & Sons, 1988.
(16) Christiaens, L.; Piette, J.-L.; Laitem, L.; Baiwir, M.; Denoel, J.;
77
́
́
́
Llabres, G. La resonance magnetique du Se dans des composes
organiques. Magn. Reson. Chem. 1976, 8, 354−356.
(17) Sandor, P.; Radics, L. High Resolution NMR Spectroscopy of
Heteroaromatic Cations. II-Pyrylium, Thiapyrylium and Seleninium
(6) (a) Fukui, K.; Matsumoto, T. Synthetic Studies of Flavone
Derivatives. II. The Synthesis of Meliternatin and Some 3,5-
Dimethoxy-6,7-methylenedioxyflavones. Bull. Chem. Soc. Jpn. 1963,
36, 806−809. (b) Seidl, H.; Biemann, K. Reaction of Thioxanthylium
Perchlorate with Diazomethane. J. Heterocycl. Chem. 1967, 4, 209−
́
Cations. Magn. Reson. Chem. 1981, 16, 148−155.
(18) Sashida, H.; Ohyanagi, K.; Minoura, M.; Akiba, K.-y. Studies on
Tellurium-containing Heterocycles. Part 18. Preparation and
Structure of 2-Benzotelluropyrylium Salts and 2-Benzoselenopyrylium
Salts. J. Chem. Soc., Perkin Trans. 1 2002, 606−612.
215. (c) Hori, M.; Kataoka, T.; Hsu
Selenaanthracene Derivatives. Chem. Pharm. Bull. 1974, 22, 15−20.
(d) Hori, M.; Kataoka, T.; Shimizu, H.; Hsu, C.-F.; Hasegawa, Y.;
̈
, C.-F. Synthesis of 10-
̈
(19) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Petersson,
G. A.; Nakatsuji, H.; Li, X.; Caricato, M.; Marenich, A. V.; Bloino, J.;
Janesko, B. G.; Gomperts, R.; Mennucci, B.; Hratchian, H. P.; Ortiz, J.
V.; Izmaylov, A. F.; Sonnenberg, J. L.; Williams-Young, D.; Ding, F.;
Lipparini, F.; Egidi, F.; Goings, J.; Peng, B.; Petrone, A.; Henderson,
T.; Ranasinghe, D.; Zakrzewski, V. G.; Gao, J.; Rega, N.; Zheng, G.;
Liang, W.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.;
Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.;
Throssell, K.; Montgomery, Jr., J. A.; Peralta, J. E.; Ogliaro, F.;
Bearpark, M. J.; Heyd, J. J.; Brothers, E. N.; Kudin, K. N.; Staroverov,
V. N.; Keith, T. A.; Kobayashi, R.; Normand, J.; Raghavachari, K.;
Rendell, A. P.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.;
Millam, J. M.; Klene, M.; Adamo, C.; Cammi, R.; Ochterski, J. W.;
Martin, R. L.; Morokuma, K.; Farkas, O.; Foresman, J. B.; Fox, D. J.
Gaussian 16, revision A.03; Gaussian, Inc.: Wallingford, CT, 2016.
(20) Singly occupied molecular orbital, highest occupied molecular
orbital, and lowest unoccupied molecular orbital are abbreviated to
SOMO, HOMO, and LUMO, respectively.
(21) (a) Schleyer, P. R.; Maerker, C.; Dransfeld, A.; Jiao, H.;
Hommes, N. J. R. E. Nucleus-Independent Chemical Shifts: A Simple
and Efficient Aromaticity Probe. J. Am. Chem. Soc. 1996, 118, 6317−
6318. (b) Chen, Z.; Wannere, C. S.; Corminboeuf, C.; Puchta, R.;
Schleyer, P. vR. Nucleus-Independent Chemical Shifts (NICS) as an
Aromaticity Criterion. Chem. Rev. 2005, 105, 3842−3888.
(22) Parent benzene and thiopyrylium cation at this level were
estimated to be −10.00 and −9.56 ppm, respectively.
(23) Reed, A. E.; Curtiss, L. A.; Weinhold, F. Intermolecular
Interactions from a Natural Bond Orbital, Donor−Acceptor View-
point. Chem. Rev. 1988, 88, 899−926.
(24) (a) Hori, T.; Sharpless, K. B. Selenium-catalyzed Nonradical
Chlorination of Olefins with N-Chlorosuccinimide. J. Org. Chem.
1979, 44, 4204−4208. (b) Kwon, T. S.; Kondo, S.; Kunisada, H.;
Yuki, Y. Synthesis of Polystyrenes with Arylseleno Groups at the
Terminal Bond, by the Free Radical Polymerization of Styrene in the
Presence of Diaryl Diselenides, and Their Conversion to End
Functional Polymers. Eur. Polym. J. 1999, 35, 727−737.
(25) (a) Smith, L. I.; Nichols, J. The Synthesis of Aldehydes from
Grignard Reagents. II. Polymethylbenzaldehydes. J. Org. Chem. 1941,
6, 489−506. (b) Zysman-Colman, E.; Arias, K.; Siegel, J. S. Synthesis
of Arylbromides from Arenes and N-Bromosuccinimide (NBS) in
Acetonitrile−A Convenient Method for Aromatic Bromination. Can.
J. Chem. 2009, 87, 440−447.
Eyama, N. Reactivities of Heteroaromatic Cations containing a Group
VIB Element in Nucleophilic Reactions. Reactions of 9-Phenyl-
xanthylium, -thioxanthylium, and -selenoxanthylium Salts with
Amines, Sodium Phenolate, and Sodium Benzenethiolate. J. Chem.
Soc., Perkin Trans. 1 1988, 2271−2276. (e) Bedlek, J. M.; Valentino,
M. R.; Boyd, M. K. Substituent Effects on Carbocation Photophysics:
9-Arylxanthyl and 9-Arylthioxanthyl Carbocations. J. Photochem.
Photobiol., A 1996, 94, 7−13. (f) Okada, K.; Imakura, T.; Oda, M.;
Kajiwara, A.; Kamachi, M.; Yamaguchi, M. Remarkable Heteroatom
Dependence of the Spin Multiplicity in the Ground State of 9,9′-(m-
Phenylene)dixanthyl and -dithioxanthyl Diradicals. J. Am. Chem. Soc.
1997, 119, 5740−5741. (g) Erabi, T.; Asahara, M.; Miyamoto, M.;
Goto, K.; Wada, M. 9-Phenylxanthen-9-ylium and 9-Phenylthiox-
anthen-9-ylium Ions: Comparison of o- and p-Substitutions in the 9-
Phenyl Group by Cyclic Voltammetry and Visible Spectra. Bull. Chem.
Soc. Jpn. 2002, 75, 1325−1332. (h) Browne, W. R.; Pollard, M. M.; de
Lange, B.; Meetsma, A.; Feringa, B. L. Reversible Three-State
Switching of Luminescence: A New Twist to Electro- and
Photochromic Behavior. J. Am. Chem. Soc. 2006, 128, 12412−
12413. (i) Lutkus, L. V.; Irving, H. E.; Davies, K. S.; Hill, J. E.;
Lohman, J. E.; Eskew, M. W.; Detty, M. R.; McCormick, T. M.
Photocatalytic Aerobic Thiol Oxidation with a Self-Sensitized
Tellurorhodamine Chromophore. Organometallics 2017, 36, 2588−
2596.
(7) (a) Young, T. E.; Ohnmacht, C. J. A Correlation of the Lowest
̈
Huckel Molecular Orbital Transition Energies with the Lb Band
Frequencies of Thiapyrylium Ions. J. Org. Chem. 1967, 32, 444−449.
(b) Kryman, M. W.; McCormick, T. M.; Detty, M. R. Longer-
Wavelength-Absorbing, Extended Chalcogenorhodamine Dyes. Orga-
nometallics 2016, 35, 1944−1955.
(8) Kassaee, M. Z.; Jalalimanesh, N.; Musavi, S. M. Effects of Group
14−16 Heteroatoms on the Aromaticity of Benzene at DFT Level. J.
Mol. Struct.: THEOCHEM 2007, 816, 153−160.
(9) Freund, T.; Scherf, U.; Mu
̈
llen, K. Leiterpolymere mit
Heteroacen-Gerust. Angew. Chem. 1994, 106, 2547−2549.
̈
(10) Reisch, H. A.; Scherf, U. Novel Phenoxy and Thiophenoxy
Substituted Poly(para-phenylenevinylene)s. Macromol. Chem. Phys.
1999, 200, 552−561.
(11) Dong, S.; Herng, T. S.; Gopalakrishna, T. Y.; Phan, H.; Lim, Z.
L.; Hu, P.; Webster, R. D.; Ding, J.; Chi, C. Extended Bis(benzothia)-
quinodimethanes and Their Dications: From Singlet Diradicaloids to
Isoelectronic Structures of Long Acenes. Angew. Chem., Int. Ed. 2016,
55, 9316−9320.
(12) For a similar ipso-acylation of a selenoaryl group, see: Detty, M.
R.; Murray, B. J. Cyclization of 3-(Arylchalcogeno)propenoyl
Chlorides. 2. Chalcogen and Substituent Control in the Regiochem-
istry of Intramolecular Acylation. Preparation of Benzo[b]-
telluropyrones. J. Am. Chem. Soc. 1983, 105, 883−890.
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DOI: 10.1021/acs.organomet.9b00100
Organometallics XXXX, XXX, XXX−XXX