Effect of Cp-Ligand Methylation on Rhodium(III)-Catalyzed Annulations of Aromatic Carboxylic Acids with Alkynes: Synthesis of Isocoumarins and PAHs for Organic Light-Emitting Devices

Article abstract of DOI:10.1002/cplu.202000048

An efficient protocol was developed for the synthesis of π-extended isocoumarins and polycyclic aromatic hydrocarbons based on the oxidative coupling of aromatic carboxylic acids with internal alkynes catalyzed by (cyclopentadienyl)rhodium complexes. The

Full text of DOI:10.1002/cplu.202000048

Accepted Article
Title: Effect of Cp-Ligand Methylation on Rh(III)-Catalyzed Annulations
of Aromatic Carboxylic Acids with Alkynes: Synthesis of
Isocoumarins and PAHs for Organic Light-Emitting Devices
Authors: Alexander P. Molotkov, Mikhail A. Arsenov, Daniil A.
Kapustin, Dmitry V. Muratov, Nikolay E. Shepel', Yury V.
Fedorov, Alexander F. Smol’yakov, Elena I. Knyazeva, Dmitry
A. Lypenko, Artem V. Dmitriev, Alexey E. Aleksandrov,
Eugeny I. Maltsev, and Dmitry Loginov
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to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
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To be cited as: ChemPlusChem 10.1002/cplu.202000048
Link to VoR: http://dx.doi.org/10.1002/cplu.202000048
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Effect of Cp-Ligand Methylation on Rh(III)-Catalyzed Annulations of Aromatic
Carboxylic Acids with Alkynes: Synthesis of Isocoumarins and PAHs for Organic Light-
Emitting Devices
Alexander P. Molotkov,[a] Mikhail A. Arsenov,[a] Daniil A. Kapustin,[a] Dmitry V. Muratov,[a]
Nikolay E. Shepel',[a] Yury V. Fedorov,[a] Alexander F. Smol’yakov,[a,b,c] Elena I. Knyazeva,[b]
Dmitry A. Lypenko,[d] Artem V. Dmitriev,[d] Alexey E. Aleksandrov,[d] Eugeny I. Maltsev,[d]
Dmitry A. Loginov*[a]
Abstract
An efficient protocol for the synthesis of -extended isocoumarins and polycyclic
aromatic hydrocarbons based on the oxidative coupling of aromatic carboxylic acids with
internal alkynes catalyzed by (cyclopentadienyl)rhodium complexes was developed. The
chemoselectivity strongly depends on the methylation of the Cp ligand. The pentamethyl
derivative [Cp*RhCl2]2 predominantly gives isocoumarin moiety, while the non-methylated
complex [CpRhI2]n results in naphthalene derivatives. The polyaromatic carboxylic acids (such
as 1-naphthoic acid, 1-pyrenecarboxylic acid, fluorene-1-carboxylic acid, and dibenzofuran-4-
carboxylic acid) are suitable for this approach. A mixture of Cp*H/RhCl3 can be used as a
catalyst instead of [Cp*RhCl2]2. The structures of 3,4-diphenylindeno[1,2-h]isochromen-1(11H)-
one and 7,10-dimethyl-8,9-diphenylbenzo[pqr]tetraphene were determined by X-ray diffraction.
The optical properties of the compounds prepared were studied. 7,8-Diphenyl-10H-
phenaleno[1,9-gh]isochromen-10-one was employed as an emissive layer for OLED
manufacturing. The OLED emits yellow-green light of maximum intensity 1740 cd∙m−2 at 15 V.
[a] A. P. Molotkov, M. A. Arsenov, D. A. Kapustin, Dr. D. V. Muratov, Dr. N. E. Shepel', Prof.
Dr. Y. V. Fedorov, Dr. A. F. Smol’yakov, Prof. Dr. D. A. Loginov
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Science,
28 ul. Vavilova, 119991 Moscow, Russian Federation
E-Mail: dloginov@ineos.ac.ru
Homepage: http://www.ineos.ac.ru/en
[b] Dr. A. F. Smol’yakov, E. I. Knyazeva
Faculty of Science, RUDN University, 6 Miklukho-Maklaya St., Moscow 117198, Russian
Federation
[c] Dr. A. F. Smol’yakov
Plekhanov Russian University of Economics, Stremyanny per. 36, Moscow, 117997, Russian
Federation
[d] Dr. D. A. Lypenko, Dr. A. V. Dmitriev, A. E. Aleksandrov, Prof. Dr. E. I. Maltsev
A.N. Frumkin Institute of Physical Chemistry and Electrochemistry of the Russian Academy of
Sciences, Leninsky Prosp. 31, bld.4, Moscow 119071, Russian Federation
1
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Introduction
In the last few decades, organic light-emitting diodes (OLEDs) have attracted much
attention from chemists and material scientists due to their wide application in light sources and
flat-panel color.[1] Tang and VanSlyke pioneered OLED technology.[2] In 1987, they constructed
the first organic light-emitting diode using 8-hydroxyquinoline aluminum as an emissive layer.
Isocoumarins, as well as polycyclic aromatic hydrocarbons (PAHs), are of special interest due to
their high stability and fluorescent properties. In particular, these compounds have a flat -
conjugated structure, which provides a strong increase in the Stokes shift of fluorescence
emission.[3] It was shown that tetracene and pyrene derivatives can be used for the OLED
construction as transport and emitting layers.[4]
Transition metal catalyzed organic reactions are a promising approach for the
construction of isocoumarins and PAHs. For example, various palladium-catalyzed intra- and
intermolecular cyclization reactions of halogen-substituted benzene derivatives have been well
established as one of the most efficient strategies for the synthesis of isocoumarins.[5] In a similar
manner, it was found that the coupling of aryl iodides with alkynes can be used for the
construction of a naphthalene moiety.[6] Arylboronic acids, triarylmethanols, and aroyl chlorides
were also successfully introduced into this reaction using rhodium and iridium catalysis.[7] But
the main disadvantage of these protocols is the low atom economy due to a large amount of
waste. At the same time, straightforward C–H activation reactions usually require the presence of
directing groups (e.g. pyrazole and ketone functions) to provide selectivity.[8] Cramer with co-
workers reported the synthesis of various naphthalene and anthracene derivatives via C–H
functionalization without any leaving and directing groups.[9] However, it should be noted that
this protocol allows to selectively obtain only products with a linear structure.
The oxidative coupling of aromatic carboxylic acids with internal alkynes via C–H
activation is of particular interest due to the great step and atom economy of this method, as well
as the possibility to synthesize both isocoumarins and PAHs.[10] The reaction proceeds through
the chelation-assistance of the carboxylic group, which provides the selectivity of C–H activation
in the ortho position.[11] Satoh and Miura were pioneers in the development of this strategy.[12] In
particular, they showed that the pentamethylcyclopentadienyl complex [Cp*RhCl2]2 effectively
catalyzes the coupling of benzoic acids with internal alkynes in the presence of Cu(OAc)2 as an
oxidant, predominantly giving isocoumarins with a side formation of naphthalenes (3–14%).[13]
The latter products are formed as a result of decarboxylation. In contrast, we found that the non-
methylated complex [CpRhI2]n in the same reaction selectively gives only naphthalene
derivatives.[14] Shibata and Tanaka with co-workers showed that the oxidant nature (Cu(II) or
Ag(I)) also have a crucial impact on the selectivity in the case of usage of electron-deficient
2
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rhodium complex [CpʹRhCl2]2 (Cp = 1,3-(COOEt)2-C5Me3) as a catalyst.[15] In the last decade,
efficient catalytic systems with different selectivity based on other transition metal complexes
have been also developed.[16,17]
Herein we report on the use of the rhodium complexes [Cp*RhCl2]2 and [CpRhI2]n for
the synthesis of -extended isocoumarins and PAHs using various polyaromatic carboxylic acids
(e.g. 1-naphthoic acid, 1-pyrenecarboxylic acid, fluorene-1-carboxylic acid, etc.) as coupling
partners. Moreover, we investigated the fluorescent properties of the compounds prepared and
used them for the OLED manufacturing.
Results and Discussion
The general procedure for the synthesis of isocoumarins and PAHs is given in Table 1.
The complexes [Cp*RhCl2]2 and [CpRhI2]n were chosen as catalysts, because they are easily
available in comparison with other known catalytic systems. Thus, the non-methylated complex
[CpRhI2]n can be easily synthesized by a two-step procedure based on the reaction of
[(cod)RhCl]2 (cod = 1,5-cyclooctadiene) with CpTl followed by treatment of the resulting
CpRh(cod) by iodine in a total yield of 97%,[18] while the methylated derivative [Cp*RhCl2]2 is
prepared by direct interaction of rhodium chloride with C5Me5H.[19] As can be seen from Table
1, in the case of benzoic acid and its derivatives, the selectivity of the reaction strongly depends
on the methylation of the Cp ligand in the catalyst (Table 1, Entries 1–7), predominantly giving
isocoumarins for [Cp*RhCl2]2 and naphthalene derivatives for [CpRhI2]n. The reaction is tolerant
to the functional groups Cl and MeO in the aromatic ring. At the same time, the presence of the
NO2-group significantly reduces the yields of the desired products (Table 1, Entry 7). Diphenyl-,
diethyl- and bis(p-methoxyphenyl)acetylenes as well as 1-phenyl-1-propyne are suitable for the
reaction. However, attempts to perform oxidative coupling of benzoic acid with 1,4-dimethoxy-
2-butyne, bis(trimethylsilyl)acetylene or phenylacetylene have failed.
The developed synthetic protocols have been successfully extended to polyaromatic
carboxylic acids, such as 1-naphthoic, fluorene-1-carboxylic, dibenzofuran-4-carboxylic and 1-
pyrenecarboxylic acids (Table 1, Entries 8–16). It is interesting to note that although the complex
[Cp*RhCl2]2 usually leads to isocoumarins, the catalyzed reaction of dibenzofuran-4-carboxylic
acid with diphenylacetylene affords naphthalene 2l as a sole product (Table 1, Entry 12).
Similarly, the replacement of diphenylacetylene by diethylacetylene in coupling with fluorene-1-
carboxylic acid catalyzed by [CpRhI2]2 results in the formation of isocoumarin 1k instead of the
expected naphthalene derivative (Table 1, Entry 11 vs 9). The low selectivity of the
[Cp*RhCl2]2-catalyzed reaction of 1-pyrenecarboxylic acid with diphenylacetylene is an
additional exception to the general tendency (Table 1, Entry 13). The observed non-selectivity
3
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may be explained by changes of the oxidation potentials of the reaction intermediates as a result
of the influence of different functional groups.[16d,20] It should be noted that the oxidation
potentials depend not only on the nature of the carboxylic acid but also on the electronic
properties of the incoming alkyne and the supporting ligand at the rhodium atom. The key
possible intermediate A is presented on Scheme 1. When the redox potential of the Cu(II)/Cu(I)
couple is sufficient for the oxidation of A, the reaction proceeds via the reductive elimination of
rhodium to give the isocoumarin product. Otherwise, the decarboxylation is more favorable and
leads to the naphthalene derivatives after insertion of the second alkyne molecule.
Scheme 1. The key intermediate A and possible reaction pathways for the oxidative coupling of
aromatic carboxylic acids with internal alkynes.
The 1H NMR spectra of isocoumarins 1a–e, 1h–i, 1k, 1m, and 1n display strongly down-
field shifted doublet at more than 8.00 ppm. In contrast, the phenyl-substituted naphthalene
derivatives 2a, 2d–g, 2i, 2j, 2l, 2m, and 2o show a characteristic multiplet signal in the range of
6.8–7.1 ppm, thus making 1H NMR spectroscopy sufficiently informative to monitor the reaction
selectivity. The structures of 1i and 2o were confirmed by single-crystal X-ray diffraction study
(Fig. 1 and 2).[21] The polyaromatic moiety is ca. planar for both compounds, being slightly
twisted in the case of benzopyrene derivative 2o. The phenyl substituents are not coplanar with a
polyaromatic moiety (dihedral angles are 27.5º and 80.2º for 1i; 70.5º and 77.6º for 2o).
Figure 1. X-Ray diffraction structure of compound 1i. Hydrogen atoms are omitted for clarity.
4
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Figure 2. X-Ray diffraction structure of compound 2o. Hydrogen atoms are omitted for clarity.
To simplify the reaction procedure, we tested mixtures of RhCl3 with various
cyclopentadienes as catalytic systems (Table 2).[22] As a model reaction, we chose the oxidative
coupling of benzoic acid with diphenylacetylene. It was found that a mixture of RhCl3 with
C5Me5H (Table 2, Entry 1) has the same selectivity and catalytic activity as the complex
[Cp*RhCl2]2 (Table 1, Entry 1), giving predominantly isocoumarin 1a. Unexpectedly, the use of
non-methylated cyclopentadiene C5H6 did not give any organic products (Table 2, Entry 4). In a
similar manner, methyl- and tetramethylcyclopentadienes proved to be inefficient as additives to
RhCl3 in this reaction (Table 2, Entries 2 and 3). At the same time, rhodium chloride without any
supporting ligands gives naphthalene 2a in 31% yield (Table 2, Entry 5), suggesting that the
presence of cyclopentadienes less substituted than C5Me5H can poison the catalyst. It may be
explained by the formation of inactive rhodium compounds, for example, rhodocenium cations.
5
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Table 1. The reaction of aromatic carboxylic acids with internal alkynes.[a]
Entry
1
Acid
R1, R2
Ph, Ph
Isocoumarin product, yield [%][b]
Napthalene product, yield [%][b]
O
Ph
Ph
O
Benzoic acid
Ph
Ph
Ph
Ph
2a, 2 (91)
1a, 51 (-)
2
Benzoic acid
p-MeOC6H4, p-MeOC6H4
2b, 4 (66)
1b, 56 (12)
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O
Et
Et
Et
O
3
4
5
6
Et, Et
Ph, Ph
Ph, Ph
Me, Ph
Benzoic acid
Et
Et
Et
2c, - (69)
1c, 88 (-)
O
O
4-Chlorobenzoic acid
4-Methoxybenzoic acid
4-Methoxybenzoic acid
Cl
Ph
Ph
2d, - (52)
1d, 52 (2)
O
O
MeO
Ph
Ph
2e, - (69)
1e, 53 (-)
Me
Ph
Ph
-
MeO
Me
2f, (40)
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Ph
Ph
Ph
Ph
7
8
9
Ph, Ph
Ph, Ph
Ph, Ph
-
4-Nitrobenzoic acid
O2N
2g, 7 (29)
-
1-Naphthoic acid
1h, 67
Fluorene-1-carboxylic acid
1i, 45 (-)
2i, - (27)
10
Me, Ph
-
Fluorene-1-carboxylic acid
2j, (33)
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11
12
Et, Et
-
Fluorene-1-carboxylic acid
1k, (15)
Ph, Ph
-
Dibenzofuran-4-carboxylic acid
2l, 57
13
14
Ph, Ph
1-Pyrenecarboxylic acid
2m, 36 (52)
1m, 29 (-)
p-MeOC6H4, p-MeOC6H4
-
1-Pyrenecarboxylic acid
1n, 62
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15
16
Me, Ph
-
-
1-Pyrenecarboxylic acid
2o, (73)
Et, Et
1-Pyrenecarboxylic acid
2p, (55)
[a] Reaction conditions: acid (0.50 mmol), alkyne (1.00 mmol), [Cp*RhCl2]2 (1 mol% of Rh, 0.0025 mmol), Cu(OAc)2∙2H2O (4 equiv, 2.00
[b]
mmol) in o-xylene, heating at 150ºC for 6 h, see general procedure. Yields are given for isolated products. Values in parentheses indicate yields
when
[CpRhI2]n
was
used
as
a
catalyst.
.
10
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Table 2. The oxidative coupling of benzoic acid with diphenylacetylene catalyzed by mixtures
of RhCl3 with cyclopentadienes.[a]
Entry
Cyclopentadiene
C5Me5H
1a, yield [%][b]
2a, yield [%][b]
1
2
3
4
84
5
-
7
-
C5HMe4H
C5H4MeH
C5H6
-
-
-
5
None
-
31
[a]
Reaction conditions: benzoic acid (0.50 mmol), diphenylacetylene (1.12 mmol), RhCl3 (2
mol%, 0.01 mmol), cyclopentadiene (12 mol%, 0.06 mmol), Cu(OAc)2∙2H2O (4 equiv, 2.00
mmol) in o-xylene, heating at 150 ºC for 6 h. [b] Yields are given for isolated products.
Photophysical Properties
Absorption and fluorescence spectra in CH3CN were measured to study the optical
properties of the prepared compounds (Table 3). Both isocoumarins and naphthalenes showed
fluorescence emission in the blue-green region (Fig. 3). For example, the absorption spectrum of
compound 2m demonstrates a set of absorption bands with different intensities. The most broad
and intense are one at 310 nm, a doublet of bands at 280 nm, several bands at 239, 382 and 401
nm (Fig. 4). There are several low-intensity bands that are responsible for the formation of the
shoulder in the absorption spectrum. To make spectral assignments, we calculated the electronic
absorption spectra for the most representative compounds (1m and 2m) using the TD-DFT
method. This method has earlier proven its usefulness for prediction of UV–Visible spectra of
organic dyes.[23] First of all, we tested various exchange–correlation functionals (B3LYP, CAM-
B3LYP, and PBE0) to compare the results of the energy gaps with the experimentally obtained
data (Table 4). In accordance with the general trend,[23] the best correlations were obtained for
the B3LYP and PBE0 functionals. The CAM-B3LYP functional overestimates the differences in
energy between the frontier orbitals. The lowest energy bands for both compounds mainly derive
from HOMO → LUMO orbitals, which correspond to the  → * transitions. These frontier
orbitals are located on the pyrene moiety (for details, see Supporting Information). It is
11
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interesting to note that the most intensive band for the isocoumarin compound 1m (310 nm)
involves the HOMO–2 → LUMO transition, which corresponds to charge transfer from phenyl
substituents to the pyrene moiety because the HOMO–2 orbital is located on the phenyl groups.
In the case of the naphthalene compound 2m, the high energy bands are formed by several
transitions and are difficult for interpretation.
The emission spectrum of 2m consists of two evident maxima, but a shoulder of about
500 nm indicates the existence of another maximum. Three Gauss curves fit yields 3 maxima at
426, 447 and 458 nm (Fig. 5).
Figure 3. The photo of acetonitrile solutions of 2g, 2i, 2m and 2o exposed to UV light (365 nm).
Experiment
Peak1
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Peak2
Peak3
Summ
4x106
3x106
2x106
4x106
3x106
2x106
1x106
1x106
0
600
0
200
250
300
350
400
450
500
550
15 000
20 000
25 000
Wavelength (nm)
Wavelength (1/cm)
Figure 4. The absorption spectrum of 2m in
CH3CN+CH2Cl2 (<1.0%), C = 2·10–5 M, L=1
cm and emission spectrum of 2m in
CH3CN+CH2Cl2 (<0.2%), C = 3.3·10–6 M, λex
= 382 nm, 20 °C.
Figure 5. Gauss curves approximation of the
emission spectrum of compound 2m:
experimental and mathematical approximation:
by component and summarized (fully
consistent with experimental).
We found that for both isocoumarin and naphthalene derivatives the additional -
conjugation as well as the introduction of donor substituents (Cl and OMe) at position 6 of 3,4-
diphenylisocoumarin (1a) and 1,2,3,4-tetraphenylnaphthalene (2a) leads to a slightly
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hypsochromic shift of the fluorescence emission (Table 3, Entries 3–6 and 8 vs 1, as well as
Entries 11–14 and 8 vs 9). In contrast, the introduction of a strong acceptor nitro group at
position 6 of 2a results in a bathochromic shift (Entry 10 vs 9). In the case of benzopyrene
compounds 2m, 2o and 2p the maxima of fluorescent emission only slightly depend on the
number of phenyl substituents (Entries 12–14).
Using the optimal excitation wavelength, the obtained luminescence spectra were used to
calculate the quantum yields (see Table 3). Surprisingly, isocoumarin derivatives showed low
quantum yields. In most cases except for the pyrene compound 1m (Table 3, Entries 8 vs 1–7)
their values are below 1%. Moreover, the replacement of phenyl substituents with ethyl groups
did not improve the fluorescence efficiency (Entry 2). In contrast, naphthalenes have rather high
quantum yields (Entries 11–14), which are comparable with quinine sulfate.
The absorption and fluorescence spectra for compounds 1m and 2m were also recorded
in dichloromethane, acetone, dimethylsulfoxide, and ethanol (see the Supporting Information).
No significant solvatochromic effects were observed. In particular, the maximum shifts of
absorption and emission bands are 6 and 12 nm, respectively, being smaller for the naphthalene
compound 2m (Table 5).
Table 3. Optical properties of compounds 1a,c,d,e,h,i,k,m and 2a,g,l,m,o,p.
Entry
Compoun Significant absorption
Emission
bands
Emission
quantum
yields φ (λex,
[nm])
d
maxima, extinction
coefficients ε (λmax, [nm]),
[L×mol–1×cm–1]
maxima,
[nm]
1
2
3
ε 295 = 14 865, ε 334 = 7 261,
ε 227 = 25 455
481 [a]
0.1% (330)
1a
1c
1d
ε269 = 7 290, ε279 = 6 160, ε260 403
0.4% (328)
0.2% (327)
= 5 950, ε328 = 2 830[c]
ε 300 = 13 462, ε 338 = 6 025,
ε 239 = 26 676
468 [a]
4
5
ε 259 = 34 358, ε 304 = 11 548
ε 285 = 30 885, ε 242 = 25 197,
ε 369 = 10 846, ε 385 = 7 544
ε 315 = 18 468, ε 363 = 12 433,
ε 253 = 13 290
406 [a]
440 [a]
<0.1% (315)
<0.1% (330)
1e
1h
6
7
8
451, 420,
399 [b]
0.4% (315)
4.2% (355)
1i
1k
1m
ε310 =17 000, ε298 = 17 500,
391, 411,
ε357 = 6 100[c]
434 [b]
ε 310 = 41 490, ε 373 = 21 147,
ε 355 = 13 836, ε 411 = 7 325,
ε 433= 8 680
502, 472,
447 [b]
9.2% (355) [d]
2.7% (365) [e]
9
10
ε 294 = 11 072, ε 239 = 45 956
ε277 = 21 433; ε323 = 6 244;
ε375 = 2 925
467 [a]
550
-
2a
2g
1.4% (380)
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11
12
ε269 = 65 642; ε292 = 31 559;
ε333 = 7 872; ε351 = 6 234
360, 375,
390 [b]
25.5% (335)
2l
ε310 = 31 715; ε280 = 24 493 [c]; 426, 447,
39.5% (382)
31.2% (364)
2m
ε239 = 23 033, ε382 = 14 862;
ε401 = 15 665
458 [b]
13
ε259 = 34 713; ε273 = 30 537;
ε296 = 27 033; ε308 = 34 523;
ε332 = 12 240; ε348 = 18 662;
ε364 = 7 188; ε383 = 12 232;
ε405 = 12 512
451, 444,
421 [b]
2o
14
ε307 = 35 000; ε295 = 26 700;
ε272 = 28 400, ε261 = 24 200;
ε385 = 13 800, ε406 = 14 500
422, 441,
462 [b]
37.8% (383)
2p
[a] Emission maxima are not well-defined due to low intensity. [b] All wavelength maxima are
obtained from Gauss curves consistent with the emission spectrum. [c] A doublet of bands. [d]
Fluorescence lifetime is equal to 1.58 ± 0.01 ns. [e] In solid state.
Table 4. The most intensive absorption bands for compounds 1m and 2m calculated at the
B3LYP/DZP, CAM-B3LYP/DZP and PBE0/DZP levels.
Compound
Experimental
λmax, [nm]
433
Calculated λmax, [nm]
B3LYP/DZP
403
CAM-B3LYP/DZP PBE0/DZP
348
326
273
354
272
266
392
356
303
406
323
303
1m
373
365
310
305
401
412
2m
310
327
280
310
Table 5. The long-wavelength absorption and emission bands for compounds 1m and 2m in
different solvents.
Solvent
Absorption maxima, [nm]
Emission maxima, [nm]
1m
Dichloromethane 376, 414, 437
2m
1m
2m
313, 386, 405
383, 403
450, 475, 490
447, 471, 500
449, 475, 492
447, 471, 501
452, 475, 502
423, 452, 462
428, 450, 460
428, 451, 459
427, 449, 458
430, 452, 467
Acetone
374, 412, 435
376, 414, 437
373, 411, 434
Ethanol
310, 383, 402
309, 382, 402
313, 387, 406
Acetonitrile
Dimethylsulfoxide 379, 416, 438
OLED construction
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To investigate the electron transport properties of the compounds prepared, we explored
the possibility of making films on a glass substrate using the thermal vacuum evaporation
procedure for 1a, 1d, 1e, 1h, 1m, and 2l. In the case of isocoumarins 1a and 1e, we failed to
obtain films of the required quality due to crystallization during deposition or complete/partial
decomposition of substances upon heating. For example, compound 1a displayed an uneven
regime of sublimation at 220–230 °C in a vacuum. The deposition rate varied within a wide
range (0.1–1.0 Å∙s−1), so the layer of the required quality was not prepared. In the case of 1e, the
sublimation temperature was about 90 °C, and the deposition rate was 0.2–0.5 Å∙s−1. The
obtained film turned out to be polycrystalline (matte) and, therefore, is not suitable for electron
transport measurements. Finally, transparent films on glass substrates without visible indication
of crystallization and discoloration were obtained for compounds 1m and 2l upon sublimation at
160 and 144 °C, respectively. Accordingly to thermogravimetric analysis (see the Supporting
Information), compound 1m is stable in the air till 300 °C. Although 1d and 1h gave matte films,
we still managed to obtain the charge carrier mobility values for them. To measure the mobility
of electrons and holes in the studied materials by means of the photo-MIS-CELIV method[24] the
following structures were manufactured: glass/ ITO/ SiO2 (70 nm)/ 1d, 1h, 1m, or 2l (100 nm)/
Al (100 nm) (Fig. 6a). The results are given in Table 6. We found that the mobility values lie in
the range of 10−6−10−5 cm2∙V−1∙s−1, which is significantly lower than for materials usually used
as transport layers (10−4−10−2 cm2∙V−1∙s−1). Therefore, these compounds cannot be applied as
transport materials. Nevertheless, we used isocoumarin 1m as an emissive layer in the OLED of
the following structure (Fig. 6b): ITO/ TAPC (80nm) / 1m (10nm)/ 3TRYMB (30nm)/ LiF
(1nm)/ Al (100nm), where ITO is the anode, TAPC is the hole transporting layer, 3TRYMB is
the electron transport layer, LiF/Al is the cathode. This OLED structure emits yellow-green light
of maximum brightness 1740 cd∙m−2 at 15 V (Fig. 7 and 8). The luminescence spectrum of
isocoumarin 1m in the solid state is represented in the Supporting Information for comparison.
Table 6. The electron and hole mobility, as well as conditions of the film formation for
compounds 1d, 1h, 1m, and 2l.
Compound Electron
mobility,
Hole
Vacuum
deposition
temperature,
oС
Vacuum
deposition Film quality
mobility,
cm2∙V−1∙s−1
cm2∙V−1∙s−1
rate,
Å∙s−1
1.8∙10−5
1.0∙10−5
110
0.1
Matte
1d
5.75∙10−6
1.31∙10−5
2.26∙10−6
5.84∙10−6
1.51∙10−4
7.63∙10−6
120
160
144
0.2
Matte
1h
0.26
0.15
Transparent
Transparent
1m
2l
15
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Figure 6. (a) Manufactured samples for the measurement of the charge carrier mobility by
photo-MIS-CELIV method - glass/ITO/ SiO2(70 nm)/ 1d, 1h, 1m, or 2l (100 nm)/Al (100 nm);
(b) working OLED structure - ITO/ TAPC (80 nm) / 1m (10 nm)/ 3TRYMB (30nm)/ LiF (1nm)/
Al (100 nm) (15В).
(b)
(a)
1
0.5
0
400
500
600
700
800
Wavelength (nm)
Figure 7. (a) Electroluminescence (EL) spectrum, (b) CIE chromaticity diagram (x = 0.363, y =
0.556) of OLED structure with 1m as an emissive layer.
16
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60
40
20
0
2000
1000
0
1
2
0
5
10
15
Voltage (V)
Figure 8. Voltage-current density (1) and voltage-brightness (2) characteristics of OLED with
1m as an emissive layer.
Conclusions
In summary, we have shown that the selectivity of the rhodium-catalyzed oxidative
coupling of aromatic carboxylic acids with internal alkynes strongly depends on the methylation
of the supporting cyclopentadienyl ligand. This step- and atom economic approach provides
access to isocoumarins using [Cp*RhCl2]2 as a catalyst and naphthalene derivatives in the case
of [CpRhI2]n. The method is suitable for polyaromatic carboxylic acids to give -extended
isocoumarins and PAHs. The products show rich optical properties, with fluorescent efficiency
being higher for PAHs. We have demonstrated their applicability as an emissive layer in OLED
manufacturing.
Experimental Section
General: Catalytic reactions were carried out under an argon atmosphere in anhydrous o-xylene.
Isolation of all products was carried out in air. Column chromatography was carried out using
[19]
Macherey-Nagel silica gel 60 (0.04−0.063 mm particle size). Catalysts [Cp*RhCl2]2
and
[18a]
[CpRhI2]n
were prepared as described in the literature. All other reagents were purchased
1
from Acros or Aldrich and used as received. H and 13C{1H} NMR spectra were recorded in
CDCl3 on a Varian Inova 400 spectrometer operating at 400.13 and 100.61 MHz, respectively.
Chemical shifts are reported in ppm using the residual signals of the solvent as internal
17
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standards. Electron impact mass spectra (EIMS) were recorded on a Kratos MS 890 instrument.
Thermogravimetric analysis spectrum for 1m was recorded on a Derivatograph-C instrument.
General procedure for the oxidative coupling of carboxylic acids with internal alkynes
catalyzed by (cyclopentadienyl)rhodium complexes: A mixture of carboxylic acid (0.5 mmol),
alkyne (1.0 mmol), [Cp*RhCl2]2 or [CpRhI2]n (1 mol% Rh), Cu(OAc)2∙2H2O (436 mg, 2.00
mmol) and o-xylene (2 ml) was refluxed with vigorous stirring for 6 h. The precipitate of copper
salts was centrifuged off. The solvent was removed in vacuo and the residue was
chromatographed on a silica column (1 × 15 cm). The first colorless band containing unreacted
alkyne was eluted with petroleum ether. The second colored band was eluted with a mixture of
petroleum ether and dichloromethane or ethyl acetate. Evaporation of the solvent gives a
product, derivative of isocoumarin or naphthalene, respectively, as a colorless or yellow solid (or
oil). Yields are given in Table 1.
3,4-Diphenyl-1H-isochromen-1-one (1a): colorless solid; SiO2, petroleum ether/
1
dichloromethane (2:1); H NMR (CDCl3): δ = 7.20−7.45 (m, 12H), 7.55 (m, 1H), 7.66 (m, 1H),
8.44 (d, 1H, J = 8.0 Hz) ppm (cf.[13a]).
3,4-Bis(4-methoxyphenyl)-1H-isochromen-1-one (1b): yellow solid; SiO2, petroleum ether/
ethyl acetate (10:1); 1H NMR (CDCl3): δ = 3.79 (s, 3H, OMe), 3.89 (s, 3H, OMe), 6.75 (d, 2H, J
= 8.8 Hz), 6.99 (d, 2Н, J = 8.4 Hz), 7.19 (d, 2H, J = 8.4 Hz), 7.22 (d, 1H, J = 7.6 Hz), 7.32 (d, 2H,
13
J = 8.8 Hz), 7.50 (m, 1H), 7.64 (m, 1H), 8.40 (d, 1H, J = 7.8 Hz) ppm; C NMR (CDCl3): δ =
55.22 (OMe), 55.30 (OMe), 113.33 (2C), 114.61 (2C), 115.35, 120.20, 125.17, 125.45, 126.60,
127.66, 129.46, 130.64 (2C), 132.34 (2C), 134.55, 139.49, 150.88, 159.31, 159.87, 162.45 ppm;
MS (EI-MS): calcd. for C23H18O4 [M]+ 358.1, found 358.1.
3,4-Diethyl-1H-isochromen-1-one (1c): orange oil; SiO2, petroleum ether/ ethyl acetate (50:1);
1H NMR (CDCl3): δ = 1.19 (t, 3H, J = 7.7 Hz), 1.27 (t, 3H, J = 7.7 Hz), 2.58−2.67 (m, 4H), 7.44
(t, 1H, J = 8.2 Hz), 7.53 (d, 1H, J = 8.2 Hz), 7.72 (t, 1H, J = 8.2 Hz), 8.30 (d, 1H, J = 8.2 Hz)
ppm; 13C NMR (CDCl3): δ = 12.53 (Et), 14.28 (Et), 19.28 (Et), 24.04 (Et), 113.04, 120.83, 122.43,
127.03, 129.83, 134.56, 137.72, 154.94, 162.96 ppm; MS (EI-MS): calcd. for C13H14O2 [M]+
202.1, found 202.1.
6-Chloro-3,4-diphenyl-1H-isochromen-1-one (1d): colorless solid; SiO2, petroleum ether/
1
dichloromethane (2:1); H NMR (CDCl3): δ = 7.12−7.27 (m, 6H), 7.34 (m, 2H), 7.40−7.54 (m,
4H), 8.34 (d, 1H, J = 8.4 Hz) ppm (cf.[13a]).
6-Methoxy-3,4-diphenyl-1H-isochromen-1-one (1e): colorless solid; SiO2, petroleum ether/
dichloromethane (2:1); 1H NMR (CDCl3): δ = 3.72 (s, 3H, OMe), 6.55 (d, 1H, J = 2.4 Hz), 7.03
(dd, 1H, J = 8.8, 2.4 Hz), 7.10−7.44 (m, 10H), 8.31 (d, 1H, J = 8.8 Hz) ppm (cf.[25]).
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3,4-Diphenyl-1H-benzo[h]isochromen-1-one (1h): colorless solid; SiO2, petroleum ether/
dichloromethane (2:1); 1H NMR (CDCl3): δ = 7.01−7.58 (m, 11H), 7.65 (t, 1H, J = 7.6 Hz), 7.81
(t, 1H, J = 7.6 Hz), 7.89 (d, 1H, J = 8.0 Hz), 8.01 (d, 1H, J = 8.8 Hz), 9.89 (d, 1H, J = 8.4 Hz)
ppm (cf.[25]).
3,4-Diphenylindeno[1,2-h]isochromen-1(11H)-one (1i): colorless solid; SiO2, petroleum ether/
1
dichloromethane (1:1); H NMR (CDCl3): δ = 4.53 (s, 2H, CH2), 7.12−7.60 (m, 13H), 7.71 (d,
1H, J = 6.4 Hz), 7.83 (d, 1H, J = 7.6 Hz), 8.04 (d, 1H, J = 8.4 Hz) ppm; 13C NMR (CDCl3): δ =
39.33 (CH2), 117.27, 117.48, 119.87, 124.80, 125.19, 125.69, 126.85, 127.59, 127.86 (2C),
128.10, 128.79, 129.09 (2C), 129.22 (2C), 131.35 (2C), 133.13, 134.96, 138.00, 139.87, 142.43,
144.43, 146.30, 150.26, 161.60 ppm; MS (EI-MS): calcd. for C28H18O2 [M]+ 386.1, found 386.4;
Anal. Calc. for C28H18O2 (%): C, 87.02; H, 4.69. Found: C, 86.60; H, 4.96.
3,4-Diethylindeno[1,2-h]isochromen-1(11H)-one (1k): yellow solid; SiO2, petroleum ether/
1
ethyl acetate (5:1); H NMR (CDCl3): δ = 1.27 (t, 3H, J = 7.5 Hz), 1.34 (t, 3H, J = 7.5 Hz),
2.65−2.76 (m, 4H), 4.46 (s, 2H, CH2), 7.37−7.46 (m, 2H), 7.63 (d, 1H, J = 8.3 Hz), 7.68 (d, 1H, J
13
= 8.3 Hz), 7.85 (d, 1H, J = 8.3 Hz), 8.16 (d, 1H, J = 8.3 Hz) ppm; C NMR (CDCl3): δ = 12.65
(Et), 14.35 (Et), 19.78 (Et), 24.14 (Et), 39.40 (СH2), 113.47, 119.60, 121.61, 125.10, 125.75,
126.72, 127.25, 136.88, 139.98, 141.34, 144.24, 146.64, 152.96, 154.40, 162.29 ppm; MS (EI-
MS): calcd. for C20H18O2 [M]+ 290.1, found 290.0.
7,8-Diphenyl-10H-phenaleno[1,9-gh]isochromen-10-one (1m): yellow solid; SiO2, petroleum
1
ether/ dichloromethane (1:1); H NMR (CDCl3): δ = 7.40−7.51 (m, 8H), 7.55−7.56 (m, 2H),
7.89−7.91 (m, 2H), 8.04−8.23 (m, 2H), 8.28 (d, 1H, J = 7.6 Hz), 8.40 (d, 1H, J = 7.6 Hz), 8.48
(d, 1H, J = 9.6 Hz), 10.24 (d, 1H, J = 9.6 Hz) ppm; 13C NMR (CDCl3): δ = 111.57, 117.29,
121.45, 123.60, 124.07, 125.87, 126.63, 126.95, 127.20, 127.42, 127.91 (2C), 128.24, 128.92,
129.26 (2C), 129.33 (2C), 130.38, 130.70, 130.97, 131.08, 131.74 (2C), 132.62, 133.12, 135.22,
135.90, 138.08, 150.91, 162.13 ppm; MS (EI-MS): calcd. for C31H18O2 [M]+ 422.1, found 422.0.
7,8-Bis(4-methoxyphenyl)-10H-phenaleno[1,9-gh]isochromen-10-one (1n): yellow solid;
1
SiO2, petroleum ether/ dichloromethane (1:2); H NMR (CDCl3): δ = 3.83 (s, 3H, OMe); 3.96 (s,
3H, OMe), 6.81 (d, 2H, J = 8.9 Hz), 7.10 (d, 2H, J = 8.9 Hz), 7.35 (d, 2H, J = 8.9 Hz), 7.44 (d, 2H,
J = 8.9 Hz), 7.89−7.92 (m, 2H), 8.09−8.17 (m, 2H), 8.27 (d, 1H, J = 7.5 Hz), 8.39 (d, 1H, J = 7.7
Hz), 8.46 (d, 1H, J = 9.5 Hz), 10.23 (d, 1H, J = 9.5 Hz) ppm; 13C NMR (CDCl3): δ = 55.22
(OMe), 55.31 (OMe), 111.33, 113.35 (2C), 114.77 (2C), 115.69, 121.31, 123.62, 123.84, 125.38,
125.59, 125.84, 126.49, 126.81, 127.09, 127.43, 130.30, 130.64, 130.71 (2C), 130.81, 130.94,
132.55, 132.78 (2C), 135.83, 138.75, 150.83, 159.36, 159.83, 162.27 ppm; MS (EI-MS): calcd. for
C33H22O4 [M]+ 482.2, found 482.2.
19
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1,2,3,4-Tetraphenylnaphthalene (2a): yellow oil; SiO2, petroleum ether/ ethyl acetate (10:1);
1H NMR (CDCl3): δ = 6.88−6.94 (m, 10H), 7.25−7.32 (m, 10H), 7.43−7.46 (m, 2H), 7.70−7.72
(m, 2H) ppm (cf.[13a]).
1,2,3,4-Tetrakis(4-methoxyphenyl)naphthalene (2b): brown solid; SiO2, petroleum ether/
diethyl ether (3:1); 1H NMR (CDCl3): δ = 3.64 (s, 6H, OMe), 3.81 (s, 6H, OMe), 6.48 (d, 4H, J =
8.6 Hz), 6.76 (d, 4H, J = 8.6 Hz), 6.83 (d, 4H, J = 8.6 Hz), 7.13 (d, 4H, J = 8.6 Hz), 7.39−7.41
(m, 2H), 7.68−7.72 (m, 2H) ppm (cf.[13a]).
1,2,3,4-Tetraethylnaphthalene (2c): yellow oil; SiO2, petroleum ether/ ethyl acetate (100:1); 1H
NMR (CDCl3): δ = 1.34 (t, 3H, J = 7.5 Hz), 1.40 (t, 3H, J = 7.5 Hz), 2.93 (q, 2H, J = 7.5 Hz),
3.19 (q, 2H, J = 7.6 Hz), 7.47−7.51 (m, 2H); 8.09−8.13 (m, 2H) ppm (cf.[26]).
6-Chloro-1,2,3,4-tetraphenylnaphthalene (2d): yellow solid; SiO2, petroleum ether/
dichloromethane (6:1); 1H NMR (CDCl3): δ = 6.88−6.91 (m, 10H), 7.22−7.28 (m, 10H), 7.57 (d,
1H, J = 8.0 Hz), 7.65 (d, 1H, J = 8.0 Hz), 7.68 (s, 1H) ppm (cf.[13a]).
6-Methoxy-1,2,3,4-tetraphenylnaphthalene (2e): yellow solid; SiO2, petroleum ether/
dichloromethane (10:1); 1H NMR (CDCl3): δ = 3.75 (s, 3H, OMe), 6.90−6.95 (m, 10H), 7.05 (s,
1H), 7.15 (d, 1H, J = 9.1 Hz), 7.29−7.34 (m, 10H), 7.67 (d, 1H, J = 9.1 Hz) ppm (cf.[27]).
6-Methoxy-1,4-dimethyl-2,3-diphenylnaphthalene (2f): yellow solid; SiO2, petroleum ether/
1
dichloromethane (3:1); H NMR (CDCl3): δ = 2.43 (s, 3H, Me), 2.45 (s, 3H, Me), 4.02 (s, 3H,
OMe), 6.99−7.02 (m, 6H), 7.15−7.17 (m, 4H), 7.30 (dd, 1H, J = 9.2, 2.7 Hz), 7.43 (d, 1H, J = 2.7
Hz), 8.11 (d, 1H, J = 9.2 Hz) ppm; 13C NMR (CDCl3): δ = 16.96 (Me), 17.10 (Me), 55.39 (OMe),
104.02, 117.70, 125.81, 125.87, 126.82, 127.28 (2C), 127.29 (2C), 129.43, 129.47, 129.72, 130.45
(2C), 130.68 (2C), 133.36, 137.42, 140.07, 141.86, 142.00, 157.72 ppm; MS (EI-MS): calcd. for
C25H22O [M]+ 338.2, found 338.2.
1
6-Nitro-1,2,3,4-tetraphenylnaphthalene (2g): yellow solid; SiO2, dichloromethane; H NMR
(CDCl3): δ = 6.90−6.94 (m, 10H), 7.24−7.35 (m, 10H), 7.84 (d, 1H, J = 9.4 Hz), 8.17 (dd, 1H, J
= 9.4, 2.4 Hz), 8.69 (d, 1H, J = 2.4 Hz) ppm (cf.[27]).
1,2,3,4-Tetraphenyl-11H-benzo[a]fluorene (2i): yellow solid; SiO2, dichloromethane; 1H NMR
(CDCl3): δ = 3.28 (s, 2H, CH2), 6.84−6.90 (m, 10H), 7.22−7.38 (m, 13H), 7.78 (d, 1H, J = 8.7
Hz), 7.81 (d, 1H, J = 7.5 Hz), 7.90 (d, 1H, J = 8.7 Hz) ppm; 13C NMR (CDCl3): δ = 39.31 (CH2),
118.72, 119.30, 124.18, 125.20, 125.23, 126.22, 126.32 (2C), 126.39, 126.49 (2C), 126.55, 126.85,
127.52 (2C), 127.61 (2C), 127.71, 127.88, 131.22 (2C), 131.27 (2C), 131.36 (2C), 131.40 (2C),
132.16, 137.48, 138.23, 139.47, 139.98, 140.25, 140.38, 140.43, 140.56, 140.59, 141.11, 141.86,
144.24 ppm; MS (EI-MS): calcd. for C41H28 [M]+ 520.2, found 519.9.
1,4-Dimethyl-2,3-diphenyl-11H-benzo[a]fluorene (2j): yellow solid; SiO2, petroleum ether/
ethyl acetate (8:1); 1H NMR (CDCl3): δ = 2.56 (s, 3H, Me), 2.74 (s, 3H, Me), 4.59 (s, 2H, CH2),
20
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7.05−7.09 (m, 4H), 7.16−7.24 (m, 6H), 7.43 (t, 1H, J = 7.4), 7.53 (t, 1H, J = 7.4 Hz), 7.71 (d,
1H, J = 7.4 Hz), 7.98 (d, 1H, J = 7.4 Hz), 8.11 (d, 1H, J = 8.7 Hz), 8.29 (d, 1H, J = 8.7 Hz) ppm;
13C NMR (CDCl3): δ = 17.96 (Me), 21.15 (Me), 41.98 (CH2), 118.71, 119.45, 124.29, 125.26,
125.82, 125.87, 126.26, 126.71, 127.25 (2C), 127.40 (2C), 130.13, 130.29, 130.43 (2C), 130.46
(2C), 131.21, 132.60, 139.00, 139.93, 139.95, 140.88, 141.41, 141.97, 142.18, 143.81 ppm; MS
(EI-MS): calcd. for C31H24 [M]+ 396.2, found 396.5.
1,2,3,4-Tetraphenylbenzo[b]naphtho[2,1-d]furan (2l): colorless solid; SiO2, petroleum ether/
1
dichloromethane (2:1); H NMR (CDCl3): δ = 6.79−7.01 (m, 10H), 7.06−7.18 (m, 1H),
7.19−7.44 (m, 12H), 7.60−7.69 (m, 1H), 7.91−8.02 (m, 2H) ppm; 13C NMR (CDCl3): δ = 111.67,
118.55, 120.00, 120.32, 120.54, 122.59, 122.90, 124.06, 125.40 (2C), 126.00, 126.22, 126.49
(2C), 126.56, 126.59 (2C), 126.90 (2C), 127.61 (2C), 130.98 (2C), 131.29 (2C), 131.25 (2C),
131.40 (2C), 132.12, 135.42, 139.03, 139.26, 140.05, 140.08, 140.34, 140.50, 141.21, 152.43,
155.52 ppm; MS (EI-MS): calcd. for C40H26O [M]+ 522.2, found 522.3.
1
7,8,9,10-Tetraphenylbenzo[pqr]tetraphene (2m): yellow solid; SiO2, dichloromethane; H
NMR (CDCl3): δ = 6.85−6.94 (m, 10H), 7.22−7.27 (m, 6H), 7.34−7.35 (m, 4H), 7.70 (d, 1H, J =
9.5 Hz,), 7.84 (m, 2H), 7.90−8.00 (m, 2H), 8.05 (m, 2H), 8.30 (s, 1H) ppm; 13C NMR (CDCl3): δ
= 124.49, 124.53, 124.84, 124.99, 125.15, 125.19, 125.36, 126.17, 126.38, 126.50 (2C), 126.59
(2C), 126.63, 126.91, 127.65, 127.69 (2C), 127.75, 128.19, 128.31 (2C), 128.49, 129.84, 130.68,
131.08, 131.22 (2C), 131.47 (2C), 131.59 (2C), 131.74 (2C), 137.88, 138.92, 139.14, 140.24,
140.27, 140.73, 140.87, 143.66 ppm; MS (EI-MS): calcd. for C44H28 [M]+ 556.2, found 556.9;
Anal. Calc. for C44H28∙CH2Cl2 (%): C, 84.23; H, 4.72. Found: C, 84.06; H, 4.86.
7,10-Dimethyl-8,9-diphenylbenzo[pqr]tetraphene (2o): yellow solid; SiO2, petroleum ether/
dichloromethane (6:1); 1H NMR (CDCl3): δ = 2.79 (s, 3H, Me), 2.96 (s, 3H, Me), 7.12−7.24 (m,
10H), 7.96−8.04 (m, 2H); 8.08−8.13 (m, 2H), 8.26 (d, 2H, J = 8.9 Hz), 8.81 (s, 1H), 9.17 (d, 1H,
J = 9.4 Hz) ppm; 13C NMR (CDCl3): δ = 17.91(Me), 25.46 (Me), 121.99, 124.61, 124.76, 125.12,
125.15, 125.95, 126.04, 126.08, 127.26 (2C), 127.56 (2C), 127.64, 127.67, 128.26, 128.47, 128.57,
128.93, 129.56 (2C), 129.64, 129.67, 130.25, 130.66 (2C), 130.68 (2C), 130.79, 130.82, 131.81,
139.34, 141.64, 141.92, 142.35 ppm; MS (EI-MS): calcd. for C34H24 [M]+ 432.2, found 432.2.
7,8,9,10-Tetraethylbenzo[pqr]tetraphene (2p): brown solid; SiO2, petroleum ether/ ethyl
acetate (5:1); 1H NMR (CDCl3): δ = 1.38 (m, 6H), 1.56 (td, 3H, J = 7.6, 2.7 Hz), 1.80 (td, 3H, J
= 7.3, 2.5 Hz), 3.10 (qd, 2H, J = 7.5, 2.7 Hz), 3.19 (qd, 2H, J = 7.4, 2.3 Hz), 3.44 (qd, 2H, J =
7.6, 2.5 Hz), 3.59 (bs, 2H), 7.89 (dd, 1H, J = 9.1, 1.8 Hz), 7.95−8.07 (m, 3H), 8.21 (dd, 2H, J =
9.4, 2.1 Hz), 8.73 (d, 1H, J = 2.4 Hz), 9.08 (dd, 1H, J = 9.4, 2.4 Hz) ppm; 13C NMR (CDCl3): δ =
16.08, 16.12, 16.20, 16.74, 22.66, 22.92, 23.01, 25.98, 121.79, 124.25, 124.29, 124.77, 124.82,
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125.39, 125.83, 127.09, 127.21, 127.65, 128.57, 128.65, 128.68, 129.70, 130.80, 131.95, 135.79,
136.02, 138.28, 140.72 ppm; MS (EI-MS): calcd. for C28H28 [M]+ 364.2, found 364.0.
General procedure for the oxidative coupling of carboxylic acids with internal alkynes
catalyzed by mixture Cp*H/RhCl3: A mixture of carboxylic acid (0.5 mmol), alkyne (1.1
mmol), Cp*H (10 µl, 0.06 mmol), RhCl3 (2.1 mg, 0.01 mmol), Cu(OAc)2∙2H2O (436 mg, 2.00
mmol) and o-xylene (2 ml) was refluxed with vigorous stirring for 6 h. Isolation and purification
of products were carried out as described above.
Absorption and fluorescence spectroscopy: Absorption spectra were recorded on an Agilent
Cary 300 double-beam UV-vis spectrophotometer in a standard 1 cm quartz cell (Helma QS with
PTFE stopper). Fluorescence spectra were recorded on a FluoroLog-3-221 spectrofluorimeter at
20±1°C in a standard 1cm quartz cell. The observed fluorescence was detected at a direct angle
relative to the excitation beam. The fluorescence spectra were corrected for the nonuniformity of
detector spectral sensitivity and were normalized by the excitation light intensity, derived from
calibrated built-in reference sensor values.
The fluorescence quantum yield of the sample was determined at 20±1 °C in CH3CN
solutions compared to quinine sulfate in 0.5M H2SO4 water solution as a standard
(φ=0.55±0.03).[28] The quantum yield was calculated from the equation:[29]
Si 0 (110D ) ni
S0
2
0.
i 


(110D
)
n02
i
where φi and φ0 are the quantum yields of the test solution and the standard; Di and D0 are the
absorptions of the test solution and the standard, Si and S0 are the areas underneath corrected
fluorescence spectrum curves for the test solution and the standard, ni and n0 are the refraction
factors of the solvents of the test compound and the standard compound, respectively.
The luminescence quantum yield measurement for 1m in the solid state was performed
using of a HORIBA Jobin Yvon integration sphere (Model F-3018) at 298 K. All data were
collected and processed using the Microsoft Excel software package (PLQY calculator v. 1.2.).
The fluorescence lifetime measurement for 1m in acetonitrile solution was carried out
using the time-correlated single-photon counting method realized on Fluorolog-3-221
spectrofluorimeter equipped with 340 nm NanoLED laser-diode source for fluorescence
excitation. To fit fluorescence decay data and to determine fluorescence lifetime DataStation
software (DAS6) was used.
The fluorescence spectra were normalized by the excitation light intensity, derived from
the calibrated built-in reference sensor values. This normalization by the excitation light intensity
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10.1002/cplu.202000048
ChemPlusChem
(as shown by the results of our tests) makes the integral intensity invariant to the changing the
excitation slit width in the range from two to four times. If the slit width is varied more than four
times, a negligible difference occurs between spectra intensity, so we limit slit width change by
four times. The best effect of this normalization (when the normalized intensity does not depend
on the slit change) occurs when the excitation wavelength corresponds to a flat area of the
absorption spectra with a minimal optical density change upon wavelength (but not at an abrupt
slope). This technique makes possible to measure the quantum yields of low-fluorescent probes
by means of high-fluorescent standards with the excitation slit variation.
Spectroscopic grade acetonitrile (HPLC-S, Biosolve, #01200702) and CH2Cl2 (HPLC-
grade, TU 6-09-2662-77) were used without further purification for solution preparation and
recording of the absorption and fluorescence spectra. The concentrated solutions (MeCN and
CH2Cl2) were prepared and stored in glass vials sealed with PTFE-shielded septa caps.
Solutions preparation: We encountered some experimental difficulties while
investigating the optical properties since the compounds studied have limited solubility in
CH3CN, but have good solubility in CH2Cl2. CH3CN as a solvent is convenient for the
experiment: it is optically transparent over a wide UV-VIS range and its boiling point is not very
low (this is essential for dosing units, that are used for dilution). CH2Cl2 has limited transparency
in the UV range, so some bands of substances will be cropped by the solvent absorption. We
decide to measure the absorption and emission spectra by diluting highly concentrated CH2Cl2
solutions (3·10–3M) with CH3CN. Because of the low CH2Cl2 concentration we were not able to
subtract its absorption from the UV spectrum with good accuracy. For compounds 1 m and 2 m,
we demonstrated that the addition of CH2Cl2 to a CH3CN solution does not affect the absorption
and fluorescence spectra (for details, see the Supporting Information).
OLED manufacturing: The CELIV set-up included a digital USB-oscilloscope (DL-Analog
Discovery, Digilent Co.), which played the role of a master pulse generator and a transient
current pulse monitor. RC constants were at least a factor of 20 smaller than the time scales of
interest. The bias was swept in the range between 10 and 100 kHz. The electroluminescence
spectra of OLEDs were recorded on an Avantes 2048 fiber-optic spectrofluorimeter (spectral
range 200–1100 nm, spectral resolution better than 0.04 nm). Voltage–current and voltage–
brightness characteristics were measured with a Keithley 2601 SourceMeter, a Keithley 485
picoammeter and a TKA-04/3 luxmeter–brightness meter. The preparation of OLED samples
and measurements of their spectral and optoelectronic characteristics were performed at room
temperature under argon atmosphere with a controlled content of oxygen and water (below 1
ppm). The thickness of the films was determined using a LOMO MII-4 interferometer.
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10.1002/cplu.202000048
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Supporting Information (see footnote on the first page of this article): Crystallographic data
and copies of NMR, absorption and fluorescence spectra.
Acknowledgements: This work was supported by the Russian Science Foundation (Grant No.
17-73-30036). The X-ray diffraction studies were performed with the financial support from the
Ministry of Science and Higher Education of the Russian Federation using the equipment of
Center for molecular composition studies of INEOS RAS. A.F.S. and E.I.K. thank the RUDN
University Program “5-100” for support. The authors are very grateful to Dr. Mikhail I. Buzin
for thermogravimetric measurements.
Keywords: C-H activation; fluorescence; organic light-emitting diode; polycycles; rhodium
catalysis
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10.1002/cplu.202000048
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Table of Contents entry
A short text
From catalysis to OLEDs: The selectivity of the rhodium-catalyzed oxidative coupling of
carboxylic acids and internal alkynes strongly depends on the methylation of the Cp ligand at the
rhodium atom. This approach provides easy access to isocoumarins and PAHs with extended
π‐conjugation for their further application as fluorescent materials. In particular, they exhibit
fluorescence emission in the blue-green region (400–550 nm). Based on 7,8-diphenyl-10H-
phenaleno[1,9-gh]isochromen-10-one as an emissive layer, the OLED structure was
manufactured.
Graphical Element
References
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