Thiophene-forming one-pot synthesis of three thienyl-bridged oligophenothiazines and their electronic properties

Article abstract of DOI:10.3762/bjoc.12.194

The pseudo five-component Sonogashira-Glaser cyclization synthesis of symmetrically 2,5-diaryl-substituted thiophenes is excellently suited to access thienyl-bridged oligophenothiazines in a one-pot fashion. Three thienyl-bridged systems were intensively studied by UV-vis and fluorescence spectroscopy as well as by cyclic voltammetry. The oxidation proceeds with lower oxidation potentials and consistently reversible oxidations can be identified. The Stokes shifts are large and substantial fluorescence quantum yields can be measured. Computational chemistry indicates lowest energy conformers with sigmoidal and helical structure, similar to oligophenothiazines. TD-DFT and even semiempirical ZINDO calculations reproduce the trends of longest wavelengths absorption bands and allow the assignment of these transitions to possess largely charge-transfer character from the adjacent phenothiazinyl moieties to the central thienyl unit.

Full text of DOI:10.3762/bjoc.12.194

Thiophene-forming one-pot synthesis of three thienyl-bridged
oligophenothiazines and their electronic properties
Dominik Urselmann, Konstantin Deilhof, Bernhard Mayer and Thomas J. J. Müller*
Full Research Paper
Open Access
Address:
Beilstein J. Org. Chem. 2016, 12, 2055–2064.
Institut für Organische Chemie und Makromolekulare Chemie,
Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, D-40225
Düsseldorf, Germany
doi:10.3762/bjoc.12.194
Received: 13 May 2016
Accepted: 11 August 2016
Published: 20 September 2016
Email:
Thomas J. J. Müller* - ThomasJJ.Mueller@uni-duesseldorf.de
This article is part of the Thematic Series "Organometallic chemistry".
Guest Editor: B. F. Straub
* Corresponding author
Keywords:
C–C coupling; copper; cyclic voltammetry; DFT; microwave-assisted
synthesis; multicomponent reactions; palladium; phenothiazines;
thiophenes
© 2016 Urselmann et al.; licensee Beilstein-Institut.
License and terms: see end of document.
Abstract
The pseudo five-component Sonogashira–Glaser cyclization synthesis of symmetrically 2,5-diaryl-substituted thiophenes is excel-
lently suited to access thienyl-bridged oligophenothiazines in a one-pot fashion. Three thienyl-bridged systems were intensively
studied by UV–vis and fluorescence spectroscopy as well as by cyclic voltammetry. The oxidation proceeds with lower oxidation
potentials and consistently reversible oxidations can be identified. The Stokes shifts are large and substantial fluorescence quantum
yields can be measured. Computational chemistry indicates lowest energy conformers with sigmoidal and helical structure, similar
to oligophenothiazines. TD-DFT and even semiempirical ZINDO calculations reproduce the trends of longest wavelengths absorp-
tion bands and allow the assignment of these transitions to possess largely charge-transfer character from the adjacent phenothia-
zinyl moieties to the central thienyl unit.
Introduction
Oligothiophenes [1-8] have adopted a dominating role among di(hetero)aryl-substituted thiophenes are additionally interest-
functional π-electron systems [9]. In particular, they have ing as redox switchable molecular wires [35,36] in unimolecu-
received attention as hole-transport materials in organic light lar electronics [37-40].
emitting diodes [10-15], organic field-effect transistors [16-22],
and organic photovoltaics [23-26]. Likewise their smaller In comparison to thiophene, phenothiazine, a tricyclic dibenzo-
congeners, 2,5-di(hetero)aryl substituted thiophenes [4,5], are 1,4-thiazine, possesses a significantly lower oxidation potential,
equally relevant as charge-carrying materials [2,3,27,28] and similar to aniline. However, phenothiazine derivatives form
organic semiconductors [29,30] in electronic [31] and optoelec- stable deeply colored radical cations with perfect Nernstian re-
tronic devices [32-34]. As reversibly oxidizable units 2,5- versibility [41-44]. Over the past one and a half decades the
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synthetic and physical organic chemistry of oligophenothia- di(hetero)arylfurans [77] could open a highly convergent thio-
zines have been intensively studied in linear [45] and cyclic phene forming approach to the proposed title compounds. Here,
[46] topologies, as diphenothiazinyl dumbbells brigded by we report the pseudo five-component synthesis of three thienyl-
heterocycles [47-49], and as acceptor [50,51], ferrocenyl [52], bridged oligophenothiazines by a one-pot Sonogashira–Glaser
and alkynyl [53-55] substituted (oligo)phenothiazines. Their cyclization sequence and the electronic characterization by elec-
pronounced reversible oxidation potentials, their electro- and tronic spectroscopy, cyclic voltammetry, and quantum chemi-
photochromicity [56], and their luminescence [57,58] have cal computations.
rendered (oligo)phenothiazines interesting candidates as donors
Results and Discussion
in donor–acceptor conjugates with photo-induced electron-
Synthesis of thienyl-bridged
oligophenothiazines
transfer characteristics [59-63], as hole-transport materials [64],
for applications in mesoporous organo silica hybrid materials
[65], and as chromophores in dye-sensitized solar cells [66-68].
Furthermore, (oligo)phenothiazines in their native reduced
forms display a pronounced ability to form self-assembled
monolayers on gold [69-71] as well as on zinc and iron oxide
surfaces [72].
Although the thienyl bridge can be introduced by Suzuki cou-
pling as previously reported [48], we decided to transpose a
methodology initiated by a Sonogashira–Glaser sequence [74]
also for probing delicate oxidative dimerization conditions with
easily oxidizable phenothiazinyl moieties. According to our
recent study on the formation of butadiynyl-bridged dipheno-
thiazines [54] we were optimistic to probe this unusual ap-
proach. First, three different bromo-substituted (oligo)pheno-
thiazine substrates 1 had to be prepared. 3-Bromo-10-hexyl-
10H-phenothiazine (1a) was synthesized according to the litera-
ture by hexylation of 3-bromo-10H-phenothiazine [45]. The
7-bromo-substituted phenothiazines 1b and 1c were prepared in
good yields according to our one-pot bromine-lithium-
exchange-borylation-Suzuki (BLEBS) sequence [78], employ-
ing an excess of 3,7-dibromo-10-hexyl-10H-phenothiazine (3)
[45] as a coupling component in the Suzuki step (Scheme 1).
Conceptually, thienyl-bridged oligophenothiazines can be
considered as a novel type of structurally well-defined electron-
rich oligophenothiazine–thiophene hybrids (Figure 1). Thereby,
the strong intramolecular electronic coupling of (oligo)pheno-
thiazines [45,64] and the low torsional displacement from a
coplanar arrangement of both redox moieties of the dumbbells
might represent conjugatively linked nanometer-scaled novel
multistep redox active oligomers.
With three bromo-substituted (oligo)phenothiazines 1 in hand
the consecutive pseudo five-component Sonogashira–Glaser
cyclization synthesis [75] was successfully performed furnish-
ing three symmetrical thienyl-bridged oligophenothiazine
dumbbells 3 as yellow greenish resins in yields of 34–54%
(Scheme 2). The molecular composition of the thienyl-bridged
oligophenothiazines 3 is unambiguously supported by mass
spectrometry (MALDI–TOF). The proton and carbon NMR
spectra unambiguously support the formation of the oligomers
3, and expectedly, in agreement with the molecular symmetry,
the appearance of one (3a), two (3b), and three (3c) distinct
resonances for the nitrogen-bound methylene carbon nuclei in
the 13C NMR spectra additionally supported the assigned struc-
tures. Combustion analyses of compounds 3b and 3c indicate
that water and THF (compound 3b) and water (compound 3c)
are present as solvent inclusion in the resins that cannot be re-
moved even upon extensive drying under vacuo. However,
Figure 1: Thienyl-bridged oligophenothiazines as topological hybrids
of (oligo)phenothiazines and 2,5-di(hetero)aryl substituted thiophene.
As part of our concept to develop novel multicomponent strate- HPLC traces with UV detection support that the materials
gies for the synthesis of functional π-electron systems [73], we consist of single specimen with over 99% purity. Taking into
reasoned that our recently reported one-pot consecutive Sono- account that five new bonds are being formed in this consecu-
gashira–Glaser sequence [74] and the resulting application to tive pseudo five-component process the yield per bond forming
pseudo five-component syntheses of 2,5-di(hetero)arylthio- step counts for 81–88%, albeit a Pd/Cu mediated air oxidation
phenes [75,76] as well as intensively blue luminescent 2,5- step is involved.
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Scheme 1: One-pot bromine-lithium-exchange-borylation-Suzuki (BLEBS) synthesis of 7-bromo-substituted phenothiazines 1b and 1c with 3,7-
dibromo-10-hexyl-10H-phenothiazine (2).
Scheme 2: Pseudo five-component Sonogashira-Glaser-cyclization synthesis of thienyl-bridged oligophenothiazine dumbbells 3.
Electronic spectra and oxidation potentials
the title compounds 3 in comparison to the model 10-hexyl-
The electronic properties of the three thienyl-bridged oligo- 10H-phenothiazine with E00/+1 = 730 mV was measured. All
phenothiazines 3 were experimentally investigated by absorp- three thienyl-bridged oligophenothiazines 3 display cathodi-
tion and emission spectroscopy and by cyclic voltammetry cally shifted first oxidations in comparison to the model, how-
(Table 1).
ever, with significantly more complex cyclovoltammetric signa-
tures (Figure 2). The simplest representative, 2,5-bis(phenothia-
Cyclic voltammetry discloses the oxidation potential as an elec- zinyl)thiophene 3a, possesses two reversible oxidation waves at
tronic ground state property. Therefore, the ease of oxidation of E1/2 = 650 and 760 mV with Nernstian behavior (Figure 2, top),
Table 1: UV–vis and emission data and oxidation potentials of thienyl-bridged oligophenothiazines 3 (recorded in CH2Cl2, T = 298 K; bold values:
absorption and emission maxima used for determining the Stokes shift).
compound
absorption λmax,abs (ε) [nm]
emission λmax,em [nm] (Φf) [%]a
E1/2 [mV]
Stokes shiftb Δ [cm−1]
246 (39600), 261 (39100),
318 (27000), 395 (33100)
3a
3b
3c
506 (18)
502 (16)
521 (15)
444 (–)
5600
4800
7200
9600
650, 760
266 (52100), 284 (45900),
319 (32500), 404 (27700)
620–1010,c
1320–1520c,d
267 (103000), 283 (116200),
327 (61000), 379 (51900)
550–950e
730
10-hexyl-10H-
phenothiazine
258, 312
aRecorded in CH2Cl2 at c(3) = 10−7 M with coumarin 151 in ethanol/water 1:1 (w/w) as a standard (Φf = 0.88). bΔ = 1/λmax,abs − 1/λmax,em [cm−1];
the UV–vis and emission data in bold face were applied for calculating the corresponding Stokes shifts. cOxidation and reduction half-waves are not
resolved but superimpose. dShoulder. ePosition of the oxidation half-wave without distinct reduction half-wave.
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Figure 2: Cyclic voltammograms of compounds 3 (recorded in CH2Cl2, T = 293 K, electrolyte n-Bu4N+PF6−, Pt working electrode, Pt counter elec-
trode, Ag/AgCl reference electrode, v = 50 mV/s (3a and 3b), v = 100 mV/s (3c, multisweep experiment, 1. cycle (black), 2. cycle (red), 3. cycle
(blue)).
indicating that the thiophene bridge enables electronic commu- reversal voltage thienyl-bridged oligophenothiazines 3 can be
nication between both electrophore moieties. The first oxida- reversible charged and discharged, a property that is highly
tion potential of 2,5-bis(diphenothiazinyl)thiophene 3b desired for molecular electronics applications.
is cathodically shifted and appears at a peak potential of
E1/2 = 620 mV, however, without displaying Nernstian behav- The absorption spectra undoubtedly follow the Lambert–Beer
ior (Figure 2, center). Two further oxidation waves can be law in a broad concentration range (as studied for compounds
detected; yet, the corresponding reduction half-waves are 3b and 3c, see Supporting Information File 1, Figures S3 and
absent. Only an increased reduction half wave indicates the S4). In addition this behavior underlines that no aggregation of
presence of multiply oxidized specimens that are reduced at the the molecules has to be taken into account at the concentration
same potential as a consequence of electrode deposition. For the level of absorption and emission spectroscopy. In the UV–vis
2,5-bis(triphenothiazinyl)thiophene 3c no distinct reversible ox- spectra, most characteristically, four absorption bands are
idation waves can be identified but rather a continuous oxida- found, three at shorter wavelengths arising from the phenothia-
tion window ranging from 500 to 1000 mV (Figure 2, bottom). zinyl moieties and the longest wavelength maximum can be
Yet, the multisweep experiment indicates that within this assigned to the central 2,5-di(hetero)aryl-substituted thiophene
window oxidation and reduction occurs in a reversible fashion. part (Figure 3). This assignment is based on the molar decadic
extinction coefficients that increase with the number of pheno-
However, the cyclic voltammograms of this system containing thiazinyl units (Table 1). However, the increasing number of
six phenothiazines conjugatively linked via a symmetrically phenothiazinyl moieties enhances the donor character of the
substituted thiophene bridge do not obey a strictly Nernstian be- substituents on the thiophene core. In turn the thienyl moiety
havior. Thereby, a first oxidation potential of E1/2 = 550 mV behaves as an acceptor due to its higher oxidation potential.
was estimated. Interestingly, by carefully selecting the applied Interestingly, the redshift of the longest wavelength absorption
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Figure 3: UV–vis (solid lines) and fluorescence spectra (dashed lines) of the thienyl-bridged oligophenothiazines 3 (recorded in CH2Cl2, T = 298 K).
band is relatively moderate, presumably as a consequence of molecules adopt sigmoidal and helical minimum conformers
only a modest delocalization of the complete π-electron systems (Figure 4) as already shown for consanguineous series of higher
in the electronic ground state.
oligophenothiazines [45].
In the emission spectra broad shortest wavelength bands appear With these geometry-optimized structures in hand the elec-
in a region from 502 to 521 nm with large Stokes shifts Δ be- tronic absorptions were calculated with the semiempirical
tween 4800 and 7200 nm (Figure 2), which are typical for ZINDO-CI, and TD-DFT (B3LYP and CAM-B3LYP, an imple-
oligophenothiazines [45]. However, the lack of a systematic mented hybrid exchange-correlation functional [81], using the
trend with the numbers of phenothiazinyl units indicates that the polarizable continuum model (PCM) [82] applying dichloro-
excited state property is strongly affected by local conforma- methane as solvent) methods and the results were compared
tional biases arising from the planarization of electronic ground with the experimentally obtained UV–vis absorption spectra
state butterfly conformation of phenothiazines in the excited (see Supporting Information File 1, Table S2) and the calcu-
state [57,79]. Also the fluorescence quantum yields Φf with 15 lated energies of the FMOs (frontier molecular orbitals) (see
to 18% essentially remain constant within this series, although, Supporting Information File 1, Table S3).
the increasing number of sulfur-containing heterocycles sug-
gests an increase in fluorescence deactivating spin–orbit cou- Although a perfect numerical match of experimentally and
pling. In comparison to the consanguineous oligophenothia- computationally determined absorption bands cannot be ex-
zines [45] the compounds 3 display considerable lower fluores- pected for conformationally flexible complex molecules with
cence quantum yields.
extended π-conjugation, the trend of the longest wavelength
absorption bands from the UV–vis spectra is correctly repro-
duced. Furthermore, for all three methods and for all three
Computations and electronic structure
The electronic properties of the three thienyl-bridged oligo- structures this longest wavelength absorption can be assigned to
phenothiazines 3 were further investigated by computational S1 states that predominantly consist of HOMO to LUMO transi-
studies on the DFT level of theory. First the ground state tions with dominant oscillator strengths. For the thienyl-bridged
geometries of structures 3a, 3b, and 3c (the n-hexyl substitu- 2,5-bis(terphenothiazinyl)thiophene 3c, containing the symmet-
ents were truncated to ethyl groups for reducing the computa- rical conjugative ligation of two terphenothiazinyl moieties to
tional time) were optimized by DFT calculations with the the thienyl bridge, in the TD-DFT methods significant contribu-
B3LYP functional and the 6-311G(d,p) basis set as imple- tions of HOMO-2 to LUMO transitions contribute to the corre-
mented in the program package Gaussian 09 [80]. In addition sponding S1 states. The inspection of the Kohn–Sham FMOs,
the minima structures were confirmed by the absence of imagi- contributing to the S1 states and representing the longest wave-
nary vibrations in the analytical frequency analyses. The inspec- length absorption bands, indicates that the nature of these transi-
tion of the computed molecular structures 3 indicates that these tions possesses predominantly a charge-transfer character from
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Figure 4: DFT-calculated minimum conformer of the 2,5-bis(terphenothiazinyl)thiophene 3c (calculated with the B3LYP functional and the
6-311G(d,p) basis set).
the adjacent phenothiazinyl moieties to the central thiophene donor–acceptor–donor systems, a topology that can be favor-
part. The intense coefficient density in the center of the struc- ably developed further in molecular electronics.
tures in both HOMO (HOMO-2) and LUMO additionally
supports and rationalizes the dominant magnitude of the oscil- Conclusion
lator strengths f, corresponding with significant decadic molar In summary, we could show that the pseudo five-component
extinction coefficients of the associated bands (Figure 5). In Sonogashira–Glaser cyclization synthesis of symmetrically 2,5-
principle these phenothiazine conjugates can be considered as diaryl-substituted thiophenes can be efficiently transposed to
Figure 5: Relevant Kohn–Sham FMOs contributing to the S1 states that are assigned to the longest wavelengths absorption bands of thienyl-bridged
oligophenothiazines 3 (calculated with the B3LYP functional in vacuo and the 6-311G(d,p) basis set).
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access thienyl-bridged oligophenothiazines in a one-pot fashion 8H), 1.39–1.51 (m, 4H), 1.78 (quint, 3J = 7.5 Hz, 4H), 3.92 (t,
starting from 3-bromo(oligo)phenothiazines. Most remarkably, 3J = 7.0 Hz, 4H), 6.90–6.97 (m, 2H), 6.97–7.03 (m, 4H), 7.14
the oxidative conditions of the central Glaser step employing air (dd, 3J = 7.7 Hz, 4J = 1.5 Hz, 2H), 7.16–7.23 (m, 2H), 7.29 (s,
as oxidant does not interfere with the oxidation sensitive 2H), 7.41 (d, 4J = 2.1 Hz, 2H), 7.44 (dd, 3J = 8.4 Hz, 4J = 2.2
(oligo)phenothiazinyl moieties. The electronic properties of the Hz, 2H); 13C NMR (75 MHz, acetone-d6) δ 14.3 (2CH3), 23.3
obtained three thienyl-bridged systems were intensively studied (2CH2), 27.1 (2CH2), 27.5 (2CH2), 32.2 (2CH2), 47.9 (2CH2),
by UV–vis and fluorescence spectroscopy as well as by cyclic 116.7 (2CH), 116.8 (2CH), 123.4 (2CH), 124.5 (2CH), 124.5
voltammetry. With increasing numbers of phenothiazinyl elec- (2CH), 124.8 (2Cquat), 125.4 (2CH), 126.1 (2Cquat), 128.1
trophore units the oxidation proceeds with lower oxidation (2CH), 128.4 (2CH), 129.6 (2Cquat), 142.5 (2Cquat), 145.5
potentials and for the 2,5-bis(terphenothiazinyl)thiophene even (2Cquat), 145.8 (2Cquat); MS (MALDI) m/z: 646.3 ([M]+);
a consistently reversible oxidation area can be found. As UV–vis (CH2Cl2), λmax [nm] (ε): 246 (39600), 261 (39100),
already shown for oligophenothiazines and typical for many 318 (27000), 395 (33100); IR (KBr) [cm−1]: 3057 (w), 2951
3-(hetero)arylphenothiazines the Stokes shifts are large and sub- (w), 2926 (w), 2851 (w), 1917 (w), 1597 (w), 1576 (w), 1539
stantial fluorescence quantum yields can be measured. Compu- (w), 1489 (w), 1458 (s), 1398 (w), 1362 (w), 1331 (m), 1285
tational chemistry supports lowest-energy conformers with (w), 1248 (m), 1238 (m), 1225 (w), 1192 (w), 1161 (w), 1134
sigmoidal and helical structure, similar to oligophenothiazines. (w), 1103 (w), 1038 (w), 1022 (w), 968 (w), 926 (w), 908 (w),
Furthermore, TD-DFT and even semiempirical ZINDO calcula- 874 (w), 793 (s), 745 (s), 704 (w), 681 (w), 669 (w), 646 (w),
tions on geometry-optimized simplified structures of the title 625 (w); anal. calcd for C40H42N2S3 (647.0): C, 74.26; H, 6.54;
compounds nicely reproduce the trends of longest wavelength N, 4.33; found: C, 74.17; H, 6.79; N, 4.05.
absorption bands and allow the assignment of these transitions
to be largely charge-transfer from the adjacent phenothiazinyl 3b: According to the GP by reaction of 7-bromo-10,10'-dihexyl-
moieties to the central thienyl unit. This represents in principle 10H,10'H-3,3'-biphenothiazine (1b, 1.29 g, 2.00 mmol) after
a donor–acceptor–donor topology, suitable for further develop- chromatography on silica gel (hexane/THF 20:1) gave 435 mg
ment toward molecular electronics. Studies employing the (36%) of compound 3b as a yellow greenish resin. 1H NMR
presented synthetic methodology and the concept of bridging (600 MHz, CDCl3) δ 0.65–0.82 (m, 12H), 1.10–1.23 (m, 16H),
oligophenothiazines with conjugating bridges of variable elec- 1.26–1.36 (m, 8H), 1.62–1.76 (m, 8H), 3.62–3.79 (m, 8H),
tronic nature are currently underway.
6.64–6.84 (m, 10H), 6.93–7.09 (m, 6H), 7.09–7.26 (m, 12H);
13C NMR (151 MHz, CDCl3) δ 14.1 (CH3), 22.7 (CH2), 26.7
(CH2), 26.7 (CH2), 26.8 (CH2), 26.9 (CH2), 31.5 (CH2), 47.5
Experimental
3a (general procedure GP): 3-Bromo-10-hexyl-10H-phenothi- (CH2), 47.6 (CH2), 115.3 (CH), 115.4 (CH), 115.5 (CH), 115.5
azine (1a) (725 mg, 2.00 mmol) and dry THF (10.0 mL) were (CH), 122.4 (CH), 123.1 (CH), 124.2 (CH), 124.4 (Cquat), 124.4
placed in a microwave vessel with septum (80 mL) and the mix- (Cquat), 124.6 (CH), 124.8 (Cquat), 125.1 (CH), 125.1 (CH),
ture was deaerated by a constant stream of nitrogen through a 125.2 (CH), 125.3 (CH), 127.3 (CH), 127.5 (CH), 128.9 (Cquat),
syringe for 10 min. Then PdCl2(PPh3)2 (56.0 mg, 0.08 mmol), 134.2 (Cquat), 134.4 (Cquat), 141.9 (Cquat), 143.7 (Cquat), 144.2
CuI (15.0 mg, 0.08 mmol), PPh3 (21 mg, 0.08 mmol), (tri- (Cquat), 144.3 (Cquat),145.1 (Cquat); MS (MALDI) m/z: 1208.5
methylsilyl)acetylene (0.56 mL, 2.00 mmol), and piperidine ([M]+); UV–vis (CH2Cl2), λmax [nm] (ε): 266 (52100), 284
(5.00 mL, 50.4 mmol) were added. The closed vessel under (45900), 319 (32500), 404 (27700); IR (KBr) [cm−1]: 2951
nitrogen was heated at 55 °C (oil bath) for 16 h. Next, (w), 2922 (w), 2853 (w), 1456 (s), 1416 (w), 1375 (w), 1364
TBAF·3H2O (631 mg, 2.00 mmol) was added and the vessel (w), 1331 (m), 1292 (w), 1238 (m), 1192 (w), 1138 (w), 1105
open to ambient atmosphere was then stirred at room temp for (w), 1063 (w), 1040 (w), 872 (m), 797 (s), 745 (s), 727 (w), 706
16 h. Then, sodium sulfide nonahydrate (960 mg, 4.00 mmol) (w), 611 (w); anal. calcd for C76H80N4S5·H2O·2C4H8O (1209.8
and potassium hydroxide (224 mg, 4.00 mmol) were added and + 18.0 + 144.2): C, 73.53; H, 7.20; N, 4.08; found: C, 73.39; H,
the reaction mixture in the closed vessel was heated at 120 °C in 7.36; N, 4.29; HPLC (n-hexane) tR [min] (%) = 4.49 (99).
the microwave cavity for 30 min. After cooling to room temper-
ature the solvents were removed in vacuo and the residue was 3c: According to the GP by reaction of 7-bromo-10,10’,10’’-
filtered with THF through a short plug of Celite® and silica gel. trihexyl-10H,10’H,10’’H-[3,3’,7’,3’’]terphenothiazin (1c,
The solvents were removed in vacuo and the residue was puri- 1.85 g, 2.00 mmol) after chromatography on silica gel (hexane/
fied by chromatography on silica gel (hexane/dichlormethane THF 7:1 to 3:1) gave 955 mg (54%) of compound 3c as a
10:1) giving 218 mg (34%) of compound 3a as a yellow yellow greenish resin. 1H NMR (600 MHz, CDCl3) δ 0.75–0.88
greenish resin. Rf 0.53 (hexane/acetone 10:1); 1H NMR (300 (m, 18H), 1.08–1.33 (m, 24H), 1.31–1.40 (m, 12H), 1.66–1.81
MHz, acetone-d6) δ 0.84 (t, 3J = 7.1 Hz, 6 H), 1.21–1.33 (m, (m, 12H), 3.60–3.89 (m, 12H), 6.68–6.88 (m, 14H), 7.00–7.11
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2. Zhao, X.; Zhan, X. Chem. Soc. Rev. 2011, 40, 3728–3743.
(m, 6H), 7.13–7.37 (m, 20H); 13C NMR (151 MHz, CDCl3) δ
14.05 (CH3), 14.06 (CH3), 22.64 (CH2), 22.66 (CH2), 26.69
(CH2), 26.72 (CH2), 26.8 (CH2), 26.88 (CH2), 26.90 (CH2),
31.5 (CH2), 47.5 (CH2), 47.6 (CH2), 47.63 (CH2), 115.31 (CH),
115.37 (CH), 115.42 (CH), 115.46 (CH), 115.48 (CH), 122.3
(CH), 123.1 (CH), 124.2 (CH), 124.42 (Cquat), 124.44 (Cquat),
124.57 (CH), 124.68 (Cquat), 124.72 (Cquat), 124.8 (CH),
125.12 (CH), 125.14 (CH), 125.18 (CH), 125.19 (CH), 125.25
(CH), 125.29 (CH), 127.25 (CH), 127.5 (CH), 128.9 (Cquat),
134.18 (Cquat), 134.23 (Cquat), 134.30 (Cquat), 134.37 (Cquat),
141.9 (Cquat), 143.7 (Cquat), 143.9 (Cquat), 144.0 (Cquat), 144.20
(Cquat), 144.22 (Cquat), 145.1 (Cquat); MS (MALDI) m/z: 1770.7
([M]+); UV–vis (CH2Cl2), λmax [nm] (ε): 267 (103000), 283
(116200), 327 (61000), 379 (51900); IR (KBr) [cm−1]: 3024
(w), 2951 (w), 2922 (w), 2851 (w), 1603 (w), 1574 (w), 1454
(s), 1416 (w), 1377 (w), 1331 (w), 1294 (w), 1238 (m), 1190
(w), 1140 (w), 1105 (w), 1063 (w), 1038 (w), 968 (w), 928 (w),
910 (w), 872 (w), 802 (s), 745 (m), 729 (w), 691 (w); anal.
calcd for C112H118N6S7·H2O (1772.63 + 18.0): C, 75.13; H,
6.76; N, 4.69; found: C, 74.89; H, 6.50; N, 4.53; HPLC
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Supporting Information
The Supporting Information contains all experimental
procedures, spectroscopic and analytical data of compounds
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computed UV–vis spectra of ZINDO-CI and TD-DFT
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The authors cordially thank the Fonds der Chemischen Indus-
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