CC BY
11
УДК 678.7
A. A. Olkhov, B. M. Rumyantsev, G. E. Zaikov, A. A. Ischenko, V. F. Shkodich, А. М. Kochnev
STRUCTURE AND PHOTOELECTRIC PROPERTIES OF POLYIMIDES BASED
ON N,N',N",N"'- SUBSTITUTED PAREPHENYLENEDIAMINE AND DIANHYDRIDES
OF AROMATIC TETRACARBOXYLIC ACIDS
Key words: electrophotographic method, polyimides, Suzuki coupling reaction, photoelectric characteristics, photoelectric sensitivity, charge transfer complex, photogeneration quantum yield, photogeneration mechanism, cation-radical, anion-radical, photovoltaic
characteristics.
The photoelectric characteristics of the newly synthesized polyimides PI are investigated by using the electrophotographic method. A novel conjugated polymers, polyimides based on N,N',N",N"'-substituted paraphenylenediamine and dianhydrides of aromatic tetracarboxylic acids, was prepared via Suzuki coupling reaction. The polymer exhibits excellent solubility in common organic solvent, and has high thermal stability such as Tdia at 453 0C in nitrogen atmosphere and Tg at about 140 0C. The photoelectric sensitivity of the PI films (3 Dm thickness) is observed in the UV, and visible spectral regions, due to the interactions with charge transfer between donor and acceptor fragments of the PI chains (formation of charge transfer complex, CTC). Study of the photogeneration quantum yield field dependence gives the evidence that the photogeneration mechanism is a field assisted thermodissociation of radical ion pairs kinetically associated with the excited CTC. The second important mechanism of photogeneration is photostimulation of long-lived stable cation-radicals of the donor PI fragments, representing the hole (major carriers) captured by deep centers (photostimulated currents). Accumulation of the cation-radicals in the dark and photoprocesses leads to the dependence of photovoltaic characteristics on the number of charge-discharge cycles of the sample.
Ключевые слова: электрофотографический метод, полиимиды, реакция сочетания Сузуки, фотоэлектрические характеристики, фотоэлектрическая чувствительность, комплексный перенос заряда, фотогенерация квантовый выход, механизм фотогенерации, катион-радикальные, анион-радикальные, фотоэлектрические характеристики.
Фотоэлектрические характеристики синтезированных полиимидов (ПИ) исследованы электрофотографическим методом. Новые конъюгированные полимеры, полиамиды на основе N, N', N", N" - замещенных парафени-лендиамин и диангидридов тетракарбоновых ароматических кислот, были подготовлены с помощью реакции сочетания Сузуки. Полимер обладает отличной растворимостью в органическом растворителе, и имеет высокую термическую стабильность, например TD10 при 453 °С в атмосфере азота и при Tg около 140°С. Фотоэлектрическая чувствительность ПИ пленок (Зцм толщина) наблюдается в УФ и видимой областях спектра, благодаря взаимодействию переноса заряда между донорными и акцепторными участками ПИ цепей (образование комплексного переноса заряда, КПЗ). Исследование области зависимости фотогенерации квантового выхода доказывает то, что механизм фотогенерации является областью, способствующей к термодиссоциации ион-радикальных пар, кинетически связанных с возбужденным КПЗ. Вторым важным механизмом фотогенерации является фотостимуляция долгоживущих стабильных катион-радикалов - участков ПИ-доноров, представляющих отверстие (основные носители), захваченное глубокими центрами (фотостимулированные токи). Накопление катион-радикалов, в темноте и фотопроцессах приводит к зависимости фотоэлектрических характеристик от количества циклов заряд-разряда образца.
Introduction
In the last two decades, p-conjugated polymers have attracted considerable interests because of their potential applications in electrochromics, [1-4] light emitting diodes, [5-9] organic thin film transistors, [10-14] photovoltaic's, [15-18] and polymer memories [19-20]. Fluorene and its analogous derivatives have drawn much attention of optoelectronics because they generally have good solubility, high luminescent efficiency, and very good charge-transfer mobility in both neutral and doped states [21-24]. However, it is also known that they have drawbacks such as unsatisfied thermal stability and excimers formation in the solid state [25, 26]. The applications for electrochromic conjugated polymers are quite diverse due to several favorable properties of these materials, like stable oxidation state, fast switching times, and excellent switching reproducibility [27]. These excellent properties led to the development of many technological applications such as self-darkening rear-view mirrors, adjustably darkening windows, large-scale electrochromic
screens, and chameleon materials [28-30]. Electron-rich triarylamines are known to be easily oxidized to form stable polarons, and the oxidation process is always associated with a noticeable change of the coloration. Furthermore, triarylamine-based polymers are not only widely used as the hole-transport layer in electroluminescent diodes but also show interesting electrochromic behavior [31-33]. A conjugated polymer derived from the Suzuki coupling reaction with a Dluorine derivative was prepared, and its general properties such as thermal and optical properties as well as electrochemical and electrochromic property were investigated and discussed earlier [34]. The high photoelectric characteristics of polyimides (PI) based on triphenylamine and its derivatives [35], and also their composites with the organic and inorganic semiconductors [36,37] (photoelectric sensitivity (PES) S, the quantum yield of the charge carrier photogeneration p, their drift length lD, collection coefficient C(Z)) are the basis of their applications in a whole series of optoelectronic devices: photovoltaic and electroluminescent cells [38,39], photodetectors [40],
organic phototransistors [41,42]. In the present work, the photoelectric characteristics of the newly synthesized PI [34, 43] are investigated by using the electrophotographic (EPG) method [42].
Experimental
Synthesis of homopolyimides. The polyimides were prepared in the procedures similar to one described in Appendix 1. One of the examples is described as follows. To the stirred solution of 0.6g (0.883 mmol) of diamine (4, Appendix 1) in 5 mL of DMAc, 0.382g (0.883 mmol) of 6FDA was gradually added. The mixture was stirred at room temperature for 4 h under nitrogen atmosphere to form poly(amic acid). Chemical cyclodehydration was carried out by adding equal molar mixture of acetic anhydride and pyridine into the above-mentioned poly(amic acid) solution with stirring at room temperature for 1 h, and then treated at 100 oC for 4 h. The polymer solution was poured into methanol. The precipitate was collected by filtration, washed thoroughly with methanol, and then dried at 100 °C under vacuum.
xnx
TC
Electrophotographic study. Electrophotographic method involves the studying of the kinetics of the surface potential dark and photoinduced decay in polymer films, charged in the field of positive or negative corona discharge. The maximum potential of the charging V and the rate of the potential dark decay (dV/dt)D are determined by the dark conductivity of the films: the higher it is, the lower the V value and higher (dV/dt)D are. Potential photoinduced decay (1/I)(dV/dt) (where the I - intensity of excitation) is determined by the rate of the capacitor photodischarging formed by the ionic contact (aeroions on the film surface) as one electrode and glass conducting support (Indium Tin Oxide, ITO) as the second electrode with the induced charge of opposite sign on it. The potential photodischarging rate depends on the effective charge carrier photogeneration quantum yield in the film volume (xerographic output, peff), carrier collection efficiency on the electrodes C(Z) and the portion of the absorbed exciting light, P:
(1/I) [dV/dt - (dV/dt)D)] = (ed/ss0) Peff P, (1) where peff = PC(Z); C(Z) - charge carrier collection efficiency, Z = ^Vx/d2 - ratio of the carrier drift length (lD = ^Vx/d) to the film thickness d, ^ - carrier drift mobility, t - their lifetime, e - electron charge. The function C(Z) for the strong and weak absorption is given in [42], from which it follows that for Z < 1, C(Z) = Z, and for Z > 1, C(Z) = 1 (strong absorption) and C(Z) = 1/2 for weak absorption. It is observed [39], that for the polymers, P and C(Z) values usually are strongly depend on the field strength E = V/d. The accuracy of the P measurement was
determined by the accuracy of the I, P and film thickness d measurements and was estimated ~20%. The photoelectric sensitivity (PES) S ([m2/J]) is defined as the reciprocal value of the half decay exposure time t1/2 of the initial charging potential V:
S = (It1/2)-1 = (Peff Pde)/[E(hv)Vss0], (2)
where E(hv) - excitation photon energy. The accuracy of the S value measurement was estimated ~10% and it was determined by the accuracy of excitation intensity I measurements. Thus, the electrophotographic method makes it possible to obtain the following photoelectric characteristics of polymer samples: photoelectric sensitivity, the carrier photogeneration quantum yield (1), and from the field dependence of peff (E) it is possible to estimate carrier drift length: at the field strength E0, for which the change of C(Z) dependence from C(Z) = Z to C(Z) = const is observed, drift length is equal to the film thickness, lD = ^E0t = d. Experimental setup makes it possible to determine both the optical density of the sample Dx under monochromatic or integral excitation, and to measure also the influence of the ionic contact field on it. Knowing optical density, it is possible to estimate the portion of the absorbed excitation light energy:
P = 1 - exp[- (D-D0)], (3)
where D is the film optical density and D0 - equivalent optical density, caused by the light reflection from the front and rear sample surfaces as well as by light scattering. The sign of major carriers can be determined via the comparison of PES values for the positive (S+) and negative (S-) corona charging of free surface under the heterogeneous excitation by the strongly absorbed UV light: with S+ > S- major carriers are holes, with S- > S+ -electrons. The PI films of 3 |im thickness were prepared by the cast of polymer solution in the chlorine - containing solvents onto the conducting ITO glass supports and the subsequent drying under the ambient conditions at 50-100 0C. The Pis under study possess good solubility and excellent film-forming properties
Results and Discussions Study of the Photoelectric Sensitivity of the PI films and its connection with the Charge Transfer Complex formation
Photoelectric sensitivity of the PI films is observed and the charge carrier photogeneration quantum yield is determined for the films of the new class of PI based on N,N',N",N"' - substituted paraphenylene-diamine (electron-donor fragment D) and dianhydrides of aromatic tetracarboxylic acids (electron-acceptor fragment A). PI series denoted as PI A1 to PI A5, see list of samples above. A study of PES spectral dependence S(^) shows that the highest sensitivity (up to 30 m2/J) is observed at the UV region (200 - 400 nm). In the visible region (400 -700 nm) there is a PES band which collapses to the long-wave edge (Figure1).
Comparison of the PES spectral dependence with the absorption spectrum of the films evidences that PES in the visible region is due to the formation of weak electronic Donor-Acceptor (D-A) ChargeTransfer Complexes (CTC) with absorption maxima in the region of 400 - 600 nm [44]. The maxima and band absorption edge of the CTC are determined. The most
clearly expressed CTC bands are observed for PI A2 and PI A3 films with flat absorption maxima in the 500- 560 nm region. For PI A1, PI A4 and PI A5 films CTC bands are essentially weaker with flat maxima shifted to short wavelengths, 420 - 480 nm. The energy position of the long-wavelength absorption band edge of the CTC and PES is determined, which is an analogue of the band gap for semiconductors, Eg, that allows to estimate the relative affinity energy values for the acceptor fragments EA (at the same values of the ionization potential of the donor fragments, ID = 7.0 - Ph = 5.5 eV, Ph - polarization energy of holes) from the expression:
Eg = Id - Ea - (Ph + Pe), (4)
where Pe -polarization energy for electrons.
D,
252015105-
-1,0 -0,8 -0,6 -0,4 -0,2
X, nm
Fig. 1 - Spectra of the photoelectric sensitivity Sx(1): (+ charging, V = 30-36 V; the number of cycles N > 10) and the optical density Dx(2) for the film PI A2 (thickness d = 3 |m)
Table 1 - Eg and (EA + Pe) values (in eV) for PI A1 - PI A5 film samples; Pe = 1.5 eV
PI A1 Eg = 2.2* (EA+Pe) = 3.3*
PI A2 1.9 3.6
PI A3 2.0 3.5
PI A4 2.6 2.9
PI A5 2.4 3.1
* Estimated average uncertainty for Eg and (EA+Pe) values is 0.1 eV.
As can be seen from Table 1, the highest EA values are observed for PI A2 and PI A3 acceptor fragments (3.6 and 3.5 eV, respectively) which characterized by the lowest Eg (1.9 and 2.0 eV) and the most pronounced CTC band as well as high PES in the visible region (up to 5 -20 m2/J). The PI A1, PI A4 and PI A5 films possess the lower EA values, weaker CTC bands and lower PES (of about 1- 4 m2/J).
These distinct spectral peaks (in the region of 440480 nm, 540-560 nm and 640-660 nm) are registered for PI A1, PI A3, PI A5 (absorption spectrum) and PI A2 (PES spectrum, Figure1). They are ascribed in this work to the formation and accumulation of the stabilized cation-radicals (D+) (and perhaps anion-radicals (A-)) of polymer fragments arising in the PI as a result of the dark-and photo-processes [45]. Some evidence of this assumption is the PES found in the red region (X > 600 nm, outside the CTC band) with a weak maximum in the
absorption band of triphenylamine type cation-radical (640-660 nm) due to its photo-stimulation [45].
The photo-generation quantum yield for the UV (PI A1-PI A5) and visible spectrum (PI A1) is determined. On varying charging potential V a nonlinear field dependence of photo-generation quantum yield P(E) ~ En (Figure 2) is revealed. The exponent n increases with increasing excitation wavelength X from n ~ 1.2 to n ~ 1.8 on changing X from 257 to 547 nm, indicating that the photo-generation occurs via the field assisted thermo-dissociation (FATD) of ion pairs (IP), kinetically coupled with the excited states of the CTC:
FATD
CTC + hucT (holes)
E, T
CTC* ^ [D+... A-] ^ carriers
(5)
7,00x10
p, electron/quantum
2 3
1,00x103 3,31x105 6,61x105 9,91x105
E, V/cm
Fig. 2 - Field dependence of charge carrier photogeneration quantum yield P(E) for the PI A2 (1), PI A1 (2, 4-6) and PI A3 (3) films, under excitation by monochromatic light: 257 nm (2) and 365 nm (1, 3, and 4); 436 nm (5) and 547 nm (6). Positive charging (N > 10), the field changed by the time variation of corona. P in electrons/quanta, E in V/cm
The highest p values in the UV region (up to 0.1 in a field E = 5.7105 V/cm) are obtained for films PI A3 and PI A2 (P = 0.02, E = 105 V / cm). Using the geminate recombination Onsager model [46, 47] to interpret the field dependence of p(E), it is possible to determine ion-pair parameters: the initial yield and initial separation r0. For films PI A1 with increasing excitation wavelength (from 257 to 547 nm) value of r0 is reduced from 3.6 - 4.5 nm to 2.0 nm, and the value of increases from 0.2 to 0.7. However under excitation in the red spectral region (640-680 nm, outside of the CTC band), the value r0 increases to 3.0 nm, which suggests that under photostimulation of stabilized cation-radical IP1 is formed that differs the IP in the scheme (3). Comparison of the field dependences of S and p allows to conclude that for the PI films drift length of the generated carriers (holes) lD > d (3 |im) for E > 105 V/cm and hence to estimate ^x > 310-9 cm2/V. Major carriers in the studied PI - holes since under free surface excitation by strongly absorbed UV light, S + > S-.
2. Effect of stable cation-radicals accumulation during repeating charge- discharge cycles on the photoelectric characteristics of the PI films; the observation of the photo-stimulated current (PSC). A strong dependence of the photoelectric characteristics of the samples (the
—>
S m /J
1,05x10 -
-2
3,50x10 -
potential of charging, PES in the red region, Sred) on the number of charge-discharge cycles N is found: when changing N from 1 to 10, V and Sred values significantly (of about several times) increase (Figure 3). In the UV region the rise only V is observed; the growth of PES is very small or completely absent.
S,, m2/J V, V
30-
Sk
0,40,2-
V, V
100
-20 -10
Fig. 3 - Photoelectric sensitivity in the UV (1 = 365 nm) Sx (1, 2) and red region (1 > 600 nm) Sred (5), as well as the maximal charge potential V (3, 4, 6) versus number of charge-discharge cycles N for films PI A5 (2, 3) and PI A2 (1, 4-6); + charging
Usually the absence of surface charging associated with the dark injection of carriers from the electrodes into the bulk of the film (holes in case of positively charged free surface), leading to a sharp increase in dark conductivity. The increase in the value of V at the positive charge indicates blocking of the dark hole injection from the free surface when N > 3 - 4. The most probable reason is the appearance in the film bulk near the electrode positively charged layer of stabilized cation-radicals (electrode polarization). The latter are holes (h+) trapped by deep centers:
dark injection capture + Electrode+D ^h+ (mobile hole)^cation-radical (6)
Accumulation and stabilization of the cation-radicals near the electrode leads not only to stop the dark hole injection, but also to a drop of dark conductivity, increase the V value, as well as to the observation of photo-stimulated currents (PSC), which manifest themselves as growth of PES in the red spectral range Sred, outside the absorption band of the CTC (absorption of cation-radicals) (Figure 3):
FATD
Cation-radical + hu1 ^ IP1 ^ curriers (PSC) (7)
The growth of Sred with increasing N (Figure 3) is partly due to its field dependence caused by growth of the field strength E = V/d. Therefore, it was specially checked that in the red region the pure field dependence due to the ion pair IP1 FATD (7) have the form: p ~ En (n = 1.35-1.60) and by (2) S ~ En-1, i.e. weakly dependent on E, so that the growth of Sred(N) is partly due to the accumulation of the cation-radicals. Under conditions when V does not depend on N (for N > 10), the V value was changing by varying the time of corona discharge. In some cases (Figure 5) the growth of Sred was observed at constant V
that points directly to the effect of the cation-radical accumulation.
The observation of PSC indicates a high cation-radical lifetime, t > (oI)-1 (o - absorption cross section). If o = 10-17 - 10-16 cm2 [5], I = 1015 cm-2 s-1, an estimate of t > 10 s is obtained. It should be noted that the results of this study evidences that there is a range of the cation-radical states from labile (t = 1-10 s) to a fully stable ones (t > 103 s) which are involved in the process of photo-stimulated generation. Similar stabilized cation-radicals and related photo-stimulated currents for the PI based on substituted triphenylamines resulting from irreversible photochemical transformation of free-radical type with the halogen hydrocarbons are observed in [45].
Conclusions
A novel conjugated polymers, polyimides based on N,N',N",N'"-substituted
paraphenylenediamine and dianhydrides of aromatic tetracarboxylic acids, was successfully prepared via Suzuki coupling reaction. The polymer exhibits excellent solubility in common organic solvent, and has high thermal stability such as Td10 at 453 0C in nitrogen atmosphere and Tg at about 140 0C.
The photoelectric sensitivity of the PI films (3 ^m thickness) is observed in the UV, and visible spectral regions, due to the interactions with charge transfer between donor and acceptor fragments of the PI chains (formation of CTC). Study of the photogeneration quantum yield field dependence gives the evidence that the photo-generation mechanism is a field assisted thermo-dissociation of radical ion pairs kinetically associated with the excited CTC.
The second important mechanism of photogeneration is photostimulation of long-lived stable cation-radicals of the donor PI fragments, representing the hole (major carriers) captured by deep centers (photo-stimulated currents). Accumulation of the cation-radicals in the dark and photo-processes leads to the dependence of photovoltaic characteristics on the number of charge-discharge cycles of the sample.
Appendix 1 Materials:
MM-bis(4-aminohenyl)-N',N'-bis[4-(2-phenyl-2-isopropyl)phenyl]-1,4-phenylene diamine was synthesized by a well-known synthetic route starting from bis(4-tert-butylphenyl)amine and p-fluoronitrobenzene as shown in Scheme 1 [43]. The synthetic details and the characterization data of this diaminemonomer have been described in [43]. Bis[4-(2-phenyl-2-isopropyl)phenyl]amine (OUCHI SHINKO), 4-fluoro-nitro- benzene (ACROS), cesium fluoride (ACROS), sodium hydride (95%; dry; ALDRICH), 10% Pd/C (MERCK), and hydrazine monohydrate (MERCK) were used as received. N,N-Dimethylacetamide (DMAc; MERCK), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidinone (NMP) (MERCK), and pyridine (MERCK), were dried over calcium hydride overnight, distilled under reduced pressure, and stored over 4 A molecular sieves in a sealed bottle. Iodobenzene, bis(dibenzylideneacetone) palladium [Pd(dba)2], 1,1'-
4
N
2
3
4
5
6
7
8
9
bis(diphenylphosphino)-ferrocene (DPPF), sodium tert-butoxide were purchased from ACROS. Commercially available aromatic tetracarboxylic dianhydrides such as 4,4 '-hexafluoroisopropylidenediphathalic dianhydride (A1; CHRISKEV) (6FDA), 3,3 ',4,4'-diphenyl sulfone-tetracarboxylic dianhydride (A2; TCI) (DSDA), 4,4'-oxydiphthalic anhydride (A3; TCI) (ODPA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (A4; CHRISKEV) (BTDA) and 3,3 ',4,4'-bitetracarboxylic dianhydride (A5; CHRISKEV) (BDA), and were purified by vacuum sublimation.
„35
Appendix 2 Monomer synthesisJ Synthesis of bis[4-(2-phenyl-2-isopropyl)phenyl]-4-nitrophenylamine) (1). In a 500 mL three neck round-bottom flask was placed bis[4-(2-phenyl-2-isopropyl)phenyl]amine (20.0 g, 49 mmol), 4-fluoro-nitrobenzene (5.23 g, 49 mmol), sodium hydroxide (1.18 g, 49 mmol), and 120 mL DMSO. The mixture was heated with stirring at 120 oC for 24 h. The reaction mixture was cooled and then poured into 1 liter methanol. The yellow precipitate was collected by filtration and dried under vacuum. The product was purified by silica gel
column chromatography (n-hexane dichloromethane = 2
: 1) to afford nitro compound 1 16.3 g in a 63 % yield; mp 150-151 oC by DSC (10 oC /min).
IR (KBr): 1585, 1342 cm-1 (NO2 stretch). 1H NMR: (CDCl3): 5 (ppm)=1.77 (s, 6H, Hd); 6.93-6.95 (d, 1H, Hf, /=9.5 Hz); 7.12-7.14 (d, 2H, He, /=10.1 Hz); 7.24-7.27 (m, 1H, Ha); 7.28-7.30 (d, 2H, Hd,' /=10.1 Hz); 7.35-7.36 (d, 2H, Hb, /=5.0 Hz); 7.37-7.38 (d, 2H, Hc, /=5.0 Hz); 8.05-8.08 (d, 1H, Hg, /=15.0 Hz).
13C NMR (CDCl3): 5 (ppm)=30.6 (C6), 42.6 (C5), 117.4 (C12), 125.3 (C13), 125.7 (C1), 125.9 (C9), 126.6 (C2), 128.0 (C3), 128.1 (C8), 139.6 (C14), 142.8 (C10), 148.2 (C7), 150.0 (C4), 153.4 (Cn).
Anal. Calcd for C36H34N2O2: C, 82.10%; H, 6.51%; N, 5.32%. Found: C, 81.67%; H, 6.39%; N, 5.21%.
C-CH3
(1)
Synthesis of bis[4-(2-phenyl-2-isopropyl)phenyl]-4-aminophenylamine (2). In a 500 mL three neck round-bottom flask was placed nitro compound 1 (20 g, 38 mmol), Pd/C (0.4 g), ethanol 200 mL. After the addition of 14 mL of hydrazine monohydrate, the solution was stirred at reflux temperature for 12 h. After the solution was cooled down to room temperature, the solution was filtered to remove the catalyst, and the crude product was recrystallized from ethanol yielded 12.5 g (yield: 66%) of
the compound 2, mp 110-114°C by DSC (10 oC /min). IR (KBr): 3432, 3356 cm-1 (NH2 stretch).
1H NMR: (DMSO-4): 5 (ppm)= 1.57 (s, 6H, Hh); 5.02
(s, 1H, NH2); 6.56-6.58 (d, 1H, Hg, /=8.5 Hz); 6.76-6.77 (d, 1H, Hf, /=5.0 Hz); 6.77-6.79 (d, 2H, He, /=10.0 Hz); 6.98-7.00 (d, 2H, Hd, /=10.0 Hz); 7.09-7.12 (m, H, Ha); 7.19-7.20 (d, 2H, Hb, /=5.0 Hz); 7.20-7.21 (d, 2H, Hc, /=5.0 Hz).
13C NMR (DMSO-4): 5 (ppm)= 30.3 (C6), 41.7 (C5), 114.9 (C13), 120.73 (C9), 125.3 (C1), 126.2 (C3), 126.9 (C8), 127.8 (C2), 127.9 (C12), 135.2 (C14), 142.5 (C10), 145.4 (C7), 145.9 (C11), 150.3 (C4). Elem- Anal- Calcd. For C36H36N2: C, 87.05%; H,
7.31%; N, 5.64%. Found C, 86.9%; H, 7.13%; N, 5.61%.
nh2
d
CH3
CH3
( 2)
Synthesis of N,N,-bis(4-nitrophenyl)-N',N'-bis[4-(2-phenyl-2-isopropyl)phenyl]-1,4-phenylene-diamine (3). In a 250 mL three neck round-bottom flask was placed bis- [4-(2-phenyl- 2-isopropyl)phenyl]-4-
aminophenylamine (2) (7.26 g, 14.63 mmol), 4-fluoro-nitro- benzene (4.13 g, 29.27 mmol), cesium fluoride (4.41 g, 29.27 mmol), and 80 mL DMSO. The mixture was heated with stirring at 120 oC for 24 h. The reaction mixture was cooled and then poured into 500 mL methanol. The red precipitate was collected by filtration and dried under vacuum. The product was purified by silica
gel column chromatography (n-hexane dichloromethane = 1: 1) to afford dinitro compound (3) in a 65% yield; mp 224-225 oC (by DSC; 10 oC /min).
IR (KBr): 1580, 1341 cm-1(NO2 stretch). 1H NMR (CDCl3): 5 (ppm)= 1.70 (s, 6H, Hd); 6.976.99 (d, 2H, Hh, /=10.0 Hz) 7.04-7.05 (d, 2H, Hf, /=5.0
Hz) 7.05-7.07 (d, 2H, Hg, /=10.0 Hz); 7.15-7.17 (d, 2H, He, /=10.0 Hz); 7.19-7.20 (d, 2H, Hi, /=5.0 Hz); 7.207.21 (m, 1H, Ha); 7.28-7.29 (d, 2H, Hc, /=5.0 Hz); 7.307.31 (d, 2H, Hb, /=5.0 Hz); 8.14-8.17 (d, 2H, Hj, /=15.0 Hz).
13C NMR (CDCl3): 5 (ppm)= 30.7 (C6), 42.5 (C5), 121.8 (C16), 123.2 (C12), 124.3 (C9), 125.4 (C17), 125.6 (C1), 126.6 (C3), 127.7 (C8), 127.9 (C2), 128.0 (C13), 137.2 (C14), 142.3 (C18), 144.3 (C10), 146.1 (C7), 147.0 (C11), 150.4 (C4), 151.7 (C15).
Elem. Anal. Calcd. For C48H42N4O4: C, 78.03 %; H, 5.73%; N, 7.58%. Found C, 77.57%; H, 5.63%; N, 7.45%.
a
a
a
Synthesis of N,N,-bis(4-aminohenyl)-N',N'-bis[4-(2-phenyl-2-isopropyl)phenyl]-1,4-phenylene-diamine (4). The dinitro compound (3) (5 g, 6.77 mmol ), Pd/C (0.2 g), and 150 mL ethanol were taken in a three-necked flask and hydrazine monohydrate (10 mL) was added dropwise over a period of 30 min at 90 oC. Upon completing the addition, the solution was stirred at reflux temperature for 12 h. After the solution was cooled down to room temperature, the solution was filtered to remove the catalyst, and the crude product was purified by silica gel column chro-
matography (n-hexane ethyl acetate = 2: 1) to afford diamine monomer (4) 2.3 g (yield: 50%), mp 149-151 oC by DSC (10 oC /min).
IR (KBr): 3445, 3360 cm-1(NH2 stretch). 1H NMR (DMSO-4): 5 (ppm)= 1.56 (s, 6H, Hd); 6.536.55 (d, 2H, Hf, /=10.1 Hz); 6.56-6.58 (d, 1H, Hh, /=10.1 Hz); 6.75-6.77 (d, 1H, Hg, /=10.1 Hz); 6.77-6.79 (d, 2H, Hi, /=10.1 Hz,); 6.80-6.82 (d, 2H, He, /=10.1 Hz); 6.997.01 (d, 2H, Hj, /=10.1 Hz); 7.09-7.12 (m, 1H, Ha); 7.197.20 (d, 2H, Hc, /=5.1 Hz); 7.21-7.23 (d, 2H, Hb /=10.1 Hz).
13C NMR (DMSO-i6):5 (ppm)= 30.3 (C6), 41.7 (C5), 114.8 (C8), 117.8 (C13), 121.3 (C16), 125.3 (C1), 126.2 (C3), 126.7 (C12), 127.0 (C9), 127.1 (C17), 127.8 (C2), 136.0 (C10), 137.2 (C14), 143.0 (C18), 145.2 (C15), 145.3 (C7), 146.2 (C11), 150.2 (C4).
Elem- Anal- Calcd. For C48H46N4: C, 84.92%; H, 6.83%; N, 8.25%. Found C, 84.11%; H, 6.77%; N, 8.17%.
j i 16 17
4
Appendix 3
The IR spectrum of A1 (film) exhibited characteristic imide absorption at 1779 (asymmetrical carbonyl stretching), 1726 (symmetrical carbonyl stretching) and 744 cm-1 (imide ring deformation).
XH NMR (CDCI3): 5 (ppm)= 1.70 (s, 6H, Hd); 7.027.04 (d, 2H, Hf); 7.04-7.10 (d, 2H, Hh + Hg); 7.13-7.14 (d, 2H, He); 7.16-7.20 (m, 1H, Ha); 7.27-7.28 (d, 2H, Hi); 7.27-7.30 (d, 4H, Hb + Hc); 7.32-7.33 (d, 2H, Hj); 7.88-7.90 (d, 2H, Hi); 7.99 (s, 1H, Hk); 8.05-8.07 (d, 2H, Hm).
Elem- Anal- Calcd. For (C69H54NsO4F6)n: C, 74.18%;
H, 4.87% N, 5.01%. Found: C, 73.01%; H, 4.23% N, 5.02%.
Acknowledgements. This work supported by RFBR grants 10-02-92000-NNC_a, 11-02-00868-a, 11-02-12041-ÜFI-m-2011 and grant of the Ministry of Education and Science of the RF 1B-5-343.
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© A. A. Olkhov - PhD, docent, Moscow Plekhanov Russian University of Economics, Moscow, Russia, [email protected]; B. M. Rumyantsev - Dr.sc.(Tech.), Prof Institute of Chemical Physics, RAS, Moscow, Russia; G. E. Zaikov - Dr.sc.(chemistry), Prof., Institute of Biochemical Physics, RAS, Moscow, Russia, [email protected]; A. A. Ischenko - Dr.sc.(chemistry), Prof., Moscow Lomonosov State University of Fine Chemical Technology, Moscow, Russia; V. F. Shkodich - Ph.D, Assoc. Professor Department of technology of synthetic rubber, Kazan National Research Technological University, [email protected]; A. M. Kochnev - Professor Department of technology of synthetic rubber, Kazan National Research Technological University, [email protected].
