Hydrazones possessing a phenyl-1,2,3,4-tetrahydroquinoline moiety as hole transporting materials

Article abstract of DOI:10.1007/s00706-006-0529-6

Hydrazones containing 1-phenyl-1,2,3,4-tetrahydroquinoline units were synthesized starting from diphenylamine. These compounds were found to constitute novel hole transporting materials and were characterized by the time of flight method. The hole drift m

Full text of DOI:10.1007/s00706-006-0529-6

Monatshefte f€ur Chemie 137, 1401–1409 (2006)
DOI 10.1007/s00706-006-0529-6
Hydrazones Possessing a Phenyl-1,2,3,4-
tetrahydroquinoline Moiety as Hole
Transporting Materials
Vytautas Getautis1;ꢀ, Albina Stanisauskaite1, Tadas Malinauskas1,
Jolanta Stumbraite1, Valentas Gaidelis2, and Vygintas Jankauskas2
1
Faculty of Chemical Technology, Kaunas University of Technology, 50270 Kaunas,
Lithuania
2
Department of Solid State Electronics, Vilnius University, 10222 Vilnius, Lithuania
Received January 23, 2006; accepted (revised) February 17, 2006
Published online October 3, 2006 # Springer-Verlag 2006
Summary. Hydrazones containing 1-phenyl-1,2,3,4-tetrahydroquinoline units were synthesized start-
ing from diphenylamine. These compounds were found to constitute novel hole transporting materials
and were characterized by the time of flight method. The hole drift mobility in these compounds ex-
ceeds 10ꢁ6 cm2 Vꢁ1 sꢁ1 at an electric field of 106 V cmꢁ1
.
Keywords. Hydrazone; Epoxide; 1-Phenyl-1,2,3,4-tetrahydroquinoline; Charge transport.
Introduction
During recent years rapid developments in the chemistry of 1,2,3,4-tetrahydroquino-
lines were observed. One of the main interests in them is due to their biological
activities. Thus, many relatively simple synthetic 1,2,3,4-tetrahydroquinolines are
already used or have been tested as potential drugs [1–3]. Besides pharmaceutical
applications, tetrahydroquinoline derivatives are useful as pesticides [4], antioxi-
dants [5], corrosion inhibitors [6], and active components of various dyes [7, 8].
They are also widely used in modern recording technologies: as intermediates for
photographic couplers [9], as high sensitivity photosensitizers in photography [10],
in the preparation of optical information recording media [11], and as charge
transporting materials in electrophotographic photoconductors [12].
Compounds possessing hydrazone moieties are also well known for their photo-
responsible properties [13]. High photosensitivity, simple synthesis, and low price are
the advantages of the hydrazones against other hole transporting materials. Low mo-
lecular weight transporting materials (TMs) containing hydrazone moieties are usually
ꢀ
Corresponding author. E-mail: vgetaut@ktu.lt

1402
V. Getautis et al.
crystalline materials, not capable offorming thin neat homogenous layers, and must be
used in combination with polymeric hosts, usually polycarbonate (PC). Aromatic
hydrazone molecules dispersed in a binder polymer are used as the main constituent
of electrophotographic devices due to their excellent hole-transporting property [14].
Recently, because of their rapid charge transporting ability, more attention has been
paid to organic photoreceptors with hydrazones possessing 1-phenyl-1,2,3,4-tetra-
hydroquinoline moieties as hole transporting materials [15–17]. Unfortunately, the
multi-step synthesis of the starting 1-phenyl-1,2,3,4-tetrahydroquinoline limits the
development of organic photoreceptors with this promising moiety.
In the present article we report the synthesis, characterization, and photocon-
ductive properties of the hydrazones 6a and 6b possessing the 1-phenyl-1,2,3,4-
tetrahydroquinoline moiety as hole transporting materials. The molecules of these
TMs consist of a large ꢀ-electron system conjugated through nitrogen atoms and a
flexible oxiranylalkyl group attached to it. The molecular structure of these TMs
makes crystallisation in solid state difficult and improves adhesion and compat-
ibility with PC. Another peculiarity of these functionalized hydrazones is the pos-
sibility to use 6a and 6b as precursors for the synthesis of a novel class of hole TMs
possessing a 1-phenyl-1,2,3,4-tetrahydroquinoline moiety [18–20].
Results and Discussion
Contrary to the multi-step synthesis of the widely used 1-phenyl-1,2,3,4-tetrahy-
droquinoline, the starting 3-hydroxy-1-phenyl-1,2,3,4-tetrahydroquinoline (1) was
Scheme 1

Hole Transporting Materials
1403
obtained by a one-pot reaction of diphenylamine with epichlorohydrin (Scheme 1).
At first, in order to protect hydroxyl group, 1 was converted to 2. The next step
was a Vilsmeier formylation followed by condensation of the resulting 3 with
hydrazine derivatives to get hydrazones 4a and 4b with different substituents at
the hydrazone N-atom. Then, the hydroxyl group was deprotected to give the
1-phenyl-1,2,3,4-tetrahydroquinoline hydrazones 5a and 5b. Finally, by interaction
of 5a and 5b with epichlorohydrin in presence of KOH, 3-oxiranylmethoxy-1-
phenyl-1,2,3,4-tetrahydroquinoline-6-carboxaldehyde N,N-diphenylhydrazone (6a)
and 3-oxiranylmethoxy-1-phenyl-1,2,3,4-tetrahydroquinoline-6-carboxaldehyde
N-phenyl-N-methylhydrazone (6b) were isolated.
The chemical structures of 6a and 6b were confirmed by IR, UV, and 1H NMR
spectrometry. In the 1H NMR spectra of 6a and 6b the epoxy group gave a double
set of signals of the AB part of an ABX system at 2.99–2.50 ppm, which indicated
that due to the presence of two stereogenic centers, the isolated hydrazones were
mixtures of diastereomers.
Since ꢀ-electrons are very important for the charge transporting process in the
TM structures, the absorption spectra of 6a and 6b were recorded. Electron transi-
tions to the higher energy states in the investigated derivatives give two main
absorption maxima (Fig. 1) at ca. 210 and 370 nm. The comparison of the UV=Vis
Vis spectra of 6a and 6b with the starting 1 showed that the second absorption band
is bathochromically shifted by 72 nm and is hyperchromically intensified due to the
ꢀ-electron conjugation through the lone electron pair at the nitrogen atom. On the
other hand, only a negligible bathochromic shift was observed for the diphenyl
substituted hydrazone 6a in comparison with the methylphenyl substituted 6b. The
former acts somewhat unusually – introduction of an additional aromatic moiety
does not lead to a marked bathochromic shift.
The results of the electron photoemission in air are presented in Fig. 2. The
ionization potential (Ip) value for 6a is 5.37 eV. Replacement of the phenyl group
by the methyl group leads to the decrease of Ip to 5.29 eV for 6b (Table 1).
Fig. 1. Absorption spectra (CH3CN, c ¼ 10ꢁ4 M) of 6a and 6b and starting compound 1

1404
V. Getautis et al.
Fig. 2. Photoemission (in air) spectra of the TMs
Table 1. Characteristics of 6a and 6b
Compound
ꢁ0=cm2 Vꢁ1 sꢁ1
ꢁ=cm2 Vꢁ1 sꢁ1
Ip=eV
6a
6b
10ꢁ7
6 ꢂ 10ꢁ8
4.4 ꢂ 10ꢁ6
4.6 ꢂ 10ꢁ6
5.37
5.29
Fig. 3. XTOF transients for 6a; insert shows one transient curve in linear plot

Hole Transporting Materials
1405
Fig. 4. Field dependencies of the hole drift mobilities of 6a and 6b
The hydrazones 6a and 6b are soluble in common organic solvents such as
acetone, chloroform, THF, dioxane, etc. Clear, transparent, and homogeneous films
were obtained using the casting technique. The hole drift mobility for 6a and 6b
was measured by the xerographic time of flight method (XTOF).
XTOF measurements revealed that small charge transport transients are
Gaussian with well-defined transit times on linear plots in all cases (Fig. 3).
Figure 4 shows the room temperature dependencies of the hole-drift mobility on
the electric field in the composition of 6a and 6b with PC. The mobility defining
parameters ꢁ0 and the mobility value at the 6.7ꢃ105 V=cm field strength are given in
Table 1. As seen from these results, the mobility values in amorphous films of
compositions 6a and 6b with PC exceed 10ꢁ6 cm2 Vꢁ1 sꢁ1 at an electric field of
106 V=cm. Due to the same ꢀ-electron conjugation as mentioned earlier there is a
small difference of mobility between the diphenyl substituted hydrazone 6a and the
methylphenylhydrazone 6b. It should be noted that the measured mobility of the
TM compositions with a binder is high enough for many practical applications and
it remains approximately in the same range as for the recently reported 1-phenyl-
1,2,3,4-tetrahydroquinoline-6-carboxaldehyde-1,10-diphenylhydrazone [17].
In conclusion, a novel family of hole transporting materials containing the 1-
phenyl-1,2,3,4-tetrahydroquinoline hydrazone moiety was synthesized and investi-
gated as potential new materials for electrophotography. These TMs exhibit high
hole drift mobilities and good compatibility with PC, and they possess the chemi-
cally active epoxy group, which enables them to be used as potential starting ma-
terials in the synthesis of various TM materials for optoelectronic devices.
Experimental
The 1H NMR spectra were taken on a Varian Unity Inova (300 MHz) spectrometer in CDCl3. The IR
spectra were taken for samples in KBr pellets on a Perkin Elmer Spectrum BX II FT-IR System

1406
V. Getautis et al.
spectrometer. The UV spectra were recorded on a Spectronic Genesys 8 spectrometer in THF (10ꢁ4 M)
in a microcell with an internal width of 1 mm. The course of the reactions was monitored by TLC on
Silufol UV-254 plates (eluent: acetone:n-hexane ¼ 7:18) and development with I2 or UV light. Silica
˚
gel (grade 62, 60–200 mesh, 150 A, Aldrich) was used for column chromatography. Elemental anal-
yses were performed with an Exeter Analytical CE-440 Elemental Analyzer; their results agreed
satisfactorily with the calculated values. The ionization potential was measured by the photoemission
in air method, similar to the one used in Ref. [21] and described in Ref. [18]. The samples for mobility
measurements were prepared from a 1:1 mass proportion compositions of 6a and 6b with polycarbo-
nate-Z (PC) (Iupilon Z-200 from Mitsubishi Gas Chemical Co.). The sample substrate was a polyester
film with conductive Al layer. The layer thickness was in the range of 7–11ꢁm. The hole drift mobility
was measured by xerographic time of flight technique [22–24]. Positive corona charging created elec-
tric field inside the TM layer. Charge carriers were generated at the layer surface by illumination with
pulses of a N2 laser (pulse duration 2 ns, wavelength 337 nm). The layer surface potential decrease as a
result of pulse illumination was up to 1–5% of the initial potential before illumination. The capacitance
probe that was connected to the wide frequency band electrometer measured the rate of the surface
potential decrease, dU=dt. The transit time tt was determined by the kink on the curve of the dU=dt
transient in linear scale. The drift mobility was calculated by the formula ꢁ ¼ d2=U0tt, where d is the
layer thickness and U0 is the surface potential at the moment of illumination.
3-Hydroxy-1-phenyl-1,2,3,4-tetrahydroquinoline (1)
To 169 g diphenylamine (1mol) 172 cm3 epichlorohydrin (2.2mol) were added in a 500 cm3 round
bottom flask with reflux condenser. The mixture was heated at 155–160ꢄC for 36–40h. After termina-
tion of the reaction unreacted epichlorohydrin was removed by distillation and obtained residue was
dissolved in 100 cm3 ethanol. The crystals formed upon standing at room temperature were filtered
off, washed with diethyl ether, and recrystallized from ethanol. Yield 140 g (62%); mp 78.0–79.0ꢄC
(Ref. [25] 78.5–79.0ꢄC); 1H NMR (CDCl3, 300 MHz): ꢂ ¼ 7.41–6.66 (m, 9H, Ar), 4.34–4.25 (m, CH),
3.77–3.46 (m, NCH2), 3.13 (dd, 1H, JAB ¼ 16.5Hz, JAX ¼ 4.4 Hz, HA of CH2CH), 2.86 (dd, 1H,
JAB ¼ 16.5Hz, JBX ¼ 4.6 Hz, HB of CH2CH), 2.44–2.23 (m, OH) ppm.
3-Acetyl-1-phenyl-1,2,3,4-tetrahydroquinoline (2)
Compound 1 (35 g, 0.2mol) was dissolved in 150 cm3 acetic anhydride and the mixture was heated
at 100ꢄC for 3 h. At the end of the reaction acetic anhydride was removed. The residue was dissolved
in methanol by heating and crystals formed upon standing at room temperature. The crystalline prod-
uct was filtered off, washed with methanol, and recrystallized from methanol. Yield 40 g (97%);
mp 64–65ꢄC (Ref. [25] 64.1–64.7ꢄC); IR (KBr): ꢃꢀ¼ 3053, 3029, 3007 (CHarom), 2949, 2936, 2913,
2875, 2825 (CHaliph), 1723 (C¼O), 1604, 1594, 1574, 1493 (C¼C, C–N), 772, 756, 704 (CH¼CH of
1
mono- and disubstituted benzenes) cmꢁ1; H NMR (CDCl3, 300 MHz): ꢂ ¼ 7.37–6.71 (m, 9H, Ar),
5.35–5.25 (m, CH), 3.81–3.66 (m, NCH2), 3.18 (dd, 1H, JAB ¼ 16.6Hz, JAX ¼ 4.4 Hz, HA of CH2CH),
2.94 (dd, 1H, JAB ¼ 16.6 Hz, JBX ¼ 5.8 Hz, HB of CH2CH), 1.95 (s, CH3) ppm.
3-Acetyl-1-phenyl-1,2,3,4-tetrahydroquinoline-6-carbaldehyde (3, C18H17NO3)
To a 250 cm3 3-neck round bottom flask equipped with thermometer, magnetical stirrer, and addition
funnel 44cm3 DMF (0.6mol) were added. The content was cooled in a salt=ice bath. 21 cm3 POCl3
(0.2mol) were slowly added to the mixture. During the addition of POCl3, the temperature of the
mixture was not allowed to rise above 5ꢄC. After the addition was completed, the reaction mixture was
allowed to warm to room temperature. A solution of 30g 2 (0.1mol) in 50 cm3 DMF was added to the
mixture and the mixture was heated to 90ꢄC for 1 h. The hot reaction mixture was poured into a
500 cm3 beaker containing 200 g ice. The mixture was neutralized by adding 40% NaOH solution and
allowed to stand at 5ꢄC for 24h. The precipitate was isolated by decanting, dissolved in ethyl acetate,
and washed with H2O until neutral, dried (MgSO4), and the solvent was removed. The residue was
dissolved in methanol and crystals formed upon standing at room temperature. The crystalline product

Hole Transporting Materials
1407
was filtered off, washed with methanol, cooled to ꢁ5ꢄC, and recrystallized from methanol. Yield 20 g
(59%); mp 89–90.5ꢄC; IR (KBr): ꢃꢀ¼ 3065, 3051 (CHarom), 2982, 2915, 2839, 2748 (CHaliph), 1728
1
(C¼O), 1664 (CHO) cmꢁ1; H NMR (CDCl3, 300MHz): ꢂ ¼ 9.71 (s, CHO), 7.63–7.20 (m, 7H, Ar),
6.59 (d, 1H, J ¼ 8.6 Hz, 8-H of Ht), 5.43–5.35 (m, CH), 3.89–3.71 (m, NCH2), 3.23 (dd, 1H,
JAB ¼ 16.6Hz, JAX ¼ 4.3 Hz, HA of CH2CH), 3.05 (dd, 1H, JAB ¼ 16.6Hz, JBX ¼ 4.9 Hz, HB of
CH2CH), 2.04 (s, CH3) ppm.
3-Acetyl-1-phenyl-1,2,3,4-tetrahydroquinoline-6-carbaldehyde N,N-diphenylhydrazone
(4a, C30H27N3O2)
To a solution of 5 g 3 (17 mmol) in 9 cm3 THF 6 g N,N-diphenylhydrazine hydrochloride (25 mmol)
dissolved in 33 cm3 methanol were added. The mixture was stirred at room temperature for 2 h. The
crystalline product formed during the reaction was filtered off, washed with 2-propanol, and recrys-
tallized from ethyl acetate:methanol ¼ 1:1. Yield 6 g (77%); mp 162–164.5ꢄC; IR (KBr): ꢃꢀ¼ 3032
(CHarom), 2961, 2937, 2866 (CHaliph), 1732 (C¼O) cmꢁ1; 1H NMR (CDCl3, 300 MHz): ꢂ ¼ 7.44–7.06
(m, 18H, Ar, CH¼N), 6.73 (d, 1H, J ¼ 8.6 Hz, 8-H of Ht), 5.35–5.26 (m, CH), 3.83–3.68 (m, NCH2),
3.18 (dd, 1H, JAB ¼ 16.7Hz, JAX ¼ 4.8 Hz, HA of CH2CH), 2.96 (dd, 1H, JAB ¼ 16.7Hz, JBX ¼ 5.4 Hz,
HB of CH2CH), 1.96 (s, CH3) ppm.
3-Acetyl-1-phenyl-1,2,3,4-tetrahydroquinoline-6-carbaldehyde N-phenyl-N-methylhydrazone
(4b, C25H25N3O2)
Compound 4b was prepared according to the procedure described above for 4a except that 20 g 3
(0.07 mol), 10cm3 N-phenyl-N-methylhydrazine (0.08 mol) and 100cm3 methanol instead of THF were
used. The reaction mixturewas stored over night at room temperature. Yield 24g (89%); mp 158–160ꢄC;
1H NMR (CDCl3, 300 MHz): ꢂ ¼ 7.47–6.86 (m, 13H, Ar, CH¼N), 6.78 (d, 1H, J ¼ 8.5 Hz, 8-H of Ht),
5.33–5.29 (m, CH), 3.85–3.69 (m, NCH2), 3.38 (s, NCH3), 3.22 (dd, 1H, JAB ¼ 16.4Hz, JAX ¼ 5.0 Hz,
HA of CH2CH), 3.01 (dd, 1H, JAB ¼ 16.4Hz, JBX ¼ 5.4 Hz, HB of CH2CH), 1.97 (s, CH3) ppm.
3-Hydroxy-1-phenyl-1,2,3,4-tetrahydroquinoline-6-carbaldehyde N,N-diphenylhydrazone
(5a, C28H25N3O).
To a solution of 24 g 4a (0.05 mol) in 30 cm3 dioxane 3.4 g KOH (0.05 mol) dissolved in 10cm3 H2O
were added. The mixture was refluxed for 3 h. Dioxane was removed and the residue was extracted
with ethyl acetate and washed with H2O until neutral. The organic layer was dried (MgSO4), filtered
off, and ethyl acetate was removed. The residue was purified by column chromatography (eluent:
acetone:n-hexane¼ 1:7). Yield 16 g (73%); IR (KBr): ꢃꢀ¼ 3374 (OH), 3057, 3033 (CHarom), 2920,
2850 (CHaliph), 1590, 1493 (C¼C, C–N) cmꢁ1; 1H NMR (CDCl3, 300 MHz): ꢂ ¼ 7.44–7.06 (m, 18H,
Ar, CH¼N), 6.67 (d, 1H, J ¼ 8.6 Hz, 8-H of Ht), 4.38–4.26 (m, CH), 3.77–3.52 (m, NCH2), 3.14 (dd,
1H, JAB ¼ 16.3 Hz, JAX ¼ 4.3 Hz, HA of CH2CH), 2.96 (dd, 1H, JAB ¼ 16.3Hz, JBX ¼ 5.8 Hz, HB of
CH2CH), 2.79 (d, J ¼ 5.5 Hz, OH) ppm.
3-Hydroxy-1-phenyl-1,2,3,4-tetrahydroquinoline-6-carbaldehyde N-phenyl-N-methylhydrazone
(5b, C23H23N3O)
To a solution of 24 g 4b (0.06 mol) in 100 cm3 THF 4 g KOH (0.06 mol) dissolved in 15 cm3 H2O
were added and heated to reflux. The same amount of KOH=H2O was added after 1, 4, and 8 h.
After these additions the mixture was refluxed for another 11 h. Then the reaction mixture was
diluted with ethyl acetate and crystals formed upon standing at room temperature. The crystalline
product was filtered off, washed with 2-propanol, and recrystallized from ethyl acetate. Yield 14 g
1
(65%); mp 149–151ꢄC; H NMR (CDCl3, 300 MHz): ꢂ ¼ 7.49–6.83 (m, 13H, Ar, CH¼N), 6.71
(d, 1H, J ¼ 8.8 Hz, 8-H of Ht), 4.42–4.29 (m, CH), 3.77–3.55 (m, NCH2), 3.37 (s, CH3), 3.19 (dd,
1H, JAB ¼ 16.4 Hz, JAX ¼ 4.5 Hz, HA of CH2CH), 2.93 (dd, 1H, JAB ¼ 16.4 Hz, JBX ¼ 4.9 Hz, HB of
CH2CH), 2.11 (d, J ¼ 7.0 Hz, OH) ppm.

1408
V. Getautis et al.
3-Oxiranylmethoxy-1-phenyl-1,2,3,4-tetrahydroquinoline-6-carboxaldehyde
N,N-diphenylhydrazone (6a, C31H29N3O2)
A mixture of 13 g 5a (0.03 mol) and 36 cm3 epichlorohydrin (0.47 mol) was stirred vigorously for 3 h
at 35–40ꢄC. Then 6.1g 85% powdered KOH (0.09 mol) and 1.6 g anhydrous Na2SO4 (0.01 mol) were
added in 6 equal portions every h with prior cooling of the reaction mixture to 30ꢄC. Then the reaction
mixturewas extracted with ethyl acetate. The organic layer was dried (MgSO4) and filtered. Ethyl acetate
and excess of epichlorohydrin were removed and the residue was purified by column chromatography
(eluent: ethyl acetate:n-hexane ¼ 1:7) to obtain 6a. Two months later the product crystallized. Yield 4 g
(30%); mp 126–128ꢄC; 1H NMR (CDCl3, 300 MHz): ꢂ ¼ 7.45–7.05 (m, 18H, Ar, CH¼N), 6.69, 6.70
(2d, 1H, J ¼ 2.4 Hz, diasteromeric 8-H of Ht), 4.08–3.97 (m, NCH2CH), 3.88–3.40 (m, 4H, NCH2,
OCH2), 3.20–3.07 (m, CH2CHO), 2.98–2.84 (m, CH from epoxy gr), 2.80–2.73 (m, HA from CH2CH
of epoxy gr), 2.59 (dd, 0.5H, JAB ¼ 5.0 Hz, JBX ¼ 2.8 Hz, HB of one diasteromer of CH2CH from epoxy
0
0
0
gr), 2.54(dd, 0.5H, JAB ¼ 5.2 Hz, JB X ¼ 2.6 Hz, HB ofotherdiasteromerofCH2CHfrom epoxygr)ppm.
3-Oxiranylmethoxy-1-phenyl-1,2,3,4-tetrahydroquinoline-6-carboxaldehyde N-phenyl-N-
methylhydrazone (6b, C26H27N3O2)
Compound 6b was prepared according to the procedure described for 6a except that 11g 5b (0.03 mol),
36cm3 epichlorohydrin (0.05 mol), 6.1 g powdered 85% KOH (0.09 mol), and 1.6 g Na2SO4 (0.01 mol)
were used. The reaction time was 26 h. The product was crystallized from ethyl acetate:methanol¼ 2:1.
The crystals were filtered off, washed with 2-propanol, and recrystallized from ethyl acetate:
methanol¼ 2:1. Yield 9 g (71%); mp 92–94ꢄC; 1H NMR (CDCl3, 300 MHz): ꢂ ¼ 7.48–6.85 (m, 13H,
Ar, CH¼N), 6.77, 6.76 (2d, 1H, J ¼ 2.3Hz, diasteromeric 8-H of Ht), 4.10–3.96 (m, NCH2CH), 3.86–
3.41 (m, 4H, NCH2, OCH2), 3.36 (s, CH3), 3.26–2.87 (m, OCHCH2), 2.99–2.89 (m, 1H, CH of epoxy
gr), 2.79–2.73 (dd, 1H, HA of CH2CH from epoxy gr), 2.60 (dd, 0.5H, JAB ¼ 4.9 Hz, JBX ¼ 3.0 Hz, HB of
0
0
one diastereomer of CH2CH from epoxy gr), 2.54 (dd, 0.5H, JAB ¼ 4.9 Hz, JB X ¼ 2.9 Hz, HB of other
diastereomer of CH2CH from epoxy gr) ppm.
Acknowledgements
Financial support of this research by the Lithuanian Science and Studies Foundation (B-18=2005) are
gratefully acknowledged.
References
[1] Kokwaro GO, Taylor G (1990) Drug Chem Toxicol 13: 347
[2] Francis CL, Ward AD (1994) Aust J Chem 47: 2109
[3] Omura S, Nakagawa A (1981) Tetrahedron Lett 22: 2199
[4] Tsushima K, Osumi T, Matsuo N, Itaya N (1989) Agric Biol Chem 53: 2529
[5] Meier HR, Evans S (1988) Eur Pat EP 273, 868; (1989) Chem Abstr 110: 98598p
[6] Shikhaliev KhS, Shmyreva Zh, Gurova EM (1989) Izv Vyssh Uchebn Zaved, Khim Khim
Technol 32: 85; (1990) Chem Abstr 112: 216659a
[7] Hahn E, Kraeh C, Mayer U (1993) Ger Pat DE 4, 215, 391; (1994) Chem Abstr 120: 301123f
[8] Rechardt C, Harms K, Kinzel M, Schafer G, Stein J, Wocadlo S (1995) Liebigs Ann: 317
[9] Lau PTS (1990) Eur Pat EP 385, 271; (1991) Chem Abstr 114: 122075w
[10] Yamaoka T, Koseki K, Suga S, Mitekura H, Yasui S (1994) Jpn Pat JP 6, 107, 719; (1994) Chem
Abstr 121: 180456b
[11] Hioki T, Tomioka (1989) Jpn Pat JP 01, 157, 944; (1990) Chem Abstr 112: 14344 h
[12] Sugiuchi M, Nishizawa H (1993) J Imag Sci Techn 37: 245
[13] Borsenberger PM, Weiss DS (1993) In: Borsenberger PM, Weiss DS (eds) Organic Photo-
receptors for Imaging Systems. Marcel Dekker, New York, p 447

Hole Transporting Materials
1409
[14] Mort J, Pfister G (1982) In: Mort J, Pfister G (eds) Electronic Properties of Polymers. Wiley, New
York, p 565
[15] Kim SH, Han SK, Kim JJ, Hwang SH, Yoon CM, Keum SR (1998) Dyes and Pigments 39: 77
[16] Hwang SH, Kim NK, Koh KN, Kim SH (1998) Dyes Pigments 39: 359
[17] Kanemitsu Y (1993) Electrophotography 32: 60
[18] Getautis V, Paliulis O, Paulauskaite I, Gaidelis V, Jankauskas V, Sidaravicius J, Tokarski Z, Law
K, Jubran N (2004) J Imag Sci Tech 48: 265
[19] Getautis V, Daskeviciene M, Gaidelis V, Jankauskas V (2005) J Photochem Photobiol A 175: 39
[20] Getautis V, Grazulevicius JV, Malinauskas T, Jankauskas V, Tokarski Z, Jubran NL (2004) Chem
Lett 33: 1336
[21] Miyamoto E, Yamaguchi Y, Yokoyama M (1989) Electrophotography 28: 364
[22] Montrimas E, Gaidelis V, Pazera A (1966) Lith J Phys 6: 569
[23] Vaezi-Nejad SM (1987) Int J Electron 62: 361
[24] Archie Y, Chan C, Juhasz C (1987) Int J Electron 62: 625
[25] Vorozhtsov NN, Kutkevichus SI (1965) Chem Heterocycl Comp 3: 374