Synthesis, film-forming properties, and thermal and light sensitivity of N,N′-bis[4-hydroxy(alkoxy, acyloxy)-3-alkoxyphenylmethylidene]benzene-1,4- diamines

Article abstract of DOI:10.1134/s1070363208020175

Previously unknown E,E-isomeric Schiff bases were synthesized by reaction of p-phenylenediamine with 4-hydroxy-3-methoxybenzaldehyde, 3-ethoxy-4- hydroxybenzaldehyde, and their O-alkyl and O-acyl derivatives in anhydrous methanol. Film-forming properties

Full text of DOI:10.1134/s1070363208020175

ISSN 1070-3632, Russian Journal of General Chemistry, 2008, Vol. 78, No. 2, pp. 281 285.
Original Russian Text E.A. Dikusar, N.G. Kozlov, V.I. Potkin, V.A. Azarko, A.P. Yuvchenko, 2008, published in Zhurnal Obshchei Khimii, 2008,
Vol. 78, No. 2, pp. 303 307.
Pleiades Publishing, Ltd., 2008.
Synthesis, Film-Forming Properties, and Thermal
and Light Sensitivity of N,N -Bis[4-hydroxy(alkoxy, acyloxy)-
3-alkoxyphenylmethylidene]benzene-1,4-diamines
E. A. Dikusara, b, N. G. Kozlova, b, V. I. Potkina, V. A. Azarkob, and A. P. Yuvchenkob
a Institute of Physical Organic Chemistry, National Academy of Sciences of Belarus,
ul. Surganova 13, Minsk, 220072 Belarus
e-mail: evgen_58@mail.ru
b Institute of New Materials Chemistry, National Academy of Sciences of Belarus, Minsk, Belarus
Received June 5, 2007
Abstract Previously unknown E,E-isomeric Schiff bases were synthesized by reaction of p-phenylenedi-
amine with 4-hydroxy-3-methoxybenzaldehyde, 3-ethoxy-4-hydroxybenzaldehyde, and their O-alkyl and
O-acyl derivatives in anhydrous methanol. Film-forming properties and thermal and light sensitivity of the
products were studied.
DOI: 10.1134/S1070363208020175
We previously studied film-forming properties and
light sensitivity of aromatic Schiff bases which were
synthesized from vanillin derivatives and chrysen-2-
amine and biphenyl-4-amine [1, 2]. The present
communication reports on the synthesis, physical and
film-forming properties, and thermal and light sens-
itivity of new Schiff bases containing two azomethine
moieties. These compounds were prepared by con-
densation of 4-hydroxy-3-methoxybenzaldehyde,
3-ethoxy-4-hydroxybenzaldehyde, and their O-alkyl
and O-acyl derivatives with p-phenylenediamine in
boiling anhydrous methanol. Previously unknown
(E,E)-N,N -bis[4-hydroxy(alkoxy, acyloxy)-3-alkoxy-
phenylmethylidene]benzene-1,4-diamines
IIIa IIIz
and IVa III were isolated in 84 91% yields. The
reactions were complete in 0.5 h and required no
catalyst, so that labile ester groups in the initial
aldehydes remained intact.
N=CH
OR
HC=N
NH2
H2N
CHO
II
OR
RO
RO
OR
OR
I
IIIa IIIz, IVa IV
III, R = Me, R = H (a), Me (b), MeC(O) (c), EtC(O) (d), PrC(O) (e), Me2CHC(O) (f), Me(CH2)6C(O) (g), Me(CH2)7C(O)
(h), Me(CH2)8C(O) (i), Me(CH2)16C(O) (j), H2C=C(Me)C(O) (k), cyclo-C6H11C(O) (l), C6H5CH2C(O) (m), C6H5(CH2)2
C(O) (n), C6H5CH(Me)CH2C(O) (o), (Z)-C6H5CH=C(CN)C(O) (p), C6H5C(O) (q), 4-ClC6H4C(O) (r), 2,4-Cl2C6H3C(O)
(s), 2,4-Cl2C6H3OCH2C(O) (t), 4-BrC6H4C(O) (u), 3-O2NC6H4C(O) (v), 3,5-(O2N)2C6H3C(O) (w), MeOC(O) (x),
EtOC(O) (y), MeOC(O)(CH2)2C(O) (z); IV, R = Et, R = H (a), Me (b), MeC(O) (c), EtC(O) (d), PrC(O) (e), Me2CHC(O)
(f), Me2CHCH2C(O) (g), Me(CH2)4C(O) (h), Me(CH2)5C(O) (i), Me(CH2)6C(O) (j), Me(CH2)7C(O) (k), Me(CH2)8C(O)
(l), Me(CH2)11C(O) (m), Me(CH2)16C(O) (n), cyclo-C6H11C(O) (o), C6H5(CH2)2C(O) (p), C6H5CH(Me)CH2C(O) (q),
trans-C6H5CH=CHC(O) (r), (Z)-C6H5CH=C(CN)C(O) (s), 4-MeC6H4C(O) (t), 2,4-Cl2C6H3C(O) (u), 2,4-Cl2C6H3OCH2
C(O) (v), 3-O2NC6H4C(O) (w), 4-O2NC6H4C(O) (x), 3,5-(O2N)2C6H3C(O) (y), MeOC(O) (z), EtOC(O) ( ), MeOC(O)
(CH2)2C(O) ( ).
281

282
DIKUSAR et al.
Schiff bases IIIa IIIz and IVa III are colored
The IR spectra of Schiff bases IIIa IIIz and
IVa III contained absorption bands in the regions
3100 3000 and 870 720 (C Harom), 2990 2840 (C
Haliph), 1770 1740 (C=O; IIIc IIIz, IVc IV ), 1625
1620 (C=N), 1600 1370 (C Carom), and 1280
(mostly yellow) crystalline substances that are soluble
in benzene, chloroform, and acetone and insoluble in
methanol, ethanol, and hexane. Compounds III and
IV required no additional purification, for they con-
tained no impurities of initial compounds. Their struc-
ture was confirmed by elemental analysis, molecular
weight determination by cryoscopy (see table), and
1
1000 cm (C O). The cyano group in molecules IIIp
1
and IVs gave rise to absorption at 2225 2224 cm ,
and compounds IIIv, IIIw and IVv IVy character-
1
IR, UV, and H NMR spectroscopy. According to the
istically showed in the IR spectra absorption bands in
1H NMR data, Schiff bases III and IV were isolated
as individual E,E isomers [3] with a purity of 97 1%.
the regions 1541 1525 and 1349 1343 cm due to
1
stretching vibrations of the nitro groups. The follow-
Yields, melting points, elemental analyses, and molecular weights of Schiff bases IIIa IIIz and IVa IV
Found, %
H
Calculated, %
H
M
Comp. Yield,
mp,
C
Formula
no.
%
C
N
C
N
found calculated
IIIa
89
91
90
90
90
91
84
90
91
90
86
89
91
90
90
91
86
90
90
88
91
90
90
89
89
90
88
91
85
90
91
90
89
87
89
90
189 190
175 176
206 207
134 135
133 134
148 149
111 112
97 98
70.36 5.48 7.21 C22H20N2O4
71.42 6.10 6.82 C24H24N2O4
68.03 5.32 5.78 C26H24N2O6
69.12 5.93 5.50 C28H28N2O6
70.01 6.38 5.05 C30H32N2O6
70.08 6.32 5.05 C30H32N2O6
72.73 7.84 4.12 C38H48N2O6
73.29 8.11 3.95 C40H52N2O6
73.88 8.32 3.87 C42H56N2O6
76.90 9.84 2.83 C58H88N2O6
70.57 5.52 5.39 C30H28N2O6
72.69 6.86 4.35 C36H40N2O6
74.65 5.41 4.30 C38H32N2O6
75.16 5.78 4.05 C40H36N2O6
75.87 6.21 3.90 C42H40N2O6
73.62 4.43 7.87 C42H30N4O6
74.17 4.98 4.55 C36H28N2O6
66.36 4.19 4.06 C36H26Cl2N2O6
60.04 3.42 3.57 C36H24Cl4N2O6
58.49 3.76 3.23 C38H28Cl4N2O8
58.44 3.64 3.52 C36H26Br2N2O6
64.18 4.02 8.04 C36H26N4O10
56.73 3.29 10.67 C36H24N6O14
63.72 5.05 5.36 C26H24N2O8
64.80 5.62 5.11 C28H28N2O8
63.83 5.45 4.40 C32H32N2O10
71.42 6.09 6.76 C24H24N2O4
72.41 6.63 6.20 C26H28N2O4
68.99 5.85 5.57 C28H28N2O6
69.94 6.24 5.24 C30H32N2O6
70.75 6.70 4.83 C32H36N2O6
70.73 6.75 4.87 C32H36N2O6
71.64 7.21 4.60 C34H40N2O6
72.00 7.46 4.17 C36H44N2O6
72.67 7.84 4.16 C38H48N2O6
73.47 8.13 3.95 C40H52N2O6
70.20
71.27
67.82
68.84
69.75
69.75
72.58
73.14
73.65
76.61
70.30
72.46
74.50
74.98
75.43
73.46
73.96
66.16
59.85
58.33
58.24
64.09
56.55
63.41
64.61
63.57
71.27
72.20
68.84
69.75
70.57
70.57
71.31
71.79
72.58
73.14
5.36
5.98
5.25
5.78
6.24
6.24
7.69
7.98
8.24
9.75
5.51
6.76
5.26
5.66
6.03
4.40
4.83
4.01
3.35
3.61
3.53
3.88
7.44
6.93
6.08
5.73
5.42
5.42
4.46
4.26
4.09
3.08
5.47
4.69
4.57
4.37
4.19
8.16
4.79
4.29
3.88
3.58
3.77
8.30
368.7
397.1
445.4
460.9
500.6
502.2
617.7
638.2
661.9
880.6
498.2
580.8
587.5
449.0
651.7
658.4
562.9
634.7
703.6
760.0
725.3
655.2
755.8
481.7
503.0
584.3
390.2
416.8
467.5
498.4
528.1
530.4
558.6
581.9
610.3
637.0
376.4
404.5
460.5
488.5
516.6
516.6
628.8
656.9
684.9
909.3
512.6
596.7
612.7
460.7
668.8
686.7
584.6
653.5
722.4
782.5
742.4
674.6
764.6
492.5
520.5
604.6
404.5
432.5
488.5
516.6
544.6
544.6
572.7
600.8
628.8
656.9
IIIb
IIIc
IIId
IIIe
IIIf
IIIg
IIIh
IIIi
92 93
80 81
IIIj
IIIk
IIIl
174 174
157 158
183 184
158 159
161 162
242 243
229 230
232 233
215 216
155 156
228 229
210 211
267 268
214 215
174 175
135 136
65 66
182 183
195 196
170 171
152 153
168 169
137 138
132 133
126 127
122 123
IIIm
IIIn
IIIo
IIIp
IIIq
IIIra
IIIsb
IIItc
IIIud
IIIv
IIIw
IIIx
IIIy
IIIz
IVa
IVb
IVc
IVd
IVe
IVf
3.16 10.99
4.91
5.42
5.33
5.98
6.52
5.78
6.24
6.66
6.66
7.04
7.38
7.69
7.98
5.69
5.38
4.63
6.93
6.48
5.73
5.42
5.14
5.14
4.89
4.66
4.46
4.26
IVg
IVh
IVi
IVj
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 2 2008

SYNTHESIS, FILM-FORMING PROPERTIES, AND THERMAL AND LIGHT SENSITIVITY
283
Table (Contd.)
Found, %
H
Calculated, %
H
M
Comp. Yield,
mp,
C
Formula
no.
%
C
N
C
N
found calculated
IVk
IVl
90
90
87
90
89
89
90
88
90
89
89
88
90
90
88
91
90
90
96 97
85 86
92 93
73 74
73.91 8.29 3.88 C42H56N2O6
74.36 8.58 3.85 C44H60N2O6
72.85 8.89 3.06 C50H72N2O6
77.03 10.02 2.77 C60H92N2O6
73.24 7.19 4.13 C38H44N2O6
75.68 6.23 3.96 C42H40N2O6
75.97 6.51 3.77 C44H44N2O6
76.14 5.58 3.96 C42H36N2O6
74.20 4.92 7.57 C44H34N4O6
75.22 5.81 4.09 C40H36N2O6
60.97 3.78 3.56 C38H28Cl4N2O6
58.56 4.13 3.20 C40H32Cl4N2O8
65.20 4.44 7.81 C38H30N4O10
65.15 4.38 7.86 C38H30N4O10
75.86 3.63 10.22 C38H28N6O14
64.69 5.50 5.05 C28H28N2O8
65.72 5.97 4.88 C30H32N2O8
64.76 5.85 4.14 C34H36N2O10
73.65
74.12
72.61
76.88
73.05
75.43
75.84
75.89
73.94
74.98
60.82
59.28
64.95
64.95
75.58
64.61
65.58
64.55
8.24
8.48
8.77
9.89
7.10
6.03
6.36
5.46
4.79
5.66
3.76
3.98
4.30
4.30
4.09
3.93
3.39
2.99
4.48
4.19
4.02
4.21
7.84
4.37
3.73
3.46
7.97
7.97
671.7
697.2
804.4
917.5
613.8
645.3
680.2
643.7
694.6
447.0
737.1
786.3
679.4
682.5
770.5
503.7
527.9
618.8
682.9
713.0
827.1
937.4
624.8
668.8
696.8
664.8
714.8
460.7
750.5
810.5
702.7
702.7
792.7
520.5
548.6
632.7
IVm
IVn
IVo
IVp
IVq
IVr
IVs
IVt
176 177
143 144
191 192
193 194
248 249
198 199
210 211
176 177
240 241
265 266
303 304
202 203
193 194
148 149
IVue
IVvf
IVw
IVx
IVy
IVz
IV
3.56 10.60
5.42
5.88
5.74
5.38
5.11
4.43
IV
a
b
c
Found Cl, %: 10.60. Calculated Cl, %: 10.85. Found Cl, %: 19.26. Calculated Cl, %: 19.63. Found Cl, %: 17.88. Calculated Cl,
d
e
f
%: 18.12. Found Br, %: 21.32. Calculated Br, %: 21.53. Found Cl, %: 18.65. Calculated Cl, %: 18.90. Found Cl, %: 17.18.
Calculated Cl, %: 17.50.
ing absorption maxima were observed in the UV spec-
tra of IIIa IIIz and IVa III , max, nm (log ): 209
(4.48), 221 (3.38), 273 (4.20), 354 (3.38).
of all bond lengths and bond and dihedral angles
using GAMESS program [5]. The following Hf
1
values were obtained (kcal mol ): E,E isomers: 48.8
(IIIq), 132.5 (IVc); E,Z isomers: 46.6 (IIIq),
131.7 (IVc); Z,Z isomers: 46.2 (IIIq), 128.4 (IVc).
Thus, the E,E configuration is more stable than E,Z
1
In the H NMR spectra of Schiff bases IIIa IIIz
and IVb, protons in the methoxy group resonated as
a singlet at 3.85 3.92 ppm; ethoxy group in IVa
IV gave a triplet at 1.35 1.70 ppm (Me) and a
quartet at 4.00 4.40 ppm (CH2). Aromatic proton
signals were located in the region 7.00 7.80 ppm,
and the azomethine HC=N proton resonated as a
singlet at 8.40 8.50 ppm; the position of the latter
signal is typical of E isomers of Schiff bases [3].
1
1
(by 0.8 2.2 kcalmol ) and Z,Z (by 2.6 4.1 kcal mol ).
The calculated energy barriers to the transformations
of one isomer into another were estimated at 8
1
12 kcal mol . Thus Schiff bases III and IV attract
interest as potential heat-sensitive molecular switches
[6].
Some relatively high-melting Schiff bases (mp
>100 C, see table) showed thermochromic effect [4]
arising from reversible transformation of E,E isomer
into less thermodynamically stable Z,Z isomer prior
to melting. This process was accompanied by change
of the crystal shape and reduction in the color intensity
just before melting. No thermochromic effect was ob-
served for low-melting Schiff bases IIIh IIIj, IVa,
and IVk IVn. In order to verify the nature of thermo-
chromic effect observed upon melting, we performed
semiempirical MNDO PM3 calculations of heats of
formation ( Hf) of the E,E, E,Z, and Z,Z isomers of
Schiff bases IIIq and IVc with complete optimization
By thermal vacuum evaporation (TVE) of 0.1-mmol
(0.038 0.094-g) samples of powdered Schiff bases
IIIa IIIz and IVa III we obtained mainly glossy
films with a thickness of 0.5 1.6 m, which had a pale
yellow or orange hue and exhibited a good adhesion
to various supports (monocrystalline silicon, quartz,
pyroceram, polymeric layers, etc.). In most cases,
samples evaporated completely or with a small residue
(0.1 0.3%). Exceptions were dinitro derivatives IIIw
and IVy; their evaporation was accompanied by de-
composition (up to 36%) and formation of a carbon
residue. Nevertheless, the IR spectra of the obtained
films were similar to those of the corresponding initial
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 2 2008

284
DIKUSAR et al.
OR
OR
H
N
N
H
H
N
N
OR
N
N
OR
OR
OR
H
OR
R O
H
H
OR
OR
OR
OR
E,E
E,Z
Z,Z
samples. The glossiness and transparency of films
prepared from all Schiff bases did not changed for a
long time (over a month).
procedure described in [1, 2, 8]; films were deposited
from the gas phase onto a silicon support for IR spec-
troscopy. The deposition process was controlled with
the aid of a quartz resonator, and film thickness was
measured using an MII-4 Linnick interferometer. The
IR spectra of the films deposited onto silicon supports
were recorded on a Protege-460 spectrometer.
The films turned out to be sensitive to UV light in
the range from 260 to 380 nm. Their exposure to
UV light through a photomask gave rise to a latent
image, and the subsequent vacuum evaporation at the
same temperature as for film deposition resulted in
formation of a negative relief pattern. The resolution
of films obtained by thermal vacuum evaporation of
the examined Schiff base was 1 to 3 m in optical
photolithography.
Initial esters I were synthesized according to the
procedures described in [9 12]. Benzene-1,4-diamine
(II) of analytical grade was used (purity 98%, mp
139 140 C).
(E,E)-N,N -Bis[4-hydroxy(alkoxy, acyloxy)-3-al-
koxyphenylmethylidene]benzene-1,4-diamines
IIIa IIIz and IVa III (general procedure). A solu-
tion of 5 mmol of the corresponding aldehyde I and
2.5 mmol of p-phenylenediamine (II) in 30 ml of an-
hydrous methanol was heated for 0.5 h under reflux.
The hot solution was filtered through a folded filter
paper, the filtrate was cooled and left to stand for
10 15 h at 5 C, and the precipitate was filtered off
through a glass filter, washed with a small amount of
methanol, and dried in air.
Using laser ablation lithography (energy exposure
up to 150 kJ cm ), a submicron relief pattern may be
3
generated in TVE films based on the prepared Schiff
bases. The films are resistant to atmospheric air and
visible light, and they can be used as yellow light
filters. They also may be interesting for nanotechno-
logy of organic light-emitting diodes as a buffer layer
preventing diffusion of oxygen atoms from transparent
anode (ITO film) and reducing the energy barrier to
hole injection [12].
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4
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