Some polyhydroxy azo-azomethine derivatives of salicylaldehyde: Synthesis, characterization, spectroscopic, molecular structure and antimicrobial activity studies

Article abstract of DOI:10.1016/j.molstruc.2006.11.025

Some new substituted polyhydroxy azo-azomethine compounds were prepared by reaction of tris(hydroxymethyl)aminomethane with (E)-2-hydroxy-5-(phenyldiazenyl) benzaldehyde and its substituted derivatives. The structures of azo and azo-azomethine compounds were determined by IR, UV-vis, ¹H NMR and ¹³C NMR spectroscopic techniques, and/or X-ray diffraction studies. According to IR spectra, all azo-azomethine compounds adopt keto form in solid state. UV-vis analysis has shown the presence of keto-enol tautomerism in solution for all azo-azomethine compounds, except that for nitro substituted derivative, enol form is dominantly favored in solution. At the same time, above mentioned derivative compounds were studied in vitro for their antimicrobial properties. Among the phenylazosalicylaldehyde series compound tested, 4-phenylazosalicylaldehyde, 4-(3-chlorophenylazo)salicylaldehyde, 4-(2-chlorophenylazo)salicylaldehyde, 4-(4-fluorophenylazo)salicylaldehyde, 4-(3-chlorophenylazo)salicylaldehyde and 4-(4-ethylphenylazo)salicylaldehyde showed a weak antimicrobial activity only against gram positive bacteria. On the contrary, phenylazosalicylaldehyde series compounds were reacted tris(hydroxmethyl)aminomethane, that exhibited a strong antimicrobial activity against gram positive bacteria, yeast and mould. Moreover, while the 2-{[1,3-dihydroxy-2-(hydroxymethyl)propan-2-ylimino]methyl}phenol did not show an inhibition on tested microorganism, the addition of phenyldiazine groups to 2-{[1,3-dihydroxy-2-(hydroxymethyl)propan-2-ylimino]methyl}phenol resulted in a strong increases in antimicrobial activity.

Full text of DOI:10.1016/j.molstruc.2006.11.025

Journal of Molecular Structure 840 (2007) 71–89
www.elsevier.com/locate/molstruc
Some polyhydroxy azo–azomethine derivatives
of salicylaldehyde: Synthesis, characterization, spectroscopic,
molecular structure and antimicrobial activity studies
a,
a
b
Mustafa Odabasog˘lu *, C¸ ig˘dem Albayrak , Resit Ozkanca ,
¨
ß
ß
b
c
Fatma Zehra Aykan , Peter Lonecke
a
Department of Chemistry, Faculty of Arts and Sciences, Ondokuz Mayıs University, 55139 Kurupelit – Samsun, Turkey
Department of Biology, Faculty of Arts and Sciences, Ondokuz Mayıs University, 55139 Kurupelit – Samsun, Turkey
b
c
Universitat Leipzig Faculta¨t fu¨r Chemie und Mineralogie, Leipzig, Germany
Received 9 September 2006; received in revised form 6 November 2006; accepted 10 November 2006
Available online 27 December 2006
Abstract
Some new substituted polyhydroxy azo–azomethine compounds were prepared by reaction of tris(hydroxymethyl)aminomethane
with (E)-2-hydroxy-5-(phenyldiazenyl) benzaldehyde and its substituted derivatives. The structures of azo and azo–azomethine com-
pounds were determined by IR, UV–vis, 1H NMR and 13C NMR spectroscopic techniques, and/or X-ray diffraction studies. According
to IR spectra, all azo–azomethine compounds adopt keto form in solid state. UV–vis analysis has shown the presence of keto–enol tau-
tomerism in solution for all azo–azomethine compounds, except that for nitro substituted derivative, enol form is dominantly favored in
solution. At the same time, above mentioned derivative compounds were studied in vitro for their antimicrobial properties. Among the
phenylazosalicylaldehyde series compound tested, 4-phenylazosalicylaldehyde, 4-(3-chlorophenylazo)salicylaldehyde, 4-(2-chloropheny-
lazo)salicylaldehyde, 4-(4-fluorophenylazo)salicylaldehyde, 4-(3-chlorophenylazo)salicylaldehyde and 4-(4-ethylphenylazo)salicylalde-
hyde showed a weak antimicrobial activity only against gram positive bacteria. On the contrary, phenylazosalicylaldehyde series
compounds were reacted tris(hydroxmethyl)aminomethane, that exhibited a strong antimicrobial activity against gram positive bacteria,
yeast and mould. Moreover, while the 2-{[1,3-dihydroxy-2-(hydroxymethyl)propan-2-ylimino]methyl}phenol did not show an inhibition
on tested microorganism, the addition of phenyldiazine groups to 2-{[1,3-dihydroxy-2-(hydroxymethyl)propan-2-ylimino]methyl}phenol
resulted in a strong increases in antimicrobial activity.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Azo–azomethine compounds; Azo dyes; X-ray; UV–vis; IR; NMR; Tautomerism
1. Introduction
[1–3]. There are about 3000 azo dyes currently in use all
over the world. The great majority of them are monoazo
compounds, which have the common structure unit of
the azo chromophore, AN@NA, linking two aromatic sys-
tems. The textile industry is the largest consumer of dye-
stuffs. Although some azo dyes have been reported to be
toxic, dozens of additional monoazo dyes are permitted
in drugs and cosmetics [4]. The pharmaceutical importance
of compounds including an arylazo group has been exten-
sively reported in the literature [5,6]. The oxidation–reduc-
tion behaviors of these compounds play an important role
in its biological activity [7].
Azo compounds are the oldest and largest class of indus-
trial synthesized organic dyes due to their versatile applica-
tion in various fields, such as dyeing textile fiber,
biomedical studies, advanced application in organic syn-
thesis and high technology areas such as laser, liquid crys-
talline displays, electro-optical devices and ink-jet printers
*
Corresponding author. Tel.: +90 362 457 6020x5196; fax: +90 362 457
6081.
E-mail address: muodabas@omu.edu.tr (M. Odabaßsog˘lu).
0022-2860/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2006.11.025

72
M. Odabaßsog˘lu et al. / Journal of Molecular Structure 840 (2007) 71–89
There is considerable interest in Schiff base ligands and
their complexes due to their antitumor activities [8].
Azomethine derivatives are widely applied in biological
systems and dyes [8,9]. In recent years, organic materials
with second-order nonlinear optical properties have been
extensively studied for use in photonic devices, such as high
X2
X1
X2
NaNO2 / HCl / 0-5 oC
N2]+ Cl-
NH2
CHO
X1
OH
2
1
OH
OH
3
CHO
OH
N
H2N
OH
OH
OH
OH
X2
X1
N
5
X2
X1
N
OH
N
N
-H2O
4a-n
6a-n
X1
H
X2
H
H
H
H
H
H
H
X1
4-I
X2
H
H
H
H
H
H
a
b
c
d
e
f
h
i
2-Me
2-Cl
3-Cl
4-F
4-Me
4-Et
4-Bun
4-NO2
4-Ac
2-Cl
j
k
l
m
n
4-Cl
4-Br
6-Cl
g
Scheme 1.
Table 1
Properties of 5-phenyldiazenylsalicylaldehydes 4 and their polyhydroxy azo–azomethine derivatives 6
Compound
Yield (%)
Mp (ꢁC)
% C
% H
% N
Calculated
Found
Calculated
Found
Calculated
Found
4a
6a
4b
6b
4c
6c
4d
6d
4e
6e
4f
96
88
82
79
85
72
91
79
87
85
83
87
74
87
85
85
80
86
90
85
89
85
87
84
70
82
65
48
128–130
169–172
113–115
191–193
151–153
206–209
139–141
182–184
168–171
200–202
211–213
241–243
216–218
252–254
219–223
227–229
151–154
212–214
123–126
190–193
96–98
–
–
–
5.78
–
–
–
4.99
–
4.99
–
5.19
–
4.99
–
4.44
–
3.99
–
6.12
–
6.49
–
7.06
–
4.85
–
5.66
–
–
–
5.85
–
–
–
5.03
–
5.03
–
5.05
–
4.94
–
3.87
–
3.98
–
6.17
–
6.62
–
7.01
–
4.35
–
5.37
–
–
–
–
62.01
–
–
–
56.13
–
56.13
–
58.79
–
56.13
–
50.02
–
44.85
–
62.97
–
63.85
–
65.44
–
54.54
–
61.95
–
–
–
56.38
–
56.45
–
58.33
–
55.80
–
49.53
–
44.53
–
62.23
–
64.37
–
64.95
–
54.16
–
12.77
–
–
–
11.55
–
11.55
–
12.10
–
11.55
–
10.29
–
9.23
–
12.24
–
11.76
–
10.90
–
14.97
–
12.58
–
–
–
11.76
–
11.73
–
11.46
–
11.17
–
9.80
–
8.37
–
11.90
–
11.89
–
10.53
–
13.55
–
6f
4g
6g
4h
6h
4i
6i
4j
6j
4k
6k
4l
182–184
195–198
266–268
176–179
233–235
165–167
156–158
6l
4m
6m
4n
6n
61.45
–
–
59.96
–
–
11.32
–
–
10.64
–
–

M. Odabaßsog˘lu et al. / Journal of Molecular Structure 840 (2007) 71–89
73
speed photonic switching, electro-optic modulators, com-
ponents of optical communication systems and others
[10–13]. o-Hydroxy Schiff bases exist as enol [14], keto
[15–20] or enol/keto mixtures [21]. N-Substituted o-
hydroxylimines have been reported to display thermochro-
mism and photochromism in the solid state by H-atom
transfer from the hydroxyl O-atom to the N-atom
[17,18]. The proton tautomerism plays an important role
in many fields of chemistry and especially biochemistry.
Which tautomeric structure is dominant under certain con-
ditions is important in terms of coloristic and technologi-
cal properties of dyes [12]. Azo–azomethines have been
extensively used as dyestuffs for wool, leather and synthetic
fabrics because of their extraordinary coloring properties
and in photonic devices, electrooptic modulators, compo-
nents of optical communication systems of their second-
order nonlinear optical properties [13,21–23].
Fig. 1. Electronic spectra of 4a (I) and 6a (II) in DMSO.
Fig. 2. Absorption spectra of 6a in ethanol C = 3.2 · 10ꢀ5 M (———)
and in DMF, C = 1.6 · 10ꢀ5 M (---------): (a) 0%; (b) 45% and (c) 60%
water.

74
M. Odabaßsog˘lu et al. / Journal of Molecular Structure 840 (2007) 71–89
O
H
O
H
N
H
N
N
N
N
OH
OH
N
OH
OH
H
OH
OH
enol-imine form
keto-amine form
Scheme 2.
sodium nitrite in the presence of hydrochloric acid, which
coupled with salicylaldehyde 3 to afford 5-phenyldiazenyl-
salicylaldehyde dyes 4 in good yields (Scheme 1 and Table
1). 5-Phenyldiazenylsalicylaldehydes 4 were purified by
recrystallization from suitable solvents. The reaction of 4
with tris(hydroxymethyl)aminomethane (5) then afforded
polyhydroxy azo–azomethine derivatives 6, which were
purified by recrystallization from suitable solvents and
their purity was analyzed by thin-layer chromatography
(Scheme 1 and Table 1).
2.2. UV–vis absorption spectra
Typical characteristic UV–vis absorption bands of
5-phenyldiazenylsalicylaldehydes 4 and their polyhydroxy
azo–azomethine derivatives 6 in DMSO are given in
Table 2.
Fig. 3. Dependence of electronic absorption spectra of 6l on temperature
in EtOH: (a) ꢀ15 ꢁC, (b) 50 ꢁC, (c) 60 ꢁC, (d) 68 ꢁC, (e) 70 ꢁC.
The difference between UV–vis spectra of azo and azo–
azomethine compounds is that p fi p* for azo group of
azo–azomethine compounds is more red shifted than relat-
ed azo compounds. This shift can be explained on the basis
of the intramolecular hydrogen bonding between C@N and
OH groups, which leaves a higher negative charge density
on the oxygen atom of OH group. Another difference is
p fi p* for keto form of azo–azomethine compounds since
hydrogen is transferred from phenol group to imine nitro-
gen. Typical characteristic UV–vis absorption spectrum in
DMSO for 5-phenyldiazenylsalicylaldehydes 4a and their
polyhydroxy azo–azomethine derivatives 6a are given in
Fig. 1.
The electronic spectra of 6a were recorded in both
DMF and EtOH between 200 and 600 nm (Fig. 2). These
solvents were selected in order to obtain a difference in
the position of tautomeric equilibrium (keto-amine M
enol-imine) (Scheme 2). The kmax values of 6a in DMF
and EtOH are 393 (with shoulder at about 430 nm)
and 339 nm, respectively. This tautomeric shift may be
inferred from (i) selective solvation and (ii) the ability
of the solvent to form stronger intermolecular H-bonds
with a particular tautomeric form [24]. The absorption
spectra of 6a at different volume ratios of the applied
pair of solvents DMF/water were also recorded. It was
observed that the absorption of the band at 393 nm
(probably enol-imine form) increased and shifted to
340 nm, while that of the other form (keto-amine at
340 nm) decreased with increasing of the volume content
Fig. 4. Dependence of electronic absorption spectra of 6l on temperature
in DMSO: (a) 30 ꢁC, (b) 50 ꢁC, (c) 70 ꢁC, (d) 80 ꢁC.
Our interest has been focused on preparation of some
polyhydroxy azo–azomethine derivatives with donor and
acceptor groups, and investigation of their spectroscopic
properties, molecular structure and antimicrobial activities.
2. Results and discussion
2.1. Synthesis
For synthesis of polyhydroxy azo–azomethine deriva-
tives 6, substituted anilines 1 were first diazotized using

M. Odabaßsog˘lu et al. / Journal of Molecular Structure 840 (2007) 71–89
75
Fig. 5. Dependence of electronic absorption spectra of 6l on temperature in DMF: (a) ꢀ10 ꢁC, (b) 90 ꢁC, (c) 96 ꢁC, (d) 98 ꢁC.
Table 3
Characteristic IR absorption bands of 5-phenyldiazenylsalicylaldehydes 4
and their polyhydroxy azo–azomethine derivatives 6
Compound OH
NHO
N@N C@O CAO(Aliphatic) CAO(Aromatic)
(cmꢀ1) (cmꢀ1) (cmꢀ1 (cmꢀ1
(cmꢀ1) (cmꢀ1
)
)
)
4a
6a
4b
6b
4c
6c
4d
6d
4e
6e
4f
3224
–
3421
–
3200
–
3213
–
3263
–
3200
–
–
1425 1668
3100–3400 1425 1635 1053
1420 1654
3100–3400 1419 1645 1056
1420 1670
3100–3400 1425 1651 1055
1411 1662
3100–3400 1413 1639 1051
1409 1670
3100–3400 1431 1645 1045
1425 1670
3100–3400 1427 1647 1059
1424 1668
3100–3400 1425 1645 1062
1425 1668
3100–3400 1425 1643 1058
1422 1655
3100–3400 1423 1660 1064
1423 1651
3100–3400 1425 1658 1062
1412 1666
3100–3400 1423 1660 1062
1420 1655
3100–3400 1419 1651 1058
–
1170–1150
–
1170–1150
–
1170–1150
–
1170–1150
–
1170–1150
–
1170–1150
–
1170–1150
–
1170–1150
–
1170–1150
–
1170–1150
–
1170–1150
–
1170–1150
–
1170–1150
–
–
–
–
–
–
–
–
–
–
6f
4g
6g
4h
6h
4i
3200
–
–
Fig. 6. IR spectra of 4e (I) and 6e (II).
3200
–
3200
–
3200
–
3200
–
–
–
–
–
6i
spectra of compound 6l at different temperatures. The
compound 6l shows two absorptions at room tempera-
ture in the range of 300–600 nm. One is 393 nm for
enol-imine form while other is 453 nm for keto-amine
form. When the solution of compound 6l was cooled
at ꢀ15 ꢁC, the color of solution was turned from orange
to yellow and the absorption band (453 nm) for keto
form was disappeared at the UV–vis spectra. When the
cold solution was heated, the absorption band for keto
form was appeared again. This implies that there is
enol–keto equilibrium and this equilibrium depends on
temperature. Phenol–imine tautomer is dominant at low
temperature in EtOH, while keto-amine tautomer is
dominant at high temperature. The phenol–imine tau-
tomerism in the spectrum of 6m is dominant as in the
spectrum of 6l in ethyl alcohol at low temperature, but
there is no significant changes at the equilibrium of other
azo–azomethines.
4j
–
–
6j
4k
6k
4l
–
–
3200
–
–
6l
4m
3200
–
–
1413 1678
1662
–
6m
3100–3400 1421 1670 1058
1643
–
4n
6n
3200
–
1421 1624
3100–3400 1421 1639 1047
–
1186
–
of water (Fig. 2). H2O leads to an increase of the H
form [24].
The UV–vis spectra of compounds 6l were studied at
different temperature in EtOH. Fig. 3 shows the UV

Table 4
1H NMR signals of 5-phenyldiazenylsalicylaldehydes 4
3
5
2
12 11
1
4
N
10
N
OH
R
6
7
14
9
8
CHO
13
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
H2
H3
H4
7.85063 (dd),
J2,3 = 8.032,
J2,4 = 1.98
–
–
7.82769 (t), 7.9201 (dd), 7.63014 (d), 7.7791
J2,6 = 2.152, J2,3 = 8.81, J2,3 = 8.76
J2,4 = 2.152 JHF = 5.27
7.62033 (d), 7.73889 (d), 7.75946 (d), 7.72988 (d), 7.98545 (d), 7.90989 (d), –
J2,3 = 8.262 J2,3 = 8.17 J2,3 = 8.17 J2,3 = 8.20 J2,3 = 9.016 J2,3 = 8.238
7.57259 (t),
J3,2 = 8.032, J3,4 = 7.56 J3,4 = 7.62,
J3,4 = 8.032 J3,5 = 2.1
7.43714 (d), 7.6450 (dd), –
7.4043 (dd), 7.86931 (d), 7.7791
J3,2 = 8.81, J3,2 = 8.76
JHF = 8.81
7.93655 (d), 7.34364 (d), 7.36687 (d), 7.30735 (d), 8.36811 (d), 8.15725 (d), 7.5972 (d),
J3,2 = 8.262 J3,2 = 8.17 J3,2 = 8.17 J3,2 = 8.20 J3,2 = 9.016 J3,2 = 8.238 J3,4 = 7.826
7.55635 (tt), 7.27547 (t), 7.45885 (td), 7.58851 (dt), –
J4,3 = 8.032, J4,3 = 7.56, J4,3 = 7.62, J4,5 = 7.562,
J4,5 = 8.032, J4,5 = 7.56 J4,5 = 7.62, J4,2 = 2.152,
–
–
–
–
–
–
–
–
7.3763 (t),
J4,3 = 7.826,
J4,5 = 7.826
J4,2 = 1.98,
J4,6 = 1.98
J4,6 = 1.68 J4,6 = 2.152
H5
H6
7.57259 (t),
7.34588 (t), 7.52832 (td), 7.61980 (t), 7.4043 (dd), 7.86931 (d), 7.7791
7.93655 (d), 7.34364 (d), 7.36687 (d), 7.30735 (d), 8.36811 (d), 8.15725 (d), 7.5972 (d),
J3,2 = 8.262 J3,2 = 8.17 J3,2 = 8.17 J3,2 = 8.20 J3,2 = 9.016 J3,2 = 8.238 J5,4 = 7.826
J5,6 = 8.032, J5,6 = 7.56, J5,6 = 7.72, J5,6 = 7.562, J5,6 = 8.81, J3,2 = 8.76
J5,4 = 8.032 J5,4 = 7.56 J5,4 = 7.62, J5,4 = 7.562 JHF = 8.81
J5,3 = 2.1
7.8563 (dd), 7.54181 (d), 7.68734
7.8388 (dt), 7.9201 (dd), 7.63014 (d), 7.7791
7.62033 (d), 7.73889 (d), 7.75946 (d), 7.72988 (d), 7.98545 (d), 7.90989 (d), –
J6,5 = 8.032, J6,5 = 7.56 (dd),
J6,5 = 7.152, J6,5 = 8.81, J2,3 = 8.76
J2,3 = 8.262 J2,3 = 8.17 J2,3 = 8.17 J2,3 = 8.20 J2,3 = 9.016 J2,3 = 8.238
J6,4 = 1.98
J6,5 = 7.72, J6,4 = 2.152, JHF = 5.27
J6,4 = 1.68 J6,2 = 2.152
H8
8.1726 (d),
8.16501 (d), 8.19225 (d), 8.18930 (d), 8.15715 (d), 8.17746 (d), 8.16715 (d),8.16848 (d), 8.12684 (d), 8.14570 (d), 8.13349 (d), 8.17885 (d), 8.17981 (d), 8.1789 (d),
J8,12 = 2.38
J8,12 = 2.504 J8,12 = 2.50 J8,12 = 2.50 J8,12 = 2.50 J8,12 = 2.54 J8,12 = 2.34 J8,12 = 2.52 J8,12 = 2.38 J8,12 = 2.242 J8,12 = 2.36 J8,12 = 2.522 J8,12 = 1.78 J8,12 = 2.51
H11
H12
7.1860 (d),
7.19261 (d), 7.2145 (d), 7.19125 (d), 7.18432 (d), 7.18521 (d), 7.1697 (d), 7.17759 (d), 7.16167 (d), 7.16900 (d), 7.15870 (d), 7.18925 (d), 7.18151 (d), 7.2219 (d),
J11,12 = 8.84 J11,12 = 8.81 J11,12 = 8.85 J11,12 = 8.84 J11,12 = 8.80 J11,12 = 8.83 J11,12 = 8.4 J11,12 = 8.886J11,12 = 8.77 J11,12 = 8.79 J11,12 = 8.84 J11,12 = 8.79 J11,12 = 8.70J11,12 = 8.83
8.0792 (dd), 8.07806
J12,11 = 8.84, (dd),
8.088 (dd), 8.09522
8.06368
(dd),
8.08278
(dd),
8.08165
(dd),
8.07582 (dd), 8.03726
8.03984
(ddd),
8.02298
(ddd),
8.09124
(dd),
Under H5 8.08768
(dd),
J12,11 = 8.85,(dd),
J12,11 = 8.86, (dd),
J12,8 = 2.38
J12,11 = 8.81,J12,8 = 2.50 J12,11 = 8.84,J12,11 = 8.80,J12,11 = 8.83,J12,11 = 8.4,J12,8 = 2.52 J12,11 = 8.77,J12,11 = 8.79, J12,11 = 8.84, J12,11 = 8.79,
J12,11 = 8.83,
J12,8 = 2.51
J12,8 = 2.504
J12,8 = 2.50 J12,8 = 2.50 J12,8 = 2.54 J12,8 = 2.34
J12,8 = 2.38 J12,8 = 2.242,J12,8 = 2.36, J12,8 = 2.522
J12,13 = 0.98 J12,13 = 0.58

M. Odabaßsog˘lu et al. / Journal of Molecular Structure 840 (2007) 71–89
77
The UV–vis spectra of compounds 6l were studied at
different temperature in DMSO, as well as illustrated in
Fig. 4. Keto-amine tautomer is dominant at low tempera-
ture while phenol–imine form is dominant at high temper-
ature. The UV–vis spectra of 6l and 6m showed a similar
behaviour, in contrast, other azo–azomethines demonstrat-
ed very little changes in DMSO.
The UV–vis spectra of compounds 6l were also stud-
ied at different temperature in DMF as shown in
Fig. 5. Compound 6l shows two absorptions at room
temperature in the range of 300–600 nm; 422 nm for
enol-imine form and 469 nm for keto-amine form. When
the solution was heated, the new absorption band was
appeared at 537 nm at 90 ꢁC. This absorption band rep-
resents the charge transfer interaction between keto and
enol molecules as observed for all azo–azomethine com-
pounds (6a–n).
2.3. IR absorption spectra
The characteristic IR absorption bands of 5-phen-
yldiazenylsalicylaldehydes 4 and their polyhydroxy azo–
azomethine derivatives 6 were determined in KBr disk.
Table 3 shows typical characteristic IR absorption bands.
The NAHꢁ ꢁ ꢁO bands are located at about the range
3100–3500 cmꢀ1 in azo–azomethine compounds. Results
from X-ray diffraction studies show very short C@O
bonds, indicating their double bond characteristic. The
peaks for azo–azomethine compounds are very sharp and
at 1630–1670 cmꢀ1, which corresponds to m(C@O) vibra-
tion, suggesting azo–azomethine compounds in the solid
state exists as a keto-amine tautomer. Another evidence
for existence of the keto-amine tautomer is that phenolic
m(CAO) vibration, which observed in the range 1170–
1150 cmꢀ1 in azo compounds, disappeared in azo–azome-
thine derivatives. Aliphatic m(CAO) vibration is in the
range 1050–1070 cmꢀ1. Fig. 6 shows the IR spectra of com-
pound 4e and 6e.
2.4. NMR investigations
1
In their H NMR spectra, all azo compounds 4 show a
peak at 10.32–10.37 ppm, belonging to the aldehyde group.
However, this aldehyde peaks disappear in azo–azomethine
derivatives. CHAN proton appears in the range of 8.60–
1
8.67 ppm (Table 4). H NMR spectra of azo compounds
show d peaks at 8.11–8.20 ppm, d at 7.14–7.22 ppm and
dd at 8.01–8.1 ppm, which are attributed to phenyl group
1
including aldehyde group. The corresponding peaks in H
NMR spectra of azo–azomethine compounds are d at
8.0–8.19 ppm, d at 6.58–6.67 ppm and dd at 7.85–
7.91 ppm. These chemical shift differences clearly indicate
that azo–azomethine compounds shift to keto structures.
In the 1H NMR spectrum of 6e (Fig. 8), H13 and H14 pro-
tons split into doublets since the hydrogen (H14) of phenol
group is transferred to the imine nitrogen and H13 proton
interact with H14 proton (J13,14 = 10.7 Hz). In compounds

78
M. Odabaßsog˘lu et al. / Journal of Molecular Structure 840 (2007) 71–89
Fig. 7. 1H NMR spectrum of 6e.
Fig. 8. 1H NMR spectrum of 6e.
6a, 6d, 6l and 6m, similar doublets are observed, as well
(Table 6). This shows that azo–azomethine compounds
exist as keto-amine tautomers (Fig. 7).
situations were observed for compounds 6a, 6c, 6d, 6f, 6i,
6k, 6l and 6m, as well (Table 6).
Aldehydic carbons observed in azo compounds in the
range 187.2–188 ppm disappear in azo–azomethine deriv-
atives and CHAN carbons appear in the range of
164.4–165.3 ppm instead of aldehydic carbons. Despite
phenolic carbons (C10) in 13C NMR spectra of azo
compounds appear at 162.8–164.5 ppm, the correspond-
ing peaks are observed at 175.7–179.5 ppm in
azo–azomethine derivatives, which prove that azo–
azomethine compounds shift to keto structure. The
chemical shifts of carbons for azo and azo–azomethine
compounds are shown in Tables 5 and 7, respectively.
13C NMR spectra of azo compounds show peaks at
129.1–130 ppm (C8), at 118.1–118.6 ppm (C11) and at
123.6–125 ppm (C12), which are attributed to phenyl
group bearing aldehyde functionality. The corresponding
peaks in 13C NMR spectra of azo–azomethine com-
pounds are at 132.2–138.5 ppm (C8), at 114.2–
114.9 ppm (C11) and at 126.2–126.5 ppm (C12). These
chemical shifts are supported by 1H NMR spectra, as
well. These results show that azo–azomethine
compounds shift to keto structure. According to 13C
In contrast to the other p-substituted azo and azo–
azomethine compounds, in 1H NMR spectra of 4e
and 6e, since the F nucleus couples to H2, H6 and
H3, H5 protons, they respectively are seen as a quartet
and a triplet (Fig. 9). Coupling constants for proton–
fluorine are different because the fluorine atom couples
differently to the ortho-, meta- and para-protons. The
triplet can be shown as a result of consecutive splitting
of the H3, H5 absorption by the H2, H6 and F nucle-
us. The peaks overlap since the coupling constants are
identical (JHF = J3,2 = 8.72 Hz). The H2, H6 protons
are coupled to both the H3, H5 protons and F nucleus
and show doublet of doublets (J2,3 = 8.72 Hz,
JHF = 5.34 Hz). This result is in accordance with the lit-
erature [25]. The chemical shift values are shown in
Table 6.
In the 1H NMR spectrum of 6e (Fig. 10), alcoholic
OAH (H16) and adjacent –CH2 (H15) protons interact
with each other and H15 proton split into a doublet while
H16 proton gives a triplet (J15,16 = 5.18) (Fig. 10). Similar

M. Odabaßsog˘lu et al. / Journal of Molecular Structure 840 (2007) 71–89
79
Table 5
13C NMR signals of 5-phenyldiazenylsalicylaldehydes 4
3
5
2
12 11
1
4
N
10
N
OH
R
6
7
9
8
CHO
13
4a
4b
4c
4d
4e
4f
4h
4i
4j
4k
4l
4m
4n
C1
C2
151.804
122.178
149.831 147.831 152.872 148.530
150.426 151.209
129.398 129.637
149.958 150.152 150.077 155.163 154.212 147.246
122.295 122.384 122.231 123.186 122.318 129.459
137.052 133.365 122.163 124.479 (d),
JC2F = 9.1
C3
C4
C5
C6
129.213
130.888
129.213
122.178
130.811 130.542 134.102 116.186 (d),
123.861 138.288
129.832 128.613 129.014 123.186 129.402 128.060
JC3F = 23.05
131.238 132.051 131.045 163.400 (d),
135.413
97.9717 141.221 147.351 145.351 148.129 137.999 141.076
JC4F = 251.6
126.455 117.481 130.442 116.186 (d),
123.861 138.288
129.398 129.637
129.832 128.613 129.014 123.186 129.402 128.060
122.295 122.384 122.231 123.186 122.318 129.459
JC5F = 23.05
115.070 127.908 120.759 124.479 (d),
JC6F = 9.1
C7
144.779
129.469
122.477
163.086
118.256
123.864
145.283 145.054 144.640 144.653
129.288 129.666 129.741 129.487
122.480 122.616 122.611 122.507
163.023 163.673 163.637 163.150
118.306 118.478 118.416 118.273
124.203 124.499 124.436 123.898
187.461 187.681 187.602 187.559
144.652 144.710
129.584 129.637
122.581 122.604
163.418 163.429
118.416 118.426
124.006 124.097
187.615 187.547
144.876 144.915 144.869 144.839 144.880 144.801
129.523 129.500 129.363 129.929 129.755 129.459
122.526 122.516 122.454 122.736 122.627 122.776
162.965 162.965 162.910 164.266 163.709 164.483
118.291 118.275 118.202 118.576 118.424 118.773
123.721 123.809 123.749 124.929 124.421 124.845
187.430 187.322 187.312 187.929 187.690 187.753
C8
C9
C10
C11
C12
C13
187.356
–CH2
–CH2
–CH2
–CH3
COCH3
CO
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
34.537
32.661
21.586
13.533
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
27.981
15.134
–
–
16.958
–
–
20.914
–
–
26.763
180.999
NMR spectra, azo–azomethine compounds exist as keto-
amine tautomers, as well. 13C NMR spectrum of 6e is
shown in Fig. 11. As in the 1H NMR spectra of 4e
and 6e, the F nucleus couples to carbons of fluorine-
containing aromatic ring and C1, C4 and C2, C6 and
C3, C5 carbons give a doublet in the 13C NMR spectra
(Fig. 12). Coupling constants for carbon–fluorine are
different as the fluorine atom couples differently to the
ipso-, ortho-, meta- and para-carbons. Coupling con-
stants for carbon–fluorine are given in Table 7. This
result is in accordance with the literature [25]. The
chemical shift values of 6 compounds are summarized
in Table 7.
bond angles for 4i and 6a. SHELXS-97 [26] and SHEL-
XL-97 [27] were used for the structure solution and
refinement.
The molecular structure of compound 4i is shown in
Fig. 13 with the atom numbering scheme. The compound
consists of two aromatic rings (C1–C6 and C7–C12), and
an azo frame (C1–N1–N2–C7). In 4i, the aromatic rings,
which adopt a trans configuration about the N@N double
bond, are nearly coplanar, with a dihedral angle of 8.10(7)ꢁ
between them. Also, our previous X-ray investigation that
the other phenyldiazenylsalicylaldehydes are nearly copla-
nar and the dihedral angles these compounds are as in
Table 11[28–31]. The 4-methyl phenyldiazenylsalicylalde-
hyde molecules are linked into [S(6)R22(4)S(6)R22(4)R44(20)
2.5. Description of the crystal structures
R44(20)] motifs [32] (Fig. 14) and CAHꢁ ꢁ ꢁp interactions
i
˚
˚
[C14AH14cꢁ ꢁ ꢁCg1 = 3.519(3)A, H14cꢁ ꢁ ꢁCg1 = 2.61(3)A,
C14AH14cꢁ ꢁ ꢁCg1 = 153(2)ꢁ; Cg1 = C1–C6 ring, (i) = x,
1 + y,z (Fig. 15)]. A significant intramolecular interaction
is noted, involving phenolic atom H and carbonyl atom
A summary of crystallographic data, experimental
details, and refinement results for 4i and 6a are given in
Table 8. Table 9 shows the selected bond distances and

Table 6
1H NMR signals of azo–azomethine compounds 6
3
5
2
12 11
1
4
N
10
O
N
R
6
7
OH
OH
14
H
N
8
9
C
H
OH
16
13
15
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
6m
6n
H2
H3
7.75332 (dd),
J2,3 = 7.54,
J2,4 = 1.44
–
–
7.71465 (t), 7.8077 (dd), 7.55690 (d), 7.69296 (s) 7.52705 (d) 7.66197 (d) 7.69155 (d) 7.68004 (d) 7.90728 (d) 7.82124 (d)
–
J2,6 = 1.42, J2,3 = 8.72, J2,3 = 8.708
J2,4 = 1.42 JHF = 5.34
J2,3 = 8.552 J2,3 = 8.228 J2,3 = 8.24 J2,3 = 8.264 J3,2 = 8,98 J3,2 = 8.594
7.5267 (t),
J3,2 = 7.54,
J3,4 = 7.54
7.34955
(dd),
J3,4 = 6.67, J3,4 = 7.1,
J3,5 = 2.59 J3,5 = 1.076
7,602795
(dd),
–
7.3507 (dd), 7.75141 (d), 7.69296 (s) 7.87341 (d), 7.31797 (d), 7.33348 (d), 7.32897 (d), 8.361945 (d), 8.084715 (d), 7.55736 (d),
J3,2 = 8.72, J3,2 = 8.708
JHF = 8.72
J3,2 = 8.552 J3,2 = 8.228 J3,2 = 8.24 J3,2 = 8.264 J2,3 = 8.98 J2,3 = 8.594 J3,4 = 7.814
H4
H5
H6
7.42140 (tt),
J4,3 = 7.54,
J4,5 = 7.54,
J4,2 = 1.44,
J4,6 = 1.44
7.25254 (td) 7.40762 (td), 7.475635
J4,3 = 6.67, J4,3 = 7.1, (dt),
J4,5 = 6.67, J4,5 = 7.1, J4,5 = 7.972,
J4,6 = 2.59 J4,6 = 1.518 J4,2 = 1.42,
J4,6 = 1.42
–
–
–
–
–
–
–
–
–
7.3129 (t),
J4,3 = 7.814,
J4,5 = 7.814
7.5267 (t),
J5,6 = 7.54,
J5,4 = 7.54
7.27486 (td), 7.422355
7.55974 (t), 7.3507 (dd), 7.75141 (d), 7.69296 (s) 7.87341 (d), 7.31797,
7.33348 (d), 7.32897 (d), 8.361945 (d), 8.084715 (d), 7.55736 (d),
J5,6 = 6.67, (td),
J5,6 = 7.972, J5,6 = 8.72, J5,6 = 8.708 J5,6 = 8.552 J5,6 = 8.228 J5,6 = 8.24 J5,6 = 8.264 J2,3 = 8.98 J5,6 = 8.594 J5,4 = 7.814
J5,4 = 6.67, J5,6 = 7.1, J5,4 = 7.972 JHF = 8.72
J5,3 = 2.59 J5,4 = 7.1,
J5,3 = 1.076
7.8563 (dd),
J6,5 = 7.54,
J6,4 = 1.44
7.50970
(dd),
7.61655
(dd),
7.726305
(dt),
7.8077 (dd), 7.55690 (d), 7.69296 (s) 7.52705 (d), 7.66197 (d) 7.69155 (d), 7.68004 (d), 7.90728 (d), 7.82124 (d),
J6,5 = 8.72, J6,5 = 8.708 J6,5 = 8.552 J6,5 = 8.228 J6,5 = 8.24 J6,5 = 8.264 J3,2 = 8.98 J6,5 = 8.594
–
J6,5 = 6.67, J6,5 = 7.1, J6,5 = 7.972, JHF = 5.34
J6,4 = 2.59 J6,4 = 1.518 J6,4 = 1.42,
J6,2 = 1.42
H8
8.05284 (d),
8.03852 (d), 8.088505
8.0938 (d), 8.04246 (d), 8.0369 (d), 8.05915 (d), 8.03934 (s) 8.012515 (d), 8.01839 (d), 8.00369 (d), 8.18761 (d), 8.13532 (d), 8.1012 (d),
J8,12 = 2.656 J8,12 = 2.49 (d),
J8,12 = 2.646
J8,12 = 2.628 J8,12 = 2.622 J8,12 = 2.586 J8,12 = 2.54
J8,12 = 2,59 J8,12 = 2,49 J8,12 = 2.484 J8,12 = 2.164 J8,12 = 2.612 J8,12 = 2.16
H11
H12
6.62586 (d),
6.66174 (d), 6.632205
J11,12 = 9.42 J11,12 = 9.36 (d),
J11,12 = 9.5
6.60796 (d), 6.627535 (d), 6.62566 (d), 6.61395 (d), 6.622215
J11,12 = 9.52 J11,12 = 9.46 J11,12 = 9.50 J11,12 = 9.38 (d),
6.63157 (d), 6.6614 (d), 6.6468 (d), 6.59595 (d), 6.60399 (d), 6.56778 (d),
J11,12 = 9,47 J11,12 = 9.35 J11,12 = 9.37 J11,12 = 9.61 J11,12 = 9.548 J11,12 = 9.58
J11,12 = 9.52
7.87341
(dd),
7.88577 (dd), 7.89718
J12,11 = 9.42, (dd),
7.89899
(dd),
7.884235
(dd),
7.874505
(dd),
7.87254
(dd),
7.87254
(dd),
7,867565
(dd),
7.883635
(dd),
7,871015
(dd),
7.90728
(dd),
7.90985 (dd), 7.84315
J12,11 = 9.548, (dd),
J12,8 = 2.656 J12,11 = 9.36, J12,11 = 9.5, J12,11 = 9.52, J12,11 = 9.46, J12,11 = 9.50, J12,11 = 9.38, J12,11 = 9.52 J12,11 = 9.47, J12,11 = 9.35, J12,11 = 9.37, J12,11 = 9.61, J12,8 = 2.612 J12,11 = 9.58,
J12,8 = 2.49 J12,8 = 2.646 J12,8 = 2.628 J12,8 = 2.622 J12,8 = 2.586 J12,8 = 2.54 J12,8 = 2.59 J12,8 = 2.49 J12,8 = 2.484 J12,8 = 2.164 J12,8 = 2.16

H13
H14
8.63625 (d),
J13,14 = 11.4
14.4665 (d),
J14,13 = 11.4
8.64426 (s) 8.64356 (s) 8.62985 (d), 8.63675 (d), 8.61241 (s) 8.6168 (s)
8.6127 (s) 8.6115 (s)
8.65015 (s) 8.6266 (s)
8.66296 (d), 8.65503 (d), 8.6393 (s)
J13,14 = 10.4 J13,14 = 11.76
J13,14 = 11.3 J13,14 = 10.7
14.5164 (s) 14.4126 (s) 14.3699 (d), 14.475 (d), 14.489 (s)
14.3654
14.3862 (s) 14.5489 (s) 14.428 (s)
14.4902 (s) 14.1995 (d), 14.3055 (d) 14.1835
J14,13 = 10.4 J14,13 = 11.76
J14,13 = 11.3 J14,13 = 10.7
H15
H16
3.6616 (d),
J15,16 = 4.6
3.67599 (s) 3.66358 (d), 3.64997 (d), 3.656755 (d), 3.65104 (d), 3.6440 (s)
3.6533(s)
3.64558 (d), 3.6842 (s)
J15,16 = 4.172
3.6547 (s)
3.65442 (d), 3.68353 (d), 3.6633(s)
J15,16 = 4.1 J15,16 = 4.75
J15,16 = 4.97 J15,16 = 5.15 J15,16 = 5.18 J15,16 = 3.65
5.15629 (t),
5.09196 (s) 5.15744 (s) 5.17728 (t), 5.15663 (t), 5.14672 (s) 5.1252 (s)
5.18062 (s) 5.17561 (t) 5.1236 (s)
5.0587 (s)
5.26849 (s) 5.24188 (t), 5.2799 (s)
J16,15 = 4.6
J16,15 = 5.15 J16,15 = 5.18
J16,15 = 4.172
J16,15 = 4.75
–CH2
–CH2
–CH2
–CH3
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
2.63341 (t),
J = 7.686
1.58142 (p),
J = 7.686
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
2.6476 (q), 1.31185 (h),
J17,18 = 7.58 J = 7.686
1.1928 (t)
J18,17 = 7.58 J = 7.686
–
2.61356 (s)
–
2.3562 (s)
–
0.89607 (t),
–
C(@O)CH3 –
–
–
2.6057 (s)

82
M. Odabaßsog˘lu et al. / Journal of Molecular Structure 840 (2007) 71–89
Table 7
13C NMR signals of polyhydroxy azo–azomethine derivates
3
2
12 11
N
1
4
R
O
N
N
7
5
6
10
13
OH
OH
H
8
9
14
OH
15
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
6m
C1
C2
C3
C4
C5
C6
152.253 150.142 148.263 153.453 148.985 (d),
150.998 151.241 151.781 150.313 150.501 150.455 156.125 154.953
129.292 123.523 123.669 121.692 121.754 121.630 122.345 121.647
123.312 132.127 138.132 129.677 128.421 128.929 124.915 129.388
JC1F = 3.05
121.635 135.956 136.159 121.446 123.626 (d),
JC2F = 8.8
129.100 129.377 127.748 135.943 115.961 (d),
JC3F = 22.7
129.519 130.999 130.670 130.835 162.603 (d),
135.275 123.523
95.823 139.590 145.757 144.349 146.894 136.738
JC4F = 247.5
129.100 126.447 117.290 128.832 115.961 (d),
123.312 132.127 138.132 129.677 128.421 128.929 124.915 129.388
129.292 123.523 123.669 121.692 121.754 121.630 122.345 121.647
JC5F = 22.7
121.635 114.875 130.328 120.058 123.626 (d),
JC6F = 8.8
C7
140.513 141.160 140.692 140.129 140.347
134.285 133.968 132.356 133.888 134.325
123.130 122.988 123.906 123.719 123.161
176.572 176.153 178.038 177.856 176.586
114.629 114.680 114.369 114.442 114.611
126.357 126.298 126.483 126.306 126.288
164.703 164.634 164.892 164.850 164.670
140.377 140.277 140.401 140.685 140.728 140.655 140.429 140.464
133.871 135.263 135.288 133.559 133.483 133.441 138.421 136.643
123.619 122.445 123.669 122.920 122.841 122.798 124.487 123.968
177.445 177.426 177.498 176.007 175.900 175.863 179.490 178.352
114.564 114.493 114.577 114.785 114.809 114.759 114.387 114.425
126.434 126.350 126.487 126.450 126.457 126.349 126.273 126.320
164.645 164.793 164.868 164.679 164.656 164.599 165.215 164.970
C8
C9
C10
C11
C12
C13
C14
65.996
65.999
65.974
65.981 65.985
66.057
65.975
60.511
66.074
66.066
66.066
60.684
66.009
66.041
65.992
60.452
C15
60.559
60.615
60.471
60.490 60.564
60.591
60.607
60.667
60.608
34.465
32.769
21.576
13.583
60.358
–CH2
–CH2
–CH2
–CH3
C(@O)CH3
C@O
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
27.889
15.214
17.006
–
–
20.826
–
–
–
–
–
–
26.683
181.082
elongation of the C13AN3 bond and contraction of the
C10-O1 bond. For quinoid form, these values are quite
typical as observed from the N,N0-di-5-nitrosalicylidene-
(R,R)-1,2-cyclohexanediamine [41], N,N0-di-5-nitrosalicy-
ene)amino]ethyl}amine [47]. Secondly, the ‘hydroxyl’ H-
atom was located on atom N3, thus confirming a prefer-
ence for the keto-amine tautomer in the solid state.
Finally, there is a strong intramolecular N3AH33ꢁ ꢁ ꢁO1
hydrogen bond, which is a common feature of salicylid-
ene systems [35–37]. It has been reported that there may
be an orientational disorder in azobenzene, resulting in a
lidene-(R,S)-1,2-cyclohexanediamine
[42], 6-hydroxy-
2-{[tris(hydroxymethyl)methyl]aminomethylene}cyclohexa-
3,5-dien-1(2H)-one and 6-methoxy-2-{[tris(hydroxymeth-
yl)methyl]aminomethylene}cyclohexa-3,5-dien-1(2H)-one
[17], N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]salicylaldimine
[17,43], N-(a-naphthyl)-2-oxy-1-naphthaldimine [44], N-
´
˚
shortening of the N@N bond [to 1.189(6) A] and an
´
˚
elongation of the NAPh bonds [to 1.473(4) A]; these
´
´
˚
˚
(5-chloro-2-hydroxybenzylidene)-4-hydroxyaniline
[45],
bond lengths are 1.249(4) A and 1.431(4) A, respectively,
in azobenzene with no disorder (Harada et al., 1997).
The N1@N2, N1AC1 and N2AC7 bonds in (I) are
17a-hydroxy-3-methoxy-16a-[(E)-salicylideneamino] estra-
1,3,5(10)-triene [46], tris{2-[(3-formyl-5-methyl salicylid-

M. Odabaßsog˘lu et al. / Journal of Molecular Structure 840 (2007) 71–89
83
Fig. 11. 13C NMR spectrum of 6e.
Fig. 12. Part of 13C NMR spectrum of 6e.
Table 9
Table 8
Crystal data of 4i and 6a
˚
Selected geometric parameters for 4i and 6a (A,ꢁ)
4i
6a
4i
6a
O1AC13
O2AC10
N1AN2
N2AC7
N1AC1
1.219 (3)
1.340 (3)
1.259 (3)
1.425 (3)
1.428 (3)
O1AC10
N1AN2
N1AC1
N2AC7
N3AC13
C1AC2
1.2913 (15)
1.2559 (16)
1.4300 (17)
1.4157 (17)
1.2997 (16)
1.396 (2)
1.3744 (19)
1.4199 (18)
1.4395 (18)
1.3639 (19)
Empirical formula
Formula mass
Crystal system
Space group
C
11H12N2O2
C17H19N3O4
329.35
Monoclinic
P21/c
240.26
Monoclinic
P21/c
´
˚
a (A)
21.662(4)
4.6493(8)
11.599(2)
95.785(4)
17.570(2)
9.6697(12)
9.3405(11)
92.083(3)
´
˚
O2AC10AC11
O2AC10AC9
C8AC7AN2
C12AC7AN2
O1AC13AC9
C6AC1AN1
C2AC1AN1
117.7 (2)
122.7 (2)
117.1 (2)
124.6 (2)
123.7 (2)
115.2 (2)
126.1 (2)
C7AC8
b (A)
C9AC13
C9AC10
C11AC12
´
˚
c (A)
b (o)
´
3
˚
V (A )
1162.3(4)
4
1.373
1585.9(3)
4
1.379
N2AN1AC1
N1AN2AC7
C8AC7AN2
O1AC10AC9
N3AC13AC9
C1AN1AN2AC7
113.74 (11)
114.34 (11)
116.37 (12)
121.23 (12)
123.63 (12)
172.80 (11)
Z
qcalc (g cmꢀ3
)
l (mmꢀ1
)
0.094
0.100
C7AN2AN1AC1
179.36 (17)
R1/wR2 (obsd data: 2r(I)])
R1/wR2 (all data)
Goodness of fit
0.0570/0.1479
0.0840/0.1724
1.102
0.0450/0.1089
0.0806/0.11273
0.913

84
M. Odabaßsog˘lu et al. / Journal of Molecular Structure 840 (2007) 71–89
Fig. 13. A view of 4i, with the atom numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.
Fig. 14. A partial packing diagram for 4i, with OAHꢁ ꢁ ꢁO, CAHꢁ ꢁ ꢁO and CAHꢁ ꢁ ꢁN hydrogen bonds shown as dashed lines. the atom numbering scheme.
H-atom not involved in these interactions have been omitted. [Symmetry codes: (i) x,y ꢀ 1,z ꢀ 1/2; (ii) x,y ꢀ 1/2,z; (iii) x,1 + y,z ꢀ 1/2].
´
´
´
˚
˚
˚
1.259(3) A, 1.428(3) A and 1.425(3) A, respectively,
indicating that there is no orientational disorder. The
two phenyl rings are planar but not coplanar with one
another. The dihedral angle between the planes of the
phenyl and salicylidene rings is 24.29(4)ꢁ and this value
is a little larger than those in (E)-azobenzenes {(5–15ꢁ);
[39]} and phenyldiazenylsalicylaldehydes {(3–7ꢁ); [28–
31]}. Our previous X-ray investigation that the other
azo–azomethine compounds of salicylaldehydes have sim-
ilar dihedral angles and these data are in Table 11. In
addition to the intramolecular hydrogen bond, molecules
of 6a are linked by intermolecular OAHꢁ ꢁ ꢁO hydrogen
bonds into a three-dimensional network (Fig. 17 and
Table 10).
2.6. Antimicrobial activity of azo and azomethines
At present study, in vitro potential antimicrobial activity
of 4a, 4c, 4d, 4e, 4f, 4g, 4i, 4j, 4k, 4m and 6a, 6c, 6d, 6e, 6f,
6g, 6i, 6j, 6k and 7 compounds were tested according to
disc diffusion method, are reported in Tables 12 and 13.
Antimicrobial activity was measured for 250, 500 and
1000 lg/ml concentrations against Gram-negative bacteria
namely Escherichia coli, Salmonella typhimurium, and
Enterobacter cloaceae, Gram-positive Nocardia farcinica,
Staphylococcus aureus and Bacillus subtilis, yeast Candida
albicans, and mould Aspergillus niger. Streptomycin and
ampicillin were used as referance antibiotics for all tests.
Among the 4 series compound tested, 4a, 4d, 4c, 4f, 4e

M. Odabaßsog˘lu et al. / Journal of Molecular Structure 840 (2007) 71–89
85
Fig. 15. A partial packing diagram for 4i, with OAHꢁ ꢁ ꢁO hydrogen bonds and CAHꢁ ꢁ ꢁp interactions shown as dashed lines. the atom numbering scheme.
H-atom not involved in these interactions have been omitted.
Table 10
´
˚
Hydrogen-bonding geometry (A, ꢁ) for 4i and 6a
D–Hꢁ ꢁ ꢁA
D–H
Hꢁ ꢁ ꢁA
Dꢁ ꢁ ꢁA
D–Hꢁ ꢁ ꢁA
4i
O2AH1ꢁ ꢁ ꢁO1
0.91(4)
0.91(4)
0.97(2)
0.97(2)
0.97(2)
1.87(4)
2.34(4)
2.78(2)
2.84(3)
2.64(3)
2.679(3)
2.863(3)
3.587(3)
3.758 (3)
3.276 (3)
148(3)
117(3)
141.10(19)
158.70(24)
123.21(23)
O2AH1ꢁ ꢁ ꢁO1(i)
C11AH11ꢁ ꢁ ꢁN2(ii)
C13AH13ꢁ ꢁ ꢁO1(iii)
C13AH13ꢁ ꢁ ꢁO2(iv)
6a
N3AH1ꢁ ꢁ ꢁO1
0.86(2)
0.84(2)
0.86(2)
0.94(4)
0.97(2)
1.904(17)
1.918(19)
1.788(19)
1.674(18)
2.401(15)
2.616(2)
2.754(2)
2.630(1)
2.606(1)
3.323(2)
138.8(15)
174.0(17)
165.8(19)
174.0(18)
159.5(12)
O2AH22ꢁ ꢁ ꢁO3i(v)
O3AH33ꢁ ꢁ ꢁO4(v)
O3AH33ꢁ ꢁ ꢁO4(vi)
C17AH17bꢁ ꢁ ꢁO3(iv)
(i)
(ii)
1 ꢀ x,ꢀ1 ꢀ y,ꢀz.
x,ꢀy + 1/2,z ꢀ 1/2.
ꢀx + 1,+y + 1/2,ꢀz + 1/2.
x,ꢀy ꢀ 1/2,z + 1/2.
ꢀx,ꢀy,ꢀ1 ꢀ z.
(iii)
(iv)
(v)
(vi)
ꢀx,ꢀy,ꢀz.
and 4j were found active against only Gram-positive bacte-
ria S. aureus, B. substilis, and N. farcinica. The same com-
pounds were also tested against Gram-negative bacteria,
yeast and mould, but there was not any activity detected.
However, among these compounds, 4f, 4m and 4g had an
effect on Gram-positive N. farcinica with the exception of
4k. In general, all 4 series compound showed weak to
moderate antibacterial activity against tested Gram-posi-
tive bacteria (Tables 12). Among all 4 series compounds
(4a–4m) the strongest inhibitory effect was observed for
4a which was derivated from aniline. However, when the
substituents were added to phenyl-ring, activity of 4 series
compounds were reduced. The greatest inhibitory
reduction occurred when 4a was placed in to para position
(compounds 4f). Reduction range in antimicrobial activity
of 4 series compound depending on substituents given as
following;
Further studies were conducted to synthesize 6a, 6c–6g,
6i–6k and compound 7 (Scheme 3) compounds by the addi-
tion of 7 to synthesize 6 series compounds. 7 itself did not
show an inhibition on tested microorganisms. A detail
analysis results reported in Table 13 shows inhibition zones
mm in diameter. The comparison of the data obtained
for 4a, 4c–4g, 4i–4k and 4m and 6a, 6c–6g, 6i–6k and

86
M. Odabaßsog˘lu et al. / Journal of Molecular Structure 840 (2007) 71–89
Fig. 16. A view of 6a, with the atom numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.
Table 11
Some X-ray parameters of some phenyldiazenylsalicylaldehydes (4) and trishydroxymethylaminomethane derivatives (6)
Compound
Dihedral angle (ꢁ)
Intramolecular hydrogen bond
Ref.
´
˚
Angle (ꢁ)
Length (A)
6a
4c
6c
6d
4f
4g
4i
24.29 (4)
4.1(1)
9.9(1)
20.47(10)
3.69(14)
3.65(16)
3.65(16)
6.85(19)
8.92(2)
2.6158 (15)
2.962(2)
2.692(2)
2.639(2)
2.702(4)
2.693(4)
2.679(3)
2.615(5)
2.652(6)
38.8 (14)
149(2)
149(2)
139(2)
130(5)
141(5)
148(3)
161(7)
125(6)
This paper
[28]
[28]
[18]
[29]
[30]
This paper
[31]
4j
6j
[38]
Fig. 17. A partial packing diagram for 6a, with hydrogen bonds shown as dashed lines. the atom numbering scheme. H-atom not involved in these
interactions have been omitted.
compound 7 indicates that the antimicrobial activities of 6
series compounds were markedly increased. All the 6
compounds which found the possess growth inhibitory
activity against tested bacteria with the exception of 6g
and 7. 6 compounds such as 6j, 6g, and 6d showed inhibi-
tory effect on yeast too. On the other hand, while there was
no activity 4 series compound with lack of 7, Some 6
compounds possessed antimicrobial activity such as 6e,
6a, 6c and 6k were found effective on both yeast and mould
by the addition of compound 7.
As can be seen from Tables 12 and 13, 6 compounds had a
broad spectrum of action and highest growth inhibitory
activity compare to 4 series compounds. The main reason
for this increment in 6 compounds action was explored in

M. Odabaßsog˘lu et al. / Journal of Molecular Structure 840 (2007) 71–89
87
Table 12
Observed inhibition zone diameters in millimetres for substrates 4a, 4c, 4d, 4e, 4f, 4g, 4i, 4j, 4k and 4m and test compounds
Compound
Concentrations (lg)
S. aureus
B. subtilis
N. farcinica
E. coli
S. typhimurium
E. cloaceae
C. albicans
A. niger
4a
250
500
1000
10
13
16
11
12
16
13
15
19
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
4c
4d
4e
4f
250
500
1000
12
13
15
10a
11a
14a
12
12
14
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
250
500
1000
9
12
14
10a
12a
14a
12
15
15
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
250
500
1000
8
9
12
7
7
11
8
9
11
250
500
1000
–
–
–
–
–
–
7a
8a
10a
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
4g
4i
250
500
1000
–
–
–
–
–
12
–
9
11a
250
500
1000
8
9
10
9
11
12
10
12
14
4j
250
500
1000
9
10
11
9
10a
11
9
10
11
4k
4m
250
500
1000
–
–
–
7
8
8
–
–
8
250
500
1000
–
–
–
–
–
10
10
11
13
Streptomycin
Ampicillin
10
10
20
30
–
17
15
–
15
–
29
20
–
16
16
–
29
20
–
–
–
–
–
–
–
DMSO
20 (ll)
–
a
Unclear zone.
1
terms of whether related to azometin substitution or not.
Therefore compound 7 was synthesised and tested on micro-
organisms. As can be seen from Table 13, compound 7 has
no effect on tested microorganism itself. It is thought that
the main reason the increasing antimicrobial activity of 6 ser-
ies compounds which related to presence of azo and azome-
tin groups compounds on the same molecule. The greatest
inhibitory activity was shown by 6a which does not has
phenyl-ring. A range of antimicrobial activity of 6 com-
pounds depending on substituents was given as following;
eter. The H NMR and 13C NMR spectra were taken on
Bruker AC 200 MHz spectrometer. Crystal structures were
analyzed with STOE STADI 4 diffractometer [40]. Elemen-
tal analyses were carried out in TUBITAK Marmara
Research Center.
3.2. Dye synthesis and purification
A mixture of 3-chloroaniline (1.275 g, 10 mmol), water
(50 ml) and concentrated hydrochloric acid (2.5 ml,
30 mmol) was heated with stirring until a clear solution
was obtained. This solution was cooled to 0–5 ꢁC and a solu-
tion of sodium nitrite (0.96 g, 14 mmol) in water was added
dropwise while the temperature was maintained below
5 ꢁC. The resulting mixture was stirred for 30 min in an ice
bath. Salicylaldehyde (1.22 g, 10 mmol) solution (pH 9)
was gradually added to a cooled solution of 3-chloro-
benzenediazonium chloride, prepared as described above,
and the resulting mixture was stirred at 0–5 ꢁC for 60 min
3. Experimental
3.1. Instrumentation
All melting points were analyzed with an electrothermal
melting point apparatus. FT-IR spectra were recorded on
FTIR-8900 Schmadzu spectrophotometer. Absorption
spectra were analyzed on Unicam UV–vis spectrophotom-

88
M. Odabaßsog˘lu et al. / Journal of Molecular Structure 840 (2007) 71–89
Table 13
Observed inhibition zone diameters in mm for substrates 6a, 6c, 6d, 6e, 6f, 6g, 6i, 6j, 6k and 7 and test compounds
Compound
Concentrations (lg)
S. aureus
B. subtilis
N. farcinica
E. coli
E. cloaceae
S. typhimurium
C. albicans
A. niger
6a
250
500
1000
20
21
22
23
25
27
29
32
35
–
–
–
–
–
–
–
–
–
12
16
19
9
11
12
6c
6d
6e
6f
6g
6i
250
500
1000
16
17
19
18
19
20
25
28
30
–
–
–
–
–
–
–
–
–
10
11
13
8
8
9
250
500
1000
13
16
18
16
17
18
15
19
22
–
–
–
–
–
–
–
–
–
9
12
14
–
–
–
250
500
1000
13
15
17
13
15
18
20
21
22
–
–
–
–
–
–
–
–
8
10
12
8
9
9
250
500
1000
7
9
12
8
9
10
9
10
13
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
250
500
1000
–
–
10
–
–
7
7
7
7
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
250
500
1000
17
18
19
17
18
19
15
22
24
–
–
–
–
–
–
–
–
–
11
13
15
–
–
8
6j
250
500
1000
15
16
17
15
16
17
15
21
23
–
–
–
–
–
–
–
–
–
9
12
14
–
–
–
6k
7
250
500
1000
10
11
12
9
10
11
9
10
13
–
–
–
–
–
–
–
–
–
7
7
8
8
8
9
250
500
1000
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
Streptomycin
Ampicillin
DMSO
10
10
20
9
17
23
–
15
–
29
20
–
16
16
–
29
20
–
–
–
–
–
–
–
20 (ll)
–
–
OH
N
(7)
OH
OH
OH
(E)-2-((1,3-dihydroxy-2-(hydroxymethyl)propan-2-ylimino)methyl)phenol
Scheme 3.
in an ice bath. The product was recrystallized from ethyl
alcohol, giving solid 5-(3-chlorophenylazo)salicylaldehyde
(mp 127–129 ꢁC). To a solution of this solid (1.302 g,
5 mmol) in butanol (75 ml) was added a solution of
tris(hydroxymethyl) aminomethane (0.605 g, 5 mmol) in
butanol (25 ml). The mixture was stirred under reflux and
water produced in the reaction was distilled out. The result-
ing orange precipitate was filtered off and recrystallized from
ethyl alcohol. Crystals of (I) were obtained after 2 d by slow
evaporation from acetonitrile (yield 90%; mp 182–184 ꢁC).
3.3. Antimicrobial activity studies
As a preliminary screening for antimicrobial activity of
6a, 6c–6g, 6i–6k and 7 and 4a, 4c–4g, 4i–4k and 4m were
tested against bacterial strains of Gram-positive, B. subtilis,
N. farcinica ATCC 3318, Gram-negative E. coli W3110,
Enterobacter cloaceae, S. typhimurium LT2, and, a yeast
Candida albicans ATCC 10231 and a mould Aspergillus
niger. Antimicrobial studies were performed according to
agar disc diffusion method. The following test conditions

M. Odabaßsog˘lu et al. / Journal of Molecular Structure 840 (2007) 71–89
89
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Acta Crystallogr. C60 (2004) o133.
were applied; all the compounds were dissolved in dimeth-
ylsulfoxide (DMSO, Merck). Nutrient agar (Acumedia)
plates were prepared and dried at 35–36 ꢁC for about
30 min in an incubator. Test strains were spreaded on solid
nutrient agar surface by using sterile swap. Spreaded inoc-
ulum was 3.5 · 105 colony forming unit/ml (0.5 McFarland
standard). At the same time, absorbent paper discs were
placed on agar surface (5 mm for compounds and 6 mm
for antibiotics) and impregnated with known concentra-
tions which determined previously by MIC tests (250, 500
and 1000 lg for each disc). Streptomycin and Ampicillin
antibiotics (Bioanalyse) were also used for all test microor-
ganisms as positive control. Blank test showed that DMSO
in the preparations of the test solutions does not affect the
test organisms. They were inverted and allowed to incubate
at 37 ꢁC. The inhibition zone around the disc was calculat-
ed edge-to-edge zone of confluent growth, which is usually,
corresponds to the sharpest edge of the zone and to be
measured diameter in millimetres. All tests were repeated
three times and average data taken as final result.
[16] M. Odabaßsog˘lu, C¸ . Albayrak, O. Buyukgungo¨r, Acta Crystallogr.
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¨
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E60 (2004) o142.
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Appendix A. Supplementary data
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Supplementary data associated with this article can be
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