Hydrogen bonding properties and intermediate structure of N-(2-carboxyphenyl)salicylidenimine

Article abstract of DOI:10.1039/a809497g

The hydrogen bonding properties, the nature of the tautomeric structure and dimerization of N-(2-carboxyphenyl)-salicylidenimine 1 has been studied. The crystal and molecular structure of 1 has been determined by single-crystal X-ray diffraction analysis. This compound forms a dimer in the solid state, which is held together by two strong intermolecular O-H ... O bridges [O(1) ... O(2a) = 2.455(1) A]. This dimeric structure is further stabilized by two intramolecular N-H ... O hydrogen bonds [N(1) ... O(1) = 2.654(1) and N(1) ... O(2) = 2.663(1) A]. In this way, an eight-membered pseudocycle is created. However, in methanol or acetonitrile solution, no dimerization was observed according to ¹H-NMR, IR and UV measurements. It was also found that this compound exists as an intermediate form between a phenol-imine and an o-quinoid structure. In addition, a derivative soluble in chloroform, 2-[2-hydroxy-5-(2-butyl)benzylideneamino]benzoic acid 3, was examined for comparison.

Full text of DOI:10.1039/a809497g

View Article Online / Journal Homepage / Table of Contents for this issue
Hydrogen bonding properties and intermediate structure of
N-(2-carboxyphenyl)salicylidenimine
Alette G. J. Ligtenbarg,a Ronald Hage,*b Auke Meetsmaa and Ben L. Feringa*a
a Department of Organic and Inorganic Chemistry, University of Groningen, Nijenborgh 4,
9747 AG Groningen, The Netherlands
b Unilever Research Laboratory, Olivier van Noortlaan 120, 3133 AT, Vlaardingen,
The Netherlands
Received (in Cambridge) 4th December 1998, Accepted 17th February 1999
The hydrogen bonding properties, the nature of the tautomeric structure and dimerization of N-(2-carboxyphenyl)-
salicylidenimine 1 has been studied. The crystal and molecular structure of 1 has been determined by single-crystal
X-ray diffraction analysis. This compound forms a dimer in the solid state, which is held together by two strong
intermolecular O–H ؒ ؒ ؒ O bridges [O(1) ؒ ؒ ؒ O(2a) = 2.455(1) Å]. This dimeric structure is further stabilized by two
intramolecular N–H ؒ ؒ ؒ O hydrogen bonds [N(1) ؒ ؒ ؒ O(1) = 2.654(1) and N(1) ؒ ؒ ؒ O(2) = 2.663(1) Å]. In this way, an
eight-membered pseudocycle is created. However, in methanol or acetonitrile solution, no dimerization was observed
according to 1H-NMR, IR and UV measurements. It was also found that this compound exists as an intermediate
form between a phenol-imine and an o-quinoid structure. In addition, a derivative soluble in chloroform,
2-[2-hydroxy-5-(2-butyl)benzylideneamino]benzoic acid 3, was examined for comparison.
found that this compound exhibits an interesting dimeric struc-
Introduction
ture in the solid state. Most intriguing is the discovery that this
In recent years, a number of studies have been reported concern-
compound exists as an unusual intermediate form between a
ing the reversible solid-state photochromic or thermochromic
phenol-imine and a quinoid structure.
reaction1 of N-salicylideneaniline (‘anil’) compounds.2 Organ-
ization of bistable organic molecules in the solid state is of great
current interest in the context of molecular data storage.3,4 The
reversible changes in colour of the anil crystals upon illumin-
Results and discussion
Synthesis and X-ray analysis of 1
ation or heating are accompanied by a transition that takes
place between two tautomeric structures due to intramolecular
proton transfer. These tautomers, a phenol-imine structure I
and a quinoid structure II in which the proton is located at
the nitrogen, are shown in Fig. 1. This behaviour of e.g. N-(2-
hydroxybenzylidene)aniline and its derivatives has been exten-
sively studied by UV, IR, X-ray diffraction, Raman and NMR
spectroscopy. Various studies were carried out with these sys-
tems in order to establish the existence of intramolecular
hydrogen bonding stabilizing one of the tautomeric forms.2
Until now, most of the X-ray structures known for this class of
compound have been referred to as phenol-imine tautomers.5
However, a few quinoid structures6 have been established as
well e.g. N-salicylidene-2-hydroxyaniline (measured at 123 K)6b
Compound 1 was prepared according to a literature pro-
cedure11 as described in the Experimental section. Crystals
suitable for X-ray analysis were obtained from a concentrated
methanolic solution of 1 by slow evaporation of the solvent.
Part of the compound decomposed during crystallization due
to the sensitivity of the molecule towards methanol. Crystal-
lization from other organic solvents yielded crystals of inferior
quality. The molecular structure (measured at 295 K) and the
adopted atom numbering are presented in Fig. 2. Bond dis-
tances and angles are listed in Table 1.
The monoclinic I-centered unit cell contains eight molecules.
In the crystal lattice two molecules are coupled by two strong
intermolecular O–H ؒ ؒ ؒ O bridges [O(1) ؒ ؒ ؒ O(2a) = 2.455(1) Å
(at 295 K)] resulting in the formation of dimers12 which have a
crystallographic imposed twofold axis. Weaker C–H ؒ ؒ ؒ O
interactions link them to infinite one-dimensional chains along
the [100] vector (Table 2).
and
2,3-dihydroxyphenylmethanimine-α-(2-hydroxymethyl)-
benzene (at 300 K).6d
Schiff base compounds are often used as ligands in coordin-
ation chemistry because they are generally known for their
metal binding ability, and in particular salicylaldimines are use-
ful for the synthesis of transition metal complexes. Noteworthy
examples include Cu,7 Fe 8 and Mn9 complexes. We have syn-
thesized N-(2-carboxyphenyl)salicylidenimine 1 as tridentate
ligand for the formation of oxovanadium complexes,10 and
Another interesting feature of this structure is the presence
of two intramolecular N–H ؒ ؒ ؒ O hydrogen bonds which stabil-
ize this dimer conformation [N(1) ؒ ؒ ؒ O(1) = 2.654(1) and
N(1) ؒ ؒ ؒ O(2) = 2.663(1) Å]. The proton of the acid group is
hydrogen-bonded to the imine-nitrogen atom forming a six-
membered ring, whereas this proton is also hydrogen-bonded to
the oxygen atom of the phenolic moiety. In this manner an
eight-membered pseudocycle is created. Distances between
hydrogen-bonded atoms are listed in Table 2. A comparable
dimer formation is known for 2,3-dihydroxyphenylmethan-
imine-α-(2-hydroxymethyl)benzene, but in this case the hydro-
gen bonds connecting the dimers are significantly longer
[A ؒ ؒ ؒ D = 2.879(4) Å].6d
X
X
N
H
N
H
O
O
I
II
Fig. 1 Intramolecular hydrogen transfer in N-salicylideneaniline
compounds.
When comparing bond distances with the mean values for
J. Chem. Soc., Perkin Trans. 2, 1999, 807–812
807

View Article Online
similar structures referred to as phenol-imine tautomers,5
a
perature (130 K). The ORTEP plot is shown in Fig. 3. Bond
number of unusual features are observed. These data were
obtained from the Cambridge Structural Database (Table 3).
For instance, C(6)–C(7) is considerably shortened as compared
with that observed in phenol-imine structures [1.4190(16) Å
instead of 1.445 Å]. C(1)–O(1) is also shortened [from 1.349 to
1.3165(15) Å], while the value of C(7)–N(1) is slightly increased
[from 1.287 to 1.2999(16) Å]. The shortening of C(6)–C(7) and
C(1)–O(1) bonds and the lengthening of C(7)–N(1) can be
explained as follows. The hydrogen of the hydroxy group
attached to C(1) is placed between atoms O(1) and O(2a) form-
ing strong O(1)–H(1) ؒ ؒ ؒ O(2a) intermolecular hydrogen bonds
[O(1)–H(1) = 1.12(2); H ؒ ؒ ؒ O(2) = 1.34(2) Å], thereby intro-
ducing partial tautomerization with appreciable keto character
to the C(1)–O(1) bond and partial double bond character to the
C(6)–C(7) bond. This causes an increase in the C(7)–N(1) bond
length. However, comparing these distances with those found
for quinoid structures,6 it is obvious that 1 cannot completely be
referred to as being in the quinoid tautomeric state. For
instance C(1)–O(1) and C(6)–C(7) bonds are too long
[1.3165(15) instead of 1.294 Å and 1.4190(16) instead of 1.407
Å, respectively], whereas the C(7)–N(1) bond possesses too
much double bond character [1.2999(16) instead of 1.327 Å]. It
can be concluded that 1 exists in the solid state as an intermedi-
ate form between tautomers I and II (Fig. 4), but it could also
be that the crystal contains 50% of each tautomer, provid-
ing an average structure which would be visible in unrealistic
anisotropic thermal displacement parameters. To clarify this
question, the crystal structure was also determined at low tem-
distances and angles are listed in Table 1. The anisotropic ther-
mal displacement parameters turned out not to be substantial
and also the rigid body analysis13 is within the standard devi-
ation. The ratio of the main axis, for example, is below 3.0 and
for most atoms it is below 2.0. Bond distances of 1 recorded at
298 K are slightly shorter than those found at 130 K (Tables 1
and 2), but this was to be expected due to the thermal motion
model. From these results it can be concluded that 1 is indeed
an intermediate structure between phenolic and quinoid
tautomers and does not exist in either two limiting structures
(type I and II).
The conformation of the molecule is nearly planar. The devi-
ation (at 295 K) of the atoms O(1), C(1)–C(10), N(1), C(13) and
C(14) from the least squares plane does not exceed 0.0558(16)
Å. O(2) deviates 0.6245(11) Å from the plane, whereas C(11)
and C(12) lie 0.1297(19) and 0.1402(16) Å out of the plane,
respectively.
Infrared spectroscopy
The infrared spectrum of 1 shows an absorption at 1691 cmϪ1
,
which is attributed to a C᎐O stretching vibration.14 A broad
᎐
O–H stretching vibration is observed at about 3450 cmϪ1. This
is indicative of hydrogen bonding, because the normal absorp-
tion band for free O–H is in the range of 3730–3520 cm
.
Ϫ1 14 A
strong C᎐N stretching vibration band is observed at 1618 cmϪ1
.
᎐
It is known that when the nitrogen atom of the C᎐N bond is
᎐
substituted in such a way that it is able to take on a more polar
character, the absorption can be found in the region 1659–1510
cmϪ1 (normal C᎐N is expected in the range of 1680–1650
᎐
Table 1 Selected bond distances (Å) and angles (Њ) of 1 with estimated
standard deviation (esd’s) in parentheses measured at 130 K and 295 K,
respectively
cmϪ1).14 In this case the hydrogen atom of the acid functionality
O(1)–C(1)
O(2)–C(14)
O(3)–C(14)
N(1)–C(7)
N(1)–C(8)
C(1)–C(2)
C(1)–C(6)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
C(6)–C(7)
C(8)–C(9)
C(8)–C(13)
C(9)–C(10)
C(10)–C(11)
C(11)–C(12)
C(12)–C(13)
C(13)–C(14)
1.3192(16)
1.2809(17)
1.2296(18)
1.3022(18)
1.4264(16)
1.4070(19)
1.4198(19)
1.375(2)
1.399(2)
1.3725(19)
1.414(2)
1.4250(19)
1.3923(19)
1.4004(19)
1.3808(19)
1.384(2)
1.3165(15)
1.2744(16)
1.2229(18)
1.2999(16)
1.4250(15)
1.4050(18)
1.4183(17)
1.372(2)
1.391(2)
1.363(2)
1.4102(18)
1.4190(16)
1.3917(18)
1.3970(17)
1.376(2)
1.369(2)
1.381(2)
1.3847(18)
1.5117(17)
1.383(2)
1.3896(19)
1.5150(19)
C(7)–N(1)–C(8)
O(1)–C(1)–C(6)
C(1)–C(6)–C(7)
N(1)–C(8)–C(13)
C(8)–C(13)–C(14)
O(2)–C(14)–O(3)
O(2)–C(14)–C(13)
C(3)–C(14)–C(13)
125.99(12)
118.57(12)
122.88(12)
118.47(11)
123.21(12)
126.01(13)
114.75(11)
119.23(12)
126.07(10)
118.65(10)
122.82(11)
118.66(10)
123.32(10)
125.81(12)
114.84(11)
119.34(11)
Fig. 2 A PLUTON representation of the structure of 1 measured at
295 K.
C(8)–C(13)–C(14)–O(2)
Ϫ31.70(19)
Ϫ30.90(18)
Table 2 Hydrogen bonds observed for 1 measured at 130 K and 295 K, respectively
D–H ؒ ؒ ؒ A/Å
D–A/Å
D–H/Å
H ؒ ؒ ؒ A/Å
D–H ؒ ؒ ؒ A/Њ
O(1)–H(1) ؒ ؒ ؒ O(2a)
N(1)–H(1Ј) ؒ ؒ ؒ O(1)
N(1)–H(1Ј) ؒ ؒ ؒ O(2)
C(7)–H(7) ؒ ؒ ؒ O(3)
C(9)–H(9) ؒ ؒ ؒ O(3)
2.453(1); 2.455(1)
2.656(2); 2.654(1)
2.667(2); 2.663(1)
3.232(2); 3.253(2)
3.237(2); 3.246(2)
1.10(2); 1.12(2)
0.95(2); 0.97(2)
0.95(2); 0.97(2)
1.00(2); 0.97(1)
0.93(2); 0.93(2)
1.36(2); 1.34(2)
1.94(2); 1.96(2)
1.95(2); 1.90(2)
2.26(2); 2.30(2)
2.39(2); 2.42(2)
173(2); 173(2)
131(2); 126(1)
131(2); 133(1)
166(1); 166(1)
148(2); 148(2)
808
J. Chem. Soc., Perkin Trans. 2, 1999, 807–812

View Article Online
Table 3 Bond distances (at 295 K) of 1 (Å) with esd’s in parentheses compared with mean distances (determined at various temperatures) for
related quinoid5a–d and phenolic4a–t structures (Å). Minimum and maximum values are given in parentheses
Bond
Distances for 1
Quinone
Phenol
C(7)–N(1)
C(1)–O(1)
N(1)–H(1Ј)
O(1)–H(1)
C(6)–C(7)
1.2999(16)
1.3165(15)
0.97(2)
1.12(2)
1.4190(16)
1.327 (1.302; 1.347)
1.294 (1.279; 1.301)
1.053 (0.903; 1.204)
1.644 (1.414; 1.836)
1.407 (1.399; 1.413)
1.287 (1.266; 1.317)
1.349 (1.323; 1.399)
1.818 (1.388; 3.536)
0.970 (0.789; 1.250)
1.445 (1.426; 1.457)
Fig. 3 An ORTEP plot of 1 measured at 130 K (50% probability level).
bonding solvent such as d6-dimethyl sulfoxide in general only
show fully dissociated components.15 A typical 1H-NMR spec-
trum of monomeric 1 in DMSO is shown in Fig. 5. The spec-
trum of 1 in acetonitrile-d3 is similar to the spectrum recorded
in DMSO, which indicates the existence of a monomeric
phenol-imine tautomeric form in acetonitrile. These observa-
tions are in agreement with the IR spectra (vide supra).
1H-NMR spectra of 1 in methanol-d4 were much more dif-
ficult to interpret because the ligand is not stable in methanol
solution. Most likely, the molecule is attacked by methanol at
the imine N(1)–C(7) bond, forming eventually, among other
products, an acetal from salicylaldehyde [5.56 ppm (s, acetal
proton)], 2-aminobenzoic acid [6.73–6.64 (m, 2H)] and salicyl-
aldehyde [9.86 ppm (s, CHO)]. Although full analysis of these
spectra was impossible, dimer formation does not occur under
the conditions employed, because no concentration dependent
shifts were observed.16
N
H
N
H
C
C
O
O
H
O
O
H
O
O
H
O
H
O
O
O
O
O
C
H
C
H
N
N
I
II
Fig. 4 Schematic representation of phenol-imine and quinoid tauto-
meric structures of 1.
located on the nitrogen causes this shift. An absorption band at
Electron spray mass measurements
1582 cmϪ1 may be assigned to a C᎐C stretching vibration.14
᎐
The IR spectra of solid samples and solutions are clearly
Additional experiments were performed using electron spray
mass spectrometry (ESMS).17 Varying the concentration of 1 in
methanol starting from 1 × 10Ϫ6 to 1 × 10Ϫ3 M reveals a con-
tinuing increase of a mass peak of 483, which corresponds
to (2M ϩ H). These results differ from the observations with
1H-NMR in methanol (vide supra). However it is known with
ESMS, that it is difficult to distinguish between dimers in
solution and cluster formation inside the mass spectrometer.18
Samples measured at higher concentrations (10Ϫ5 M and above)
can give association of two molecules held together by a Hϩ or
a Naϩ. A lot of degradation products were also found, which is
in agreement with the NMR studies. When acetonitrile is used
as a solvent, no significant dimer formation was observed at the
same concentrations, which was compatible with the NMR
data as well. The mass spectra and NMR experiments both
showed greater stability of 1 in acetonitrile than in methanol.
different. Although in acetonitrile the absorption of the C᎐N
᎐
bond is observed at 1620 cmϪ1 (1618 cmϪ1 for the solid sample),
a shift is observed for the C᎐O stretching vibration from 1691 to
᎐
1727 cmϪ1. Varying the concentration of 1 does not influence
the spectrum. This indicates the absence of intermolecular
hydrogen bonds. It seems that in solution the hydrogen of the
acid moiety is still hydrogen bonded to the imine nitrogen, but
hydrogen bonding to the phenol functionality of a second
monomer does not occur. We conclude that whilst the solid-
state structure shows a dimeric entity, in solution it appears to
be monomeric. However, the degree and nature of dimerization
in solution is very often a sensitive function of the donor and
acceptor properties and the dryness of the solvent. Therefore,
the difference was further corroborated by 1H-NMR analysis.
1H-NMR analysis
UV spectroscopy
To further support the occurrence of monomeric species of
compound 1 in solution, we have carried out additional NMR
analyses. 1H-NMR spectra of aggregates in a hydrogen-
The UV spectrum of 1 recorded in acetonitrile exhibits four
bands at 214, 274, 336 and 429 nm. The band at 214 nm
J. Chem. Soc., Perkin Trans. 2, 1999, 807–812
809

View Article Online
Fig. 5 1H-NMR spectrum of 1 in acetonitrile-d3.
(ε = 26.1 103 MϪ1 cmϪ1) is considered to arise from electronic
examine possible dimer formation of 3. In chloroform, a sig-
π–π* transitions in the aromatic rings.6d The band at 274 nm
(10.6) can be assigned to π–π* transitions involving one aro-
matic ring and the imine functionality. The band at even longer
wavelength, 336 nm (9.5), probably arises from an intra-
molecular charge transfer interaction. Strong intramolecular
hydrogen bonding between the carboxylic hydrogen and the
imino-nitrogen forces planarity, which facilitates charge trans-
fer.19 The band at 429 nm (0.3) is assigned to a n–π* transition
confirming that 1 possesses partial o-quinoid character.20
nificant amount of a dimer with a mass of 595 (2M ϩ H) was
observed besides the mass peak of the monomer (298 corre-
sponds to M ϩ H). Molecular weight determinations in
chloroform at 38 ЊC of 0.015, 0.04, 0.07 and 0.09 M solutions,
however, indicated that dimerization does not occur. Also con-
centration dependent 1H-NMR measurements in deuterated
chloroform are consistent with a monomeric phenol-imine
tautomeric structure. Again, cluster formation seems to occur
inside the mass spectrometer. Results of experiments in aceto-
nitrile show comparable results as discussed earlier for imine 1
i.e. neither ESMS nor 1H-NMR gave any evidence for dimeriz-
ation. Also Schiff base 3 is not stable in methanol solution. In
Synthesis and structural analysis of related salicylidenimine 3
To further study the ability of these compounds to form
hydrogen-bonded aggregates in solution, the alkyl-substituted
derivative 3 was synthesized which shows higher solubility in
chloroform. In this solvent, salicylidenimine 1 is insoluble. If
dimerization was possible in solution with this type of
compound, we expected it to occur in this solvent.15
1
the mass spectra as well as in the H-NMR spectra, several
degradation products are observed.
The UV spectrum recorded in chloroform resembles that of 1
recorded in acetonitrile. Also in this case four bands are
observed, at 242 (ε = 18.7 103 MϪ1 cmϪ1), 279 (11.1), 312 (9.4)
and 438 nm (1.4). The latter shows that 3 also possesses partial
o-quinoid character as was observed for 1.
The infrared spectra of 3 in the solid state as well as in solu-
tion are very similar to those of 1. The absorptions in the solid
2-[2-Hydroxy-5-(2-butyl)benzylideneamino]benzoic acid
3
was synthesized by the Schiff-base formation of 2-hydroxy-5-
(2-butyl)benzaldehyde 2 and 2-aminobenzoic acid in chloro-
form (Scheme 1). Compound 2 had been synthesized previously
state are at 1693 (C᎐O), 1622 (C᎐N), 1568 (C᎐C) and at around
᎐
᎐
᎐
3450 cmϪ1 a broad O–H band is observed. In chloroform solu-
tion the C᎐O stretching vibration band shifts towards 1727
᎐
cmϪ1 and the C᎐N stretching vibration band is located at
᎐
1627 cmϪ1
.
NH2
+
CHCl3
COOH
CHO
Conclusions
OH
A dimeric structure was obtained for 1 in the solid state with
short intermolecular hydrogen bonds giving rise to the form-
ation of an eight-membered pseudocycle. Variable temperature
X-ray analyses show that its structure can be described best as
intermediate between phenol-imine and quinoid tautomeric
forms and is not an average of the two limiting structures. We
have shown using 1H-NMR, UV and IR measurements, that in
solution the compound exists as a monomer. In addition a
related salicylidenimine 3, soluble in chloroform, was investi-
gated. This Schiff base showed similar properties to that of 1.
Compound 3 most probably exists as a dimer in the solid state
as well, as, for instance, IR spectra of solid samples and of
solution samples are very similar in the O–H region as well
as in the carbonyl and imine region, which indicates similar
dimerization behaviour for both compounds.
2
N
COOH
OH
3
Scheme 1 Synthesis of 3.
via a Reimer–Tiemann reaction,21 but the yield was rather low
(30%). Therefore we developed a route analogous to the liter-
ature22 procedure in which o-hydroxyaryl aldehydes are formed
by treating aryloxymagnesium bromides with paraformalde-
hyde in the presence of triethylamine. In this way, 2 was
obtained in 63% yield.
Electron spray mass spectrometry (ESMS) was again used to
810
J. Chem. Soc., Perkin Trans. 2, 1999, 807–812

View Article Online
C18H19NO3: 297.136. Found: 297.139); λmax(CHCl3)/nm 242 (ε
Experimental
103 MϪ1 cmϪ1 18.7), 279 (11.1), 312 (9.4), 438 (1.4).
Proton and carbon-13 NMR spectra were recorded on a Varian
VXR-300 spectrometer (at 300 MHz and 75.4 MHz, respect-
ively). Chemical shifts are reported in δ units (ppm) relative to
the residual deuterated solvent signals. All solvents used for
NMR experiments were dried on molecular sieves (4 Å),
degassed and stored under an atmosphere of argon. High-
resolution mass spectra were obtained on an AEI MS-902
spectrometer by electron impact (EI), electron spray (ES) mass
spectra on a NERMAG mass spectrometer. Infrared spectra
were recorded on a Perkin-Elmer 841 spectrometer. UV–VIS
spectra were recorded on a HP-8453 spectrophotometer.
Elemental analyses were performed in the Microanalytical
Department of our laboratory.
X-Ray crystal structure determination of 1
An orange–red coloured block-shaped crystal of 1 having
approximate dimensions of 0.15 × 0.15 × 0.40 mm mounted on
top of a glass fiber was used for the X-ray study.
Crystal data. C14H11NO3, M = 241.25, monoclinic, space
group I2/a, T = 295 K, a = 14.840(1), b = 6.813(1), c = 22.680(1)
Å, β = 97.796(6)Њ, V = 2271.9(4) Å3, Z = 8, Dx = 1.411 g cmϪ3
,
µ(Mo-Kα) = 1.0 cmϪ1, F(000) = 1008; T = 130 K, a = 14.831(1),
b = 6.718(1), c = 22.660(5) Å, β = 97.61(1)Њ, V = 2237.8(6) Å3,
Z = 8, Dx = 1.432 g cmϪ3, µ(Mo-Kα) = 1.0 cmϪ1, F(000) = 1008.
Data collection, structure analysis and refinement. The inten-
sity data were collected on an Enraf-Nonius CAD-4F diffrac-
tometer with graphite monochromated Mo-Kα radiation
(λ = 0.71073 Å) using ω/2θ mode with ω scan width = 0.85 ϩ
0.34 tan θ at 295 K and 0.80 ϩ 0.34 tan θ at 130 K, respectively.
Intensity data were corrected for Lorentz and polarization
effects, scale variation, but not for absorption and were reduced
N-(2-Carboxyphenyl)salicylidenimine (1)
To a hot solution of o-aminophenol (3.43 g, 0.025 mol) in abso-
lute ethanol (15 ml) was added a solution of salicylaldehyde
(3.05 g, 0.025 mol) in absolute ethanol (5 ml). The orange reac-
tion mixture was heated for 5 min and then cooled in an ice
bath. Filtration of the orange precipitate yielded 1 (5.47 g,
90%). Crystals suitable for X-ray analysis were obtained from a
concentrated solution of 1 in methanol by slow evaporation of
the solvent (yield 20–40%) (Found: C, 69.63; H, 4.75; N, 5.70.
C14H11NO3 requires C, 69.70; H, 4.60; N, 5.81%); δH(300 MHz,
DMSO-d6) 13.00 (br, 2H, H1 ϩ H1Ј), 8.83 (br, 1H, H7), 7.84 (d,
1H, J = 6.96 Hz, H12), 7.62–7.60 (m, 2H, H11 ϩ H5), 7.45–
7.30 (m, 3H, H10 ϩ H9 ϩ H3), 6.96–6.91 (m, 2H, H2 ϩ H4);
δH(300 MHz, CD3CN) 8.70 (br, 1H, H7), 7.94 (d, 1H, J = 7.69
Hz, H12), 7.65–7.58 (m, 1H, H11), 7.55–7.52 (m, 1H, H5),
7.40–7.33 (m, 3H, H10 ϩ H9 ϩ H3), 6.98–6.93 (m, 2H,
H2 ϩ H4); ESMS (CH3CN) m/z 242 (M ϩ H); ESMS (MeOH)
m/z 242 (M ϩ H), 264 (M ϩ Na), 301, 360, 483 (2M ϩ H), 585
(2M ϩ Na) (HRMS calcd. for C14H11NO3: 241.074. Found:
241.074); λmax(CH3CN)/nm 214 (ε 103 MϪ1 cmϪ1 26.1), 274
(10.6), 336 (9.5), 429 (0.3).
2
to Fo . The structure was solved by direct methods with
SHELXS86.23 Refinement on F 2 was carried out by full-matrix
least-squares techniques: observance criterion F 2 у 0 was
applied during refinement. A subsequent difference Fourier
analysis resulted in the location of all the hydrogen atoms,
which coordinates and isotropic thermal displacement param-
eters were refined. The crystal (at 295 K) exhibited some sec-
ondary extinction for which the Fc values were corrected by
refinement of an empirical isotropic extinction parameter.
Final refinement on F 2 carried out by full-matrix least-squares
techniques converged at wR(F 2) = 0.1148 for 2364 reflections
with Fo2 у 0 and R(F) = 0.0388 for 1967 reflections obeying
Fo у 4.0 σ(Fo) criterion and 208 parameters. A final difference
Fourier map did not show residual peaks outside the range
0.22(4) e ÅϪ3. Final refinement on F 2 (at 130 K) converged at
wR(F 2) = 0.1001 for 2192 reflections with Fo2 у 0 and R(F) =
0.0359 for 1783 reflections obeying Fo у 4.0 σ(Fo) criterion and
207 parameters. A final difference Fourier map did not show
2-Hydroxy-5-(2-butyl)benzaldehyde (2)
Compound 2 was obtained analogously to a literature pro-
cedure:22 yield after Kugelrohr distillation (97 ЊC at 0.4 mmHg)
as a slightly yellow oil, 63%. δH(300 MHz, CDCl3) 10.86 (s, 1H,
CHO), 9.87 (s, 1H, OH), 7.38–7.33 (m, 2H), 6.92 (d, 1H,
J = 8.05 Hz), 2.60 (heptet, 1H, J = 7.0 Hz, CH), 1.65–1.50 (m,
2H, CH2), 1.23 (d, 3H, J = 6.83 Hz, CH3), 0.81 (t, 3H, J = 7.45
Hz, CH3); δC(75.4 MHz, CDCl3) 196.6 (CHO), 159.6 (C), 138.9
(C), 135.9 (CH), 131.4 (CH), 120.2 (C), 117.2 (CH), 40.4 (CH),
30.9 (CH2), 21.5 (CH3), 11.9 (CH3) (HRMS calcd. for C11H14O2:
178.099. Found: 178.100).
residual peaks outside the range 0.21(5) e ÅϪ3
.
Atomic coordinates, bond lengths and angles and thermal
parameters have been deposited with the Cambridge Crystallo-
graphic Data Centre (CCDC). For details of the deposition
scheme see ‘Instructions for Authors (1998)’, J. Chem. Soc.,
Perkin Trans. 2, available via the RSC Web page (http://
www.rsc.org/authors). Any request to the CCDC for this
material should quote the full literature citation and the refer-
ence number 188/159. See: http://www.rsc.org/suppdata/p2/
1999/807/ for crystallographic files in .cif format.
2-[2-Hydroxy-5-(2-butyl)benzylideneamino]benzoic acid (3)
Acknowledgements
To a solution of 5-sec-butylsalicylaldehyde (0.200 g, 1.12 mmol)
in chloroform (10 ml) was added 2-aminobenzoic acid (0.155 g,
1.12 mmol) in chloroform (10 ml). The reaction mixture was
stirred for 2 h. Sodium sulfate was added and the yellow solu-
tion was stirred for an additional 30 min. After filtration and
slow evaporation 3 was obtained as a yellow powder (0.24 g,
72%) (Found: C, 72.19; H, 6.35; N, 4.68. C14H11NO3 requires C,
72.71; H, 6.44; N, 4.71%); δH(300 MHz, CDCl3) 11.15 (br,
2H, H1 ϩ H1Ј), 8.44 (s, 1H, H7); 8.07 (d, 1H, J = 7.88 Hz,
H12), 7.54–7.49 (m, 1H, H11), 7.27 (t, 1H, J = 7.69 Hz, H5),
7.17–7.11 (m, 3H, H10 ϩ H9 ϩ H3), 6.98 (d, 1H, J = 8.42
Hz, H2), 2.51–2.44 (m, 1H, CH); 1.53–1.43 (m, 2H, CH2), 1.13
(d, 3H, J = 6.59 Hz, CH3), 0.73 (t, 3H, J = 7.33 Hz, CH3);
ESMS (CHCl3) m/z 298 (M ϩ H) and 595 (2M ϩ H); ESMS
(CH3CN) m/z 298 (M ϩ H); ESMS (MeOH) m/z 138
(o-aminophenol ϩ H), 178 (5-sec-butylsalicylaldehyde ϩ H),
193, 247, 298 (M ϩ H), 595 (2M ϩ H) (HRMS calcd. for
This work was financially supported by Unilever Research
Vlaardingen, The Netherlands. Mrs C. M. Jeronimus-Stratingh
and Dr A. P. Bruins are gratefully acknowledged for performing
the electron spray mass spectrometry experiments.
References
1 M. D. Cohen and S. Flavian, J. Chem. Soc. B, 1967, 334 and
references therein.
2 See, for example, E. Hadjoudis, in Photochromism, Molecules and
Systems, ed. H. Dürr and H. Bouas-Laurent, Elsevier Science
Publishers, Amsterdam, 1990, ch. 17.
3 K. Nakatani and J. A. Delaire, Chem. Mater., 1997, 9, 2682.
4 M. Irie, K. Uchida, T. Eriguchi and H. Tsuzuki, Chem. Lett., 1995,
899.
5 (a) S. V. Lindeman, V. G. Andrianov, S. G. Kravcheni, V. M.
Potapov, K. A. Potekhin and Yu. T. Struchkov, Zh. Strukt. Khim.,
1981, 22, 123; (b) O. S. Filipenko, V. I. Ponomarev, B. M. Bolotin
J. Chem. Soc., Perkin Trans. 2, 1999, 807–812
811

View Article Online
and L. O. Atovmyan, Kristallografiya, 1983, 28, 889; (c) S. M.
Aldoshin, L. O. Atovmyan and V. I. Ponomarev, Khim. Fiz. (Sov. J.
Chem. Phys.), 1984, 3, 787; (d) J. Bregman, L. Leiserowitz and
K. Osaki, J. Chem. Soc., 1964, 2086; (e) S. M. Aldoshin, M. I.
Knyazhanskii, Ya. R. Tymyanskii, L. O. Atovmyan and O. A.
D’Yachenko, Khim. Fiz. (Sov. J. Chem. Phys.), 1982, 1015; ( f ) A. E.
Obodovskaya, Z. A. Starikova, B. M. Bolotin, T. N. Safonova and
N. B. Etingen, Zh. Strukt. Khim., 1985, 26, 111; (g) O. S. Filipenko,
L. O. Atovmyan, B. L. Tarnopol’skii and Z. Sh. Safina, Zh. Strukt.
Khim., 1979, 20, 80; (h) J. Ondracek, Z. Kovarova, J. Maixner and
F. Jursik, Acta Crystallogr., Sect. C, 1993, 49, 1948; (i) F. Mansilla-
Koblavi, S. Toure, J. Lapasset, M. Carles and H. Bodot, Acta
Crystallogr., Sect. C, 1989, 45, 451; (j) T. Inabe, N. Hoshino,
T. Mitani and Y. Maruyama, Bull. Chem. Soc. Jpn., 1989, 62, 2245;
(k) G. P. Moloney, R. W. Gable, M. N. Iskander, D. J. Craik and
M. F. Mackay, Aust. J. Chem., 1990, 43, 99; (l) T. Inabe, I. Gautier-
Luneau, N. Hoshino, K. Okaniwa, H. Okamoto, T. Mitani,
U. Nagashima and Y. Maruyama, Bull. Chem. Soc. Jpn., 1991, 64,
801; (m) V. S. Sergienko, A. E. Mistryukov, V. V. Litvinov, M. I.
Knyazhanskii, A. D. Garnovskii and M. A. Porai-Koshits, Koord.
Khim., 1990, 16, 168; (n) G.-Y. Yeap, C.-L. Gan, H.-K. Fun, O. B.
Shawkataly and S.-G. Teoh, Acta Crystallogr., Sect. C, 1992,
48, 1143; (o) K. Wozniak, H. He, J. Klinowski, W. Jones,
T. Dziembowska and E. Grech, J. Chem. Soc., Faraday Trans., 1995,
91, 77; (p) M. Kwiatkowski, E. Kwiatkowski, A. Olechnowicz,
B. Kosciuszko-Panek and D. M. Ho, Pol. J. Chem., 1994, 68, 85; (q)
F. Mansilla-Koblavi, J. A. Tenon, S. Toure, N. Ebby, J. Lapasset and
M. Carles, Acta Crystallogr., Sect. C, 1995, 51, 1595; (r) J. M.
Fernández-G., A. Rodríguez-Romero, K. Panneerselvam and
M. Soriano-García, Acta Crystallogr., Sect. C, 1995, 51, 1643;
(s) Y. Elerman, A. Elmali, O. Atakol and I. Svoboda, Acta
Crystallogr., Sect. C, 1995, 51, 2344; (t) J. A. Tenon, M. Carles and
J.-P. Aycard, Acta Crystallogr., Sect. C, 1995, 51, 2603.
7 (a) T. N. Sorell, Tetrahedron, 1989, 45, 3; (b) O. J. Gelling and B. L.
Feringa, J. Am. Chem. Soc., 1990, 112, 7599.
8 (a) S. K. Dutta, J. Ensling, R. Werner, U. Flörke, W. Haasse,
P. Gütlich and K. Nag, Angew. Chem., Int. Ed. Engl., 1997, 36, 152;
(b) J. W. Pyrz, X. Pan, D. Britton and L. Que, Jr., Inorg. Chem., 1991,
30, 3461.
9 (a) E. N. Jacobsen, Catalytic Asymmetric Synthesis, ed. I. Ojima,
VCH, New York, 1993; (b) J. Connors, C. A. McAuliffe and
J. Tames, Rev. Inorg. Chem., 1982, 3, 257.
10 M. J. Clague, N. L. Keder and A. Butler, Inorg. Chem., 1993, 32,
4754.
11 A. D. Westland and M. T. H. Tarafder, Inorg. Chem., 1981, 20, 3992.
12 (a) J. Sartorius and H.-J. Schneider, Chem. Eur. J., 1996, 2, 1446;
(b) F. H. Beijer, H. Kooijman, A. L. Spek, R. P. Sijbesma and E. W.
Meijer, Angew. Chem., Int. Ed., 1998, 37, 75.
13 F. L. Hirshfeld, Acta Crystallogr., Sect. A, 1976, 32, 239.
14 L. J. Bellamy, The Infra-red Spectra of Complex Molecules, Third
edn., Chapman and Hall Ltd., London, 1975.
15 M. Mammen, E. E. Simanek and G. M. Whitesides, J. Am. Chem.
Soc., 1996, 118, 12614.
16 G. C. Pimentel and A. L. McClellan, The Hydrogen Bond, W. H.
Freeman and Company, San Francisco, 1960, ch. 4 (Part I).
17 (a) X. Cheng, Q. Gao, R. D. Smith, E. E. Simanek, M. Mammen
and G. M. Whitesides, J. Org. Chem., 1996, 61, 2204; (b) K. C.
Russell, E. Leize, A. V. Dorsselaer and J. M. Lehn, Angew. Chem.,
Int. Ed. Engl., 1995, 34, 209.
18 C. K. Meng and J. B. Fenn, Org. Mass Spectrom., 1991, 26, 542.
19 M. R. Mahmoud, A. A. El-Samahy and S. A. El-Gyar, Bull. Soc.
Chim. Fr., 1981, I-424.
20 S. R. Salman, S. K. Kanber and L. K. Arsalan, Spectroscopy Lett.,
1991, 24, 1153.
21 M. Ansar, S. Al Akoum Ebrik, R. Mouhoub, P. Berthelot,
C. Vaccher, M. P. Vaccher, N. Flouquet, D. H. Caignard, P. Renard,
B. Pirard, M. C. Rettori, G. Evrard, F. Durant and M. Debaert, Eur.
J. Med. Chem., 1996, 31, 449.
22 R. X. Wang, X. Z. You, Q. J. Meng, E. A. Mintz and X. R. Bu,
Synth. Commun., 1994, 24, 1757.
23 G. M. Sheldrick, Acta Crystallogr., Sect. A, 1990, 46, 467.
6 (a) V. A. Tafeenko, S. I. Popov and S. V. Medvedev, Zh. Strukt.
Khim., 1991, 32, 106; (b) S. V. Lindeman, M. Yu. Antipin and Yu. T.
Struchkov, Sov. Phys. Crystallogr., 1988, 33, 215; (c) V. A. Tafeenko,
T. V. Bogdan, S. V. Medvedev, A. A. Kozyrev and S. I. Popov, Zh.
Strukt. Khim., 1991, 32, 169; (d) V. G. Puranik, S. S. Tavale, A. S.
Kumbhar, R. G. Yerande, S. B. Padhye and R. J. Butcher, J. Cryst.
Spectrosc. Res., 1992, 22, 725.
Paper 8/09497G
812
J. Chem. Soc., Perkin Trans. 2, 1999, 807–812