Intramolecular hydrogen bonding and tautomerism in Schiff bases. Structure of N-(2-pyridil)-2-oxo-1-naphthylidenemethylamine

Article abstract of DOI:10.1016/S0022-2860(00)00393-8

N-(2-pyridil)-salicylidene (1) and N-(2-pyridil)-2-oxo-1-naphthylidene- methylamine (2) were studied by elemental analysis, IR, ¹H NMR and UV- visible techniques and the structure of compound (2) was examined crystallographically. The UV-visible spectra of 2-hydroxy Schiff bases are investigated in different solvents, acidic and basic media. Compound (2) is in tautomeric equilibrium (phenol-imine, O-H···N ? keto-amine, O···H-N forms) in polar and non-polar solvents. These tautomers are not observed in polar and non-polar solvents for (1) as also supported by ¹H NMR and UV- visible data. The keto-amine form of compound (2) was observed in basic solutions of DMSO, ethanol, chloroform, benzene, cyclohexane and in acidic solutions of chloroform and benzene, but not in acidic solutions of DMSO and ethanol. On the contrary, this form for compound (1) was not observed in the same solutions. The asymmetric unit of compound (2) contains two independent molecules of (C₁₆H₁₂N₂O) which constitute a tautomeric pair. The observed differences in the related C = N (1.317(4) and 1.330(4) A?) and C-O (1.279(4) and 1.263(4) A?) bond lengths in the two crystallographically independent molecules indicate that the phenol-imine and the keto-amine forms coexist in the solid state. Intramolecular hydrogen bond lengths (O-H···N) are 2.586(4) A? and 2.518(4) A? for the two individual tautomers. It crystallizes in the monoclinic space group P2₁/n with a = 5.837(2), b = 17.476(2), c = 24.295(3) A?, β = 91.95(4)°, V = 2476.9(6) A?³, Z = 4 and D(x) = 1.3315 g cm^-3. (C) 2000 Elsevier Science B.V.

Full text of DOI:10.1016/S0022-2860(00)00393-8

Journal of Molecular Structure 524 (2000) 241–250
www.elsevier.nl/locate/molstruc
Intramolecular hydrogen bonding and tautomerism in Schiff bases.
Structure of N-(2-pyridil)-2-oxo-1-naphthylidenemethylamine
a,
b
a
c
c
*
¨
H. Nazır , M. Yıldız , H. Yılmaz , M.N. Tahir , D. Ulku¨
a
Department of Chemistry, Ankara University, 06100 Tandogan, Ankara, Turkey
b
Department of Chemistry, 18 March University, C, anakkale, Turkey
c
Department of Physics, Hacettepe University, 06532 Beytepe, Ankara, Turkey
Received 4 June 1999; accepted 13 December 1999
Abstract
N-(2-pyridil)-salicylidene (1) and N-(2-pyridil)-2-oxo-1-naphthylidene-methylamine (2) were studied by elemental analysis,
1
IR, H NMR and UV–visible techniques and the structure of compound (2) was examined crystallographically. The UV–
visible spectra of 2-hydroxy Schiff bases are investigated in different solvents, acidic and basic media. Compound (2) is in
…
tautomeric equilibrium (phenol–imine, O–H N O keto–amine; O···H–N forms) in polar and non-polar solvents. These
1
tautomers are not observed in polar and non-polar solvents for (1) as also supported by H NMR and UV–visible data. The
keto–amine form of compound (2) was observed in basic solutions of DMSO, ethanol, chloroform, benzene, cyclohexane and
in acidic solutions of chloroform and benzene, but not in acidic solutions of DMSO and ethanol. On the contrary, this form for
compound (1) was not observed in the same solutions. The asymmetric unit of compound (2) contains two independent
12 2
molecules of (C16H N O) which constitute a tautomeric pair. The observed differences in the related CyN (1.317(4) and
˚
˚
1
.330(4) A) and C–O (1.279(4) and 1.263(4) A) bond lengths in the two crystallographically independent molecules indicate
that the phenol–imine and the keto–amine forms coexist in the solid state. Intramolecular hydrogen bond lengths (O–H···N)
˚
˚
are 2.586(4) A and 2.518(4) A for the two individual tautomers. It crystallizes in the monoclinic space group P2 =n with a ˆ
1
3
Ϫ3
ꢀ
ꢀ
5
:837ꢀ2†; b ˆ 17:476ꢀ2†; c ˆ 24:295ꢀ3† A; b ˆ 91:95ꢀ4†Њ; V ˆ 2476:9ꢀ6† A ; Z ˆ 4 and D ˆ 1:3315 g cm : ᭧ 2000
x
Elsevier Science B.V. All rights reserved.
Keywords: Crystal structure; Schiff bases; Tautomerism; Spectroscopic and crystallographic studies; Intramolecular hydrogen bond
1
. Introduction
catalytic reactions [12]. A series of the Schiff base
complexes display interesting structural and elec-
tronic properties [5,9,13]. Tautomerism in 2-hydroxy
Schiff bases both in solution and in solid state were
2
-Hydroxy Schiff base ligands and their complexes
derived from the reaction of salicylaldehyde and 2-
hydroxy-1-naphthaldehyde with amines have been
extensively studied [1–6] and a number of them
were used as models for biological systems [7–11].
The Schiff base complexes have also been used in the
1
5
investigated using IR [1,14,15], UV [1,15–24], N
1
13
NMR [25], H NMR [26–29], C NMR [30,31] and
X-ray crystallography techniques [32,33]. 2-Hydroxy
Schiff base ligands are of interest mainly due to the
existence of (O–H···N) and (O···H–N) type hydrogen
bonds and tautomerism between phenol–imine and
keto–amine forms [9,16,34]. In these compounds,
*
Corresponding author. Fax: ϩ 90-312-223-2395.
E-mail address: nazir@science.ankara.edu.tr (H. Nazır).
0
022-2860/00/$ - see front matter ᭧ 2000 Elsevier Science B.V. All rights reserved.
PII: S0022-2860(00)00393-8

2
42
H. Nazır et al. / Journal of Molecular Structure 524 (2000) 241–250
Scheme 1.
Scheme 2.
short hydrogen bonds were observed between the 2-
hydroxy group and the imine nitrogen. In some
instances the hydrogen from the phenol group is
completely transferred to the imine nitrogen. In
other words, Phenol–imine O keto–amine equili-
brium shifts predominantly to the keto–amine side
to the keto–amine form of the Schiff base. The
keto–amine tautomer is always observed when the
Schiff base is derived from 2-hydroxy naphthalde-
hyde and aniline. For Schiff bases derived from
salicylaldehyde and aniline, the keto–amine form
was not observed in polar and non-polar solvents,
but was noted after acid addition [1,16]. We report
here the spectroscopic studies of Schiff bases and
the crystal structure of the Schiff base formed by
2-aminopyridine and 2-hydroxy-1-naphthaldehyde
in order to compare the hydrogen bonding and tauto-
merism (Schemes 1 and 2) in those compounds. As
can be seen from Fig. 4 the asymmetric unit includes
both the tautomeric forms at 50% abundance in the
crystalline state.
[28,32,33,35]. The hydrogen bond type depends
neither on the stereochemistry of the molecule nor
on the sort of the substituent to the imine (N) atom,
but on the kind of aldehyde used [32]. The UV–
visible spectra of some 2-hydroxy Schiff bases were
also studied in polar and non-polar solvents [1,16]. In
polar solvents, a new band at Ͼ400 nm was observed,
which is not found in non-polar solvents. The results
indicate that the absorption band at 400 nm belongs
Fig. 1. Solvent effect on compound (2). DMSO —, ethanol - - -;, chloroform - × - × -, benzene -O-O, cyclohexane -W-W-, Schiff base
Ϫ5
Ϫ3
concentration 5 × 10 mol dm
:

H. Nazır et al. / Journal of Molecular Structure 524 (2000) 241–250
243
Fig. 2. Acid effect on compound (2). DMSO —, ethanol - - -, chloroform - × - × -, benzene -O-O, CF
3
COOH, pH: 2.
Fig. 3. Base effect on compound (2). DMSO —, ethanol - - -, chloroform - × - × -, benzene -O-O, cyclohexane -W-W-, (C
2 5 3
H ) N, pH: 9.

2
44
H. Nazır et al. / Journal of Molecular Structure 524 (2000) 241–250
Fig. 4. An ORTEP [41] drawing of the title molecule with the atom-numbering scheme.
2. Experimental
for 1 h. Compound (1) was obtained after the evapora-
tion of THF, as a yellow solid m.p. 65ЊC, 1.50 g (76%)
yield. Found: C, 72.94; H, 5.11; N, 14.16; calc. for
C H N O; C, 72.72; H, 5.05; N, 14,14%. IR (KBr,
2
.1. Reagents and techniques
1
2
10
2
1
Ϫ1
The H NMR spectra were recorded on a Bruker
cm ): n (Ar–H) 3059 m, n (C–H)2929 w), n(O–H)
1
DPX FT-NMR spectrometer operating at 400 MHz.
The proton shifts were measured using SiMe as an
2
719 w, n (CyN) 1612 s, n (CyC) 1600 s. H NMR
4
(CDCl ): d ppm; 13.44(s, 1H, OH), 9.45 (s, 1H,
3
internal standard. Infrared absorption spectra were
obtained from a Mattson 1000-FTIR spectrometer in
KBr discs and were reported in cm units. UV–
–
CHyNy), 7.79–6.94 (m, 8H, Arom-H).
Ϫ1
2
.2.2. Synthesis of N-(2-pyridil)-2-oxo-1-
naphthylidenemethylamine (2)
-Hydroxy-1-naphthaldehyde (1.72 g, 0.01 mol)
visible spectra were measured using a UNICAM
UV2-100 series spectrometer. Carbon, nitrogen and
hydrogen analyses were performed on a LECO
CHNS-932 C-, H-, N- analyzer. Melting points were
measured on a Gallonkamp apparatus using a capil-
lary tube, chloroform, THF, Benzene, EtOH, cyclo-
hexane, DMSO, light petroleum ether (b.p. 50–70ЊC)
were purchased from Merck (Germany).
2
was added to a dry THF (100 ml) solution of 2-amino-
pyridine (0.94 g, 0.01 mol). The mixture was stirred
and heated for 1 h. Compound (2) was obtained from
the evaporation of THF [36]. It was crystallized from
(CHCl /petroleum ether (50–70)) by the slow-diffu-
3
sion method as a yellow solid, m.p. 174ЊC, 2.0 g
81%) yield. Found: C, 76.90; H, 4.97; N, 11.32.
C H ON ; C, 77.42; H, 4.84; N, 11.29%. IR (KBr,
(
2
2
.2. Synthetic procedures
1
6
12
2
Ϫ1
.2.1. N-(2-pyridil)-salicylidene) (1)
cm ): n (Ar–H) 3061 m, n (CyN) 1620 s, n (CyC)
1600, n (C–O) 1473 s, 1321 s. H NMR (CDCl ); d
1
Salicylaldehyde (1.22 g, 0.01 mol) was added to a
3
dry THF (100 ml) solution of 2-amino pyridine
0.94 g, 0.01 mol). The mixture was stirred and heated
ppm, 15.41 (s, 1H, OH); 15.45 (broad, OH) [36];
9.95(d, 1H, CHyN, JNHCH ˆ 7:04 Hz†; 9.99(d,
3
(

H. Nazır et al. / Journal of Molecular Structure 524 (2000) 241–250
245
Table 1
Experimental data
Experimental data, methods and the procedures used
to elucidate the structure and other related parameters
are given in Table 1. The structure was solved by the
Direct method, Simpel-MoIEN [37]. All non-H atoms
were refined with anisotropic thermal parameters. H
atoms were placed in naphthyl geometrically at
Compound
Color/shape
For. Wt.
Space group
Temperature (K)
Cell constants
32 24 4 2
C H N O
Dark brown/needle
496.57
Monoclinic, P2 =n
295
1
˚
0
.95 A from their corresponding C atoms. For all H
a ˆ 5:837ꢀ2†; b ˆ 17:476ꢀ2†;
ꢀ
atoms a riding model was used with U ꢀH† ˆ
iso
c ˆ 24:295ꢀ3† A; b ˆ 91:95ꢀ4†Њ
3
˚
1:3U ꢀC; N; O†:
Cell volume (A )
Formula units/unit cell
D calc (mg m
m calc (mm
2476.9(6)
eq
4
Ϫ3
)
1.332
0.079
Ϫ1
)
3. Results and discussion
Diffractometer/scan
Radiation used, graphite
monochromator
Max. crystal dimen. (mm)
Standard reflections
Decay of standard
Reflections measured
u (max) (Њ)
Enraf-nonius CAD-4/w-2u
MoKa ꢀl ˆ 0:71073 Aꢀ †
1
3
.1. IR and H NMR spectroscopies
3
30 :35 × 0:15 × 0:10 mm
The n (CyN) absorbtion bands were observed at
612 and 1620 cm for compounds (1) and (2) as
in ArCHyNAr [32,38]. The observation of phenolic
n (C–O) at 1321 cm for (2) is the evidence for the
existence of the keto–amine form (N–H···O) intra-
molecular hydrogen bonding only in the solid state.
The stretching frequency observed at 2719 cm in
(1) shows the presence of O–H···N intramolecular
hydrogen bond, which is in agreement with the
Ϫ1
1
Ϫ0.59
3844
23.57
Ϫ1
Range of h, k, l
0 Ͻ h Ͻ 6; 0 Ͻ k Ͻ 19; Ϫ27 Ͻ
l Ͻ 27
2118
No. of reflections with I Ͼ
Ϫ1
1=sꢀI†
Corrections applied
Computer programs
Source of atomic scattering
factor
Lorentz-polarization
MoIEN[37]ORTEP(II)[41]
Ref. [42]
1
reported values in the literature [38]. H NMR data
for compound (1) shows that the tautomeric equili-
brium favors the phenol–imine in CDCl3 ꢀd ˆ
13:44 ppm; singlet for OH; d ˆ 9:45 ppm; singlet
for –CHyN–). The compound (2) shifts to the keto–
Structure solution
Treatment of hydrogen atoms
Direct method
calculated geometrically and a
riding model was used
343
No. of parameters var.
GOF
1.33
amine form in the CDCl ꢀd ˆ 15:41 ppm; singlet for
3
R ˆ ʈFo͉ Ϫ ͉Fcʈ=͉Fo͉
0.054
0.049
0.247
Ϫ0.195
3
OH; d ˆ 9:95 ppm; doublet, J
ˆ 7:04 Hz†:
NHCH
Rw
Ϫ3
˚
˚
ꢀ
D=r† max (e A
)
Ϫ3
3.2. UV–visible spectroscopy
ꢀ
D=r† min (e A
)
The UV–visible spectra of compounds (1) and (2)
were studied in polar and non-polar solvents both in
acidic and basic media. Table 2 gives the calculated
keto–amine form. Figs. 1–3 show the UV spectra of
compound (2) in different solvents both in acidic and
basic media. Compound (1) did not show any absorp-
tion above 400 nm in DMSO, EtOH, chloroform,
benzene and cyclohexane. However, for compound
(2), a new band was observed at Ͼ400 nm in the
same solvents (Fig. 1). The band was observed at
3
CHyN, J
ˆ 7:0 Hz† [36]; 8.50–6.87 (m, 10H,
NHCH
Arom-H).
2
.3. Crystallography
The crystals suitable for X-ray analysis were
obtained by recrystallization from (CHCl /petroleum
3
ether (50–70)) by slow-diffusion method. Probably
due to the fact that the crystallization medium was a
mixture and that the rates of evaporation of the two
liquids were different, a careful control of the crystal-
lization process has proven to be difficult. The result
was minute crystals not perfectly suitable for X-ray
studies and attempts to grow better sizes failed.
Ͼ400 nm in acidic (CF COOH, pH ˆ 2† solutions
3
of chloroform and benzene and basic ((C H ) N,
2
5 3
pH ˆ 9† solutions of DMSO, EtOH, chloroform,
benzene and cyclohexane for compound (2) (Figs. 2
and 3) but it is not observed in acidic and basic solutions

2
46
H. Nazır et al. / Journal of Molecular Structure 524 (2000) 241–250
Table 2
Effect of solvent, acid and base on the UV spectra of compounds (1) and (2)
Ϫ1
Ϫ1
Compound
Solvent
l, nm (e, M cm
)
Keto–amine isomer (%)
a
b
Solvent media
–
Acidic media
–
Basic media
–
(1)
DMSO
EtOH
256(3200),270(3500)
08(3900),346(3400)
226(550),272(240)
04(300),346(250)
240(5600),270(5700)
06(6600),350(5700)
224(4700),234(6400,
3
–
–
–
–
–
–
3
CHCl
3
3
Benzene
–
–
–
–
–
–
2
3
70(6300),306(8200),
54(7700)
Cyclohexane
228(4200),268(3800)
04(5000),352(4400)
–
–
–
3
(2)
DMSO
EtOH
316(3100),436(3900)
58(3800)
314(800),434(110)
58(110)
318(5300),436(7700)
58(7800)
322(700),412(900)
34(520)
322(5100),396(6300)
58(3000)
63
63
62
57
52
–
67
68
72
61
70
4
–
4
CHCl
3
68
75
4
Benzene
4
c
Cyclohexane
Not measured
4
a
b
c
CF
(C H )
2 5 3
3
COOH, pH:2.
N, pH:9.
Not mixtured cyclohexane and acid.
of the same solvents for compound (1). In Schiff bases
derived from salicylaldehyde and aniline this new band at
Ͼ400 nm was observed only in acidic media [1,16].
The molar extinction (e) coefficients of the bands in
the range of 222–354 nm for compound (1) can be
DMSO, EtOH, chloroform, benzene and cyclohexane.
On the contrary, keto–amine tautomer was increased
by 6, 7, 8, 16, 57% and 6, 32%, respectively in the
basic solutions of DMSO, benzene, EtOH, chloro-
form, cyclohexane and in the acidic solutions of
chloroform and benzene with respect to the pure
solvent media. Absence of keto–amine form in the
acidic solutions of DMSO and ethanol may be
ordered
as
EtOH Ͻ DMSO Ͻ cyclohexane Ͻ
chloroform Ͻ benzene. However, for compound (2),
the extinction coefficients are ordered as ethanol Ͻ
benzene Ͻ cyclohexane Ͻ DMSO Ͻ chloroform for
bands above 400 nm and as benzene Ͻ EtOH Ͻ
DMSO Ͻ chloroform Ͻ cyclohexane for bands in
the range of 318–396 nm. The bathochromic shifts
both above and below 400 nm in all of the solvents
studied (DMSO, EtOH, chloroform, benzene and
cyclohexane) do not depend on solvent polarities for
compound (1) and (2). Phenol–imine tautomer is
dominant only in the acidic solutions of DMSO and
ethanol for compound (2), while for compound (1) it
is dominant in both acidic and basic solutions of
explained by the hydrogen bonding to CF COOH.
3
3
.3. Crystal study
Single crystal X-ray structure of compound (2) is
reported to further corroborate the structure assign-
ments. The final coordinates and equivalent isotropic
displacement parameters are given in Table 1. The
molecular structure with the atom-numbering scheme
is shown in Fig. 4. The atomic coordinates and
equivalent isotropic displacement parameters are

H. Nazır et al. / Journal of Molecular Structure 524 (2000) 241–250
247
Table 3
Atomic coordinates and equivalent isotropic displacement parameters with e.s.d.s in parentheses (starred atoms were refined isotropically).
Anisotropically refined atoms are given in the form of the isotropic equivalent displacement parameter defined as: ꢀ4=3† × ‰a2 × Bꢀ1; 1† ϩ b2 ×
Bꢀ2; 2† ϩ c2 × Bꢀ3; 3† ϩ abꢀcos gamma† × Bꢀ1; 2† ϩ acꢀcos beta† × Bꢀ1; 3† ϩ bcꢀcos alpha† × Bꢀ2; 3†Š
2
˚
Atom
X
Y
Z
B (A )
O1
O1
N1
N1
N2
N2
C1
C1
C2
C2
C3
C3
C4
C4
C5
C5
C6
C6
C7
C7
C8
C8
C9
C9
C10
C10
C11
C11
C12
C12
C13
C13
C14
C14
C15
C15
C16
C16
H1
H1
H3
H3
H4
H4
H6
H6
H7
H7
0.4177(4)
0.8327(5)
0.6662(5)
1.0960(5)
0.8906(5)
1.3427(5)
0.3531(6)
0.7760(6)
0.3024(6)
0.7117(7)
0.1115(6)
0.5034(7)
Ϫ0.0185(6)
0.3713(7)
0.0235(6)
0.4305(6)
Ϫ0.1198(7)
0.2910(7)
Ϫ0.0791(7)
0.3514(7)
0.1062(7)
0.5492(7)
0.2468(7)
0.6897(7)
0.2096(6)
0.6335(6)
0.5336(6)
0.9676(6)
0.8531(6)
1.2870(6)
1.0745(6)
1.5318(7)
1.2190(7)
1.6615(7)
1.1723(7)
1.5976(7)
0.9857(6)
1.4097(7)
0.635
0.0652(1)
0.0929(1)
0.1379(2)
0.0545(2)
0.2062(2)
0.0226(2)
0.1956(2)
1.04873(9)
1.2131(1)
0.9798(1)
1.2926(1)
0.9197(1)
1.3672(1)
1.0259(1)
1.2641(1)
1.0547(1)
1.2227(1)
1.0905(1)
1.1905(1)
1.0960(1)
1.1987(1)
1.0675(1)
1.2377(1)
1.0735(1)
1.2430(1)
1.0468(1)
1.2790(1)
1.0127(2)
1.3104(2)
1.0056(1)
1.3062(1)
1.0327(1)
1.2700(1)
0.9908(1)
1.2980(1)
0.9449(1)
1.3268(1)
0.8883(1)
1.3978(2)
0.8807(1)
1.3904(2)
0.9070(1)
1.3484(2)
0.9394(1)
1.3157(2)
0.995
4.92(6)
5.92(7)
3.84(7)
4.01(7)
4.22(7)
5.36(8)
3.30(8)
3.52(8)
3.82(8)
4.57(9)
4.09(9)
5.2(1)
0
0
0
0
Ϫ0.0217(2)
0.1256(2)
0.0337(2)
0.1270(2)
0.0234(2)
0.1893(2)
Ϫ0.0381(2)
0.2594(2)
Ϫ0.0964(2)
0.3231(2)
Ϫ0.1608(2)
0.3897(2)
Ϫ0.2187(2)
0.3942(2)
0.2123(2)
0.3328(2)
Ϫ0.1496(2)
0.2634(2)
Ϫ0.0896(2)
0.1976(2)
Ϫ0.0068(2)
0.1407(2)
0.0703(2)
0.2083(2)
0.0406(2)
0.1476(2)
0.1056(2)
0.0803(2)
0.1534(2)
0.0760(2)
0.1366(2)
0.099
0
0
4.15(8)
5.1(1)
0
3.54(8)
3.96(8)
4.67(9)
5.01(9)
5.4(1)
5.5(1)
5.4(1)
5.3(1)
4.60(9)
4.62(9)
3.56(8)
3.61(8)
3.60(8)
4.05(9)
3.50(8)
4.17(9)
4.96(9)
6.5(1)
5.00(9)
6.4(1)
4.82(9)
6.2(1)
4.11(9)
5.2(1)
0
0
0
0
0
0
0
0
0
0
0
0
ء
4.5
7.4
5.3
6.9
5.5
6.6
6.1
6.5
7.0
7.1
7.2
7.0
0
ء
0.938
0.079
0.459
Ϫ0.145
0.231
Ϫ0.248
0.152
Ϫ0.176
0.257
0.136
0.591
0.372
0.104
0.082
0.060
0.187
Ϫ0.042
0.319
Ϫ0.165
0.433
Ϫ0.263
0.441
Ϫ0.252
0.338
1.237
1.111
1.163
1.120
1.178
1.096
1.222
1.051
1.282
0.994
1.336
0.982
ء
0
ء
ء
0
ء
ء
0
ء
ء
0
ء
ء
H8
H8
H9
0
ء
ء
6.0

2
48
H. Nazır et al. / Journal of Molecular Structure 524 (2000) 241–250
Table 3 (continued)
2
˚
Atom
X
Y
Z
B (A )
0
ء
H9
0.827
0.569
1.005
1.106
1.578
1.348
1.792
1.269
1.684
0.948
1.364
Ϫ0.147
0.244
Ϫ0.043
0.225
0.007
0.152
0.116
0.037
0.198
0.030
0.169
1.328
0.973
1.326
0.870
1.427
0.858
1.414
0.903
1.342
0.957
1.286
6.1
4.9
5.1
6.6
8.6
6.4
8.3
6.2
ء
H11
H11
H13
H13
H14
H14
H15
H15
0
ء
ء
0
ء
ء
0
ء
ء
0
ء
8.3
5.2
6.8
ء
H16
H16
0
ء
Table 4
˚
Bond lengths (A), bond angles (Њ) and torsion angles (Њ)
0
0
0
0
0
O1 –C2
1.279(4)
1.330(4)
1.406(4)
1.317(4)
1.395(4)
1.320(4)
1.338(5)
1.320(4)
1.347(5)
1.445(4)
1.463(5)
1.380(5)
1.436(5)
1.459(5)
1.392(5)
1.438(5)
1.434(5)
1.341(5)
1.402(5)
1.400(5)
C12 –C16
1.394(5)
N1–C11
N1–C12
C13–C14
1.372(5)
1.380(6)
1.336(5)
1.432(4)
1.426(5)
1.403(5)
1.401(5)
1.397(5)
1.403(5)
1.376(5)
1.358(5)
1.367(5)
1.386(6)
1.365(5)
1.375(5)
1.372(5)
1.361(5)
1.367(5)
1.364(5)
0
C13 –C14
0
0
0
0
N1 –C11
C3–C4
C4–C5
C4 –C5
C5–C6
C5–C10
C5 –C6
C5 –C10
C6 –C7
C6–C7
N1 –C12
0
0
N2–C12
N2–C13
0
0
0
0
N2 –C12
0
0
0
N2 –C13
0
C1–C2
0
0
0
C1–C10
C1–C11
0
0
0
C1 –C2
C7 –C8
C7–C8
C8–C9
0
0
0
0
C1 –C10
C1 –C11
0
0
C2–C3
C8 –C9
0
0
0
C2 –C3
C14–C15
0
0
0
0
C3 –C4
C14 –C15
0
0
C9 –C10
C9–C10
C15–C16
0
C15 –C16
0
0
0
0
0
0
0
C11 –N1 –C12
C12–N2–C13
123.2(3)
C3 –C4 –C5
C4–C5–C6
C4–C5–C10
C6–C5–C10
122.9(3)
115.9(3)
116.1(3)
120.3(3)
119.6(3)
120.1(3)
118.7(3)
118.4(3)
122.9(3)
122.3(3)
120.8(3)
117.0(3)
122.7(3)
121.0(3)
118.9(3)
120.1(3)
120.5(3)
119.4(3)
120.1(3)
120.9(3)
121.0(3)
119.2(3)
117.5(3)
122.7(3)
124.5(3)
0
0
C12 –N2 –C13
C2–C1–C10
C2–C1–C11
C10–C1–C11
0
0
0
0
0
0
0
0
0
C4 –C5 –C6
0
0
C4 –C5 –C10
0
0
0
0
0
0
C2 –C1 –C10
C6 –C5 –C10
0
C2 –C1 –C11
C5 –C6 –C7
C5–C6–C7
0
0
0
C10 –C1 –C11
O1–C2–C1
O1–C2–C3
C1–C2–C3
0
0
0
C6 –C7 –C8
C5–C10–C9
0
0
0
N1 –C11 –C1
N1–C11–C1
0
0
0
O1 –C2 –C1

H. Nazır et al. / Journal of Molecular Structure 524 (2000) 241–250
249
Table 4 (continued)
0
0
0
0
0
0
0
0
0
O1 –C2 –C3
117.7(3)
119.6(3)
120.0(3)
119.2(3)
121.0(3)
121.2(3)
121.1(3)
121.2(3)
119.2(3)
123.3(3)
117.5(3)
119.1(3)
123.4(39)
122.0(3)
122.8(3)
N1–C12–N2
N1–C12–C16
N2–C12–C16
117.0(3)
118.7(3)
124.3(3)
119.3(3)
117.1(3)
123.6(3)
124.4(3)
124.3(4)
117.8(3)
117.7(4)
119.3(3)
120.0(4)
118.2(3)
118.3(3)
C1 –C2 –C3
C2 –C3 –C4
C6–C7–C8
C7–C8–C9
0
0
0
N1 –C12 –N2
0
0
0
0
0
0
N1 –C12 –C16
0
0
0
0
0
C7 –C8 –C9
N2 –C12 –C16
N2–C13–C14
0
C8 –C9 –C10
C8–C9–C10
0
0
0
N2 –C13 –C14
C13–C14–C15
0
0
0
0
0
0
0
0
0
C1 –C10 –C5
0
0
0
0
0
C1 –C10 –C9
C13 –C14 –C15
C14–C15–C16
C14 –C15 –C16
C12–C16–C15
C5 –C10 –C9
C1–C10–C5
C1–C10–C9
C2–C3–C4
C3–C4–C5
0
0
0
0
C12 –C16 –C15
C12–N1–C11–C1
C11–N1–C12–N2
C11–N1–C12–C16
Ϫ178.53(0.29)
Ϫ3.18(0.44)
176.28(0.30)
179.39(0.31)
Ϫ0.95(0.48)
178.92(0.31)
177.84(0.29)
Ϫ0.29(0.49)
Ϫ176.67(0.31)
5.45(0.50)
0
0
0
0
0
C12 –N1 –C11 –C1
0
0
0
0
0
0
C11 –N1 –C12 –N2
0
C11 –N1 –C12 –C16
C10–C1–C2–O1
C11–C1–C2–O1
0
0
0
0
C10 –C1 –C2 –O1
0
0
0
C11 C1 C2 O1
˚
˚
given in Table 3 and the bond lengths and angles with
some selected torsion angles are given in Table 4. The
structure of the Schiff base ligand (2) is the same both
in solid state and in solution. Phenol–imine and keto–
amine forms do exist in the solid state. When the
phenol–imine form is transformed into the keto–
amine form, an appreciable increase in the CyN
bond angles are (1.317(4) A; 1.330(4) A) and
˚
(124.2(3)Њ; 123.2(3)Њ) compared with 1.313(8) A and
122.5(6)Њ values in (C H NO) [39]. The degrees of
1
4
15
planarity for the two molecules in the asymmetric unit
are different. Least squares plane calculations show
that the keto–amine type molecule as a whole is prac-
tically planar. In contrast, the phenol–imine structure
is not quite as planar with a maximum dihedral angle
of 5.5(9)Њ between the moieties of the molecule. The
intramolecular hydrogen bonds between (N···H–O;
N–H···O) for the two different forms are rather
0
0
˚
distance is observed ((C11 yN1 1.317(4) A versus
˚
C11–N1:1.330(4) A). However, in naphthaldimine
derivatives, only the keto–amine form is dominant
as in (N-(a-naphtyl)-2-oxo-1-naphthaldimine) (N–
O: 2.536, N–H: 0.851) [32] and (N-n-propyl-2-oxo-
0
˚
short as expected (N1–O1: 2.586(4) A and N1 –
O1 : 2.518(4) A) with respective angles of 137.09(4)
0
˚
1
0
-naphthylidenemethylamine) (N–O: 2.578(2), N–H:
˚
.775, H···O: 1.936 A) [33]. A concomitant decrease
and 136.06(4)Њ.
0
0
in the C–O distance is also noted ((C2 –O1 :
˚
˚
1.279(4) A; C2–O1: 1.263(4) A). The corresponding
bond lengths in (C H NO) and (C H NO) are
Acknowledgements
1
4
˚
15
15 17
1.23(1) and 1.254(8) A, respectively [39,40]. In the
solid state, the shortening in the C–O bond length
can be explained by the quinoidal structure (keto–
amine form) as in the 2-hydroxy-1-naphthaldimine
derivatives [32]. The CyN imine bond and C–N–C
The authors wish to acknowledge the purchase of
CAD-4 diffractometer under Grant DPT/TBAG1 of
the Scientific and Technical Research Council of
Turkey.

2
50
H. Nazır et al. / Journal of Molecular Structure 524 (2000) 241–250
References
[23] M. Ottolenchi, D.S. Mc, Clure, J. Chem. Phys. 46 (1967)
620.
24] A.A.H. Saeed, S.A.W. Othman, K.A. Al-jalil, A.T. Atto, Can.
4
[
[
[
1] M. Yildiz, Z. Kili c, , T. H o¨ kelek, J. Mol. Struct. 441 (1998) 1.
2] D.P. Kessisoglu, C.P. Raptopoulou, E.G. Bakalbassis, A.
Terzis, J. Mrozinski, Inorg. Chem. 31 (1992) 4339.
J. Chem. 26 (1980) 39.
[25] M. Allen, J.D. Roberts, J. Org. Chem. 45 (1980) 130.
[26] G.O. Dudek, R.H. Holm, J. Am. Chem. Soc. 84 (1962) 2692.
[27] P. Teyssie, J. Charette, Spectrochim. Acta 19 (1963) 1275.
[28] G.O. Dudek, E.P. Dudek, J. Am. Chem. Soc. 88 (1966) 2407.
[29] G.C. Percy, D.A. Thornton, J. Inorg. Nucl. Chem. 34 (1972)
[3] S.C. Bhatia, J.M. Bindlish, A.R. Saini, P.C. Jain, J. Chem.
Soc., Dalton Trans. (1981) 1773.
[
4] M. Calligaris, G. Nardin, L. Randaccio, Coord. Chem. Rev. 7
(1972) 385.
3357.
[
[
[
[
5] H.S. Maslen, T.N. Waters, Coord. Chem. Rev. 17 (1975) 137.
6] J. Stewart, E.C. Lingafelter, Acta Crystallogr. 12 (1959) 842.
7] D. Chen, A.E. Martel, Inorg. Chem. 26 (1987) 1026.
[
[
[
30] S.R. Salman, J.C. Lindon, R.D. Farrant, T.A. Carpenter,
Magn. Reson. Chem. 31 (1993) 991.
31] R.D. Salman, R.D. Farrant, J.C. Lindon, Spectrosc. Lett. 24
8] J.W. Pyrz, A.L. Roe, L.J. Stern, L. Que Jr., J. Am. Chem. Soc.
(
9) (1991) 1071.
32] M. Gavranic, B. Kaitner, E. Mestrovis, J. Chem. Crystallogr.
6 (1996) 23.
1
07 (1985) 614.
[9] J. Costamagna, J. Vargas, R. Latorre, A. Alvarado, G. Mena,
2
Coord. Chem. Rev. 119 (1992) 67.
[
[
33] B. Kaitner, G. Pavlovic, Acta Crystallogr. C 52 (1996) 2573.
34] O. Atakol, A. Kenar, M. Kabak, Synth. React. Inorg. Met.-
Org. Chem. 27 (1) (1997) 29.
[
[
[
[
10] N.E. Dixon, C. Gazzalo, J.J. Watters, R.L. Blakeley, B.
Zerner, J. Am. Chem. Soc. 97 (1975) 4131.
11] C.T. Walsh, W.H. Orme-Johnson, Biochemistry 26 (1987)
[
[
35] J.W. Ledbetter, J. Phys. Chem. 81 (1977) 54.
36] H. Ranganathan, D. Ramaswamy, T. Ramasami, M. Santappa,
Chem. Lett. (1979) 1201.
4
901.
12] D.E. Hamilton, R.S. Drago, A. Zombeck, J. Am. Chem. Soc.
09 (1987) 374.
13] Y. Nishida, K. Kino, S. Kida, J. Chem. Soc., Dalton Trans.
1987) 1157.
1
[
37] C.K. Fair, MoIEN, An Interactive Intelligent System for
Crystal Structure Analysis, Enraf-Nonius, Delft, The Nether-
lands, 1990.
(
[14] J.W. Ledbetter Jr., J. Phys. Chem. 81 (1977) 54.
[15] J.W. Lewis, C. Sandorfy, C. an, J. Chem. 6 (1982) 1727.
[16] S.R. Salman, S.H. Shawkat, G.M. Al-Obaidi, Can. J. Spec-
trosc. 35 (1990) 25.
[38] H.H. Freedman, J. Am. Chem. Soc. 83 (1961) 2900.
[39] T. H o¨ kelek, N. G u¨ nd u¨ z, Z. Hayvali, Z. Kili c, , Acta Crystallogr.
C 51 (1995) 880.
[
[
[
17] M.D. Cohen, S. Flavian, J. Chem. Soc. B (1967) 317.
18] M.D. Cohen, S. Flavian, J. Chem. Soc. B (1967) 321.
19] J. Charette, G. Faltlhansl, P.H. Tyssie, Spectrochim. Acta 20
[40] T. H o¨ kelek, N. G u¨ nd u¨ z, Z. Hayvali, Z. Kili c, , J. Chem. Crys-
tallogr. 25 (1995) 831.
[41] C.K. Johnson, ORTEP II, Report ORNL-5138, Oak Ridge
National Laboratory, TN, 1976.
(1964) 597.
[20] J.W. Ledbetter Jr., J. Phys. Chem. 70 (1966) 2245.
[21] J.W. Ledbetter Jr., J. Phys. Chem. 71 (1967) 2351.
[22] P.W. Alexander, R.J. Sleet, Austral. J. Chem. 23 (1970) 1183.
[42] International Tables For X-ray Crystallography, vol. 4,
Kluwer Academic Publishers, Dordrecht, Kynoch Press,
Birmingham, 1974.