Characterisation of novel macroacyclic hexadentate (n4o 2 and n2o4)schiff base ligands and their zinc(ii), copper(ii) and cobalt(II) complexes with ligands derived from reduction

Article abstract of DOI:10.3184/030823409X457528

themacrocyclic, hexadentate (N₄O₂ and N ₂O₄) Schiff base ligands, 1,2-bis(2'-nitrophenoxy)benzene, 1,2-bis (2'-nitrophenoxy)-4-t-butylbenzene), 1,2-bis(2'-aminophenoxy)benzene and 1,2-bis Zinc(II), copper(II) an

Full text of DOI:10.3184/030823409X457528

JOURNAL OF CHEMICAL RESEARCH 2009
JUNE, 361–365
RESEARCH PAPER 361
Characterisation of novel macroacyclic hexadentate (N4O2 and N2O4)
Schiff base ligands and their zinc(II), copper(II) and cobalt(II) complexes,
with ligands derived from reduction
Hassan Keypoura*, Hadi Amiri Rudbaria, Reza Azadbakhtb and Ebrahim Abouzari Lotfc
aFaculty of Chemistry, Bu-Ali Sina University, Hamedan, Iran
bDepartment of Chemistry, Payame Noor University, Hamedan, Iran
cDepartment of Chemistry, Tarbiat Moalem University, Tehran, Iran
The macrocyclic, hexadentate (N4O2 and N2O4) Schiff base ligands, 1,2-bis(2'-nitrophenoxy)benzene, 1,2-bis
(2'-nitrophenoxy)-4-t-butylbenzene), 1,2-bis(2'-aminophenoxy)benzene and 1,2-bis(2'-aminophenoxy)-4-t-butyl-
benzene have been synthesised, together with macroacyclic hexadentate ligands formed from their reduction.
Zinc(II), copper(II) and cobalt(II) complexes of the Schiff base ligands have also been prepared and all compounds
have been characterised by spectroscopy and elemental analysis.
Keywords: ortho-aminophenyl diamines, Schiff-base ligands, complexes, reduction
The chemistry of metal complexes with chelate ligands
containing nitrogen or oxygen donors has been studied
extensively in order to mimic the redox function of various
metalloenzymes in living systems and the formation and
reactivity of dioxygen in synthetic, industrial and biological
processes. In enzymes, metal ions have several functions:
(i) redox as in superoxide dismutase-like activity;1-6 and (ii)
structural and catalytic.7-11 The complexation sites of these
proteins are often N or O donors. Therefore, for many years
there has been great interest in the study of metal complexes
of bulky polydentate ligands that are able to mimic the active
sites of metalloproteins. We have prepared and characterised
four novel macroacyclic Schiff-base ligands derived from
diamines with 2-pyridinecarboxaldehyde and salicylaldehyde.
Compounds L5, L6, H2L7 and H2L8 were prepared by the
reduction of Schiff base ligands. During the course of this
work, we have prepared and characterised Co2+, Cu2+ and
Zn2+ complexes of L1, L2 and H2L3 ligands, and Co2+ and
Cu2+ complexes of the H2L4 ligand. The diamines 1,2-bis
(2'-aminophenoxy)benzene (3) and 1,2-bis(2'-aminophenoxy)-
4-t-butylbenzene (4) were synthesised by the reaction of
diols (catechol or 4-tert-butylcatechol) with 1-fluoro-2-
nitrobenzene in the presence of potassium carbonate (K2CO3)
under a dinitrogen atmosphere, and then reduced by zinc dust
and ammonium chloride.
H2O/MeOH.14 After reduction, the characteristic absorptions
of nitro groups disappeared and the amino groups showed NH
stretching bands at 3426, 3408, 3313 cm-1 and 3461, 3405,
3376, 3304 cm-1 for (3) and (4), respectively. In the 1H NMR
spectra, all the aromatic protons of (3) and (4) resonated in the
7–6.6 ppm and 7.2–6.6 ppm region, respectively. Hydrogens of
the t-butyl group appeared at 1.3 ppm and the signal appearing
at 3.7 ppm corresponds to the amine group. Comparing the 13
C
NMR spectra of (3) and (4) with the spectra of the precursors
(1) and (2), the 13C absorptions of the central three benzene
rings move downfield as a result of the change to the electron-
donating amino groups from the electron-withdrawing nitro
groups.12,13
Schiff base ligands
The Schiff base ligands (L1, L2, H2L3 and H2L4)
were prepared by condensation of the diamines with
2-pyridinecarboxaldehyde and salicylaldehyde in a 1:2 ratio
(Fig. 1). The reactions are almost quantitative and produce
yellow solids that are soluble in common organic solvents.
L1, L2 are unstable in air but H2L3 and H2L4 are stable in air.
The chemical structures of the L1, L2, H2L3 and H2L4 ligands
1
were confirmed by elemental analysis and IR, H and 13C
NMR spectroscopies, with results in good agreement with the
designed compounds. The formation of Schiff base ligands is
evidenced by the presence of a strong IR band at ~1639 cm-1
for L1, L2 and a strong band at ~1618 for H2L3 and H2L4, due
to n(C=N), while no bands attributable to n(C=O) or to n(NH2)
have been detected. For L1, L2 ligands the bands at 1600 and
1488 cm-1 of the pyridine ring vibrations are also present.5
The 1H NMR spectra are consistent with the IR spectroscopy.
Results and discussion
Bis(nitrophenoxy)benzenes
1,2-Bis(2'-nitrophenoxy)benzene (1) and 1,2-bis(2'-nitro-
phenoxy)-4-t-butylbenzene (2) were prepared by an SNAr
reaction between 1-fluoro-2-nitrofluorobenzene and simple
aromatic diols (catechol and 4-tert-butylcatechol). The IR
spectrum of (1) and (2) reveals absorption bands at ca 1348
and 1524 cm-1 due to symmetric and asymmetric stretching of
the -NO2 group.12,13 In the 1H NMR spectrum, the absorption
signals of aromatic protons of (1) and (2) appear in the region
of 6.9–8 and ppm 6.8–7.8, respectively, and the butyl group
of (2) appears at 1.3 ppm. 20 main peaks are expected in the
13C NMR spectrum of (2), but only 16 main signals appeared
because of overlap of carbon resonances. The 13C NMR of (1)
showed the expected nine aromatic signals.
1
The H NMR spectra in CDCl3 show a peak at ~9.3 ppm for
L1, L2 and at ~8.5 ppm for H2L3 and H2L4 corresponding to
the imine protons.16,17
Complexes
The prepared complexes are stable in air. The elemental
analysis, yield, IR and FAB mass data of the complexes are
compared in Tables 1, 2 and 3. The presence of n(C=N) bands
in the correct positions for Schiff base linkages of this kind,
and the absence of C=O and NH2 indicate that the required
macroacyclic Schiff base complexes have indeed formed.18
For complexes containing 2-pyridinecarboxaldehyde, all
the spectra exhibit medium to strong bands at ~1597 and
1485 cm-1 as expected for the two highest energy pyridine-
ring vibrations. The shift of the imine and pyridine bands to
lower wavenumbers by complexation suggests coordination
via the imine and pyridine nitrogen atoms.19,20 For the
Bis(aminophenoxy)benzenes
Aromatic nitro compounds can be reduced in high yield to
the corresponding diamines using zinc metal and NH4Cl in
* Correspondent. E-mail: haskey1@yahoo.com

362 JOURNAL OF CHEMICAL RESEARCH 2009
HO
OH
O2N
2
F
+
R
O2N
NO2
O
O
R=H
(1)
R
R=C(CH3)3 (2)
NH2
H2N
O
R
O
R=H
(3)
(4)
R=C(CH3)3
H
H
O
N
O
HO
OH
OH
N
N
N
N
N
N
O
R
O
O
R
O
R=H
L1
R=H
H2L3
R=C(CH3)3 L2
R=C(CH3)3 H2L4
OH
N
N
OH
NH
NH
HN
NH
O
O
O
R
O
R=H
L5
R=H
H2L7
R
R=C(CH3)3 L6
R=C(CH3)3 H2L8
Fig. 1 Synthetic route used for the preparation of (1, 2, 3 and 4) compounds, and ligands.

JOURNAL OF CHEMICAL RESEARCH 2009 363
Table 1 Elemental analysis (%) and yield of the complexes
Complex
Formula
C
H
N
Yield/%
[Co(L1)](NO3)2.H2O
[Cu(L1)](ClO4)2.H2O
[Zn(L1)](NO3)2.2CH3CH2OH
[Co(L2)](NO3)2.1.5H2O
[Cu(L2)](ClO4)2.2H2O
[Zn(L2)](NO3)2.2CH3OH
[CoL3].0.5CHCl3
C30H24CoN6O9
53.7(53.7)
48.1(48.0)
54.4(54.3)
55.3(55.4)
49.4(49.5)
55.4(55.4)
63.2(63.25)
66.6(66.7)
68.1(68.2)
60.7(60.6)
67.0(66.9)
3.5(3.6)
3.3(3.2)
4.5(4.6)
4.4(4.5)
4.2(4.15)
5.0(4.9)
3.7(3.7)
4.4(4.4)
3.9(3.9)
4.2(4.3)
5.6(5.6)
12.5(12.5)
7.4(7.5)
11.1(11.2)
11.3(11.4)
6.9(6.8)
82
47
78
54
38
48
51
37
43
38
25
C30H24Cl2CuN4O11
C34 34
C34 33
C34 34
C36 38
C65 45
C33 26
C32 22
C37 31
C38 38
H
N6O10Zn
CoN6O9.5
Cl2CuN4O12
N6O10Zn
N4Cl3O8Co2
N2O5Cu
H
H
H
10.7(10.8)
4.6(4.5)
H
[CuL3].CH3OH
H
4.8(4.7)
[ZnL3]
H
N2O4Zn
5.0(5.0)
[CoL4].CHCl3
H
N2Cl3O4Co
N2O6Cu
3.8(3.8)
[CuL4].2CH3OH
H
4.1(4.1)
perchlorate complexes, absorptions attributable to ionic
perchlorate were found at approximately 1100 and 624 cm-1.
The lack of splitting of these bands suggests that the
perchlorate anions are not coordinated.21 The band at ~1384
[Cu(L2)](ClO4)2.2H2O
and
[Zn(L2)](NO3)2.2CH3OH
complexes indicate the presence of the macroacyclic ligand
and metal ion and, as is common with complexes of this type,
a characteristic fragmentation pattern resulting from stepwise
loss of counterions from the neutral parent ion is observed.26-32
For these complexes, the highest-mass and more intense peak
in each case corresponds to the general formulation [MLX]+
and the loss of a second counterion occurs to generate [ML]+.
In the [Zn(L1)](NO3)2.2CH3CH2OH complex, the FAB mass
spectra gave a highest-mass and more intense peak at m/z 598
assignable to [Zn(L1)NO3]+. The spectrum also shows a peak
due to [ZnL1]+ and [L1 + H]+ at 536 and 471, respectively.
For [CoL3].0.5CHCl3, [CuL3].CH3OH, [ZnL3], [CoL4].
CHCl3 and [CuL4].2CH3OH complexes the highest-mass and
more intense peak in each case corresponds to the general
formulation [ML + H]+. Unfortunately, we could not prepare
zinc complexes with H2L4.
‾ 22,23
cm-1 for the nitrate complexes is due to ionic NO3 .
The shift of the imine band to lower and higher
wavenumbers by complexation suggests coordination
via the nitrogen atoms for complexes containing
salicylaldehyde.24 The diamagnetic zinc complexes were
studied by 1H, 13C, COSY, HMQC and DEPT NMR
1
experiments. The H and 13C NMR were run immediately
after solution in DMSO-d6 and gave the expected simple
spectrum, indicating the integrity of the complexes.
The spectra obtained after 12, 24 and 120 h were similar to
the initial spectra indicating that the complexes are stable
1
in solution. The H NMR spectra of complexes, containing
2-pyridinecarboxaldehyde, show a peak at ~ 9.20 ppm due
to the formation of the iminic bond. The 13C NMR spectra
show 14 and 19 signals for [Zn(L1)](NO3)2.2CH3CH2OH
and [Zn(L2)](NO3)2.2CH3OH complexes respectively.
The peak at ~163.3 ppm, assignable to the imine carbon atoms,
confirms the presence of the Schiff base in the complexes.
1H NMR spectrum of [ZnL3] shows a peak at 8.47 ppm
corresponding to the imine protons. No signal corresponded
to hydroxyl protons at ~13.1 ppm, suggested that the hydroxyl
groups are fully deprotonated and the oxygen is most likely
coordinated to the metal ions. The 13C NMR spectrum of
the Zn2+ complex with H2L3 is very simple and exhibited 16
signals, as expected; the peak at 172.8 ppm corresponds to
the imine carbon for such a zinc complex.25 The FAB mass
spectral results serve an important role in confirming the
[1 + 1] nature of the complexes (Tables 2 and 3). The FAB
mass spectra for [Co(L1)](NO3)2.H2O, [Cu(L1)](ClO4)2.
H2O, [Zn(L1)](NO3)2.2CH3CH2OH, [Co(L2)](NO3)2.1.5H2O,
Experimental
Materials and physical measurements
NMR spectra were recorded using Jeol FX-Q 90 MHZ, Bruker FT
NMR 350 and 500 MHZ spectrometers. The IR spectra were recorded
as KBr discs, using a Perkin Elmer FT-IR GX spectrophotometer
(4000–4600 cm-1). Positive ion FAB mass spectra were recorded
on a Kratos-MS-50 spectrometer with 3-nitrobenzyl alcohol as the
matrix solvent. Solvents were of reagent grade and were purified
by the usual methods. Catechol, 4-tert-butylcatechol, 1-fluoro-2-
nitrobenzene, 2-pyridinecarboxaldehyde, salicylaldehyde and metal
salts were obtained from Merck Chem.Co. and used without further
purification.
Ligand synthesis
Synthesis of 1,2-bis(2'-nitrophenoxy)benzene (1): Catechol (11 g,
0.1 mol) was dissolved in DMF (100 cm3)/xylene (10 cm3) before
K2CO3 (42 g, 0.3 mol) and 1-fluoro-2-nitrobenzene (28.2 g, 0.2 mol)
were added. The mixture, refluxed at 130–135°C under a dinitrogen
atmosphere for 24 h with stirring, was then allowed to cool and poured
Table 2 IR data (cm-1) and FAB mass spectral of the complexes
–
–
Compound
n(C=N)a
n(C=N)b
n(C=C)c
NO3
ClO4
Peak
Assignment
[Co(L1)](NO3)2.H2O
1628
1631
1634
1635
1635
1637
1596
1599
1597
1597
1597
1597
1486
1487
1485
1485
1487
1491
1384
592
634
598
648
690
654
[Co(L1)(NO3)]+
[Cu(L1)(ClO4)]+
[Zn(L1)(NO3)]+
[Co(L2)(NO3)]+
[Cu(L2)(ClO4)]+
[Zn(L2)(NO3)]+
[Cu(L1)](ClO4)2.H2O
1100, 623
1100, 624
[Zn(L1)](NO3)2.2CH3CH2OH
[Co(L2)](NO3)2.1.5H2O
[Cu(L2)](ClO4)2.2H2O
[Zn(L2)](NO3)2.2CH3OH
1384
1384
1384
aSchiff base. b,cPyridine ring.
Table 3 IR data (cm-1) and FAB mass spectral of the complexes
Compound
Sol. for crystallisation
n(C=N)
n(C=C)
n(C-H)
Peak
Assignment
[CoL3].0.5CHCl3
[CuL3].CH3OH
[ZnL3]
[CoL4].CHCl3
[CuL4].2CH3OH
CHCl3/CH3OH
CH3OH
1607
1609
1612
1611
1609
1581
1581
1584
1590
1588
-
-
559
563
565
615
619
[CoL3 + H]+
[CuL3 + H]+
[ZnL3 + H]+
[CoL4 + H]+
[CuL4 + H]+
CH3CN
-
CHCl3/CH3OH
CH3OH
2963
2965

364 JOURNAL OF CHEMICAL RESEARCH 2009
into H2O (500 cm3). The precipitate was isolated by filtration. After
drying, the crude product was recrystallised from EtOH to give pure
1,2-bis(2'-nitrophenoxy)benzene. Yield: 31.3 g (89%). Anal. Calcd
for C18H12N2O6: C, 61.4; H, 3.4; N, 7.95. Found: C, 61.3; H, 3.5; N,
7.8%. M.p. 110°C. 1H NMR dH (90 MHz, CDCl3): 6.9–8 (m, Ar,
12H). 13C NMR dC (90 MHz, CDCl3): 150.1, 145.8, 140.0, 134.2,
126.3, 125.5, 123.1, 121.9, 118.9. IR: 1524, 1348 (–NO2), 1179
(C–O–C str).
H2L3:Yield: 0.39 g (73%).Anal. Calcd for C32H24N2O4.CH3CH2OH
C, 74.7; H, 5.5; N, 5.1. Found: C, 74.8; H, 5.5; N, 5.1%. 1H NMR dH
(500 MHz, CDCl3): 6.8–7.4 (m, Ar, 20 H), 8.5 (s, CH=N, 2H), 13.1 (s,
OH, 2H). 13C NMR dC (90 MHz, CDCl3): 163.4, 161.2, 149.8, 146.9,
138.6, 132.9, 132.2, 127.5, 124.9, 123.6, 121.1, 120.7, 119.3, 118.7,
118.1, 117.1. IR: 3408 (OH), 1618 (CH=N), 1592 (C=C)ar.
H2L4:Yield:0.36g(64%).Anal.CalcdforC36H32N2O4.2CH3CH2OH
1
C, 74.05; H, 6.8; N, 4.3. Found: C, 74.1; H, 6.8; N, 4.4%. H NMR
Synthesis of 1,2-bis(2'-nitrophenoxy)-4-t-butylbenzene (2):
4-tert-Butylcatechol (16.6 g, 0.1 mol) was dissolved in DMF
(100 cm3)/xylene (10 cm3) before K2CO3 (42 g, 0.3 mol) and 1-
fluoro-2-nitrobenzene (28.2 g, 0.2 mol) were added. The mixture
was refluxed at 130–135°C under a dinitrogen atmosphere for 24 h
with stirring, then the obtained mixture was poured into MeOH/H2O
(440 cm3, vol. ratio 10:1) and left overnight at 0°C to give a solid,
which was collected, washed thoroughly with MeOH and H2O, and
dried under vacuum.After drying, the crude product was recrystallised
from EtOH to give pure 1,2-bis(2'-nitrophenoxy)-4-t-butylbenzene.
Yield: 37.21 g (91%). Anal. Calcd for C22H20N2O6: C, 64.7; H, 4.9;
dH (500 MHz, CDCl3): 13.2 (s, OH, 2H), 8.4 (s, CH=N, 2H), 7.4–6.4
(m, Ar, 19 H), 1.3 (s, C(CH3)3, 9H). 13C NMR dC (90 MHz, CDCl3):
163.2, 161.2, 160.2, 148.9, 145.8, 144.3, 138.0, 132.8, 132.1, 127.4,
123.0, 122.1, 121.4, 121.0, 120.6, 119.4, 118.6, 117.1, 34.4, 31.3.
IR: 3410 (OH), 2959, 2864 (C–H)aliph, 1619 (CH=N), 1590 (C=C)ar.
Synthesis of L5 and L6
2-Pyridinecarboxaldehyde (2 mmol) in dry MeOH (25 cm3) was
slowly added to a stirred solution of the appropriate diamine [1,2-bis
(2'-aminophenoxy)benzene or 1,2-bis(2'-aminophenoxy)-4-t-butyl-
benzene; 1 mmol] in dry MeOH (25 cm3). The yellow solution was
stirred for 5 h and then NaBH4 (6 mmol) was added in small portions
to the solution. The resulting mixture was stirred at room temperature
for 35 h. The solvent was reduced to dryness by rotary evaporation,
extracted by CHCl3 (3 ¥ 50 cm3) and dried in vacuo.
1
N, 6.9. Found: C, 64.7; H, 4.9; N, 6.9%. M.p. 52°C. H NMR dH
(90 MHz, CDCl3): 7.8–6.8 (m, Ar, 11H), 1.3 (s, C(CH3)3, 9H). 13C
NMR dC (90 MHz, CDCl3):150.3, 144.7, 143.2, 139.8, 139.5, 134.1,
125.4, 123.4, 122.8, 122.6, 121.7, 119.8, 118.5, 118.0, 34.5, 31.1. IR:
2964, 2868 (C–H)aliph, 1524, 1348 (–NO2), 1186 (C–O–C str).
L5: Yield: 0.35 g (73%). Anal. Calcd for C30H26N4O2.2H2O C,
70.6; H, 5.9; N, 11.0. Found: C, 70.5; H, 6.0; N, 11.1%. 1H NMR dH
(90 MHz, CDCl3): 8.53 (2H, py), 8.00 (2H, py), 7.79–6.37 (ar (12H)
and py (4H)), 4.67 (4H, CH2NH). 13C NMR dC (90 MHz, CDCl3):
148.76–113.18 (ar and py rings), 45.81 (H2C–NH). IR: 3359 (NH),
1600 (CH=N)py, 1488 (C=C)py.
L6: Yield: 0.36 g (67%). Anal. Calcd for C34H34N41O2.2H2O C,
72.1; H, 6.8; N, 9.9. Found: C, 72.0; H, 6.7; N, 10.0%. H NMR dH
(90 MHz, CDCl3): 8.50 (2H, py), 8.06 (2H, py), 7.66–6.48 (ar (11H) and
py (4H)), 4.64 (4H, CH2NH), 1.36 (9H, CCH3). 13C NMR dC (90 MHz,
CDCl3): 149.01–112.89 (ar and py rings), 45.93 (H2C–NH), 34.51
(CCH3), 31.10 (CCH3). IR: 3363 (NH), 1598(CH=N)py, 1493 (C=C)py.
Synthesis of 1,2-bis (2'-aminophenoxy)benzene (3): A mixture of
1,2-bis(2'-nitrophenoxy) benzene (3.52 g, 10 mmol), NH4Cl (1.07 g,
20 mmol) and H2O (10 cm3) in MeOH (100 cm3) was heated to
boiling and zinc dust (2 g, 30 mmol) in 0.1 g portions at intervals
of several minutes was added. The mixture was then refluxed for
5 h. The resulting solution was filtered, extracted with H2O (300 cm3)
and dried. The precipitate was dissolved in CH3CN, the solution was
filtered and the solvent was the removed. Yield: 2.1 g (73%). Anal.
Calcd for C18H16N2O2.0.25H2O: C, 72.8; H, 5.6; N, 9.4 Found: C,
1
72.7; H, 5.5; N, 9.5%. M.p. 110°C. H NMR dH (90 MHz, CDCl3):
7–6.6 (m, Ar, 12H), 3.7 (s, NH2, 4H). 13C NMR dC (90 MHz, CDCl3):
147.2, 144.3, 137.5, 124.2, 120.1, 118.8, 117.8, 116.8. IR: 3426,
3408, 3313 (NH str), 1199 (C–O–C str).
Synthesis of H2L7 and H2L8
Synthesis of 1,2-bis(2'-aminophenoxy)-4-t-butylbenzene (4):
A mixture of 1,2-bis(2'-nitrophenoxy)-4-t-butylbenzene (4.09 g,
10 mmol), NH4Cl (1.07 g, 20 mmol) and H2O (10 cm3) in MeOH
(100 cm3) was heated to boiling and zinc dust (2 g, 30 mmol) was
added in 0.1 g portions at intervals of several minutes. The mixture was
reflux for 5 h. The solution was evaporated to dryness and the residue
extracted with H2O/CHCl3. The organic layer was evaporated to yield
an organic solid. Yield: 2.71 g (77%). Anal. Calcd for C22H24N2O2.
H2O: C, 72.1; H, 7.15; N, 7.6. Found: C, 72.2; H, 7.1; N, 7.7%. M.p.
89–91°C. 1H NMR dH (90 MHz, CDCl3): 7.2–6.6(m, Ar, 11H), 3.7(br,
NH2, 4H), 1.3(s, C(CH3)3, 9H). 13C NMR dC (90 MHz, CD3CN):
148.5, 147.3, 146.4, 145.2, 144.6, 140.1, 139.7, 125.4, 124.9, 122.1,
119.7, 119.2, 118.5, 118.1, 116.9, 35.1, 31.7. IR: 3461, 3405, 3376,
NaBH4 (0.15 g, 4 mmol) was added in small portions to a solution
of Schiff base ligand (H2L1 or H2L2, 1 mmol) in absolute EtOH
(50 cm3). The resulting mixture was stirred at room temperature
for 30 h. The solvent was then removed and extracted by CHCl3
(3 ¥ 50 cm3) and dried.
H2L7: Yield: 0.26 g (51%). Anal. Calcd for C32H28N2O4.CHCl3 C,
1
63.5; H, 4.7; N, 4.5. Found: C, 63.5; H, 4.7; N, 4.55%. H NMR dH
(500 MHz, CDCl3): 7.4–6.5(m, Ar, 20 H), 4.2 (s, CH2, 4H). 13C NMR
dC (90 MHz, CDCl3): 156.2, 146.6, 145.4, 138.3, 128.8, 128.6, 124.8,
124.1, 123.2, 120.7, 119.9, 119.5, 116.3, 114.4, 47.4. IR: 3331 (NH),
1585 (C=C)ar.
H2L8: Yield: 0.35 g (63%). Anal. Calcd for C36H36N2O4 C, 77.1; H,
6.5; N, 5.0. Found: C, 77.0; H, 6.4; N, 5.05%. 1H NMR dH (90 MHz,
CDCl3): 7.4–6.6 (m, Ar, 19 H), 4.2 (s, CH2, 4H), 1.3 (s, C(CH3)3,
9H). 13C NMR dC (500 MHz, CDCl3): 156.4, 148.6, 146.0, 145.6,
144.2, 138.3, 128.7, 128.6, 123.8, 123.3, 120.6, 119.8, 118.9, 115.9,
115.7, 115.1, 114.3, 47.5, 34.4, 31.3. IR: 3340 (NH), 1587 (C=C)ar.
3304 (–NH2), 3041 (C–H)ar, 2962, 2867 (C–H)aliph
.
Synthesis of L1 and L2: 2-Pyridinecarboxaldehyde (2 mmol) in
dry MeOH (25 cm3) was slowly added to a stirred solution of the
appropriate diamine [1,2-bis(2'-aminophenoxy)benzene or 1,2-bis
(2'-aminophenoxy)-4-t-butylbenzene;
1 mmol] in dry MeOH
(25 cm3). The yellow solution was stirred for 5 h. The solvent
volume was reduced, cooled in an ice bath for 3 h and the yellow
precipitate formed was filtered off and dried in vacuo.
Preparation of complexes
Metal complexes of L1 and L2 ligands
General synthesis
L1: Yield: 0.27 g (57%). Anal. Calcd for C30H22N4O2 C, 76.6; H,
4.7; N, 11.9. Found: C, 76.5; H, 4.8; N, 11.8%.1H NMR dH (90 MHz,
CDCl3): 9.29 (2H, HC=N), 8.87 (2H, py), 8.16 (2H, py), 8.01–6.63
(ar (12H) and py (4H)). 13C NMR dC (90 MHz, CDCl3): 163.51
A MeOH solution (25 cm3) of 2-pyridinecarboxaldehyde (2 mmol)
was added dropwise to a MeOH solution (25 cm3) of the appropriate
diamine (1 mmol). The yellow solution was stirred for 5 h; then the
appropriate salt (1 mmol) in MeOH (15 cm3) was added dropwise.
The resulting solution was stirred for 4 h at 40–45°C and allowed to
stand overnight. The precipitate was filtered, washed with EtOH and
Et2O and dried in vacuo.
(C=N)imi, 150.34–115.34 (ar and py rings). IR: 1637 (CH=N)imi
,
1601 (CH=N)py, 1488 (C=C)py.
L2: Yield: 0.32 g (61%).Anal. Calcd for C34H30N4O2.2CH3OH C, 73.2;
H, 6.5; N, 9.5. Found: C, 73.3; H, 6.4; N, 9.6%. 1H NMR dH (90 MHz,
CDCl3): 9.31 (2H, HC=N), 8.87 (2H, py), 8.26 (2H, py), 8.20–6.51
(ar(11H) and py(4H)), 1.33 (9H, CCH3). 13C NMR dC (90 MHz, CDCl3):
163.49 (C=N)imi, 150.21–115.31 (ar and py rings), 34.56 (CCH3), 31.08
(CCH3). IR: 1639 (CH=N)imi, 1600 (CH=N)py, 1488 (C=C)py.32
[Zn(L1)](NO3)2.2CH3CH2OH: 1H NMR dH (350 MHz, DMSO-d6):
6.65, 6.78, 6.89, 6.97, 7.46, 7.70, 7.97, 8.04, 8.30, 8.84, 9.20. 13C NMR dC
(350 MHz, DMSO-d6): 115.41, 122.14, 125.77, 126.47, 127.23, 128.28,
129. 68, 129.86, 133.34, 142.05, 146.26, 148.83, 150.50, 163.37.
1
[Zn(L2)](NO3)2. 2CH3OH: H NMR dH (350 MHz, DMSO-d6):
1.33, 6.56, 6.61, 6.67, 6.84, 6.95, 7.46, 7.52, 7.90, 8.02, 8.25, 8.76,
9.26. 13C NMR dC (350 MHz, DMSO-d6): 31.01, 34.56, 115.18, 121.
48, 121.84, 123.62, 125.65, 127.20, 128.06, 129.20, 129.30, 133.10,
141.76, 143.76, 145.85, 146.17, 148.79, 150.19, 163.20.
Synthesis of H2L3 and H2L4
The salicylaldehyde (0.244 g, 2 mmol) in absolute EtOH (25 cm3)
was added dropwis to hot solution in absolute EtOH (50 cm3) of the
appropriate diamine [1,2-bis (2'-aminophenoxy)benzene or 1,2-bis(2'-
aminophenoxy)-4-t-butylbenzene; 1 mmol]. The solution was gently
refluxed for 6 h. The colour of the solution changed to yellow. The
solution was then concentrated in a rotary evaporator to a volume of ca
15 cm3. The precipitate was obtained by standing overnight at 0°C.
Metal complexes of H2L3 and H2L4 ligands
General synthesis
The salicylaldehyde (0.244 g,
2 mmol) in absolute EtOH
(25 cm3) was added dropwise to a hot solution in absolute EtOH

JOURNAL OF CHEMICAL RESEARCH 2009 365
(50 cm3) of diamine [1,2-bis (2'-aminophenoxy)benzene or 1,2-bis
(2'-aminophenoxy)-4-t-butylbenzene; 1 mmol]. The solution was
gentlly refluxed for 6 h. After cooling to 55–60°C temperature
a solution of triethylamine (0.2 g, 2 mmol) in absolute EtOH
(5 cm3) was added to the solution. The solution was essentially red
at this time. The mixture stirred for 10 min, and then a solution of
appropriate metal salt (1 mmol) in absolute EtOH (20 cm3) was
added dropwise. The solution was refluxed for 6 h, concentrated in
a rotary evaporator until approximately 10–15 cm3. The precipitation
obtained was filtered off.
10 D.W. Christianson, Adv. Protein Chem., 1991, 42, 281.
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Inorg. Chim. Acta, 2005, 207, 39.
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H. Khavasi and H. Adams, Polyhedron., 2008, 27, 1631.
20 S. Salehzadeh, S.A. Javarsineh and H. Keypour, J. Molec. Struct., 2005,
739, 57.
[ZnL3]: 1H NMR dH (500 MHz, DMSO-d6): 6.46, 6.53, 7.06, 7.15,
7.21, 7.28, 7.56, 8.47. 13C NMR dC (500 MHz, DMSO-d6): 114.4,
119.3, 120.6, 123.0, 123.1, 123.4, 126.3, 126.7, 128.5, 136.7, 138.2,
140.7, 148.9, 151.1, 170.9, 172.8.
IR and NMR spectra of dinitro and diamine compounds, ligands
and zinc complexes of L1, L2 and H2L3 and FAB-Mass spectra of
complexes are available upon request from the authors.
21 H. Keypour, R. Azadbakht, H.A. Rudbari, H. Khavasi, Polyhedron
(submitted).
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25 L. Valencia, H. Adams, R. Bastida, D.E. Fenton and A. Macias, Inorg.
Chim. Acta, 2001, 317, 45.
We are grateful to the Department of Chemistry of Bu–Ali
Sina, Tarbiat Moalem Universities and Sharif University of
Technology for support of this work.
Received 18 December 2008; accepted 1 April 2009
Paper 09/0369 doi: 10.3184/030823409X457528
Published online: 22 June 2009
26 H. Adams, R. Bastida, D.E. Fenton, A. Macias, S.E. Spey and L. Valencia.
J. Chem. Soc., Dalton Trans., 1999, 4131.
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