Synthesis and spectral studies of macrocyclic Pb(II), Zn(II) and La(III) complexes by template reaction of 1,4-bis(3-aminopropoxy)butane with metal nitrate and salicylaldehyde derivatives

Article abstract of DOI:10.3184/030823409X12609007112282

Six new macrocyclic complexes are synthesised by template reaction of 1,4-bis(3-aminopropoxy)butane with metal nitrate and 1,7-bis(2-formylphenyl)-1, 4,7-trioxaheptane or 1,10-bis(2-formylphenyl)-1,4,7,10-tetraoxadecane and their structures are proposed on the basis of elemental analysis, FT-IR, UV-Vis, molar conductivity measurements, ₁H NMR and mass spectra. The complexes are 1:2 electrolytes for Pb(II),Zn(II) complexes and 1:3 electrolytes for La(III) as shown by their molar conductivities (A_m) in DMSO at 10⁰³ mol L^-1. The confi gurations of La(III) and Zn(II) complexes are proposed to probably octahedral.

Full text of DOI:10.3184/030823409X12609007112282

JOURNAL OF CHEMICAL RESEARCH 2010
RESEARCH PAPER 1
JANUARY, 1–4
Synthesis and spectral studies of macrocyclic Pb(II), Zn(II) and La(III)
complexes by template reaction of 1,4-bis(3-aminopropoxy)butane with
metal nitrate and salicylaldehyde derivatives
Salih Ilhan*
Department of Chemistry, Faculty of Art and Sciences, Siirt University, Siirt, Turkey
Six new macrocyclic complexes are synthesised by template reaction of 1,4-bis(3-aminopropoxy)butane with metal
nitrate and 1,7-bis(2-formylphenyl)-1,4,7-trioxaheptane or 1,10-bis(2-formylphenyl)-1,4,7,10-tetraoxadecane and their
structures are proposed on the basis of elemental analysis, FT-IR, UV-Vis, molar conductivity measurements, 1H NMR
and mass spectra. The complexes are 1:2 electrolytes for Pb(II),Zn(II) complexes and 1:3 electrolytes for La(III) as
shown by their molar conductivities (Λm) in DMSO at 10−3 mol L−1. The configurations of La(III) and Zn(II) complexes
are proposed to probably octahedral.
Keywords: macrocyclic Schiff base, macrocyclic complexes, 1,7-bis(2-formylphenyl)-1,4,7-trioxaheptane, 1,10-bis(2-
formylphenyl)-1,4,7,10-tetraoxadecane and 1,4-bis(3-aminopropoxy)butane
t, 4H, J = 7.1), δ = 1.38 (H7, t, 4H, J = 6.4) , δ = 3.42 (H O), δ = 7.03–
8.11 (m, 8H, ArH), δ = 10.36 (s, 2H, HC=N). Selected 2IR data (KBr,
ν cm−1): 3368 ν(H2O), 1642 ν(C=N), 1384 ν(ionic NO3−), 487 ν(Pb-O),
439 ν(Pb-N). ΛM = 183 Ω−1 mol−1 cm2. UV-vis (λmax, nm) (DMSO):
278, 326, 382. Mass spectrum (m/z): [630, 2.6%, [PbL1-(OCH2
CH2O)]+].
Schiff-base condensations are used to form macrocyclic
ligands from diamines and dicarbonyl compounds. It is nor-
mally necessary to use a metal ion to act as a template in
bringing the amine and carbonyl compound together.1–3 Schiff
base macrocycles play a large role in macrocyclic chemistry.4
The coordination chemistry of macrocyclic ligands is a
fascinating area of intense study for inorganic chemists.5,6 Syn-
thesis of these Schiff-base complexes are achieved through
the template reaction or transmetallation reactions.7–9 There is
continuing interest in synthesising macrocyclic complexes10–12
because of their potential applications in fundamental and
applied sciences and importance in the area of coordination
chemistry.13–15
[Zn(H2O)L1][NO3]2.3H2O: Yield: 0.34 g (22.8%). Anal. Calcd for
.
ZnC28H40N4O12 3H2O: C, 45.22; H, 6.19; N, 7.54. Found: C, 45.37; H,
6.15; N, 7.58%. 1H NMR (DMSO-d6, δ ppm): δ = 3.87 (H1, t, 4H, J =
6.1), δ = 4.26 (H2, t, 4H, J = 6.7), δ = 3.63 (H3, t, 4H, J = 5.6), δ =
1.94 (H4, p, 4H, J = 7.2), δ = 3.58 (H5, t, 4H, J = 5.4), δ = 3.50 (H6,
t, 4H, J = 4.8), δ = 1.34 (H7, t, 4H, J = 6.4) , δ = 3.42 (H O), δ =
7.02–8.07 (m, 8H, ArH), δ = 10.36 (s, 2H, HC=N). Selected2IR data
(KBr, ν cm−1): 3376 ν(H O), 1646 ν(C=N), 1384 ν(ionic NO3−), 515
ν(Zn-O), 476 ν(Zn-N). 2ΛM = 195 Ω−1mol−1cm2. UV-vis (λ , nm)
(DMSO): 277, 325, 381. Mass spectrum (m/z): [691m, ax0.9%,
[Zn(H2O)L1][NO3]2]+].
In this study, I have synthesised Pb(II), Zn(II) and La(III)
complexes by template reaction of 1,4-bis(3-aminopropoxy)
.
butane with salicylaldehyde derivatives and M(NO3) 6H2O in
[La(H2O)L1][NO3]3.H2O: Yield: 0.25 g (14.8%). Anal. Calcd for
methanol Then, spectral properties of the new compnounds are
studied in detail.
.
LaC28H40N5O15 H2O: C, 39.86; H, 4.98; N, 8.30. Found: C, 40.07; H,
5.15; N, 8.51%. 1H NMR (DMSO-d6, δ ppm): δ = 3.86 (H1, t, 4H, J =
6.4), δ = 4.27 (H2, t, 4H, J = 6.2), δ = 3.61 (H3, t, 4H, J = 5.2), δ =
1.95 (H4, p, 4H, J = 7.4), δ = 3.58 (H5, t, 4H, J = 6.2), δ = 3.52 (H6,
t, 4H, J = 4.8), δ = 1.36 (H7, t, 4H, J = 6.3) , δ = 3.41 (H O), δ =
7.01–8.09 (m, 8H, ArH), δ = 10.39 (s, 2H, HC=N). Selected2IR data
(KBr, ν cm−1): 3374 ν(H2O), 1641 ν(C=N), 1384 ν(ionic NO3−), 493
ν(La-O), 456 ν(La-N). ΛM = 246 Ω−1 mol−1 cm2. UV-vis (λ , nm)
(DMSO): 279, 327, 379. Mass spectrum (m/z): [827,max0.8%,
[La(H2O)L1][NO3]3+H]+].
Experimental
Methods
Elemental analysis is carried out on a LECO CHNS model 932 ele-
mental analyzer. 1H NMR spectra are recorded using a model Bruker
Avance DPX-400 NMR spectrometer. IR spectra are recorded on a
Perkin Elmer Spectrum RX1 FTIR spectrometer on KBr discs in the
wave number range of 4000–400 cm−1. Electronic spectral studies are
conducted on a Shimadzu model 160 UV Visible spectrophotometer
in the wavelength 200–800 nm. Molar conductivity is measured with
a WTW LF model 330 conductivity meters, using prepared solution
of the complex in DMSO. LC/MS-API-ES mass spectra are recorded
using an AGILENT model 1100 MSD mass spectrophotometer.
[PbL2][NO3]2.H2O: Yield: 0.27 g (15.4%). Anal. Calcd for
.
PbC30H42N4O12 H2O: C, 41.10; H, 5.02; N, 6.39. Found: C, 41.46; H,
1
5.19; N, 6.33%. H NMR (DMSO-d6, δ ppm): δ = 3.59 (H1, s, 4H),
δ = 3.85 (H2, t, 4H, J = 8.1), δ = 4.21 (H3, t, 4H, J = 7.6), δ = 3.56
(H4, t, 4H, J = 6.4), δ = 1.87 (H5, p, 4H, J = 4.3), δ = 3.23 (H6, t, 4H,
J = 6.8), δ = 3.35 (H7, t, 4H, J = 7.3), δ = 1.42 (H7, t, 4H, J = 5.3),
δ = 3.43 (H2O), δ = 7.01–8.10 (m, 8H,ArH), δ = 10.38 (s, 2H, HC=N).
Selected IR data (KBr, ν cm−1): 3376 ν(H2O), 1647 ν(C=N), 1384
ν(ionic NO −), 482 ν(Pb-O), 436 ν(Pb-N). ΛM = 207 Ω−1mol−1cm2.
UV-vis (λma3x, nm) (DMSO): 277, 324, 378. Mass spectrum (m/z):
[628, 1.3%, [PbL2-(OCH2CH2OCH2CH O)]+].
Chemical and starting materials
The salicylaldehyde derivatives which are used in the synthesis are
prepared as shown in Fig. 1.16,18 All the other chemicals and solvents
are of analytical grade and used as received.
[ZnL2][NO3]2.H2O: Yield: 0.24 g2 (16.3%). Anal Calcd for
General synthesis of complexes
.
ZnC30H42N4O12 H2O: C, 48.98; H, 5.99; N, 7.62. Found: C, 49.19; H,
To a stirred solution of salicylaldehyde derivatives (2 mmol) and
metal nitrate in methanol (50 mL) is added dropwise 1,4-bis(3-
aminopropoxy)butane (2 mmol) in methanol (30 mL). The reaction is
continued for 2h at 80 °C and 1 h at room temperature. After the reac-
tion is completed, the coloured precipitate is filtered and washed with
methanol and, dried in air. Yield: 33–14%.
6.11; N, 7.50%. 1H NMR (DMSO-d6, δ ppm): δ = 3.88 (H1, t, 4H, J =
6.1), δ = 4.26 (H2, t, 4H, J = 6.7), δ = 3.61 (H3, t, 4H, J = 5.6), δ =
1.96 (H4, p, 4H, J = 7.2), δ = 3.56 (H5, t, 4H, J = 5.4), δ = 3.51 (H6,
t, 4H, J = 4.8), δ = 1.33 (H7, t, 4H, J = 6.4) , δ = 3.41 (H O), δ =
6.93–8.08 (m, 8H, ArH), δ = 10.38 (s, 2H, HC=N). Selected2IR data
(KBr, ν cm−1): 3373 ν(H O), 1649 ν(C=N), 1384 ν(ionic NO3−), 523
ν(Zn-O), 481 ν(Zn-N). 2ΛM = 177 Ω−1mol−1cm2. UV-vis (λ , nm)
(DMSO): 279, 327, 382. Mass spectrum (m/z): [735m, ax1.0%,
[ZnL2][NO3]2.H2O+H]+].
[PbL1][NO3]2.2H2O: Yield: 0.55 g (32.5%). Anal. Calcd for
.
PbC28H38N4O11 2H2O: C, 39.58; H, 4.95; N, 6.60. Found: C, 40.61; H,
5.09;N, 6.53%. 1H NMR (DMSO-d , δ ppm): δ = 3.85 (H1, t, 4H, J =
7.2), δ = 4.22 (H2, t, 4H, JV= 6.9),6δ = 3.64 (H3, t, 4H, J = 4.6), δ =
1.92 (H4, p, 4H, J = 7.4), δ = 3.62 (H5, t, 4H, J = 5.6), δ = 3.51 (H6,
[LaL2][NO3]3.2H2O: Yield: 0.32 g (18.0%). Anal. Calcd for
.
LaC30H42N5O16 2H2O: C, 40.54; H, 5.18; N, 7.88. Found: C, 41.12; H,
1
5.31; N, 7.73%. H NMR (DMSO-d6, δ ppm): δ = 3.81 (H1, t, 4H,
* Correspondent. E-mail: salihilhan@dicle.edu.tr
J = 6.7), δ = 4.28 (H2, t, 4H, J = 7.3), δ = 3.62 (H3, t, 4H, J = 6.2),

2
JOURNAL OF CHEMICAL RESEARCH 2010
Fig. 1 Synthesis of 1,7-bis(2-formylphenyl)-1,4,7-trioxaheptane and 1,10-bis(2-formylphenyl)-1,4,7,10-tetraoxadecane.
δ = 1.96 (H4, p, 4H, J = 7.4), δ = 3.57 (H5, t, 4H, J = 6.6), δ = 3.54
(H6, t, 4H, J = 8.1), δ = 1.35 (H7, t, 4H, J = 5.8) , δ = 3.41 (H2O),
δ = 7.00–8.04 (m, 8H, ArH), δ = 10.40 (s, 2H, HC=N). Selected IR
data (KBr, ν cm−1): 3369 ν(H O), 1644 ν(C=N), 1384 ν(ionic NO −),
495 ν(La-O), 462 ν(La-N). Λ2 = 262 Ω−1mol−1cm2. UV-vis (λ , n3m)
(DMSO): 277, 326, 376. MMass spectrum (m/z): [852,max1.1%,
[LaL2][NO3]3]+].
and ν (NH2) peak at around 3300 cm−1 are indicative of Schiff’s base
condensation. A strong band observed in the IR spectra of the com-
plexes at ca 1645 cm−1 region which is attributed to the υ(C=N) stretch,
indicating coordination of the azomethine nitrogen to metal.20 The
presence of several bands in the region associated with nitrate vibra-
tions clearly identifies these species as containing nitrate groups. The
absorptions of the nitrate counterions, at ca 1460–1452 (ν3), 1300 (ν1)
and 1040 (ν2) cm−1, suggest the presence of nitrate groups: a intense
band at ca 1384 cm−1 attributable to ionic nitrate, is also present.21 In
the spectra of all the complexes are dominated by bands between 2965
and 2855 cm−1 due to ν(Alph.-CH) groups.22 Conclusive evidence of
the bonding is also shown by the observation that new bands in the IR
spectra of the complexes appear at 525–485 cm−1 and 481–435 cm−1
assigned to ν(M–O) and ν(M–N) stretching vibrations23 (Table 2).
Result and discussion
Macrocyclic Schiff base complexes
In the reaction between synthesis of 1,7-bis(2-formylphenyl)-1,4,7-
trioxaheptane or 1,10-bis(2-formylphenyl)-1,4,7,10-tetraoxadecane,
metal nitrate and 1,4-bis(3-aminopropoxy)butane in methanol, the
[1+1] macrocyclic Schiff-base complexes are formed as the product.
The macrocyclic complexes are characterised by elemental analysis,
Electronic spectra
1
UV-vis spectra, conductivity measurements, mass, H NMR and IR
Electronic absorption spectral data of complexes in DMSO at room
temperature are presented in the experimental section. The absorption
bands below ca 300 nm are practically identical and can be attributed
to π→π* transitions in the benzene ring and azomethine (–C=N)
groups. The absorption bands observed ca the 300–330 nm range are
most probably due to the transitions of n→π* of imine groups.22–24
spectra. The mass spectrum of complexes plays an important role in
confirming the monomeric [1+1] (dicarbonyl and diamine) nature of
complexes. As the crystals are unsuitable for single-crystal, X-ray
analyses of the complexes cannot be done. The complexes are insolu-
ble in most common solvents, including water, ethanol, ethyl acetate,
and acetonitrile (Table 1).
Molar conductivity and mass spectra
FT-IR spectra
The complexes are 1:2 electrolytes for Pb(II) and Zn(II) complexes as
shown by their molar conductivities (ΛM) in DMSO at 10−3 M, which
are in the range 140–200 Ω−1cm2mol−1 and 1:3 electrolytes for La(III)
complexes as shown by their molar conductivities (ΛM) in DMSO at
The characteristic IR spectrum data are given in the experimental sec-
tion. IR spectra of the complexes are recorded in the KBr pellet from
4000 to 400 cm−1. The broad bands within the range ca 3370 cm−1 for
all complexes can be attributed to stretching vibrations of water mol-
ecule υ(H2O).19 The absence of a ν(C=O) peak at around 1700 cm−1
10−3 M, which are in the range 200–250 Ω−1cm2mol−1.25–27
.

JOURNAL OF CHEMICAL RESEARCH 2010
3
Table 1 Physical characterisation, analytical, molar conductance and mass data of the complexes
Compound
(Calcd)
Found
%C
ΛM
Formula
weight
MS/EI
Assignment
(ohm1cm2
mol−1)
%H
%N
.
[PbL1][NO3]2 2H2O
(39.58)
40.61
(45.22)
45.37
(39.86)
40.07
(41.10)
41.46
(48.98)
49.19
(40.54)
41.12
(4.95)
5.09
(6.19)
6.15
(4.98)
5.15
(5.02)
5.19
(5.99)
6.11
(5.18)
5.31
(6.60)
6.53
(7.54)
7.58
(8.30)
8.51
(6.39)
6.33
(7.62)
7.50
183
195
246
207
177
262
850
744
844
876
734
888
630
691
827
628
735
852
[PbL1-(OCH2CH2O)]+].
[Zn(H2O)L1][NO3]2]+
[Zn(H2O)L1][NO3]2 3H2O
.
[La(H2O)L1][NO3]3 H2O
[La(H2O)L1][NO3]3+H]+]
.
.
[PbL2][NO3]2 H2O
[PbL2-(OCH2CH2OCH2CH2O)]+
.
.
[ZnL2][NO3]2 H2O
[ZnL2][NO3]2 H2O+H]+
.
[LaL2][NO3]3 2H2O
(7.88)
7.73
[LaL2][NO3]3]+
Table 2 IR (cm−1) spectral data for the complexes
Compound
ν(H2O)
ν(C=N)
ionic ν(NO3−)
ν(M-O)
ν(M-N)
[PbL1][NO3]2.2H2O
[Zn(H2O)L1][NO3]2.3H2O
[La(H2O)L1][NO3]3.H2O
[PbL2][NO3]2.H2O
3368 s
3369 s
3364 s
3333 s
3348 s
3349 s
1642 m
1636 m
1635 m
1635 m
1634 m
1635 m
1384 m
1384 m
1384 m
1384 m
1383 m
1384 m
487 w
515 w
493 w
482 w
523 w
495 w
439 w
476 w
456 w
436 w
481 w
462 w
[ZnL2][NO3]2.H2O
[LaL2][NO3]3.2H2O
m, medium; s, strong; w, weak.
The mass spectrum of the complexes are given in experimental
section and shown in Table 1.25–27
soluble in DMF, DMSO and insoluble CHCl , CH Cl and less
soluble MeOH, EtOH, CH3CN. As the cryst3als ar2e u2nsuitable
for single-crystal, X-ray analyses of the complexes cannot be
done.28 Absolute structure of the complexes can be determined
using X-ray diffraction method. In this study only suggested
structure of the complexes are shown in Fig. 3. The La(III) and
Zn(II) complexes probability show octahedral geometry.29 As
the Pb(II) is large, the ligand behaves as a heptadentate or octa-
dentate ligand with the lone electron pairs of two azomethine
nitrogen atoms and the lone electron pairs of five or six oxygen
atoms in ether groups. As La(III) and Zn(II) are small, La(III)
and Zn(II) coordinate to three oxygen atoms in L1, lone elec-
tron pairs of two azomethine nitrogen atoms and one H2O, four
oxygen atoms in L2 lone electron pairs of two azomethine
nitrogen atoms.
NMR spectra
The 1H NMR spectrums are run in DMSO-d6 and gives the expected
simple spectrum, indicating the integrity of the complex in that
solvent. The 1H NMR spectrums of the complexes show a multiplet in
the range 7.1–8.0 ppm due to aromatic protons, 3,4 ppm due to H2O
protons, around 1.99–4,32 ppm due to CH2, OCH and OCH2Ph
protons and 10.4 ppm corresponding to the imine prot2ons, but no sig-
nals corresponding to the formyl or amine protons are present.26 Also
1H NMR spectral data of the complexes are given in experimental
section (Fig. 2).
Conclusion
The novel six Schiff base macrocyclic complexes are syn-
thesised by template reaction and characterised by elemental
analyses, FTIR and UV-Vis spectra, conductivity measure-
In brief, the Pb(II) metal ion can bind seven or eight atoms
and Zn(II) and La(III) ions can bind six atoms in the com-
plexes. Structure of the Pb(II) complexes are different from
structure of the Zn(II) and La(III) complexes. Similar cases
can be seen in the literature.30–34
1
ments, H NMR and mass spectra. The complexes have no
clearly defined melting point and begin to decompose in the
temperature range 250–350 oC.27 The complexes are air stable,
Fig. 2 Structure of the ligands.

4
JOURNAL OF CHEMICAL RESEARCH 2010
Fig. 3 Suggested structure of the complexes.
Received 13 September 2009;accepted 27 November 2009
Paper090784 doi: 10.3184/030823409X12609007112282
Published online: 20 January 2010
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