Spectral, XRD, SEM and biological properties of new mononuclear Schiff base transition metal complexes

Article abstract of DOI:10.1016/j.inoche.2013.06.014

Six new transition metal complexes derived from the reaction of 4(4-(dimethylamino) benzylideneamino) benzoic acid and Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) cations, were prepared, isolated and characterized by a range of spectral and analytic

Full text of DOI:10.1016/j.inoche.2013.06.014

Inorganic Chemistry Communications 35 (2013) 104–109
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Feature article
Spectral, XRD, SEM and biological properties of new mononuclear Schiff
base transition metal complexes
a
a
a
a
b
M.I. Khan a, , Ayub Khan , Iqbal Hussain , Murad Ali Khan , Saima Gul , Mohammad Iqbal ,
⁎
Inayat-Ur-Rahman c, Fazli Khuda d
Department of Chemistry, Kohat University of Science & Technology, Kohat, 26000, Khyber Pakhtunkhwa, Pakistan
Department of Chemistry and Biochemistry, University of Windsor, Ontario, Canada
Gandhara College of Pharmacy, Gandhara University, Peshawar, Khyber Pakhtunkhwa, Pakistan
a
b
c
d
Department of Pharmacy, University of Peshawar, Peshawar, Khyber Pakhtunkhwa, Pakistan
a r t i c l e i n f o
a b s t r a c t
Article history:
Six new transition metal complexes derived from the reaction of 4(4-(dimethylamino) benzylideneamino)
benzoic acid and Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) cations, were prepared, isolated and characterized
by a range of spectral and analytical methods including UV/Vis, FT IR, NMR, MS, powder XRD, TGA and SEM. The
complexes were formed with the deprotonation of the ligand and presented typical six-coordinated octahedral
geometry. In addition, the biological activity was evaluated by conducting in vitro anti-bacterial, anti-fungal and
anti-leishmanial screenings. All the complexes were found more active than the ligand, while complex 7 revealed
biological significance.
Received 6 May 2013
Accepted 6 June 2013
Available online 13 June 2013
Keywords:
Schiff base
Transition metal complexes
Anti-bacterial
Anti-fungal
© 2013 Elsevier B.V. All rights reserved.
Anti-leishmanial
Contents
Appendix A.
References .
Supplementary material .
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Introduction. Schiff bases produced by condensation reaction of
aromatic amines and aromatic aldehydes; which are versatile li-
gands furnishing imine N and other donor sites are responsible for
a wide range of biological and chemical applications [1–7]. Past sev-
eral decades have seen a great number of reports describing the syn-
thesis of Schiff bases with interesting structural aspects and their
biological perspective as well [8]. Transition metal ions enhance the
biological activity of different ligands, and in some cases the activity
has been solely attributed to metal ions only [9]. N,O-donor Schiff
bases containing carboxylic group have been used extensively in coor-
dination chemistry because of their versatile modes of attachment to
metal centers via monodentate, bidentate, chelate or bridging [10–12].
In literature, several reports linked the significance of biological activity
of metal complexes with the metal ion rather than with the ligands [13].
Schiff base transition metal complexes 4-dimethylaminobenzaldehyde
(Ehrlich's Reagent) are reported in the literature; while little is known
about the synthesis and biological study of 4-(4-(dimethylamino)
benzylideneamino) benzoic acid (Fig. 1) and its transition metal com-
plexes [14]. This report is a continuation of the previous work on biolog-
ically active coordination compounds, describing the structures and
in vitro anti-bacterial, anti-fungal and anti-leishmanial screenings of
4-(4-(dimethylamino) benzylideneamino) benzoic acid and its divalent
Mn, Fe, Co, Ni, Cu and Zn transition metal complexes [15,16]. Ligand and
complexes were screened in vitro for their anti-bacterial (Pseudomonas
aeruginosa, Bacillus subtilis, Methicillin-resistant staphylococcus aureus
(MRSA), Klebsiella pneumoniae, and Escherichia coli); anti-fungal
(Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger and Fusarium
solani) and anti-leishmanial (Leishmania major (MHOM/PK/88/DESTO),
Leishmania tropica (K27) and Leishmania donovani (H43)) potential.
Experimental. Ethanolic solutions of 4-aminobenzoic acid (1.02 g,
7.4453 mmol in 30 ml) of 4-(dimethylamino)benzaldehyde (1.12 g,
7.4453 mmol, 30 ml) were mixed together at room temperature. The
resulting mixture was stirred at room temperature, and after 5 min
the color of the reaction mixture gave a yellowish appearance; the reac-
tion mixture was stirred for 2 h. Ethanol was evaporated at room
⁎
Corresponding author. Tel.: +92 922 554437; fax: +92 922 554556.
E-mail address: gorikhan@kust.edu.pk (M.I. Khan).
1387-7003/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.inoche.2013.06.014

M.I. Khan et al. / Inorganic Chemistry Communications 35 (2013) 104–109
105
Fig. 1. 4-(4-dimethylamino)benzylideneamino)benzoic acid.
temperature and the solid obtained was washed twice with ether
(15 ml) and recrystallized from 90% ethanol.
NH2C6H4COOH þ OHCC6H4NðCH3Þ2→NðCH3Þ2C6H4CHNC6H4COOH þ H2O
All the complexes were synthesized by the same methodology,
briefly an ethanolic solution of the freshly prepared ligand was added
in portions to the corresponding metal salt solution in the same solvent
in 2:1 molar ratio. Instantly, precipitation occurred; colors of the precip-
itates depended upon the metals. The precipitate was filtered and
washed with excess of distilled water, then ethanol and in the end
with diethyl ether to remove unreacted ligand and impurities. Instru-
mentation and acquisition of other spectral data, in vitro biological ac-
tivity protocols were conducted as reported earlier [15–19].
Fig. 2. Octahedral geometry of complexes 2–7 and NMR numbering scheme where
M = MnII, FeII, CoII, NiII, CuII and ZnII.
the L → MCT band is followed by a long broad tail at 18,868 cm−1
which is due to a d → d transition in an octahedral arrangement [28].
Co(II) complex furnished two bands at 16,452 cm−1 and 18,530 cm−1
respectively for 4Tı(F) → 4A2(F) and 4Tı(F) → 4Tı(P) transitions;
Results and discussion. In the free ligand, the band at 1650 cm−1
is assigned to ν(C_N) frequency; after complexation, this band is
shifted to lower frequency. Shifting of the ν(C_N) vibration to
lower frequency (1612–1581 cm−1) is due to C_N → M coordination
[20]. Characteristic broad band in the range of 3300–3500 cm−1 is
assigned to carboxylic group in the ligand's spectrum that disappeared
after complexation which proved deprotonation of the ligand; similarly
presence of coordinated water is confirmed by the presence of another
broad band at 3160–3550 cm−1 [21]. Coordinated water molecule is
also seen as a weak band at 840 cm−1 due to rocking mode while
band at 605–660 cm−1 indicated the presence of water of crystalliza-
tion [21]. Difference of symmetric and asymmetric vibrations of the car-
bonyl group i.e. Δν(C_Oasym\C_Osym) provided valuable information
about the coordination mode of COOH group in the complexes (2–7).
The values of Δν less than 200 cm−1 indicate the monodentate coordi-
nation mode of carboxylic group [21]. In free ligand, sharp dips were ob-
served at 1685 cm−1 and 1472 cm−1 (Δν: 213 cm−1) for C_Oasym and
C_Osym respectively, while in complexes these shifted to lower fre-
quencies and the magnitude of Δν also went below 200 cm−1; briefly
190, 181, 183, 183, 182 and 193 cm−1 for complexes 2–7 respectively.
This indicated the involvement of monodentate approach of COOH
group of the ligand with the central metal cations [22,23]. New bands
appeared in the spectra of the complexes at 534–577 cm−1, corre-
sponding to O → M and 425–468 cm−1 due to the N → M vibrations
which support the involvement of N and O atoms in complexation
with metal ions under investigation [24]. Characteristic strong band at
1332 cm−1 is assignable to the stretching vibration of aromatic C\N
group that remained unchanged after complexation which confirmed
the non-coordination of dimethylamino moiety [25]. All this discussion
indicates that the ligand is bidentate coordinating via O,N in octahedral
geometry (Fig. 2) and also proves 1:2 metal to ligand stoichiometry
[26].
Cu(II) complex displayed four bands at 37,037–35,714 cm−1
,
25,641–25,316 cm−1, 22,222–21,739 cm−1 due to π–π* within or-
ganic molecule and 16,393–16,129 cm−1 attributable to π–π* of
C_N group (L → Cu2+) charge transfer after complex formation;
2
while the last band can be assigned to B1g
→
2Eg transition of the
Cu(II) ion in tetragonal elongation of octahedral geometry [29]. Similar-
ly, Ni(II) complex also exhibited two additional bands with 18,868–
3
18,519 cm−1 and 13,514–13,333 cm−1 due to the A2g
→
3T1g(ν1)
and 3A2g
→
3T1g(F)(ν2) transitions. This indicated octahedral geometry
around the Ni(II) ion and is further supported by a ν2/ν1 ratio of (1.4,
1.39), which corresponds to an octahedral geometry [29]. Mn(II)
complex exhibited electronic spectral bands at 18,868 cm−1 and
25,316 cm−1 corresponding to 6A1g
→
4T1g(P) (ν3) transition, typi-
cal of octahedral Mn(II) complex [30].
1H NMR spectral data of the ligand and its complexes were recorded in
DMSO-d6 for the evaluation of the number & nature of all the protons rel-
ative to TMS with chemical shifts given in ppm (DMSO: ≈2.0 ppm). All
the protons resonated at appropriate positions i.e. COOH group in the li-
gand gives a broad singlet at 12.85 ppm, a singlet for azomethine hydro-
gen (CH_N) at 8.73 ppm, aromatic ring attached to dimethylamino 6.5–
7.35 ppm, aromatic protons of benzoic phenyl ring at 7.3–8.0 ppm and
singlet at 2.94 ppm for methyl groups. The peak near 11 ppm is absent
metal(II) complexes, confirmed the deprotonation of CO\O\H.
The azomethine signal is shifted to downfield as well and indicated
deshielding of the azomethine proton due to coordination to the
metal ion through the azomethine nitrogen atom [31]. 13C NMR
spectral data corroborated the mode of bonding situation depicted by
The electronic spectrum gives information on the electronic envi-
ronment of the metal; the electronic absorption spectra are determined
in DMSO in the range of 200–1000 nm i.e. 50,000–10,000 cm−1. Pure li-
gand showed three intensive bands at 42,194 cm−1, 37,037 cm−1 and
29,850 cm−1 suggesting the presence of π–π* and n–π* transitions
[27]. The π–π* transition in the complexes (2–7) is shifted to a longer
wavelength as a consequence of coordination to the metal, confirming
the formation of Schiff base metal complexes. Fe(II) complex display
maximum absorption bands centered at 30,211–28,490 cm−1; ascribed
to an intramolecular charge transfer transition in the complexed ligand.
In addition, a band is seen at 23,809–21,276 cm−1 that can be attrib-
uted to charge transfer from ligand to metal (L → M). Furthermore,
Fig. 3. Thermograms of compounds 1–6.

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M.I. Khan et al. / Inorganic Chemistry Communications 35 (2013) 104–109
Fig. 4. X-ray diffraction pattern of Zn(II) complex.
Fig. 5. Scanning electron micrographs of (a) ligand, (b) Cu(II) complex and (c) Zn(II) complex.
1H NMR; carbon attached to the hydroxyl group in the ligand is ob-
served at 158.5 ppm, which after complexation shifted to >168 ppm,
and confirmed the coordination of the ligand through oxygen. The
deshielding of the azomethine carbon is also confirmed by a signal
at >173 ppm; which provided support that the azomethine nitrogen
is also involved in the complexation (C_N → M) [32,33].
FAB spectrum of the ligand showed molecular ion peak at m/z 268
equal to its molecular mass. FAB spectrum of Co(II) complex showed
a molecular ion peak M+ at m/z 629 that is equivalent of its molecu-
lar mass, while that of Cu(II) at m/z 634 and Zn(II) at m/z 635 are at-
tributable to [M + 1] and [M + 2] respectively. Co(II), Cu(II) and
Zn(II) complexes lost two water molecules and thereby displayed
fragments at m/z 593, 597 and 598. Further, [L + H]+ observed at
m/z 268 is furnished by all the complexes because of demetallation.
Complexes show [M]+ peaks in good agreement with the structures
proposed by elemental analysis and spectral data and molar stoichiom-
etry [34−36]. TGA study was carried out up to 1000 °C; thermograms
(1–7) showed gradual weight loss, indicating decomposition by frag-
mentation with increase in temperature. For all the complexes, follow-
ing steps were observed (i) small weight loss in the range of 40–110 °C
assignable to the loss of water of crystallization, (ii) maximum weight
loss in the range of 130–170 °C which is attributable to the loss of coor-
dinated water (iii) and gradual weight loss in the range of 540–1000 °C
that can be assigned to complete decomposition of ligand moiety
around the metal ion respectively and finally the complex is converted
into its metal oxide [37]. Thermograms of compounds 1–6 are plotted in
Fig. 3; showing approximately 80% weight loss up to 1000 °C which is
according to the aforementioned three steps.
During powder X-ray diffraction analysis (Fig. 4), only Ni(II) and
Zn(II) complexes exhibited sharp peaks, while no peaks were observed
for the rest of the complexes indicating their amorphous nature. Line
broadening of the crystalline diffraction peak in the Zn(II) complex
showed higher crystallinity. Crystalline nature of the complexes
was indicated by comparing the diffractograms of the ligand and
Fig. 6. Anti-bacterial and anti-fungal activity of compounds 1–7 and standards at a: 25, b: 50 and c: 100 μg/ml respectively.

M.I. Khan et al. / Inorganic Chemistry Communications 35 (2013) 104–109
107
Fig. 7. Zones of inhibition by compounds 6 and 7 against Pseudomonas aeruginosa and
Bacillus subtilis.
Fig. 9. Anti-fungal activity of 1 and 4 against A. flavus, A. fumigatus, A. niger and F. solani.
complexes. Based on literature, this may be due to the incorporation
of water molecules into the coordination sphere [38]. Although sin-
gle crystal X-ray crystallography is the most precise source of infor-
mation regarding the structure of a complex, the difficulty of
obtaining suitable crystals in proper symmetric form has rendered
this method unsuitable for such a study.
capacity to inhibit the metabolic growth of the investigated bacteria
(Fig. 6). All the complexes displayed increased activity compared to
that of the ligand; while among the complexes, Zn(II) complex
furnished significant activity under identical experimental conditions
(Figs. 7 and 8). The possible mode of increased toxicity of the complexes
may be explained by Tweedy's chelation theory, which states that che-
lation reduces the polarity of the central metal atom because of partial
sharing of its positive charge with the ligand which favors the perme-
ation of the complexes through the lipid layer of cell membranes [39].
Furthermore, hydrogen bonding may affect the mode of action of com-
pound probably through the azomethine (C_N) group and the active
centers of cell constituents resulting in the interference with normal
cell processes [39–41]. In vitro anti-fungal activity of all the synthesized
compounds was carried out against A. flavus, A. fumigatus, A. niger and
F. solani by agar tube dilution method using Miconazole as reference
and significant activity results were observed at 25, 50 and 100 μg ml−1
concentrations. Significant improvement in ligand's anti-fungal effect
upon complexation was observed; the increase in anti-fungal activity is
due to the structural changes after coordination which can be seen in
Figs. 9 and 10. The increase in activity with the increase in concentration
of the test compound, and the variation in the effectiveness of the differ-
ent compounds against different organisms is due to the impermeability
of the microbial cells or ribosomal difference in the microbial cells
[42–44]. Anti-leishmanial activity findings are depicted in Fig. 11; it was
clearly evident from the plotted data that all the complexes showed excel-
lent activity in comparison to the ligand and the standard drug. This
enhancement in activity may be attributed to the structural changes
taking place in vitro during the assaying and it is suggested that the
metal–ligand interactions are a major deciding factor responsible for the
increase in anti-leishmanial activity.
The SEM analysis was here carried out to check the surface morphol-
ogy of the selected complexes and the micrographs obtained are given
in Fig. 5. The micrograph of the Schiff base ligand is given in Fig. 5(a);
it can be seen that it gave a rock like appearance with a numerous ter-
ritorial patches. These facts revealed the amorphous nature of the ligand
with complicated interpretation due to unclear appearance. On the
other hand, the micrographs of copper and nickel complexes Fig. 5(b
& c) indicated that the presence of well defined crystals free from any
shadow of the metal ion on their external surface had a twisted fiber
and grass like morphology. It is evident from the SEM study that in all
the synthesized metal complexes, crystals were found to grow up
from just a single molecule to several molecules in an aggregate distri-
bution with particle sizes starting from a few nanometers to several
hundred. In addition, different characteristic shapes of metal Schiff
base complexes were identified and these SEM images were quite dif-
ferent from that of Schiff base. The difference in the shape of the Schiff
base metal complex crystal aggregates deposited on the thin films
was mainly dependent on the metal ions.
The experimental data obtained from elemental analysis are in
good agreement to support 1:2 metal to ligand stoichiometry. The
molar conductance measurements suggested the absence of ionic
character of the monovalent anions of the ligand coordinated to
metal ion. Molar conductance values in DMSO solutions of the com-
plexes that fell in the range of 17−19 Ω−1 cm2 mol−1 proved that
the complexes were non-electrolytes (1 × 10−3 mol dm−3). The
coordinated water analysis of the complexes indicated two water
molecules per molecule.
Conclusions. Condensation reaction of 4-dimethylaminobenzalde-
hyde and 4-aminobenzoic acid resulted in the production of Schiff base li-
gand in excellent yield. The ligand coordinates in 2:1 ligand to metal ratio
as a monobasic bidentate (ON) donor in all the complexes. The analytical,
thermal, molar conductance, vibrational, resonance, mass and electronic
spectral study suggested the structures shown in Fig. 2 in octahedral
Effectiveness of an antimicrobial agent is based on the zones of
inhibition; based on their respective zones of inhibition, the data
obtained showed that the synthesized complexes have got the
Fig. 8. Zone of inhibition by compounds 6 and 7 against Escherichia coli and Methicillin-
resistant Staphylococcus aureus (MRSA).
Fig. 10. Anti-fungal activity of 6 and 7 against A. flavus, A. fumigatus, A. niger and F. solani.

108
M.I. Khan et al. / Inorganic Chemistry Communications 35 (2013) 104–109
[15] M.I. Khan, S. Gul, I. Hussain, M.A. Khan, M. Ashfaq, I. Rahman, F. Ullah, G.F. Durrani, I.B.
Baloch, R. Naz, In vitro anti-leishmanial and anti-fungal effects of new SbIII carboxylates,
Org. Med. Chem. Lett. 1 (2011) 2–7, http://dx.doi.org/10.1186/2191-2858-1-2.
[16] M.I. Khan, M.K. Baloch, M. Ashfaq, S. Gul, Organotin(IV) esters of 4-maleimido-benzoic
acid: synthesis, characterization and in vitro anti-leishmanial effects, J. Braz. Chem. Soc.
20 (2009) 341–347, http://dx.doi.org/10.1590/S0103-50532009000200020;
M. Ashfaq, M.I. Khan, M.K. Baloch, A. Malik, Biologically potent organotin(IV)
complexes of 2-maleimidoacetic acid, J. Organomet. Chem. 689 (2004)
238–245, http://dx.doi.org/10.1016/j.jorganchem.2003.10.007.
[17] Ligand 1: Yield: 1.35 g, 70%. MP: 265–267 °C; Ω (S·cm2·mol−1): 11.21. 1H NMR
(400 MHz, DMSO-d6): CH, δ = 9.65 ppm (s, 1-H); CH, δ = 7.68 ppm (d, 3-H, J:
8.8 Hz); CH, δ = 6.79 ppm (d, 4-H, J: 8.8Hz); CH, δ = 8.47 ppm (s, 6-H); CH,
δ = 7.61 ppm (d, 8-H, J: 8.8 Hz); CH, δ = 6.54 ppm (d, 9-H, J: 8.8 Hz); CH3,
δ = 3.03 ppm (s, 11-H). 13C NMR (100 MHz, DMSO-d6): COOH, δ = 189.72 ppm;
C_C (aromatic), δ = 110.12–155.42 ppm; C_N, δ = 160 ppm; CH3, δ = 38.86.
Anal. Calcd. for C16H16N2O2: C, 71.62; H, 6.01; N, 10.44. Found: C, 71.58; H, 5.88; N,
10.22. FT IR: 3391 (COOH), 1650 (C_N), 1472 (C_O)sym, 1687 (C_O)asym, 1601
(C_C) cm−1. MS: 268. [2] Yield: 54%. MP: 210–220 °C; Ω (S.cm2.mol−1): 11.21. 1H
NMR (400 MHz, DMSO-d6): CH (azomethine), δ = 9.73 ppm (s, 1-H); CH (aromatic),
δ = 6.55–8.42 ppm. 13C NMR (100 MHz, DMSO-d6): COO, δ = 182.18 ppm; C_C (ar-
omatic), δ = 114.55–159.12 ppm; C_N, δ = 162.31 ppm; CH3, δ = 39.47. Anal.
Calcd. for C32H34MnN4O6: C, 61.44; H, 5.48; N, 8.96; Mn, 8.78. Found: C, 61.12; H,
5.11; N, 8.66; Mn, 8.52. FT IR: 1600 (C_N), 1465 (C_O)sym, 1655 (C_O)asym,
1600 (C_C), 548 (O → M), 436 (C_N → M) cm−1. MS: 625. [3] Yield: 76%. MP:
Fig. 11. Anti-leishmanial activity of compounds 1–8 and standard.
arrangement. TGA showed that the complexes are thermally more stable
than the ligand. The biological activity results solely depend upon the co-
ordination sphere of the central metal ion and the role of the ligand is vital
in facilitating the transportation to the target sight.
252–254 °C;
Ω
(S·cm2·mol−1): 17.11. 1H NMR (400 MHz, DMSO-d6): CH
(azomethine), δ = 9.69 ppm (s, 1-H); CH (aromatic), δ = 6.59–8.32 ppm. 13C NMR
(100 MHz, DMSO-d6): COO, δ = 186.21 ppm; C_C (aromatic), δ = 114.43–
160.04 ppm; C_N, δ = 165.00 ppm; CH3, δ = 40.02. Anal. Calcd. for C32H34FeN4O6:
C, 61.35; H, 5.47; N, 8.94; Fe, 8.91. Found: C, 61.03; H, 5.31; N, 8.67; Fe, 8.55. FT IR:
1612 (C_N), 1470 (C_O)sym, 1651 (C_O)asym, 1597 (C_C), 534 (O → M), 425
(C_N → M) cm−1. MS: 626. [4] Yield: 69%. MP: 256 °C; Ω (S·cm2·mol−1): 20.31.
1H NMR (400 MHz, DMSO-d6): CH (azomethine), δ = 9.62 ppm (s, 1-H); CH (aromat-
ic), δ = 6.50–8.21 ppm. 13C NMR (100 MHz, DMSO-d6): COO, δ = 181.33 ppm; C_C
(aromatic), δ = 118.22–167.44 ppm; C_N, δ = 169.07 ppm; CH3, δ = 40.11. Anal.
Calcd. for C32H34CoN4O6: C, 61.05; H, 5.44; N, 8.90; Co, 9.36. Found: C, 60.87; H, 5.21;
N, 8.64; Co, 9.02. FT IR: 1597 (C_N), 1483 (C_O)sym, 1666 (C_O)asym, 1611
(C_C), 540 (O → M), 445 (C_N → M) cm−1. MS: 629. [5] Yield: 52%. MP: 250 °C;
Appendix A. Supplementary material
Supplementary data to this article can be found online at http://
dx.doi.org/10.1016/j.inoche.2013.06.014.
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Ω
(S·cm2·mol−1): 14.89. 1H NMR (400 MHz, DMSO-d6): CH (azomethine),
δ = 9.55 ppm (s, 1-H); CH (aromatic), δ = 6.44–8.02 ppm. 13C NMR (100 MHz,
DMSO-d6): COO, δ = 183.0 ppm; C_C (aromatic), δ = 120.1–163.75 ppm; C_N,
δ = 170.0 ppm; CH3, δ = 39.69. Anal. Calcd. for C32H34NiN4O6: C, 61.07; H, 5.45; N,
8.90; Ni, 9.33. Found: 59.71; H, 5.18; N, 8.53; Ni, 8.92. FT IR: 1601 (C_N), 1488
(C_O)sym, 1670 (C_O)asym, 1622 (C_C), 555 (O → M), 433 (C_N → M) cm−1
.
MS: 628. [6] Yield: 53%. >300 °C; Ω (S·cm2·mol−1): 11.48. 1H NMR (400 MHz,
DMSO-d6): CH (azomethine), δ = 9.41 ppm (s, 1-H); CH (aromatic),
δ = 6.42–7.94 ppm. 13C NMR (100 MHz, DMSO-d6): COO, δ = 180.4 ppm; C_C (ar-
omatic), δ = 124.2–165.0 ppm; C_N, δ = 175.2 ppm; CH3, δ = 40.11. Anal. Calcd.
for C32H34CuN4O6: C, 60.60; H, 5.40; N, 8.83; Cu, 10.02. Found: 60.31; H, 5.22; N,
8.66; Cu, 9.69. FT IR: 1605 (C_N), 1479 (C_O)sym, 1669 (C_O)asym, 1629 (C_C),
549 (O → M), 458 (C_N → M) cm−1
. MS: 633. [7] Yield: 51%. >300 °C; Ω
(S·cm2·mol−1): 19.96. 1H NMR (400 MHz, DMSO-d6): CH (azomethine),
δ = 9.33 ppm (s, 1-H); CH (aromatic), δ = 6.51–7.82 ppm. 13C NMR (100 MHz,
DMSO-d6): COO, δ = 178.04 ppm; C_C (aromatic), δ = 126.14–167.76 ppm; C_N,
δ = 175.87 ppm; CH3, δ = 40.43. Anal. Calcd. for C32H34ZnN4O6: C, 60.43; H, 5.39; N,
8.81; Zn, 10.28. Found: C, 60.08; H, 5.12; N, 8.61; Zn, 9.88. FT IR: 1581 (C_N), 1482
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