Supporting Information:
Synthesis and characterization of 1a-6a
Schiff base complexes of transition metals were obtained by using Schiff base ligands
by the aldol condensation of 3,4-diaminopyridine with 2-hydroxy-benzaldehyde, 5bromo-2-hydroxybenzaldehyde or 5-nitro-2-hydroxybenzaldehyde in the 1:2 molar
ratio. The tetradentate ligands H2[(Sal)2Py], H2[(5-Br-Sal)2Py] and H2[(5-NO2Sal)2Py] were obtained with the general formula H2BX (x = 1-3) respectively. The
ligands were characterized by IR, 1H NMR and elemental analysis. These ligands
form complexes in 1:1 ratio with Mn2+ and VO2+ ions with the general formula MBx,
x = 1-3. The nature and electronic property of complexes were established by IR, UVVis spectra, A.A., elemental analysis (CHN) and cyclic voltammetry.
Experimental
Material and Physical Measurement
VO(acac)2 and 2-hydroxybenzaldehyde were obtained from Aldrich. All others were
obtained from Merck.
Infrared spectra were recorded using a shimadzu IR 460 spectrophotometer using KBr
pellets. Electronic absorption spectra were recorded on a Varian UV-Vis Cary 100E
spectrophotometer. 1H NMR spectra were obtained on Bruker FT-NMR AC-250 (250
MHz) spectrophotometers using TMS as an internal standard and CDCl3 and DMSOd6 as solvents. Elemental analyses (C, H, N) were performed using a Heraeous
Elemental Analyzer CHN-O-Rapid (Elemental-Analyses system, GmbH-West
Germany). Melting points were determined by a B-540 Buchi melting point apparatus.
Cyclic voltammograms (CVs) were obtained using an electrochemical system (Palm
Sense, The Netherlands) in conjunction with a three-electrode system and a personal
computer for data storage and processing. An Ag/AgCl (3 M KCl KCl) reference
electrode, a Pt wire (counter electrode) and a glassy carbon working electrode were
employed for the electrochemical studies. Voltammetry measurements were
performed at room temperature in DMF solution with 0.1 M tetrabutylammonium
hexaflourophosphate as the supporting electrolyte.
Preparation of the Schiff bases ligands H2Bx(x = 1, 2, 3)
The ligands were obtained by conventional one-step Schiff base condensation of 1,2diamine with appropriate aldehyde in 1:2 molar stoichiometric ratio in methanol or
ethanol by similar reported methods for symmetrical ligands.
Synthesis of H2[(Sal)2Py], H2B1: To a vigorously stirred and cool dilute solution (2–5
o
C) of 0.1 mmol (10.9 g) of the 3,4-diaminopyridine in 30 mL of anhydrous ethanol,
was added a cooled solution of 0.2 mole (24.00 g) 2-hydroxybenzaldehyde in 40 mL
anhydrous ethanol, drop by drop. After the addition was completed, the mixture was
stirred for 45 min at 75˚C in an oil bath. The mixture was concentrated by solvent
evaporation under vacuum until the orange H2[(Sal)2Py] precipitated. The product was
filtered and washed using distilled water, then washed with cooled ethanol, followed
by recrystallized from ethanol and drying at 70˚C overnight until pure product
obtained. Yield 75%, base on 3,4-diaminopyridine. M.p. 107-110˚C; elemental
analysis for C19H15N3O2; Mol. Wt.: 317.34; calcd. (%):C 71.91, H 4.76, N 13.24;
found: C 72.11, H 4.60, N 13.06. 1H NMR (250 MHz, CDCl3): δ (ppm) = 12.59
(s,2H, OH), 8.6 (s,2H, CH = N), 8.1(d,2H, CH=N pyridine ring), 6.6-7.5 (m,9H,
ArH);
C NMR (250 MHz, CDCl3): δ (ppm)= 109.4(2), 117.2, 117.4(2), 119.5,
13
119.8, 132.6(2), 133.(2), 136.9, 139.1, 145.2, 148.6, 160.7, 161.5, 163.6(2); Selected
IR bands (KBr): ν (cm−1) = 3315, 1668, 1603, 1183, 746. UV-Vis data in DMF:
λ(nm), ε(M-1 cm-1)= 366(3287), 318(3626).
Synthesis of H2[(5-Br-Sal)2Py], H2B2: This ligand was prepared with 0.2 mole (40 g)
of 5-bromo-2-hydroxybenzaldehyde according to the same procedure as that
employed for H2B1. Yield 70%, yellow solid. M.p. 180-183 oC; elemental analysis for
C19H13N3O2Br2; Mol. Wt.: 475.13; calcd. (%): C 48.03, H 2.63, N 8.84; found: C
48.26, H 2.71, N 8.68. 1H NMR (250 MHz, CDCl3): δ (ppm) = 12.59 (s,2H, OH),
8.55 (s,2H, CH = N), 8.15(d,2H, CH=N pyridine ring), 6.7-7.6 (m,7H, ArH). Selected
IR bands (KBr): ν (cm−1) = 3070, 1669, 1609, 1273, 818. UV-Vis data in DMF:
λ(nm), ε(M-1 cm-1)= 367(3330) ; 327(3613).
Synthesis of H2[(5-NO2-Sal)2Py], H2B3: The ligand was prepared with 0.2 mole (33 g)
of 5-nitro-2-hydroxybenzaldehyde according to the same procedure as that employed
for H2B1. Yield 70%, orange solid. M.p. 280-283 oC; elemental analysis for
C19H13N5O6; Mol. Wt.: 407.34; calcd. (%):C 56.02, H 3.22, N 17.19; found: C 56.21,
H 3.10, N 16.97. 1H NMR (250 MHz, CDCl3): δ (ppm) = 13.6 (s,2H, OH), 9.8 (s,2H,
CH = N), 8.7 (d,2H, CH=N pyridine ring), 6.7-7.7 (m,7H, ArH. Selected IR bands
(KBr): ν (cm−1) = 3335, 1632, 1608, 1288, 826. UV-Vis data in DMF: λ(nm), ε(M-1
cm-1)= 365(3229), 309(3686).
Preparation of the Schiff base complexes MBx, x = 1-3, M = Mn2+and VO2+
Synthesis of vanadyl Schiff base complexes VO[(Sal)2Py], VOB1: To a stirred and hot
solution of 3 mmol (0.95 g) H2[(Sal)2Py], H2B1 in 40 mL ethanol was added a hot
solution of 3 mmol (0.80 g) VO(acac)2 in 30 mL methanol. The orange color of the
solution changed in a few minutes. The reaction mixture was then refluxed for 45
min. The green color solution was concentrated and cooled to yield green participate.
The product was filtered, washed with diethyl ether followed by drying at 60 oC over
night and then recrystallized from ethanol until pure product was obtained. Yield
75%.
Synthesis of VOB2 and VOB3: The VOB2 and VOB3 complexes were prepared by use
of 3 mmol (1.4 g) of the H2B2 and 3 mmol (1.2 g) of the H2B3, respectively, according
to the same procedure as employed for VOB1.
Synthesis of MnBx , x = 1-3: The MnB1, MnB2 and MnB3complexes were prepared by
use of 3 mmol (0.75 g) of the Mn(acac)2 instead of VO(acac)2, according to the same
procedure as employed for VOB1, VOB2 and VOB3complexes.
Table S1. The yields, elemental analysis, IR and UV-Vis spectroscopy data and other
physico-chemical properties of the Schiff base complexes MBx, x = 1-3.
Compound
Formula
M.Wt.
(g/mol)
Color
Yield
(%)
(C=N),
cm-1
(C=N),
cm-1
pyridine
Fou nd (calc)
% C %H
%N
VOB1
C19H13N3O3V
382.1
green
75
1601
1647
VOB2
C19H13N3O3Br2V
669.7
green
70
1597
1647
VOB3
C19H11N5O7V
472.06
orange
85
1600
1647
MnB1
C19H13N3O2Mn
370.1
69
1596
1694
MnB2
C19H11N3O2Br2Mn
527.9
79
1594
1647
MnB3
C19H11N5O6Mn
460.06
Dark
brown
Dark
red
Brown
76
1599
1648
59.65 3.38 10.91
(59.71) (3.40) (10.99)
32.60 2.65 6.11
(32.61) (2.71) (6.00)
48.25 2.25 14.85
(48.33) (3.23) (14.82)
61.58 3.48 11.25
(61.65) (3.51) (11.34)
43.11 2.01 7.83
(43.22) (2.08) (7.95)
49.58 2.32 15.20
(49.60) (2.39) (15.21)
Table S2. Electronic spectral data of the Schiff base complexes MBx, x = 1-3 in
DMF
λ(nm), ε(M-1 cm-1)
743 (188)a 410(6808)b 314(11060)c
744(211)a 420(1199)b 245(40388) 290(28433)d
423(3127)b 367(33093)c 313(35172)d
434(1239)b 310(5206)c 270(6000)d
751(102)a 530(257)a 273(1888)d
741(56)a
416(3635)b 374(3447)c a
d-d transition, b charge transfer transition, c n   * , d    * , e f-transition
Compound
VOB1
VOB2
VOB3
MnB1
MnB2
MnB3
Table S3. Electrochemical data of the Schiff base complexes MBx, x = 1-3 . M=
Mn2+ and VO2+ ionsa.
Complex Epc, mV
VOB1
520
2
VOB
688
3
VOB
919
1
MnB
‫ـــــــ‬
2
MnB
‫ـــــــ‬
3
MnB
‫ـــــــ‬
Epa, mV
980
747
988
1039
1005
1104
ΔEp, mV
64
59
69
‫ـــــــ‬
‫ـــــــ‬
‫ـــــــ‬
a
Scan rate 100 mV/s, 0.1 molar solution of complex in DMF, supporting electrolyte tetrabutylammonium hexafluorophosphate (TBAH). Potentials vs. Ag/AgCl reference electrode.
References:
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[s2] D.M. Boghaei, S. Mohebi, J. Mol. Catal. A: Chem. 179 (2002) 41.
[s3] S. Mohebi, D.M. Boghaei, Synth. React. Inorg. Met.-Org. Chem. 34 (2004) 611.
[s4] S. Mohebi, D.M. Boghaei, A.H. Sarvestani, A. Salimi, Appl. Catal. A: Gen. 278
(2005) 263.
[s5] S. Mohebbi, S. Raiati, F. Nikpour, J. Mol. Catal. A: Chem. 256 (2006) 265.
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