Supporting Information:
Synthesis and characterization of 1a-6a
Schiff basecomplexes of transition metals were obtained by usingSchiff base ligands by the aldolcondensation of 3,4-diaminopyridine with 2-hydroxy-benzaldehyde, 5-bromo-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-NO2-Sal)2Py] were obtained withthe general formula H2BX (x = 1-3)respectively. The ligands were characterized by IR, 1H NMRandelemental analysis. These ligands form complexes in 1:1 ratio with Mn2+andVO2+ions with the general formula MBx, x = 1-3.The nature and electronic property of complexes were established by IR, UV-Vis 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. 1HNMR spectra were obtained on Bruker FT-NMR AC-250 (250 MHz) spectrophotometers using TMS as an internal standard and CDCl3 and DMSO-d6 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 ligandsH2Bx(x=1,2,3)
The ligands were obtained by conventional one-step Schiff base condensation of 1,2-diamine with appropriate aldehyde in 1:2 molar stoichiometric ratio in methanol or ethanol by similar reported methodsfor symmetrical ligands.
Synthesis of H2[(Sal)2Py], H2B1: To a vigorously stirred and cool dilute solution (2–5 oC) 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 overnightuntil 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); 13C NMR (250 MHz, CDCl3): δ (ppm)= 109.4(2), 117.2, 117.4(2), 119.5, 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 45min. 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 overnight and then recrystallized from ethanol until pure product was obtained. Yield 75%.
Synthesis of VOB2 and VOB3: The VOB2 and VOB3complexes 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 %NVOB1 / C19H13N3O3V / 382.1 / green / 75 / 1601 / 1647 / 59.65 3.38 10.91
(59.71) (3.40) (10.99)
VOB2 / C19H13N3O3Br2V / 669.7 / green / 70 / 1597 / 1647 / 32.60 2.65 6.11
(32.61) (2.71) (6.00)
VOB3 / C19H11N5O7V / 472.06 / orange / 85 / 1600 / 1647 / 48.25 2.25 14.85
(48.33) (3.23) (14.82)
MnB1 / C19H13N3O2Mn / 370.1 / Dark brown / 69 / 1596 / 1694 / 61.58 3.48 11.25
(61.65) (3.51) (11.34)
MnB2 / C19H11N3O2Br2Mn / 527.9 / Dark red / 79 / 1594 / 1647 / 43.11 2.01 7.83
(43.22) (2.08) (7.95)
MnB3 / C19H11N5O6Mn / 460.06 / Brown / 76 / 1599 / 1648 / 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
Compound / λ(nm),ε(M-1 cm-1)VOB1 / 743 (188)a / 410(6808)b / - / 314(11060)c
VOB2 / 744(211)a / 420(1199)b / - / 245(40388) 290(28433)d
VOB3 / - / 423(3127)b / 367(33093)c / 313(35172)d
MnB1 / - / 434(1239)b / 310(5206)c / 270(6000)d
MnB2 / 751(102)a / 530(257)a / - / 273(1888)d
MnB3 / 741(56)a / 416(3635)b / 374(3447)c / -
a d-d transition, b charge transfer transition, c, d, e f-transition
Table S3.Electrochemical data of the Schiff base complexes MBx, x = 1-3 . M= Mn2+andVO2+ ionsa.
Complex / Epc, mV / Epa, mV / ΔEp, mVVOB1 / 520 / 980 / 64
VOB2 / 688 / 747 / 59
VOB3 / 919 / 988 / 69
MnB1 / ـــــــ / 1039 / ـــــــ
MnB2 / ـــــــ / 1005 / ـــــــ
MnB3 / ـــــــ / 1104 / ـــــــ
a Scan rate 100 mV/s, 0.1 molar solution of complex in DMF, supporting electrolyte tetrabutyl-ammonium hexafluorophosphate (TBAH). Potentials vs. Ag/AgCl reference electrode.
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