Introduction
Schiff bases constitute the important class of organic compounds containing azomethine group (-CH=N-) which is generally obtained by the condensation of aromatic aldehydes or ketones with amines. Nowadays research dealing with the coordination complexes of Schiff bases with various metal ions has expanded enormously. Schiff bases act as a good chelating agent 1 and exhibit extraordinary properties with metal complexes. Some heterocyclic Schiff base ligands form metal chelates 2 and play a very important role in medicinal chemistry. Schiff bases due to their wide range of applications becoming more and more interesting for the researchers.The Schiff bases are very much important in bioinorganic chemistry,biomedical chemistry, 3-4 pharmaceutical industries, catalysis 5-9, polymer chemistry, supramolecular chemistry, catalysis, material science.They have been found to possess antimicrobial, antifungal, antimalarial, antiviral activities.10-15. Recently Schiff bases having halogen groups and their metal complexes have been found to possess special interest due to their pharmacological properties. These metal complexes of Schiff base shows various biological activities 16-17. These are also used as anticancer agents. Generally, ketones show less reactivity than aldehydes. A large number of Schiff bases were synthesized from hydroxy aldehydes but lesser work has been done on hydroxy propiophenone. Schiff bases act as an effective chelating agent when it has an OH group in the vicinity of the azomethine (>C=N- ) group and forms metal complexes that possess outstanding biological properties.
Because of the biological importance of Schiff bases, we have synthesized some new Schiff bases from chloro hydroxy propiophenone, bromo hydroxy propiophenone, and methyl hydroxy propiophenone with benzylamine, p- toluidine, aniline, and propylamine, and these newly prepared ligands were characterized by spectral analysis.
Material and Method
Chemicals used were of analytical grade without further purification. Iodination of bromo and chloro 2’ hydroxypropiophenone was done by using iodine and iodic acid[18].Melting points were determined by an open capillary tube and were uncorrected. Thin layer chromatography was used to determine the progress of the reaction.1H NMR spectra of all theligands were recorded in DMSO solvent using Brucker Avance Neo 500MHzspectrophotometer, FTIR spectra were recorded on Shimadzu spectrometer and themass spectra was recorded on Q-TOFMicromass (ESI-MS).UV spectra were recordedon a W-1800 series spectrometer.
General Procedure for the synthesis of Schiff bases
All the Schiff base ligands were synthesized by refluxing substituted hydroxy propiophenone (0.01M) with different aliphatic and aromatic amines (0.01M) for 3-5 hrs. The reaction was monitored after the regular interval by TLC. When the reaction was complete, cooled the resulting mixture at room temperature and then transferred in ice-cold water. The yellow product separated which was then recrystallized by hot ethanol.
Result and Discussion
The analytical and physical data of Schiff base ligand are given in the following table 1. All the ligands were yellow colored, solid, and stable at room temperature. The UV spectra of the ligands showed the strong absorption bands at 330-350 nm and 280-290 nm which were attributed to n-n* and π-π* transitions respectively.Strong IR bands were observed in the range 3000-3100 cm-1 which is the characteristic of the phenolic OH group. The details of the spectroscopic data are illustrated below the table.
Table 1: Physical and Analytical Data of Schiff Base Ligand
| Ligand | R1 | R2 | R | Melting Point (0c) | Yield(%) | Elemental Analysis (%) calculated(found) | ||
| C | H | N | ||||||
| 2a | H | Br | C6H5CH2 | 110 | 68 | 60.39 (60.56) | 5.10 (5.04) | 4.35 (4.41) |
| 2b | I | Br | C6H5-CH2 | 122 | 62 | 36.39 (36.54) | 3.72 (3.80) | 3.44 (3.55) |
| 3a | H | CH3 | C6H5 | 131 | 66 | 80.20 (80.33) | 7.16 (7.11) | 5.75 (5.85) |
| 3b | I | Br | C6H5 | 130 | 55 | 41.89 (41.95) | 3.08 (3.03) | 3.36 (3.26) |
| 4a | H | CH3 | C6H4-OCH3 | 85 | 54 | 80.50 (80.63) | 7.56 (7.50) | 5.43 (5.53) |
| 4b | I | Cl | C6H4-OCH3 | 125 | 55 | 48.14 (48.06) | 3.82 (3.75) | 3.55 (3.5) |
| 5a | H | Br | n-C3H7 | 82 | 54 | 53.35 (53.53) | 5.77 (5.94) | 5.08 (5.20) |
| 5b | H | Cl | n-C3H7 | 72 | 61 | 70.32 (70.20) | 5.91 (5.85) | 5.22 (5.11) |
| 6a | H | Cl | Iso- C3H7 | 90 | 65 | 70.32 (70.20) | 5.91 (5.85) | 5.22 (5.11) |
| 6b | I | Cl | Iso- C3H7 | 110 | 40 | 40.89 (41.08) | 4.23 (4.27) | 3.67 (3.99) |
2a: 2-(1-(benzyl imino) propyl)4-bromophenol
IR(KBr) : 3028.37(OH),1604.85(C=N),1284.65(C-O) cm-1.1H NMR(DMSO):-δ 1.16(t,3H),2.97(q,2H),4.88(s,2H),6.63-7.79(m,Ar-H),16.86(s,1H,OH)ppmMass:-m/z-317 M+
2b: 2-(1-(benzyl imino) propyl)4-bromo -6-iodo phenol
IR(KBr) : 3078.52(OH),1612.56(C=N),1284.65(C-O) cm-1.1H NMR(DMSO):-δ 1.07(t,3H),3.18(q,2H),3.32(s,2H),6.63-7.79(m,Ar-H),12.97(s,1H,OH)ppmMass:-m/z-443 M+
3a: 4-methyl-2-(1-phenylimino)propyl phenol
IR(KBr) : 3055.38(OH),1597.13(C=N),1203.63(C-O) cm-1.1H NMR(DMSO):-δ 1.16(t,3H),2.23(q,2H), 6.63-7.79(m,Ar-H),14.45(s,1H,OH)ppm Mass:-m/z-239M+
3b: 4-bromo-2-iodo-6-(1-phenylimino) propyl phenol
IR(KBr) : 3045.38(OH),1651.14(C=N),1273.07(C-O) cm-1.1H NMR(DMSO) :-δ 1.17(t,3H),2.50(q,2H),7.35-7.84(m,Ar-H),17.78(s,1H,OH)ppm Mass:-m/z-429 M+
4a: 2-(1-p -tosylimino) propyl)4-methyl phenol
IR(KBr) : 3065.51(OH),1643.42 (C=N),1273.07(C-O) cm-1.1H NMR(DMSO) :-δ1.21(t,3H),2.99(q,2H),2.35(s,6H,Ar-CH3),7.08-7.30(m,Ar-H),16.00(s,1H,OH)ppmMass:-m/z-253M+
4b: 2-(1-p -tosylimino) propyl)4-chloro-6-iodo phenol
IR(KBr) : 3063.09(OH),1651.14(C=N),1265.36(C-O) cm-1.1H NMR(DMSO):-δ 1.16(t,3H),2.02(q,2H),1.01(s,3H),6.67-7.79(m,Ar-H),15.55(s,1H,OH)ppmMass:-m/z-399 M+
5a: 4-bromo-2- (E)-1-(propyl imino) propyl phenol
IR(KBr) : 3070.81(OH),1643.42(C=N),1273.07(C-O) cm-1.1H NMR(DMSO):-δ 1.01(t,3H),1.16(t,3H),2.01 (m,2H),3.89(t,2H),6.45-8.19(m,Ar-H),15.86(s,1H,OH)ppmMass:-m/z-269 M+
5b: 4-chloro-2- (E)-1-(propyl imino) propyl phenol
IR(KBr) : 3068.52(OH),1612.56(C=N),1262.43(C-O) cm-1.1H NMR(DMSO) :-δ 1.01(t,3H),1.11(sex,2H),2.83(t,2H),8.13-8.19(m,Ar-H),17.10(s,1H,OH)ppm Mass:-m/z-225M+
6a: 4-chloro-2-( 1-isopropyl imino) propyl phenol
IR(KBr) : 3075.55(OH),1602.16(C=N),1284.65(C-O) cm-1.1H NMR(DMSO) :-δ1.03(t,3H),1.95(q,2H),3.48(m,1H),6.70-7.48(m,Ar-H),15.45(s,1H,OH)ppmMass:-m/z-225 M+
6b: 4-chloro-2-iodo 6 –(1-(isopropyl imino) propyl phenol
IR(KBr) : 3078.52(OH),1612.56(C=N),1284.65(C-O) cm-1.1H NMR(DMSO) :-δ 1.16(t,3H),2.04(q,2H),3.87 (m ,1H),6.87-7.67(m,Ar-H),16.06(s,1H,OH)ppm Mass:-m/z-350 M+
Conclusion
New Schiff base ligands were synthesized by reacting substituted 2′ hydroxy propiophenone with different aromatic and aliphatic amines. All the ligands showed a strong IR band at 3000-3200 cm-1 for phenolic -OH, a band at 1684-1595 cm-1 for C=N stretch. All the structures were confirmed by NMR and mass spectra. NMR studies showed the presence of OH peak at 12 to 17 ppm in all the ligands.
Acknowledgement
The authors are thankful to Principal, D. S. M. College, Parbhani and Principal, Adarsh College, Hingoli, and the Director, SAIF Punjab University, Chandigarh for providing spectral data.
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