Synthesis and Spectral Characterization of Some New Novel Schiff bases Derived from Hydroxy Propiophenone

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 the ligands were recorded in DMSO solvent using Brucker Avance Neo 500MHz spectrophotometer, FTIR spectra were recorded on Shimadzu spectrometer and the mass spectra was recorded on Q-TOFMicromass (ESI-MS).UV spectra were recorded on 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.

Figure 1: Synthesis of Schiff bases Click here to View figure

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)ppm Mass:-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)ppm Mass:-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) :-δ 1.21(t,3H),2.99(q,2H),2.35(s,6H,Ar-CH₃),7.08-7.30(m,Ar-H),16.00(s,1H,OH)ppm Mass:-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)ppm Mass:-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)ppm Mass:-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-225 M⁺

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) :-δ 1.03(t,3H),1.95(q,2H),3.48(m,1H),6.70-7.48(m,Ar-H),15.45(s,1H,OH)ppm Mass:-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⁺

Figure 2:- IR spectra of 3a Click here to View figure

Figure 3: 1H NMR spectra of 2a. Click here to View figure

Figure 4: UV spectra of 2b Click here to View figure

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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