Molbank 2006, M455

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Synthesis and Physical Characterization of 2-((E)-1-(3-((E)-1-(2-hydroxyphenyl)ethylideneamino)-2-methylphenylimino)ethyl)phenol

A. A. Jarrahpour^a*, A. F. Jalbout^b*, S. Rezaei^a and B. Trzaskowski^b

^aDepartment of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran

^bDepartment of Chemistry, University of Arizona, Tucson, AZ 85721 USA

Phone: +98 711 2284822, Fax: +98 711 2280926, e-mail: [email protected] or [email protected]

*Author to whom correspondence should be addressed

Received: 28 December 2005/ Accepted: 3 January 2006 / Published: 22 January 2006

Abstract: In this paper we propose the synthesis of 2-((E)-1-(3-((E)-1-(2-hydroxyphenyl) ethylideneamino)-2-methylphenylimino) ethyl) phenol. In addition to its synthesis we present AM1 and B3LYP/6-31G* calculations to characterize the physical properties of the molecule.

Keywords: 2-Hydroxyacetophenone, 2-methyl-1,3-phenylenediamine, Schiff base, AM1, B3LYP

Introduction:

Schiff bases are important intermediates for the synthesis of various bioactive compounds [1-2]. Furthermore, they are reported to show a variety of biological activities including antibacterial [3], antifungal [4], anti mouse hepatitis virus (MHV) [5], inhibition of herpes simplex virus type 1 (HSV-1) and adenovirus type 5 (Ad 5 )[6], anti cancer [7], anti mosquito larvae [8] and herbicidal activities [9].The complexes containing the nontoxic 2-hydroxyacetophenone have been used in selective membrane electrodes[10].Choudhuri et al have synthesized a copper complex of 2-hydroxyacetophenone and they have evaluated it as an anticancer agent [11].Some Co(III) complexes of 2-hydroxyacetophenone have been synthesized by John and his coworkers[12].Grunule group have synthesized and characterized four copolymer derived from 2-hydroxyacetophenone.In view of these facts we decided to synthesize a new Schiff base from the nontoxic 2-hydroxyacetophenone as potential biological and complexometric agent. Its biological activities and analytical works are under study.

Results and Discussion:

2-Hydroxyacetophenone 1 (2.03 g, 1.8 mL, 15 mmol) and 2-methyl-1, 3 pheneylenediamine 2 (0.61 g, 5 mmol) were dissolved in 20 ml of warm ethanol. The reaction mixture was refluxed for 8h at 85 °C, and allowed to stand. The solid crystals were filtered off and washed with ethanol. The pure Schiff base 3 was isolated as a light yellow crystalline solid (yield 68%).We next performed theoretical calculations to present a viable structure for the product. All calculations in this work where carried out with the AM1 level of theory using the GAUSSIAN 03 [13] suite of programs. More information about these methods is available elsewhere [14]. Figure 1 presents the optimized structure of the molecule with bond lengths and bond angles shown. We obtained a melting point (mp) value 184-186 °C, and IR (KBr, cm^-1): 3244(OH) (B3LYP/6-31G*: 3217); 1604(C=N) (B3LYP/6-31G*: 1629), as well as NMR.

(A)	(B)
Figure 1. (A). AM1 optimized geometry and (B) B3LYP/6-31G* optimized geometry with all bond lengths shown in angstroms (Å), and bond angles in degrees (º)

Figure 2 shows the theoretical IR vibrational spectrum for this molecule.

(A)	(B)
Figure 2. (A). AM1 IR Spectra theoretical, (B) B3LYP/6-31G* theoretical IR Spectra

Table 1 shows the thermodynamic properties for the complex in figure 1 where T (temperature in K), S (entropy in J mol^-1 K^-1), C_p (heat capacity at constant pressure in kJ mol^-1 K^-1), and ΔH=H° - H°_298.15 (enthalpy content, in kJ mol^-1), T₁=100 K, T₂=298.15 K, and T₃=1000 K calculated AM1 frequencies. The fits were performed according to the equations implemented by the National Institute of Standards and Technology (NIST) [15].

		Fitted Thermodynamic Equation (T/1000=t)	100 K	298.15K	1000 K
AM1	Cp	-32.60241+ 1692.63626*t -907.85165*t^2 + 150.38779*t^3 +0.51679*t^-2	179.04	398.44	904.39
	S	53.732 *ln(t) + 1197.55633 *t + 17.76292 *t^2/2 -370.35669 *t^3/3 - 5533.6327 /(2*t^2) + 153.29627	462.67	755.21	1541.55
	ΔH	465.16043 *t + 6885.20409 *t^2/2 -13920.11871 *t^3/3 + 7543.03025 *t^4/4 – 7.7704 /t -1756.97223	11.50	68.42	560.53
B3LYP/6-31G*	Cp	-72.8544+ 1979.22049*t -1324.98024*t^2 + 333.74311*t^3 +0.56512*t^-2	168.36	412.38	916.56
	S	35.62635*ln(t) + 1302.38545*t + 32.60854*t^2/2 -463.77548*t^3/3 + 2344.59164/(2*t^2) + 159.49792	439.53	731.65	1540.23
	ΔH	-101.60395*t + 6628.71227*t^2/2 -13286.08662*t^3/3 + 7109.30838*t^4/4 + 14.26015/t +702.59222	10.54	67.85	572.53

Table 1. Thermodynamic properties of the molecule in Figure 1, calculated at the AM1 level and B3LYP/6-31G* level of theory, where C_p is the heat capacity in J mol^-1 K^-1, S is the entropy in J mol^-1 K^-1, and DH is the standard enthalpy kJ mol^-1. These where fitted to the Shomate equations [15] which are implemented by the JANAF tables of the NIST databases. These equations converged to an R² value of 0.999 on average.

These equations have been very good at predicting physical properties of various molecules, as we have tested in the past [16-19]. Overall, there is some relative correlation between the AM1 and B3LYP/6-31G* values, however, the density functional theory values should be much more reliable.

Melting Point: 184-186 °C

IR (KBr, cm^-1): 3244(OH); 1604(C=N).

¹H-NMR (250 MHz, CDCl₃): 1.65(6H, s, ArCH₃), 2.26(3H, s, ArCH₃), 6.21(2H, d, Ar), 6.24(2H, d, Ar), 6.88-7.64(5H, m, Ar), 7.94(2H, d, Ar), 14.57(2H, s, OH).

¹³C-NMR (62.9 MHz,CDCl₃): 11.516; 17.133; 30.944; 111.21; 111.71; 113.20; 118.02; 118.22; 119.63; 126.66; 128.88; 132.95; 145.55;145.60; 146.60; 162.15; 171.23.

MS (m/z): 358.47, 225, 132, 106, 77.

Acknowledgment

AFJ and BT would like to thank the University of Arizona supercomputer center for over 200 hours of computer time for these calculations. AAJ and SR thank the Shiraz University Research Council for financial support (Grant No.84-GR-SC-23)

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