Organic Chemistry International

Volume 2012 (2012), Article ID 828032, 8 pages

doi:10.1155/2012/828032

Research Article

Solvent-Free Synthesis of New Coumarins

Redah I. Al-Bayati,¹ Mahdi F. Radey,¹ and Ahmed A. Al-Amiery2,3

¹Chemistry Department, College of Science, Al-Mustansiriyah University, Baghdad 66004, Iraq

²Applied Chemical Division, Department of Applied Science, University of Technology, Baghdad 10066, Iraq

³Department of Chemical and Processing Engineering, Faculty of Engineering and Built Environment, University of Kebangsaan Malaysia, Selangor, Bangi 43600, Malaysia

Received 26 March 2012; Accepted 4 June 2012

Academic Editor: Robert Salomon

Copyright © 2012 Redah I. Al-Bayati et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

A solvent-free synthesis of five series of coumarin derivatives using microwave assistant is presented herein. The synthesized compounds are fully characterized by UV-VIS, FT-IR, and NMR spectroscopy.

1. Introduction

Coumarin (2H-Lbenzopyran-2-one) and its derivatives possess a wide range of various biological and pharmaceutical activities. They have a wide range of applications as antitumor [1, 2], anti-HIV [3, 4], anticoagulant [5, 6], antimicrobial [7, 8], antioxidant [9, 10], and anti-inflammatory [11, 12] agents. The antitumor activities of coumarin compounds have been extensively examined [13–16]. Although most of the existing natural coumarins have been isolated from higher plants, some of them have been discovered in microorganisms, for example, aminocoumarin antibiotics: novobiocin, coumermycin A1, and chlorobiocin (produced by the actinomycete Streptomyces niveus) [17]. Synthetic coumarin derivatives have been obtained by chemical modification of the coumarin ring. Recently, density functional theory (DFT) has been accepted by the quantum chemistry community as a cost-effective approach for the computation of molecular structure, vibration frequencies, and energies of chemical reactions. Many studies have shown that the molecular structures and vibration frequencies calculated by DFT methods are more reliable than MP2 methods [18–26]. While there is sufficient evidence that DFT provides accurate description of the electronic and structural properties of solids, interfaces, and small molecules, relatively little is known about the symmetric performance of DFT applications to their molecular associates.

Structure activity relationships of coumarin derivatives have revealed that the presence of substituted amino derivatives is an essential feature of their pharmacological action. Based on these findings, we try to describe the synthesis of some compounds featuring different heterocyclic rings fused onto the coumarin moiety with the aim of obtaining more potent pharmacologically active compounds.

2. Experimental

2.1. General

The chemicals used for the synthesis were supplied by Sigma-Aldrich. Purity of the compounds was checked on thin layer chromatography (TLC) plates (Silica Gel G) using the solvent systems benzene-ethyl acetate-methanol (40 : 30 : 30, v/v/v) and toluene-acetone (75 : 25, v/v). The spots were located under UV light (254 and 365 nm). Melting points were determined on GallenKamp (MFB-600) melting point apparatus and were uncorrected. The IR spectra of the compounds were recorded on a shimadzu FT-IR-8300 spectrometer as KBr disk. The UV-VIS spectra were performed on Cintra-5-Gbes scientific equipment. The ¹H-NMR and ¹³C-NMR spectra (solvent DMSO-d6) were recorded on Bruker 400 MHz spectrophotometer using TMS as internal standard.

2.2. Synthesis of 1-aminoquinolin-2(1H)-one (1)

1-aminoquinolin-2(1H)-one (1) was synthesized according to [27], and the structure of the compound was confirmed with elemental analyses and spectral analyses (IR, UV-VIS, ¹H-NMR, and ¹³C-NMR).

2.3. Synthesis of (E)-1-((2-hydroxybenzylidene)amino)quinolin-2(1H)-one (2) and (E)-1-((1-(thiophen-2-yl)ethylidene)amino)quinolin-2(1H)-one (3)

N-aminocoumarin (0.16 g, 0.001 mol) and 2-hydroxybenzaldehyde (or 1-(thiophen-2-yl)ethanone) (0.001 mol) were placed together in an open small test tube; after 6 minutes, the product was separated out and recrystallized.

2.4. Synthesis of 1,1′-((1Z,1′Z)-(1,4-phenylenebis(methanylylidene))bis(azanylylidene))bis(quinolin-2(1H)-one) (4)

N-aminocoumarin (0.32 g, 0.002 mol) and terephthaldehyde (0.134 g, 0.001 mol) were placed together in an open small test tube; after 8 minutes, the product was separated out and recrystallized.

2.5. Synthesis of 2-(2-oxoquinolin-1(2H)-yl)isoindoline-1,3-dione (5) and 3-methylene-1-(2-oxoquinolin-1(2H)-yl)pyrrolidine-2,5-dione (6)

N-aminocoumarin (0.16 g, 0.001 mol) and phthalic anhydride (or itaconic anhydride) (0.001 mol) were placed together in an open small test tube; after 5 minutes, the product was separated out and recrystallized.

2.6. Synthesis of 1-(naphthalen-1-yl)-3-(2-oxoquinolin-1(2H)-yl)urea (7)

N-aminocoumarin (0.16 g, 0.001 mol) and 1-naphthylisocyanate (0.17 g, 0.001 mol) were placed together in an open small test tube; after 8 minutes, the product was separated out and recrystallized.

2.7. Synthesis of 1,1′-(hexane-1,6-diyl)bis(3-(2-oxoquinolin-1(2H)-yl)urea) (8) and 1,1′-(2-methyl-1,4-phenylene)bis(3-(2-oxoquinolin-1(2H)-yl)urea) (9)

N-aminocoumarin (0.32 g, 0.002 mol) and hexamethylene diisocyanate (or toluene-2,5-diisocyanate) (0.001 mol) were placed together in an open small test tube; after 8 minutes, the product was separated out and recrystallized.

2.8. Synthesis of 2-((2-oxoquinolin-1(2H)-yl)amino)thiazol-5(4H)-one (10), 2-(carboxy(2-oxoquinolin-1(2H)-yl)amino)acetic acid (11) and 1-(pyridin-2-ylamino)quinolin-2(1H)-one

N-aminocoumarin (0.16 g, 0.001 mol) and rhodanine (or 2-mercaptopyridine or 2-mercaptosuccinic acid) (0.001 mol) were placed together in an open small test tube; after 8 minutes, the product was separated out and recrystallized.

2.9. Synthesis of 3H–[1,2,4,5]tetrazino[1,6-a]quinolin-2-amine (13)

N-aminocoumarin (0.16 g, 0.001 mol) and thiosemicarbazide (0.1 g, 0.001 mol) were placed together in an open small test tube; after 10 minutes, the product was separated out and recrystallized.

2.10. The Calculation Method

Gaussian 03, Revision C.01 [28] was used for the calculation of ground-state geometry which was optimized to a local minimum without any symmetry restrictions using basis set 3-21G [29, 30]. The Becke three-parameter hybrid (B3) [31, 32] exchange functional in combination with the Lee-Yang-Parr (LYP) [33] correction functional (B3LYP) was used for all geometry optimizations, thermodynamic functions at conditions (temperature = 298.150 Kelvin and pressure = 1.0 Atm), high occupied molecular orbital (HOMO), and low unoccupied molecular orbital (LUMO) distribution, and some physical properties for compound 3.

3. Results and Discussion

3.1. Chemistry

For the synthesis of new coumarin derivatives, the reaction sequences outlined in Schemes 1, 2, 3, 4, 5, 6, 7, and 8 were followed. We started from coumarin (1) which is commercially available or, alternatively, readily accessible through a Pechmann and Perkin condensation [25]. Recrystallization solvent was chloroform. Yield 91%; M.P. 131–133°C. The structure of compound (1) was confirmed from its spectral data. UV-VIS in methanol, nm: 280 (0.93) and 227 (1.8). The IR spectrum showed two strong absorption bands at 3290 to 3300 cm⁻¹ and strong band at 1645 cm⁻¹, corresponding to –NH₂ and –C=O, respectively; 1595 (C=C aromatic), 3045 (C–H aromatic), 1242 (C–N). ¹H-NMR: 4.1 (s, 2H, –NH₂), 6.7 (t, Ar–H), 7.4 (d, Ar–H) and 7.1 (d, Ar–H). ¹³C-NMR: 126, 127, 127.8, 128, 123.3, 128.5, 129, 155 and 157.

Scheme 1

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Scheme 6

Scheme 7

Scheme 8

3.1.1. Compound (2)

Yellow solid; Yield 92; mp 86–88°C; IR (KBr) (/cm⁻¹): 3076, 2945, 2920, 1681, 1653, 1583, 1520. ¹H NMR (300 MHz, CDCl₃): (ppm) 2.3 (s, 3H, –CH₃), 7.1–7.9 (9H, Ar–H); ¹³C NMR (125 MHz, CDCl₃): (ppm) 15, 23, 126, 128, 128.2, 129, 129.8, 130, 131, 133, 135, 143, 144, 157.

3.1.2. Compound (3)

Yellow solid; Yield 88; mp 215–217°C; IR (KBr) (/cm⁻¹): 3200, 3046, 1681, 1621, 1573, 1487. ¹H NMR (300 MHz, CDCl₃): (ppm) 3.3 (s, 1H, –OH), 9.0 (s, 1H, N=CH), 6.6–7.7; ¹³C NMR (125 MHz, CDCl₃): (ppm) 17.6, 118.7, 125.0, 125.5, 125.9, 127.4, 128.2, 136.5, 137.1, 139.0, 161.3, 164.6.

3.1.3. Compound (4)

Yellow solid; Yield 78; mp 230–232°C; IR (KBr) (/cm⁻¹): 3070, 1670, 1604, 1595, 1456. ¹H NMR (300 MHz, CDCl₃): (ppm) 6.1 (dd, 1H, =CH), 7.1–7.6 (m, 1H, Ar–H), 7.9–8.2 (m, 1H, Ar–H); ¹³C NMR (125 MHz, CDCl₃): (ppm) 117.5, 126.0, 126.6, 128.3, 128.7, 131.2, 131.4, 131.9, 133.0, 137.5, 141.9, 159.3.

3.1.4. Compound (5)

White solid; Yield 90; mp 340 dec.°C; IR (KBr) (/cm⁻¹): 3016, 1661, 1601, 1557 ¹H NMR (300 MHz, CDCl₃): (ppm) 3.1 (s, 2H, –CH₂), 5.9 (s, 1H, =CH), 6.3 and 6.5 (dd, 1H, =CH), 6.9–7.3 (1H, s, C–H, Aromatic); ¹³C NMR (125 MHz, CDCl₃): (ppm) 17 39.7, 99.6, 117, 122.7, 127.3, 127.6, 127.9, 129.2, 130.9, 140.8, 155.6, 155.9, 169.3.

3.1.5. Compound (6)

Yellow solid; Yield 89; mp 94–96°C; IR (KBr) (/cm⁻¹): 3001, 2925, 1681, 1604, 1562. ¹H NMR (300 MHz, CDCl₃): (ppm) 6.6 (dd, 1H, =CH), 6.8 (dd, 1H, =CH), 7.3–7.6 (1H, Ar–H); ¹³C NMR (125 MHz, CDCl₃): (ppm) 110.8, 118.6, 119.3, 121.8, 124, 136, 138.6, 156.2, 156.9.

3.1.6. Compound (7)

White solid; Yield 87; mp 216–218°C; IR (KBr) (/cm⁻¹): 3271 (N–H), 3049 (C–H Aromatic), 1660 and 1654 (C=O), 1608 and 1552 (C=C Aromatic). ¹H NMR (300 MHz, CDCl₃): (ppm) 5.9 (s, 1H, –CH), 6.2 (dd, 1H, =CH), 6.9–7.5 (m, –C–H Aromatic); 7.6 (dd, –C–H Aromatic); ¹³C NMR (125 MHz, CDCl₃): (ppm) 111.3, 112.2, 122.1, 122.3, 122.5, 122.6, 122.9, 127.1, 129, 129.7, 139.2, 140.1, 144.2, 144.6, 153.9, 154.2, 163.6.

3.1.7. Compound (8)

White solid; Yield 91; mp 248–250°C; IR (KBr) (/cm⁻¹): 3300 (N–H), 3095 (C–H Aromatic), 2931, 2858 (C–H ali), 1664 (C=O), 1556, 1458 (C=C Aromatic). ¹H NMR (300 MHz, CDCl₃): (ppm) 1.3 (t, 2H. CH₂CH₂.), 6.3 (s, 1H, –NHCO), 3.3 (s, 2H, NHCH₂), 6.9–7.5 (6H, Ar–H); ¹³C NMR (125 MHz, CDCl₃): (ppm) 111.8, 114.0, 114.3, 117.5, 119.0, 121.1, 121.2, 121.6, 121.9, 124.1, 124.6, 128.2, 130.3, 131.2, 143.1, 144.2, 144.7, 144.9, 152.9, 161.0.

3.1.8. Compound (9)

White solid; Yield 88; mp 210–212°C; IR (KBr) (/cm⁻¹): 3307 (N–H), 3020 (C–H Aromatic), 2926 and 2850 (C–H ali.), 1670 and 1658 (C=O), 1633 and 1602 (C=C arom). ¹H NMR (300 MHz, CDCl₃): (ppm) 2.3 (m, 2H, –CH₂), 3.1 (m, 2H, –CH₂), 6.9–7.2 (m, 1H, Ar–H); 7.3–7.5(1H, Ar–H); ¹³C NMR (125 MHz, CDCl₃): (ppm) 28.2, 31.9, 37.0, 117.6, 122.4, 122.8, 124.1, 124.4, 125.2, 141.3, 143.0, 158.6.

3.1.9. Compound (10)

Yellow Yield 93; oily; IR (KBr) (/cm⁻¹): 3182 (N–H), 3072 (C–H Aromatic), 1668 (C=O), 1598 and 1456 (C=C arom), 1573 (C=N). ¹H NMR (300 MHz, CDCl₃): (ppm) 3.6 (s, 2H, –CH₂), 5.8 (d, 1H, =C–H), 6.4 (d, 1H, =C–H), 7.0–7.3 (1H, Ar–H); ¹³C NMR (125 MHz, CDCl₃): (ppm) 41.0, 111.6, 119.1, 122.3, 122.6, 122.9, 125.3, 146.8, 151.1, 152.9, 156.1.

3.1.10. Compound (11)

Yellow solid; Yield 90; mp 102–104°C; IR (KBr) (/cm⁻¹): 3182, 3070, 1708, 1570. ¹H NMR (300 MHz, CDCl₃): (ppm) 3.8 (s, 2H, CH₂), 5.9 (dd, 1H, =C–H), 6.6 (d, 1H, =C–H), 6.9–7.2 (1H, Ar–H); ¹³C NMR (125 MHz, CDCl₃): (ppm) 42.7, 117.4, 120.1, 121.9, 122.1, 122.4, 122.8, 15.3, 127.8, 151.4, 158.5, 161.4, 168.8.

3.1.11. Compound (12)

Yellow oily; Yield 90; IR (KBr) (/cm⁻¹): 3217 (N–H), 3180–2563 (OH), 2945, 2920, 1714, 1651, 1568, 1462. ¹H NMR (300 MHz, CDCl₃): (ppm) 5.2 (s, 1H, –NH), 6.1 (d, 1H, =C–H), 6.4 (d, 1H, =C–H),7.0–7.2 (m, 1H, Ar–H), 7.3–7.5 (m, 1H, Ar–H); ¹³C NMR (125 MHz, CDCl₃): (ppm) 117.9, 118.4, 120.4, 121.1, 121.4, 122.5, 137.9, 145.0, 152.1, 155.9, 171.0, 171.7.

3.1.12. Compound (13)

Yellow solid; Yield 87; solid; mp 92–94°C; IR (KBr) (/cm⁻¹): 3254 and 3147 (N–H), 3003, 2676, 1622, 1577, 1556. ¹H NMR (300 MHz, CDCl₃): (ppm) 5.9 (1H, s, =C–H), 6.4 (1H, s, =C–H), 6.9 (1H, dd, –C–H aromatic), 7.3 (1H, dd, –C–H aromatic); ¹³C NMR (125 MHz, CDCl₃): (ppm) 113.1, 117.0, 122.4, 127.6, 127.9, 133.1, 136.1, 140.5, 140.8, 157.2.

3.2. Computational Studies

3.2.1. Atomic Charges (Mulliken Charges)

An earlier study [34] has shown that atomic charges were affected by the presence of the substituent of rings. For compound 3 the 3D geometrical structure is given in Figure 1. The data obtained show that highest atomic charge in compound 3 is at [N(7) −0.744890] followed by the next charge value at [O(11) −0. 0. 500312]. These data show clearly that these atoms are the most reactive toward the addition, substitution reactions, and bonding with the metal. The determined bond angle and twist angle, stretch (1. 9443), bend (7. 6317), stretch-bend (0. 0909), and the 3D geometrical structure indicate that this molecule is a nonplanar molecular and the stereochemistry is [C(9): C(10): (Z); N(12)-C(13): (Z)].

Figure 1: Optimized 3D geometrical structure for compound 3.

3.2.2. Density Function Theory (DFT)

DFT calculations were performed for compound 3. Optimized molecular structure of the most stable form is shown in Figure 1, Table 1; the calculated energies and relative energies are presented in Table 1. Molecular orbital calculations provide a detailed description of orbitals including spatial characteristics, nodal patterns, and individual atom contributions. The contour plots of the frontier orbitals for the ground state of compound 3 are shown in Figures 2 and 3, including the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). It is interesting to see that both orbitals are substantially distributed over the conjugation plane. It can be seen from Figure 2 that the HOMO orbitals are located on the substituted molecule while LUMO orbitals resemble those obtained for the unsubstituted molecule, and therefore the substitution has an influence on the electron donation ability, but only a small impact on electron acceptance ability [35]. The orbital energy levels of HOMO and LUMO of compound 3 are listed in Table 2. It can be seen that the energy gaps between HOMO and LUMO are about −5.419 eV. The lower value in the HOMO and LUMO energy gap explains the eventual charge transfer interaction taking place within the molecules. The dipole moments of compounds 3 were also calculated and listed in Table 3.

Table 1: Total energy, relative energies and heat of formation for 3.

Compound
Potential energy
Total energy
Kinetic energy

3
−1445030.1135 Kcal/Mol
−724778.6338 Kcal/Mol
720251.4797 Kcal/Mol

Table 2: HOMO and LUMO energies of 3.

Compound
HOMO
LUMO

3
−8.992 eV
−3.573 eV
−4.390

Table 3: The dipole moments (Debye) of 3.

Compound
x-component
y-component
z-component
Magnitude

3
−0.984845
3.875375
−1.511631
4.274749

Figure 2: The highest occupied molecular orbital (HOMO) of compound 3.

Figure 3: The lowest unoccupied molecular orbital (LUMO) of compound 3.

4. Conclusions

In this study, the new coumarins have been successively synthesized and characterized by using various spectroscopic methods. The synthesized compound 3 was studied theoretically, and the atomic charges, heat of formation, and stereochemistry were estimated, and it was found that compound 3 is not planar.

References

H. Madari, D. Panda, L. Wilson, and R. S. Jacobs, “Dicoumarol: a unique microtubule stabilizing natural product that is synergistic with Taxol,” Cancer Research, vol. 63, no. 6, pp. 1214–1220, 2003.

I. Kostova, “Synthetic and natural coumarins as cytotoxic agents,” Current Medicinal Chemistry, vol. 5, no. 1, pp. 29–46, 2005.

Y. Takeuchi, L. Xie, L. M. Cosentino, and K. H. Lee, “Anti-AIDS agents-XXVIII.¹ Synthesis and Anti-HIV activity of methoxy substituted 3′,4′-Di-O-(−)-camphanoyl-(+)-cis-khellactone (DCK) analogues,” Bioorganic & Medicinal Chemistry Letters, vol. 7, no. 20, pp. 2573–2578, 1997.

Y. Shikishima, Y. Takaishi, G. Honda et al., “Chemical constituents of Prangos tschimganica; structure elucidation and absolute configuration of coumarin and furanocoumarin derivatives with anti-HIV activity,” Chemical and Pharmaceutical Bulletin, vol. 49, no. 7, pp. 877–880, 2001.

I. Manolov, C. Maichle-Moessmer, and N. Danchev, “Synthesis, structure, toxicological andpharmacological investigations of4-hydroxycoumarin derivatives,” European Journal of Medicinal Chemistry, vol. 41, no. 7, pp. 882–890, 2006.

J. C. Jung, J. C. Kim, and O. S. Park, “Simple and cost effective syntheses of 4-hydroxycoumarin,” Synthetic Communications, vol. 29, no. 20, pp. 3587–3595, 1999.

D. A. Ostrov, J. A. Hernández Prada, P. E. Corsino, K. A. Finton, N. Le, and T. C. Rowe, “Discovery of novel DNA gyrase inhibitors by high-throughput virtual screening,” Antimicrobial Agents and Chemotherapy, vol. 51, no. 10, pp. 3688–3698, 2007.

A. A. Al-Amiery, A. Kadhum, and A. Mohamad, “Antifungal activities of new coumarins,” Molecules, vol. 17, no. 5, pp. 5713–5723, 2012.

L. Koshy, B. S. Dwarakanath, H. G. Raj, R. Chandra, and T. Lazar Mathew, “Suicidal oxidative stress induced by certain antioxidants,” Indian Journal of Experimental Biology, vol. 41, no. 11, pp. 1273–1278, 2003.

K. C. Fylaktakidou, D. J. Hadjipavlou-Litina, K. E. Litinas, and D. N. Nicolaides, “Natural and synthetic coumarin derivatives with anti-inflammatory/antioxidant activities,” Current Pharmaceutical Design, vol. 10, no. 30, pp. 3813–3833, 2004.

M. Ghate, D. Manohar, V. Kulkarni, R. Shobha, and S. Y. Kattimani, “Synthesis of vanillin ethers from 4-(bromomethyl) coumarins as anti-inflammatory agents,” European Journal of Medicinal Chemistry, vol. 38, no. 3, pp. 297–302, 2003.

C. A. Kontogiorgis and D. J. Hadjipavlou-Litina, “Synthesis and antiinflammatory activity of coumarin derivatives,” Journal of Medicinal Chemistry, vol. 48, no. 20, pp. 6400–6408, 2005.

M. Baba, Y. Jin, A. Mizuno et al., “Studies on cancer chemoprevention by traditional folk medicines XXIV. Inhibitory effect of a coumarin derivative, 7-isopentenyloxycoumarin, against tumor-promotion,” Biological and Pharmaceutical Bulletin, vol. 25, no. 2, pp. 244–246, 2002.

D. Thornes, L. Daly, G. Lynch et al., “Prevention of early recurrence of high risk malignant melanoma by coumarin,” European Journal of Surgical Oncology, vol. 15, no. 5, pp. 431–435, 1989.

A. A. Al-Amiery, R. Al-Bayati, K. Saour, and M. Radi, “Cytotoxicity, antioxidant, and antimicrobial activities of novel 2-quinolone derivatives derived from coumarin,” Research on Chemical Intermediates, vol. 38, pp. 559–569, 2012.

A. Kadhum, A. Mohamad, A. A. Al-Amiery, and M. Takriff, “Antimicrobial and antioxidant activities of new metal complexes derived from 3-Aminocoumarin,” Molecules, vol. 16, pp. 6969–6984, 2011.

D. Završnik, S. Muratović, D. Makuc et al., “Benzylidene-bis-(4-hydroxycoumarin) and benzopyrano-coumarin derivatives: synthesis, 1H/13C-NMR conformational and X-ray crystal structure studies and in vitro antiviral activity evaluations,” Molecules, vol. 16, no. 7, pp. 6023–6040, 2011.

S. Ali Beyramabadi and A. Morsali, “Intramolecular proton transfer of 2-[(2,4- dimethylphenyl)iminomethyl]-3,5-dimethoxyphenol schiff-base ligand: a density functional theory (DFT) study,” International Journal of Physical Sciences, vol. 6, no. 7, pp. 1780–1788, 2011.

M. Monajjemi, M. Sayadian, K. Zare, A. Ilkhani, and F. Mollaamin, “Computational study of hydrogen bonding on calix[8]arene as nanostructure compound,” International Journal of Physical Sciences, vol. 6, no. 16, pp. 4063–4066, 2011.

A. Kadhum, A. A. Al-Amiery, M. Shikara, and A. Mohamad, “Synthesis, structure elucidation and DFT studies of new thiadiazoles,” International Journal of the Physical Sciences, vol. 6, no. 29, pp. 6692–6697, 2011.

A. A. Al-Amiery, A. Musa, A. Kadhum, and A. Mohamad, “The use of umbelliferone in the synthesis of new heterocyclic compounds,” Molecules, vol. 16, pp. 6833–6843, 2011.

A. A. Al-Amiery, Y. K. Al-Majedy, H. Abdulreazak, and H. Abood, “Synthesis, characterization, theoretical crystal structure, and antibacterial activities of some transition metal complexes of the thiosemicarbazone (Z)-2-(pyrrolidin-2-ylidene) hydrazinecarbothioamide,” vol. 2011, Article ID 483101, 6 pages, 2011.

A. Kadhum, B. Wasmi, A. Mohamad, A. Al-Amiery, and M. Takriff, “Preparation, characterization, and theoretical studies of azelaic acid derived from oleic acid by use of a novel ozonolysis method,” Research on Chemical Intermediates, vol. 38, pp. 659–668, 2011.

A. H. Kadhum, A. A. Al-Amiery, A. Y. Musa, and A. Mohamad, “The antioxidant activity of new coumarin derivatives,” International Journal of Molecular Sciences, vol. 12, pp. 5747–5576, 2011.

A. A. Al-Amiery, A. Kadhum, and A. Mohamad, “Antifungal and antioxidant activities of pyrrolidone thiosemicarbazone complexes,” Bioinorganic Chemistry and Applications, vol. 2012, Article ID 795812, 6 pages, 2012.

A. A. Al-Amiery, Y. K. Al-Majedy, H. Ibrahim, and A. A. Al-Tamimi, “Antioxidant, antimicrobial,and theoretical studies of the thiosemicarbazone derivative Schiff base 2-(2-imino-1-methylimidazolidin-4-ylidene)hydrazinecarbothioamide (IMHC),” Organic and Medicinal Chemistry Letters, vol. 2, no. 4, 2012.

R. I. H. Al-Bayati and M. F. Radi, “Synthesis of novel 2-quinolone derivatives,” African Journal of Pure and Applied Chemistry, vol. 4, no. 10, pp. 228–232, 2011.

J. A. Pople, et al., Gaussian, Inc., Wallingford CT, 2004 Gaussian 03W (Revision C.01), Gaussian, Inc., Wallingford CT, 2003

W. J. Pietro, M. M. Francl, W. J. Hehre, D. J. Defrees, J. A. Pople, and J. S. Binkley, “Self-consistent molecular orbital methods. 24. Supplemented small split-valence basis sets for second-row elements,” Journal of the American Chemical Society, vol. 104, no. 19, pp. 5039–5048, 1982.

K. D. Dobbs and W. J. Hehre, “Molecular orbital theory of the properties of inorganic and organometallic compounds 5. Extended basis sets for first-row transition metals,” Journal of Computational Chemistry, vol. 8, pp. 861–879, 1987.

A. D. Becke, “Density-functional exchange-energy approximation with correct asymptotic behavior,” Physical Review Letters A, vol. 38, pp. 3098–3100, 1988.

A. D. Becke, “Density-functional thermochemistry. III. The role of exact exchange,” The Journal of Chemical Physics, vol. 98, no. 7, pp. 5648–5652, 1993.

C. Lee, W. Yang, and R. G. Parr, “Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density,” Review Letters B, vol. 37, no. 2, pp. 785–789, 1988.

A. A. Al-Amiery, “Synthesis and antioxidant, antimicrobial evaluation, DFT studies of novel metal complexes derivate from Schiff base,” Research on Chemical Intermediates, vol. 38, pp. 745–752, 2012.

A. Musa, A. Mohamad, A. A. Al-Amiery, A. Kadhum, and L. Tien, “Galvanic corrosion of aluminum alloy (Al2024) and copper in 1.0 M hydrochloric acid solution,” International Journal of Electrochemical Science, vol. 6, pp. 5052–5065, 2011.