Synthesis, spectral, optical and anti-inflammatory activity of complexes derived from 2-aminobenzohydrazide with some rare earths

JOURNAL OF RARE EARTHS, Vol. 33, No. 7, July 2015, P. 758

Synthesis, spectral, optical and anti-inflammatory activity of complexes derived from 2-aminobenzohydrazide with some rare earths Nasser Mohammed Hosny1,*, El Sayed A. El Morsy2,3, Yousery E. Sherif2,4 (1. Chemistry Department, Faculty of Science, Port-Said University, 23 December Street, Port-Said, Egypt; 2. Clinical Pharmacology Department, Faculty of Medicine, Mansoura University, Mansoura, Egypt; 3. Pharmacology and Therapeutics Department, Qassim College of Medicine, Qassim University, Qassim, KSA; 4. Department of Chemistry, Faculty of Science and Arts, Taibah University, Ulla, KSA) Received 11 February 2014; revised 13 April 2015

Abstract: Three new metal complexes derived from Er(III), Dy(III) and Zr(IV) with 2-aminobenzohydrazide (ABH) were synthesized and characterized by elemental analyses, IR, 1H-NMR, ES-MS and transmission electron microscopy (TEM). The morphology and the particle size were determined by TEM. The results showed that the ligand acted as neutral bi-dentate coordinating to the metal ions through the carbonyl oxygen and amidic amino nitrogen. The aromatic amine group remained inert towards coordination. The optical band gap was measured and found to be 3.3, 3.5 and 4.3 eV for Er(III), Dy(III) and Zr(IV), respectively. The optical band gap values indicated a semi-conducting nature of the investigated complexes. The anti-inflammatory and analgesic activities of the tested compounds were determined and compared with standard meloxicam. Keywords: Er(III); Dy(III); Zr(IV); metal complexes; optical band gap; rare earths

Metal complexes of rare earth metals have attracted much more attention because of their wide applications as anti-tumor, anti-bacterial and anti-fungal agents[1–3]. Also, they are used as catalyst in organic synthesis[4] and as optical materials[5]. Hydrazides have increasing applications in medicine, analytical chemistry, syntheses of novel heterogeneous catalysts of oxido-reduction processes, molecular semiconductors, as well as in numerous fields of science and technology[6]. Derivatives of anthranilic acid are used as non-steroidal anti-inflammatory drugs (NSAIDs), prescribed for different types of arthritis[7–9]. The hydrazide moiety not only has anti-inflammatory activity[10], but also has anti-tuberculosis, anti-tumor, anti-hypertensive and peripheral vasodilator action[11–14]. The remarkable biological activity of acid hydrazides comes from their ability to bind with the transition metal ions present in the living system[15,16]. No work has been carried out on the metal complexes of 2-aminobenzohydrazide with lanthanides or zirconium. In this work, we synthesized three new metal complexes of Er(III), Dy(III) and Zr(IV) with 2-aminobenzohydrazide (ABH). The isolated complexes were characterized by different physicochemical techniques. The optical band gaps of the isolated complexes were determined and indicated semi-conducting properties of the isolated complexes. The analgesic and anti-inflammatory activities of the organic ligand and its metal complexes were studied and compared with meloxicam.

1 Experimental All chemicals were of analytical grade and were used without further purification. Molar conductance measurements of the complexes (10−3 mol/L) in DMSO were carried out with a conductivity bridge YSI model 32. Infrared spectra were measured using KBr discs on a Mattson 5000 FTIR spectrometer. Electronic spectra were recorded on a UV2 Unicam UV/vis spectrometer using silica cells. Thermal analysis measurements (TGA) were carried out on a Shimadzu model 50 H instrument. The nitrogen flow rate and heating rate were 20 cm3/min and 10 ºC/min, respectively. 1H-NMR spectra were obtained on a JEOL spectrophotometer at 500 MHz, using TMS as an internal reference and DMSO-d6 as solvent. TEM images of the products were obtained by a CM20PHILIPS electron microscope. 1.1 Synthesis of metal complexes The following general procedures were followed in the preparation of the metal complexes: 0.01 mol of DyCl3·6H2O, Er(NO3)3·5H2O or ZrCl4 was added to 0.01 mol of 2-aminobenzohydrazide in 25 mL ethanol. The reaction was refluxed for 4 h in case of Dy(III) and Er(III), while ZrCl4 was injected and the reaction mixture was refluxed under nitrogen for 6 h. A brown precipitate was isolated in case of Er(III) and Dy(III), while yellow precipitate was formed in case of Zr(IV). The precipitate was filtered under vacuum then, washed with ethanol and

* Corresponding author: Nasser Mohammed Hosny (E-mail: [email protected]; Tel.: +201208949300) DOI: 10.1016/S1002-0721(14)60482-8

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signed to ν M–N and ν M–O, respectively[20]. From the above findings, it could be concluded that, the ligand (ABH) binds to the metal ions in a neutral bi-dentate manner, through amidic nitrogen and carbonyl oxygen (Figs. 2–4). In case of Zr(IV) complex the ligand may exist either in N–N cis, O–O cis or N–N trans, O–O trans. Since Zr(IV) complex gives negative test with biacetyl, it is suggested that the ligand coordinates in the trans form[11].

kept under vacuum. Anal. Calc. for [Zr(ABH)2(OC2H5)2]Cl2·5/2C2H5OH: C, 41.3; H, 6.4; N, 12.5; Zr, 13.6. Found: C, 41.8; H, 5.6; N, 13.0; Zr, 14.50%. Anal. Calc. for [Er(ABH)(NO3)3H2O]H2O: C, 15.5; H, 2.4; N, 15.5. Found: C, 15.7; H, 3.0; N, 16.0% and Anal. Calc. for [Dy(ABH)OHCl2H2O]1/2H2O.1/ 2EtOH: C, 21.2; H, 3.3; N, 9.2; Cl, 15.7. Found: C, 21.60; H, 3.3; N, 8.5; Cl, 16.2%. 1.2 Pharmacological studies More details about the pharmacological and quantitative structure activity relationship (QSAR) studies are presented in literature[17].

2.2

1

H-NMR spectrum

The 1H-NMR spectrum of Zr(IV) complex in DMSOd6 shows singlet signal in the downfield region at 8.5 ppm, corresponding to the protons of the amidic –NH2. The shift of this signal to downfield regions compared with its position in the free ligands (7.21 ppm) indicates that this group coordinates to the metal ion. Another singlet signal has been observed at 10.5 ppm assigned to –NH of the amidic group (CO–NH–). The presence of this signal in the spectra of the complex confirms the coordination of the ligand in the keto form. The spectrum of Zr complex also shows singlet signal at 6.3 ppm assigned to NH2 of the ring, it remains in its position as the free ligand, confirming the inertness of NH2 of the ring towards coordination[11]. The broadening of this signal was attributed to the presence of hydrogen bond between NH2 and CO groups. The aromatic protons appear as multiplet in the region of 6.48–7.42 ppm.

2 Results and discussion All the isolated complexes are colored, Zr(IV) complex is yellow and stable in air, while Er(III) and Dy(III) complexes are yellowish brown and hygroscopic. All the complexes are soluble in DMF and DMSO. The molar conductivity values of 1×10–3 mol in DMF at 25 ºC are 75 Ω–1cm2mol–1 for Zr(IV) complex and 4.0–9.0 Ω–1cm2mol–1 for Er(III) complex and Dy(III) complex, respectively. These values suggest 1:2 electrolytic nature of Zr(IV) complex and non-electrolytic nature of both Er(III) and Dy(III) complexes[18]. 2.1 IR spectra of ABH and its metal complexes The most important IR bands of the ligand and its complexes are collected in Table 1. The ligand ABH shows several bands at 3346, 3326 and 3028 cm–1 assigned to ν NH2 of the amide and the ring. The ligand also shows band at 1680 assigned to ν C=O[19]. This band has been shifted to the range of 1660–1666 cm–1 in the spectra of the complexes (Fig. 1), indicating the participation of this group in bonding. The bands assigned to NH2 of the ring remain approximately in its position in the spectra of the complexes, indicating the inertness of this group towards coordination. The spectrum of Dy(III) complex shows a new band at 1033 cm–1 assigned to δ OH (free). The band at 1663 cm–1 assigned to ν CONH in the spectrum of the free ligand is shifted to the region of 1627–1650 cm–1 in the spectra of the complexes due to the coordination of the carbonyl oxygen. The presence of this band confirms that the ligand chelates the metal ions in the keto form. Several new bands are observed in the spectra of the three complexes in the range of 439–451 and 514–545 cm–1 as-

2.3 ES-MS of Er(III), Dy(III) and Zr(IV) complexes Mass spectrum of Er(III) complex shows the exact mass at m/z=541. Two possible pathways in fragmenta-

Fig. 1 IR spectrum of Zr(IV) complex

Table 1 IR bands (cm–1) of the ligand (ABH) and its complexes Compound

ν(NH2)

ν(C=O)

ν(CONH)

ν(M–O)

(ABH)

3444, 3346, 3326, 3028

1680

1663

–

ν(M–N) –

[Er(ABH)(NO3)3H2O]H2O

3443, 3345, 3317, 3272

1660

1650

514

477

[DyC7H11N3Cl2OH]1/2H2O·1/2EtOH

3440, 3350, 3305, 3282

1663

1651

527

451

[Zr(ABH)2 (OC2H5)2]Cl2·5/2C2H5OH

3379, 3203

1666

1627

558

439

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JOURNAL OF RARE EARTHS, Vol. 33, No. 7, July 2015

Fig. 2 Suggested structure for Er(III) complex

Fig. 4 Suggested structure for Zr(IV) complex

2.4 Thermal analyses

Fig. 3 Suggested structure for Dy(III) complex

tion pattern of Er(III) complex are indicated in Scheme 1. Mass spectrum of Dy(III) complex shows the exact mass peak at m/z=451. The fragmentation pattern of this complex is indicated in Scheme 2. The mass spectrum of Zr(IV) complex shows the exact mass at m/z=669 and the fragmentation pattern is indicated in Scheme 3.

The results of thermogravimetric analyses of the complexes are given in Table 2. The thermogram of Dy(III) complex indicates the loss of half molecule of water of hydration and half molecule of ethanol in the temperature range 20–110 ºC (Exp. 5.7, Calcd. 7.1%), followed by loss of one molecule of coordinated water and OH group in the temperature range of 110–220 ºC (Exp. 5.7, Calcd. 7.7%) then, the chloride ions are lost in three successive steps in the temperature range of 220–576 ºC (Exp. 20.2, Calcd. 23.3%). Finally, the organic ligand decomposes in the temperature range 576–900 ºC (Exp. 33.1, Calcd. 33.8%) leaving Dy2O3 as a residue. TGA curve of Er(III) complex shows the loss of one

Scheme 1 Fragmentation pattern of Er(III) complex

Scheme 2 Fragmentation pattern of Dy(III) complex

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Scheme 3 Fragmentation pattern of Zr(IV) complex Table 2 Thermo analytical results (TG) of Er(III), Dy(III) and Zr(III) complex Complex

T range/ºC

Mass loss Estim (Calcd)/%

Assignment

[Er(ABH)(NO3)3H2O]H2O

50–120

4.2(3.3)

Loss of H2O (hydrated)

150–240

38.3(37.8)

Loss of H2O (coordinated)+3NO3

250–660

24.3(24.6)

Loss of PhCNHNH2

660–900

38.0(39.9)

Residue of Er2O3

20–110

5.7(7.1)

1/2H2O+1/2EtOH

110–220

5.7(7.7)

H2O (coordinated)+OH

[Dy(ABH) OH Cl2H2O]1/2H2O·1/2EtOH

[Zr(ABH)2 (OC2H5)2]Cl2·5/2C2H5OH

220–576

20.2(23.3)

Cl2

576–900

33.1(33.8)

Organic moiety decomposition

190–320

21.8(23.9)

Loss of Cl2+2C2H5OH

320–700

38.4(40.7)

2(Ph(NH2)CONH)

18.0(17.0)

Residue of ZrO2

molecule of water of hydration in the temperature range 50–120 ºC (Exp., 4.2, Calcd. 3.3%), followed by loss of one molecule of coordinated water and three nitrate ions in the temperature range 150–240 ºC (Exp., 38.3, Calcd. 37.8%). The organic moiety C6H4CNHNH2 is lost in the temperature range of 250–660 ºC (Exp. 24.3, Calcd. 24.6%), leaving Er2O3 as a residue (Exp. 38.0, Calcd. 39.9%). The thermogram of Zr(IV) complex shows that it loses 2.5 molecules of ethanol in two successive steps in the temperature range 40–190 ºC. The next step corresponds to the loss of Cl2 and two ethanol molecules in the temperature range 190–320 ºC (Exp. 21.8, Calcd. 23.9%). The final step corresponds to the loss of two molecules of the organic moiety (C6H4(NH2)CONH2) in the temperature range 320–700 ºC (Exp. 38.4, Calcd. 40.7%) leaving ZrO2 as a residue (Exp. 17.0, Calcd. 18.0%).

to the charge transfer band (LMCT)[21,22]. The electronic spectra were used to calculate the optical band gap of the complexes aiming to clarify the conductivity of these compounds. The optical band gap (Eg) of Zr(IV), Er(III) and Dy(III) complexes has been calculated from absorption spectra in Fig. 5. The measured absorbance (A) was used to calculate approximately the absorption coefficient (α) by using the relation α=1/d lnA (1) where, d is the width of the cell. The optical band gap (Eg)

2.5 Electronic spectra and optical band gap (Eg) The electronic spectrum of the ligand shows two bands at 35087 and 27248 cm–1 assigned to π→π* transition of the aromatic ring and n→π* transition in the carbonyl group, respectively[21,22]. The spectra of the complexes exhibit bands in the region 25252–24154 cm–1 attributed

Fig. 5 Electronic spectra of Dy (1), Er (2) and Zr (3) complexes

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is calculated from the relation: αhν=A(hν–Eg)m (2) where m is equal to 2 and 1/2 for direct and indirect transitions, respectively. A is an energy independent constant[23,24]. A direct band gap was obtained for all complexes (Fig. 6(a), (b) and (c)). From the curves it is clear that, the values of the band gap (Eg) equal to 4.3, 3.5 and 3.3 eV in case of Zr(IV), Dy(III) and Er(III) complexes, respectively. There is a trend between the atomic number of the central atoms and Eg values, indicating that Eg depends on the electronic configuration of the central ion. The optical band gap was theoretical calculated for optimized complexes and found to be 4.6, 3.6 and 3.0 eV. These values show good agreement with the measured optical band gap. The band gap values suggest that these complexes are semi-conductors. Also, the values of (Eg) are in the same range of highly efficient photovoltaic materials. So, the present compounds could be considered potential materials for harvesting solar radiation in solar cell applications[25]. 2.6 Morphological characterization of Er(III), Dy(III) and Zr(IV) complexes The properties of the materials depend on the particle size and the morphology. Transmittance electron microscope (TEM) is a powerful tool in determining the particle size and the shape. Fig. 7(a), (b) and (c) show the TEM images of Er(III), Dy(III) and Zr(IV) complexes, respectively. It is clear that the particles of Er(III) complex is eclipsed with size 200 nm, while, the particles of Dy(III) complex are irregular spheres with particle size in the range 8–40 nm with average 24 nm. The particles of Zr(IV) complex are

irregular slides with average size 285 nm. It is clear that Dy(III) complex has the smallest particles among the three complexes. 2.7 QSAR and anti-inflammatory activity Data base of 8 compounds were used in calculations[26]. Some physicochemical properties (descriptors) (Table 3) of the investigated compounds were calculated at the semi-empirical theoretical method AM1 by hyperchem version 8 program[17]. The data obtained from QSAR are used to deduce Eq. (1) by winks program 4.65[27]. % Inhibition of paw edema=0.2463368 Surface area approx+0.8899733 Surface area gride –0.7089817 Volume+13.207001 Hydration Energy –36.63369 lgP+ 0.9013315 Refractivity+121.54978 (1) This equation is validated by (F-value=44.35, P-value<0.054 and R=0.996), the most chief descriptor affecting the biological activity is surface area approx (P<0.001, 95% confidence). The descriptors of seven newly postulated structures (Fig. 8) are examined and the % inhibition of paw edema is calculated by applying Eq. (1). It was found that the postulated compound 7 (ABH) has the highest activity among the postulated compounds. In-vivo pharmacological evaluation of ABH, Er(III), Dy(III) and Zr(IV) complexes was carried out to assess their potential anti-inflammatory and analgesic activities. Animal treatment by meloxicam, (ABH), Er(III) complex, Dy(III) complex and Zr(IV) complex induced a significant anti-inflammatory effect and a significant decrease in Rheumatoid Index detectable by the 7th day big joint inflammation as compared with that of the arthritic

Fig. 6 Optical band gap of Dy(III) (a), Er(III) (b) and Zr(IV) (c) complexes

Fig. 7 TEM images of Er(III) (a), Dy(III) (b) and Zr(IV) (c) complexes

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Table 3 Theoretical (calculated by estimated equation) and anti-inflammatory activity after 8 h Calculated/%

Compound number

Experimental/%

Inhibition after 3 h

Inhibition after 3 h

1

70.40

2

31.22

3

Surface area –2

Volume/

Surface area

Hydration E./

lg P

Refractivity

–6.69

–0.21

84.14

–13.05

–2.04

129.9

–9.39

–0.05

117.15

1052.47

–7.74

1.09

115.06

1044.02

–8.81

0.72

115.49

610.22

1009.22

–8.7

0.34

110.9

700.82

1193.36

–11.03

–1.05

123.52

–2

2

–3

3

approx/10 nm

gride/10 nm

10 nm

70.4

365.6

468.23

780.13

33

499.36

795.56

1327.02

24.17

24.2

505.26

617.82

1065.05

4

26.55

26.6

509.72

633.8

5

22.49

22.5

506.54

623.6

6

41.08

41.1

484.57

7

35.09

35.1

534.81

29.5

(kcal/mol)

8

31.27

499.35

795.6

1327

–13.05

–2.04

129.9

Postulated 1

–37.197

435.98

552.52

976.05

–6.57

2.2

112.61

Postulated 2

–104.37

417.63

545.43

966.74

–13.65

1.30

109.93

Postulated 3

–41.75

436.29

549.41

974.76

–7.28

2.1

115.86

Postulated 4

–62.63

421.40

559.25

992.29

–12.94

0.33

111.83

Postulated 5

–59.04

462.49

572.59

1018.4

–7.32

2.57

120.65

Postulated 6

–32.20

439.81

560.04

992.17

–8.74

1.27

116.35

Postulated 7 (ABH)

182.52

223.9

375.08

570.6

–4.99

–2.72

47.49

Table 4 Anti-inflammatory and analgesic effects of meloxicam, (AABH), Er(III), Dy(III) and Zr(IV) complexes in collagen IIFreund’s adjuvant model of experimentally induced rheumatoid arthritis in rats ( n=6, M ± S.E) Group

Dose/(mg/200 g of

Morphology

rat weight)

(Inflammation)

Rheumatoid index

Analgesic effect Pain tolerance

Pain scoring

Non-arthritic non-treated

[SCMC] Solvent

1±0.00

2.33±0.09

14.33±2.01

1.00±0.00

Arthritic non-treated

[SCMC] Solvent

3.79±0.21*

5.0±0.14*

3.33±0.21*

3.87±0.21*

Meloxicam

0.4 mg

2.53±0.22*©

3.82±0.17*©

5.43±0.37*©

2.68±0.22*©

2-Aminobenzohydrazide

0.17 mg

2.55±0.23*©

3.66±0.18*©

5.11± 0.20*©

2.45±0.27*©

0.61 mg

*©

*©

*©

2.33±0.21*©

*©®

1.57±0.19*©®

*©

2.43±0.22*©

Er complex Dy complex Zr complex

0.51 mg 0.71 mg

2.57±0.23

*©®

1.47±0.11

*©

2.37±0.19

3.51±0.27

*©®

2.11±0.11

*©

3.67±0.11

5.33±0.46 8.15±0.42

5.67±0.21

SCMC 0.5% sodium carboxymethyl cellulose; * Compare with group NonArth Non treated (P<0.01); © Compare with group Arth Non treated (P<0.01); ® Compare with meloxicam (P<0.01)

Dy(III) complex treated group showed a significant increase in pain tolerance and a significant decrease in pain score detectable by the 7th day big joint inflammation as compared with meloxicam treated group and the other tested complexes groups (Table 4). The highest activity of Dy complex could be attributed to its smallest size among the tested compounds. It is small enough to penetrate easily through the cell membrane or scavenge the free radicals on the same microscopic level. Fig. 8 Postulated compounds

non-treated group (Table 4). Moreover, Dy(III) complex treated group showed a significant anti-inflammatory effect and a significant decrease in rheumatoid index detectable by the 7th day big joint inflammation as compared with meloxicam treated group (Table 4). The pain score was decreased and pain tolerance was increased by the 7th day in the treated groups with meloxicam, (ABH), Er(III) complex, Dy(III) complex and Zr(IV) complex as compared with that of the arthritic non-treated group (Table 4). It is worth noting that

3 Conclusions Up to our knowledge, literature survey showed that no work had been carried out on the present compounds ABH and its Er(III), Dy(III) and Zr(IV) complexes. These complexes were synthesized and characterized with different physicochemical techniques. The optical gap measurements showed that these compounds were semi-conductors and could be used as harvesting materials in solar cell devices. The ligand (ABH) and its complexes showed anti-inflammatory and analgesic effect.

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The investigated metal complexes had higher anti-inflammatory activity than the free ligand. New complexes of lanthanides and/or actinides with hydrazide moiety are expected to be potent anti-rheumatic agents.

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