Ligand C20H18N4O,ðHL<sup>23</sup><sup>Þ</sup>

The ligand HL23 was synthesized by refluxing equimolar amounts of 4-amino-2,3-dimethyl-1 phenyl-3-pyrazolin-5-one and indole-3-carboxaldehyde in methanol according to the experimental protocol described in Ref. [67].

Complexes 16–21 were prepared by direct reaction between the ligand and the corresponding metal salts (Figures 19, 20) [67].

$$\left[\mathbf{Cu}(\mathbf{L}^{\mathsf{23}})\_{\mathsf{2}}\mathbf{Cl}\_{\mathsf{2}}\right] \tag{16}$$

To a stirred solution of CuCl2�2H2O (1mmol) in ethanol (15mL) was added a solution of ligand HL<sup>23</sup> (1mmol) in ethanol (15mL). The mixture was stirred at reflux temperature for 2h. The resulting precipitate of green-brown color was filtered, washed with ethanol, and dried.

$$\left[\mathbf{Cu}(\mathbf{L}^{23})\_2\right] \left(\mathbf{NO}\_3\right)\_2\tag{17}$$

Complex 17 was prepared similarly, using Cu(NO3)2�3H2O (1mmol). Brown solid.

$$[ (\mathbf{Cu}(\mathbf{L}^{23})\_2(\mathbf{OAc})\_2 ]\tag{18}$$

Figure 19. X-ray molecular structure of ligand HL23.

Transition Metal Complexes with Antipyrine‐Derived Schiff Bases: Synthesis and Antibacterial Activity http://dx.doi.org/10.5772/67584 81

Figure 20. Proposed structures of the metal complexes 16–21.

<sup>½</sup>Cu2ðL<sup>22</sup>Þ2ðH2OÞ4� SO4 (15)

<sup>½</sup>CuðL23Þ2Cl2� (16)

<sup>½</sup>CuðL23Þ2� ðNO3Þ<sup>2</sup> (17)

<sup>½</sup>CuðL<sup>23</sup>Þ2ðOAcÞ2� (18)

Complex 15 was prepared similarly, using CuSO4�5H2O (2mmol). Dark-green solid.

Ligand C20H18N4O,ðHL<sup>23</sup><sup>Þ</sup>

The ligand HL23 was synthesized by refluxing equimolar amounts of 4-amino-2,3-dimethyl-1 phenyl-3-pyrazolin-5-one and indole-3-carboxaldehyde in methanol according to the experi-

Complexes 16–21 were prepared by direct reaction between the ligand and the corresponding

To a stirred solution of CuCl2�2H2O (1mmol) in ethanol (15mL) was added a solution of ligand HL<sup>23</sup> (1mmol) in ethanol (15mL). The mixture was stirred at reflux temperature for 2h. The resulting precipitate of green-brown color was filtered, washed with ethanol, and dried.

Complex 17 was prepared similarly, using Cu(NO3)2�3H2O (1mmol). Brown solid.

2.2.1.3. Synthesis of the complexes with ligand HL<sup>23</sup>

80 Descriptive Inorganic Chemistry Researches of Metal Compounds

mental protocol described in Ref. [67].

Figure 19. X-ray molecular structure of ligand HL23.

metal salts (Figures 19, 20) [67].

Complex 18 was prepared similarly, using Cu(OAc)2�H2O (1mmol). Dark-green solid.

$$\left[\mathbf{Cu}(\mathbf{L}^{23})\_2(\mathbf{H\_2O})\_2\right]\mathbf{SO\_4} \tag{19}$$

Complex 15 was prepared similarly, using CuSO4�5H2O (1mmol). Green solid.

$$\left[\mathbf{VO}(\mathbf{L}^2)\_2(\mathbf{H}\_2\mathbf{O})\right]\mathbf{SO}\_4\tag{20}$$

Complex 20 was prepared in a similarly, using VOSO4�2H2O. Green solid.

$$[\text{Ni}(\text{L}^{23})\_2(\text{H}\_2\text{O})\_2]\text{Cl}\_2\tag{21}$$

Complex 21 was prepared in a similarly, using NiCl2�6H2O. Dark-green solid.

Figure 21. X-ray molecular structure of ligand HL<sup>24</sup> and complex 23.

2.2.1.4. Synthesis of the complexes with ligand HL<sup>24</sup>

$$\text{Light} \gets \text{19} \\ \text{H}\_{20} \\ \text{N}\_4 \\ \text{O}\_3, (\text{HL}^{24})$$

The ligand HL24 was synthesized by refluxing equimolar amounts of 4-amino-2,3-dimethyl-1 phenyl-3-pyrazolin-5-one and pyridoxal hydrochloride in methanol according to the experimental protocol described in Ref. [68].

Complexes 22–28 were prepared by direct reaction between the ligand and the corresponding metal salts (Figures 21, 22) [68].

$$[\mathbf{CuL^{24}Cl}]\_2\tag{22}$$

To a hot solution of HL24 (1mmol) in methanol was added a hot solution of CuCl2�2H2O (2mmol) in aqueous/methanol (1:2 v/v), and the mixture was stirred at reflux temperature for 4h. Brown solid.

$$\left[\mathrm{CuL^{24}(H\_2O)\_2}\right]\mathrm{NO\_3}\cdot\mathrm{2.25H\_2O}\tag{23}$$

Complex 23 was prepared similarly, using Cu(NO3)2�3H2O (1mmol). The mixture was stirred at room temperature for 7h. Brown solid, X-ray quality single crystals were obtained.

$$\left[ (\mathbf{Cu}(\mathbf{L}^{\mathsf{24}})(\mathbf{OAc})(\mathbf{H\_{2}O}) \right] \tag{24}$$

Complex 24 was prepared similarly, using Cu(OAc)2�H2O (2mmol). The mixture was stirred at reflux temperature for 4h. Green-brown solid.

Transition Metal Complexes with Antipyrine‐Derived Schiff Bases: Synthesis and Antibacterial Activity http://dx.doi.org/10.5772/67584 83

Figure 22. Proposed structures of the metal complexes 22, 24–28.

2.2.1.4. Synthesis of the complexes with ligand HL<sup>24</sup>

82 Descriptive Inorganic Chemistry Researches of Metal Compounds

Figure 21. X-ray molecular structure of ligand HL<sup>24</sup> and complex 23.

mental protocol described in Ref. [68].

reflux temperature for 4h. Green-brown solid.

metal salts (Figures 21, 22) [68].

Ligand C19H20N4O3,ðHL<sup>24</sup><sup>Þ</sup>

The ligand HL24 was synthesized by refluxing equimolar amounts of 4-amino-2,3-dimethyl-1 phenyl-3-pyrazolin-5-one and pyridoxal hydrochloride in methanol according to the experi-

Complexes 22–28 were prepared by direct reaction between the ligand and the corresponding

<sup>½</sup>CuL24Cl�

To a hot solution of HL24 (1mmol) in methanol was added a hot solution of CuCl2�2H2O (2mmol) in aqueous/methanol (1:2 v/v), and the mixture was stirred at reflux temperature for 4h. Brown solid.

Complex 23 was prepared similarly, using Cu(NO3)2�3H2O (1mmol). The mixture was stirred

Complex 24 was prepared similarly, using Cu(OAc)2�H2O (2mmol). The mixture was stirred at

at room temperature for 7h. Brown solid, X-ray quality single crystals were obtained.

<sup>2</sup> (22)

<sup>½</sup>CuL24ðH2OÞ2� NO3 � <sup>2</sup>:25H2O (23)

<sup>½</sup>CuðL<sup>24</sup>ÞðOAcÞðH2OÞ� (24)

$$\left[\mathbf{CuL^{24}(H\_2O)\_2}\right]\mathbf{ClO\_4}\tag{25}$$

Complex 25 was prepared similarly, using Cu(ClO4)2�6H2O (2mmol). The mixture was stirred at reflux temperature for 5h. Brown solid.

$$\left[ (\mathbf{C}\mathbf{u}\_2(\mathbf{L}^{\mathsf{24}})\_2(\mathbf{SO}\_4)(\mathbf{H}\_2\mathbf{O})\_2 \right] \tag{26}$$

Complex 26 was prepared in a similar fashion to complex 24, using CuSO4�5H2O. The mixture was stirred at reflux temperature for 4h, giving a dark-red precipitate.

$$[\mathbf{CuL}^{24}(\mathbf{NCS})] \cdot 2\mathbf{H\_2O} \tag{27}$$

For the synthesis of complex 27, the acetate complex was first prepared and the acetate ion was then displaced by thiocyanate ion by using KSCN (2mmol). Green solid.

$$[\mathbf{VO}(\mathbf{L}^{24})\_2] \tag{28}$$

Complex 28 was prepared in a similar fashion to complex 24, using VOSO4�2H2O. Brown solid.

#### 2.3. Antibacterial activity

The complexes and ligands HL21–<sup>24</sup> were tested for their in vitro antibacterial activity against de Staphylococcus aureus var. Oxford 6538, Klebsiella pneumoniae ATCC 100131, Escherichia coli ATCC 10536, and Pseudomonas aeruginosa ATCC 9027 strains using the paper disc diffusion method (for the qualitative determination) and the serial dilutions in liquid broth method (for determination of MIC) [66]. Streptomycin was used as internal standard.

The results of the antibacterial activity point out the fact that the activity of the Schiff bases HL21–<sup>24</sup> is more pronounced when it coordinates at the metal ion (Table 1). In case of complexes 1, 6, 10, 12, 15, 18, 19, 20, 23, 25, 26, and 28, there can be seen a visible increase in the antibacterial action.

Missing a clear action mechanism, in vitro, of the respective ligand of the complexes obtained on a microbian stem, there can be made the following stipulations:




<sup>½</sup>Cu2ðL<sup>24</sup>Þ2ðSO4ÞðH2OÞ2� (26)

<sup>½</sup>CuL<sup>24</sup>ðNCSÞ� � 2H2O (27)

<sup>½</sup>VOðL<sup>24</sup>Þ2� (28)


and SO4

2-, respectively, and

Complex 26 was prepared in a similar fashion to complex 24, using CuSO4�5H2O. The mixture

For the synthesis of complex 27, the acetate complex was first prepared and the acetate ion was

Complex 28 was prepared in a similar fashion to complex 24, using VOSO4�2H2O. Brown solid.

The complexes and ligands HL21–<sup>24</sup> were tested for their in vitro antibacterial activity against de Staphylococcus aureus var. Oxford 6538, Klebsiella pneumoniae ATCC 100131, Escherichia coli ATCC 10536, and Pseudomonas aeruginosa ATCC 9027 strains using the paper disc diffusion method (for the qualitative determination) and the serial dilutions in liquid broth method

The results of the antibacterial activity point out the fact that the activity of the Schiff bases HL21–<sup>24</sup> is more pronounced when it coordinates at the metal ion (Table 1). In case of complexes 1, 6, 10, 12, 15, 18, 19, 20, 23, 25, 26, and 28, there can be seen a visible increase in the

Missing a clear action mechanism, in vitro, of the respective ligand of the complexes obtained




was stirred at reflux temperature for 4h, giving a dark-red precipitate.

84 Descriptive Inorganic Chemistry Researches of Metal Compounds

then displaced by thiocyanate ion by using KSCN (2mmol). Green solid.

(for determination of MIC) [66]. Streptomycin was used as internal standard.

on a microbian stem, there can be made the following stipulations:

ity. The complexes 5, 6, 15, 19, 20, and 25 contain the groups ClO4

prevent a visible increase in their activity against all species of bacteria used.

2.3. Antibacterial activity

antibacterial action.

the metal center.

link π out of the plan.


K. pneumoniae (Klebsiella pneumoniae ATCC 31488); S. aureus (Staphylococus aureus var. Oxford ATCC 6538); P. aeruginosa (Pseudomonas aeruginosa ATCC 9027); E. coli (Escherichia coli ATCC 10536). G(): Gram-negative bacteria; G(+): Grampositive bacteria.

Table 1. "In vitro" antibacterial activity of the ligands and corresponding complexes.
