Synthesis and Characterization of Some Complexes of Azo- Chalcone Ligand and Assessment of their Biological Activity

The azo-chalcone dye of theophylline namely (E)-1-(4-((E)-(theophyllin-8-yl) diazenyl)phenyl3-(4-dimethylaminophenyl)prop-2-en-1-one (TDPP) has been prepared and characterized by H-NMR, infrared, and electronic spectra, elemental analysis. Three solid complexes Mn(II), Ni(II) and Cu(II) of TDPP dye have been prepared and characterized by IR, electronic spectra, magnetic and conductivity measurements. The antibacterial and antifungal activities of the TDPP ligand and metal (II) complexes of Ni, and Cu are notable, with the copper(II) complex being more potent than the others. The TDPP ligand has interesting spectral properties as a pH sensor, solvent polarity sensor, and switches. Keyword: chalcone, biological activity, Azo dye, pH sensor, photochromism


1.Introduction
The chalcones are important classes of compounds widely used as antibacterial, anti-inflammatory, antifungal, anti-tubercular, antioxidant, antiviral, antitumor, anti-Alzheimer's disease agents and antimalarial [1][2][3]. The chalcone compounds synthesized under clean conditions such as under room temperature, small amount of solvent, high yield, and it is possible under ultrasound irradiation which is considered reactions of green chemistry doing fast under neat conditions [4].
All plant kingdom, fruits, vegetables and other plants have flavonoids that have chalcone structure [5][6][7]. Chalcones show trans (E) and cis (Z) isomers but in general trans isomer is more stable thermodynamic than cis isomer because there is high steric effect in structure of the cis isomer [6,8]. The vanadyl VO(II) complexes of chalcones which derivatives from benzaldehyde and acetophenone show activity against types of bacteria such as E. coli and Staphylococcus aureus and against funges such as P. notatum [9]. Ruthenium (II) chalcone complexes show binds with DNA through major groove of the DNA [10].
Azo dyes and their complexes show large applications in medical, dying sensor devices and indicators in chemistry. The 2-aminothiazole azo dye complexes exhibited antimicrobial activity in vitro against positive Gram bacteria such as Bacillus subtilis, negative Gram bacteria such as Escherichia coli, and against the yeast such as Candida albicans and fungus such as Aspergillus favus [11].
Chalcones and azo dyes are important classes of compounds appearing photochemistry applications which consider good photochromism based on forming a trans-cis isomerization process [12,13]. Azochalcone hybrids exhibited wide spectrum biological properties and photochemistry properties [14,15]. Diazenyl having chalcone exhibited activity against different microorganisms [16] and gave excellent fastness properties on fibre and polyester [17].

2.Materials and methods
Electronic spectra of TDPP dye and its complexes were assessed by UV-Vis, T80, PG instruments Ltd. IR spectra were done by (FTIR)-Platinum utilizing KBr disk in the range of (400-4000) cm -1 . Molar conductivity measurements of TDPP complexes were performed on 720(WTW). Mass spectrum of The chalcone dye synthesized under stirring for 3h by mixing 4-aminoacetophenone (1g, 0.0067 mole) with 4-dimethylaminobenzaldhyde (0.9 g, 0.0067 mole) in 30 mL ethanol in an alkaloid medium (KOH 0.5 g). The reaction mixture was neutralize by adding hydrochloric acid under cooling. The solution filtrated off, the yield was 90 %, bright orange powder. Azo-chalcone dye (TDPP) synthesized under cooling at 0 o C by mixing diazoinium salt of chalcone dye (0.5 g, 0.0018 mole of chalcone dye in 10 mL water with 3 mL HCl mixed with 0.13 g, 0.0018 mole of sodium nitrite under cooling) with 10 ml aqueous solution of theophylline (0.32g, 0.0018 mole) in alkaline medium (NaOH 0.5 g). Azochalcone dye was dark red powder, 60% yield. We also synthesized Azo-chalcone dye (TDPP) by diazotization of 4-aminoacetophenone then coupling with theophylline to form azo dye then coupling with 4-dimethylaminobenzaldhyde to form chalcone but the yield was low.
Complexes preparation: The dye complexes were made in the same way, by combining 0.2 g, 0.43 mmole dye dissolved in 30 mL ethanol with 0.21 mmole metal chloride (0.04g, 0.05 g and 0.02g corresponding to MnCl2.4H2O, NiCl2.6H2O and CuCl2 respectively dissolving in 5 mL distillate water, and then refluxing the mixture solution for 45 min. The solution was then filtered, and the precipitate was dried in a desiccator. Elemental

3.Results and discussions
Theophylline's azo-chalcone dye (TDPP) was made in two steps (Scheme 1), the first stage involved reacting 4-aminoacetophenone with 4-dimethylaminobenzaldehyde in ethanol with sodium hydroxide to produce orange chalcone with a 90% yield. The second stage included diazotization of chalcone followed by the diazotization salt of chalcone with an aqueous solution of theophylline in basic medium, resulting in a dye yield of 60%. H-NMR spectrum of (TDPP) as shown in Figure 1, the TDPP dye exhibited the following chemical shift, 9.   The TDPP dye exhibited red shift under increasing the polarity from hexane, DMSO, and ethanol to methanol as shown in (Figure 3).

Figure 3. Polarity Effect of solvents on TDPP dye
Theophylline's azo-chalcone dye (TDPP) showed actual photochromic behaviour (Figure 4) when exposed to 395 nm light, with trans azo converting to cis isomer with contribution from the converted trans chalcone isomer to cis under irradiation [18][19][20]. The new spectra of dye returned to the original spectra over time when the light was removed, which is consistent with real photochromic behaviour [21]. The complexes of Mn, Ni and Cu divalent ions of TDPP dye were prepared as shown in (Scheme 2) by reacting a hot solution of TDPP dye and hot solution of metal chloride of Mn, Ni and Cu divalent under mole ratio equal to 1:2 (M:Dye) which was suggested depending on mole ratio results as shown in Figure 5 for Mn (II) complex.  Table 1 such as N-H, CH aromatic and aliphatic, C=O, C=N, C=C, azo group. The basic differences between the spectra of dye ( Figure 6) and the spectra of complexes like the spectrum of Mn complex (Figure 7) are that the peaks of imine (C=N) and azo groups suffered down (red shift) around 5-19 cm -1 , indicating that these groups associated with metal ions.   The electronic spectra of the complexes of TDPP dye as shown in (Figure 8) were done in ethanol at room temperature. The electronic spectrum of TDPP dye exhibited band at 339 nm due to π→π* and another band is a shoulder at 405 nm due to n→π*. The electronic spectrum of manganese (II) of TDPP dye exhibited band at 324 nm due to due to π→π* of ligand and the second band was at 460 nm due to https://doi.org /10.37358/Mat.Plast.1964 and another band was at 723 nm. The magnetic susceptibility was 5.65 B.M. in agreement with the environment of the octahedral complex of manganese (II). The electronic spectrum of nickel complex of TDPP dye exhibited bands at 250 nm and 339 nm due to π→π* of TDPP dye in complex, and a band at 451 nm due to 3 A2g(F) → 3 T2g(P) and a band at 728 due to 3 A2g(F) → 3 T1g(F) of d-d transition of octahedral complex of nickel (II). The magnetic susceptibility was 3.35 B.M. in agreement with the environment of the octahedral complex of nickel (II).
The electronic spectrum of copper complex of TDPP dye exhibited three bands at 332 nm due to π→π* of TDPP dye in complex, and a band at 469 nm due to 2 B1g → 2 Eg and another band at 724 nm due to 2 B1g→ 2 A1g of d-d transition of octahedral complex of copper (II). The magnetic susceptibility was 1.87 B.M. in agreement with the environment of the octahedral complex of copper (II).

Biological activity
The antimicrobial activity of the synthesized ligand (TDPP dye) and its metal complexes were tested against two local bacterial organisms, Gram positive bacteria (Staphylococcus aureus) and Gram negative bacteria (Escherichia coli) ( Table 2). The antibacterial efficacy of synthesized compounds of TDPP dye was investigated (Staphylococcus aureus and Escherichia coli). The copper compound seemed to be selective against the bacteria. The copper complex had the highest inhibition zone and antibacterial efficacy against the bacteria. Nickel complex also exhibited high inhibition zone and antibacterial efficacy against Staphylococcus aureus. The ligand and other complexes did not show activity against all of gram +ve bacteria and gram -ve bacteria.

4.Conclusions
A new azo-chalcone dye of theophylline namely (E)-1-(4-((E)-(theophyllin-8-yl) diazenyl)phenyl)-3-(4-dimethylaminophenyl)prop-2-en-1-one (TDPP) and its complexes of Mn(II), Ni(II) and Cu(II) were synthesized and characterized. The TDPP dye exhibited a bathochromic shift under increasing the polarity of solvents. The UV-Vis spectral changes of TDPP dye indicated that light-induced trans to cis isomerization and reverse isomerism from cis to trans around the -N=N-bond with contribution from cis chalcone to trans chalcone isomer at room temperature. Antimicrobial experiments on a number of bacteria show that the complexes TDPP are more effective bactericides than the TDPP ligand and have high efficiency.