Analysis of New Piperidine Substituted Benzothiazole Crystalline Derivatives

Introduction

The benzothiazole derivatives possess superior biological and bio-physical properties such as antitumor and metabolic activities ¹, antimicrobial^2-5, imaging agents for β- amyloid ⁶ anti-cancer ⁷, anti-tuberculosis ⁸ anti-viral ⁹, anti-oxidant ¹⁰ and hence driven the attention of the researchers for further development. Several substituted benzothiazoles have been identified as potent anthelmintic drugs ^11-14. Aminobenzothiazoles have manifested a large scale of biological activities such as antiparkinsonian, dopa-mine antagonist^15-16, schistosomicidal agents ¹⁷, anticonvulsant activity ¹⁸, antileishmanial activity ¹⁹, analgesic agents ²⁰, and antiasthmatic drugs ²¹. Moreover, compounds containing condensed pyrimidines have been used as herbicide antidotes ²², and diuretics ²³. The BTA act as an effective catalyst ²⁴ and the crystal nature shows fluorophore property ²⁵. Based on earlier studies, an attempt is made to prepare benzothiazole derivatives. The prepared samples were characterized for their potential applications.

Experimental

Materials

The chemicals ethyl2-aminobenzo[d]thiazole-6-carboxylate, copper(II)bromide, t-nitrosobutane, piperidine, cesium carbonate, sodiumhydroxide, acetonitrile, dimethylformamide, methanol, hydrochloric acid, ethylacetate, dichloromethane, triethyl amines, sodiumsulphate, propanephosphonic acid anhydride, substituted amines were of  Sigma-Aldrich. These are used without purification. The dry ethyl acetate, hexane, and ethanol were obtained from Spectrochem for the crystallization process.

Instruments and methods

The Perkin-Elmer spectrum 100 series spectrophotometer was used for FTIR studies of the sample. The information about the nature and number of protons was studied from the 1HNMR spectrum. The ¹HNMR spectra were studied by using a 400MHz Varian spectrometer. The information about carbon was obtained from the ¹³CNMR spectrum of compound which was taken for the samples by subjected to 100MHz Brucker spectrometer with TMS as reference compound. With the help of Shimadzu mass spectrometer, the mass spectra were obtained. All the reactions were monitored by TLC plates and their spots were visualized by exposing them to a UV lamp, iodine chamber, or KMnO₄, and it was performed with silica gel 60-120mesh. The crystal formation and optical properties were ensured by powder XRD and photoluminescence studies respectively. The data were taken by XPERT-PRO- Gonio scan- 2 m diffractometer and Cary Eclipse- EL08083851 photo spectrometer. The elemental analysis was done by the Varian instrument (VARIO EL-3 series analyzer).

Synthesis and characterization

Synthesis of Ethyl 2-bromobenzo[d]thiazole-6-caroxylate

In a round bottom flask, 5g of ethyl2-aminobenzo[d]thiazole-6-carboxylate dissolved in 1eq of acetonitrile solvent then added 1eq of copper(II)bromide with t-nitrosobutane. The reaction mixture was mixed thoroughly using a magnetic stirrer up to 16h maintaining in the room temperature. It was monitored by TLC complies. After that, theethyl acetate was addedwith the reaction mixture to dilute it. The 1.5N HCl, water, and brine solution were used to wash the reaction mixture. Now the mixture was dried over sodium sulphate, and concentrated below 50 °C. The crude has proceeded to the next step without purification.

It was obtained as yellow solid. The yield was 54%. (LCMS: 95% purity). B.pt.139-40°C, IR (KBr, cm^-1): v_max 1742(C=O), 1647(C=N), 1324(C-N), 684(C-S), 610(C-Br). ¹HNMR (400 MHz, DMSO-d₆, ppm): δ 8.420 (s, 1H, ArH), 7.453-7.482 (d, 2H, J=11.6Hz ArH), 4.302 (m, 2H, -CH₂), 1.289-1.301 (t, 3H, J=4.8Hz -CH₃). ¹³CNMR (100 MHz, DMSO-d₆, ppm): δ 14.32, 60.50, 121.34, 123.52, 126.40, 128.63, 141.36, 155.77, 165.62. For C₁₀H₈BrNO₂S, Calculated: C-41.97%, H-2.82%, Br-27.92%, N-4.89%, 0-11.19%, S-11.21%.Found: C-42.04%, H-2.90%, Br-27.86%, N-4.92%, 0-11.13%, S-11.15%. LCMS [M+1] ⁺: m/z 287.1.

Synthesis of Ethyl 2-(piperidin-1-yl)benzo[d]thiazole-6-caroxylate (3)

The obtained compound (2) was dissolved in DMF and added to the N-alkylation base (CS₂CO₃ 1.5eq). Now piperidine (1.1 eq) was added and then subjected for thermal treatment to a temperature of 100 °C for 3 h. After complies, it was cooled and purified to get compound (III).

It was obtained as orange solid with 56% yield, (LCMS: 95.7% purity), m.pt.161-162°C, IR (KBr, cm^-1): v_max 1740(C=O), 1643(C=N), 1326(C-N), 681(C-S). ¹HNMR (400 MHz, DMSO-d₆, ppm): δ 1.536-1.553 (m, 6H, -CH₂), 3.691-3.724, (t, 4H, J=13.2Hz -CH₂) 8.414 (s, 1H, ArH), 7.697-7.721 (d, 2H, J=9.2Hz ArH), 4.292 (m, 2H, -CH₂), 1.292-1.313 (t, 3H, J=8.4Hz -CH₃). ¹³CNMR (100 MHz, DMSO-d₆, ppm): δ 14.44, 24.21, 25.45, 54.2, 61.02 116.55, 123.26, 126.57, 130.61, 157.62, 165.87, 168.13. For C₁₅H₁₈N₂O₂S, Calculated:C-62.04%, H-6.25%, N- 9.65%, 0-11.02%, S-11.04%.Found: C-61.98%, H-6.27%, N-9.69%, 0-11.05%, S-11.01%. LCMS [M+1] ⁺: m/z 291.3.

Synthesis of 2-(piperidin-1-yl)benzo[d]thiazole-6-caroxylic acid (4)

The 2 g measured compound (3) was dissolved in methanol. Now, 2 eq sodium hydroxide solution (NaOH dissolved in water) was added. Now it was stirred for a time duration of 1h at room temperature. After TLC complies, acidified with 1.5N HCl. Then it was extracted with ethyl acetate. The organic layer was washed with water, dried, and concentrated. With the help of column chromatography crude was purified and compound eluted with methanol (2.4%) and DCMto get the desired product.

It was obtained as yellow solid of 67% of yield, (LCMS: 95.3% purity), m.pt.169-70 °C, IR (KBr, cm^-1): v_max 3242(O-H), 1761(C=O), 1645(C=N), 1321(C-N), 684(C-S). ¹HNMR (400 MHz, DMSO-d₆, ppm): δ 1.546-1.5621 (m, 6H, -CH₂), 3.716-3.734 (t, 4H, J=7.2Hz -CH₂) 8.618, (s, 1H, ArH), 7.882-7.894 (d, 2H, J=74.8Hz ArH), 11.121 (s, 1H, -OH). ¹³CNMR (100 MHz, DMSO-d₆, ppm): δ 24.14, 25.52, 54.36, 116.74, 123.62, 126.88, 130.73, 158.55, 166.72, 168.15. For C₁₃H₁₄N₂O₂S,Calculated: C-59.52%, H-5.38%, N-10.68%, 0-12.20%, S-12.22%. Found:C-59.59%, H-5.41%, N-10.72%, 0-12.12%, S-12.16%. LCMS [M+1]⁺: m/z.263.3.

Preparation of benzothiazole derivatives (5a-e)

In the solvent dichloromethane (1 mL), one equivalent (100 mg) weighed compound(4) was dissolved. Now the solution was added to simple amine (1eq), triethylamine (2 eq). The mixture was stirred for 2h. Then cooled to zero degrees Celsius. Now, propane phosphoric acid anhydride (T3P) (50% in ethyl acetate) (1.5 eq) was added and again stirred for 12h. At the end of the reaction, monitor by TLC, the addition of ice waterwas done and extracted with dichloromethane.Finally washed in water and brine solution, dried over sodium sulphate, then concentrated. The purification of crude was made by column chromatography (using silica gel) eluent (petroleum ether and 50 – 70% of ethyl acetate) to get desired product(5a-e). All the reaction schemes were shown in Fig.1. The yield and melting point of these samples are presented in Table.1.

Figure 1: The reaction scheme Click here to View figure

Table 1: Results of reaction Click here to View table

Synthesis of N-phenyl-2-(piperidin-1-yl)benzo[d]thiazole-6-carboxamide(5a)

The aniline was used to obtain the above compound (5a). The reactions results as white crystalline solid of 68% yield. (LCMS: 96.1% purity), m.pt.230-31 °C, IR (KBr, cm^-1): v_max3230(N-H), 1629(C=O), 1629(C=N), 1322(C-N), 691(C-S).¹HNMR (400 MHz, DMSO-d₆, ppm): δ1.542-1.562 (m, 6H, -CH₂), 3.742-3.761 (t, 4H, J=7.6Hz -CH₂), 7.921-7.942 (d, 1H, J=8.4Hz ArH), 7.635-7.641 (d, 3H, J=2.4Hz ArH), 8.382 (s, 1H, ArH), 9.194 (s, 1H, -NH), 7.293-7.316 (t, 3H, J=9.2Hz ArH).¹³CNMR (100 MHz, DMSO-d₆, ppm): δ 24.32, 25.26, 54.48, 121.17, 121.73, 123.85, 128.41, 131.07, 137.58, 156.53, 164.36, 167.92.For C₁₉H₁₉N₃O₂S. Calculated:C-67.63%, H-5.68%, N-12.45%, 0-4.74%, S-9.50%. Found:C-67.57%, H-5.71%, N-12.41%, 0-4.79%, S-9.52%. LCMS [M+1] ⁺: m/z.337.4.

Synthesis of N-(tert-butyl)-2-(piperidin-1-yl)benzo[d]thiazole-6-carboxamide(5b).

The t-butyl amine was added that reacts to give the compound 5(b). It was obtained as a white crystalline solid with a 72% yield. (LCMS: 95.3% purity), m.pt.233-34 °C, IR (KBr, cm^-1): v_max3333(N-H), 1625(C=O), 1625(C=N), 1321(C-N), 694(C-S). ¹HNMR (400 MHz, DMSO-d₆, ppm): δ 1.548-1.591(m, 6H, -CH₂), 3.695-3.702(t, 4H,J=2.8Hz -CH₂), 7.878-7.895(d, 1H,J=6.8Hz ArH), 7.672-7.685(d, 1H,J=5.2Hz ArH), 8.402(s, 1H, ArH), 8.108(s, 1H, -NH), 1.402(s, 9H, -CH₃).¹³CNMR (100 MHz, DMSO-d₆, ppm): δ 24.58, 25.32, 29.15, 54.62, 59.57, 121.13, 121.66, 123.72, 130.85, 156.42, 169.84, 168.12. For C₁₇H₂₃N₃OS, Calculated: C-64.32%, H-7.30%, N-13.24%, 0-5.04%, S-10.10%. Found: C-64.38%, H-7.26%, N-13.21%, 0-5.01%, S-10.14%. LCMS [M+1] ⁺: m/z.317.4.

Synthesis of N-(3,4-difluorophenyl)-2-(piperidin-1-yl)benzo[d]thiazole-6-carboxamide(5c).

The compound 5(c) was obtained by the addition of 3,4-difluoro aniline. It was obtained as a white crystalline solid with a 63% yield, (LCMS: 95.6% purity), m.pt.218-19 °C, IR (KBr, cm^-1): v_max3262(N-H), 1638(C=O), 1638(C=N), 1324(C-N), 1240(C-F), 687(C-S).¹HNMR (400 MHz, DMSO-d₆, ppm): δ1.538-1.556(m, 6H, -CH₂), 3.707-3.719(t, 4H,J=4.8Hz -CH₂), 7.796-7.812(d, 1H,J=6.4Hz ArH), 7.578-7.601(d, 3H,J=9.2Hz ArH), 8.412(s, 1H, ArH), 9.562(s, 1H, -NH), 7.742(s, 1H, ArH).¹³CNMR (100 MHz, DMSO-d₆, ppm): δ 24.58, 25.43, 54.56, 111.61, 114.95, 121.27, 121.73, 123.98, 130.92, 145.26, 147.22, 156.47,164.57, 168.03.For C₁₉H₁₇F₂N₃OS, Calculated: C-61.11%, H-4.59%, F-10.18%, N-11.25%, 0-4.28%, S-8.59%. Found: C-61.02%, H-4.52%, F-10.24%, N-11.30%, 0-4.31%, S-8.61%. LCMS [M+1]⁺: m/z.373.4.

Synthesis of morpholine(2-(piperidin-1-yl)benzo[d]thiazol-6-yl)-methanone(5d).

The addition of morpholine yields compound 5(d). It was obtained as pale yellow crystalline solid, with a 70% yield. (LCMS: 93% purity), m.pt.128-29 °C, IR (KBr, cm^-1): v_max3332(N-H), 1625(C=O), 1625(C=N), 1330(C-N), 682(C-S).¹HNMR (400 MHz, DMSO-d₆, ppm): δ 1.526-1.549(m, 6H, -CH₂), 3.720-3.738(t, 4H,J=7.2Hz -CH₂), 7.901-7.925(d, 1H,J=9.6Hz ArH), 7.645-7.681(d, 1H,J=14.4Hz ArH), 8.421(s, 1H, ArH), 3.591-3.615 (t, 8H,J=11.2Hz -CH₂).¹³ CNMR (100 MHz, DMSO-d₆, ppm): δ 24.29, 25.63, 36.47, 46.33, 54.37, 66.18, 121.22, 121.67, 123.96, 131.10, 156.45, 168.17, 168.81.For C₁₇H₂₁N₃O₂S, Calculated: C-61.61%, H-6.39%, N-12.68%, 0-9.65%, S-9.67%. Found: C-61.68%, H-6.35%, N-12.64%, 0-9.69%, S-9.64%. LCMS [M+1]⁺: m/z.331.4.

 Synthesis of N-cyclopropyl-2-(piperidin-1-yl)benzo[d]thiazole-6-carboxamide(5e).

The reaction of cyclopropyl amine and the compound (5) results the compound 5(e) in the form of white crystalline solid. Its yield percentage is 76%.  (LCMS: 95.4% purity), m.pt.240-41 °C, IR (KBr, cm^-1): v_max3267(N-H), 1623(C=O), 1623(C=N), 1290(C-N), 672(C- S).¹HNMR (400 MHz, DMSO-d₆, ppm): δ 1.536-1.569 (m, 6H, -CH₂), 3.701-3.718(t, 4H,J=6.8Hz -CH₂), 7.902-7.916(d, 1H,J=6.0Hz ArH), 7.625-7.646(d, 1H,J=8.4Hz ArH), 8.368(s, 1H, ArH), 8.102(s, 1H, -NH), 2.765 (m, 1H, -CH), 0.612-0.850(m, 4H, -CH₂).¹³CNMR (100 MHz, DMSO-d₆, ppm): δ 6.52, 24.45, 25.28, 26.62, 54.67, 121.08, 121.82, 123.74, 130.82, 156.55, 168.23, 167.14.For C₁₆H₁₉N₃OS, Calculated: C-63.76%, H-6.35%, N-13.94%, 0-5.31%, S-10.64%. Found: C-63.68%, H-6.41%, N-13.91%, 0-5.39%, S-10.61%. LCMS [M+1]⁺: m/z 301.4.

Result and discussion

The functional groups present in all the compounds were identified by FTIR spectra of these compounds. The compound 5c shows an additional peak due to C-F functional group at 1240 cm^-1. The result of FTIR confirms the formation of the synthesized compounds. In ¹HNMR, all the compounds display the almost same chemical shift values. However, in compound 5d singlet due to N-H is disappeared. It is because of the presence of two R-groups instead of one R-group and one H-atom which were present in all other groups. Similarly, when comparing the ¹HNMR compounds display the almost same chemical shift values. However, in compound 5d singlet due to N-H is disappeared. It is because of the presence of two R-groups instead of one R-group and one H-atom which were present in all other groups. Similarly, when comparing the ¹HNMR compounds display the almost same chemical shift values. However, in compound 5d singlet due to N-H is disappeared. It is because of the presence of two R-groups instead of one R-group and one H-atom which were present in all other groups. Similarly, when comparing the ¹HNMR spectrum of the compounds 5a and 5c, it is observed that the doublet at δ (7.635-7.641 ppm) is changed as a singlet at δ (7.742 ppm). It is due to the substitution of fluorine that replaces hydrogen at C-3 in aniline. The same result was also obtained in ¹³CNMR the chemical shift value changes from 128.41 to 145.26 ppm. The structure of these compounds was confirmed from the ¹HNMR and ¹³CNMR. From the table.1, it is observed that the melting point of the synthesized compounds is almost the same except for compound 5d. The compound 5d shows a lower melting point value. The addition of heterocyclic compound (Morpholine) weakens the bond and hence reduces the melting point. The results of LCMS analysis establish the formation of the products. The percentage of the elements present in the products was obtained from elemental analysis. These values agree with theoretically calculated values. Hence the formation of the products is also confirmed from this analysis.

Antibacterial and antifungal activity

Antibacterial activity

In earlier days, simple and easy method of screening the antibacterial activity of a sample by the agar well diffusion method was used (Perez et al., 1990, Perez et al., 1999, Bagamboula et al., 2004 and Erdemoglu et al., 2003). In Brain Heart Infusion (BHI) (Difco, Detroit, MI) broth the microorganism was suspended. It was diluted to roughly 106 colony-forming units (cfu) per mL. On the surface of BHI agar and Sabouraud Dextrose Agar (SDA) (Difco, Detriot, MI), these diluted microorganisms were spread as “flood-inoculated”. Then it was dried. The SDA was used for         C. albicans and C. tropicalis,. The wells of 5 mm size were cut from the agar using a sterile cork-borer. Now 25µL of the sample solutions were poured in these wells. The plates were kept in an incubation chamber for 18 h at 35°C. The measurement of zone of inhibition gives the antimicrobial activity of the samples. Ciprofloxacin (10 μg/mL) was the standard drug for antibacterial activities. The tests were carried out in duplicates. The diameter of inhibition zone was measured and interpreted.

The Minimal Inhibitory Concentration (MIC) and Minimal Bactericidal Concentration (MBC) was measured by the broth dilution method (Van der Berghe and Vlietinck, 1991). About 1.0 to 0.25 mg/mL diluted plant extract was used. Test bacteria culture with concentration of 105 CFU/mL was used. After 24 h of incubation at 37°C the MIC values were taken as the lowest plant extracts concentration whichrestricts visible bacterial growth and MBC was the lowest concentration that completely inhibited bacterial growth. In this method the reference was Ciprofloxacin. The experimental procedure was done thrice. The antibacterial activity of all the synthesized compounds was tested in-vitro against pathogenic Enterococcus feacalis, Staphylococcus aureus, Escherichia coli, and Salmonella typhi. The results are presented in Table.2.

Table 2: Antibacterial activity of the compounds

Microorganisms	Control	5a	5b	5c	5d	5e	Ciprofloxacin
		Zone of inhibition in mm
Enterococcus faecalis	–	10.5±0.55	11.24±0.67	18.45±0.44	07.44±0.56	11.54±0.67	35.56±0.55
Staphylococcus aureus	–	08.42±0.10	07.12±0.10	10.56±0.66	12.34±0.30	07.55±0.10	40.54±0.48
Escherichia coli	–	07.55±0.00	08.15±0.00	11.87±0.54	13.44±0.45	08.45±0.00	38.54±0.60
Salmonella typhi	–	06.67±0.22	09.21±0.00	08.22±0.00	08.57±0.00	09.45±0.00	35.76±0.10

Figure 2: Antibacterial activity Click here to View figure

Antifungal activity

As reported earlier by Alves and Cury, 1992 , the samples were examined for antifungal activity by dilution in agar technique. A 100mg plant extracts were dissolved in 1 mL of dimethyl sulfoxide (DMSO) and thenundergone two fold dilution in Yeast Nitrogen Base Phosphate (YNBP) agar (Merck, Germany) to get a concentration range of 31.25-1000µL/mL. The YNBP agar plates having only DMSO diluted in the same way, that didn’t influence the fungal growth, were used as controls. These fungal strains were suspended in sterile physiological Tris buffer (pH 7.4, 0.05 M), homogenized, and adjusted to an OD (530 nm) of 0.05 (equivalent to 1 X 106 CFU/mL). This suspension was used as the inoculum for the test in the agar plates. Using an automatic micropipette,the fungal suspensions (3µL) were inoculated. These plates (diameter: 25 cm) were kept for incubation at 37^oC for 48 h. The minimal inhibitory concentration (MIC) is defined as the minimum concentration of the plant extracts required to inhibit completely the visible growth of the fungus. Ketoconazole was used as a reference and appropriate controls with no plant extracts were used. Each experiment was carried out for three times. The antifungal activity of all the synthesized compounds was tested in-vitro against pathogenic Aspergillus niger, Aspergillus flavus, Candida albicans, and Penicillium sps. The results are given in Table.3. 

Table 3: Antifungal activity of the compounds

Microorganisms	Control	5a	5b	5c	5d	5e	Ketoconazole
		Zone of inhibition in mm
Aspergillus niger	–	07.32±0.10	08.13±0.00	10.55±0.20	10.67±0.10	08.34±0.00	12.54±0.50
Aspergillus flavus	–	06.35±0.00	06.64±0.10	08.22±0.01	09.56±0.30	07.10±0.10	09.30±0.30
Candida albicans	–	08.34±0.10	11.24±0.20	07.35±0.00	10.45±0.00	12.15±0.20	12.44±0.40
Penicillium sps	–	07.10±0.00	07.15±0.10	7.50±0.00	08.25±0.02	07.40±0.10	15.34±0.10

Figure 3: Antifungal activity Click here to View figure

Powder XRD studies

The powder XRD pattern is shown in fig. 4. From the graph, it is observed that the peaks are sharp and intense. This shows that the sample is pure and crystalline in nature.

Figure 4: Powder X-ray diffraction pattern of N-phenyl-2-(piperidin-1-yl)benzo[d]thiazole-6-carboxamide(5a) Click here to View figure

The crystalline size is calculated from the Debye-scherrer formula

λ → wavelength 1.546 A°

β → Full width half (0.1476deg = 0.002576 rad)

θ → Angle of diffraction(16.1967/2 = 8.09835 deg = 0.14134 rad)

D = 0.9 X 0.154/0.002576  Cos(0.14134)

D = 54.3652 nm.

The crystalline size of the samples are calculated and presented in Table.4

Table 4: Crystalline size of the compounds

S.No	Compound name	Size (nm)
1	5a	54.3652
2	5b	54.4454
3	5c	54.2976
4	5d	54.4046
5	5e	54.6069

Figure 5: Powder X-ray diffraction pattern ofcompounds 5b to 5e Click here to View figure

Generally, the crystalline size value will increase or decrease depending on the ordering inside the material. So when materials are added it will disturb the order of the parent compound also the additional compound produces strain inside the crystal. For example, the crystalline size of the compounds figure 5a and 5e are compared and presented in table. 4. It is observed that the crystalline size of compound 5a is less than that of compound 5e. It is because in compound 5a more carbon atoms are present when compared with compound 5e. The more carbon atoms produce more amount of strain that restricts the growth and size of the crystal.

Photoluminescence

The photoluminescence (PL) spectrum examines material for its wide applications in the field of medical, biochemical, and chemical research. In PL spectroscopy, generally, a beam of light excites the electrons in the molecule of given materials and causes them to emit light in a longer wavelength than the observed radiation. The figures Fig.6 to Fig.7 show the PL spectra of the samples. These spectra give the absorption wavelength at 362 to 381 nm which means the emission of blue radiation. The absorption peak is due to the band-to-band electronic transition in a material. The result predicts the use of the materials as a color filter.

Figure 6: Photoluminescence spectrum of N-phenyl-2-(piperidin-1-yl) benzo[d]thiazole-6-carboxamide(5a) Click here to View figure

Figure 7: Photoluminescence spectrum of compounds 5b to 5e Click here to View figure

Conclusion

The synthesis of derivatives of benzothiazole (5a-e) was carried out. The functional groups present in the samples were studied from the FTIR spectra and thus it confirms the synthesis of the compounds. The proton and carbon positions of these were obtained through 1HNMR and 13CNMR spectra respectively. The LCMS study indicates the good yield of all the compounds. The synthesized compounds exhibited antibacterial and antifungal activities. From the antibacterial test the compounds 5c, 5d, 5d, and 5e are show the highest activity of Enterococcus feacalis, Staphylococcus aureus, Escherichia coli, and Salmonella typhi, respectively. In the antifungal activity test the compounds 5c & 5d, 5d, 5b &5e, and 5d show the higher activity of Aspergillus niger, Aspergillus flavus, Candida albicans, and Penicillium sps, respectively. The crystalline nature of the samples was confirmed by the powder X-ray diffraction studies. These samples show good optical nature as studied from the PL study. Hence the synthesized compounds can be used as color filters and in pharmaceutical applications.

Acknowledgement

The authors are thankful to Alagappa University, Karaikudi, Tamilnadu for powder XRD, elemental analysis and photolumiscence studies, Government Arts College, Tiruvannamalai for FTIR and melting point test, European Advance Limited, Bangalore for LCMS test, Micro Labs, Vellore for biological activity studies, VIT University, Vellore for NMR tests.  

Conflict of interest

The authors declare no conflict of interest

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