Synthesis, Characterization and Antibacterial Activity of O-Alkyl/O-Aryl trithiophosphate derivatives of Niobium (V)

 

Suman Bhatti^1,2, Alok Chaturvedi²

¹Department of Chemistry, Pt. N.R.S. Govt. College, Rohtak, Haryana 

²Synthetic and Surface Science Laboratory, Department of Chemistry, S. P. C. Govt. College, Ajmer 305001, Rajasthan, India

*Corresponding Author E-mail: alok_chat.ajm@rediffmail.com

 

 

INTRODUCTION:

The synthesis of co-ordination compounds with sulphur containing ligands has been at the centre of interest in chemical research for many years^1-6. In recent time, the chemistry of trithiophosphate ligand is a fascinating area of intense study for inorganic chemists due to their bonding possibilities (monodentate, bidentate, chelating and bridging) and extensive applications in various fields, like agriculture^7-9, industries^10-11 and analytical studies^12-13.

 

The interest in transition metal complexes of trithiophosphate ligands stems from the fact that such complexes investigated for a number of biological applications viz. deoliants¹⁴, insecticides¹⁵, nematodicides¹⁶ and inhibitor of steel corrosion¹⁷.

 

Synthesizing and screening the antibacterial activity of various metal derivatives of trithiophosphates ligand have been reported in literature^18-22. Although a few O-alky/O-aryl trithiophosphate derivatives of main group metals^23-27 and transistion metals^28-31 have been studied in our laboratories, yet the chemistry of O-alky/O-aryl trithiophosphates of niobium(V) not explored.

 

Niobium pentachloride is used as lewis acid in organic synthesis. It is used as main precursor to alkoxide of niobium which uses in sol-gel processing. It is also the precursor to many laboratory reagents.

 

In the view of this it was considered worthwhile to synthesize O-alkyl /O-aryl trithiophosphate derivatives of Niobium (V), study their chemical bonding modes, antibacterial action and compare their antibacterial activities with standard drugs.

 

Expeimental:

During the experimental manipulations moisture was carefully excluded. O-alkyl/O-aryl trithiophosphoric acids have been synthesized by method reported in literature³². All the chemicals which we used during the investigation were of reagent grade. Carbon and hydrogen were estimated by colemen C, H and N analyzer. Sulphur was estimated by idometric method and Messenger's method³³. Molecular weights were determined by knauer vapour pressure osmometer in CHCl₃. FT IR spectra were recorded on perkin eimer spectrum version 10.400 spectrophotometer in the range of 4000-200 cm^-1. ¹H NMR and ³¹PNMR spectra were recorded in deutriated DMSO on DELTA NMR 400 MHz spectrophotometer using TMS (for ¹H).

 

Synthesis of ClNb[p-CH₃C₆H₅OP(S)SS]₂:

Solution of 1.0011gm (4.2392mmol) H₂S₃POC₆H₅-CH₃ in ethanol (approx.20mL) was added dropwise with constant stirring to 0.5726gm (2.1196mmol) in 15mL ethanol. The colour of reaction mixture changed from dark brown to yellow. The mixture was refluxed for 10-12 hours until the liberation of hydrochloride gas ceased. The product was isolated as pale yellow solid. The desired product was purified by washing several times with acetone and dried under vaccum.

 

All other derivatives were synthesized by similar method. The relevant synthetic and analytic data are given in table-1.

 

RESULTS AND DISCUSSION:

Reaction of niobiun pentachloride with O-alkyl/O-aryl trithiophosphoric acids have been carried out in 1:2 molar ratio, respectively in ethanol. All reactions are quite facile and completed by refluxing the reactants in ethanol for 10-12 hours.

 

 

(where R = Me, Et, Prⁱ, Buⁱ, Ph, CH₃-Ph)

Most of these derivatives are pale yellow colour powdery solids, soluble in co-ordinating solvents like DMSO, DMF etc. New derivatives are washed 3-4 times with acetone and recrystallized in ethanol and DMSO solvent. These derivatives could not be volatilized even under reduced pressure. Molecular weight determinations indicated the monomeric nature of these derivatives.

 

IR Spectra:

IR spectra of new derivatives have been measured in the range 4000-200cm^-1. Detail regarding the individual peak has been included in table-2. A comparison of IR spectra of new derivatives with those of starting materials shows the following characteristic changes:

1.   A new weak absorbtion band at (414.43-453.46 cm^-1) is observed, which is assigned to ʋNb-S linkage.

2.   Absence of absorbtion band in the region 2450-2550 cm^-1 indicates absence of S-H bond in the product.

3.   No absorbtion band appears at 1100-1200cm^-1 which suggests the absence of ʋP=O linkage in these derivatives.

4. Two strong intensity bands present in the region 1268.80-1396.51 cm^-1 and 991.94-1040.78cm^-1 have been assigned to ʋ(P)-O-C and ʋP-O-(C) vibrations, respectively.

5.   Band with medium intensity in the region 586.26-611.80 cm^-1 attributed to vibration of ʋP-S, asymmetric and symmetric.

6.   A sharp band present in the region 772.51-792.70 cm^-1 has been assigned to ʋP=S vibrations. Shifting of this band towards lower frequency indicates that this group is strongly chelated with central niobium atom.

 

Table 1: Synthetic and Analytic Data of ClNb[ROP(S)SS]₂

S. No.	Reactant  g.(mmol)		Product g.%.	Analysis % found (calcd.)				Molecular Weight found (calcd.)
	NbCl5	ROPS3H2 R=.		C	H	S	Nb
1.	0.8435 [3.1223]	CH3 1.0008 [6.2491]	ClNb[CH3OP(S)SS]2 1.1950          86.06	5.16 (5.39)	1.13 (1.35)	42.95 (43.25)	20.63 (20.89)	417.65 (444.71)
2.	0.7757 [2.8713]	C2H5 1.0010 [5.7479]	ClNb[C2H5OP(S)SS]2 1.2904         95.11	9.91 (10.15)	1.94 (2.11)	40.38 (40.69)	19.34 (19.65)
3.	0.7179 [2.6574]	iC3H7 1.0016 [5.3234]	ClNb[iC3H7OP(S)SS]2         1.2316          92.56	13.86 (14.38)	2.62 (2.80)	37.98 (38.42)	18.27 (18.55)	467.38 (500.71)
4.	0.6671 [2.4694]	iC4H9 1.0027 [4.9602]	ClNb[iC4H9OP(S)SS]2 1.2175          93.20	17.73 (18.16)	3.18 (3.40)	36.04 (36.38)	16.89 (17.57)
5.	0.6085 [2.2524]	C6H5 1.0006 [4.5041]	ClNb[C6H5OP(S)SS]2 1.1705          91.37	24.88 (25.32)	1.57 (1.76)	33.48 (33.82)	15.96 (16.34)	529.85 (568.71)
6.	0.5740 [2.1247]	o-CH3C6H4 1.0035 [4.2494]	ClNb[o-CH3C6H4OP(S)SS]2 1.2067          95.21	27.79 (28.15)	1.99 (2.35)	31.75 (32.24)	14.93 (15.57)
7.	0.5725 [2.1192]	m-CH3C6H4 1.0009 [4.2321]	ClNb[m-CH3C6H4OP(S)SS]2        1.1495           90.92	27.84 (28.15)	2.06 (2.35)	31.97 (32.24)	15.09 (15.57)
8.	0.5726 [2.1196]	p-CH3C6H4 1.0011 [4.2392]	ClNb[p-CH3C6H4OP(S)SS]2        1.1987           94.78	27.90 (28.15)	2.17 (2.35)	31.85 (32.24)	15.19 (15.57)	561.97       (596.71)

 

Table 2: IR spectra data of ClNb[ROP(S)SS]₂

S.No.	COMPOUND	ʋ(P)-O-C	ʋP-O-(C)	ʋP=S	ʋP-S	ʋNb-S	ʋNb-Cl
1.	ClNb[CH3OP(S)SS]2	1391.46w	1032.43vs	781.21w	606.08s	426.36w	677.70w
2.	ClNb[C2H5OP(S)SS]2	1385.56s	1033.49vs	779.13s	609.57s	427.89w	679.05w
3.	ClNb[iC3H7OP(S)SS]2	1378.67s	1037.83vs	780.93s	611.80s	429.90w	676.99s
4.	ClNb[iC4H9OP(S)SS]2	1291.60w	995.32vs	776.51w	590.48s	414.43s	680.54w
5.	ClNb[C6H5OP(S)SS]2	1268.80w	991.94vs	773.67s	589.62s	421.63s	673.03s
6.	ClNb[o-CH3C6H4OP(S)SS]2	1396.51s	1040.78vs	792.70w	595.41s	429.91w	684.31w
7.	ClNb[m-CH3C6H4OP(S)SS]2	1278.10s	994.57vs	772.51vs	604.59s	437.36w	687.55s
8.	ClNb[p-CH3C6H4OP(S)SS]2	1386.98s	1003.46vs	781.58s	586.26s	453.46s	688.76s

Vs = very strong, s = strong, w = weak

 

NMR spectra:

¹H NMR spectra: The PMR spectra of monochloro-niobium(V) bis-O-alkyl/O-aryl trithiophosphates, ClNb[ROP(S)SS]₂ recorded in deutriated DMSO in 0-10 ppm region. Characteristics signals of these derivatives are listed in Table -3. It shows the expected³⁴ peaks due to corresponding alkoxy and phenyl protons. The singlet peak at (3.1-3.5ppm) assigned to SH protons in O-alkyl/O-aryl trithiophosphoric acid is absent in the spectra of chloro-niobium derivatives, indicating deprotonation of SH group on forming Nb-S bond.

 

³¹P NMR spectra: ³¹P NMR spectra of newly synthesized derivatives have been scanned in deutriated DMSO and spectral data are summarized in Table-3. Presence of only one type of phosphorus nucleus in these derivatives has been confirmed by only one resonance signal in ³¹P NMR spectra in the region 89.90-108.19ppm. On comparing these values with the parent compound, a downfield shift of 20-30 ppm is observed. This unexpected downfield shift indicates the formation of Nb-S-P bond in these derivatives.

 

Table 3: ¹H NMR spectra and ³¹P NMR spectra of ClNb[ROP(S)SS]₂

S. No.	Compound	1H chemical shift (ppm)	31P Chemical shift (ppm)
1.	ClNb[CH3OP(S)SS]2	2.61, s, 6H (OCH3)	101.83
2.	ClNb[C2H5OP(S)SS]2	1.84, t, 6H (CH3) 3.21, q, 4H (OCH2)	98.79
3.	ClNb[iC3H7OP(S)SS]2	1.15, d, 12H (CH3) 2.85-3.38, m, 2H (OCH)	94.65
4.	ClNb[iC4H9OP(S)SS]2	1.29, d, 12H (CH3) 2.28-2.37, m, 2H (CH) 3.43, d, 4H (OCH2)	89.90
5.	ClNb[C6H5OP(S)SS]2	6.63-6.95, m, 10(C6H5)	108.19
6.	ClNb[o-CH3C6H4OP(S)SS]2	6.94-7.37, m, 8H(C6H4) 2.46, s, 6H (CH3)	99.42
7.	ClNb[m-CH3C6H4OP(S)SS]2	6.79-7.26, m, 8H(C6H4) 2.35, s, 6H (CH3)	94.70
8.	ClNb[p-CH3C6H4OP(S)SS]2	6.57-6.91, m, 8H (C6H4) 2.12, s, 6H (CH3)	92.45

 

Antibacterial activity:

All newly synthesized derivatives and free ligand studied were tested on gram positive and gram negative bacteria. The antibacterial activity was carried out by paper disc method. The zone of inhibition was measured in mm. DMSO was used as solvent. The compounds were tested at 100 µg/mL concentration. The results show that the activity is enhanced on co-ordination. Compound-17 show maximum activity against E. Coli, while compound-12 exhibit minimum against it. Against Staphylococcus aureus, maximum activity is exhibited by compound-13 and minimum by compound-14.

 

Effect of ClNb [p-CH₃C₆H₄OP(S)SS]₂ on gram positive and gram negative bacteria

.                                  

Effect on gram positive bacteria

Effect on gram negative bacteria

1.Solvent 2-NbCl₅ 3- Ligand 4- ClNb [p-CH₃C₆H₄OP(S)SS]₂

 

Effect of ClNb[ⁱC₄H₉OP(S)SS]₂ on gram positive and gram negative bacteria

.                              

Effect on gram positive bacteria

Effect on gram negative bacteria

1-Solvent 2-NbCl₅ 3- Ligand 4- ClNb[ⁱC₄H₉OP(S)SS]₂

 

Table 4: Antibacterial activity Niobium (V) derivatives of the type ClNb [ROP(S)SS]₂

Sr. No.	Compound	Gram positive bacteria zone of inhibition in mm	Gram negative bacteria zone of inhibition in mm
1.	Solvent	0	0
2.	CH3OPS(S)(SH)2	9	6
3.	C2H5OPS(S)(SH)2	7	5
4.	iPrOP(S)(SH)2	10	4
5.	iBuOP(S)(SH)2	6	8
6.	PhOP(S)(SH)2	10	12
7.	o-CH3 PhOP(S)(SH)2	12	14
8.	m-CH3 PhOP(S)(SH)2	11	13
9.	p-CH3 PhOP(S)(SH)2	9	10
10.	ClNb[CH3OP(S)SS]2	31	16
11.	ClNb[C2H5OP(S)SS]2	33	19
12.	ClNb[iC3H7OP(S)SS]2	28	14
13.	ClNb[iC4H9OP(S)SS]2	37	18
14.	ClNb[C6H5OP(S)SS]2	15	32
15.	ClNb[o-CH3C6H4OP(S)SS]2	21	38
16.	ClNb[m-CH3C6H4OP(S)SS]2	18	40
17.	ClNb [p-CH3C6H4OP(S)SS]2	22	43
18.	Imipenem	12	30
19.	Linezolid	8	10

 

CONCLUSION:

With the help of physico-chemical spectroscopic studies IR and NMR (¹H, ¹³C, ³¹P) following structure may be proposed for the newly synthesized derivatives. Considering the bidentate and chelating mode of bonding of trithiophosphate moiety with metal, we conclude that metal atom in the monochloro-niobium(V) bis-O-alkyl/O-aryl trithiophosphates is five-coordinated.

 

ACKNOWLEDGEMENT:

One of the authors (Suman Bhatti) is thankful to M.N.I.T Jaipur for spectral analysis.

 

REFERENCES:

1.      G.V. Dave and P.J. Vyas; Journal of Current Chemical &Pharmaceutical Sciences.; 2, 133-148 (2012).

2.      A.L. Bingham, J.E. Drake, M.B. Hursthouse, M.E. Light, M. Nirwan and R. Ratnani; Polyhedron.; 26, 2672-2678 (2007).

3.      S. Maheshwari, J.E. Drake, K. Kori, M.E. Light and R. Ratnani; Polyhedron; 28, 689-694 (2009).

4.      A.A. El Khaldy, A.R. Hussien, A.M. Abushanab and M.A. Wasse; Phosphorus Sulfur and Silicon Relat. Elem.; 186,589-597, (2011).

5.      A.M. Cotero-Villegas, R.A. Toscano and M. Munoz; Journal of Organometallic Chemistry; 690, 2872-2879 (2005).

6.      N. Ma, Y. Li, H. Xu, Z. Wang, and X. Zhang; Journal of the American Chemical Society;132, 442-443 (2010).

7.      A. Mihailovski, US Pat. Chem. Abstr.; 88b (1978).

8.      J. Kanazawa, H. Kubo and R. Sato; Agric. Biol. Chem.; 29, 43 (1965).

9.      A. Kumar, S. Kour, M.S. Hundal and S.K. Pandey; J. Chem. Crystallogr.; 42, 299 (2012).

10.   H.H. Farmer, B.W. Malone and H.F. Tompkins; Lubric(Eng.); 23, 57 (1967).

11.   M.C. Gupta, K. Sankhala and A. Chaturvedi; J. Iranian Chem. Res.; 4, 223 (2012).

12.   K. Hayashi, Y. Sasaki, S. Tagashira, Y. Soma and S. Kato; Anal Sci.; 105 (1986).

13.   M.C. Gupta, K. Sankhala and A. Chaturvedi; Res. J. of Pharmaceutical, Biological and Chem. Sciences; 3, 223 (2012).

14.   B.P. Singh, G. Srivastava and R.C. Mehrotra; Inorg. Chem. Acta.; 161, 253 (1989).

15.   B. Stristveen, B.L. Fesinga and R.; Tetrahedron; 43(1), 123 (1987).

16.   K. Sankhala and A. Chaturvedi; I.J. Chem. Tech. Res.; 4, 1329 (2012).

17.   A.K. Kjalafavah, M.E. Hassan and N.S. Soleman; J. Ind. Chem. Soc..; 69, 318 (1992).

18.   S. Shahzad, K. Shafrid, S. Ai.M. Mazhar and K.M. Khan, J. Iran. Chem. Soc., 2(4), 277-288 (2005).

19.   U.N. Tripathi, A. Siddiqui, Mohd. Safi, Nitya Sharma and Neetu Shrivastava; Phosphorus Sulfur and Silicon; 185, 1993, (2010).

20.   A. Chaturvedi, C. Sharma and P.N. Nagar; Phosphorus Sulfur and Silicon; 178(9), 1923 (2003).

21.   U.N. Tripathi and D.K. Sharma; Phosphorus Sulfur and Silicon; 180, 1559 (2005).

22.   U.N. Tripathi, Mohd. Ahmad; Phosphorus Sulfur and Silicon; 179(11), 2307 (2004).

23.   A. Chaturvedi and L. Chordia, Phosphorous, Sulfur and Silicon, 182, 2821 (2007).

24.   A. Chaturvedi and L. Chordia, Main Group Met. Chem. 31(6), 319(2007).

25.   A. Chaturvedi, Kiran Sankhla; Res. J. of Chem. Sci.; 2(5), 57(2012).

26.   A. Chaturvedi and Kiran Sankhla; Phosphorus Sulfur and Silicon; 187, 1236 (2012).

27.   A. Chaturvedi, Kiran Sankhla; Phosphorus Sulfur and Silicon; 188, 1427(2013).

28.   A. Chaturvedi, Bharti Chaturvedi; International Journal of Recent Scientific Research; 8(9), 20235-20237(2017).

29.   A. Chaturvedi, Mahendra Kumar Rana; International Journal of Recent Scientific Research; 8(9), 19894-19896(2017).

30.   A. Chaturvedi, Kamiya Mundra; International Journal of Innovative Research in Science, Engineering and Technology; 7(1), 546-551(2018).

31.   A. Chaturvedi, Suman Bhatti; International Journal of Recent Research Aspects; 4(3), 183-187(2017).

32.   B.P. Kotavich, N.I. Zemlyanskii, I.V. Mwzavev and M.P. Volosin; Zn. Obsch. Khim; 38(6), 1282(1968).

33.   A.I. Vogel, "A Text Book of Quantitative Inorganic Analysis" Longman E.L.B.S. IV Edition (1973).

34.   R.M. Silverstein, F.X. Webster "Spectrometric Identification of Organic Compounds" 6^th edition, John Wiley & Sons Inc., New York, (1998).

 

Received on 05.12.2019                    Modified on 10.01.2020

Accepted on 31.01.2020                   ©AJRC All right reserved