**Abstract**

The vanadyl(IV) complexes of substituted chalcones were prepared by refluxing vanadyl sulphate with different substituted chalcones in ethanoic medium. The chalcones were prepared with different aromatic aldehydes like benzaldehyde, hydroxy benzaldehyde, nitro benzaldehyde and chloro benzaldehyde. The synthesized Vanadium complexes were characterized by different spectral techniques. The IR spectral studies revealed that the chalcone derivatives are bidentate ligand. Magnetic studies, electron spin resonance and UV studies suggest that the complexes are in square pyramidal geometry. Conductance measurements suggest that all complexes are non-electrolyte in DMF. The thermal study explained the stability of complex and its decomposition. The synthesized ligand and metal complexes were screened for their antibacterial activity against *E. coli* and *Staphylococcus aureus* bacterial strains and for antifungal activity against *P. notatum*.

**Keywords:** vanadyl sulphate, chalcone ligands, complexes, spectral studies, TGA, magnetic study, antifungal and antibacterial study

### **1. Introduction**

Chemically chalcones consist of open chain flavonoids in which the two aromatic ring joined by a three carbon. Chalcones are *α*, *β*-unsaturated ketones and contain a reactive keto-ethylenic group 2-hydroxychalcones and their heterocyclic analogues are also reported to form coordination complexes.

Chalcones are widely distributed in fruits, vegetables, tea, spices and also have applications in biological activities. These are abundant in edible plants and are considered to be the precursors of flavonoids and isoflavonoids [1]. Some chalcones has been employed for the gravimetric estimation of divalent ions of palladium, copper and nickel. Calcium determination by complexometric titration by using chalcone-metanil as indicator also has been reported. Chalcones possesses several biological activities with wide ranging. Chalcones use for the treatment of chronic diseases which involve inflammatory processes, for example, diabetes mellitus [2]. The study of chalcone derivatives has become of much interest in recent years on account of their antibacterial, antiviral activities [3]. Many chalcones based have been recognized in a number of screening assays for modulating important pathways or molecular targets in cancer [4, 5].

The coordination chemistry of oxovanadium(IV) (i.e. VO2+ or vanadyl ion) is more interesting and rather more important because of two main reasons. Firstly, the vanadyl complexes are finding more and more importance in biological systems. Secondly, the coordination number and geometry of this metal is highly ligand

dependent. Moreover vanadyl ion is less toxic. In last year's research has been directed towards the synthesis of efficient bioactive compounds with low toxicity, in order to achieve this goal the type and the position of substituent into ligand were varied [6].

A wide variety of oxovanaduim(IV) complexes have been prepared and characterized by various physicochemical methods. Oxovanadium(IV) complexes have a square pyramidal geometry with apical oxygen and the vanadium atom lying above the plane defined by the donor atoms of the equatorial ligands. These square pyramidal complexes generally exhibit strong tendency to remain five coordinate [7, 8]. The coordination chemistry of vanadium(V) compounds is dominated by oxo complexes, containing the VO3+ or the VO2+ moiety [9]. The absorption band due to V〓O stretching vibration of oxovanadium(IV) complexes is usually observed at a higher wavenumber compared to those of vanadate(V) complexes. However, the V〓O stretching vibration is susceptible to a number of influences including electron donation from basal plane ligand atoms, solid-state effects, and coordination of additional molecules. Therefore, there has been considerable work done to assign the V〓O stretching frequencies in oxovanadium(IV) compounds [10].

An increasing research interest of vanadium in coordination chemistry is not only due to its exhibiting a range of oxidation dates from +5 to −1 but also complexities exhibited by vanadium complexes and their industrial [11, 12], biological [13, 14] and medicinal [15, 16] applications. Vanadium complexes have been reported to have interesting antibacterial activities [17–20]. It has been reported that V(IV) complexes high effect on anticancer activity [21].

#### **2. Preparation of substituted chalcone**

The substituted chalcones prepared by stirring the equimolar concentration mixture of 2-hydroxy-4,5-dimethyl acetophenone (0.01 mol) and substituted aromatic benzaldehyde (0.01 mol) in 20 ml ethanol for 1 h in presence of 50% NaOH. The mixture stirred till completion of the reaction (progress of reaction checked by TLC). The crude mixture poured into ice water then acidified the product with 10% hydrochloric acid. The coloured compound formed was filtered, washed with water and dried. The compounds recrystallized from absolute ethanol (**Figure 1**).

**Figure 1.** *Reaction scheme for chalcones (R* 〓 *H, 4-OH, 4-NO2 and 3-chloro).*

#### **3. Preparation of complexes**

To a hot suspension of ligand (0.02 M) in ethanol, ethanolic solution (0.01 M) of the metal salt vanadyl sulphate (VOSO4) was added drop wise with constant stirring and refluxed for 2–3 h. The resulting reaction mixture was cooled to room temperature and maintained up to pH 8.0 by adding ammonia then refluxed further for 30 min. The resultant product was filtered through Whatman filter paper no. 1 and repeatedly washed with ethanol until the washing were free from the excess of ligand. These complexes were finally dried under vacuum in desiccator over fused CaCl2.

**73**

**Table 1.**

*Stability of Vanadium Chalcone Complexes DOI: http://dx.doi.org/10.5772/intechopen.88072*

KBr pallets in the range of 4000–400 cm<sup>−</sup><sup>1</sup>

8120 TG-DTA instrument with a heating rate 10°C min<sup>−</sup><sup>1</sup>

concentration are in the range of 15–27 mhos.cm 2

plexes have been scanned in the 4000–400 cm<sup>−</sup><sup>1</sup>

**Mol wt.**

The complexes shows a band in the region 1162–1205 cm<sup>−</sup><sup>1</sup>

**Yield %**

The IR spectra of complexes were recorded on a Perkin-Elmer instrument in

carried out in nitrogen atmosphere in the range 25–900°C on Rigaku Thermo Plus-

dard. UV-Visible spectra were recorded using DMF as solvent on Shimadzu UV-VIS spectrophotometer in the range 250–950 nm. Electron spin resonance spectra complexes were recorded on E-112 ESR Spectrometer as '*g*' marker ( *g* = 2.00277) at room temperature. The conductance was measured in DMF solvent on Equiptronics

All the vanadium chalcone complexes are insoluble in water and most common organic solvents but sparingly soluble in DMF. The complexes are stable at room temperature. The elemental analysis shown in **Table 1** indicates that, all metal complexes have 1:2 (metal: ligand) stoichiometry for all the complexes (**Figure 2**).

VL1: R1〓H & R2〓H; VL2: R1〓H & R2〓OH

VL3: R1〓H & R2〓 NO2 and VL4: R1〓Cl & R2〓H

All synthesized complexes are green in colour. All complexes are decomposed above 300°C. The molar conductance values obtained for these complexes at the

Some structurally significant IR bands for uncoordinated chalcones and com-

V L1 C34H30O5V 569 62 9.10 71.52 5.15 — — 14.13 18.21

V L2 C34H30O7V 601 59 8.55 67.94 4.91 — — 18.58 23.46

VL3 C34H28N2O9V 659 65 7.68 61.93 4.22 4.28 — 21.88 15.62

mol<sup>−</sup><sup>1</sup>

**M C H N Cl O**

(8.96) (71.70) (5.27) (14.06)

(8.48) (67.88) (4.99) (18.63)

(7.74) (61.91) (4.25) (4.25) (21.85)

638 56 8.05 63.88 4.35 — 11.13 12.58 26.33 (7.99) (63.95) (4.39) (11.1) (12.54)

suggesting their non-

region and presented in **Table 2**.

**% Elemental analysis found (calculated) Molar** 

which corresponds to

**conductance mhos.cm 2 mol<sup>−</sup><sup>1</sup>**

. TGA analysis of metal complexes were

using Alumina as a stan-

**4. Instrumental methods**

Conductivity meter (EQ-664A).

**5. Results and discussion**

electrolytic nature [22].

**5.1 IR spectral studies**

**Complex Empirical** 

V L4 C34H28O5Cl

V

*Physical and analytical data of metal complexes.*

**formula**
