**5. Results and discussion**

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**).

$$\mathsf{VL}\_1; \mathsf{R}\_1 \sqsubseteq \mathsf{H} \& \mathsf{R}\_2 \sqsubseteq \mathsf{H}; \mathsf{VL}\_2; \mathsf{R}\_1 \sqsubseteq \mathsf{H} \& \mathsf{R}\_2 \sqsubseteq \mathsf{OH}.$$

$$\mathsf{VL}\_3 \colon \mathsf{R}\_1 \sqcap \mathsf{H} \otimes \mathsf{R}\_2 \sqcap \mathsf{NO}\_2 \text{ and } \mathsf{VL}\_4 \colon \mathsf{R}\_1 \sqcap \mathsf{Cl} \otimes \mathsf{R}\_2 \sqsubseteq \mathsf{H}$$

All synthesized complexes are green in colour. All complexes are decomposed above 300°C. The molar conductance values obtained for these complexes at the concentration are in the range of 15–27 mhos.cm 2 mol<sup>−</sup><sup>1</sup> suggesting their nonelectrolytic nature [22].

## **5.1 IR spectral studies**

Some structurally significant IR bands for uncoordinated chalcones and complexes have been scanned in the 4000–400 cm<sup>−</sup><sup>1</sup> region and presented in **Table 2**. The complexes shows a band in the region 1162–1205 cm<sup>−</sup><sup>1</sup> which corresponds to


**Table 1.**

*Physical and analytical data of metal complexes.*

strong band in the region 1185–1221 in free ligand of chalcones due to *υ* (C—O). The shifts of this band were observed to move to lower wave numbers indicates bonding of phenolic oxygen atom to metal center via deprotonation. The band in the region 552–573 cm<sup>−</sup><sup>1</sup> can be assigned to the stretching modes of the metal to ligand bonds, *ν* (V—O) [23]. In addition the compound exhibit a strong band in the 952–983 cm<sup>−</sup><sup>1</sup> range due to the terminal V〓O stretching and this value is close to the majority of oxovanadium(IV) complexes [24]. In the IR spectra of all the ligands an intense band appearing around 1640 cm<sup>−</sup><sup>1</sup> is attributed [25] to (C〓O) group. In the complexes this band is observed in the 1618–1626 cm<sup>−</sup><sup>1</sup> range. The shifting of band to lower wave number indicates coordination through oxygen of (C〓O) group. The band appears around 740 cm<sup>−</sup><sup>1</sup> in chloro complex indicating presence of C—Cl bond. The occurrence of band around 1500 cm<sup>−</sup><sup>1</sup> in VL3 complex is due to *ν* (C—NO2) mode.

#### **Figure 2.**

*Structure of vanadium complex.*


**75**

**Table 4.**

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

Electronic absorption spectral study is an important tool used [26] to determine the geometry around a central metal atom. The electronic spectra (**Figure 3**) of the metal complexes in DMF (10**<sup>−</sup><sup>3</sup>** M) were recorded on Shimadzu UV-VIS spectrophotometer in the range 200–950 nm. The Vanadium chalcone complexes show absorption band in 380–770 nm region (**Table 5**). Most of the VO(II) complexes are green in colour. The electronic absorption spectra of VO(II) complexes showed three bands at 13,015–13,305, 17,455–17,632 and 25,755–25,930 cm<sup>−</sup><sup>1</sup>

B1 (dxy → dx<sup>2</sup>

respectively. From these electronic absorption bands and paramagnetic nature, square pyramidal geometry suggested for VO(II) chalcone complexes. As these

in the metal ion so B0 value of V4+ is not available. Therefore calculation of Racah

B2 → <sup>2</sup>

parameter is not possible for these vanadium complexes (**Table 3**).

**Complexes (***v***1) (***v***2) (***v***3) Dq (cm<sup>−</sup><sup>1</sup>**

**Complex Magnetic moment (B.M.)**

VL1 1.73 VL2 1.71 VL3 1.76 VL4 1.72

*Magnetic moment values of the vanadium (IV) chalcone complexes.*

VL1 13,275 17,455 25,810 1745 −83.50 VL2 13,305 17,585 25,930 1758 −84.12 VL3 13,015 17,632 25,755 1763 −84.36 VL4 13,135 17,490 25,890 1749 −83.69

representing 10 Dq. These bands are assigned to the transitions


system, there is no interelectronic repulsion

, with

2 )

B2 → [2]A1 (dxy → dz

**) CFSE (KJ/mol)**

**5.2 Electronic spectra**

17,455–17,632 cm<sup>−</sup><sup>1</sup>

B2 → [2]E(dxy → dxz,dyz),<sup>2</sup>

oxovanadium(IV) belong to the 3d1

2

**Figure 3.**

**Table 3.**

*Electronic spectra of V(IV) complexes.*

*Electronic spectral data for vanadium metal complexes.*

**Table 2.** *Important IR spectral bands (cm<sup>−</sup><sup>1</sup> ) of the complexes.*
