**5.5 Thermal measurements**

A plot of change in weight vs. temperature or time is known as Thermo gravimetric curve. It records the loss in weight as a function of temperature for transition that involves dehydration or decomposition. The TGA studies of the complexes was recorded in nitrogen atmosphere on Rigaku Thermo Plus-8120 instrument by increasing the temperature from room temperature upto 900°C at the heating rate of 10°C min<sup>−</sup><sup>1</sup> . The decomposition pattern obtained for VO(II) complexes of chalcone ligands follow two major stages (**Figure 4**). The thermal dehydration of this complex in the first stage was attributed to the loss of water leaving behind the nonhydrated complex takes place between 80 and 120°C. In the second stage the complex starts decomposing gradually which occurs in the temperature range corresponds to 220–310°C, this range correspond to the decomposition of part of chalcone ligand and the observed mass loss was recorded as 29.81% for VL1, 32.41% for VL2, 38.78%


**77**

**Table 6.**

*Thermal data for vanadium metal complexes.*

**Figure 4.**

*Thermogravimetry spectra of V(IV) complexes.*

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

for VL3 and 36.90% for VL4 complex, which shows that at least unstable intermediate are also formed during this degradation stage. The third stage was decomposition of complete chalcone ligand in temperature range of 550–700°C. The overall total mass loss up to 700°C is around 88–90% which shows finally formation of VO. The residue left after 700°C is around 9–11% which resemble the theoretical values. Hence from thermal analysis it is clear that the complexes under study contains two water molecules for VL1, VL3 and VL4 complex and three water molecules for VL2 complex

**Complex Temperature range (°C) % Weight loss Decomposition product**

VL1 80–110 5.90 5.95 2H2O

VL2 85–110 8.30 8.24 3H2O

VL3 80–115 5.12 5.17 2H2O

VL4 90–120 5.27 5.34 2H2O

**Found Calculated**

235–290 29.81 29.75 C14H12 550–680 53.26 53.20 C20H18O4 700–780 11.03 11.07 VO

230–300 32.41 32.36 C14H12O2 570–660 49.09 49.16 C20H18O4 700–750 10.16 10.22 VO

240–310 38.78 38.85 C14H10O4N2 580–700 46.41 46.33 C20H18O4 720–780 9.70 9.64 VO

220–290 36.90 36.94 C14H10Cl2 550–660 47.85 47.77 C20H18O4 710–760 9.95 9.94 VO

which are present in the ionic sphere of the complex (**Table 6**).

**Table 5.** *ESR spectral data of vanadium(IV) metal complexes.*

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

*Stability and Applications of Coordination Compounds*

**5.3 Magnetic susceptibility measurement**

electronic absorption spectra.

**5.4 Electron spin resonance study**

orbital split into different level, dx2

**5.5 Thermal measurements**

10°C min<sup>−</sup><sup>1</sup>

The magnetic susceptibility for all the Vanadium complexes at room temperature were recorded by the Gouy's method using Hg[Co(SCN)4] as a calibrant and reported in **Table 4**. The effective magnetic moments were calculated after applying diamagnetic corrections for the ligand components using Pascal's constants. The room temperature μeff values for the vanadium complexes were found in the range 1.71–1.76 B.M. The magnetic susceptibilities of the complexes are consistent with square pyramidal geometry around the central metal ion [27, 28]. The magnetic moments of the compounds investigated are in agreement with the findings of

ESR spectrum of VO(II) complexes was recorded at room temperature as polycrystalline sample, on *x*-band at 9.1 GHz, under the magnetic field strength 3000 G using TCNE as marker. The value of g|| and g┴ is shown in **Table 5**. Paramagnetism of vanadyl ion arises from the single unpaired electron, its paramagnetism is due to spin angular momentum and VO2+is most stable diatomic cation. In V(IV) complexes value of g is below value of free electron. The trend 2.0023 > g┴ > g||, observed for the complexes. The EPR signal are split into eight lines suggested that V(IV) complexes

of strong multiple covalent vanadium oxo-bond, a tetragonal compression occurs and therefore square pyramidal geometry proposed for VO(II) complex. The d

in dxy orbital. As G values of present complexes are lower than four indicates, the

A plot of change in weight vs. temperature or time is known as Thermo gravimetric curve. It records the loss in weight as a function of temperature for transition that involves dehydration or decomposition. The TGA studies of the complexes was recorded in nitrogen atmosphere on Rigaku Thermo Plus-8120 instrument by increasing the temperature from room temperature upto 900°C at the heating rate of

ligands follow two major stages (**Figure 4**). The thermal dehydration of this complex in the first stage was attributed to the loss of water leaving behind the nonhydrated complex takes place between 80 and 120°C. In the second stage the complex starts decomposing gradually which occurs in the temperature range corresponds to 220–310°C, this range correspond to the decomposition of part of chalcone ligand and the observed mass loss was recorded as 29.81% for VL1, 32.41% for VL2, 38.78%

**Complex g|| g┴ gav G axial symmetry parameter**

VL1 1.981 1.986 1.984 1.31 VL2 1.958 1.983 1.975 2.29 VL3 1.973 1.987 1.982 1.91 VL4 1.949 1.987 1.974 3.48

. The decomposition pattern obtained for VO(II) complexes of chalcone

system. Because

electron lies

orbital is least stable as it is face to face with

are mononuclear [29]. The oxovanadium(IV) ion belong to the 3d1


all four equatorial ligands. dxy being most stabilized orbital therefore d1

ligands involve in the complex formation are the strong field ligands.

**76**

**Table 5.**

*ESR spectral data of vanadium(IV) metal complexes.*

for VL3 and 36.90% for VL4 complex, which shows that at least unstable intermediate are also formed during this degradation stage. The third stage was decomposition of complete chalcone ligand in temperature range of 550–700°C. The overall total mass loss up to 700°C is around 88–90% which shows finally formation of VO. The residue left after 700°C is around 9–11% which resemble the theoretical values. Hence from thermal analysis it is clear that the complexes under study contains two water molecules for VL1, VL3 and VL4 complex and three water molecules for VL2 complex which are present in the ionic sphere of the complex (**Table 6**).



#### **Table 6.**

*Thermal data for vanadium metal complexes.*


**Table 7.**

*Antibacterial and antifungal activities (inhibition zone of bacterial growth, mm) of the ligand and metal complexes.*
