Comparing Nickel Complexes: A UV-Vis Spectra Study on Solvent Effects and Absorbance Differences

The difference in absorbance between Ni(SCN)2(PPh3)2 and Ni(NO3)2(PPh3)2 might be due to several factors: 1. Solvent used: The solvent can play a significant role in determining the absorbance of a solution. Solvents can affect the extinction coefficients of the compounds, which directly affects their absorbance. In this case, acetonitrile and nitromethane were used for Ni(SCN)2(PPh3)2 and Ni(NO3)2(PPh3)2 respectively. Nitromethane is more polar than acetonitrile, which may make it easier for the nitrate compound to absorb light, leading to a higher absorbance value. 2. Concentration: The concentration of the solution can also affect absorbance. According to the Beer-Lambert Law, absorbance is directly proportional to concentration. The concentration used for Ni(NO3)2(PPh3)2 was five times higher than for Ni(SCN)2(PPh3)2, which would naturally lead to a higher absorbance, all other things being equal. 3. Chemical Structure: Lastly, the different chemical structures of Ni(SCN)2(PPh3)2 and Ni(NO3)2(PPh3)2 can lead to differences in absorbance. Different compounds can absorb light differently depending on their electronic configurations and the types of transitions that are possible. The nitrate ion in Ni(NO3)2(PPh3)2 may facilitate more or different types of electronic transitions compared to the thiocyanate ion in Ni(SCN)2(PPh3)2, leading to higher absorbance. It's also worth noting that the yield of synthesized product can affect your results. However, in your case, since you've obtained higher percentage yield for Ni(NO3)2(PPh3)2, it further validates the higher absorbance in UV-Vis Spectra. Lastly, any impurities or byproducts in the synthesized product could also affect the UV-Vis spectra and alter the absorbance values. Always ensure that your synthesis process is optimized to minimize the presence of these.