Geometrical isomerism and optical isomerism are two types of stereoisomerism found in coordination compounds. They differ in the arrangement of ligands around the central metal ion.1. Geometrical isomerism: This type of isomerism arises due to the different possible arrangements of ligands around the central metal ion in a coordination compound. It is commonly observed in complexes with coordination numbers 4 and 6. In a square planar complex coordination number 4 , cis and trans isomers can be formed, while in an octahedral complex coordination number 6 , cis, trans, fac, and mer isomers can be formed.2. Optical isomerism: Optical isomers are non-superimposable mirror images of each other, also known as enantiomers. They have the ability to rotate plane-polarized light in opposite directions. Optical isomerism is commonly observed in octahedral complexes with chiral ligands or when the arrangement of ligands around the central metal ion is asymmetric.To identify geometrical and optical isomers using spectroscopic methods, you can use the following techniques:1. Ultraviolet-visible UV-Vis spectroscopy: Geometrical isomers often have different absorption spectra due to differences in ligand arrangement, which can affect the energy levels of the d-orbitals in the central metal ion. By comparing the absorption spectra of different isomers, you can identify the type of geometrical isomerism present.2. Circular dichroism CD spectroscopy: This technique measures the difference in absorption of left and right circularly polarized light by a sample. Optical isomers will exhibit a characteristic CD spectrum, with one enantiomer showing a positive Cotton effect and the other showing a negative Cotton effect at the same wavelength. By analyzing the CD spectrum, you can determine the presence of optical isomers in a coordination compound.3. Nuclear magnetic resonance NMR spectroscopy: NMR can provide information about the chemical environment of ligands in a coordination compound. Geometrical isomers may have different chemical shifts for their ligands, allowing you to distinguish between them. In the case of optical isomers, the use of chiral solvents or chiral derivatizing agents can help differentiate between enantiomers based on their NMR spectra.4. Vibrational spectroscopy IR and Raman : Geometrical isomers may exhibit different vibrational frequencies due to differences in bond lengths and angles. By comparing the IR and Raman spectra of different isomers, you can identify the type of geometrical isomerism present. Optical isomers may also show differences in vibrational spectra, but this is less common and may require more advanced techniques, such as vibrational circular dichroism VCD spectroscopy.In summary, geometrical isomerism and optical isomerism in coordination compounds refer to different arrangements of ligands around the central metal ion. Spectroscopic methods such as UV-Vis, CD, NMR, and vibrational spectroscopy can be used to identify and differentiate between these isomers.