Ligand substitution can significantly affect the color and magnetic properties of coordination compounds. This is because the nature of the ligand can influence the electronic structure and energy levels of the metal ion in the complex. Here's an explanation and examples to illustrate this:1. Color: The color of coordination compounds is primarily due to the absorption of light by the metal-to-ligand charge transfer MLCT or ligand-to-metal charge transfer LMCT transitions, which involve the movement of electrons between the metal ion and the ligand. When a ligand is substituted by another ligand, the energy gap between the ground and excited states of the complex may change, leading to a change in the wavelength of light absorbed and, consequently, the color of the compound.Example: The color of the hexaaquacopper II complex [Cu H2O 6]2+ is pale blue due to the MLCT transition. However, when ammonia ligands replace the water ligands to form the tetraamminecopper II complex [Cu NH3 4]2+, the color changes to deep blue. This is because the ammonia ligands cause a change in the energy levels of the complex, leading to a different MLCT transition and a change in the color.2. Magnetic properties: The magnetic properties of coordination compounds depend on the number of unpaired electrons in the metal ion. Ligand substitution can affect the magnetic properties by changing the metal's oxidation state or by altering the ligand field strength, which can influence the splitting of the metal ion's d-orbitals and the distribution of its electrons.Example: The octahedral complex [Fe H2O 6]2+ has five unpaired electrons in its high-spin state, making it paramagnetic. However, when the water ligands are replaced by stronger-field cyanide ligands to form [Fe CN 6]4-, the complex becomes low-spin, with all six electrons paired up in the lower-energy t2g orbitals. As a result, the [Fe CN 6]4- complex is diamagnetic, with no unpaired electrons.In summary, ligand substitution can significantly affect the color and magnetic properties of coordination compounds by altering the electronic structure and energy levels of the metal ion. The specific effects will depend on the nature of the ligands involved and the geometry of the complex.