The strength of the ligand in a coordination complex has a significant impact on the crystal field splitting energy . Crystal field splitting energy refers to the energy difference between the d-orbitals of a transition metal ion in a coordination complex. The ligand's strength influences the extent to which the d-orbitals are split, which in turn affects the complex's properties, such as its color, magnetic behavior, and stability.Ligands can be classified based on their ability to split the d-orbitals, known as the spectrochemical series. The series, in increasing order of ligand strength, is as follows:I- < Br- < S2- < SCN- < Cl- < NO3- < N3- < F- < OH- < C2O4^2- < H2O < NCS- < CH3CN < py pyridine < NH3 < en ethylenediamine < bipy 2,2'-bipyridine < phen 1,10-phenanthroline < NO2- < PPh3 < CN- < COAs the strength of the ligand increases, so does the crystal field splitting energy. Strong-field ligands cause a larger splitting of the d-orbitals, while weak-field ligands cause a smaller splitting.For example, consider the coordination complexes [Fe H2O 6]^2+ and [Fe CN 6]^4-. In the first complex, the ligand is H2O, a relatively weak-field ligand. This results in a smaller crystal field splitting energy, and the complex exhibits high-spin configuration with five unpaired electrons. In the second complex, the ligand is CN-, a strong-field ligand. This leads to a larger crystal field splitting energy, and the complex exhibits a low-spin configuration with only one unpaired electron.The implications of this relationship in coordination chemistry are as follows:1. Color: The crystal field splitting energy determines the wavelength of light absorbed by the complex, which in turn affects its color. Complexes with larger splitting energies absorb higher-energy shorter wavelength light, while those with smaller splitting energies absorb lower-energy longer wavelength light.2. Magnetic properties: The number of unpaired electrons in a complex determines its magnetic behavior. High-spin complexes with more unpaired electrons exhibit stronger paramagnetism, while low-spin complexes with fewer unpaired electrons exhibit weaker paramagnetism or even diamagnetism.3. Stability: Strong-field ligands generally form more stable complexes due to the larger crystal field splitting energy. This can be quantified using the Chelate Effect and the Irving-Williams series, which show that stability increases with the strength of the ligand.4. Reactivity: The strength of the ligand and the crystal field splitting energy can also influence the reactivity of the complex. Complexes with larger splitting energies are generally less reactive, as the energy required to remove an electron from the complex is higher.In summary, the strength of the ligand in a coordination complex directly affects the crystal field splitting energy, which in turn influences the complex's color, magnetic properties, stability, and reactivity. Understanding this relationship is crucial for designing coordination complexes with desired properties and applications in various fields, such as catalysis, materials science, and bioinorganic chemistry.