The coordination geometry of transition metal complexes plays a significant role in determining their photochemical properties. Changing the coordination geometry can lead to alterations in the electronic structure, absorption spectra, and reactivity of the complex. Some of the effects of changing the coordination geometry on the photochemical properties of transition metal complexes are:1. Electronic structure: The coordination geometry affects the energy levels and distribution of d-orbitals in the transition metal complex. Different geometries can lead to different splitting patterns of d-orbitals, which in turn influence the electronic transitions and overall stability of the complex.2. Absorption spectra: The coordination geometry can impact the absorption spectra of transition metal complexes by altering the energy differences between the ground and excited states. This can result in changes in the wavelength and intensity of light absorbed by the complex, which is crucial for photochemical reactions.3. Reactivity: Changing the coordination geometry can influence the reactivity of transition metal complexes by affecting the steric and electronic factors. For example, a change in geometry can alter the accessibility of the metal center to substrates or the strength of metal-ligand bonds, which can impact the rate and selectivity of photochemical reactions.4. Photostability: The coordination geometry can also affect the photostability of transition metal complexes. Some geometries may be more prone to photodissociation or photodegradation, leading to a decrease in the efficiency of photochemical reactions.5. Excited state properties: The coordination geometry can influence the nature and lifetime of excited states in transition metal complexes. This can have a significant impact on the efficiency and pathways of photochemical reactions, such as energy transfer, electron transfer, and ligand exchange processes.In summary, changing the coordination geometry of transition metal complexes can have a profound effect on their photochemical properties by influencing their electronic structure, absorption spectra, reactivity, photostability, and excited state properties. Understanding these effects is crucial for designing efficient and selective photochemical systems in various applications, such as solar energy conversion, photocatalysis, and photopharmacology.