Changing the molecular geometry can significantly affect the electronic excited states and optical properties of a molecule. The electronic excited states are determined by the distribution of electrons in the molecule and their energy levels. The optical properties, such as absorption and emission spectra, are related to the electronic transitions between these energy levels. When the molecular geometry changes, several factors come into play:1. Change in bond lengths and angles: Altering the molecular geometry can lead to changes in bond lengths and angles, which in turn affects the electron distribution and energy levels. This can cause shifts in the energy levels of the electronic excited states, leading to changes in the absorption and emission spectra.2. Change in orbital overlap: The extent of overlap between atomic orbitals in a molecule determines the strength and nature of the chemical bonds. A change in molecular geometry can lead to changes in the orbital overlap, which can affect the electronic structure and energy levels of the molecule. This can result in changes in the optical properties, such as the position and intensity of absorption and emission bands.3. Change in symmetry: The symmetry of a molecule plays a crucial role in determining its electronic structure and optical properties. A change in molecular geometry can lead to a change in the symmetry of the molecule, which can affect the allowed electronic transitions and selection rules. This can lead to the appearance or disappearance of certain absorption or emission bands in the optical spectra.4. Change in dipole moment: The dipole moment of a molecule is related to the distribution of charges within the molecule. A change in molecular geometry can lead to a change in the dipole moment, which can affect the intensity of the electronic transitions and the optical properties of the molecule.5. Change in conjugation and electronic delocalization: In conjugated systems, the electronic excited states and optical properties are strongly influenced by the extent of conjugation and electronic delocalization. A change in molecular geometry can disrupt or extend the conjugation, leading to changes in the electronic structure and optical properties.In summary, changing the molecular geometry can have significant effects on the electronic excited states and optical properties of a molecule. These changes can be observed through shifts in absorption and emission spectra, changes in the intensity of spectral bands, and the appearance or disappearance of certain bands due to changes in selection rules. Understanding these effects is crucial for designing molecules with specific optical properties for applications in areas such as photovoltaics, sensors, and organic light-emitting diodes OLEDs .