The conformational changes of bisoprolol (BISO) are crucial for understanding its interaction with the receptor and the mechanism of action. Therefore, here we investigated the free energy conformational landscape of the free bisoprolol base, aiming at describing the 3D structures and energetic stability of its conformers. Twenty-three unique conformers, within an energy window of 2.44 kcal×mol-1 were identified by conformational search in gas-phase, at B3LYP/6-31+G theoretical level of theory. Among these, the 10 most stable were further refined in water at the same level of theory. The most stable conformers in gas-phase exhibit an S-shape structure. The most stable conformer was used to compute the absorption spectrum of bisoprolol
