A molecular glass compound includes (A) a tetrameric reaction product of a specific aromatic compound having at least one hydroxy group, and a specific polycyclic or fused polycyclic aromatic aldehyde; and (B) an acid-removable protecting group as an adduct with the hydroxy group of the aromatic compound and/or a hydroxy group of the polycyclic or fused polycyclic aromatic aldehyde. A photoresist composition including the molecular glass compound, and a coated substrate including a layer of the photoresist composition are also disclosed.