The difference in effects of molecules and ions

When hypochlorous acid is added to water, it coexists in both dissociated state (ClO-) and undissociated state (HClO) according to the dissociation equilibrium.
 
Usually, when sodium hypochlorite is diluted, hypochlorous acid exist as ions (ClO-) because the diluted solution is basic. On the other hand, hypochlorous acid exist as both molecules (HClO) since the solution is in the range of pH 6 to pH of 7.
 
The molecules of hypochlorous acid (HClO) can permeate microbial cell wall and plasma membrane very easily since it is very small in molecular size and electrically neutral, and therefore can directly oxidate the nucleus and the cytoplasm. In comparison, ions (ClO-) can affect the cell wall, yet cannot permeate through the plasma membrane.
 
In consequence, hypochlorous acid molecules have much greater effects on bacterial elimination comparing to sodium hypochlorite ions. Furthermore, while infection control measures recommend using chloride concentration of over 1000ppm for a diluted sodium hypochlorite, hypochlorous acid is said to be valid even though it has a chloride concentration of 100 to 200ppm.