We have calculated the ${pi}$-electron density, atom self-polarizability, and free valence on each atom of N-(2-chlorobenzyl)-pyridinium, N-(benzyl)-2-chloropyridinium, and N-(2-chlorobenzyl)-2-chloropyridinium salts using a simple Huckel method in order to discuss their intramolecular photocyclization reaction in a qualitative method. Our calculation qualitatively predicts that photocyclization occurs through forming radicals as a reaction intermediate by breaking a C-Cl bond after photoexcitation into a triplet state via intersystem crossing from an initially excited singlet state. We noticed that this C-Cl bond breaking is aided by ${pi}$-complex formation between a chlorine atom and the ${pi}$ -electrons of the neighboring ring in the triplet state and a stronger ${pi}$-complex bond makes C-Cl bond breaking, i.e., radical formation, much easier. A chlorine atom will form a stronger ${pi}$ -complex bond to a benzyl ring of N-(benzyl)-2-chloropyridinium than a pyridinium ring of N-(2-chlorobenzyl)-pyridinium because the former can donate its ${pi}$-electron more easily than the latter. The chlorine at position 15 of N-(2-chlorobenzyl)-2-chloropyridinium salt in the excited state also provides its ${pi}$-electron to the benzyl ring. So this ${pi}$-electron can increase the bond strength of the $pi-complex.$ Therefore, the strength of ${pi}$-complex follows the order of N-(2-chlorobenzyl)-2-chloropyridinium, N-(benzyl)-2-chloropyridinium, and N-(2-chlorobenzyl)-pyridinium salts and thus the radical formation rate. This provides us with an intramolecular photocyclization reaction rate of the same order as given above.