Utilization of photoinitiated isornerization reaction has recently emerged as a very promising platform to modulate the basicity of compounds; however, theoretical insight into its regulatory mechanism remains largely unknown and needs to be addressed. For the first time, an unexpected trans-cis photoisomeritation via the N=N out of plane (NOOP) motion triggered by an in-plane inversion of N-N=N moiety was computationally demonstrated to regulate the pOH jump of water solvated triazabutadiene by using the Jnulticonfigurational perturbation theory together with the calculation of rate constants.of protonationdeprotonation reactions. Kinetic analyses show that the dramatic pOH change can be attributed to the reinforced intramolecular hydrogen bonding resulting from water cluster reorientation and the enhanced coupling between the rotated pi orbital and N lone pair of triazabutadiene in the remarkable trans-cis photoisomerization.