Computational Study of Ground-State Destabilization Effects and Dipole-Dipole Interaction Energies in Amphidynamic Crystals.

Ground-state destabilization is a promising strategy to modulate rotational barriers in amphidynamic crystals. Density functional theory studies of polar phenylenes installed as rotators in pillared paddle-wheel metal organic frameworks were performed to investigate the effects of ground-state destabilization on their rotational dynamics. We found that as the steric size of phenylene substituents increases, the ground-state destabilization effect is also increased. Specifically, a significant destabilization of the ground-state energy occurred as the size of the substituents increased, with values ranging from 2 to 11.7 kcal/mol. An evaluation of the effects of substituents on dipole-dipole interaction energies and rotational barriers suggests that it should be possible to engineer amphidynamic crystals where the dipole-dipole interaction energy becomes comparable to the rotational barriers. Notably, while pure dipole-dipole interaction energies reached values ranging from 0.6 to 2.4 kcal/mol, the inclusion of electronic and steric effects can alter dipolar orientations to significantly greater values. We propose that careful selection of polar substituents with different sizes may help create temperature-responsive materials with switchable collective polarization.