To quantify the potential for interactions between these groups we performed potential energy scans for head-to-tail homodimers of RM734, and compounds 6-9 Our calculations employ the B3LYP hybrid functional, GD3BJ dispersion correction, the LAN2DZ basis set, and additional counterpoise correction. We start from a homodimer of each compound, with the Ph-NO2 and Ph-X bondswhere X is OMe, F, Cl, Br, or Ibeing oriented on the same vector and with a separation of 2.5 Å between the nitro and X groups, and increase the separation in 0.1 Å steps. We compute the complexation energy as function of the distance between the nitro group and the terminal group in question by performing relaxed scans about the potential energy surface (Fig. ). The iodo terminated material 6 has the largest sigma hole and this displays a large complexation energy (~2.7 kcal mol -1 ) at a separation of 3.7 Å. In contrast, the bromterminated material has a much smaller complexation energy (~ 1.3 kcal mol -1 ) and the chloro is smaller still (~ 0.4 kcal mol -1 ). Owing to the electronegativity of its terminal fluorine group, 9 experiences electrostatic repulsion (i.e. positive complexation energy).