How far can we push chemical self-assembly? This is one of the current big questions  in science. Hydrogen bonds and the coordination of metal ions have been the most-commonly used forces to drive the spontaneous organization of small building blocks into large, complex, and sometimes functional structures. The use of pi-stacking and van der Waals forces is now well documented. Other intermolecular forces have not been used mostly because they have been poorly understood until now, as is the case for the inter-atomic contacts made by the heavy p-block elements. The succession of names given to this phenomenon parallels the evolution of our understanding: the initial 'non-bonded contact" became"weakly bonding interaction" and now the term "secondary bonding interaction"(SBI) is gaining increasing acceptance.

Our research program pursues the use of SBIs of heavy p-block elements in supramolecular chemistry and molecular self-assembly. SBIs have distinctive features that can be exploited to control the properties of self-assembled materials. For example, while hydrogen bonds are barriers to electron mobility, SBIs enhance conductivity. In addition, SBIs can stabilize compounds with unusual compositions. In summary, new interactions translate in new properties.

Noncentrosymmetric supramolecular structures exhibit nonlinear optical (NLO) properties, there are many known examples of supramolecular NLO materials built with hydrogen bonds. However, hydrogen bonds absorb light in the near-infrared and such materials are not useful in optical fibre technology. SBIs vibrate at much lower frequencies and their supramolecular nonlinear optical materials should have greater transparency. An additional advantage to using heavy elements, the soft electron clouds of these atoms result in unusually strong nonlinear properties. This is precisely a second major interest of our group. We have designed and synthesized molecules with promising nonlinear activity and have developed our own Second Harmonic Generation spectrometer with a tunable excitation wavelength.