A comparative study on the performance of subphthalocyanines and corannulene derivatives as receptors for fullerenes†
Herein, we have employed dispersion corrected density functional theory to study the performance of modified subphthalocyanines and dibenzo[a,g]corannulenes as fullerene receptors. Analysis of the interaction energies and structures of the catchers revealed that subphthalocyanines display excellent ball–socket interactions with C60 and C70. However, dibenzo[a,g]corannulene showed an excellent fit only with C70, as indicated by recent experimental results. Functionalization of subphthalocyanines with long thioalkyl chains increases the interaction energies between receptors and fullerenes. Yet, the effect on the association constant is negligible, and in some cases it can be even harmful, because the long alkyl chains introduce large entropic penalties, which are translated into a small improvement of the free energy changes. We propose a new subphthalocyanine based receptor which bears three 1,4-dithino groups at the peripheral region. The new host has a strong affinity towards C60 and C70, as indicated by theoretical calculations, which showed a large change in free energy when the above-mentioned modification is considered. In spite of the fact that long alkyl chains seem not to be useful in improving the binding affinity of several receptors, we have found that the addition of small ethyl chains to dibenzo[a,g]corannulene increases the affinity of the bowl towards fullerenes. Nevertheless, new functional groups must be attached in places where the stacking interaction between the host and the guest is barely affected; otherwise the loss of π stacking should be compensated by the new functional groups.