A 14-porphyrin rugby ball
Harry Anderson's latest creation
Having done my PhD in the Champness group — a lab that dabbles heavily in porphyrin synthesis — I’m no stranger to sitting down and ogling at Harry Anderson’s group’s latest creations. I certainly remember a group meeting around the time of the 12-porphyrin nanoring that left everyone in the room feeling simultaneously shell-shocked and inspired.
I had the pleasure of seeing Harry present at MASC 2016, where again, I was blown away (as I suspect most people in the room were) by his porphyrin nanotubes and ring-in-ring structures. Yesterday, as I was scrolling through twitter, I was delighted to come across another exceptional piece of work from this lab. This time, they’ve fashioned a 14-porphyrin structure composed of two perpendicular intersecting nanorings that superficially looks something like a rugby ball, reminiscent of the shape of C70.
They build the structure up bit by bit using a typical Anderson templating strategy and then couple the extremities together at the end to create a closed, continuous structure. Excitingly, this porphyrin ball is fully π-conjugated. Using fluorescence upconversion spectroscopy they find that prior to template removal, where the conformation is locked in, electronic excitation delocalizes over the entire system within 0.3 ps, and within 2 ps in the absence of the templates. Thanks to rapid migration of the excitation between the two perpendicular rings, the system also displays a fluorescence anisotropy that approaches zero.
The motivation for building these high dimensional π-conjugated systems clearly lies in their light-harvesting abilities, but for me, as a synthetic chemist, just looking at the synthetic route in Figure 2 makes me feel rather giddy, particularly when you start thinking about purification steps…