Segregated stacks
This mode of packing is seen when the alkyne substituent is very large (substituent diameter slightly greater than half the length of the pentacene). Because of the two-dimensional pi-overlap seen in this packing motif, acenes that adopt this sort of solid-state pi-stacked order tend to exhibit the best device performance.
Slip-stacks
The majority of derivatives we've prepared arrange as slipped-stacks, which is the order we see when the solubilizing "ball" is less than half the length of the pentacene. As an example, here is the trimethylsilyl (TMS) derivative.
Columnar stacks
By offsetting the substituent group, the acenes are able to form nearly columnar stacks. Although the pi-overlap between any two pentacene molecules in the stack is quite good, the materials are not particularly stable, and thus not useful for electronic devies.
