Zigzag molecular belts have captured the imagination of scientists for over a half
century because of their aesthetically appealing structures and tantalizing properties.
One of the formidable challenges in synthesis is to circumvent the energy accumulated
in the construction of strained structures. Reported herein is our theoretical study
to quantify the molecular strain energies. A general exponential function equation
E
strain = a·n·e
−n/b
was obtained to estimate strain energies of both conjugated and partially hydrogenated
hydrocarbon belts and their heteroatom-embedded analogs. The deformation of aromatic
rings from planarity was revealed to contribute dominantly to the high strain energies.
The method enabled the convenient quantification of the energetics of aromatization
processes from partially hydrogenated double-stranded macrocycles, and facilitated
the design and optimization of practical routes to synthesize the long-awaited zigzag
molecular belts.
Key words
zigzag hydrocarbon belts - belt[
n]arenes - macrocycles - strain energy
