The chiroptical response is enabled by the parallel orientation of the transition dipoles (Figure ). It is the mixing of the πsystems through the formally saturated central spiro-carbon that ensures the electric and magnetic transitions dipole moments are reoriented. If we remove rotation symmetry and treat spiropentadiene as quasi-C 2v , the transition density of the electronic transitions is contained within one of the molecular planes (ESI Figure ). Consequently, spiropentadiene is optically inactive because ⃗ µ and ⃗ m are perpendicularly oriented.