Theoretical study on the diradical characters and third-order nonlinear optical properties of cyclic thiazyl diradical compounds

- Second hyperporizabilities (γ) of cyclic thiazyl diradicaloids (TZs) were studied.
- The diradical character (y) depends on the size, and the positions of heteroatoms.
- The increase in y with the size depends on the positions of heteroatoms.
- The γ values of TZs show an enhancement in the intermediate y region.