Anion Size‐Dependent Conformational Folding of Guanidinopropionate: Enabling Tunable Birefringence and Balanced Second‐Harmonic Generation Performance

). DFT reveals these four conformations are nearly degenerated, and the HOMO-LUMO gap, polarizability anisotropy, and hyperpolarizability across these four conformers are broadly tunable. This work first demonstrates how conformational folding control of flexible π-conjugated units effectively modulates and optimally balances three critical yet mutually restrictive parameters essential for high-performance SHG materials.