Nuclear-Spin-Dependent Chirogenesis: Hidden Symmetry Breaking of Poly(di-n-butylsilane) in n-Alkanes

Since the 1960s, theorists have claimed that the electroweak force, which unifies parity-conserving electromagnetic and parity-violating weak nuclear forces, induces tiny parity-violating energy differences (10⁻¹⁰–10⁻²¹ eV) between mirror-image molecules. This study reports the dual mirror-symmetry-breaking and second-order phase transition characteristics of mirror-symmetric 7₃-helical poly(di-n-butylsilane) in n-alkanes under static (non-stirring) conditions. In particular, n-dodecane-h₂₆ significantly enhances the circular dichroism (CD) and circularly polarized luminescence (CPL) spectra. A new (−)-CD band emerges at 299 nm below T_C1 ~ 105 °C, with a helix–helix transition at T_C2 ~ 28 °C, and exhibits g_abs = +1.3 × 10⁻² at −10 °C. Synchronously, the CPL band at 340 nm exhibiting g_lum = −0.7 × 10⁻² at 60 °C inverts to g_lum = +2.0 × 10⁻² at 0 °C. Interestingly, clockwise and counterclockwise stirring of the mixture induced non-mirror-image CD spectra. n-Dodecane-d₂₆ weakens the g_abs values by an order of magnitude, and oppositely signed CD and a lower T_C1 of ~45 °C are observed. The notable H/D isotope effect suggests that the CH₃ termini of the polysilane and n-dodecane-h₂₆, which comprise a three identical nuclear spin-1/2 system in a triple-well potential, effectively work as unidirectional hindered rotors due to the handedness of nuclear-spin-dependent parity-violating universal forces. This is supported by the (−)-sign vibrational CD bands in the symmetric and asymmetric bending modes of the CH₃ group in n-dodecane-h₂₆.