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 TC1 ~ 105 °C, with a helix–helix transition at TC2 ~ 28 °C, and exhibits gabs = +1.3 × 10−2 at −10 °C. Synchronously, the CPL band at 340 nm exhibiting glum = −0.7 × 10−2 at 60 °C inverts to glum = +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 gabs values by an order of magnitude, and oppositely signed CD and a lower TC1 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.