Room-temperature molecular luminescent ferroelectrics based on chiral molecular hybrids incorporating polycyanidometallate ions

Chiral luminescent and ferroelectric molecular materials offer exciting opportunities for multifunctional device applications, yet examples combining strong optical activity, nonlinear response, and switchable polarization remain scarce. Here, we report a new series of crystalline materials based on enantiopure (S,S)- and (R,R)-N-methyl-2-phenyl-4,5-pinenopyridinium cations and di- or tetracyanidometallates of Ag(I), Au(I), Pd(II), and Pt(II). All compounds crystallize in the noncentrosymmetric polar P2₁ space group, and exhibit strong second-harmonic generation (SHG) signals, with the Au(I)-analogue reaching 22.9% of KDP. Circular dichroism confirmed the retention of chirality in the solid state, while solid-state photoluminescence revealed tailorable optical properties with high quantum yields, up to 19% for Pt(II) derivatives. Moreover, piezoresponse force microscopy (PFM) demonstrated stable ferroelectric domains and field-switchable polarization in Ag(I)- and Pd(II)-based materials. These results establish a modular platform for designing multifunctional, chiral molecular materials with luminescent, nonlinear optical, and ferroelectric properties.