Chiral amino acid-templated tin fluorides tailoring nonlinear optical properties, birefringence, and photoluminescence

초록

In this study, we successfully synthesized two types of new chiral amino acid-templated tin fluoride crystals: (R)-[(C8H10NO3)2]Sn(iv)F6, (S)-[(C8H10NO3)2]Sn(iv)F6, (R)-[C8H10NO3]Sn(ii)F3, and (S)-[C8H10NO3]Sn(ii)F3, employing a slow evaporation method. The crystal structures of Sn(iv)-compounds were determined to belong to the noncentrosymmetric (NCS) nonpolar space group, P21212. Conversely, the structures of Sn(ii)-compounds were found to crystallize in the NCS polar space group, P21, as revealed by single-crystal X-ray diffraction analysis. Remarkably, Sn(iv)-compounds exhibited a larger birefringence (0.328@546.1 nm), attributed to the well-stacked arrangement of planar pi-conjugated benzene rings along the b-axis. The ability of tin(iv) fluorides to form more hydrogen bonds with ligands increased the probability of pi-pi interactions between benzene rings, enabling the growth of centimeter-sized crystals in Sn(iv)-compounds. In contrast, Sn(ii)-compounds displayed a stronger second-harmonic generation (SHG) response (0.85 x KDP) than Sn(iv)-compounds (0.46 x KDP). This enhanced SHG response in Sn(ii)-compounds was attributed to the increased dipole moments resulting from the presence of lone pairs. Additionally, Sn(ii)-compounds exhibited photoluminescent properties due to the transition from the metal-to-ligand charge transfer state, facilitated by the presence of the lone pairs. The new chiral amino acid-templated polar tin fluoride crystals, (R)-[C8H10NO3]Sn(ii)F3 and (S)-[C8H10NO3]Sn(ii)F3, reveal enhanced second-harmonic generation, photoluminescence, and birefringence.

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