The transformation of a zero-dimensional cluster into a one-dimensional chain structure achieving a dramatically enhanced birefringence in tin(II)-based oxalates

Developing new birefringent materials with large optical anisotropy is extremely urgent due to the fantastic progress of laser science and technology. Here, two tin(II)-based oxalates, K2Sn(C2O4)(2)center dot H2O and K2Sn2(C2O4)(2)F-2 center dot H2O, were successfully synthesized by simultaneously introducing pi-conjugated [C2O4](2)groups and distorted Sn2+-polyhedra with stereochemically active lone pairs. The use of F- regulates the arrangement of birefringence-active groups, resulting in the transformation of zero-dimensional (0D) K2Sn(C2O4)(2)center dot H2O into 1D K2Sn2(C2O4)(2)F-2 center dot H2O, which successfully enhances birefringence from 0.103@546 nm to 0.301@546 nm. Meaningfully, detailed structural and property analysis demonstrates that the ideal spatial arrangement of all the birefringence-active functional modules can induce strong optical anisotropy, providing an idea for designing birefringent materials with excellent properties.