Ba3(C4H4O5)2(OH)2: A Novel Short-Wavelength Alkaline Earth Metal 2-Hydroxybutanedioate

With the continuous development of optical science and technology, there are higher requirements for the versatility and multi-application scenarios of optical devices. Organic–inorganic hybrid birefringent crystals have attracted much attention due to their high flexibility in molecular design and assembly. In this work, an alkaline earth metal 2-hydroxybutanedioate Ba 3 (C 4 H 4 O 5 ) 2 (OH) 2 crystallizing in the C 2/ c space group is synthesized by the hydrothermal method. Its unit cell parameters are a = 20.0584(7) Å, b = 7.4499(3) Å, c = 9.5087(3) Å, and β = 96.808(2) °. Ba 3 (C 4 H 4 O 5 ) 2 (OH) 2 polycrystalline powder is characterized in detail by Fourier transform infrared (FTIR) absorption spectroscopy, UV–vis–NIR diffuse reflectance spectroscopy, and simultaneous thermal analysis. In addition, theoretical analyses are carried out using first-principles calculations and Hirshfeld surface analysis. The theoretical birefringence of Ba 3 (C 4 H 4 O 5 ) 2 (OH) 2 is calculated to be 0.1 @546 nm. At the same time, UV–vis–NIR diffuse reflectance and band structure calculations show that Ba 3 (C 4 H 4 O 5 ) 2 (OH) 2 has an indirect bandgap of 5.11 eV with a UV cutoff edge of 203 nm. By leveraging the complementary attributes of organic and inorganic materials, Ba 3 (C 4 H 4 O 5 ) 2 (OH) 2 stands out as a promising UV birefringent candidate.