Structural, spectral and nonlinear optical analysis of Sodium bis(2-methyllactato)borate: a new semiorganic crystal for photonic applications

Abstract

Semiorganic single crystals of Sodium bis(2-methyllactacto)borate (NaMB) have been grown using solvent evaporation process. NaMB crystal comprises a bis(2-methyllactato)borate anion and a sodium cation. Powder XRD pattern reveals the good crystallinity. Linear optical transmittance window is found to be 215–1100 nm. Na⋯O–C intermolecular interaction is observed in the grown crystal and it is established by observed vibrational frequencies. Functional group associated with borate is well addressed through the vibrations observed in FTIR and FT-Raman spectroscopy. 13C NMR spectroscopy enunciates the position of carbon atoms in the crystal structure. Intermolecular interactions such as Na1⋯O6–C5 and Na1⋯O1–C1 where O6 and O1 are uncoordinated oxygen atoms of carboxylato groups which pulls the electrons from C5 and C1 and causes deshielding effect resulting in shifting of C5 and C1 signals towards higher ppm. These interactions are also established through the shifts observed in 1H NMR spectroscopy. The third order nonlinear susceptibility (χ3) value is 1.07911 × 10−6 esu and this larger value is due to electron delocalization in carboxylato group and charge transfer due to intermolecular interaction present in the crystal structure. The self-focussing and saturable absorption nature of the crystal may be utilized in optical sensors and Q-switching applications.