M(NH2SO3)2·xH2O (M = Ca, Pb, x = 0, 1, 4): Effect of Hydrogen Bonding on Structural Transformations and Second Harmonic Generation of Metal Sulfamates

Nonlinear optical (NLO) crystals are very important for laser technology, but the performances of available NLO crystals are still insufficient for increasing demand. Recently, the exploration of new NLO crystals in non-π-conjugated systems with the heteroatomic tetrahedra is attracting a lot of interest. In this work, we systematically explore the metal sulfamates containing [NH2SO3] groups and four metal sulfamates, namely, Ca(NH2SO3)2·4H2O, Ca(NH2SO3)2·H2O, Pb(NH2SO3)2·H2O, and Pb(NH2SO3)2 were synthesized by aqueous solution and hydrothermal methods. Notably, these metal sulfamates exhibit different crystal structures and optical properties owing to the diverse arrangement of the functional groups in their structures. In addition, due to hydrogen bond regulation, the centrosymmetric (CS) compound Ca(NH2SO3)2·4H2O can transform into noncentrosymmetric (NCS) Ca(NH2SO3)2·H2O, leading to NLO activity. Experimental characterizations and theoretical analysis reveal that these metal sulfamates are ultraviolet transparent and suitable for developing new NLO materials.