Na₁₀Zn(NO₃)₄(SO₃S)₄: a nonlinear optical crystal combining inorganic π-conjugated and non-π-conjugated heteroanion groups

The research on nonlinear optical (NLO) crystals is mainly focused on two relatively separate systems, π-conjugated or non-π-conjugated systems, respectively. In this work, we report a new NLO crystal Na₁₀Zn(NO₃)₄(SO₃S)₄ combining inorganic π-conjugated [NO₃] and non-π-conjugated heteroanion [S₂O₃] groups, which was synthesized by the aqueous solution method. In the structure, the similar coexistence of planar triangular anionic groups (π-conjugated) and heteroanion tetrahedra (non-π-conjugated) is rarely mentioned, which provides a new approach for designing NLO crystals. Notably, this compound exhibits a phase-matching second-harmonic generation (SHG) response 1.2 times that of KH₂PO₄. In addition, birefringence, absorption edge and theoretical calculations are also reported in this article. This work provides a new designing route to expand NLO systems via combining planar π-conjugated and non-π-conjugated heteroanion groups.