Noncentrosymmetric BaInQ (Q = S, Se): Structural Chemistry and Nonlinear-Optical Activity.

The indispensable condition for laser frequency-doubling crystal materials is that they crystallize in the noncentrosymmetric (NCS) structures. Here, ternary NCS BaInS () and BaInSe () (6) were synthesized via conventional solid-state reactions. Their zero-dimensional structures feature isolated InQ tetrahedra and Q (Q = S, Se) dimers that are separated by Ba counter cations. The structural relevance and differences with the centrosymmetric BaInS and BaInSe are analyzed in detail. Both and show obvious laser frequency-doubling activity, and their optical band gaps are 3.72 and 1.78 eV, respectively. This work provides a new type of IR nonlinear-optical materials.