A3Mn2Sb3S8 (A = K and Rb): a new type of multifunctional infrared nonlinear optical material based on unique three-dimensional open frameworks

Abstract

Exploring inorganic materials with two or more different physical properties has become an important and emerging topic in solid-state chemistry. Despite the considerable progress achieved recently, however, multifunctional infrared nonlinear-optical (IR-NLO) chalcogenides are still rarely reported. This paper is the first report of quaternary manganese thioantimonates, A₃Mn₂Sb₃S₈ (A = K and Rb), developed using a facile surfactant–thermal method. Both compounds are isostructural and belong to the tetragonal space group I2m (no. 121). Their structures are composed of unique three-dimensional non-centrosymmetric [Mn₂Sb₃S₈]³⁻ frameworks and intervening alkali A⁺ cations. Significantly, A₃Mn₂Sb₃S₈ (A = K and Rb) not only show type-I phase-matching features with moderate second-harmonic generation (SHG) effects and strong laser-induced damage thresholds but also display temperature-dependent paramagnetism and photocurrent responses. In addition, the highly polarizable [Sb₃S₇]⁵⁻ group in this type of structure is a beneficial NLO-active motif, which can be instrumental in designing new IR-NLO materials with suitable birefringence and strong SHG efficiency based on the experimental and theoretical research results. This study will contribute to enrich the diversity of lone-pair cation-based NLO-active units and open a new avenue for discovering other multifunctional IR-NLO materials.