The Syntheses And Characterizations Of New Chalcogenides Containing Polychalcogen Anion

Chalcogenide nonlinear optical（NLO）crystals that can expand the solid-state laser output range to mid and far infrared（IR）region are the most typical class of IR NLO crystals.Designing new IR NLO chalcogenide crystals is of great significance to the development of modern laser technology.The unique electronic configurations of ns²np⁴ of chalcogen atoms allow them to form two types of chalcogen anions:1)isolated Q^2-（Q=S,Se,Te）anions;2)polymerized（Q_n）^2-（n≥2）polychalcogen anions.They not only enrich structural chemistry of chalcogenides,but also have an important effect on band gap,second harmonic generation（SHG）response,birefringence,etc.In this paper,aiming at the designs and syntheses of new IR NLO chalcogenides,seven new noncentrosymmetric chalcogenides have been successfully designed and synthesized:1.Salt-inclusion polychalcogenides[Ba₄（Q₂）][Zn Ga₄Q₁₀]（Q=S,Se）（Ⅰ）:Wide band gap,strong SHG response and moderate birefringence are three critical optical properties for IR NLO material.Ag Ga S₂-like（AGS-like）chalcogenides exhibit wide band gaps,strong SHG responses while small birefringences.Polychalcogenides have large anisotropy but narrow band gaps.In this work,the（Q₂）^2-polychalcogen anions have been introduced into the ionic guest of salt-inclusion structure to realize a balance among wide band gap,strong SHG response and moderate birefringence.The first case of salt-inclusion polychalcogenide,[Ba₄（S₂）][Zn Ga₄S₁₀]has been successfully synthesized.As a result,[Ba₄（S₂）][Zn Ga₄S₁₀]reaches a great balance among band gap（3.39 e V）,SHG response（0.9×AGS）and birefringence（0.053@1064 nm）.2.Chalcogenides Ba₅Zn₃Ga₂Sn₂Se₁₅（Q=S,Se）（Ⅱ）and Sr₅Zn₃Ga₂Sn₂S₁₅:Alkaline earth（AE）,ⅢA,ⅣA andⅡB elements are the preferred choice to design nonlinear optical materials.Because AE elements have strong electropositivity that can broaden band gaps.ⅢA,ⅣA,andⅡB group elements coordinating with chalcogen atoms can not only form various[MQ_x]（M=Ga,Ge,Sn,Zn,etc;x=2-6）basic building units（BBUs）,these BBUs can also exhibit strong SHG responses with uniform arrangements.In this work,three chalcogenides,Ba₅Zn₃Ga₂Sn₂S₁₅,Ba₅Zn₃Ga₂Sn₂Se₁₅and Sr₅Zn₃Ga₂Sn₂S₁₅,were successfully synthesized.They all exhibit strong SHG responses（2.8-4×AGS）,moderate birefringences（0.051-0.072@1064 nm）and uniform melting thermal behaviors and are promising IR NLO candidates.3.Polychalcogenides[[Ba₄（Q₂）][Zn Ga₃Sn Q₁₀]][Ba₁₀Zn₇Ga₃Sn₄Q₁₅]（Q=S,Se） （Ⅲ）and‘Ⅰ+Ⅱ=Ⅲ’design strategy:A reasonable structure design strategy is of great significance to the development of NLO materials.By chelating polychalcogenidesⅠand chalcogenidesⅡ,two new polychalcogenides[[Ba₄（Q₂）][Zn₂Ga₂Sn Q₁₀]][Ba₁₀Zn₇Ga₃Sn₄Q₃₀]（Q=S,Se）were successfully designed and synthesized.InⅢ,the[[Ba₄（Q₂）][Zn Ga₃Sn Q₁₀]]part and[Ba₁₀Zn₇Ga₃Sn₄Q₃₀]part retained the same structural characteristics ofⅠandⅡ,which is rare in inorganic chemistry.Based on the synthesis of compoundⅢ,a new structure design strategy namely‘Ⅰ+Ⅱ=Ⅲ’is proposed in this paper,which will provide important implications for the development of new IR NLO materials.