Four New Thioantimonates(III) with the General Formula [<i>TM</i>(tren)]Sb₄S₇ (<i>TM</i> = Mn, Fe, Co, Zn) with the Transition Metal as Part of a Thioantimonate(III) Network Synthesized under Solvothermal Conditions and Tuning of the Optical Band Gap by the Transition Metal Cation

Abstract

Abstract Four new thioantimonate(III) compounds with the general formula [ TM (tren)]Sb 4 S 7 , TM = Mn 1 , Fe 2 , Co 3 and Zn 4 , were synthesized under solvothermal conditions by reacting elemental TM , Sb and S in an aqueous solution of tren ( tren = tris(2‐aminoethyl)amine). All compounds crystallize in the monoclinic space group P2 1 /n with four formula units in the unit cell. Single crystal X‐ray analyses of 1 [a = 8.008(2), b = 10.626(2), c = 25.991(5) Å, β = 90.71(3)°, V = 2211.4(8) Å 3 ], 2 [a = 8.0030(2), b = 10.5619(2), c = 25.955(5) Å, β = 90.809(3)°, V = 2193.69(8) Å 3 ], 3 [a = 7.962(2), b = 10.541(2), c = 25.897(5) Å, β = 90.90(3)°, V = 2173.0(8) Å 3 ] and 4 [a = 7.978(2), b = 10.625(2), c = 25.901(5) Å, β = 90.75(3)°, V = 2195.2(8) Å 3 ] reveal that the compounds are isostructural. The [Sb 4 S 7 ] 2‐ anions are composed of three SbS 3 trigonal pyramids and one SbS 4 unit as primary building units (PBU). The PBUs share common edges and corners to form semicubes (Sb 3 S 4 ) which may be regarded as secondary building units (SBU). The SBUs and SbS 3 pyramids are joined in an alternating fashion yielding the [Sb 4 S 7 ‐ ] anionic chain which is directed along [100]. Weaker Sb‐S bonding interactions between neighbored chains lead to the formation of layers within the (001) plane which contain pockets that are occupied by the cations. The TM 2+ ions are in a trigonal bipyramidal environment of four N atoms of the tren ligand and one S atom of the thioantimonate(III) anion. The optical band gaps depend on the TM 2+ ion and amount to 3.11 eV for 1 , 2.04 eV for 2 , 2.45 eV for 3 , and 2.60 eV for 4 .