Inorganic Chemistry, Vol.55, No.9, 4664-4668, 2016
Scandium Selenophosphates: Structure and Properties of K4Sc2(PSe4)(2)(P2Se6)
The new compound K4Sc2P4Se14 was synthesized via the polychalcogenide flux method. It crystallizes in the space group C2/c, and the structure is composed of (1)/(infinity)[Sc2P4Se144] chains that are separated by K+ cations. The structural motif features two [PSe4](3-) units and one [P2Se6](4-) unit bridging the Sc centers and has not been reported for any other compound. The 1/(infinity)[Sc(2)P(4)Se14(4-)] chains pack in a crosshatched pattern perpendicular to the c axis of the crystal, forming channels for half of the K+ atoms while the other half occupy empty space between the chains. The orange-yellow crystals of K4Sc2P4Se14 are air-sensitive and gradually turn red over the course of a couple hours. The band gap of the phase is 2.25(2) eV, and Raman spectroscopy shows the symmetric stretches of the selenophosphate groups to be at 231 and 216 cm(-1) for the [PSe4](3-) and [P2Se6](4-) units, respectively. Solid-state P-31 MAS NMR of K4Sc2P4Se14 shows two prominent peaks at 11.31 and -23.07 ppm and one minor peak at -106.36 ppm, most likely due to degradation of the product or an unknown second phase.