Studies of Novel Quaternary Main Group Chalcophosphates, Chalcogermanates, and Chalcostannates from Exploratory Synthesis

The polychalcogenide flux method has been crucial in moving the field of solid state chemistry forward. Chalcophosphate fluxes formed by the addition of P2Q5 (Q= S, Se) to a polychalcogenide flux are intriguing in that dissolved [PyQz]x- units are able to undergo reactions with other species within the molten media. Reaction temperatures below 600 °C allow otherwise unattainable compounds to be isolated and characterized. These metastable compounds are of varying dimensionality and often exhibit interesting properties such as ferroelectricity, photoluminescence, reversible crystal-to-glass phase transitions, and second harmonic generation.;The library of known quaternary rare earth and transition metal chalcophosphates is immense. The number of reported quaternary main group chalcophosphates is much less and most contain the larger congeners of Groups 13, 14, and 15. This work gives attention to the synthesis and characterization of chalcophosphates containing smaller main group elements, namely As and Ge. A number of molecular As-containing chalcophosphates, some which are structurally related to previously reported chalcophosphates, are presented in Chapter 2. Chapters 3 and 4 highlight chalcophosphates containing Ge. The incommensurately modulated, one-dimensional structure of K4Ge4-xPxSe 12 is presented in Chapter 3 along with the molecular compound Rb 6Ge2P2Se14. Annealing crystals of K 4Ge4-xPxSe12 below their melting point for 30 d was required to obtain sharp supercell reflections for a suitable refinement. Chapter 4 presents the new series of quaternary molecular chalcophosphates A4GeP4Q12 (A= K, Rb, Cs; Q= S, Se). The selenides are noncentrosymmetric and are shown to have intact molecules in their melt quenched amorphous phases. Broadband second harmonic generation (SHG) measurements reveal K4GeP4Se12 exhibits the strongest response among the reported phases, as well as measurable response in its glassy phase. The importance of broadband measurements is emphasized in this chapter. Chapter 5 moves on to a large family of layered chalcostannates and chalcogermanates synthesized using the flame-melting rapid-quenching method and whose optical properties were investigated as a function of composition. The final two chapters cover ternary thiophosphate compounds. The structure and Se substitution of spontaneously forming AsPS4 nanotubes is presented in Chapter 6 and the structure of two discrete molecular thiophosphates, Cs 4P2S8 and Rb4P2S10 , in Chapter 7.