The tellurophosphate K(4)P(8)Te(4): phase-change properties, exfoliation, photoluminescence in solution and nanospheres.

We describe the inorganic polymer K(4)P(8)Te(4) which is soluble, giving solutions that exhibit white emission upon 355 nm laser irradiation. An indirect band gap semiconductor (E(g) approximately 1.4 eV), K(4)P(8)Te(4) crystallizes in the space group P2(1)/m, with a = 6.946(1) A, b = 6.555(1) A, c = 9.955(2) A, and beta = 90.420(3) degrees at 173(2) K. The compound features infinite chains of [P(8)Te(4)(4-)] with covalent P-Te bonding and exhibits reversible crystal-glass phase-change behavior. When deposited from solution, the material forms highly crystalline K(4)P(8)Te(4) nanospheres. The thermal analysis, FT-IR, UV-vis diffuse reflectance, (31)P magic angle spinning solid-state NMR spectroscopy, and pair distribution function (PDF) analysis for the crystal and glass forms and ab initio electronic structure calculations by the screened-exchange local density function approximation are also reported. Speciation of K(4)P(8)Te(4) in solution studied with (31)P solution-state NMR spectroscopy, electrospray ionization mass spectrometry, and PDF analysis indicate exfoliation of [P(8)Te(4)(4-)] chains followed by rearrangement into molecular species.