The Tellurophosphate K 4 P 8 Te 4 : Phase-Change Properties, Exfoliation, Photoluminescence in Solution and Nanospheres In Chung, †,‡ Jung-Hwan Song, § Myung Gil Kim, ‡ Christos D. Malliakas, †,‡ Angela L. Karst, † Arthur J. Freeman, § David P. Weliky, † and Mercouri G. Kanatzidis* ,‡ Department of Chemistry, Michigan State UniVersity, East Lansing, Michigan 48824, and Department of Chemistry and Department of Physics and Astronomy, Northwestern UniVersity, EVanston, Illinois 60208 Received August 27, 2009; E-mail: m-kanatzidis@northwestern.edu Abstract: 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 ≈ 1.4 eV), K 4 P 8 Te 4 crystallizes in the space group P2 1 /m, with a ) 6.946(1) Å, b ) 6.555(1) Å, c ) 9.955(2) Å, and  ) 90.420(3)° 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. 1. Introduction Solid-state compounds with P-Te bonding have long been elusive, although phosphorus, in general, has been known to combine with nearly all elements. 1 The paucity of P-Te bonds is in striking contrast to the well-established metal chalco- phosphate class 2-6 involving the ternary (M/P/Q) and quaternary (A/M/P/Q) compounds with [P x Q y ] z- anions. The only reported P/Te containing inorganic compounds are MPTe (M ) Ru, Os, 7 Ir 8 ) and BaP 4 Te 2 . 9 The latter features P-Te bonding, while only unit cell dimensions and spectroscopic data have been reported for the former. On the other hand, organometallic compounds provide some examples of P-Te bonded species, for example, Et 3 PTeX 2 (X ) Cl, Br, I), 10 TePPh 2 Ch 3 11 and Ph 3 PTe(Ph)I. 12 The larger elements in group 15, As, Sb, and Bi, show a wealth of chemistry with Te to produce a broad set of solid-state inorganic materials. 13-15 Recently, we reported rational synthesis conditions that stabilize P-rich species and avoid the simple classical [PSe 4 ] 3- and [P 2 Se 6 ] 4- anions through the use of excess phosphorus in the flux. Examples are A 6 P 8 Se 18 (A ) K, Rb, Cs), 16 Rb 4 P 6 Se 12 , 17 Cs 4 P 6 Se 12 , and Cs 5 P 5 Se 12 , 18 yet with the exception of BaP 4 Te 2 there is a scarcity of species with P-Te bonds. Here we report on the new alkali tellurophosphate compound K 4 P 8 Te 4 featuring P-Te bonding and the infinite anion [P 8 Te 4 4- ]. The compound was prepared with the molten salt flux method 2,19 at intermediate temperature, and it shows reversible phase-change behavior. K 4 P 8 Te 4 was found to be soluble in hydrazine to give a colloidal solution of n 1 [P 8 Te 4 4- ] species. This is a useful property of K 4 P 8 Te 4 , because, generally, it is very difficult to disperse polymeric solids in polar solvents. † Michigan State University. ‡ Department of Chemistry, Northwestern University. § Department of Physics and Astronomy, Northwestern University. (1) von Schnering, H. G.; Ho ¨nle, W. Chem. ReV. 1988, 88, 243–273. (2) Chondroudis, K.; Hanko, J. A.; Kanatzidis, M. G. Inorg. Chem. 1997, 36, 2623–2632. (3) Chondroudis, K.; McCarthy, T. J.; Kanatzidis, M. G. Inorg. Chem. 1996, 35, 840–844. (4) Mccarthy, T. J.; Kanatzidis, M. G. Inorg. Chem. 1995, 34, 1257– 1267. (5) Chondroudis, K.; Kanatzidis, M. G. Inorg. Chem. 1995, 34, 5401– 5402. (6) Mccarthy, T. J.; Kanatzidis, M. G. Chem. Mater. 1993, 5, 1061–1063. (7) Lutz, H. D.; Schmidt, T.; Waschenbach, G. Z. Anorg. Allg. Chem. 1988, 562, 7–16. (8) Kliche, G. Z. Naturforsch., B 1986, 41, 130–131. (9) Jo ¨rgens, S.; Johrendt, D.; Mewis, A. Chem.sEur. J. 2003, 9, 2405– 2410. (10) Konu, J.; Chivers, T. Dalton Trans. 2006, 3941–3946. (11) Dornhaus, F.; Bolte, M.; Lerner, H. W.; Wagner, M. Eur. J. Inorg. Chem. 2006, 1777–1785. (12) Boyle, P. D.; Cross, W. I.; Godfrey, S. M.; McAuliffe, C. A.; Pritchard, R. G.; Sarwar, S.; Sheffield, J. M. Angew. Chem., Int. Ed. 2000, 39, 1796–1798. (13) Poudeu, P. F. P.; Kanatzidis, M. G. Chem. Commun. 2005, 2672– 2674. (14) Hsu, K. F.; Lal, S.; Hogan, T.; Kanatzidis, M. G. Chem. Commun. 2002, 1380–1381. (15) Sheldrick, W. S.; Wachhold, M. Coord. Chem. ReV. 1998, 176, 211– 322. (16) Chondroudis, K.; Kanatzidis, M. G. Inorg. Chem. 1998, 37, 2582– 2584. (17) Chung, I.; Karst, A. L.; Weliky, D. P.; Kanatzidis, M. G. Inorg. Chem. 2006, 45, 2785–2787. (18) Chung, I.; Jang, J. I.; Gave, M. A.; Weliky, D. P.; Kanatzidis, M. G. Chem. Commun. 2007, 4998–5000. (19) Kanatzidis, M. G. Curr. Opin. Solid State Mater. Sci. 1997, 2, 139– 149. Published on Web 10/21/2009 10.1021/ja907273g CCC: $40.75  2009 American Chemical Society J. AM. CHEM. SOC. 2009, 131, 16303–16312 9 16303