Polythiazyl

Polythiazyl (polymeric sulfur nitride), (SN)x, is an electrically conductive, gold- or bronze-colored polymer with metallic luster. It was the first conductive inorganic polymer discovered[1][2] and was also found to be a superconductor at very low temperatures (below 0.26 K).[3][4] It is a fibrous solid, described as "lustrous golden on the faces and dark blue-black", depending on the orientation of the sample. It is air stable and insoluble in all solvents.[5]

Polythiazyl
Names
Other names
polythiazyl
poly(sulfur nitride)
Identifiers
ChemSpider
  • none
Properties
(SN)x
Appearance Golden or bronze-coloured crystalline solid with metallic lustre[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

History

The compound was first reported as early as 1910 by F.P. Burt, who obtained it by heating tetrasulfur tetranitride in vacuum over silver wool.[6]

The compound was the first non-metallic compound in which superconductivity could be demonstrated. However, the relatively low transition temperature at about 0.3 K makes a practical application unlikely.[7][8]

Properties

Polythiazyl is a metallic-golden and shiny, crystalline but fibrous material.[8] The polymer is mostly inert to oxygen and water, but decomposes in air to a grey powder.[9][10] At temperatures above 240 °C explosive decomposition can occur.[11] The compound also explodes on impact.[10] Explosion generally proceeds via decomposition to the elements.

Polythiazyl shows an anisotropic electrical conductivity. Along the fibres or SN chains, the bond is electrically conductive, perpendicular to it acts as an insulator. The one-dimensional conductivity is based on the bonding conditions in the S-N chain, where each sulfur atom provides two π electrons and each nitrogen atom provides one π electron to form two-center 3π electron bonding units.[8]

Two polymorphic crystal forms were observed in the compound. The monoclinic form I obtained from the synthesis can be converted into an orthorhombic form II by mechanical treatment such as grinding.[12]

Structure and bonding

The material is a polymer, containing trivalent nitrogen, and divalent and tetravalent sulfur. The S and N atoms on adjacent chains align.[2][13][14] Several resonance structures can be written.[15]

Polythiazyl resonance structures

The structure of the crystalline compound was resolved by X-ray diffraction. This showed alternating S–N bond lengths of 159 pm and 163 pm and S–N–S bond angles of 120 ° and N–S–N bond angles of 106 °.[16][17][9][8]

Synthesis

Polythiazyl is synthesized by the polymerization of the cyclic formal dimer disulfur dinitride (S2N2), which is in turn synthesized from the formal tetramer tetrasulfur tetranitride (S4N4),[2] in the presence of hot silver wool.[2][1][18]

The reaction begins when silver abstracts sulfur from S4N4 to produce a Ag2S catalyst; the resulting gaseous S2N2 is then isolated through sublimation onto a cold surface:

S4N4 + 8 Ag → 4 Ag2S + 2 N2
S4N4 (low-pressure gas at 250-300 °C; Ag2S catalyst) → 2 S2N2 (gas) → 2 S2N2 (stable solid at 77 K)

When warmed to room temperature, the additional heat induces spontaneous polymerization:

S2N2 (0 °C) → (SN)x

Uses

Due to its electrical conductivity, polythiazyl is used in LEDs, transistors, battery cathodes, and solar cells.[18]

Literature

King, R.S.P.: Novel chemistry and applications of polythiazyl, Doctoral Thesis Loughborough University 2009, pdf-Download

References
  1. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 725–727. ISBN 978-0-08-037941-8.
  2. Goehring, Margot; Voigt, Dietrich (1953). "Über die Schwefelnitride (SN)2 und (SN)x". Die Naturwissenschaften (in German). 40 (18): 482. Bibcode:1953NW.....40..482G. doi:10.1007/BF00628990. ISSN 0028-1042. S2CID 8181710.
  3. Labes, M. M.; Love, P.; Nichols, L. F. (1979). "Polysulfur Nitride - a Metallic, Superconducting Polymer". Chemical Reviews. 79 (1): 1–15. doi:10.1021/cr60317a002.
  4. Harry R. Allcock (20 September 2011). Introduction to Materials Chemistry. John Wiley & Sons. p. 131. ISBN 978-1-118-21098-7. Retrieved 29 June 2012.
  5. A. G. MacDiarmid; C. M. Mikulsk; A. J. Heeger; A. F. Garito (1983). "Polymeric Sulfur Nitride (Polythiazyl), (SN) X". Polymeric Sulfur Nitride (Polythiazyl), (SN)x. Inorganic Syntheses. Vol. 22. pp. 143–149. doi:10.1002/9780470132531.ch31. ISBN 9780470132531.
  6. Burt, Frank Playfair (1910). "XCIX.—A new sulphide of nitrogen". J. Chem. Soc., Trans. 97: 1171–1174. doi:10.1039/CT9109701171. ISSN 0368-1645.
  7. Labes, M.M.; Love, P.; Nichols, L.F.: Polysulfur nitride - a metallic, superconducting polymer in Chem. Rev. 79 (1979) 1–15, doi:10.1021/cr60317a002.
  8. Alsfasser, R.; Janiak, C.; Klapötke, T.M.; Meyer, H.-J.: Moderne Anorganische Chemie, Herausgeber Riedel, E., 3. Auflage 2007, Walter de Gruyter GmbH & Co. KG, Berlin/Boston, ISBN 978-3-11-019060-1, S. 129–132, (retrieved via De Gruyter Online).
  9. MacDiarmid, A.G.; Mikulski, C.M.; Saran, M.S.; Russo, P.J.; Cohen, M.J.; Bright, A.A.; Garito, A.F.; Heeger, A.J.: Synthesis and Selected Properties of Polymeric Sulfur Nitride, (Polythiazyl), (SN)x in Advances in Chemistry 150 (2009) 63–72, doi:10.1021/ba-1976-0150.ch006.
  10. Entry on Schwefel-Stickstoff-Verbindungen. at: Römpp Online. Georg Thieme Verlag, retrieved 2 March 2017.
  11. Wiberg, E.; Wiberg, N.; Holleman, A.F.: Anorganische Chemie, 103. Auflage, 2017 Walter de Gruyter GmbH & Co. KG, Berlin/Boston, ISBN 978-3-11-026932-1, S. 681, (retrieved via De Gruyter Online).
  12. Baughman, R.H.; Apgar, P.A.; Chance, R.R.; MacDiarmid, A.G.; Garito, A.F.: A New Phase of (SN)x in J. Chem. Soc. Chem. Comm. 1977, 49–50, doi:10.1039/C39770000049.
  13. Goehring, Margot (1956). "Sulphur nitride and its derivatives". Quarterly Reviews, Chemical Society. 10 (4): 437. doi:10.1039/qr9561000437. ISSN 0009-2681.
  14. Cohen, M.J .; Garito, A. F.; Heeger, A. J.; MacDiarmid, A. G.; Mikulski, C. M.; Saran, M. S.; Kleppinger, J. (1976). "Solid state polymerization of S2N2 to (SN)x". Journal of the American Chemical Society. 98: 3844–3848. doi:10.1021/ja00429a018.
  15. Okada, M.; Tanaka, K.; Takata, A.; Yamabe, T. (1993). "Examination of Electronic Phase of the Hartree-Fock Solution of an Isolated Polythiazyl Chain". Synthetic Metals. 59 (2): 223–230. doi:10.1016/0379-6779(93)91029-2.
  16. Boudeulle, M.: in Cryst. Struct. Comm. 4 (1975) 9–13.
  17. MacDiarmid, A.G.; Mikulski, C.M.; Russo, P.J.; Saran, M.S.; Garito, A.F.; Heeger, A.J.: Synthesis and structure of the polymeric metal, (SN)x, and its precursor, S2N2 in J. Chem. Soc. Chem. Comm. 1975, 476–477, doi:10.1039/C39750000476.
  18. Ronald D. Archer (26 February 2001). Inorganic and Organometallic Polymers. John Wiley & Sons. p. 213. ISBN 978-0-471-24187-4. Retrieved 29 June 2012.
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