Structure and properties of some new dihydropyrazine–tetracyanoquinodimethane charge transfer salts

Abstract

Rapid crystallization of acetonitrile solutions containing 4a,8a-diaza-2,6-dioxa-3,4,7,8-tetrahydro-4,4,8,8-tetramethylanthracene-1,++5-dione (DDTTA) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) results in two new polymorphs of the previously reported charge transfer salt DDTTA(TCNQ)_2.The first of these {β-[DDTTA(TCNQ)₂ ]} crystallizes in the space group P2₁ /c with cell dimensions a=15.04(2), b=6.953(7), c=16.22(2) Å, beta;=99.4(1)°. The structure of the second polymorph {γ-[DDTTA(TCNQ)₂ ]} could not be determined as a result of small crystal size. The new donor, 2,4,4,6,8,8-hexamethyl-2,4a,6,8a-tetraaza-3,4,7,8-tetrahydroanthracene-1,++5-dione (HTTA) also forms a charge transfer salt with TCNQ of composition HTTA·TCNQ·CH₃CN. This salt crystallizes in the space group P2₁ /c with a=8.973(1), b=22.907(4), c=14.048(2) Å, β=96.69(1)°. The magnetic susceptibility of the three new materials and the originally reported structure {α-[DDTTA(TCNQ)₂ ]} was recorded as a function of temperature. Ferromagnetic exchange is observed between DDTTA cations in α-[DDTTA(TCNQ)₂ ] as a result of the molecular alignment brought about by hydrogen bonding. Hydrogen bonding between cations is also observed in HTTA·TCNQ·CH₃CN; however, a slightly different orientation results in weak antiferromagnetic exchange between cations. β-[DDTTA(TCNQ)₂ ] and γ-[DDTTA(TCNQ)₂ ] also show overall antiferromagnetic exchange. In the DDTTA salts, the TCNQ anions are arranged in stacks resulting in semiconducting behavior. In the α and β phases these stacks are dimerized whereas the magnetic susceptibility of the γ phase suggests the stack is tetramerized. In HTTA·TCNQ·CH₃CN the TCNQ anions are arranged in discrete dimers.

References

1. J. A. Zerkowski, C. T. Seto and G. M. Whitesides, J. Am. Chem. Soc., 1992, 114, 5473.
2. R. J. J. Visser, J. L. De Boer and A. Vos, Acta Crystallogr. Sect. B, 1993, 49, 859.
3. D. J. R. Brook, R. C. Haltiwanger and T. H. Koch, J. Am. Chem. Soc., 1991, 113, 5910.
4. D. J. R. Brook, R. C. Haltiwanger and T. H. Koch, J. Am. Chem. Soc., 1992, 114, 6017.
5. D. J. R. Brook, B. Noll and T. H. Koch, J. Chem. Soc., Perkin Trans 1, in the press.
6. J. S. Chappell, A. N. Bloch, W. A. Bryden, M. Maxfield, T. O. Poehler and D. O. Cowan, J. Am. Chem. Soc., 1981, 103, 2442.
7. V. Zelezny, J. Petzelt and R. Swietlik, Phys. Status Solidi B, 1987, 140, 595.
8. G. A. Sawatsky, S. Huizinga, J. Kommandeur, K. Kopinga and W. J. M. de Jonge, in Quasi One-Dimensional Conductors 2, ed. S. Barisic, A. Bjelis, J. R. Cooper and B. Leontic, Springer Verlag, Berlin, 1979.
9. G. A. Sawatsky, S. Huizinga and J. Kommandeur, in Quasi One-Dimensional Conductors 2, ed. S. Barisic, A. Bjelis, J. R. Cooper and B. Leontic, Springer Verlag, Berlin, 1979.
10. K. Yakushi, M. Iguchi, G. Katagiri, T. Kusaka, T. Ohita and H. Kuroda, Bull. Chem. Soc. Jpn., 1981, 54, 348.
11. R. L. Carlin, Magnetochemistry, Springer Verlag, Berlin, 1986.
12. D. B. Tanner, J. S. Miller, M. J. Rice and J. J. Ritsko, Phys. Rev. B, 1980, 21, 5835.
13. D. Gatteschi and R. Sessoli, Magn. Reson. Rev., 1990, 15, 1.
14. W. E. Hatfield, J. Appl. Phys., 1981, 52, 1985.
15. T. Smith and J. Friedberg, Phys. Rev., 1968, 176, 660.