TY - JOUR
T1 - Polymorphism and Alloys in the Bis(ethylenedithio)tetrathiafulvalene/M(CN)42- Radical Cation Salts. Structural and Physical Properties of α,δ-(ET)4[Ni(CN)4][Pt(CN)4]1-x(H2O)n
AU - Fettouhi, M.
AU - Ouahab, L.
AU - Grandjean, D.
AU - Ducasse, L.
AU - Amiell, J.
AU - Canet, R.
AU - Delhaes, P.
PY - 1995/3
Y1 - 1995/3
N2 - The synthesis and structural and physical properties of some radical cation salts based on bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and tetracyanometallates M(CN)42- (M = Pt(II) and Ni(II)) are reported. The salts (ET)4[Ni(CN)4L[PtiCN)4]1-x(H2O)n (at x= 0-1; n= 0-4) have been isolated with different principal packing modes, in particular the a and ó types. In both cases the structures consist of alternating layers of organic cations and inorganic anions, and two different kinds of packing, namely, a4 and ci2, have been observed in the case of the a type structure. The organic sublattice in the, salts is built of two independent chains, while only one type of dimerized chain is observed in the 012 modification. The δ phase is originated from an independent and strongly dimerized one-dimensional stack. All materials are conductors at ambient temperature and exhibit a semiconducting behavior upon cooling. For the α1 phase the spin susceptibility and the ESR line widths decrease with temperature, giving rise to two anomalies respectively at about 200 and 20 K. The 0.2 type shows a classical Currie-Weiss low-T 1dependence of the spin susceptibility with a Weiss temperature θ= -25 K, characteristic of weak antiferromagnetic interactions. In the case of the δ type a strong decrease of the spin susceptibility at about 180 K reminiscent of a Peierls-type transition is observed. The band calculations (EHT model) agree with the observed ambient temperature conducting behavior for both α and δ phases. The nesting of the Fermi surface for the latter type might be related to the occurrence of a structural phase transition. In the absence of nesting for the α1 type, an alternative mechanism based on the alternation of electronic densities on the different intermolecular bonds (bond order wave) is proposed to explain the observed electronic localization at low temperature. Finally a general description of the polymorphism encountered with their related structural organization is proposed.
AB - The synthesis and structural and physical properties of some radical cation salts based on bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and tetracyanometallates M(CN)42- (M = Pt(II) and Ni(II)) are reported. The salts (ET)4[Ni(CN)4L[PtiCN)4]1-x(H2O)n (at x= 0-1; n= 0-4) have been isolated with different principal packing modes, in particular the a and ó types. In both cases the structures consist of alternating layers of organic cations and inorganic anions, and two different kinds of packing, namely, a4 and ci2, have been observed in the case of the a type structure. The organic sublattice in the, salts is built of two independent chains, while only one type of dimerized chain is observed in the 012 modification. The δ phase is originated from an independent and strongly dimerized one-dimensional stack. All materials are conductors at ambient temperature and exhibit a semiconducting behavior upon cooling. For the α1 phase the spin susceptibility and the ESR line widths decrease with temperature, giving rise to two anomalies respectively at about 200 and 20 K. The 0.2 type shows a classical Currie-Weiss low-T 1dependence of the spin susceptibility with a Weiss temperature θ= -25 K, characteristic of weak antiferromagnetic interactions. In the case of the δ type a strong decrease of the spin susceptibility at about 180 K reminiscent of a Peierls-type transition is observed. The band calculations (EHT model) agree with the observed ambient temperature conducting behavior for both α and δ phases. The nesting of the Fermi surface for the latter type might be related to the occurrence of a structural phase transition. In the absence of nesting for the α1 type, an alternative mechanism based on the alternation of electronic densities on the different intermolecular bonds (bond order wave) is proposed to explain the observed electronic localization at low temperature. Finally a general description of the polymorphism encountered with their related structural organization is proposed.
UR - https://www.scopus.com/pages/publications/0001266296
U2 - 10.1021/cm00051a005
DO - 10.1021/cm00051a005
M3 - Article
AN - SCOPUS:0001266296
SN - 0897-4756
VL - 7
SP - 461
EP - 471
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 3
ER -