Abstract
The charge transfer salts α-DT-TTF[Au(dcdmp)2] (1), BET-TTF[Au(dcdmp)2] (2M and 2T), α-DT-TTF[Cu(dcdmp)2] (3), ET[Cu(dcdmp)2] (4), (BET-TTF)2[Cu(dcdmp)2] (5), (ET)2[Ni(dcdmp)2] (6), and α-mtdt[Cu(dcdmp)2] (7) were obtained by electrocrystallization of different electron donor molecules derived from TTF (α-DT-TTF = alpha-dithiophene-tetrathiafulvalene; BET-TTF = (bis(ethylenethio)tetrathiafulvalene; ET = bis(ethylenedithio)-tetrathiafulvalene; α-mtdt = alpha-methylthiophenetetrathiafulvalene) in the presence of transition metal complex [M(dcdmp)2] (M = Au (III), Cu (III) and Ni (II)) (dcdmp = 2,3-dicyano-5,6-dimercaptopyrazine). Compounds 1 and 2 (2M and 2T) have a similar packing pattern composed of mixed stacks of alternating donor-acceptor molecules. For (BET-TTF)[Au(dcdmp)2] two different crystal structures (2M and 2T) were obtained indicating polymorphism. Compounds 3 and 4 are isostructural being composed of zigzag chains of alternating donor and acceptor molecules. The salts with a 2:1 stoichiometry, (BET-TTF)2[Cu(dcdmp)2] (5), and (ET)2[Ni(dcdmp)2] (6) present the donor molecules fully oxidized and [M(dcdmp)2] (M = Ni and Cu) in a dianionic state. The salt of the dissymmetric donor α-mtdt with [Cu(dcdmp)2], α-mtdt[Cu(dcdmp)2] (7) has a crystal structure composed of segregated donor stacks that are positioned in a head-to-head fashion and alternate with the anion stacks. All charge transfer salts (1–7) are modest semiconductors with conductivities in the range 10−1–10−5 S/cm, with the highest values obtained in α-DT-TTF salts, compounds 1 and 3.
Highlights
After about 50 years of intensive studies, transition metal bisdithiolene complexes still continue to be actively explored as building blocks for molecular conducting and magnetic materials due to their interesting and unique structural and electronic properties [1]
Some attractive features of these types of complexes are the diversity of coordination geometries that metal centres can adopt, as well as, depending on the transition metal or the oxidation state, the accessibility to several oxidation states and different magnetic moments [2]
Eight new compounds were obtained by electrocrystallization by combining TTF type electronic donors, namely, ET, BET-TTF, α-DT-TTF, and α-mtdt, with transition metal complexes [M(dcdmp)2 ]
Summary
After about 50 years of intensive studies, transition metal bisdithiolene complexes still continue to be actively explored as building blocks for molecular conducting and magnetic materials due to their interesting and unique structural and electronic properties [1]. The square planar coordination geometry and the delocalised π-nature of the ligands favour, in the solid state, the formation of extended networks of π-π interactions, which can give rise to interesting properties such as ferromagnetism [3], spin-ladder behaviour [4,5], and metallic [6,7], or even superconducting, properties [8,9]. Extended dithiolene π-ligands containing N atoms are significantly less explored when compared Crystalsrich. REVIEW to sulphur which have been favoured to build intermolecular S···S contacts with improved dimensionality in the solid state [10]. Extended dithiolene π-ligands containing N atoms are significantly less explored when to act as an extra coordinating site that can provide an additional degree of freedom in the crystal compared to sulphur rich ligands, which have been favoured to build intermolecular S···S contacts engineering of these solids [11]. The N atoms in dithiolene ligands are [M(dcdmp)
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