Metal Bis Dithiolene Complexes Research Articles

Complexes with pyrazine-tetrathiafulvalene-dithiolate (pztdt) ligand [M(pztdt)2], M = Ni, Pd, Pt; Synthesis and characterisation

The synthesis and characterisation of three metal bisdithiolene complexes based on the recently reported highly extended ligand incorporating fused tetrathiafulvalene and pyrazine moieties, [M(pztdt)2], M=Ni, Pd, Pt and pztdt=pyrazinetetrathiafulvalenedithiolate, are reported. These complexes were obtained under anaerobic conditions as crystals of dianionic tetrabutylammonium salts. The crystal structures of Ni and Pd complexes as determined by single crystal X-ray diffraction confirm the ability of these molecules to established interactions with their neighbours through the pyrazine moieties. These dianionic complexes easily undergo oxidations to their monoanionic and neutral states, with a narrow range of stability for the monoanionic and an extended one for the neutral forms that is rather insoluble in common solvents.

Crystal structures and physical properties of donor type dithiolene complexes with cycloalkane rings

Metal bis-dithiolene complexes have been intensively studied as conducting materials. Among them, acceptor type complexes provide various anion radical salts which exhibit superconducting and metallic behavior. [1] On the other hand, neither a metal nor a superconductor has been obtained from donor type complexes except for a salt of [Ni(dddt)2]. [2] In this work, we examined modification of the dddt complex with terminal cycloalkane rings, and developed [Ni(Cn-dddt)2] (n = 3, 4, 5, 6) to expand the materials chemistry of the donor type complexes. In the crystals of the neutral complexes, the cycloalkane rings exhibited various conformations which would affect physical properties in their cation radical salts. We succeeded in electrochemical crystallization of new cation radical salt [Ni(C3-dddt)2]3(BF4)2. Other salts were also obtained by similar procedures. We will discuss their electrical property of the salts based on the crystal structure.

Transition Metal Bisdithiolene Complexes Based on Extended Ligands with Fused Tetrathiafulvalene and Thiophene Moieties: New Single‐Component Molecular Metals

The gold and nickel bisdithiolene complexes based on new highly extended ligands incorporating fused tetrathiafulvalene and thiophene moieties (alpha-tdt=thiophenetetrathiafulvalenedithiolate and dtdt=dihydro- thiophenetetrathiafulvalenedithiolate), were prepared and characterised by using cyclic voltammetry, single crystal X-ray diffraction, EPR, magnetic susceptibility and electrical transport measurements. These complexes, initially obtained under anaerobic conditions as diamagnetic gold monoanic [nBu(4)N][Au(alpha-tdt)(2)] (4), [nBu(4)N][Au(dtdt)(2)] (3) and nickel dianionic species [(nBu(4)N)(2)][Ni(alpha-tdt)(2)] (8), [(nBu(4)N)(2)][Ni(dtdt)(2)] (7), can be easily oxidised to the stable neutral state just by air or iodine exposure. The monoanionic complexes crystallise in at least two polymorphs, all of which have good cation and anion segregation in alternated layers, the anion layers making a dense 2D network of short SS contacts. All of the neutral complexes, obtained as microcrystalline or quasi amorphous fine powder, present relatively large magnetic susceptibilities that correspond to effective magnetic moments in the range 1-3 mu(B) indicative of high spin states and very high electrical conductivity that in case of the Ni compound can reach sigma(RT) approximately 250 S cm(-1) with a clear metallic behaviour. These compounds are new examples of the still rare single-component molecular metals.

Electrical Conductivity and Spin Crossover: A New Achievement with a Metal Bis Dithiolene Complex

Three new compounds based on the cationic complex [Fe(III)(3-R-salEen)(2)]+ (salEen stands for N-(2-ethylamino)ethyl)-salicylaldimine, R = H, CH(3)O) with the electroactive Ni(dmit)(2) species as a counterion (dmit stands for 1,3-dithia-2-thione-4,5-dithiolato) have been synthesized and structurally and magnetically characterized. Compound 1 ([Ni(dmit)(2)][Fe(3-OMe-salEen)(2)]. CH(3)OH) shows an apparent hysteresis loop, due to an irreversible desolvatation process. Compound 2 ([Ni(dmit)(2)](NO(3))[Fe(salEen)(2)](2)) exhibits a gradual and incomplete spin transition. Compound 3 ([Ni(dmit)(2)](5)[Fe(salEen)(2)](2), 6CH(3)CN) is a fractional oxidation state complex, which behaves like a semiconductor and exhibits a gradual but complete spin transition between 300 and 4 K.

Electrical Conductivity and Spin Crossover: Towards the First Achievement With a Metal Bis Dithiolene Complex

The synthesis, structure, magnetic behavior and electrical conductivity of the system [Fe(sal2trien)][Ni(dmit)2]x have been investigated. The electrocrystallization method used has afforded small amounts of crystalline multi-phase materials. In particular, the complex salt [Fe(sal2trien)][Ni(dmit)2]3 has been unambiguously characterized. Surprisingly, despite it contains the spin crossover cation [Fe(sal2trien)]+, the complex does not exhibit spin transition. Most probably, this fact is related to the structural arrangement of the cationic species, which in addition are strongly disordered. This salt behaves like a semiconductor. A strongly cooperative spin transition accompanied with a hysteresis loop is observed in a still-unknown phase obtained during the preparation of [Fe(sal2-trien)] [Ni(dmit)2]3.

X-ray photoelectron spectra and electrical properties of new metal complexes of [M(DMID)2][TAA

Abstract X-ray photoelectron spectroscopy (XPS) spectra of a series of metal complexes of the DMID ligand [M(DMID) 2 ][TAA] x . (DMID=1,3- dithiole-2-one-4,5-dithiolate, MNi, Cu, Zn; TAA = tetraalkylammonium, such as tetrabutylammonium (TBA), tetraethylammonium (TEA), and tetramethylammonium (TMA); X = integer or non-integer) were studied by comparing with other metal bisdithiolene complexes. The XPS results show that in the metal-DMID complexes the formal oxidation states of the central chelating metal ion are in the valence states of 3+ with the extra negative charge residing essentially on the ligands, especially on the sulfur atoms, and the electron density on the sulfur atoms is higher than that in the electron-rich organic donor molecule tetrathiafulvalene (TTF). Electrical properties of these complexes were investigated by conductivity and cyclic voltammetric measurements. Furthermore, the effects of the central metal atoms, counter cations and ligands on the electrical properties and XPS shifts are discussed.

Novel Solid State Materials Derived from Transition Metal Bis-dithiolene Complexes

Abstract The transition metal bis-dithiolene complexes (MS4C4X4) can be used as acceptor molecules in π-donor-acceptor-type compounds, or as radical anions in mixed valence compounds. These compounds are in the wide middle ground between the strictly organic or inorganic molecular solids on which extensive research has led to the discovery of molecular superconductors and to the development of new materials and concepts. Novel solid state materials derived from metal bis-dithiolene complexes also exhibit interesting original physical properties. In the (TTF)[MS4C4(CF3)4] series of compounds, depending on the nature of the metal ion, a wide range of novel magnetic phenomena ranging from bulk ferrimagnetism (M = Ni) to spin-Peierls transition (M = Cu and Au) have been observed. Metal bis-dithiolene complexes have also been used for preparing molecular superconductors such as (TTF)[M(dmit)2]2 and (Me4N)0.5[Ni(dmit)2] (dmit2- = 1,3-dithiol-2-thione-4,5-dithiolate) in which the conduction mechanisms are quite ...