Investigation of the Redox Properties of a Cp*Co(dithiolene) Complex. Evidence of the Formation of a Dimeric Dicationic Species: [Cp*Co(dddt)]22+

Molecular and thin film properties of cobalt half-sandwich compounds for optoelectronic application

The structure and electronic properties of a novel cobalt half sandwich complex of cyclopentadiene (Cp) and diaminonaphthalene (DAnap) [CpCo(DAnap)] are described and compared to the previously reported diaminobenzene derivative [CpCo(DAbnz)] in view of their potential for (opto)electronic device application. Both complexes show stable redox processes, tunable through the diaminoacene ligand, and show strong absorption in the visible region, with additional transitions stretching into the near infrared (NIR). CpCo(DAnap) crystallises with a particularly large unit cell (9301 ų), comprising 32 molecules, with a gradual rotation over 8 molecules along the long c-axis. In the solid state the balance of the optical transitions in both complexes is reversed, with a suppression of the visible band and an enhancement of the NIR band, attributed to extensive intermolecular electronic interaction. In the case of CpCo(DAnap), highly crystalline thin films could be formed under physical vapor deposition, which show a photocurrent response stretching into the NIR, and p-type semiconductor behavior in field effect transistors with mobility values of the order 1 × 10^-4 cm² V^-1 s^-1. The device performance is understood through investigation of the morphology of the grown films.

[CpNi(dithiolene)] (and Diselenolene) Neutral Radical Complexes

Various preparations of the neutral radical [CpNi(dddt)] complex (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate) were investigated with CpNi sources, [Cp2Ni], [Cp2Ni](BF4), [CpNi(CO)]2, and [CpNi(cod)](BF4), and dithiolene transfer sources, O=C(dddt), the naked dithiolate (dddt(2-)), the monoanion of square-planar Ni dithiolene complex (NBu4)[Ni(dddt)2], and the neutral complex [Ni(dddt)2]. The reaction of [CpNi(cod)](BF4) with (NBu4)[Ni(dddt)2] gave the highest yield for the preparation of [CpNi(dddt)] (86%). [CpNi(ddds)] (ddds = 5,6-dihydro-1,4-dithiin-2,3-diselenolate), [CpNi(dsdt)] (dsdt = 5,6-dihydro-1,4-diselenin-2,3-dithiolate), [CpNi(bdt)] (bdt = 1,2-benzenedithiolate), and [CpNi(bds)] (bds = 1,2-benzenediselenolate) were synthesized by the reactions of [Cp2Ni] with the corresponding neutral Ni dithiolene complexes [Ni(ddds)2]2, [Ni(dsdt)2], [Ni(bdt)2], and [Ni(bds)2], respectively. The five, formally Ni(III), radical complexes oxidize and reduce reversibly. They exhibit, in the neutral state, a strong absorption in the NIR region, from 1000 nm in the dddt/ddds/dsdt series to 720 nm in the bdt/bds series with epsilon values between 2500 and 5000 M(-1) cm(-1). The molecular and solid state structures of the five complexes were determined by X-ray structure analyses. [CpNi(dddt)] and [CpNi(ddds)] are isostructural, while [CpNi(dsdt)] exhibits a closely related structure. Similarly, [CpNi(bdt)] and [CpNi(bds)] are also isostructural. Correlations between structural data and magnetic measurements show the presence of alternated spin chains in [CpNi(dddt)], [CpNi(ddds)], and [CpNi(dsdt)], while a remarkably strong antiferromagnetic interaction in [CpNi(bdt)] and [CpNi(bds)] is attributed to a Cp...Cp face-to-face sigma overlap, an original feature in organometallic radical complexes.

Paramagnetic cp/dithiolene complexes as molecular hinges: interplay of metal/ligand electronic delocalization and solid-state magnetic behavior

Paramagnetic, flexible organometallic dithiolene complexes associating cyclopentadienyl (Cp) and dithiolate (dt) ligands, such as CpM(dt), Cp2M(dt), or CpM(dt)2, are investigated in the solid state through their structural and magnetic properties. The degree of delocalization of the spin density between the metal and the dithiolene fragments in a given complex, its varying molecular geometry and frontier orbitals, and the structures adopted in the solid state are intimately correlated and adapt mutually to each other. A variety of magnetic structures follows, from noninteracting spins to dyads, spin chains, spin ladders, or antiferromagnetic ground state, the detailed properties of which are highly sensitive to "minor" molecular modifications.