5‐Methylthiophene‐2,3‐dithiolene Transition Metal Complexes

Abstract

Transition metal complexes based on the new ligand 5‐methylthiophene‐2,3‐dithiolate (α‐mtpdt) and Au, Ni, Fe, Co, Cu Pt and Pd were prepared as tetraalkylammonium and tetraarylphosphonium salts and characterised by cyclic voltammetry, X‐ray diffraction, electron paramagnetic resonance (EPR) spectroscopy and magnetic susceptibility measurements. Except for the Cu complex, which forms a four‐metal cluster [Cu4(α‐mtpdt)3]2–, the metals form complexes of the general formula [M(α‐mtpdt)2]. With Au, Ni and Fe, the complexes are directly obtained from the synthesis as monoanionic salts, and the isostructural crystal structures of [nBu4N][Ni(α‐mtpdt)2] and [nBu4N][Au(α‐mtpdt)2] were solved by single‐crystal X‐ray diffraction. For M = Co, Pt and Pd, both monoanionic and dianionic salts were obtained, and the crystal structures of [Ph4As]2[Co(α‐mtpdt)2] and [Ph4As]2[Pd(α‐mtpdt)2] were determined by single‐crystal X‐ray diffraction. The Co compound presents a rare tetrahedral coordination geometry. The oxidation of the monoanionic Ni and Au complexes with iodine leads to stable neutral complexes, which are fairly soluble in common organic solvents such as acetonitrile and dichloromethane. The crystal structure of [Ni(α‐mtpdt)2] was solved by single‐crystal X‐ray diffraction. The electrical conductivities of the neutral Ni and Au complexes as polycrystalline compressed pellets are typical of a semiconductor; the room‐temperature conductivities are 5.2 × 10–7 and 8.7 × 10–5 S cm–1, and the activation energies are 325 and 287 meV, respectively.

TTFs nonsymmetrically fused with alkylthiophenic moieties

“…This is most likely the result of orientation disorder of the molecule in the most stable trans configuration, rather than a cis–trans disorder. The bond lengths are within the expected range for thiophenic dithiol ketones [ 12 , 20 ].…”

“…One of the limitations in the study of these complexes and their possible applications is their low solubility mainly in the neutral state. This limitation can be, in principle, overcome by appropriated functionalization of the ligands as already explored for less extended complexes [ 12 ].…”

The quest for single component molecular metals within neutral transition metal complexes

“…One approach to overcome this drawback is to incorporate solubilizing alkyl chains in the molecular framework. Following this strategy different families of derivatives with a methyl, 68 a tert-butyl 69 and a diisopropyl, 69 in the outer thiophene ring were prepared (Chart 3). The transport properties of [Au(a-mtpdt) 2 ] and [Ni(a-mtpdt) 2 ] (a-mtpdt: 5-methylthiophene-2,3-dithiolate, Chart 3), performed in compressed pellets, revealed in both cases a semiconducting behaviour, with a s RT of 5.2 Â 10 À7 S cm À1 and of 8.7 Â 10 À5 S cm À1 for the nickel and gold complexes, respectively.…”

Broadband near-IR absorbing Au-dithiolene complexes bearing redox-active oligothiophene ligands

“…In both 23TDT and 34TDT further functionalisation of the thiophene moiety can be used to modify and tune the materials' electronic or mechanical properties. Mono- 53 and di-alkyl 54 substituted derivatives of 23TDT have been prepared with a dialkyl substituted complex behaving as a single molecule conductor, while robust synthetic routes have been established for the synthesis of semiconducting π-extended 23TDT ligands bearing aromatic rather than alkyl substituents. 55,56 Our interest in this area involves extending the conjugation length of the 34TDT ligand.…”