A Three-Dimensional Synthetic Metallic Crystal Composed of Single-Component Molecules

Abstract

Molecular metals normally require charge transfer between two different chemical species. We prepared crystals of [Ni(tmdt)2] (tmdt, trimethylenetetrathiafulvalenedithiolate) and carried out crystal structure analyses and resistivity measurements. The analyses and measurements revealed that these single-component molecular crystals are metallic from room temperature down to 0.6 kelvin. Ab initio molecular orbital calculations suggested that pi molecular orbitals form conduction bands. The compact molecular arrangement, intermolecular overlap integrals of the highest occupied and lowest unoccupied molecular orbitals, and tight-binding electronic band structure calculation revealed that [Ni(tmdt)2] is a three-dimensional synthetic metal composed of planar molecules.

Variety of valence bond states formed of frustrated spins on triangular lattices based on a two-level system Pd(dmit)2

“…The spectral evidence for the HOMO-LUMO interchange scheme suggests that the unit dimer [Pd(dmit) 2 ] − 2 is potentially a multi-carrier system having two electrons in b-LUMO and one hole in a-HOMO levels [13]. The situation is somewhat similar to that in the single-component molecular metal Ni(tmdt) 2 having electron-like and hole-like Fermi surfaces [27][28][29][30], though the b-LUMO (filled band) electrons in Z [Pd(dmit) 2 ] 2 are completely paired in the dimer. In Z [Pd(dmit) 2 ] 2 , only the a-HOMO hole band is partially filled.…”

“…From a quantum chemical viewpoint, the HOMO-LUMO interchange is based not only on the strong dimerization but also on the symmetries of HOMO and LUMO, which are characteristic of the metal-dithiolene complexes [3]. The material design inspired by these features has been developed; it leads to the single-component molecular metals based on Ni(tmdt) 2 (tmdt = trimethylenetetrathiafulvalenedithiolate) [27]. In this case, the small HOMO-LUMO energy gap makes efficient HOMO-LUMO band crossing (hybridization) so as to form multiple Fermi surfaces stabilising metallic state [28][29][30].…”

Ab initio derivation of multi-orbital extended Hubbard model for molecular crystals

“…Among these singlecomponent molecular solids, the metallic behavior was first confirmed in [Ni(tmdt) 2 ]. 17,18 In [Au(tmdt) 2 ], antiferromagnetic ordering was observed with high transition temperature T AF = 110 K. [19][20][21] Interestingly, it has been proposed that in [Au(tmdt) 2 ], a new type of antiferromagnetic state, called the intra-molecular antiferromagnetic (IAF) state, is realized, in which two ligands within each molecule have opposite spins. 22,23 From DFT-based ab initio calculations for these compounds, several MOs are shown to contribute to the conduction band of the crystal systems.…”

Hydrogen bond-promoted metallic state in a purely organic single-component conductor under pressure

“…On the basis of the latter (ii), the nickel complex, [Ni(tmdt) 2 ] (tmdt, trimethylenetetrathiafulvalene dithiolate), has been synthesized as the first singlecomponent molecular metal. In this material, conductive p electrons delocalize over the tetrathiafulvalene (TTF)-type large ligand skeleton, and as a result, the HOMO-LUMO gap is made smaller 1 . Subsequently, such single-component molecular conductors composed of metal complexes have been intensively developed [2][3][4][5][6][7] .…”