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 π 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.

https://science.sciencemag.org/content/sci/291/5502/285.full.pdf

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

Many kinds of radicals are stable enough to isolate, handle, and store without any special precautions. The diversity in molecular architectures of these stable radicals is sufficiently large that the common factors governing radical stability/persistence, geometric and electronic structure, association/dimerization preferences, and reactivity have generally not been well articulated or appreciated. This review provides a survey of the major classes of stable or persistent organic/organomain group radicals with a view to presenting a unified description of the interdependencies between radical molecular structure and properties.

What's new in stable radical chemistry?

Single-component molecular metals with extended-TTF dithiolate ligands.

http://lib.fibopt.ru/Articles/PAPER/Elsevier/CCRev-2007-251-1007.pdf

Stretching bonds in main group element compounds—Borderlines between biradicals and closed-shell species

This review describes recent advances in the development of thiazyl radicals, particularly dithiadiazolyl (RCNSSN) and dithiazolyl (RCSNSCR) as molecule-based materials. Particular emphasis is placed on their potential applications as molecular conductors, magnets and switchable materials and incorporates an overview of the structure–property relationships required in these molecular systems.

Thiazyl radicals: old materials for new molecular devices

The preparation and purification of the heterocyclic diradical benzo-1,2:4,5-bis(1,3,2-dithiazolyl) (BBDTA) is described. Crystals of BBDTA, grown by fractional sublimation at 120-180 °C/10-3 Torr, are monoclinic, space group P21/c, with a ) 4.144(2), b ) 9.0344(13), and c ) 10.7424(16) A,‚ ) 91.11(3)°, and Z ) 2. The crystal structure consists of discrete, unassociated molecules of BBDTA. The molecules form slipped stacks along the x direction, with the mean molecular plane making an angle of 32.4° to the x axis. The interplanar separation between consecutive molecules along the stacking direction is 3.49 A. The ESR spectrum of BBDTA is solvent dependent, displaying signals attributable to partially associated materials ( not exchange coupled) and to free diradical (exchange coupled). Ab initio molecular orbital calculations suggest a small (ca. 0.5 kcal/mol) separation between the triplet and singlet diradical states. Cyclic voltammetry on BBDTA and the related benzo-1,3,2-dithiazolyl BDTA, coupled with gas phase photoelectron studies on BDTA, establish that both compounds are strong electron donors. Magnetic susceptibility measurements show that BBDTA is essentially diamagnetic up to room temperature; variable temperature single-crystal conductivity measurements provide a band gap of 0.22 eV. The transport properties are discussed in the light of extended Huckel band structure calculations, which suggest a highly three-dimensional electronic structure for bulk BBDTA in the solid state.

https://pure.rug.nl/ws/files/3624920/1997JAmChemSocBarclaySupp.pdf

R.H. de Laat

Papers

The heterocyclic diradical benzo-1,2:4,5-bis(1,3,2-dithiazolyl). electronic, molecular and solid state structure