Optimization of crystal packing in semiconducting spin-crossover materials with fractionally charged TCNQ^δ− anions (0 < δ < 1)

Abstract

Co-crystallization of the prominent Fe(II) spin-crossover (SCO) cation, [Fe(3-bpp)2]2+ (3-bpp = 2,6-bis(pyrazol-3-yl)pyridine), with a fractionally charged TCNQδ- radical anion (0 &lt; δ &lt; 1) has afforded a hybrid complex [Fe(3-bpp)2](TCNQ)3·5MeCN...

Co-crystallisation as a modular approach to the discovery of spin-crossover materials

“…18,19,30 In some cases, for example, when TCNQ dÀ was used, additional properties such as (semi)conducting behaviour have been achieved. [31][32][33][34][35][36][37][38] However, examples of ionic SCO-cocrystals are oen highly solvated, and difficulties with reproducibility and elucidation of structureproperty correlations have been associated with desolvation effects. The use of neutral rather than charged molecules would allow the incorporation of a much wider range of coformers to be employed, increasing the modularity of the approach.…”

Electronic structure of cobalt valence tautomeric molecules in different environments

“…[24][25][26][27][28] The conductivity of Fe(II)based SCO systems can be further enhanced by adding organic semiconducting polymers, such as polyaniline (PANI) and polar poly-D-lysine (PDL), 28,29 and select molecules. [30][31][32][33][34][35][36][37] Even interfaces can improve conductivity and mobility within adjacent SCO layers and it is likely that this also holds for valence tautomeric films.…”

Structural and Magnetic Investigation of Cobalt Valence Tautomeric Complexes with Sulfur-Containing Ligands

“…Molecular conductors with switchable magnetic responses hold potential for application in data processing and storage devices. − In this vein, spin crossover (SCO) complexes, which show switching between high-spin (HS) and low-spin (LS) electronic configurations under changes in temperature, pressure, or photoexcitation, have been extensively investigated as switchable molecular conductors. ,− A most common way to achieve the combination of SCO with electrical conductivity is to cocrystallize SCO complexes with suitable organic donor or acceptor fragments, such as tetrathia­fulvalene (TTF), − 7,7′,8,8′-tetracyano­quino­dimethane (TCNQ), − or [M­(dmit) 2 ] n − (dmit = 4,5-dithiolato-1,3-dithiol-2-thione). − For example, our group and others reported several hybrid materials that combine cationic SCO complexes with partially charged TCNQ δ− anions. − ,− Such complexes displayed gradual temperature-induced SCO, as well as a light-induced excited spin-state trapping (LIESST) effect, and appreciable conductivity, up to 0.2 S/cm at 300 K . An intriguing approach to combining spin-state switching and conductivity in the same material was proposed by Galán-Mascarós et al, who reported SCO-induced changes in conductivity of conjugated polymers loaded with SCO nanoparticles. , …”