Ni(dmit)(2) salts with chiral stilbazolium- and ferrocenyl-based chromophores as countercations

Four 1:1, two-component salts combining the [Ni(dmit)(2)](-) anion (dmit(2- ) = 2-thioxo-1,3-dithiole-4,5-dithiolato) and chiral stilbazolium-based cou ntercations (HPMS+ = 4'-[2-(hydroxymethyl)pyrrolidinyl]-1-methylstilbazoliu m and MPMS+ = 4'- [2-(methoxy-methyl)pyrrolidinyl]-1-methylstilbazolium), o r chiral ferrocenyl-based countercations (2(+) = (E)-1-((R)-2-methylferroce nyl)-2-(1-methyl-4-pyridiniumyl)ethene; 3(+) = (E)-1-((S)-2-trimethylsilylf errocenyl)-2-(1-methyl-4-pyridiniumyl)ethene) were prepared. Semiconducting behaviour (2.10(-4) S.cm(-1) measured on compressed pellets for [Ni(dmit)( 2)] (MPMS), for example) is secured by the presence of the [Ni(dmit)(2)]- a nions. The chiral nature of the countercations ensures non-centrosymmetry o f the structures (space group P1 for [Ni(dmit)(2)](2) and [Ni(dmit)(2)](3), for example). A ubiquitous antiparallel arrangement of the cations, which are thus packed in a pseudo-centrosymmetrical environment, results in almos t vanishing second-order susceptibilities chi((2)), and therefore zero effi ciencies in second harmonic generation. (C) Academie des sciences/Elsevier, Paris.