Neutral, closed-shell nickel bis(2-alkylthio-thiazole-4,5-dithiolate) complexes as single component molecular conductors

Abstract

Neutral nickel bis(dithiolene) complexes, because of their closed-shell character, are usually considered as insulating materials, unless they are formed out of highly delocalized tetrathiafulvalenedithiolate ligands. We describe here an original series of S-alkyl substituted neutral bis(thiazole-4,5-dithiolate) nickel complexes formulated as [Ni(RS-tzdt)2] (R = Me, Et), which organize in the solid state into uniform stacks and exhibit semiconducting behavior, with room temperature conductivities comparable to those reported in the prototypical [Ni(dmit)2] and [Ni(Et-thiazdt)2] neutral complexes. These findings provide new perspectives in the current search for single component molecular conductors.

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

“…80 In [Ni(RS-tzdt) 2 ] (R: Me, Et) a semiconducting behaviour was observed, with s RT ranging between 5 Â 10 À7 -5 Â 10 À6 S cm À1 and between 10 À4 -10 À5 S cm À1 for the Me and Et substituted complexes, respectively. 81 The gold and nickel complexes of [M(EtOHS-tzdt) 2 ] were found to be isostructural presenting uniform stacks and strong O-HÁ Á ÁN hydrogen bonds (1.968 Å for the Ni complex and 2.065 Å for the Au complex) between molecules in neighbouring stacks. The hydrogen bonds control the overall crystal structures regardless of their different open/closed shell nature.…”

Hydrogen bonding interactions in single component molecular conductors based on metal (Ni, Au) bis(dithiolene) complexes

“…The synthesis of 2-(hydroxyethylthio)-1,3-thiazole-4,5-dithiolene proligand 2 involves the reaction of 1 in the presence of an excess of 2-iodoethanol. This original transformation, first discovered with simple alkylating reagents such as MeI or EtI, 42 has been successfully extended here to 2-iodoethanol. When the reaction was performed in refluxing dichloromethane, as previously described with MeI and EtI, the proligand 2 was obtained in very low yield (7%) only.…”

“…Deprotection of the proligand 2 in the presence of sodium methanolate, followed by the addition . 42 A complex set of hydrogen bonds (Fig. 1) takes place in the crystal, whose structural characteristics are collected in Table 1.…”