Dithiazolodithiazolyl radicals: Substituent effects on solid state structures and properties

作者：Beer L; Britten JF; Clements OP; Haddon RC; Itkis ME; Matkovich KM; Oakley RT^*; Itkis ME

来源：Chemistry of Materials, 2004, 16(8): 1564-1572.

DOI：10.1021/cm035191u

A general synthetic route to the pyridine-bridged dithiazolodithiazolyl framework R(2)BPR(1), involving N-alkylation of a 4-substituted 2,6-dichloropyridine, followed by amination and double Herz cyclization with S(2)Cl(2), has been developed. The radicals R(2)BPMe (R(2) = Me, Ph) have been prepared and characterized by EPR spectroscopy and cyclic voltammetry. Their crystal structures have been determined by X-ray crystallography. Both structures consist of undimerized slipped radical pi-stacks. Lateral interactions in MeBPMe (space group P2(1)/c) generate chainlike arrays with radicals linked by inversion centers; there are no close interchain S-S contacts. By contrast, in PhBPMe (space group P3(1)21) the radical pi-stacks are nested about 3(1) axes, so as to produce an extensive 2-dimensional network of intermolecular S-S interactions. Variable-temperature magnetic susceptibility measurements reveal that MeBPMe is essentially paramagnetic, whereas PhBPMe displays strong antiferromagnetic coupling. A value of J = - 149 cm(-1) has been estimated by using a Bonner-Fisher anti-ferromagnetic chain model. Pressed pellet conductivity measurements indicate values of sigma(RT) approximate to 10(-5) S cm(-1) for both R(2)BPMe compounds (R(2) = Me, Ph), suggesting Mott insulator ground states. The structural results and transport properties are discussed in the light of extended Huckel theory band structure calculations.

• 出版日期2004-4-20