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Band-structure calculations, semiempirical as well as ab initio, have been applied to study the electronic band gap of the new exotic natural low-dimensional MX systems (where M = Pb or Sn and X = I, Br or Cl). Moreover, variational calculations are employed to calculate the excitonic binding energies, whose amplification is due not only to the quantum confinement of the excitons but also to a dielectric enhancement effect. A single set of semiempirical parameters is sought to describe the materials; comparison of the calculations with experimental data shows this to be successful in the case of the PbI- and PbBr-containing compounds. .

The authors report on ambipolar organic transistors based on the soluble dithiolene derivative ͑diphenylethylenedithiolato͒͑1,3-dithiol-2-thione-4,5-dithiolato͒nickel ͓Ni͑dpedt͒͑dmit͔͒. Due to its small band gap, efficient injection of holes and electrons from gold source/drain electrodes is possible. Both carrier mobilities are estimated to be approximately equal with maximum value on the order of 10 −4 cm 2 / V s. The transistors exhibit excellent ambient stability with a shelve lifetime exceeding 3 months. The pronounced stability of Ni͑dpedt͒͑dmit͒ as well as of several other molecules studied here is correlated to their redox potential. The present findings can be used as a general guide towards design and synthesis of air-stable ambipolar/n-channel molecules.

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On page 1223, first paragraph, the values for the theoretically estimated binding energy, Bohr radius and Eb(2D) should be 285 meV, 11.5 Å and 9.82 Eb(3D), rather than 191 meV, 14.2 Å and 6.58 Eb(3D), respectively.

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