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Abstract: This paper reports on organic field effect transistors (OFETs) based on two π-conjugated oligomers derived from thiophenes and their use as sensors for the detection of 2,4-dinitrotoluene (DNT). The detection mechanism relies on donor-acceptor interactions between the π-conjugated system (donor) and the nitrated molecule (acceptor). An important feature of sensors is the stability under operation, so, a large part of this work will be dealing with the behavior of OFETs under bias stress experiments as well as with the influence of temperature during operation. Most of results reported here are concerning hexyl capped tetra Thienylene–Vinylene (denominated 4-TV). Some preliminary results on the promising hexyl capped quinquethiophene derived from 3,4-ethylenedioxythiophene (denominated TETET) are also reported. Under a DNT contaminated air atmosphere (∼7 ppm), 4-TV based OFETs exhibit an increase of the drain current when DNT is present in the atmosphere as expected. [Copyright &y& Elsevier]

Abstract: We report on a density functional theory and spectroscopic study of a π-conjugated push–pull chromophore with second order nonlinearities, 5-[1,3-bis(dicyanomethylidene)indan-2-ylidenemethyl]-5′-[(E)-4-N,N-dimethylaminobenzylidene)methyl]-2,2′-bithiophene. The effects of the intramolecular charge transfer (ICT) from the donor to the acceptor groups on the molecular geometry and atomic charge distribution of this NLO-phore are derived from its DFT//B3LYP/6-31G* minimum-energy structure and Natural Population Analysis. The optical absorptions of this chromophore in the UV–Vis spectral region are analyzed with the help of TDDFT//B3LYP/6-31G* calculations of one-electron vertical excitations and of the DFT//B3LYP/6-31G* topologies of the relevant molecular orbitals. The main infrared and Raman features of the NLO-phore are also analyzed by performing DFT//B3LYP/3-21G* vibrational calculations. The great resemblance, in peak positions and relative intensities, between the infrared and Raman spectra of this compound reveals that it really behaves as an efficient push–pull system. [Copyright &y& Elsevier]