Structural Substituent Effect in the Excitation Energy of a Chromophore: Quantitative Determination and Application to S-Nitrosothiols

A methodology for the prediction of excitation energies for substituted chromophores on the basis of ground state structures has been developed. The formalism introduces the concept of ?structural substituent excitation energy effect? for the rational prediction and quantification of the substituent effect in the excitation energy of a chromophore to an excited electronic state. This effect quantifies exclusively the excitation energy variation due to the structural changes of the chromophore induced by the substituent. Therefore, excitation bathochromic and hypsochromic shifts of substituted chromophores can be predicted on the basis of known ground and excited potential energy surfaces of a reference unsubstituted chromophore, together with the ground state minimum energy structure of the substituted chromophore. This formalism can be applied if the chemical substitution does not affect the nature of the electronic excitation, where the substituent effect can be understood as a force acting on the chromophore and provoking a structural change on it. The developed formalism provides a useful tool for quantitative and qualitative determination of the excitation energy of substituted chromophores and also for the analysis and determination of the structural changes affecting this energy. The proposed methodology has been applied to the prediction of the excitation energy to the first bright state of several S-nitrosothiols using the potential energy surfaces of methyl-S-nitrosothiol as a reference unsubstituted chromophore.Ministerio de Ciencia e InnovaciónUniversidad de Alcal

Organic Semiconductors

One of the most exciting opportunities in electronics, optoelectronics or flexible electronics is to be able to make devices based on organic semiconductors. Organic active materials can exhibit many advantages such as lower demands on processing technology with less sensitivity to the processing environment, flexibility, and the opportunity to apply the simplicity of organic synthesis to tailoring the properties of the materials for specific applications [1]. Depending on their vapor pressure and solubility, organic semiconductors are deposited either from a vapor or solution phase. In this section, some of the organic semiconductor deposition methods are discussed. Similar to its inorganic counterparts, organic semiconductors have been the subject of extensive research to produce organic electronic devices such as organic photovoltaic cells (OPV), organic field-effect transistors (OFET), and organic lightemitting diodes (OLED) [2, 3, 73–77, 82]. However, organic semiconductors have certain limitations such as a short lifetime, degradation byUVlight, temperature sensitivity, low efficiency compared to inorganic semiconductors, and not well understood charge transfer mechanisms. Despite these limitations, advantages like their lightweight, transparency, flexibility, and lower production cost make them candidates for the development of novel electronic devices fomenting research in this area. It is worthwhile to note that organic semiconductors have been combined with other carbon nanomaterials like carbon nanotubes, fullerenes, and graphene, to improve their charge carrier mobility, which is one of the limitations of polymers and oligomers