Abstract:Dedicated to Professor Klaus Weissermel on the occasion of his 60th birthdayBesides its technical meaning, the word "electronics" signifies another industrial revolution. The driving force behind this development is the very rapid progress in the field of integrated semiconductor circuits. An ever-increasing number of structures of ever-decreasing size must be accommodated on the same surface of the semiconductor crystal. This trend towards miniaturization embraces not only the integrated circuit but also its … Show more
“…Carbenes are important intermediates in a variety of chemical reactions and have therefore been extensively studied both experimentally and theoretically . Carbenes have low-lying singlet and triplet states and, because their reactivity is state-specific, the magnitude of the singlet−triplet (S−T) splitting is of great importance and has received particular attention. , Carbonyl carbenes (YC−CO−X) are widely used in synthesis and in industry as photoresists . A key reaction that singlet carbonyl carbenes can undergo is the Wolff rearrangement, leading to the production of a ketene: …”
High-level ab initio calculations at the G3(MP2)//B3-LYP level have been used to study carbomethoxychlorocarbene and related halogenocarbenes and carbonyl carbenes. Initial calculations at the more accurate W1' level on the subset CH(2), HCCl, HCF, CCl(2), and CF(2) provide support for the reliability of G3(MP2)//B3-LYP for this type of problem. The W1' calculations also suggest that the experimental S-T splitting is slightly underestimated for HCCl and CF(2) and substantially underestimated for CCl(2), in keeping with other recent high-level studies. Whereas the parent carbonyl carbenes, namely formylcarbene, carbohydroxycarbene, and carbomethoxycarbene, are all predicted to have triplet ground states, their chloro and fluoro derivatives are predicted to have singlet ground states. In particular, carbomethoxychlorocarbene is predicted to have a singlet ground state, with the singlet-triplet splitting estimated as -16.0 kJ mol(-)(1). The barriers to Wolff rearrangement of the singlet carbonyl carbenes generally (but not always) correlate with the exothermicity accompanying the production of ketenes. In the case of the parent carbonyl carbenes, for which the rearrangement reaction is most exothermic, the barriers lie between about 10 and 30 kJ mol(-)(1), whereas for the less exothermic rearrangements of the chloro- and fluoro-substituted carbonyl carbenes, the Wolff rearrangement barriers increase significantly to between 58 and 75 kJ mol(-)(1). The calculated barrier for carbomethoxychlorocarbene is 58.2 kJ mol(-)(1).
“…Carbenes are important intermediates in a variety of chemical reactions and have therefore been extensively studied both experimentally and theoretically . Carbenes have low-lying singlet and triplet states and, because their reactivity is state-specific, the magnitude of the singlet−triplet (S−T) splitting is of great importance and has received particular attention. , Carbonyl carbenes (YC−CO−X) are widely used in synthesis and in industry as photoresists . A key reaction that singlet carbonyl carbenes can undergo is the Wolff rearrangement, leading to the production of a ketene: …”
High-level ab initio calculations at the G3(MP2)//B3-LYP level have been used to study carbomethoxychlorocarbene and related halogenocarbenes and carbonyl carbenes. Initial calculations at the more accurate W1' level on the subset CH(2), HCCl, HCF, CCl(2), and CF(2) provide support for the reliability of G3(MP2)//B3-LYP for this type of problem. The W1' calculations also suggest that the experimental S-T splitting is slightly underestimated for HCCl and CF(2) and substantially underestimated for CCl(2), in keeping with other recent high-level studies. Whereas the parent carbonyl carbenes, namely formylcarbene, carbohydroxycarbene, and carbomethoxycarbene, are all predicted to have triplet ground states, their chloro and fluoro derivatives are predicted to have singlet ground states. In particular, carbomethoxychlorocarbene is predicted to have a singlet ground state, with the singlet-triplet splitting estimated as -16.0 kJ mol(-)(1). The barriers to Wolff rearrangement of the singlet carbonyl carbenes generally (but not always) correlate with the exothermicity accompanying the production of ketenes. In the case of the parent carbonyl carbenes, for which the rearrangement reaction is most exothermic, the barriers lie between about 10 and 30 kJ mol(-)(1), whereas for the less exothermic rearrangements of the chloro- and fluoro-substituted carbonyl carbenes, the Wolff rearrangement barriers increase significantly to between 58 and 75 kJ mol(-)(1). The calculated barrier for carbomethoxychlorocarbene is 58.2 kJ mol(-)(1).
“…Thermal and photochemical rearrangements of α-diazocarbonyl compounds to ketenes (Wolff rearrangement) have received considerable attention because of their relevance to both fundamental science − and applied technology. − In synthetic organic chemistry, the Wolff rearrangement represents the key step in the Arndt−Eistert sequence for the one-carbon homologation of carboxylic acids. − The rearrangement also serves as an excellent method for effecting ring contraction and is notable for its success in forming strained rings. − , Recent applications of the Wolff rearrangement involve the use of α-diazo ketones as photochemically triggered DNA-cleaving reagents. , The most important application of the Wolff rearrangement derives from the use of α-diazocarbonyl compounds in computer circuit microfabrication. − …”
Photolysis of methyl α-diazo-(2-naphthyl)acetate at 450 nm yields primarily the triplet ground state
of 2-naphthyl(carbomethoxy)carbene (3NCC), which was characterized by its UV/visible, IR, and ESR spectra
as well as by trapping with O2 and CO. Bleaching of the weak visible bands of 3NCC (λ > 515 nm) leads to
the disappearance of the triplet ESR spectrum and to a new optical spectrum with broad bands in the near-UV
region. The spectra of 3NCC can be almost fully recovered in the dark at 12 K. The same process also occurs
upon irradiation at 450 nm, with the exception that the recovery of 3NCC is accompanied by the formation of
small amounts of 2-naphthyl(methoxy)ketene and 2-(2-naphthyl)propiolactone. The observed optical and IR
spectra of the intermediate that is formed reversibly from 3NCC are in full accord with quantum chemical
model calculations for the singlet state of the same carbene 1NCC, but not with the tricyclic cyclopropene
derivative observed previously for the parent 2-naphthylcarbene or the 1-(2-naphthyl)-2-methoxyoxirene.
Exploration of the potential energy surfaces for singlet and triplet NCC show that a barrier between the two
states is created by a pronounced change in conformation of the carbomethoxy group, which may furthermore
be hindered in a solid matrix environment.
“…[25][26][27][28] The same polymers as above with only the azide groups have been utilized as photoresists in high resolution lithography. 29,30 In this contribution the chemistry of azide-functionalized copolymers 30 has been adapted to synthesize random copolymers for thin dielectrics for organic FETs which do not show the above addressed problems and are easy to process. Synthesis and characterization of two benzyl azide-containing random copolymers, named PAZ 12 and PAZ 14, and their applicability as thin gate insulator in OFETs are presented.…”
A large number of cross-linkable dielectrics with good dielectric properties have been reported; however, all of them suffer from disadvantages like uncontrolled pre-crosslinking, necessity of high process temperatures and the need for an additional cross-linking compound. In this contribution, two new poly(methyl methacrylate) polymers are introduced which can be cross-linked due to the attached benzyl azide (N3) monomer units making the addition of hardeners or initiators obsolete. The synthesis of the copolymers as well as their successful characterization and usage as gate dielectrics for organic field-effect transistors is demonstrated. The investigated polymers have been labeled PAZ 12 and PAZ 14 according to their azide content in mol%. The additional building blocks of the polymers are methyl methacrylate for PAZ 12 and methyl methacrylate and styrene monomer units in about an equal ratio for PAZ 14. Spin-coated thin films were cross-linked by a thermal treatment at 110 °C followed by an UV exposure at a wavelength of 254 nm yielding insoluble, smooth and electrically dense polymeric networks. Optimal cross-linking parameters were obtained using infrared spectroscopy to follow the N3 vibrational mode. Its disappearance confirms a complete cross-linking reaction, and thus fully reacted azide groups facilitate the analytics. The dielectric properties of the cross-linked thin films have been studied by impedance spectroscopy. The application of double layer dielectrics results in lower dielectric losses and lower leakage currents in the subsequently produced pentacene-based field-effect transistors. These devices operate at voltages below −6 V and show hysteresis-free current–voltage characteristics with hole mobilities up to 0.16 cm2 V−1 s−1. PAZ 12 appears to be superior to PAZ 14 due to a lower total layer thickness of down to 92 nm still providing good insulation in the transistor presumably related to a lower free volume that arises in the cross-linked network of the two-component containing copolymer PAZ 12
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