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Spectroscopic, electrochemical, and structural properties of 2,6-dialkoxy-9,10-anthraquinones (Anth-OCn, n = 4, 6, 8, 10, and 12) of increasing alkoxy substituents length were investigated. UV-vis spectroscopy showed a substitution-induced bathochromic shift of the least energetic band from 325 nm in the case of unsubstituted anthraquinone to ca. 350 nm for the studied derivatives. Similarly as unsubstituted anthraquinone, the studied compound showed two reversible one electron reductions to a radical anion and spinless anions, respectively. The first reduction was affected by electron-donating properties of the substituents, its potential being shifted to ca. -1.5 V (vs Fc/Fc+), i.e., by 80 to 95 mV as compared to the case of unsubstituted anthraquinone. This corresponded to a decrease of |EA| from 3.27 to 3.19-3.17 eV. The experimental spectroscopic and electrochemical data were in full agreement with the DFT calculations. The introduction of the alkoxy substituent improved solution processibility of the studied compounds and facilitated the formation of their ordered supramolecular 2D aggregation on HOPG as well as single crystal growth from solutions. Comparative structural investigations carried out on single crystals and monolayers deposited on HOPG revealed two, mutually related, effects of the substituent length on the resulting supramolecular organization. The first one concerns both the 2D organization in the monolayers and 3D molecular arrangement in crystals: increasing substituent length evolution of the structure occurs from herringbone-type to lamellar. The second effect, observed in monolayers of the derivatives with longer substituents, concerns gradual evolution of their lamellar structures with increasing substituent length. This evolution is induced by the structure of the graphite substrate and involves increasing correlation of the molecules orientation (anthraquinone cores as well as alkoxy substituents) with the symmetry of the graphite substrate. As a result, their 2D and 3D structures become dissimilar.

Three new donor-acceptor (D-A) compounds, positional isomers of phenoxazine-substituted acridone, namely 1-phenoxazine-N-hexylacridone (o-A), 2-phenoxazine-N-hexylacridone (m-A) and 3-phenoxazine-N-hexylacridone (p-A), were synthesized. The synthesized compounds showed interesting, isomerism-dependent electrochemistry. Their oxidation was reversible and their potential (given vs. Fc/Fc+) changed from 0.21 V for o-A to 0.36 V for p-A. In contrast, their reduction was irreversible, isomerism-independent and occurred at rather low potentials (ca. -2.25 to -2.28 V). The electrochemical results led to the following values of the ionization potentials (IPs) and electron affinities (EAs): 5.03 eV and -2.14 eV, 5.15 eV and -2.20 eV, and 5.20 eV and -2.28 eV for o-A, m-A and p-A, respectively. The experimentally obtained values were in very good agreement with those predicted by DFT calculations. All three isomers readily formed single crystals suitable for their structure determination. o-A and p-A crystallized in P1[combining macron] and P21/n space groups, respectively, with one molecule per asymmetric unit, while m-A crystallized in the P21/c space group with two molecules in the asymmetric unit accompanied by disordered solvent molecules. The UV-vis spectra of the studied compounds were isomerism and solvent independent, yielding absorption maxima in the vicinity of 400 nm. Their photoluminescence spectra, in turn, strongly depended on isomerism and the used solvent showing smaller Stokes shifts for the emission bands registered in toluene as compared to the corresponding bands measured in dichloromethane. The photoluminescence quantum yields (φ) were systematically higher for toluene solutions reaching the highest value of 20% for p-A. For all three isomers studied, stationary and time-resolved spectroscopic investigations carried out in toluene at different temperatures revealed spectral features indicating a contribution of thermally activated delayed fluorescence (TADF) to the observed spectroscopic behaviour. The measured photoluminescence quantum yields (φ) were higher for solid state films of pure compounds and for their dispersions in solid matrices (zeonex) than those recorded for toluene and dichloromethane solutions of the studied phenoxazine-N-hexylacridone isomers. The obtained experimental spectroscopic and structural data were confronted with theoretical predictions based on DFT calculations.

Two new electropolymerizable monomers were synthesized, namely dithieno[3,2-b:2′,3′-d]pyrrole N-functionalized with 4-(2-heptylthiazol-4-yl)phenyl (DTP1) and 4-(5-octylthiophen-2-yl)phenyl (DTP2) groups. Both monomers readily electropolymerize to yield the corresponding polyDTP1 and polyDTP2. Electrochemically determined ionization potential (IP) of both polymers (about 4.75 eV) are higher than IPs of poly(dithieno[3,2-b:2′,3′-d]pyrrole) N-substituted with alkyl or alkylphenyl groups. This finding, corroborated by DFT calculations, suggests that electron accepting nature of (thiazol-4-yl)phenyl and (thiophen-2-yl)phenyl substituents lowers the π-electron density in the dithienopyrrole moiety making the polymers oxidation more difficult. Optical band gaps of polyDTP1 (Eg opt = 1.76 eV) and polyDTP2 (Eg opt = 1.78 eV) are lower than the gaps of poly(dithieno[3,2-b:2′,3′-d]pyrrole) N-substituted with alkyl or alkylphenyl groups. This combined with higher IP value yield higher electron affinity (ǀEAǀ) value. Thus, the obtained new polymers are more difficult to oxidize but easier to reduce as compared to poly(dithieno[3,2-b:2′,3′-d]pyrrole)s studied to date. Again, these findings are in a very good agreement with DFT calculations. As evidenced by UV–vis–NIR spectroelectrochemistry, both polymers undergo classical (for conjugated polymers) oxidation, involving the formation of polarons in the first step and bipolarons in the second one. An interesting feature of the oxidation of polyDTP2 is the highly delocalized nature of bipolarons, indicative of the metallic state (featureless absorption tails extending towards NIR part of the spectrum). In order to elucidate the exact nature of the electrochemical oxidation process detailed Raman spectroelectrochemical investigations of polyDTP2 were carried out supported by the vibrational model calculations using two methods: DFT and General Valence Force Field (GVFF). This combined experimental and theoretical study leads to a conclusion that radical cations (polarons) formed at the first stage of oxidation are formed in the pyrrole ring whereas dications formed in the second stage show classical bipolaron configuration with positive charges located on the thiophene rings.

Self-organization in mono- and bilayers on HOPG of two groups of benz[5,6]acridino[2,1,9,8-klmna]acridine derivatives, namely, 8,16-dialkoxybenzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridines with an increasing alkoxy substituent length and 8,16-bis(3- or 4- or 5-octylthiophen-2-yl)benzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridines, i.e., three positional isomers of the same benzoacridine, is investigated by scanning tunneling microscopy. The layers were deposited from a solution of the adsorbate (in hexane or dichloromethane) and imaged ex situ at molecular resolution. In all cases, the resulting two-dimensional (2D) supramolecular organization is governed by the interactions between large, fused heteroaromatic cores that form densely packed rows separated by areas covered by substituents. In 8,16-dialkoxybenzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridines, the alkoxy substituents, separating the rows of densely packed cores, are interdigitated. An increasing substituent length leads to an intuitively expected increase in this 2D unit cell parameter that corresponds to the orientation of the substituent in the monolayer. In the case of 8,16-bis(3- or 4- or 5-octylthiophen-2-yl)benzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridine positional isomers, the self-assembly processes are more complex. Although the determined 2D unit cell is in all cases essentially the same, the role of alkylthienylene substituents in layer formation is distinctly different. Thus, the formation of monolayers and bilayers is very sensitive to isomerism. 8,16-Bis(5-octylthiophen-2-yl)benzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridine is capable of forming the most stable monolayer and the most labile bilayer. In the case of 8,16-bis(3-octylthiophen-2-yl)benzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridine, an inverse phenomenon is observed leading to the most labile monolayer and the most stable bilayer. These differences are rationalized in terms of dissimilar molecular geometries of the studied isomers and different interdigitation patterns in their 2D supramolecular structures.

A new DπAπD compound consisting of naphthalene diimide core-functionalized with 1,4-phenylene-functionalized carbazole, namely 2,6-bis[4-(9H-carbazol-9-yl)phenyl]-N,N’-bis(2-ethylhexyl)-1,4,5,8-naphthalenetetracarboxylic acid diimide (CNDI) was synthesized. Its redox properties (reduction and oxidation potentials, electron affinities (EA) and ionization potentials (IP)) were compared with those of 4,7-bis(4-(9H-carbazol-9-yl)phenyl)benzo[c][1,2,5]thiadiazole (CBTD) – a specially synthesized reference compound containing identical Dπ- units and significantly weaker acceptor (benzothiadiazole). It was demonstrated that the acceptor strength, determined as the index of the spatial extent of the charge transfer, D C T P , only weakly influenced the molecule oxidation potential and by consequence its ionization potential. To the contrary, strong effect of charge transfer, expressed by D C T P , was found for the reduction potential of CNDI and CBTD, showing significantly higher reduction potential of the former leading to much higher |EA|. CNDI could be electrochemically polymerized yielding a low band gap polymer (Eg = 1.63 eV) of ambipolar character, exhibiting low ionization potential (IP = 5.48 eV) and high electron affinity (|EA| = 3.85 eV). In its cyclic voltammograms polyCNDI shows five redox states, namely neutral, first and second reduction and first and second oxidation ones. As revealed by detailed studies of electrochromic parameters only three redox states (neutral, first reduction and first oxidation) demonstrate good electrochromic performance.

A novel synthetic strategy for the preparation of quinacridone derivatives with extended conjugation in central aromatic core is proposed allowing for fine tuning of their electronic properties. Two new quinacridone derivatives with carbazole (1) and naphthalene (2) core are described, which are excellent candidates for optoelectronic applications as evidenced by their electrochemically determined redox properties combined with strong photoluminescence (the fluorescence quantum yield of 0.83 and the radiative rate constant of 90.2 × 107 s−1 in the case of 2).

This review is devoted to low and high molecular mass electroactive materials containing triphenylamine (TPA) structural units. It is shown that by appropriate selection of C–C coupling methods, it is possible to obtain solution-processable, electroactive materials of tunable donor–acceptor properties, suitable for the use as active layers in p-channel or ambipolar field effect transistors, as hole-transporting layers and as electroluminophores in organic light-emitting diodes. Other applications involve their use as components of bulk heterojunctions in organic solar cells and dye-sensitized solar cells. Since TPA-based materials exhibit high electrochemical reversibility, they can also be technologically exploited as solution-processable electrochromic materials.

One of the most challenging problems limiting the development of the technology of organic electronics is a lack of simple, solution based, techniques for producing organic thin film transistors (OTFTs) with ambipolar characteristics. In this work, a simple method of manufacturing ambipolar OTFTs, based on a zone-casting technique, is presented. This technique was used to prepare thin and highly oriented films from a combination of the p-type organic semiconductor, TIPS-Pentacene, with one of the two naphthalene bisimide derivatives, both exhibiting electron conductivity. The OTFTs produced with such active layers display ambipolar properties with symmetric characteristics and electron and hole mobility in the best case amounting to: μe = 1.5 × 10−2 and μh = 1.1 × 10−2 cm2 V−1 s−1, respectively.

EPR and UV–vis spectroelectrochemical behavior of a series of ambipolar donor–acceptor–donor (DAD) compounds, consisting of a diketopyrrolopyrrole (DPP) central unit symmetrically disubstituted with mono-, bi- and terthiophene, is reported. All derivatives studied undergo a reversible reduction to radical anions at E ca. −1.55 V to ca. −1.65 V vs Fc/Fc+. Electrochemically generated radical anions are sufficiently stable to be detected at RT. Two-step oxidation of these compounds involves the formation of radical cations in the first step followed by their transformation into spinless dications in the second one. The formed radical cations are detectable at RT, however, contrary to the case of radical anions they yield unresolved EPR spectra. The potential of their formation depends on the length of D segment decreasing from ca. 0.50 V vs Fc/Fc+ for monothiophene disubstituted DPP to ca. 0.25 V in the case of the terthiophene derivative. Combining differential pulse voltammetry with EPR and UV–vis spectroelectrochemistry allows for unequivocal identification of all new, electrochemically induced UV–vis bands to particular forms of the studied molecules (radical anions, radical cations or dications). Both electrochemical reduction and electrochemical oxidation processes involve profound and distinctly different spectral changes in the visible range of the spectrum. Since they are reversible, the studied compounds can be considered as promising multicolor electrochromophores.

Three D-π-Α-π-D organic luminophores of tunable donor-acceptor interactions were synthesized by combining carbazole D-units with two different A units, namely 2,5-dithiophen-2-yl-[1,3,4]-thiadiazole and benzo[c][1,2,5]thiadiazole. In the third compound tert-butyl groups were introduced to the carbazole ring to increase its electron-donating properties. This compound, namely 4,7-bis(4-(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)benzo[c][1,2,5]thiadiazole (CBTD2) turned out to be a very good photoluminophore showing the photoluminescence quantum yield (φ) of 62% in toluene solution and 45% when dispersed in a solid blend consisting of poly(vinylcarbazole) (PVK) and 2-([1,1′-biphenyl]-4-yl)-5-(4'-(tert-butyl)-[1,1′-phenyl]-4-yl)-1,3,4-oxadiazole (PBD). Moreover, its electrochemically determined ionization potential (IP = 5.55 eV) and electron affinity (EA = −2.73 eV) made it a very promising candidate for application as an active component in light emitting diodes of guest/host configuration with PVK-PBD matrix. The fabricated diodes of the following structure ITO/PEDOT:PSS/PVK-PBD + CBTD2/Ca/Ag showed the luminance reaching 6000 cd/m2 with luminous efficiency of 1 cd/A.

It is demonstrated that a naphthalene diimide core disubstituted with triphenylamine can be used as a thermally activated delayed fluorescence emitter in organic light emitting diodes. Detailed spectroscopic studies demonstrated unusual host effects on the photophysical properties of this material. In particular, we were able to deduce recombination pathways and the role of the host and temperature in increasing/decreasing the TADF contribution in overall emission. Furthermore, stemming from these host effects on the geometry of the emitter we discover different local triplet states involved in the TADF mechanism. We elucidate this confusing situation to show that simply measuring low-temperature phosphorescence does not always give the energy of the local triplet involved in TADF. The studies carried out in a non-polar polymer and the OLED host were completed by NIR OLED fabrication showing promising characteristics.

Five and six heterocycle ring assemblies, comprising triazole or oxadiazole acceptor (A) units and thiophene or alkylthiophene donor (D) units in a DDADD and DDAADD arrangement, have been synthesised and characterised by spectroscopic and electrochemical means. It is demonstrated that the replacement of a weaker acceptor (triazole) by a stronger one (oxadiazole) in DDADD compounds results in lowering of the frontier molecular energy gap by 70 meV from 2.94 to 2.87 eV. For oxadiazole-centred compounds these gaps can be further lowered by increasing the number of A units and alkyl solubilising substituents, down to 2.76 eV for the DDAADD compound containing four alkyl pendants. The photoluminescence quantum yield exceeds 50 % for DDADD compounds and reaches 78 % for DDAADD ones. All compounds, when dispersed in a blend consisting of 70 % poly(vinylcarbazole) (PVK) and 30 % of 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD) (host–guest configuration), demonstrate light-emitting diode behaviour, affording blue, tuneable emission with luminances reaching 120 cd m−2 and luminous efficiencies of 0.12 cd A−1 for non-optimised devices.

Diketopyrrolopyrroles symmetrically disubstituted with bi- or terthiophenes, abbreviated as DPPnT, are interesting semiconductors exhibiting small optical band gap, tunable photoluminescence of high quantum yield and high charge carrier mobilities for both electrons and holes. Scanning tunneling microscopy (STM) has been used to study the 2D supramolecular organization in monomolecular layers on HOPG of six DPPnT derivatives with different lengths and positions of alkyl substituents and different sizes of thiophene segments. All compounds show a strong tendency to form ordered monolayers of regular lattice-like structure, however, specific characteristics of their organization depend on their molecular topology. The observed differences in the supramolecular organization revealed two specific features of crucial importance: (i) clear effect of the alkyl substituent position (central core vs terminal thiophene ring) on the alkyl group interdigitation pattern and (ii) influence of the position of the alkyl substituents in the terminal thiophene ring on the molecule conformation and the resulting 2D supramolecular organization. Moreover, self-assembly in the monolayers was compared with the 3D organization deduced from the powder X-ray diffraction, indicating close similarity for the majority of compounds.

A series of solution-processable tetraalkoxy-substituted dinaphtho[2,3-a:2′,3′-h]phenazines were synthesized by reductive functionalization of indanthrone (6,15-dihydrodinaphtho[2,3-a:2′,3′-h]phenazine-5,9,14,18-tetraone), an old intractable dye. The melting point of these new compounds was found to decrease from 204 °C to 98 °C upon extension of the number of carbons from 4 to 12 in the alkoxy substituent. All derivatives show a strong tendency to self-organize in 2D as evidenced by STM investigations of monolayers deposited on HOPG. The 2D structure is less dense and shows different alkoxy group interdigitation pattern as compared to the 3D structure determined from the X-ray diffraction data obtained for the corresponding single crystals. Electrochemical, absorption, and emission properties of tetraalkoxy-substituted dinaphtho[2,3-a:2′,3′-h]phenazines, studied in solution, are essentially independent of the length of the alkoxy substituents. All derivatives exhibit high photoluminescence quantum yield,...

Four arylene bisimides N-substituted with triarylamine and three bisimides core-functionalized with the same substituent were studied by cyclic voltammetry, UV-vis and EPR spectroelectrochemistry. All the investigated compounds showed ambipolar behaviour manifested by their quasi-reversible reduction to radical anions and quasi-reversible oxidation to radical cations. The presence of stable radical anions and radical cations was confirmed by EPR spectroelectrochemical experiments. Formation of the radical anions resulted in bleaching of the bisimide UV-vis bands with simultaneous hypsochromic shift of the charge transfer (CT) band and appearance of the radical anion peaks, the bands originating from the triarylamine remaining essentially unchanged. Electrochemical generation of radical cations resulted in turn in bleaching of the triarylamine band accompanied by a hypsochromic shift of the CT band and with the appearance of the radical cation bands at higher wavelengths, the bisimide bands remained essentially intact.

Photo- and electroluminescence of five bithiophene disubstituted 1,3,4-thiadiazoles, constituting a new class of solution processable materials for organic opto-electronics, were studied. It was found that the introduction of alkyl solubilizing substituents bathochromically shifted the photo- and electroluminescence bands. The most pronounced effect was observed for the substitution at the Cα position which changed the emitting light color from bluish to green. All five derivatives were tested in host/guest type organic light emitting diodes (OLEDs) with either poly(N-vinylcarbazole) (PVK) or poly(N-vinylcarbazole) + 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PVK + PBD) matrices. The latter matrix turned out especially well suited for these guest molecules yielding devices of varying color coordinates. The best luminance (750 cd/m2) was measured for 2,5-bis(5'-octyl-2,2'-bithiophene-5-yl)-1,3,4-thiadiazole with the luminous efficiency exceeding 0.4 cd/A. © 2014 Elsevier B.V. All rights reserved.

A series of solution processable semiconducting donor-acceptor (DA) copolymers consisting of either diketopyrrolopyrrole or benzothiadiazole A units and alkoxy- or alkyl-substituted oligothiophene D units were synthesized. For all prepared copolymers the measured XPS spectra (C1s, S2p, N1s and O1s) were in a very good agreement with the expected chemical constitution. Spectroscopic studies of the synthesized copolymers showed that their optical band gaps were governed by the presence of the alkoxy substituents whose electron donating properties led to additional gap narrowing yielding semiconductors with band gaps of below 1.3 eV in the case of the polymers with the diketopyrrolopyrrole A unit. The same trend was observed with the electrochemical band gaps, whose values were however found to be ca. 0.4 eV superior to the corresponding optical band gaps values. Vibrational model was calculated for two of the synthesized copolymers with the goal to unequivocally attribute the observed Raman modes and to support the interpretation of the spectral changes induced by the electrochemical oxidation. It was established that the electrochemical oxidative doping of the copolymer with the benzothiadiazole A unit is limited to the oligothiophene segment in which the charge of the formed polycation is localized. To the contrary, in the case of the polymer with the diketopyrrolopyrrole A segment the charge imposed on the oligothiophene segment delocalizes towards the diketopyrrolopyrrole unit. These findings are in perfect agreement with the UV-vis-NIR spectroelectrochemistry data which show strong localization of electrochemically created charge carriers in the benzothiadiazole - oligothiophene copolymer and their metallic-like delocalization in the diketopyrrolopyrrole one. The latter seems to be very interesting not only as a potential low band gap component of organic photovoltaic cells but also, in the doped state, as electronic conductor of metallic character.

In this work technological properties of ceramic slurries based on silicon carbide were characterized. Silicon carbide and poly(vinyl alcohol) in an amount 6%, 10% and 15 wt. % as a solution were added to prepare the ceramic slurries. Solid phase content in ceramic slurries was 62, 5 wt.%. Plate weight test, pH, density, viscosity (measured by the Zhan 4# cup) and dynamic viscosity were investigated. Dipping test on wax model was done to measure adhesive properties. Characterization of SiC fillers powder was made by determination of grain size, density, chemical composition, Zeta potential and by use of scanning electron microscopy. Obtained results of ceramic slurries based on SiC meet standard specification in industrial investment casting and its properties are very promising for future application in investment casting of superalloys.

Indanthrone, an old, insoluble dye can be converted into a solution processable, self-assembling and electroluminescent organic semiconductor, namely tetraoctyloxydinaptho[2,3-a:2',3'-h]phenazine (P-C8), in a simple one-pot process consisting of the reduction of the carbonyl group by sodium dithionite followed by the substitution with solubility inducing groups under phase transfer catalysis conditions.

XPS/UPS was used to examine interface energetics of PBI-4-t-BuPh/metal interfaces.No reaction between the substrates and the organic semiconductor was observed.An interfacial dipole of 0.5eV was found at the PBI-4-t-BuPh/Au interface.Vacuum level alignment is observed at the interface with Al.Al is a more suitable substrate for OFET applications using PBI-4-t-BuPh. The interfaces between perylene bisimide with 4-t-butylphenyl N-substituents (an organic semiconductor) and gold or aluminum were studied by Ultraviolet and X-ray photoelectron spectroscopies (UPS and XPS). Neither of the substrates reacts with the organic semiconductor. An interfacial dipole of 0.5eV is found at the interface with gold, whereas with aluminum a vacuum level alignment is observed. The onset of the highest occupied molecular orbital (HOMO) was determined at 2.3eV below the Fermi level. An electron injection barrier of 0.6eV was found for aluminum and 0.9eV for gold, which indicates that the interface with aluminum seems more promising for organic field effect applications.

The type of N-substituents affects the energetics at the interface with Au.The organic semiconductors seem to form uniform films on the substrate.Alkylthienyl N-substituted naphthalene bisimides show smaller injection barriers. Semiconducting naphthalene bisimide derivatives belong to the most popular organic materials presently used as active layers in n-channel or ambipolar organic field effect transistors. Substituents at imide nitrogen atoms in these compounds can modify not only their physical properties such as the ionization potential and the electron affinity, but also their solution processability and supramolecular organization. Moreover, on view of possible applications of these semiconductors in organic electronics, specific phenomena occurring at the semiconductor/ electrode interface must be elucidated. In this work we have studied by Photoelectron Spectroscopies the effect of the type of N-substituents in naphthalene bisimides on the energy diagram of the organic semiconductor/Au interface. Two differently N-substituted organic semiconductors have been tested and compared: the first containing alkylthienylphenylene N-substituents whereas the second - alkylphenyl ones. For both compounds the work function, the highest occupied molecular orbital position (HOMO) and the ionization potential were determined, as well as the interface dipole and the injection barriers at the interface with Au. The experimental results clearly show that alkylthienylphenylene N-substituted naphthalene bisimides exhibits smaller injection barriers at the interface with gold compared to the alkylphenylene substituted one.

The aim of this work was to characterize the microstructure of the as-cast Haynes® 282® alloy. Observations and analyses were carried out using techniques such as X-ray diffraction (XRD), light microscopy (LM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray spectroscopy (EDS), wave length dispersive X-ray spectroscopy (WDS), auger electron spectroscopy (AES) and electron energy-loss spectrometry (EELS). The phases identified in the as-cast alloy include: γ (gamma matrix), γʹ (matrix strengthening phase), (TiMoCr)C (primary carbide), TiN (primary nitride), σ (sigma-TCP phase), (TiMo)2SC (carbosulphide) and a lamellar constituent consisting of molybdenum and chromium rich secondary carbide phase together with γ phase. Within the dendrites the γʹ appears mostly in the form of spherical, nanometric precipitates (74 nm), while coarser (113 nm) cubic γʹ precipitates are present in the interdendritic areas. Volume fraction content of the γʹ precipitates in the dendrites and interdendritic areas are 9.6% and 8.5%, respectively. Primary nitrides metallic nitrides (MN), are homogeneously dispersed in the as-cast microstructure, while primary carbides metallic carbides (MC), preferentially precipitate in interdendritic areas. Such preference is also observed in the case of globular σ phase. Lamellar constituents characterized as secondary carbides/γ phases were together with (TiMo)2SC phase always observed adjacent to σ phase precipitates. Crystallographic relations were established in-between the MC, σ, secondary carbides and γ/γʹ matrix.

A series of copolymers consisting of alternating thiadiazole and unsubstituted or alkyl disubstituted quaterthiophene units, were synthesized by electropolymerization of 2,5-bis(2,2′-bithiophene-5-yl)-1,3,4-thiadiazole (polymer P1 ), 2,5-bis(4′-octyl-2,2′-bithiophene-5-yl)-1,3,4-thiadiazole (polymer P2 ), 2,5-bis(3′-octyl-2,2′-bithiophene-5-yl)-1,3,4-thiadiazole (polymer P3 ), 2,5-bis(3-decyl-2,2′-bithiophene-5-yl)-1,3,4-thiadiazole (polymer P4 ). For comparative reasons P3 was also obtained via Suzuki coupling of 2,5-bis(5-bromo-2-thienyl)-1,3,4-thiadiazole and neopentyl ester of 4,4′-dioctyl-2,2′-dithienyl-5,5′-diboronic acid. As evidenced by cyclic voltammetry studies the presence of electron accepting thiadiazole unit in the main polymer chain results in an increase of the reductive doping potential of the studied compounds as compared to polythiophene or poly(alkylthiophene). Electrochemically determined electron affinities values were found in the range from −3.10 eV to −3.14 eV, showing a negligible effect of the alkyl substituent on this parameter. To the contrary, the oxidation potential of the studied copolymers strongly depended on the presence and the position of the alkyl group. For P3 the electron donating properties of the substituents were particularly pronounced leading to a decrease of its oxidative doping potential by 210 mV, as compared to the case of the unsubstituted polymer ( P1 ), and the corresponding drop of the ionization potentials from +5.75 eV to +5.54 eV. The presence of a characteristic capacitive plateau's following the reductive and oxidative dopings suggests that both redox reactions are true doping reactions and the synthesized polymers can be transformed either in n-type or p-type conductors. For P3 and P4 these findings are additionally corroborated by UV–vis-NIR spectroelectrochemical data which unequivocally show the formation of polaronic/bipolaronic bands upon reductive and oxidative dopings. The analysis of the Raman spectroelectrochemical data obtained for P3 , supported by theoretical calculations of the vibrational model, leads to the conclusion that the mechanism of the electrochemical doping in this polymers is the same as in poly(alkylthiophene) homopolymers and involves the transformation of the benzoid-like structure into quinoid one. As judged from the redox properties of the synthesized copolymers, P3 seems to be the most promising candidate for application in such organic electronic devices such as p-channel field effect transistors (FETs), photodiodes (PD) or photovoltaic cells (PC), however its use in air operating n-channel and ambipolar FETs seems to be excluded due to relatively high absolute value of electron affinity.

Unsubstituted 2,5-bis(2,2′-bithiophene-5-yl)-1,3,4-thiadiazole and four of its derivatives containing solubilizing octyl groups in different positions of the terminal thiophene ring were synthesized (3 new compounds and 2 already reported). Their UV–vis absorption and emission spectra turned out to be strongly dependent on the position of the substituent and showed significant bathochromic shifts of the dominant transition for compounds with the substituents attached to Cα of the terminal ring (λmax > 425 nm). A good correlation was found for the experimentally determined and theoretically calculated excitation energies employing the time-dependent Coulomb-attenuated hybrid exchange-correlation functional using the 6-31G* basis set (TD CAM-B3LYP/6-31G*). The calculations showed, in addition, that the alkyl substituents improved the planarity of the molecule and its aromaticity, and that they raised the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels (the lat...

Key parameters for organic semiconductors used as active layers in organic electronic devices are: solution processability, charge carriers mobility as well as the electron affinity (EA) and the ionization potential (IP) which determine their redox properties and by consequence their air stability. The purpose of the present work was to investigate the influence of different substituents at imide nitrogen atom (alkylaryl, thienylene and triarylamine) and at naphthalene core (triarylamine) on the IP and EA values in recently synthesized naphthalene bisimide derivatives, tested as promising semiconductors for flexible n-channel or ambipolar organic field effect transistors (OFETs). The ionization potentials were determined by Ultra-violet Photoelectron Spectroscopy (UPS) for thin semiconductor films evaporated in ultra-high vacuum. The values obtained by photoelectron spectroscopy were compared with the ones determined from electrochemical investigations of the semiconductors dissolved in an electrolyte solution. Using cyclic voltammetry the IPs was estimated from the onset of the first oxidation peak whereas EAs from the onset of the first reduction peak. In cases where it was not possible to record the oxidation wave in the electrolyte electrochemical window, the IPs values were calculated by subtracting the energy of the spectroscopically (UV–vis–NIR) determined band gap from the EA values and changing the sign. A good correlation between the spectroscopic (UPS) and electrochemical data was found.

Scanning tunneling microscopy was used to investigate self-organization in mono- or multilayers of an organic semiconductor used for the fabrication of n-channel field effect transistors, namely N,N′-bis(4-n-butylphenyl)-perylene-3,4:9,10-tetracarboxylic-diimide (4-n-BuPh-PTCDI). Two types of substrates were used: HOPG and reconstructed Au(111). All investigations were performed at liquid–solid interface in a trichlorobenzene solution. Monolayers deposited directly on the HOPG show a brick-wall organization with individual molecules lying flat on the substrate surface (the planes of aromatic cores being parallel to this surface). Monolayers obtained by controlled dissolution of a previously deposited multilayer show a different 2D organization in which individual molecules are in the edge-on position i.e. stand perpendicular to the substrate surface with their long axis parallel to it. This finding clearly demonstrates the effect of the upper-lying layers on the first monolayer which changes the balance in the molecule–substrate and molecule–molecule interactions, leading to a rotation of the molecules in the first layer. A very similar structure of densely packed molecules, oriented perpendicular to the substrate, is also found for the monolayer deposited on the Au(111) surface.

Two low molecular weight electroactive donor-acceptor-donor (DAD)-type molecules are reported, namely naphthalene bisimide (NBI) symmetrically core-functionalized with dithienopyrrole (NBI-(DTP)2 ) and an asymmetric core-functionalized naphthalene bisimide with dithienopyrrole (DTP) substituent on one side and 2-ethylhexylamine on the other side (NBI-DTP-NHEtHex). Both compounds are characterized by low optical bandgaps (1.52 and 1.65 eV, respectively). NBI-(DTP)2 undergoes oxidative electropolymerization giving the electroactive polymer of ambipolar character. Its two-step reversible reduction and oxidation is corroborated by complementary EPR and UV/Vis-NIR spectroelectrochemical investigations. The polymer turned out to be electrochemically active not only in aprotic solvents but also in aqueous electrolytes, showing a distinct photocathodic current attributed to proton reduction. Additionally, poly(NBI-(DTP)2 ) was successfully tested as a photodiode material.

In organic electronics solution-processable n-channel field-effect transistors (FETs) matching the parameters of the best p-channel FETs are needed. Progress toward the fabrication of such devices is strongly impeded by a limited number of suitable organic semiconductors as well as by the lack of processing techniques that enable strict control of the supramolecular organization in the deposited layer. Here, the use of N,N′-bis(4-n-butylphenyl)-1,4,5,8-naphthalenetetracarboxylic-1,4:5,8-bisimide (NBI-4-n-BuPh) for fabrication of n-channel FETs is described. The unidirectionally oriented crystalline layers of NBI-4-n-BuPh are obtained by the zone-casting method under ambient conditions. Due to the bottom-contact, top-gate configuration used, the gate dielectric, Parylene C, also acts as a protective layer. This, together with a sufficiently low LUMO level of NBI-4-n-BuPh allows the fabrication and operation of these novel n-channel transistors under ambient conditions. The high order of the NBI-4-n-BuPh molecules in the zone-cast layer and high purity of the gate dielectric yield good performance of the transistors.

Three novel electroactive copolymers, consisting of alternating naphthalene bisimide and oligoarylene segments have been synthesized and studied by cyclic voltammetry and UV–vis-NIR spectroelectrochemistry. These studies show that the conjugation between both copolymer segments is very weak and the reduction of the bisimide part is essentially uninfluenced by the oligoarylene segment. The oxidation of the oligoarylene segment strongly depends on its length but is not affected by the presence of the bisimide part. The HOMO levels, determined electrochemically are systematically below −5.0 eV with respect to the vacuum level, changing from −5.45 eV for poly[1,4-phenylene-(4,3′(4′),3″-trioctyl-2,2′,5′,2″-terthiophene-5,5″-diyl)-1,4-phenylene-1,4,5,8-naphthalenediimide-N,N′-diyl] ( 6 ) to −5.50 eV in poly[1,4-phenylene-(4,4′-dioctyl-2,2′-bithiophene-5,5′-diyl)-1,4-phenylene-1,4,5,8-naphthalenediimide-N,N′-diyl] ( 5 ) and −5.84 eV for poly[1,4-phenylene-(3,4-dioctylthiophene-2,5-diyl)-1,4-phenylene-1,4,5,8-naphthalenediimide-N,N′-diyl] ( 4 ). The LUMO levels in all three cases are close to −4.0 eV. The obtained results clearly indicate that 5 and 6 are good candidates for the fabrication of ambipolar transistors operating in air whereas 4 can be considered as an active component of n-channels FETs.

New tetraester derivatives of 1,4,5,8-tetraazaanthracene have been prepared and characterized by spectroscopic and electrochemical techniques. The LUMO level of the compounds is close to -4 eV (the so-called air operating stability border in n-channel field effect transistors). Tetraesters were obtained with reasonable yields without the necessity of using high-quality reactants or solvents, resulting in their low cost.

New, solution processable organic semiconductors, namely arylene bisimides core- or N-functionalized with triarylamines have been synthesized in view of their potential application in organic electronics. In N-functionalized compounds the electrochemically determined oxidation potentials are 0.46 and 0.48 V vs Fc/Fc+ for perylene (P1) and naphthalene (N1) bisimides, respectively. For the core functionalized perylene bisimide (P2) this potential is shifted to higher values (0.55 V vs Fc/Fc+). A reversed trend is observed for the first reduction potential since P2 is being reduced at the lowest potential (−1.09 V) whereas N1 and P1 at −1.05 and −1.02 V, respectively. These shifts observed in the case of P2 are induced by donor–acceptor interactions between the substituent and the core. The results of DFT calculations performed for N-substituted bisimides indicate a clear separation in space of the HOMO and LUMO orbitals, the former being located on the triarylamine substituent whereas the latter is on the b...

Two series of new soluble conjugated compounds containing tetrazine central ring have been synthesized. The three-ring compounds have been synthesized by the reaction of aryl cyanide (where aryl = thienyl, alkylthienyl, phenyl or pyridyl) with hydrazine followed by oxidation of the intermediate product with diethyl azodicarboxylate. The five-ring compounds have been prepared using two pathways: (i) reaction of 5-cyano-2,2'-bithiophene (or its alkyl derivative) with hydrazine; (ii) via Suzuki or Stille coupling of 3,6-bis(5-bromo-2-thienyl)-1,2,4,5-tetrazine with a stannyl or boronate derivative of alkylthiophene. UV-vis spectroscopic properties of the synthesized compounds are strongly dependent on the nature of the aryl group, the position of the solubilizing substituent and the length of the molecule, showing the highest bathochromic shift (λ(max)440 nm) for five-ring compounds with alkyl groups attached to C(α) carbon in the terminal thienyl ring. An excellent linear correlation has been found for spectroscopically determined and theoretically calculated (TD-B3LYP/6-31G*) excitation energies. With the exception of dipyridyl derivative, the calculated lowest unoccupied molecular orbital (LUMO) level of the investigated molecules changes within a narrow range (from -2.63 to -2.41 eV), in line with the electrochemical data, which show a reversible reduction process with the redox potential varying from -1.23 V to -1.33 V (vs. Fc/Fc(+)). The electrochemically determined positions of the LUMO levels are consistently lower by 0.9 to 1.2 eV with respect to the calculated ones. All molecules readily crystallize. Single crystal studies of 3,6-bis(2,2'-bithien-5-yl)-1,2,4,5-tetrazine show that it crystallizes in a P2(1)/c space group whose structural arrangement is not very favorable to the charge carriers flow within the crystal. Powder diffraction studies of other derivatives have shown that their structural organization is sensitive to the position of the solubilizing substituent. In particular, the presence of alkyl groups attached to C(α) carbon in the terminal thienyl ring promotes the formation of a lamellar-type supramolecular organization.

International audience; Hybrid materials consisting of CdSe nanocrystals (CdSe NCs) and 7-(4,4″-dioctyl-2,2′:5′,2″-terthiophene-3′-yl)heptanoic acid (TTHA) or its high molecular analogue--poly(7-(4,4″-dioctyl-2,2′:5′,2″-terthiophene-3′-yl)heptanoic acid) (PTTHA) have been prepared from TOPO capped NCs via ligand exchange. Detailed spectroscopic and spectroelectrochemical (UV-vis-NIR, Raman) studies of these hybrids enabled us to determine the alignment of the HOMO and LUMO levels of their components. Since, for NCs of 3.7nm, the alignment of the energy levels in both hybrids is staggered, the elaborated new materials are of potential use in photovoltaic devices. In the CdSe-PTTHA hybrid material a uniform distribution of the NCs within the polymer matrix is evidenced by TEM...

Strictly monodispersed fractions of two types of regioisomers of increasing molecular mass, namely, oligomers of 3,3′′-dioctyl-2,2′:5′,2′′-terthiophene (3,3′′DOTT) and 4,4′′-dioctyl-2,2′:5′,2′′-ter...

Three groups of naphthalene bisimides were synthesized and comparatively studied, namely, alkyl bisimides, alkylaryl ones, and novel bisimides containing the alkylthienyl moiety in the N-substituent. The experimental absorption spectra measured in CHCl(3) exhibit one intensive absorption band that is uniformly detected in the spectral range of 340 to 400 nm for all studied molecules. This band consists of three or four vibronic peaks. The introduction of an alkylthienyl group results in the appearance of an additional band (in the spectral range from 282 to 326 nm, depending on the position of the substituent) that can be ascribed to the pi-pi* transition in the thienyl chromophore. The minimal substituent effect on the lowest electronic transitions was explained using the quantum chemical calculations based on the time-dependent density functional theory. The investigation of the shapes of frontier orbitals have also shown that the oxidation of bisimides containing thiophene moiety is primary connected with the electron abstraction from the thienyl ring. To the contrary, the addition of an electron in the reduction process leads to an increase in the electron density in the central bisimide core. As shown by the electrochemical measurements, the onset of the first reduction potential (so-called "electrochemically determined LUMO level") is sensitive toward the type of the substituent being shifted from about -3.72 eV for bisimides with alkyl substituents to about -3.83 eV for alkylaryl ones and to about -3.94 eV for bisimides with thienyl groups. The presence of the thienyl ring also lowers the energy difference between the HOMO and LUMO orbitals. These experimental data can be well correlated with the DFT calculations in terms of HOMO/LUMO shapes and energies. Taking into account the low position of their LUMO level and their highly ordered supramolecular organization, the new bisimides are good candidates for the use in n-channel field effect transistors, operating in air. The fabricated "all organic" transistors show effective charge carrier mobilities in the range 10(-2) to 10(-4) cm(2) V(-1) s(-1) and the ON/OFF ratios exceed 10(5) for the majority of cases.

A series of alkyl- or alkylphenyl-1,4,5,8-naphthalenetetracarboxylic-1,4:5,8-bisimides together with the comparative series of the corresponding 3,4,9,10-perylenetetracarboxylic-3,4:9,10-bisimides have been synthesized and characterized by cyclic voltammetry. The naphthalene bisimides family shows a clear dependence of its first reduction potential – corresponding to the LUMO level – on the nature of the N-substituent. Naphthalene bisimides containing alkylphenyl groups undergo the first 1e reduction at potentials of ca. 100 mV higher than those with alkyl groups ( ca. −900 mV vs ca. −1000 mV with respect to Fc/Fc + couple). No effect of the nature of the substituent is observed for the corresponding perylene bisimide series. Due to their improved solution processibility the synthesized organic semiconductors can be used for the fabrication of all organic, flexible n-channel field effect transistors (OFETs) through spin coating and printing techniques, without the necessity of the use of vacuum deposition techniques. The best of the fabricated transistors, operating in air show the charge carriers mobility of 4 × 10 −2 cm 2 /(V s) and the ON/OFF ratio equal to 4.5 × 10 5 .

Alternating linear and branched poly(m−p-anilines) and poly(m−p−p-anilines) have been synthesized via palladium-catalyzed amination reactions. Polymers were oxidized to radical cations either chemically or electrochemically. The presence of radical cations was manifested by the appearance of two and three new bands in the UV−vis−NIR spectra of poly(m−p-anilines) and poly(m−p−p-anilines), respectively. EPR spectra of frozen solutions of partially oxidized polymers confirmed the formation of high-spin states for all polymers studied.

A novel concept of tailoring potentiometric responses of all-solid-state ion-selective electrodes was introduced. The effect of composition and resulting properties of the conjugated polymer transducer, placed between the electrode support and ion-selective membrane, on analytical characteristic of obtained sensors was studied.

Poly(3,3″-dioctyl-2,2′∶5′,2″-terthiophene), obtained from its corresponding monomer by oxidative polymerization with FeCl3, has been fractionated into five fractions of reduced polydispersity, covering the Mn range from 1.50 kDa to 10.50 kDa (measured vs. polystyrene standards). The effect of Mn on spectroscopic, electrochemical, spectroelectrochemical and electrical transport properties has been investigated. Fractions of growing Mn show an increasing bathochromic shift of the band originating from the π–π* transition in the neutral polymer with the appearance of a clear vibrational structure for the two highest molecular fractions. The onset of oxidative doping determined from the cyclic voltammogram shifts towards lower potentials with increasing molecular weight. A similar trend is observed for doping induced near infrared bands, which shift towards lower energies (higher wavelengths) with increasing molecular weight and appear at lower potentials in spectroelectrochemical experiments. Finally, a comparison of the FET mobility in two transistors fabricated under identical conditions from polymer fractions differing in their molecular weight shows that a ca. fourfold increase of Mn (from 2.40 kDa to 10.50 kDa) results in a two orders of magnitude increase in the carriers’ mobility (from μsat = 4 × 10−5 cm2 V−1 s−1 to μsat = 2 × 10−3 cm2 V−1 s−1). The obtained results underline the importance of the control of the macromolecular parameters in the preparation of electronic and electrochemical devices from poly(3,3″-dioctyl-2,2′∶5′,2″-terthiophene).

We describe the preparation of solution-processible hybrid polymers, consisting of a polythiophene main chain and randomly distributed alkyl and oligoaniline side groups. The proposed procedure involves three steps: copolymerization of alkyl- and ester-group-substituted thiophenes to give the precursor polymer, followed by the hydrolysis of the pendant ester groups and aniline tetramer grafting through an amidation reaction. The proposed method is more versatile than previously used copolymerization procedures because higher tetraaniline grafting levels can be obtained. The postfunctionalized polymer is electrochemically active both in its oligoaniline part and in its conjugated polythiophene main chain. As shown by complementary voltammeric and UV−vis−NIR and Raman spectroelectrochemical studies, the polymer can be electrochemically doped selectively in its side oligoaniline chains or globally in the main chain as well as in the side chains. Selective side-chain doping can also be achieved chemically th...

Voltammetric and spectroelectrochemical behavior of two newly synthesized conjugated polymers, which show the same chemical constitution but different type of regioregularity, is compared. These are poly(fluorenone- alt -dioctyl bithiophene)s in which the alkylthiophene rings are either head to head (HH) or tail to tail (TT) coupled, termed PFDOBT-HH and PFDOBT-TT, respectively. Both polymers can be electrochemically p- and n-doped and show the electrochemical energy gap ( E g el ) of the order of 2 eV. In the oxidation side of the voltammogram PFDOBT-HH gives a relatively narrow anodic peak with a maximum at E = 0.78 V versus Fc/Fc + . The corresponding peak of PFDOBT-TT is much broader with the maximum shifted to slightly lower potentials ( E = 0.74 V versus Fc/Fc + ). UV–vis-NIR and Raman spectroelectrochemical studies confirm that the oxidative doping of PFDOBT-TT starts at lower potentials and indicate significant differences in the anodic oxidation in both cases. In PFDOBT-HH the doping is sequential, which means that it starts by the oxidation of the bithiophene sub-units and is completed by the oxidation of the fluorenone ones. In the case of PFDOBT-TT both sub-units are doped simultaneously.

The paper presents the design of all-solid-state potassium microsensors for flow analysis. The sensors are based on Ag planar electrodes as transducers (without internal electrolyte or poly(2-hydroxyethyl methacrylate) (polyHEMA) layer) and ion-selective membranes with the addition of conducting polymers doped with organic acids. The performance of the microsensors containing three conducting polymers: polyaniline (PANI), polyanisidine (PANIZ), and polypyrrole (PPy) in a membrane were determined. The best results, i.e. the highest potassium selectivity in comparison with the sensors based on internal electrolyte immobilized in polyHEMA layer and good signal stability (significantly better than for sensors without the addition of conducting polymers) were obtained for microsensors containing polypyrrole in plasticized PVC membranes.

Oxidative polymerization of pyrrole in the presence of salts of two diesters of sulfosuccinic acid, namely sodium di(ethylhexyl)sulfosuccinate(abbreviated as NaDEHSS)or sodium dihexylsulfosuccinate(abbreviated as NaDHSS)have been investigated. It has been demonstrated that the processibility of the resulting polymer depends on the selection of an appropriate oxidant/dopant couple. If ammonium peroxydisulfate is used as the oxidizing agent the resulting polypyrrole combines solution processibility with spectroscopic and spectroelectrochemical properties of classical intractable doped polypyrrole. For these reasons polypyrrole doped with sulfosuccinate anions can be considered as a very promising material for the fabrication of polymer modified electrodes in various sensing devices or as a material for the fabrication of hole transporting layers in polymer photovolatic cells.

We demonstrate that similarly as in the case of poly(pyrrole), diesters of sulfosuccinic acid containing alkyl or alkoxy substituents can serve as dopants inducing solution processibility of poly(aniline) (PANI). Free-standing films of PANI doped with sulfosuccinates, cast from 2,2′-dichloroacetic acid, show excellent thermal stability and electrical conductivity exceeding 100 S cm −1 which in addition is metallic in character down to 230 K.