Real-time manipulation of light in a diffractive optical element made with an azomaterial, through the light induced reconfiguration of its surface based on mass transport, is an ambitious goal that may enable new applications and technologies. The speed and the control over photopatterning/ reconfiguration of such devices are critically dependent on the photoresponsiveness of the material to the structuring light pattern and on the required extent of mass transport. In this regard, the higher the refractive index (RI) of the optical medium, the lower the total thickness and inscription time can be. In this work, we explore a flexible design of photopatternable azomaterials based on hierarchically ordered supramolecular interactions, used to construct dendrimer-like structures by mixing specially designed sulfur-rich, high-refractive-index photoactive and photopassive components in solution. We demonstrate that thioglycolic-type carboxylic acid groups can be selectively used as part of a supramolecular synthon based on hydrogen bonding or readily converted to carboxylate and participate in a Zn(II)-carboxylate interaction to modify the structure of the material and fine-tune the quality and efficiency of photoinduced mass transport. Compared with a conventional azopolymer, we demonstrate that it is possible to fabricate high-quality, thinner flat diffractive optical elements to reach the desired diffraction efficiency by increasing the RI of the material, achieved by maximizing the content of high molar refraction groups in the chemical structure of the monomers.

Eight novel isoindigo (iI) based small molecules have been successfully synthesized. Their molecular structure consists of an electron acceptor iI core symmetrically linked to two furan (F-series) or thiophene (T-series) rings and end-functionalized with four auxiliary electron withdrawing groups (EWGs) of different strength. The optical properties of the dyes in chloroform solution are uniformly modulated by the terminal EWGs so that absorption maxima wavelengths move to higher values as the EWG's strength increases. A computational (DFT level) analysis provides useful information on the electronic structure of the dyes: upon photoexcitation, the electron density moves away from iI core or towards it according to the different EWG considered. Optical analysis is performed on dyes' thin films as well and a general broadening and red shift of the absorption is observed as compared to the behaviour in solution; all the dye's thin films are characterized by narrow bandgaps (<1.60 eV) and diffused absorption of most of the visible light. From XRD diffraction analysis performed on drop casted films of the dyes, it is possible to observe a lamellar organization in the solid phase with lamellae width clearly linked to the nature of the terminal EWG. HOMO and LUMO energies of the dyes, determined by cyclic voltammetry analysis performed on dyes' thin films, show very stable LUMO and HOMO energy levels, suggesting, respectively, a tendency to act as n-type semiconductors and a very good thermo-oxidative stability. The dyes are finally employed as active layers in organic field-effect transistors to study their charge transport properties: all of them display unipolar n-type charge transport with the presence of the electron accumulation phenomenon under the application of positive gate voltages. For one of the dye, mobility (mu) up to 10-2 cm2/V center dot s was measured, whereas values around 10-3 cm2/V center dot s were found for the others.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Three novel diketopyrrolopyrrole (DPP) based small molecules have been synthesized and characterized in terms of their chemical-physical, electrochemical and electrical properties. All the molecules consist of a central DPP electron acceptor core symmetrically functionalized with donor bi-thienyl moieties and flanked in the terminal positions by three different auxiliary electron-acceptor groups. This kind of molecular structure, characterized by an alternation of electron acceptor and donor groups, was purposely designed to provide a significant absorption at the longer wavelengths of the visible spectrum: when analysed as thin films, in fact, the dyes absorb well over 800 nm and exhibit a narrow optical bandgap down to 1.28 eV. A detailed DFT analysis provides useful information on the electronic structure of the dyes and on the features of the main optical transitions. Organic field-effect transistors (OFETs) have been fabricated by depositing the DPP dyes as active layers from solution: the different end-functionalization of the dyes had an effect on the charge-transport properties with two of the dyes acting as n-type semiconductors (electron mobility up to 4.4 . 10(-2) cm(2)/V . s) and the third one as a p-type semiconductor (hole mobility up to 2.3 . 10(-3) cm(2)/V . s). Interestingly, well-balanced ambipolar transistors were achieved by blending the most performant n-type and p-type dyes with hole and electron mobility in the order of 10(-3) cm(2)/V . s

Four novel diketopyrrolopyrrole (DPP) derivatives have been synthesized and characterized: the dyes are based on a DPP electron acceptor core symmetrically functionalized with donor bi-furyl moieties and end capped with four different auxiliary electron-acceptor groups. Because of the alternation along the molecular backbone of electron acceptor and donor groups, all the dyes are characterized by optical absorption maxima approaching or exceeding 700 nm. In the solid state, this optical behavior determines for all the dyes a very low optical bandgap ranging from 1.57 eV to 1.29 eV, while electrochemical characterization shows a clear dependence of the LUMO energies on the strength of the auxiliary electron-acceptor groups. All the dyes are characterized by stable LUMO energies suitable for their application as n-type semiconductors. Organic field-effect transistors based on the reported compounds display actually n-type behavior and, in three cases, a very interesting and balanced ambipolar charge transport behavior was moreover observed.

Correction for ‘Space-charge accumulation and band bending at conductive P3HT/PDIF-CN2 interfaces investigated by scanning-Kelvin probe microscopy’ by Federico Chianese et al., J. Mater. Chem. C, 2021, DOI: 10.1039/d1tc04840f.

The synthesis and characterization of the N-rich bis(triazole) compound 1H,4′H-[3,3′-bis(1,2,4-triazole)]-4′,5,5′-triamine (C4H7N9) with a N content of 69.6% by weight is reported. The compound exhibits a rich acid–base behavior because it can accept up to two protons, forming a monocation and a dication, and can lose one proton, forming an anion. Measurement of the acid constants has shown that there exist well-defined pH intervals in which each of the four species is predominant in solution, opening the way to their isolation and characterization by single-crystal X-ray analysis as salts with different counterions. Some energetic salts of the monocation or dication containing oxidizing inorganic counterions (dinitramide, perchlorate, and nitrate) were also prepared and characterized in the solid state for their sensitivity. In particular, the neutral compound shows a very remarkable thermal stability in air, with Td = 347 °C, and is insensitive to impact and friction. Salts of the dication with energetic counterions, in particular perchlorate and nitrate, show increased sensitivities and reduced thermal stability. The salt of the monocation with dinitramide as the counterion outperforms other dinitramide salts reported in the literature because of its higher thermal stability (Td = 230 °C in air) and friction insensitiveness.

Charge transfer processes and space charge accumulation phenomena are fundamental topics concerning the technological applications of organic heterointerfaces.

Correction for 'Space-charge accumulation and band bending at conductive P3HT/PDIF-CN2 interfaces investigated by scanning-Kelvin probe microscopy' by Federico Chianese et al., J. Mater. Chem. C, 2021, DOI: 10.1039/d1tc04840f.

A new N-rich triazolo-triazole derivative, 4-methyl-7-(pyrazin-2-yl)-2H-[1,2,4]triazolo[3,2-c][1,2,4]triazole (C8H7N7), bearing a pyrazine residue at 7-position of the triazolo-triazole bicycle, was synthesized, and its acid-base and metal coordination properties were evaluated in solution. The results showed amphoteric behavior and the formation of stable complexes with Cu(ii) and Zn(ii) in pH intervals in which the ligand is neutral or deprotonated. Computational studies were performed in order to evaluate the stability of the different tautomers/conformers of the ligand, and the proton position in the neutral and acidic forms. Single crystal X-ray analysis of the free neutral ligand (2H/s-trans tautomer/conformer), and of its singly protonated (2H-3H/s-trans), doubly protonated (2H-3H-7H/s-trans) and deprotonated forms showed that the influence of the pyrazine ring on the triazolo-triazole system is mainly as electron withdrawing and chelating group, and proton acceptor. Different coordination modes have been evidenced for the neutral and deprotonated ligand. Upon metal coordination, the neutral ligand switches from 2H/s-trans to 3H/s-cis tautomer/conformer forming five-membered chelate rings, while the anionic deprotonated ligand forms six-membered chelate rings in the s-trans conformation. Altogether, five different tautomers/conformers of the ligand were isolated and characterized. In vitro tests confirmed the general antiproliferative activity of triazolo-triazole compounds and the importance of substitution in position 7 for their selectivity.

The hydrolysis reactions of triazolo–triazole derivatives, which are characterized by the presence of substituents of different electronic character (electron donor or acceptor) on the bicycle, in 0.5 mol·dm−3 NaCl as ionic medium, at 25 °C, have been investigated. Acid–base titrations, volumetric or coulometric, have been performed. The pH range investigated is 0.3–12. UV–vis spectra recorded at various pH values showed that the substitution pattern at the bicycle strongly affects the absorption and emission properties of the triazoles. Current/voltage curves recorded at various pH values also indicate that only a cationic monoprotonated species undergoes irreversible reduction at potential values spanning the range − 0.9 V to − 1.3 V (vs. Ag/AgCl), depending on the pH and on the substituent’s nature. Particularly, on the fused-ring N-rich bicycle, with pentafluorophenyl as electron withdrawing group, reduction takes place at a potential of 0.05 V higher than the analogue with aminophenyl electron donor group. The mononuclear complexes formation between Cu(II) and a triazolo–triazole compound has been also highlighted by UV–vis spectra and current/voltage curves recorded at 0.3 < pH < 6.

Here we report the solid-state experimental and computational analysis of naphtho [2,3-c] [1,2,5]thiadiazole (1) and naphtho [2,3-c] [1,2,5]selenadiazole (2) showing that the three different crystal phases of polymorphic 1 and the sole crystal phase of nonpolymorphic 2 are characterized by predominance of some intermolecular motifs over the others. In particular, the intermolecular interactions present in the compounds, pi center dot center dot center dot pi, C-H center dot center dot center dot pi, C-H center dot center dot center dot N, S center dot center dot center dot N, and Se center dot center dot center dot N, are hierarchically ranked, in such a way that in 1 polymorphism is observed, with the three different phases showing different combinations of the intermolecular interactions, while in 2 only the packing that maximizes the strongest intermolecular interaction by far, i.e., chalcogen bond, is observed. Moreover we also show that different packings produce different responses in the solid-state topochemical reactivity of the crystalline compounds, spanning from nonreactive packings to packings producing butterfly dimers. In order to rationalize the different responses, the relevance molecules is suggested, as an important factor, in addition to the known Schmidt's rules for of the transverse parallel shift of solid-state topochemical reactions.

A study of three isomeric compounds containing a phenolic moiety attached to the nitrogen-rich triazolo-triazole bicycle is presented. In the three isomers, the phenolic OH group is in the ortho, meta and para positions. The crystal structure analysis of the meta isomer (C10H9N5O) shows that the 2H-tautomer is present in the crystal and that the molecule adopts a substantially planar geometry. However, the conformation found in the crystal is different compared to the monoprotonated cation of the same compound previously investigated in several salts. The packing of the meta isomer is driven by the formation of strong hydrogen bonds and shows the formation of infinite planar ribbons, parallel to a, formed around 2(1) crystallographic axes. The three isomers were tested against some cancer cell lines and also against normal cell lines. The ortho isomer shows a weak antiproliferative activity, the meta isomer shows significant antiproliferative activity against some cancer lines and no activity against healthy cell lines, and the para isomer is active against all the tested cell lines.

We have prepared new hydroxyphenyl derivatives of [1,2,4]triazolo[3,2-c][1,2,4]triazole and investigated their tautomeric behavior, for the neutral and the monoprotonated forms, either computationally and experimentally in solution and the solid state. The results of our analysis indicate that the tautomeric behavior, in particular for the monoprotonated forms, is strongly dependent on the position of the OH group in the phenyl ring. The different position of the group (ortho, meta, para) has an effect on the relative energy of the various tautomeric forms of the cations but also on their ability to get an optimum packing, which is driven by directional hydrogen bonds. In particular, with the OH in para position, the two tautomers 1H-3H and 2H-3H of the singly protonated form have a similar energy and can be selectively isolated in the solid state with different counterions; with OH in the meta position, though the energy difference between the tautomers is even smaller, only the 2H-3H is present in the solid state, because of optimum packing interactions (hydrogen-bonding pairing); finally, with ortho OH, only the 1H-3H is isolated in the solid state because it has energy significantly lower than 2H-3H.

Mol­ecules of the title compound, C24H8F4N2O8, have Ci point-group symmetry in the crystal, as they lie on crystallographic inversion centres (Z′ = 1/2). The di­fluoro­phenyl ring is disordered over two orientations; the final refined occupancy factors of the two components of disorder are 0.947 (4) and 0.053 (4). In the crystal, some Car—H⋯F inter­actions are present, which involve the most acidic H atom of the mol­ecule.

Molecules of the title compound, C 24 H 8 F 4 N 2 O 8 , have C i point-group symmetry in the crystal, as they lie on crystallographic inversion centres ( Z ′ = 1/2). The difluorophenyl ring is disordered over two orientations; the final refined occupancy factors of the two components of disorder are 0.947 (4) and 0.053 (4). In the crystal, some C ar —H...F interactions are present, which involve the most acidic H atom of the molecule.

Fine control of the tautomeric forms of [1,2,4]triazolo[3,2-c][1,2,4]triazole derivatives in acidic conditions has been achieved by acting on the electronic character of the substituent at position 7 of the heterobicycle and on the counterion. Strong electron releasing or electron withdrawing substituents lead almost exclusively to a single tautomeric form, the 1H-3H or the 2H-3H, respectively. In the case of the phenol substituent, both tautomeric forms are present in comparable amount in solution; the two tautomers can also be selectively precipitated in different crystalline salts using suitable counterions.

A novel semiconductor, the small molecule C6-NTTN, was used to fabricate organic thin film transistors (OTFTs). Different architectures and deposition techniques were employed, together with various surface treatments of the substrate, insulator and metal contacts, whose effect is analyzed through atomic force microscopy. The aim is to investigate the relationship between the process parameters and the electrical performance, with a particular attention to the quality of interfaces between active layers. The proportionality between the charge carrier mobility and the interface trap density was studied.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Organic thin-film transistors (OTFTs) were fabricated using a novel small molecule, C6-NTTN, as the semiconductor layer in several different architectures. The C6-NTTN layer was deposited via both vacuum evaporation at different substrate temperatures and via solution-processing, which yield maximum hole mobilities of 0.16 and 0.05 cm(2)/V . s, respectively. Surface treatments of the substrate, insulator, and metal contacts used for OTFT fabrication employing polymer films and different self-assembled monolayers were investigated. In particular, in bottom-gate devices, the insulator surface hydrophobicity was optimized by the deposition of poly(methyl methacrylate) or hexamethyldisilazane, while in the top-gate geometry, pentafluorobenzenethiol was efficiently used to modify the substrate surface energy and to change the contact work function. Atomic force microscopy analysis was exploited to understand the relationship between the semiconductor thin-film morphology and the device electrical performance. The results shown here indicate an inverse proportionality between the mobility and the interface trap density, with parameters depending especially on semiconductor-insulator interfacial properties, and a correlation between the threshold voltage and the characteristics of the semiconductor-metal interface.