Luminescent organic radicals are among the most promising materials for spintronics, upconversion, red and near infrared (NIR) organic light-emitting diodes suffering from the spin-statistics limitations. However, the number of emissive radicals applied in electronic devices is limited, and their design principles are still under discussion. Here we designed, synthesized and studied a series of tris(2,4,6-trichlorophenyl)methyl (TTM) radicals with thiophene-based donors. The radicals were synthesized via cross-coupling reaction of a convenient monobromo-substituted TTM precursor followed by proton elimination and oxidation. Our DFT calculations and experimental data indicate that the HOMO energy of the donor strongly affects the radical emission properties. The radical with the highest optical gap demonstrated deep red electroluminescence and photoluminescence with a quantum yield of up to 12%. The photostability of radicals was found to increase dramatically with substitution, and, according to the proposed mechanistic picture, the spin density on chlorine atoms, and the energy and lifetime of the lowest excited state, D1, control the photodegradation rate. Our results not only extend the pool of the luminescence radicals but also provide clear physical and chemical insights into their fundamental structure-property relations and may serve as the basis for future molecular design of highly stable and emissive radicals.

Impact of fluorination on crystal and molecular structure, heteroatom reactivity, and solid-state magnetic properties of thermally-stable π-radicals is studied experimentally and computationally with 1,3,2-benzodithiazolyl 1· and its 4,7-difluoro, 4,5,6,7-tetrafluoro, and 4,7-difluoro-5,6-(hexafluoropropane-1,3-diyl) derivatives 2·-4·, respectively. Radicals 2·-4· are isolated by vacuum thermolysis of their unusual covalent 2:1 adducts with 7,7,8,8-tetracyanoquinodimethane. The impact of fluorination on reactivity is evidenced by transformation of 2·-4· and 2+-4+ into corresponding 2H-1-oxo-1,3,2-benzodithiazoles under the influence of air's or solvents' moisture; back transformation into the cations under the action of protic acids; and formation of a paramagnetic molecular complex between 3· and naphthalene, whereas 1· and octafluoronaphthalene do not exhibit complexation. The crystal structures of 3· and 4· reveal a novel packing motif featuring radical pairs linked by four-center interactions that stack into offset π-columns, forming a unique zip-π-stack synthon that incorporates head-over-tail π-pairs of radicals. Despite the formation of π-pairs, polycrystalline 3· and 4· display a nonzero effective magnetic moment that rises with temperature above 200 K, although the values remain significantly lower than those of the high-temperature polymorphs of magnetically-bistable 1· and 2·. This behavior can be rationalized by different magnetic topologies and values of spin exchange between the radicals.

While fluorene-containing materials are widely used in organic optoelectronics as bright emitters and hole semiconductors, their diazafluorene analogues have been poorly explored, though their nitrogen atoms could result in electron transport and bring sensory abilities. Here, we report the synthesis, characterization, and detailed study of a series of 4,5-diazafluorene-derivatives with different donor/acceptor substituents and organic semiconductors based on these molecules. The crystal structures of all the materials were solved by X-ray diffraction, indicating the presence of extensive π-stacking and anisotropic charge-transfer pathways. The materials were applied as active layers in single-crystal and thin-film organic field-effect transistors (OFETs) demonstrating air-stable electron transport with charge-carrier mobility up to 0.02 cm2/(V s) for (2,7-diphenyl-4,5-diazafluorene-9-ylidene)malononitrile (P-DAF-CN). Moreover, P-DAF-CN thin-film OFETs were employed as gas sensors demonstrating a sensor response toward sub-ppm concentrations of hydrogen sulfide. 4,5-Diazafluorene-based materials are shown to be promising organic semiconductors on the way to high-performance air-stable n-channel OFETs and electronic nose applications.

Neutral M and radical-ion [M](-) and [M](+) states of phenanthro- (1, 2)/dibenzoquinoxalino- (3, 4) fused 1,2,5-chalcogenadiazoles are studied; chalcogen = S (1, 3), Se (2, 4). Experimentally, 1-4 are characterized by simultaneous thermogravimetry - differential scanning calorimetry, spectroelectrochemistry and optical (UV-Vis-NIR/FL) spectroscopy, 2-4 by cyclic voltammetry (CV) for reduction and oxidation, and [M](-) by electron paramagnetic resonance ([M](+) were not detected). Compounds 3, 4 and [M](-) (in the form of [K(18-crown-6)](+) salts; M = 1, 3) are characterized by X-ray diffraction (all are planar), and [M](-) (M = 1-4) by UV-Vis-NIR. Theoretically, M and [M](-) (M = 1-4) are specified by density functional theory (DFT) calculations. As compared with the archetypal 2,1,3-benzothiadiazole (5), in 1-4 the pi-extension and replacement of S by Se jointly lead to increase of DFT adiabatic electron affinity (0.8 -> 2.1 eV), decrease of the absolute values of CV potentials (-1.5 -> -0.5 V), broadening and bathochromic shifts of UV-Vis (similar to 310 -> similar to 420 nm) and FL (similar to 380 -> similar to 470 nm) bands. DFT adiabatic ionization energy of 1-4 of similar to 7.9 eV is invariant to their structure (5: 8.7 eV). FL spectra of 1-4 exhibit small Stokes shifts; and those of 2 and 3, vibronic structures. The estimated excited-state lifetime tau(1) is similar to 1 ns (ns) for 3 and 4, and similar to 2 ns for 2, while long-time component tau(2) is similar to 9 ns for 2 and similar to 7 ns for 3. The findings suggest that 1-4 are promising organic pi-dyes/non-fullerene electron acceptors for small-molecule optoelectronics.

A series of dithioazaspiroacrylamide monomers containing sulfur atoms in the cyclic structure and having high refractive indices have been synthesized. Transparent polymer films were obtained from these monomers. The refractive indices of monomers and polymers obtained from them were measured (nD25$$ {n_D}<^>{25} $$ = 1.52-1.67) and their Abbe numbers were also measured (VD = 26-55). The glass transition temperatures of polymers were measured Tg = 45-155 degrees C. Polymers consisting of spirocyclic unbranched units showed the highest refractive indices and high transparency, which seems promising for use in photolithography, holography, elements of polymer, and waveguide optics.Highlights From 4-piperidone, dithioazaspiroacrylae monomers was obtained. Transparent polymer films with high refractive indices are obtained. Polymer with spirocyclic units showed high refractive index and Abbe number.

2-[4-(2-Methacryloyl)-piperazine-1-ylmethyl]-9H-thioxanthen-9-one-S,S-dioxide 1, an electrochemically active monomer, has been synthesised from 2-(piperazine-1-ylmethyl)-9 & Ncy;-thioxanthen-9-one-S,S-dioxide and methacryloyl chloride. Subsequent radical copolymerisation of the synthesised compound with methyl methacrylate leads to an electroactive copolymer (PMMA-co-ThxSO(2)) with the ratio of methyl methacrylate fragments in the chain to the pendant (side) groups of the 9 & Ncy;-thioxanthen-9-one S,S-dioxide structure equal to 95 : 5, respectively. It has been shown by cyclic voltammetry that the electrochemical reduction (ECR) of 1 in acetonitrile (MeCN) is a two-electron and two-stage process, with the formation of long-living radical anion at the first one-electron stage and unstable dianion at the second stage. Electrochemical reduction of PMMA-co-ThxSO(2) is due to the reductive electrochemical activity of the pendant groups, and its mechanism is similar to the ECR of monomer 1. This compound is a polymer with pendant groups that play the role of efficient electron traps during charge transport inside the thin copolymer film, and it can be used in the resistive memory technologies (ReRAM - Resistive Random Access Memory) as the active working layer of memristors.

Bioengineered vascular grafts (VGs) have emerged as a promising alternative to the treatment of damaged or occlusive vessels. It is thought that polyurethane (PU)-based scaffolds possess suitable hemocompatibility and biomechanics comparable to those of normal blood vessels. In this study, we investigated the properties of electrospun scaffolds comprising various blends of biostable polycarbonate-based PU (Carbothane (TM) 3575A) and gelatin. Scaffolds were characterized by scanning electron microscopy, infra-red spectroscopy, small-angle x-ray scattering, stress-loading tests, and interactions with primary human cells and blood. Data from in vitro experiments demonstrated that a scaffold produced from a blend of 5% Carbothane (TM) 3575A and 10% gelatin has proven to be a suitable material for fabricating a small-diameter VG. A comparative in vivo study of such VGs and expanded polytetrafluoroethylene (ePTFE) grafts implanted in the abdominal aorta of Wistar rats was performed. The data of intravital study and histological examination indicated that Carbothane-based electrospun grafts outclass ePTFE grafts and represent a promising device for preclinical studies to satisfy vascular surgery needs.

A series of asymmetrically fluorinated 2,2 '-bibenzimidazoles '-bibenzimidazoles were obtained by reaction of benzimidazole-2carboxylic acid with fluorinated 1,2-phenylenediamines in polyphosphoric acid at elevated temperature. The tautomers of fluorinated 2,2 '-bibenzimidazoles '-bibenzimidazoles with a predominance of isomers containing F atoms in distant position relative to the NH group of the benzimidazole fragment are detected in DMSO-d6 using NMR spectroscopy. The ratio of tautomers depends on the number and arrangement of F atoms in the initial fluorinated 1,2-phenylenediamines. Under similar conditions fluorinated 1,2-phenylenediamines in the presence of benzimidazole-2-carboxylic acid, but without its participation as well as without it, give fluorinated phenazine2,3-diamines. The direction of transformation of fluorinated 1,2-phenylenediamines depends on the number and position of F atoms. Under similar conditions phenazine-2,3-diamine is not formed from non-fluorinated 1,2-phenylenediamine, but it is obtained with the presence of fluorinated 1,2-phenylenediamines. When fluorinated 1,2phenylenediamines contain F atoms simultaneously at the positions 4 and 5, the hydrodefluorination of initial fluorinated 1,2-phenylenediamines occurs, resulting in less fluorinated 2,2 '-bibenzimidazoles '-bibenzimidazoles and phenazine-2,3diamines. Hydrodefluorination of fluorinated 1,2-phenylenediamines in a polyphosphoric acid at elevated temperatures is the first example of the hydrodefluorination of fluorinated aromatic compounds containing strong donor substituents, such as amino groups. Polyphosphoric acid is shown to be a suitable medium for redox processes.

A series of novel N-methylquinoline-2-ones with a fluorinated benzene ring (with and without Br atoms) is prepared by the interaction of halogenated quinoline-2-ones with CH3I in methanol in the presence of KOH. The molecular and crystal structures of these compounds are determined by XRD. It is shown that the main structure-forming interaction in the crystals of these compounds is π-staking, while the main supramolecular motif is formed by the π-stacks of molecules resulting from the expected π–π-interaction between the electron-deficient haloarene species and a more electron-donating pyridinone ring (fluoroarene–fluoroarene interactions are also present). In all cases, the intra-stack molecular packing changes noticeably upon the transition from fluorinated N-methylfluoroquinoline-2-ones to their bromine-containing derivatives: the lateral shift increases, the Br…π interactions appear. The Br atoms form Br…F or Br…Br intermolecular interactions.

Aggregation induced emission materials are highly demanded for practical applications in optoelectronics, sensorics, material science and bio-imaging. However, highly torsionally-flexible and hybrid organic/inorganic AIE materials are limited. In this work we designed, synthesized and comprehensively studied AIE-active bis((9H-(4,5-diazafluoren)-9-ylidene)methyl)arylenes demonstrating high torsional freedom coupled with electron-accepting character and N,N’-chelating ability. One-rotor nonplanar structure of phenylene-linked derivative (BDFMP) allowed us to demonstrate its polymorphic diversity both in neat state and in coordination polymers. X-ray diffraction analysis indicated formation of crystals with extensive π-stacking interactions and slipped/side-by-side packing motifs, the former crystals demonstrating a photoluminescence quantum yield of 25%. The reaction of both BDFMP/BDFMT with ZnCl2 resulted in formation of unique coordination polymers and porous metal organic frameworks with photoluminescence sensitive to heating and (de/re)hydratation. The latter effect was exploited for security painting and anti-counterfeiting demonstration.

The transverse charge transport mechanism in a specially synthesized novel methyl methacrylate copolymer containing 2 % electron -accepting 9H-thioxanthene-9-one side groups (poly(MMA-co-ThS)) has been studied experimentally and theoretically. These side groups are shown to be deep electron traps. The charge transport in poly(MMA-co-ThS) is governed by the model of phonon -assisted tunneling between traps. The optical ionization trap energy (Wopt = 1.8 eV), independently determined by a reduction spectroelectrochemical method, confirms the validity of the phonon -assisted tunneling model used to describe charge transport in organic dielectrics with high content of electron traps.

An electro-active copolymer of methyl methacrylate and 2-((4-acroylpiperazine-1-yl)methyl)-9H-thioxanthene-9-one (poly(MMA-co-ThS)) was synthesized by radical polymerization. The copolymer has good solubility in most organic solvents, thermal stability up to 282 °C and excellent ability to form thin films on silicon wafers. Poly(MMA-co-ThS) films exhibited an electrochemical and electrochromic activity resulting in the formation of long-lived radical anion states of pendant thioxanthone groups inside the film. These states exhibit optical transitions in the visible region as a broad optical absorption band, 500<λ<900 nm (1.38<Wopt(ThS)<2.48 eV) with a maximum at λmax=675 nm (1.84 eV). Using temperature measurements of the current-voltage characteristics of p-Si(100)/poly(MMA-co-ThS)/Al devices, it was shown that the charge transport in the film occurs by a multiphonon mechanism, which is quantitatively described by the Nasyrov-Gritsenko model of phonon-assisted tunneling between traps. The value of the optical transition energy of the trap, determined by the Nasyrov-Gritsenko model, Wopt=1.8 eV, is in a good agreement with Wopt(ThS), confirming the nature of the traps as 9H-thioxanthen-9-one structures. The n++Si(100)/poly(MMA-co-ThS)/Al memory device exhibited a memristive effect (reversible ON/OFF switching of the device) with an initial "forming" cycle followed by repetitive memory cycles characterized by bipolar switching.

Polycondensation of perfluorobiphenyl with 1,4-dihydroxythioxanthen-9-one resulted in the title highly thermally stable polyether containing the thioxanthenone-type electron acceptor in-chain blocks in its structure. Model resistive memory devices based on it as the active medium exhibited a bipolar switching memristive effect with a 4-order difference in resistance between the low and high resistance states. The charge transport in this polyether is quantitatively described by the Nasyrov-Gritsenko model of phonon-assisted electron tunneling between traps.

Aggregation-induced emission (AIE) materials are in high demand for various practical applications in organic optoelectronics, sensorics, and bioimaging applications. Typically, these materials were designed to have nonplanar molecular structures with at least one-rotor moiety and intramolecular motion/rotation. Here, we designed, synthesized, and comprehensively studied 1,4-bis((9H-(1,8-diazafluoren)-9-ylidene)methyl)phenylene (1,8-BDFMP), demonstrating a unique and counterintuitive behavior. Despite the rigid and planar molecular structure caused by the effective conjugation and intramolecular NH interactions coupled with strong H-aggregation, it clearly demonstrated AIE activity. The photoluminescence quantum yield of the luminophore in solution was only 0.04%, whereas its single crystals, despite strong pi-stacking intermolecular interactions, were emissive with a photoluminescence quantum yield of 10%. The charge transport in 1,8-BDFMP single crystals and drop-cast films was evaluated. The detailed photophysics of 1,8-BDFMP was studied both experimentally and computationally. The conical intersection of the S-1-S-0 states was demonstrated to be the main nonradiative deactivation pathway in the monomeric state.

The title radical R⋅, synthesized by reduction of the corresponding cation R+, is thermally stable up to ~380 K in the crystalline state under anaerobic conditions. With SQUID magnetometry, single-crystal and powder XRD, solid-state EPR and TG-DSC, reversible spin-Peierls transition between diamagnetic and paramagnetic states featuring ~10 K hysteretic loop is observed for R⋅ in the temperature range ~310-325 K; ΔH=~2.03 kJ mol-1 and ΔS=~6.23 J mol-1 K-1. The transition is accompanied by mechanical movement of the crystals, i. e., by thermosalient behavior. The low-temperature diamagnetic P-1 polymorph of R⋅ consists of R⋅2 π-dimers arranged in (…R⋅2…)n π-stacks; whereas the high-temperature paramagnetic P21/c polymorph, of uniform (…R⋅…)n π-stacks. With the XRD geometries, CASSCF and broken-symmetry DFT jointly suggest strong antiferromagnetic (AF) interactions within R⋅2 and weak between R⋅2 for the (…R⋅2…)n stacks; and moderate AF interactions between R⋅ for the (…R⋅…)n stacks. The fully hydrocarbon archetype of R⋅ does not reveal the aforementioned properties. Thus, the fluorinated 1,3,2-benzodithiazolyls pave a new pathway in the design and synthesis of metal-less magnetically-bistable materials.

Взаимодействием галогенированных хинолин-2-онов с СН3I в метаноле в присутствии KOH получена серия новых фторированных по бензольному кольцу N-метилхинолин-2-онов, содержащих атомы Br и без них. Методом РСА определены их молекулярные и кристаллические структуры. Установлено, что основным структурообразующим взаимодействием в кристаллах этих соединений является π-стекинг. Основным супрамолекулярным мотивом являются π-стопки молекул, возникающие из-за ожидаемого π-π взаимодействия электрон-дефицитного галогенаренового фрагмента и более электрон-донорного пиридинонового кольца, но присутствуют и взаимодействия фторарен-фторарен. Во всех случаях при переходе от фторированных N-метилфторхинолин-2-онов к их бромсодержащим производным заметно изменяется внутристопочная упаковка молекул: увеличивается латеральный сдвиг, появляются Br…π взаимодействия. Атомы Br образуют межмолекулярные взаимодействия Br…F или Br…Br.

The influence of the oxygen and sulfur atoms in the spirocycles (–O–CH2–CH2–O–, –O–CH2–CH2–S–, –S–CH2–CH2–S–) of the spirocyclic acryloylpiperidonyl monomers on the thermomechanical and holographic properties of the photopolymer material was studied. The conversion of double bonds of monomers during UV polymerization was determined by IR spectroscopy method. The refractive indices of spirocyclic monomers and photopolymers were measured. The phase transmission diffraction gratings were recorded in photopolymer materials containing the spirocyclic monomers. The highest modulation of the refractive index was observed in the photopolymer based on the acryloylpiperidonyl dithiaazaspiroheterocyclic (–S–CH2–CH2–S–) monomer. It was shown that light scattering in the photopolymer at hologram recording has noticeable negative contribution and for the decrease in the diffraction efficiency of holograms. The phase incompatibility of the polymer matrix and formed photopolymer is considered as the reason of the light-scattering growth.

Fibrous polyurethane-based scaffolds have proven to be promising materials for the tissue engineering of implanted medical devices. Sterilization of such materials and medical devices is an absolutely essential step toward their medical application. In the presented work, we studied the effects of two sterilization methods (ethylene oxide treatment and electron beam irradiation) on the fibrous scaffolds produced from a polyurethane-gelatin blend. Scaffold structure and properties were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), infrared spectroscopy (FTIR), a stress-loading test, and a cell viability test with human fibroblasts. Treatment of fibrous polyurethane-based materials with ethylene oxide caused significant changes in their structure (formation of glued-like structures, increase in fiber diameter, and decrease in pore size) and mechanical properties (20% growth of the tensile strength, 30% decline of the maximal elongation). All sterilization procedures did not induce any cytotoxic effects or impede the biocompatibility of scaffolds. The obtained data determined electron beam irradiation to be a recommended sterilization method for electrospun medical devices made from polyurethane-gelatin blends.

In this study, we report the synthesis of a new fluorinated vinyl monomer, that is, pentafluorophenyl vinyl ketone [1-(pentafluorophenyl)prop-2-en-1-one], its radical polymerization and copolymerization with styrene, methyl vinyl ketone, or phenyl vinyl ketone. The obtained homo- and co-polymers were subjected to thermal analysis, contact angle measurement, and an assay of resistance to UV irradiation. The results showed that the poly(pentafluorophenyl vinyl ketone) has a slightly greater contact angle and a lower temperature of the maximum decomposition rate when compared to the nonfluorinated analog: poly(phenyl vinyl ketone).