RESUMEN

Low-cost molecular emitters that merge circularly polarized luminescence (CPL) and thermally activated delayed fluorescence (TADF) properties are attractive for many high-tech applications. However, the design of such emitters remains a difficult task. To address this challenge, here, we propose a simple and efficient strategy, demonstrated by the design of pseudochiral-at-metal complexes [Cu(L*)DPEPhos]PF6 bearing a (+)/(-)-menthol-derived 1,10-phenanthroline ligand (L*). These complexes exhibit a yellow CP-TADF with a record-high quantum yield (close to 100%) and high dissymmetry factor (|glum| ~ 1×10-2). Remarkably, the above compounds also show a negative thermal-quenching (NTQ) of luminescence in the 300-77 K range. Exploiting the designed Cu(I) emitters, we fabricated efficient CP-TADF OLEDs displaying mirror-imaged CPL bands with high |gEL| factors of 1.5×10-2  and the maximum EQE of 6.15%. Equally important, using the (+)-[Cu(L*)DPEPhos]PF6 complex, we have discovered that an external magnetic field noticeably suppresses CP-TADF of Cu(I) emitters. These findings are an important contribution to the CPL phenomenon and provide access to highly efficient, low-cost and robust CP-TADF emitters.

RESUMEN

Di(het)aryldiynes smoothly react with N-benzylaldimines in a [4 + 3] cycloaddition manner under the action of the KOBut/DMSO system (60 °C, 30 min) to afford pharmaceutically relevant tetra(het)arylsubstituted 3H-azepines in up to 71% yield. The process involves the addition of azaallyl anions to one of the triple bonds of diynes followed by prototropic isomerization and cyclization of anionic intermediates with participation of the second triple bond. The cascade mechanism is consistent with quantum-chemical analysis (B2PLYP-D3/6-311+G**//B3LYP-D3/6-31+G* + PCM).

RESUMEN

By X-ray diffraction analysis and IR spectroscopy, it was established here that vinyl carbocations C3H5+/C4H7+ with carborane counterion CHB11Cl11- form stable monosolvates C3H5+⋅C3H6/C4H7+⋅C4H8 with molecules of alkenes C3H6/C4H8. They contain molecular group =C+⋯Hδ--Cδ+= with a new type of bond formed by the H atom of the H-C= group of the alkene with the C atom of the C+=C group of the carbocation. The short C+----Cδ+ distance, equal to 2.44 Å, is typical of that of X----X in proton disolvates (L2H+) with an quasi-symmetrical X-H+⋯X moiety (where X = O or N) of basic molecule L. The nature of the discovered bond differs from that of the classic H-bond by an distribution of electron density: the electron-excessive Hδ- atom from the (=)C-H group of the alkene is attached to the C+ atom of the carbocation, on which the positive charge is predominantly concentrated. Therefore, it can be called an inverse hydrogen bond.

RESUMEN

Highly resistant to reduction nitroxides open new opportunities for structural studies of biological macromolecules in their native environment inside living cells and for functional imaging of pH and thiols, enzymatic activity and redox status in living animals. 3,4-Disubstituted nitroxides of 2,2,5,5-tetraethylpyrrolidine and pyrroline series with a functional group for binding to biomolecules and a polar moiety for higher solubility in water and for more rigid attachment via additional coordination to polar sites were designed and synthesized. The EPR spectra, lipophilicities, kinetics of the reduction in ascorbate-containing systems and the decay rates in liver homogenates were measured. The EPR spectra of all 3,4-disubstituted pyrrolidine nitroxides showed additional large splitting on methylene hydrogens of the ethyl groups, while the spectra of similar pyrroline nitroxides were represented with a simple triplet with narrow lines and hyperfine structure of the nitrogen manifolds resolved in oxygen-free conditions. Both pyrrolidine and pyrroline nitroxides demonstrated low rates of reduction with ascorbate, pyrrolidines being a bit more stable than similar pyrrolines. The decay of positively charged nitroxides in the rat liver homogenate was faster than that of neutral and negatively charged radicals, with lipophilicity, rate of reduction with ascorbate and the ring type playing minor role. The EPR spectra of N,N-dimethyl-3,4-bis-(aminomethyl)-2,2,5,5-tetraethylpyrrolidine-1-oxyl showed dependence on pH with pKa = 3, ΔaN = 0.055 mT and ΔaH = 0.075 mT.

Asunto(s)

RESUMEN

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.

RESUMEN

The title compound was synthesized by Ullmann cross-coupling in low yield as the first representative of [n]phenylene containing hydrocarbon and fluorocarbon rings. Stille/Suzuki-Miyaura cross-coupling reactions, as well as substitution of fluorine in suitable starting compounds, failed to give the same product. The geometric and electronic structures of the title compound were studied by X-ray diffraction, cyclic voltammetry and density functional theory calculations, together with Hirshfeld surface and reduced density gradient analyses. The crystal structure features head-to-tail π-stacking and other fluorine-related secondary bonding interactions. From the nucleus-independent chemical shifts descriptor, the four-membered ring of the title compound is antiaromatic, and the six-membered rings are aromatic. The Janus molecule is highly polarized; and the six-membered fluoro- and hydrocarbon rings are Lewis π-acidic and π-basic, respectively. The electrochemically-generated radical cation of the title compound is long-lived as characterized by electron paramagnetic resonance, whereas the radical anion is unstable in solution. The title compound reveals electrical properties of an insulator. On expanding its molecular scaffold towards partially fluorinated [n]phenylenes (n≥2), the properties presumably can be transformed into those of semiconductors. In this context, the title compound is suggested as a prototype scaffold for ambipolar materials for organic electronics and spintronics.

RESUMEN

A number of new biologically interesting fluorinated 2-arylchroman-4-ones and their 3-arylidene derivatives were synthesized based on the p-toluenesulfonic acid-catalyzed one-pot reaction of 2-hydroxyacetophenones with benzaldehydes. It was found that obtained (E)-3-arylidene-2-aryl-chroman-4-ones reacted with malononitrile under base conditions to form 4,5-diaryl-4H,5H-pyrano[3,2-c]chromenes. The structures of the synthesized fluorinated compounds were confirmed by 1H, 19F, and 13C NMR spectral data, and for some representatives of heterocycles also using NOESY spectra and X-ray diffraction analysis. A large series of obtained flavanone derivatives as well as products of their modification (35 examples) containing from 1 to 12 fluorine atoms in the structure was tested in vitro for cytotoxicity in MDCK cell line and for antiviral activity against influenza A virus. Among the studied heterocycles 6,8-difluoro-2-(4-(trifluoromethyl)phenyl)chroman-4-one (IC50 = 6 µM, SI = 150) exhibited the greatest activity against influenza A/Puerto Rico/8/34 (H1N1) virus. Moreover, this compound appeared active against phylogenetically distinct influenza viruses, A(H5N2) and influenza B (SI's of 53 and 42, correspondingly). The data obtained suggest that the fluorinated derivatives of 2-arylchroman-4-ones are prospective scaffolds for further development of potent anti-influenza antivirals.

RESUMEN

A simple and highly effective methodology for the cross-coupling of heteroaryl iodides with NN-AuPPh3 at room temperature is reported. The protocol is based on a novel catalytic system consisting of Pd2(dba)3·CHCl3 and the phosphine ligand MeCgPPh having an adamantane-like framework. The present protocol was found to be well compatible with various heteroaryl iodides, thus opening new horizons in directed synthesis of functionalized nitronyl nitroxides and high-spin molecules.

RESUMEN

We report here an unprecedentedly fast and reversible transformation between 1D and 2D MOFs/CPs induced through organic solvent vapours. The transformations occur at room temperature in just 15-20 min, accompanied by a significant change in the observed phosphorescence. These findings provide a new insight into the design of luminescent networks with stimuli-switchable dimensionality.

RESUMEN

We have discovered that three molecules of arylacetylene are rapidly (15 min) assembled with one molecule of nitrile at room temperature in the KOBut/DMSO system to afford 2-aryl-3-arylethynyl-4-aryl-5-benzyl-1H-pyrroles in up to 76% yield. We assume that this unprecedented self-organization process involves the cascade addition of acetylenic carbanions, first to the CN, then to the CC and CC bonds of the intermediates, followed by pyrrole ring closure via the intramolecular nucleophilic addition of the NH functional group to the CC bond of the final intermediates.

RESUMEN

Introduction of Cl and O atoms into C4-vinyl carbocations was studied by X-ray diffraction analysis and IR spectroscopy. Chlorine atoms are weak electron acceptors in ordinary molecules but, within vinyl carbocations, manifest themselves as strong electron donors that accept a positive charge. The attachment of a Cl atom directly to a C=C bond leads to an increase in the e-density on it, exceeding that of the common double bond. The positive charge should be concentrated on the Cl atom, and weak δ- may appear on the C=C bond. More distant attachment of the Cl atom, e.g., to a C atom adjacent to the C=C bond, has a weaker effect on it. If two Cl atoms are attached to the Cγ atom of the vinyl cation, as in Cl2CγCδHCαHCH3, then the cation switches to the allyl type with two practically equivalent and almost uncharged CγCδCα bonds. When such a strong nucleophile as the O atom is introduced into the carbocation, a protonated ester molecule with a C-O(H+)-C group and a C=C bond forms. Nonetheless, in the future, there is still a possibility of obtaining carbocations with a non-protonated C-O-C group.

Asunto(s)

RESUMEN

Over recent years, Mn(II)-organic materials showing circularly polarized luminescence (CPL) have attracted great interest because of their eco-friendliness, cheapness, and room temperature phosphorescence. Using the helicity design strategy, herein, chiral Mn(II)-organic helical polymers are constructed featuring long-lived circularly polarized phosphorescence with exceptionally high glum and ΦPL magnitudes of 0.021% and 89%, respectively, while remaining ultrarobust toward humidity, temperature, and X-rays. Equally important, it is disclosed for the first time that the magnetic field has a remarkably high negative effect on CPL for Mn(II) materials, suppressing the CPL signal by 4.2-times at B ⃗ $\vec{B}$  = 1.6 T. Using the designed materials, UV-pumped CPL light-emitting diodes are fabricated, demonstrating enhanced optical selectivity under right- and left-handed polarization conditions. On top of all this, the reported materials display bright triboluminescence and excellent X-ray scintillation activity with a perfectly linear X-ray dose rate response up to 174 µGyair  s-1 . Overall, these observations significantly contribute to the CPL phenomenon for multi-spin compounds and promote the design of highly efficient and stable Mn(II)-based CPL emitters.

RESUMEN

A series of complexes [Cu2X2(Pic3PO)2] (X = Cl, Br, I) based on tris(pyridin-2-ylmethyl)phosphine oxide (Pic3PO) has been synthesized. At 298 K, these compounds exhibit thermally activated delayed fluorescence (TADF) of 1(M+X)LCT type with λmax varying from 485 to 545 nm, and quantum efficiency up to 54%. In the TADF process, the halide effect appears as the emission intensification and bathochromic shift of λmax in the following order X = I < Br < Cl. Upon X-ray irradiation, the title compounds emit radioluminescence, the emission bands of which have the same shape as those at TADF, thereby meaning a similar radiative excited state. By contrast to TADF, the halide effect in the radioluminescence is reversed: its intensity grows in the order X = Cl < Br < I, since heavier atoms absorb X-rays more efficiently. These findings essentially contribute to our knowledge about the halide effect in the photo- and radioluminescent Cu(I) halide emitters.

Asunto(s)

RESUMEN

Exploiting 2-(alkylsulfonyl)pyridines as 1,3-N,S-ligands, herein we have constructed 1D CuI-based coordination polymers (CPs) bearing unprecedented (CuI)n chains and possessing remarkable photophysical properties. At room temperature, these CPs show efficient TADF, phosphorescence or dual emission in the deep-blue to red range with outstandingly short decay times of 0.4-2.0 µs and good quantum performance. Owing to great structural diversity, the CPs demonstrate a variety of emissive mechanisms, spanning from TADF of 1(M + X)LCT type to 3CC and 3(M + X)LCT phosphorescence. Moreover, the designed compounds emit strong X-ray radioluminescence with the quantum efficiency of up to an impressive 55% relative to all-inorganic BGO scintillators. The presented findings push the boundaries in designing TADF and triplet emitters with very short decay times.

RESUMEN

X-ray diffraction analysis and IR spectroscopy were used to study the products of the interaction of vinyl cations C3H5+ and C4H7+ (Cat+) (as salts of carborane anion CHB11Cl11-) with basic molecules of water, alcohols, and acetone that can crystallize from solutions in dichloromethane and C6HF5. Interaction with water, as content increased, proceeded via three-stages. (1) adduct Cat+·OH2 forms in which H2O binds (through the O atom) to the C=C+ bond of the cation with the same strength as seen in the binding to Na in Na(H2O)6+. (2) H+ is transferred from cation Cat+·OH2 to a water molecule forming H3O+ and alcohol molecules (L) having the CH=CHOH entity. The O- atom of alcohols is attached to the H atom of the C=C+-H moiety of Cat+ thereby forming a very strong asymmetric H-bond, (C=)C+-H⋅⋅⋅O. (3) Finally all vinyl cations are converted into alcohol molecule L and H3O+ cations, yielding proton disolvates L-H+-L with a symmetric very strong H-bond. When an acetone molecule (Ac) interacts with Cat+, H+ is transferred to Ac giving rise to a reactive carbene and proton disolvate Ac-H+-Ac. Thus, the alleged high reactivity of vinyl cations seems to be an exaggeration.

RESUMEN

We introduce here a new subclass of copper(I) hybrid emitters simultaneously containing [CuxIy]z- anions and Cu+ cations, separated in space by a Janus head ligand. When UV-irradiated at 298 K, these unique "Two-In-One" hybrids exhibit a short-lived green TADF with near-unity quantum yield and a strong solvatochromic effect. Moreover, they manifest a strong radioluminescence upon X-ray irradiation. These findings open up new possibilities for the design of highly performing TADF materials.

RESUMEN

2,1,3-Benzochalcogenadiazoles C6 R4 N2 E (E/R; E=S, Se, Te; R=H, F, Cl, Br, I) and C6 H2 R2 N2 E (E/R'; E=S, Se, Te; R=Br, I) are 10π-electron hetarenes. By CV/EPR measurements, DFT calculations, and QTAIM and ELI-D analyses, it is shown that their molecular electron affinities (EAs) increase with decreasing Allen electronegativities and electron affinities of the E and non-hydrogen R (except Cl) atoms. DFT calculations for E/R+e⋅- →[E/R]⋅- electron capture reveal negative ΔG values numerically increasing with increasing atomic numbers of the E and R atoms; positive ΔS has a minor influence. It is suggested that the EA increase is caused by more effective charge/spin delocalization in the radical anions of heavier derivatives due to contributions from diffuse (a real-space expanded) p-AOs of the heavier E and R atoms; and that this counterintuitive effect might be of the general character.

RESUMEN

Nitronyl nitroxides are functional building blocks in cutting-edge research fields, such as the design of molecular magnets, the development of redox and photoswitchable molecular systems and the creation of redox-active components for organic and hybrid batteries. The key importance of the nitronyl nitroxide function is to translate molecular-level-optimized structures into nano-scale devices and new technologies. In spite of great importance, efficient and versatile synthetic approaches to these compounds still represent a challenge. Particularly, methods for the direct introduction of a nitronyl nitroxide moiety into aromatic systems possess many limitations. Here, we report gold derivatives of nitronyl nitroxide that can enter Pd(0)-catalysed cross-coupling reactions with various aryl bromides, affording the corresponding functionalized nitronyl nitroxides. Based on the high thermal stability and enhanced reactivity in catalytic transformation, a new reagent is suggested for the synthesis of radical systems via a universal cross-coupling approach.

RESUMEN

The coordination behavior of tris(2-pyridyl)arsine (Py3As) has been studied for the first time on the example of the reactions with CuI, CuBr and AgClO4. When treated with CuI in CH2Cl2 medium, Py3As unexpectedly affords the scorpionate complex [Cu(Py3As)I]∙CH2Cl2 only, while this reaction in MeCN selectively leads to the dimer [Cu2(Py3As)2I2]. At the same time, the interaction of CuBr with Py3As exclusively gives the dimer [Cu2(Py3As)2Br2]. It is interesting to note that the scorpionate [Cu(Py3As)I]∙CH2Cl2, upon fuming with a MeCN vapor (r.t., 1 h), undergoes quantitative dimerization into the dimer [Cu2(Py3As)2I2]. The reaction of Py3As with AgClO4 produces complex [Ag@Ag4(Py3As)4](CIO4)5 featuring a Ag-centered Ag4 tetrahedral kernel. At ambient temperature, the obtained Cu(I) complexes exhibit an unusually short-lived photoluminescence, which can be tentatively assigned to the thermally activated delayed fluorescence of (M + X) LCT type (M = Cu, L = Py3As; X = halogen). For the title Ag(I) complexes, QTAIM calculations reveal the pronounced argentophilic interactions for all short Ag∙∙∙Ag contacts (3.209-3.313 Å).

RESUMEN

The butylene carbocation in its salts with anions CHB11F11 - and CHB11Cl11 - forms isomers CH2=C+-CH2-CH3 (I) and CH3-C+=CH-CH3 (II), which were characterized here by infrared (IR) spectroscopy and X-ray diffraction analysis. The strongest influence on the structure of the cations is exerted by geometric ordering of their anionic environment. In the crystalline phase, the cations uniformly interact with neighboring anions, and the C=C bond is located in the middle part of the cations forming a -CH=C+- moiety with the highest positive charge on it and the lowest νC=C frequency, at 1490 cm-1. In the amorphous phase with a disordered anionic environment of the cations, contact ion pairs Anion-···CH2=C+-CH2-CH3 form predominantly, with terminal localization of the C=C bond through which the contact occurs. The positive charge is slightly extinguished by the anion, and the C=C stretch frequency is higher by ∼100 cm-1. The replacement of the hydrogen atom in cations I/II by a Cl atom giving rise to cations CH2=C+-CHCl-CH3 and CH3-C+=CCl-CH3 means that the donation of electron density from the Cl atom quenches the positive charge on the C+=C bond more strongly, and the C=C stretch frequency increases so much that it even exceeds that of neutral alkene analogues by 35-65 cm-1. An explanation is given for the finding that upon stabilization of the vinyl cations by polyatomic substituents such as silylium (SiMe3) and t-Bu groups, the stretching C=C frequency approaches the triple-bond frequency. Namely, the scattering of a positive charge on these substituents enhances their donor properties so much that the electron density on the C=C bond with a weakened charge becomes much higher than that of neutral alkenes.