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New pyridyl-containing diarylamines were obtained via Cu-assisted reductive amination of the ortho-2-pyridylarylboronic acids. Comparative analysis of the spectral and electrochemical data obtained for new diarylamines and their pyridyl-free counterparts revealed the intramolecular H-bond (IMHB) formation which significantly influences the properties of the amino group. The electron density at the N atom of the amino group is increased due to partial weakening of the N–H bond, although the BDE and activation energy for the H-atom abstraction is increased due to the chelating effect of two N atoms. The ortho-pyridyl-containing diarylamines are more prone to be oxidized as compared to their pyridyl-free counterparts; the shift in the oxidation potential values correlates with the strength of the intramolecular H-bonding which can be tuned by inserting substituents in the pyridyl or phenyl rings. The IMHB is reserved even in polar solvents having a significant H-acceptor ability (such as DMSO) but can be destroyed in methanol, testifying in favor of the dynamic nature of the H-bonding.

The mini-review highlights key structural features and provides guidelines for the molecular design of ambipolar redox-active frameworks, which are of interest for the fabrication of all-organic ‘poleless’ batteries and semiconductors. Open-shell molecules that can form at least three relatively stable redox states (i.e. cationic, neutral, and anionic) are discussed. The efficiency of the suggested strategies is supported by the representative examples taken from the recent publications.

This mini-review highlights key structural features that should be taken into account when creating ambipolar redox-active closed-shell metal-free molecules. This type of compound is strongly required for the fabrication of all-organic ‘poleless’ batteries and semiconductors. The suggested strategies aimed at stabilization of both oxidized (cationic) and reduced (anionic) redox-states are based on the comprehensive analysis of the most successful structures taken from the recent publications.

The results of the DFT studies on the mechanism of the PIII/PV=O catalyzed reductive amination of nitrosoarenes using ArB(OH)2 yielding diaryl amines are reported. This allowed a comparison of the reaction paths and key intermediates of the Cu(I)- and P(III)-mediated reductive aminations of aryl boronic acids using alkylnitrites, nitroso- or nitroarenes, and revealed important similarities in the catalytic reactivity of transition-metal and main-group elements in C(sp2)–N bond-forming reactions. It is shown that both transformations occur via ambiphilic nitrenoid-type key intermediates, the reactivity of which towards the aryl boronic acid is attributed to the presence of both a Lewis acid center (Cu or P) and a Lewis base center (the N or O atoms of the ‘N=O’ component).

The α-methylcyclopropyl (MCP) group with conformationally dependent electronic properties is suggested as an additional structural "instrument" for stabilization of both open-shell and ionic states of diarylnitroxides, to be used as "ambipolar" redox active materials. New MCP-substituted diphenylnitroxides (fully characterized by electrochemical, spectral, and X-ray data) are the most stable nitroxides of the diaryl type known to date [τ1/2 in benzene exceeds three months (2310 h)]. The radicals are capable to reversible oxidation and reduction, yielding stable oxoammonium cations and aminoxyl anions. DFT investigation of the electronic structure and geometry of the compounds confirmed the conformational switching of the cyclopropyl orientation relative to the adjacent aromatic π system is dependent on the nitroxide's redox state. Additional through-space stabilizing interaction between the π-acceptor orbital of the NO+ moiety and the cyclopropyl "banana" bond orbital was also detected, highlighting its good hyperconjugative ability. The estimated σ(para)MCP value (-0.32) confirms its strong electron-donating properties.

Involvement of an α,α-cyclopropanated amino acid in the chiral Ni(II) coordination environment in the form of a Schiff-base is considered as a route to electrochemical broadening of the DA-cyclopropane concept in combination with chirality induction in the targeted products. A tendency to the reductive ring-opening and the follow-up reaction paths of thus formed radical-anions influenced by substituents in the cyclopropane ring are discussed. Optimization of the reaction conditions opens a route to the non-proteinogenic amino acid derivatives containing the α-β or β-γ double C=C bond in the side chain; the regioselectivity can be tuned by Lewis acids addition. One-pot combination of the reductive ring opening and subsequent addition of thiols allows obtaining the cysteine derivatives in practical yields and with high stereoselectivity at the removed β-stereocenter.

Experimental and DFT investigation of the α,α-cyclopropanation of amino acids via nucleophilic addition of the deprotonated glycine Ni(ii)-Schiff-base complex, containing the (S)-proline derivatives as an auxiliary chiral moiety, to alkyl α-bromoacrylates was performed. It was demonstrated that the predominant configuration of the newly formed α-stereocenter is (S), regardless of the solvent used but the smart choice of solvent allows high diastereoselectivity at the removed β-stereocenter to be obtained, which commonly is rather rare. DFT analysis of the reaction path provides a rationale for the stereochemical outcome observed. The cyclopropanated complexes exhibit stereodependent redox activity, thus supporting that this is a general phenomenon inherent to this class of Ni Schiff-base derivatives, accounting for the influence of the peripheral groups in the metal coordination environment on the relative impact of different parts of the molecule in the frontier orbitals via conformational changes.

Copper-catalyzed amination of aryl boronic acids with alkylnitrites leading to symmetrical diarylamines with a practical 50–80% yield was elaborated. Two C(sp2)–N bonds are formed in the one-pot pr...

Photochemical stability and possible routes for photodegradation of twisted diarylnitroxides were determined. It was shown that quantum yields for twisted diarylnitroxides fall in the range typical for the best representatives of alkylnitroxides providing an additional support that twisting of the phenyl ring from the N-O conjugation plane constitutes an efficient route for increasing thermo and photo stability of the nitroxides.

A composite material in the form of powder is synthesized by a redox reaction in mixed aqueous solution of Pd(NH3)4Cl2 + pyrrole. The composite consists of polypyrrole globules with palladium nanoparticles uniformly distributed inside the latter. Being applied as a film on the electrode surface, both components of this material exhibit redox activity. Palladium particles inside the composite exhibit catalytic properties in cyanation of styryl bromides, a reaction widely used in fine organic synthesis.

One-pot method for direct stereoselective (S)-α-thioalkylation of glycine in Ni(II) coordination environment was elaborated. The reaction of electrochemically deprotonated Ni(II) glycine/Schiff-base complex containing (S)-o-[N-(N′-benzylprolyl)amino]benzophenone as an auxiliary chiral moiety with alkyl thiocyanates leads to the α-thioalkylated derivatives in a practical ca.70% chemical yield and stereoselectivity (de 80%).

The electrochemical behavior of a new type of stable diarylnitroxide radicals with bulky substituent in the ortho-position of one of the phenyl rings is described. The presence of the substituent results in broken conjugation of one of the phenyl rings with the NO moiety (the other ring stays conjugated) giving rise to so called “twisted nitroxides”. New diphenylnitroxides with t-Bu and/or CF3 substituents were synthesized and are the first examples of diarylnitroxides which are extremely stable in solution and form both stable oxidized and reduced forms (oxoammonium cations and aminoxyl anions). These compounds exhibit fast ET kinetics and reversible electrochemical oxidation and reduction. Varying the torsion angle θ shifts Eox and Ered values in the opposite directions thus increasing the electrochemical potential gap, contrary to the traditional effects of substituents that commonly shift both potential values in the same direction. The electronic effect of the substituents in the ortho-position as well as the total electronic effect of both rings on the electrochemical potential values was estimated using the linear fit for the relationship between E 1 / 2 Ox + E 1 / 2 Red vs. the sum of Hammett constants (σp + σo·cosθ). The ρ value (the slope in the linear fit) is 0.501 indicating significant sensitivity of the potential values to the electronic effects and wide possibilities for tuning. The results obtained shed light on the efficient principles of molecular design for stable electroactive nitroxide-based materials.

Crystals of binuclear complex [(VO) 2 ( µ -OH)( µ -Piv) 2 (bpy) 2 ](OTf) ( 1 ) have been obtained by the reaction of [VO(H 2 O) 5 ](OTf) 2 (OTf = CF 3 SO 3 − , Piv = (CH 3 ) 3 CCO 2 − ) with 2,2′-bipyridine (bpy) and lithium trimethylacetate (pivalate), Li(Piv), in a ratio of 1:1:2 in MeCN. Change of the reagent ratio to 1:1:3 resulted in the bimetallic compound [Li 2 (VO) 2 ( µ -Piv) 6 (bpy) 2 ] ( 2 ), which was isolated in the form of 2 ·MeCN and 2 ·CH 2 Cl 2 solvates. Replacement of Li(Piv) with lithium trifluoroacetate Li(Tfac) (Tfac = CF 3 CO 2 − ) results in the bimetallic compound [Li 2 (VO) 2 ( µ -Tfac) 6 (bpy) 2 ] ( 3 ). A similar reaction with lithium trichloroacetate, Li(Tcac) (Tcac = CCl 3 CO 2 − ), in ethanol gives the mononuclear complex [VO(Tcac)(bpy) 2 ](OTf) ( 4 ). The structures of 1 – 4 were determined by single crystal X-ray diffraction. The magnetic properties (2–300 K) and EPR spectra of compounds 1 – 3 have been studied. Using the ESEEM (electron spin echo envelope modulation) method it has been shown that the mononuclear cation [VO(Tcac)(bpy) 2 ] + of complex 4 has partial spin density transfer from the V IV atom to donor ligands (in particular, the bpy nitrogen atoms). According to EPR spectroscopy data and quantum-chemical calculations, a similar spin density distribution is observed for 2 and 3 , though spin exchange in these compounds is hindered by lithium ions, which contain no spin density and block electron density delocalization in the bridging system between the “magnetic” vanadium ions. Electrochemical properties of compounds 2 and 3 confirm the vanadium(IV) oxidation state.

A new series of promising synthetically facile cycloruthenated thiophene-based sensitizers have been developed and fully characterized by UV–vis spectroscopy, NMR and cyclic voltammetric studies. The synthesized dyes have broad MLCT bands spanning the visible spectrum, with high extinction coefficients. The energies of the molecular orbitals for the isolated molecules of the complexes and densities of occupied states were determined. The cycloruthenated compounds contains ortho-metallated thiophene moiety substituted by N-(methyliden)aniline or pyridine-2-yl at the ortho-position. Having 4,4’-dicarboxy-2,2’-bipyridine as the linker and auxiliary ligands and anchored to nanocrystalline TiO2 films, they achieve efficient sensitization in the visible range and display an overall conversion efficiency of 5.3% under standard AM 1.5 sunlight.

A series of novel highly soluble double-caged [60]fullerene derivatives were prepared by means of lithium-salt-assisted [2+3] cycloaddition. The bispheric molecules feature rigid linking of the fullerene spheres through a four-membered cycle and a pyrrolizidine bridge with an ester function CO2 R (R=n-decyl, n-octadecyl, benzyl, and n-butyl; compounds 1 a-d, respectively), as demonstrated by NMR spectroscopy and X-ray diffraction. Cyclic voltammetry studies revealed three closely overlapping pairs of reversible peaks owing to consecutive one-electron reductions of fullerene cages, as well as an irreversible oxidation peak attributed to abstraction of an electron from the nitrogen lone-electron pair. Owing to charge delocalization over both carbon cages, compounds 1 a-d are characterized by upshifted energies of frontier molecular orbitals, a narrowed bandgap, and reduced electron-transfer reorganization energy relative to pristine C60 . Neat thin films of the n-decyl compound 1 a demonstrated electron mobility of (1.3±0.4)×10-3 cm2 V-1 s-1 , which was comparable to phenyl-C61 -butyric acid methyl ester (PCBM) and thus potentially advantageous for organic solar cells (OSC). Application of 1 in OSC allowed a twofold increase in the power conversion efficiencies of as-cast poly(3-hexylthiophene-2,5-diyl) (P3HT)/1 devices relative to the as-cast P3HT/PCBM ones. This is attributed to the good solubility of 1 and their enhanced charge-transport properties - both intramolecular, owing to tightly linked fullerene cages, and intermolecular, owing to the large number of close contacts between the neighboring double-caged molecules. Test P3HT/1 OSCs demonstrated power-conversion efficiencies up to 2.6 % (1 a). Surprisingly low optimal content of double-caged fullerene acceptor 1 in the photoactive layer (≈30 wt %) favored better light harvesting and carrier transport owing to the greater content of P3HT and its higher degree of crystallinity.

Based on a combination of a gas-phase DFT electronic structure calculation at PBE/L2 level implemented in the highly efficient ‘Priroda’ program package with consecutive fast solvation energy evaluation by continuum solvation model, a liable methodology has been developed for accurate calculation of the standard redox potentials for diarylnitroxides in acetonitrile solution.

Possibility for diarylamine/diarylnitroxide cycling via electrochemical N–O bond formation/bond breaking processes was considered using quantum-chemical and electrochemical methods. It was shown that electrochemically reduced diarylnitroxides undergo fast N–O bond cleavage in the presence of oxophilic Li ions. The possible reaction scheme was suggested. In contrast, in the presence of Na+ salts, aminoxyl anions are stable and can be considered as possible anodic redox active material in energy storage systems utilizing Na+ ions migration. Direct oxygenation of diarylaminyl radicals with dioxygen yielding diarylnitroxide is not feasible; multiple competing routes involving the aromatic moiety are observed instead. The results obtained shed light on possibilities and limitations for functioning of nitroxide-based redox active electrode materials., Electrochemistry; Organic chemistry; Theoretical Chemistry; electrochemical bond cleavage; diaryl nitroxides; redox materials; electrode reactions; specific solvation

Electrochemical properties of a series of chiral Ni(II) Schiff-base complexes of β-arylsulfanyl amino acids were investigated; the potential values and possible follow-up steps were compared for the diastereomeric couples. Within the series, two diastereomeric couples ((D)- and (L)-1H as well as (D)- and (L)-2H) were identified which constitute an interesting example of the stereodependent reactivity induced by electrochemical oxidation: follow-up transformations of the radical-cations are different for the (L)- and (D)-diastereomers. Reversibility of electrochemical reduction of the complexes allows comparison of the reduction potential values for the diastereomeric couples. DFT computation of the conformations of (D)- and (L)- diastereomers as well as non-covalent interactions in the Ni coordination environment indicates that small differences observed in the reduction potential values are more likely attributed to solvation rather than stereoelectronic effects induced by inversion of the α-amino acid stereocenter.

Stereoselective electrosynthesis of the first individual (f,tA)- and (f,tC)-1,4-fullerene derivatives with a non-inherently chiral functionalization pattern is described, as well as the first example of an optically pure protected primary amino acid directly linked to the fullerene through only the chiral α-amino-acid carbon atom. An application of an auxiliary chiral nickel-Schiff base moiety as derivatizing agent allowed separation of (f,tA)- and (f,tC)-1,4-fullerene derivatives using an achiral stationary phase, a separation which has never been done before.

Incorporation of the CF 2 bridge into fullerene cages allows fine tuning of the boundary levels and endows bridgehead sites with enhanced reactivity in the anionic state. Further functionalization at those sites provides additional level tuning capabilities, which can give rise to promising acceptor-type building blocks for organic electronics. Here we report the regioselective synthesis, spectral and structural characterization of novel C 60 (CF 2 )R 2 dialkyl derivatives (R = CH 3 , allyl, benzyl, CH 2 C 6 F 5 , CH 2 CO 2 Et), as well as their electrochemical behavior. The reported compounds can be reversibly reduced up to the trianionic state. Experimental electrochemical and DFT estimation of the HOMO and LUMO levels revealed that the energy of the frontier orbitals is increased as compared to C 60 making these compounds prospective for application as acceptor materials in polymer solar cells (PSCs). Testing the corresponding prototypical PSCs demonstrated that among the C 60 (CF 2 )R 2 derivatives the highest power conversion efficiency was observed for C 60 (CF 2 )(CH 2 CO 2 Et) 2 which exhibits better solubility and photoactive layer morphology.

The mesoporous nanographite (NG) film material consisting of tiny flake-like graphite crystallites of nanometer-scale thickness is deposited onto carbon fibers with diameter of few micrometers using adapted plasma enhanced chemical vapor deposition (CVD) method. Macroscopic morphology parameters of NG material depend on deposition time duration so, that thickness of the NG coating is increased from 0.5 to 2 μm, whereas the average sizes of the individual crystallites and the pores between them are decreased from 0.5 to 0.1 nm, with deposition time extension from 15 to 60 min, respectively. The high resolution electron microscopy examinations indicate that the NG flakes consist of parallel graphene layers separated by about 0.34 nm and those layers are paired at the edges of the flakes producing arced structures. The electrochemical capacitance measurements were served for characterization of the mesoporous nanographite coating; the specific capacitance arising from the electrostatic charge accumulated at the electrode–electrolyte interface was estimated using cyclic voltammetry, galvanostatic charge/discharge measurements, and electrical impedance spectroscopy. The effects of the deposition time duration and other parameters of CVD process on electrochemical performance and structural properties of the prepared NG films are to be discussed.

The metal complexes of a pivotal representative of the so-called porphyrin-phthalocyanine hybrid series - 5,15-diaryl-10,20-diazatetrabenzoporphyrin (Ar2TBDAP), - recently made available by a new selective and versatile procedure, with Zn, Ni, Cu, and Pd were synthesized and characterized by single crystal X-ray analysis, UV-vis/NIR absorption and emission spectroscopy, nanosecond and microsecond time-resolved (NSTA and TCSPC) experiments and by means of cyclic voltammetry. The complexes obtained are compared with the related tetrabenzo-annelated tetrapyrrolic systems, including tetrabenzoporphyrin, phthalocyanine, and other hybrids, using both experimental data and the results of quantum chemical DFT and TD-DFT computations. The Ar2TBDAP system reported shares sharp hyperchromic long-wavelength absorption of phthalocyanines with the essential features of extended porphyrins including the possibilities of effective chemical modification through meso-aryl substituents.

International audience; An efficient cyanation of vinyl bromides, activated chlorides and mesylates with K4Fe(CN)(6) has been performed using palladium polypyrrole nanocomposite. The reactions are clean and high yielding. They are highly stereoselective furnishing (E)-nitriles from (E)-halides and Z-nitriles from Z-halides. Chemoselective cyanation of sp(2)(vinyl)-Br bond in the presence of sp(2)(aryl)-Br is possible. The additional advantages offered by the suggested catalytic system are operational simplicity and the environmentally friendly synthetic methodology (no toxic ligands and the possibility to use environmentally benign aqueous solutions). The catalyst is active under heating and under MW irradiation; it can be reused at least three times.

Despite trifluoromethylfullerene Cs-C70(CF3)8 has a multitude of available reaction sites, [2 + 1] cycloaddition of CX2 moieties (X = F and p-MeOC6H4) proceeds regioselectively at a particular [5,6]-bond. Depending on the nature of X, the resulting derivative can be either [5,6]-open (i.e., the said C C bond is cleaved) or [5,6]-closed, and this structural detail, seemingly insignificant for a molecule that large, brings about a remarkable 0.6 eV difference in the electron affinity, as revealed by electrochemical studies. Synthesis, structural and electrochemical elucidation of the C70(CF3)8(CX2) compounds are discussed, as well as electrochemically promoted switching of the electronic properties based on disruption of the conjugated 62π-electron system into the isolated 32 and 28π-electron fragments upon closing the [5,6]-bond.

A voltammetric investigation of the electrochemical reduction and oxidation of a homologous series of binuclear diastereomeric (SR)- and (SS)-Ni(II) α-amino acid /Schiff-base complexes in which two Ni-containing moieties are linked via glycine fragments (LNi–Gly–(CH2)n–Gly–NiL; n = 0,1,2) and which contain an auxiliary chiral aromatic moiety – (S)-o-[N-(N'-benzylprolyl) amino]benzophenone was performed at a Pt electrode in acetonitrile. These complexes constitute an interesting example of the influence of the absolute configuration of the stereocenters on the electrochemical behavior of the diastereomers and on the redox potential values. To distinguish between the diastereomers, cyclic voltammetry is more sensitive than UV–vis spectroscopy. For n = 0, the difference between the λmax values for the (SR) and the (SS) diastereomers is large enough to differentiate them. With an increase in the number of the methylene units between two Ni–glycine moieties in the binuclear complex spectral characteristics for (SR) and (SS) diastereomers become almost identical whereas the voltammetric characteristics remain sufficiently different to allow the differentiation even for n = 2. 1H, 13C NMR data and DFT computation revealed that the electronic density in (SR)- LNi–Gly–(CH2)n–Gly–NiL (n = 0,1,2) is distributed non-uniformly between the two parts of the diastereomeric molecule both in the neutral complexes and their radical cation. Their dipole moment as well as their frontier orbitals were calculated. The HOMO and LUMO are not located on the same mononuclear units and their location alternates between the two units in the homologous series. Thus, there is an alternation of the reduction and oxidation sites. As a consequence, both the oxidation and the reduction of the (SR)-complexes are easier than those of to their (SS) counterparts, which results in a smaller difference between the oxidation and the reduction potentials for the SR diastereomers. This provides an electrochemical way to probe the absolute configuration of the α-carbon atoms of the diaminodicarboxylic acid moiety in these Ni(II) binuclear complexes.

The redox properties of the first member of a new family of bridgehead-modified difluoromethylenated homofullerenes, [6,6]-open C 60 (CF 2 )H 2 , were investigated by means of cyclic voltammetry and ESR spectroelectrochemistry. The half-life time of C 60 (CF 2 )H 2 –• estimated from the decay of the ESR response exceeds 25.5 min at room temperature which will be crucial for practical applications later on. The high stability of C 60 (CF 2 )H 2 –• was proven to be attributed to spin density delocalization over the fullerene cage as well as to the higher BDE(C–H) value for C 60 (CF 2 )H 2 (as compared to C 60 H 2 ). Di- and trianions of C 60 (CF 2 )H 2 are less stable and undergo partial dehydrogenation. A detailed voltammetric investigation of H-transfer processes (induced by radicals, radical-anion species or by a Bronsted bases) in the anionic forms of C 60 (CF 2 )H m ( m = 0–2) was performed. It allowed suggesting a general scheme integrating various anionic forms of C 60 (CF 2 )H m n – ( n = 1–3) which was corroborated by DFT calculations as well as by a targeted synthesis of deprotonated C 60 (CF 2 )H – and C 60 (CF 2 ) 2– anions from C 60 (CF 2 )H 2 using a Bronsted base. Based on these results, an alternative, non-electrochemical synthetic route to C 60 (CF 2 )H 2 using the Zn/Cu-couple in water/toluene media was elaborated since similar processes regulate the features of hydrogenation of fullerene derivatives in both cases.

Two series of germanium compounds, (p-Tol)3Ge-MMe3 (M = Si (1), Ge (2), Sn (3)) and (Me3Si)3Ge-MPh3 (M = Ge (4), Sn (5)), were prepared using lithium or potassium intermediates. The changing of the reaction conditions results in trigermane Ph3Ge-Ge(SiMe3)2-GePh3 (6). The molecular structures of 1, 2, and 6 were investigated by X-ray analysis. By UV/visible spectroscopy it is established that introduction of a tin atom results in a significant bathochromic absorption shift. Furthermore, according to cyclic voltammetry, oxidation potentials decrease in the order 1 > 2 > 3. The electronic structures of 1–4 and related (Me3Si)3Ge-SiPh3 were investigated by DFT calculations. Fluorescence properties of 1–3 were studied in the solid state and in solution; for compound 3 phosphorescence (lifetime is 4.58 ms) is observed in the solid state.

The title compound, first example of a stable diarylnitroxyl with vacant para-position, was best synthesized by CuCl-assisted coupling of o-tert-butylnitrosobenzene and p-tert-butylphenylboronic acid followed by N-xidation of the thus obtained unsymmetrical diarylamine. ESR investigation showed that ortho-substituted aromatic ring is removed from the conjugation plane providing unusual stability of this radical.

Bis{tetrakis(5,7-bis(4-tert-butylphenyl)-6H-1,4-diazepino)[2,3-b,g,l,q]porphyrazinato} cerium has been prepared for the first time via two alternative synthetic pathways: template macrocyclization of 5,7-bis(4-tert-butylphenyl)-6H-1,4-diazepine-2,3-dicarbonitrile and direct complexation employing its cyclic tetramer, a free-base porphyrazine ligand. A combination of HRMS, UV-Vis, FT-IR and NMR spectroscopic methods allowed the identification of the tetravalent oxidation state of cerium ion in the double-decker obtained. Unlike Pc2CeIV (Pc2− = phthalocyaninate anion), the compound revealed a complicated UV-Vis spectrum that demonstrated a strong solvent dependence. A comparative electrochemical study of the cerium complex and the corresponding free-base ligand was carried out. Ligand-centered processes are diffusion controlled, whereas Ce4+/3+ transformation is characterized by slow electron transfer kinetics. This is as a result of poor accessibility of the metal center to an electrode surface due to the presence of bulky ligands, as well as a considerable structural rearrangement of the sandwich molecule.

Comparative investigation of copper-assisted oxidative and reductive amination showed that the latter was preferable for the synthesis of bulky diarylamines. DFT estimation of the mechanism of copper(I)-assisted reductive amination of boronic acids with aryl nitroso compounds was performed and possible active species were identified. DFT estimation of the steric penalty revealed that the barrier for the transmetalation step for the hindered nitroso compound was almost the same as that for the unsubstituted one, whereas a bulky group in the boronic acid increased the activation energy. A DFT study of the influence of the electronic properties of the substituents in both reactants on the activation energy revealed that the optimal combination for the synthesis of unsymmetrical diarylamines to provide better yields was an electron-rich aryl boronic acid and an electron-deficient nitroso compound. By using these helpful guidelines, a series of new bulky diarylamines were obtained and fully characterized.

The reaction of an oxidovanadium(IV) salt with an N-donor ligand (2,2′-bipyridine (bpy) or 4,4′-di-tert-butyl-2,2′-bipyridine (dtb-bpy)) and M(piv) (M = Li, K, NBu4; piv = (CH3)3CCO2−) in a ratio of 1:1:2 affords complexes [(VO)2(µ-OH)(µ-piv)2(bpy)2](otf) (1), [(VO)2(µ-O)(µ-piv)2(dtb-bpy)2](otf)·H2O (2), or [(VO)2(µ-O)(µ-piv)2(bpy)2](NO3)·Hpiv·H2O (3), respectively (piv = (CH3)3CCO2−, otf = CF3SO3−). According to single-crystal X-ray diffraction, the complexes contain two vanadium atoms bridged by two carboxylate groups and one hydroxo (1) or oxo (2, 3) group. Cyclic voltammetry revealed that both vanadium atoms in 1 have oxidation state +4, whereas one of the two metal atoms in 2 and 3 has oxidation state +4 and another one has +5. The room-temperature EPR spectrum of complex 2 in solution is indicative of delocalization of an unpaired electron between two equivalent metal atoms. In frozen glass (77 K) the electron is localized on one center.