The metalation of 3,6-di- tert -butyl-1,8-bis-(2,4,6-triisopropylphenyl)-9 H -carbazole ( 1 ) with n -BuLi, t -BuLi or Me 3 SiCH 2 Li (1 : 2) in heptane affords binuclear ionic complexes containing monomeric n -BuLi, t -BuLi and Me 3 SiCH 2 Li units.

A new redox-active tetradentate ONNO-type ligand containing electron-withdrawing chlorine substituents in the phenylene ring, namely N,N'-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-4,5-dichloro-1,2-phenylenediamine (LH4), has been synthesized. Its coordination behavior was studied with tin(IV), zinc(II), and cadmium(II) ions. The reaction with Sn(IV) precursor yields the complex LSnMe2 (1), where the ligand is fully deprotonated and coordinated in its dianionic form. However, in solution, L undergoes intramolecular cyclization within the metal coordination sphere, resulting in the formation of a phenoxazine moiety and, consequently, a new ligand L' in the isolated complex L'SnMe2 (2). For Zn(II) and Cd(II), the structures of the resulting compounds - (LH)2Zn (3), (LH)2Cd (4), L'2Zn (5), and L'2Cd (6) - are determined by the choice of oxidant (p-benzoquinone or atmospheric oxygen) used during the synthesis. The structures of the synthesized complexes were established using a combination of NMR, IR, and UV spectroscopy, along with elemental analysis. SC-XRD was carried out for the tin(IV) and zinc(II) compounds. It was shown that the obtained derivatives possess redox-amphoteric properties and exhibit intense absorption in the near-IR region.

Here, we report the synthesis of tris(benzhydryl) sodium calciate {[(p-tBu-C6H4)2CH]3Ca}Na (3) featuring the structure of a base-free contact ion pair. Catalytic amounts (2 mol%) of 3 containing earth-abundant and biogenic s-metals combined with pyrrolidine as a co-catalyst (H+-donor) enable efficient regio- and stereocontrollable CC bond transposition at ambient temperature. Allyl- and homoallylbenzenes undergo thermodynamically controlled isomerization to afford prop-1-en-1-yl- and but-1-en-1-ylbenzenes with E-stereoselectivity up to 98%. The exceptionally regioselective isomerization of terminal alpha-olefins (1-hexene-1-decene) to internal 2-olefins catalyzed by 3/pyrrolidine (23 degrees C) to yield a mixture of E- and Z-isomers proved to be kinetically controlled. Mechanistic investigations revealed that these processes involve the in situ formation of a heterobimetallic amide complex, which catalyzes olefin isomerization through methylene group deprotonation followed by metallotropic rearrangement. DFT calculations elucidate the mechanism of the catalytic cycle and explain E/Z-selectivity in terms of kinetic and thermodynamic controls. In particular, QTAIM analysis revealed coordination of allylic intermediates to both metallic centers and therefore defined a synergetic effect of the heterobimetallic catalyst.

A study of nucleophilic substitution in 4,7-dichloro[1,2,5]oxadiazolo[3,4-d]pyridazine 1-oxide 4 showed that the nature of the nucleophile has a significant effect on the position and number of substituted chlorine atoms. Treatment of the dichloride 4 with amines resulted in the selective substitution of the chlorine atom at position 4 or of two chlorine atoms, depending on the amount of amine used. The reaction with thiols does not stop at the formation of a mono-substitution product and leads to bis-substitution products regardless of the structure of the thiol, its amount and reaction conditions. The reaction of 4 with alcohols and sodium alcoholates is not regioselective and afforded a mixture of mono-substitution products at positions 4 and 7, while hydrolysis of 4 gave 4-chloro-7-oxo-6,7-dihydro-[1,2,5]oxadiazolo[3,4-d]pyridazine 1-oxide only. The results of DFT calculations of the first and second stages of SNAr substitution reactions showed that the reactivity of the chlorine atoms in positions 4 and 7 does not differ significantly, and the reason for the differences in reactivity is the presence of kinetic control for N-nucleophiles, thermodynamic control for reactions with O-nucleophiles, and muted effects for S-nucleophiles. The position of the oxygen atom of the N-oxide in furoxanopyridazines was rigorously proven by X-ray structural analysis data.

A new redox-active tetradentate ONNO-type ligand containing electron-withdrawing chlorine substituents in the phenylene ring, namely N,N'-bis(3,5-di‑tert‑butyl‑2-hydroxyphenyl)-4,5-dichloro-1,2-phenylenediamine (LH4), has been synthesized. Its coordination behavior was studied with tin(IV), zinc(II), and cadmium(II) ions. The reaction with Sn(IV) precursor yields the complex LSnMe2 (1), where the ligand is fully deprotonated and coordinated in its dianionic form. However, in solution, L undergoes intramolecular cyclization within the metal coordination sphere, resulting in the formation of a phenoxazine moiety and, consequently, a new ligand L' in the isolated complex L'SnMe2 (2). For Zn(II) and Cd(II), the structures of the resulting compounds — (LH)2Zn (3), (LH)2Cd (4), L'2Zn (5), and L'2Cd (6) — are determined by the choice of oxidant (p-benzoquinone or atmospheric oxygen) used during the synthesis. The structures of the synthesized complexes were established using a combination of NMR, IR, and UV spectroscopy, along with elemental analysis. SC-XRD was carried out for the tin(IV) and zinc(II) compounds. It was shown that the obtained derivatives possess redox-amphoteric properties and exhibit intense absorption in the near-IR region.

New binuclear rare-Earth complexes [(μ2-η5:η5;κ2:κ2-N,C-L)Ln2(THF)4] (Ln = Y3+ (1Y), Tb3+ (1Tb), Dy3+ (1Dy), and Er3+ (1Er)) containing a hexaanionic dibenzopentalene-bridged bis(carbazolyl) framework were obtained via spontaneous self-assembly in the reactions of Ln(CH2SiMe3)3(THF)2 with an equimolar amount of 3,6-di-tert-butyl-1,8-bis(phenylethynyl)-9H-carbazole. Two Ln3+ ions are μ-anti-η5:η5-coordinated with the dianionic dibenzopentalene fragment resulting from a series of successive intramolecular ortho-CH activations in the phenyl rings of the ethynyl substituents followed by intermolecular dimerization involving Ln-CAr bond addition to a CC triple bond. Magnetic investigations show that 1Dy behaves as a genuine single-molecule magnet (SMM) with relaxation dynamics described by a multicomponent phenomenological relaxation model yielding an effective energy barrier of 689 cm-1. In contrast, 1Tb and 1Er exhibit only field-induced slow magnetic relaxation at low temperature. Ab initio calculations reveal a substantially larger crystal-field splitting and stronger axial anisotropy for Dy3+ than for the Er3+ analogue. Weak antiferromagnetic interactions between the lanthanide centers were identified with J = -0.23 cm-1 for 1Dy, -0.06 cm-1 for 1Tb, and -0.28 cm-1 for 1Er. This indicates that the slow magnetic relaxation is governed primarily by single-ion crystal-field effects rather than exchange coupling.

Here, we report the synthesis of tris(benzhydryl) sodium calciate {[(p-tBu-C6H4)2CH]3Ca}Na (3) featuring the structure of a base-free contact ion pair. Catalytic amounts (2 mol%) of 3 containing earth-abundant and biogenic s-metals combined with pyrrolidine as a co-catalyst (H+-donor) enable efficient regio- and stereocontrollable C[double bond, length as m-dash]C bond transposition at ambient temperature. Allyl- and homoallylbenzenes undergo thermodynamically controlled isomerization to afford prop-1-en-1-yl- and but-1-en-1-ylbenzenes with E-stereoselectivity up to 98%. The exceptionally regioselective isomerization of terminal α-olefins (1-hexene-1-decene) to internal 2-olefins catalyzed by 3/pyrrolidine (23 °C) to yield a mixture of E- and Z-isomers proved to be kinetically controlled. Mechanistic investigations revealed that these processes involve the in situ formation of a heterobimetallic amide complex, which catalyzes olefin isomerization through methylene group deprotonation followed by metallotropic rearrangement. DFT calculations elucidate the mechanism of the catalytic cycle and explain E/Z-selectivity in terms of kinetic and thermodynamic controls. In particular, QTAIM analysis revealed coordination of allylic intermediates to both metallic centers and therefore defined a synergetic effect of the heterobimetallic catalyst.

The lithiation reactions of superbulky 3,6-di-tert-butyl-1,8-bis-(2,4,6-triisopropylphenyl)-9H-carbazole (1) with a two-fold molar excess of n-BuLi, t-BuLi, or Me3SiCH2Li in heptane afford the binuclear lithium complexes [Carb2,4,6-iPrLi(μ2-n-Bu)Li] (2), [Carb2,4,6-iPrLi(μ2-Me3SiCH2)Li] (3), and [Carb2,4,6-iPrLi(μ2-t-Bu)Li] (4) in 80, 90, and 56% yields. The single-crystal X-ray diffraction studies revealed that 2-4 are binuclear ionic complexes comprising the alkyl group μ2-bridging two lithium centers, one of which is also η6-coordinated with the phenyl fragment of the carbazolyl ligand. For complexes 2 and 3, the binuclear structures are retained in solution as evidenced by 1H, 13C, 7Li, and 1H DOSY NMR spectroscopy. QTAIM and NCI data reveal a difference in the strength of Li-C interactions between 2-4, which are weaker for 4, and rationalised the tBu-substituted 4 prone to dissociation.

Novel antimony( v ) complexes featuring ONNO redox-active ligands exhibit strong NIR absorption, photothermal activity, and high optical stability.

The study investigates the kinetics and thermodynamics of the reversible tandem Diels-Alder (tDA) reaction between difuranic compounds and maleimides, leading to the quantitative formation of tDA adducts at rates comparable to their counterparts from the “classical” Diels-Alder (DA) reaction. The tDA adducts exhibited unprecedented thermal stability up to 250 °C, which is 100 °C higher than that of the DA adducts, owing to the higher activation energy (Ea) required for the initial intramolecular step of the reverse process. The stability of the tDA adducts was exploited in the AA + BB type polymerization of tetrafuranic monomers with bis(maleimides), yielding thermally stable (up to 200 °C) yet depolymerasable linear polymers with molecular weights of 10-20 kDa. Only furanic groups were identified as the end-groups of the resulting polymers, suggesting the possibility for post-polymerization and end-group modifications. NMR and GPC kinetic data offered insights into the intermediate formation of classical adducts during polymerization, as well as the stereochemistry of tDA adducts in the polymer chains. Combined thermal analysis (DSC, TGA, and TMA) provided a comprehensive understanding of the reverse DA reaction in the resulting materials. This relatively clean, catalyst- and byproduct-free, well-controlled process, which uses derivatives of biorenewables as monomers, heralds the formation of a new class of thermally recyclable polymers.

New diorganotin(IV) complexes based on a redox-active tetradentate ONNO ligand, namely N,N'-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-1,2-phenylenediamine (LH4), were synthesized. A methodology for the stepwise oxidation of tin(IV)-ONNO derivatives with a stoichiometric amount of p-benzoquinone was developed. This allowed the preparation of tin(IV) complexes containing the ligand in the tetraanionic doubly deprotonated form, in the dianionic state, and a controlled intraligand cyclization to be carried out. It has been found that the diorganotin(IV) compounds with the dianionic form of the ONNO ligand have a ground singlet spin state, but an increase in temperature leads to partial populating of the triplet state and a transition from the diamagnetic form of these complexes to the paramagnetic biradical ones. The UV-vis-NIR spectrum of L2-SnPh2 shows an intense absorption band in the range of 600-1400 nm, corresponding to the intraligand charge transfer (ILCT). The coordination ability of the solvent strongly influences the position of this solvatochromic band. Cyclic voltammetry revealed that this compound undergoes two sequential reversible single-electron oxidations and two sequential reversible single-electron reductions. This cyclic voltammetry remains unchanged even after 100 cycles have been performed.

The structure and properties of sol-gel filled polyimide (PI) films were investigated as a protective coating for the low orbit devices. The organosoluble PI based on 4,4 '-(9-fluorenylidene)dianiline and 3,3 ',4,4 '-diphenyloxide tetracarboxylic acid and tris-(methyldiethoxysiloxy)aluminium (Al-siloxane) and tris-(methyldiethoxysiloxy)iron (Fe-siloxane) as precursors of nanoparticles were used. A comparative analysis of the curing of Al-siloxane and Fe-siloxane in pure state and in the polymer matrix was carried out by FTIR spectroscopy. The type of precursor metal atom has no significant influence on the thermal, mechanical, and dielectric properties of PI nanocomposites, however the filler and the type of precursor metal atom determine their resistance to atomic oxygen (AO). PI filled with nanoparticles based on Fe-siloxane (PI-[FeOSi]) exhibit a higher AO resistance than PI[AlOSi]. The SEM imaging showed that the protection mechanism of PIs with metallosiloxanes nanoparticles against the destructive AO effect is based on the formation of an external protective layer, morphology/continuity of which is determined by the nature of the metal atom. The protective layer on the PI-[FeOSi] surface is less susceptible to microcracking compared to the outer layer formed on the PI-[AlOSi] film.

The bis(carbazolide) complex of Smii, Sm[3,6-But2-1,8-(Me3SiC degrees C)2Carb]2, was synthesized by the transamination reaction of Sm[N(SiMe3)2]2(THF)2with two molar equivalents of carbazole 3,6-But2-1,8-(Me3SiC degrees C)2CarbH. A similar reaction of the less sterically demanding carbazole 3,6-But2-1,8-(PhC degrees C)2CarbH is accompanied by the oxidation of Smii to Smiii and lead to the formation of bis(carbazolide) amido complex [3,6-But2-1,8-(PhC degrees C)2Carb]2Sm[N(SiMe3)2]. For both Sm complexes, hhh2-interactions with C degrees C bonds, which are unconventional for Lnii and Lniii metals, were experimentally confirmed by single-crystal X-ray diffraction, IR and Raman spectroscopy along with QTAIM analysis.

Metalation of bulky tris(2-(piperidin-1-yl-methyl)phenyl)methanol [(C5H10N)CH2C6H4-o]3COH with (Me3Si)2NK in Et2O results in a dimeric potassium alkoxide {[(C5H10N)CH2C6H4-o]3C(μ2-O)K(Et2O)}2 (1). The Et2O molecule can be removed from the K+ coordination sphere affording coordinatively unsaturated alkoxide species which readily traps π-donor molecules. In the presence of excess arene, the reactions result in ηn-π-complexes, retaining in the crystal state a dimeric core {[(C5H10N)CH2C6H4-o]3C(μ2-O)K(ηn-arene)}2 (arene = C6H6 (2), CH3C6H5 (3), C10H8 (4)). With C6H5OMe and C6H5NMe2 molecules containing competing n- and π-donating sites, the reactions proceed differently: the former coordinates to K+ through an oxygen lone pair resulting in {[(C5H10N)CH2C6H4-o]3C(μ2-O)K(κ1-O(Me)C6H5)}2 (5) while for the latter, π-arene interaction turns out to be preferable, yielding {[(C5H10N)CH2C6H4-o]3C(μ2-O)K(η2-C6H5NMe2)}2 (6). The reactions with equimolar amounts of benzene or thiophene afford coordination polymers [{[(C5H10N)CH2C6H4-o]3C(μ2-O)K}2(μ-C6H6)]n (7) and [{[(C5H10N)CH2C6H4-o]3C(μ2-O)K}2(μ-C4H4S)]n (8), in which benzene and thiophene molecules are μ-bridging two K+ ions. The treatment of {[(C5H10N)CH2C6H4-o]3C(μ2-O)K(η2-CH3C6H5))}2 with Me3SiCH2Li or n-BuLi (1.2 eq.) in hexane at 20 °C results in the facile metalation of the Me group of toluene, forming [PhCH2K]n and lithium alkoxide. This model reaction provides a deeper insight into the probable mechanism of metalation of CH bonds under Lochmann-Schlosser superbasic conditions, and the role and the nature of the synergistic effect of two metals. The calculations and QTAIM analysis were performed for 1-8 and model molecules as well.

Micro-Raman spectroscopy of Luna-16 and Luna-24 regolith samples revealed 27 unshocked components, including first-time detections of metallic silicon and arzakite. The study identified sp2-carbon formations (500-1000 degrees C) and proposed a spectral criterion to determine carbon origin (impact, meteoritic, or micrometeoritic). Carbon in Mare Crisium and Fecunditatis regolith was classified as micrometeoritic. Lower carbon content in Luna-24 (2 m depth) suggests increased micrometeoritic bombardment of carbonaceous chondrites in recent time.

Two positional isomers of nitro-hydroxy nicotinic acid, 1H-3-carboxy-5-nitropyridin-2-one (3c5n) and 1H-5-carboxy-3-nitropyridin-2-one (5c3n), both adopt the amide tautomer in the solid state and crystallize in noncentrosymmetric space groups (3c5n: two polymorphs, crystallizing together, P212121 and P21212; 5c3n: Pna21). Polymorph 3c5n-II is 0.15 g cm− 3 less dense than 3c5n-I owing to isolated voids ( 18 Å3 each), yet single-crystal X-ray diffraction, DSC/TGA analyses, and micro-FTIR rule out solvent inclusion, establishing 3c5n-II as a solvent-free polymorph with reduced packing efficiency. In both polymorphs, identical O–H···O chains generated by 21 axis define the primary supramolecular synthon. However, the secondary assembly of these chains differs: the undulating chains of 3c5n-I pack closely to form a dense structure, whereas the nearly planar chains of 3c5n-II assemble less efficiently and thereby generate the voids. NO₂···π(pyridin-2-one) contacts form ladder motifs along the shortest unit cell axis; together with the 21 chains, these motifs favor noncentrosymmetric packing. Periodic DFT (PBE0-D3/def2-TZVPP) gives nearly identical lattice/cohesive energies for 3c5n-I and 3c5n-II despite the density contrast. Relative to 3c5n, the 5c3n isomer gains an additional intermolecular O–H···O bond and a slightly more favorable lattice and cohesive energy, but the total crystal energies remain comparable, suggesting compensation between inter- and intramolecular hydrogen bonding.

In the chemistry of bio-based furans, the Diels-Alder reaction plays an important role as a renewable route for the synthesis of fuels, fine chemicals, and monomers. Nonetheless, the unfavorable kinetic and thermodynamic parameters inherent to the Diels-Alder reaction involving furans as dienes often lead to the reversibility of cycloaddition, resulting in decreased equilibrium conversion and diastereoselectivity. In this study, we present a new strategy for overcoming the problem of reversibility in chemical reactions. We demonstrate that conducting the reaction under solvent-free conditions can facilitate the transition from a molten state formed by the initial reactants to a solid phase containing the reaction product along with an excess of the initial substrate. According to our results, such a liquid-to-solid transition of the reaction mixture can lead to exceptionally high conversion and diastereoselectivity in the furan-maleimide Diels-Alder reaction, particularly for challenging electron-poor furanic substrates. Our approach enables the reversible furan-maleimide Diels-Alder reaction to be performed in a cleaner and more environmentally friendly manner, free from the complexities associated with the use of solvents and the need for purification from side products.

Reaction of tris[2-(2 '-pyridylmethoxy)phenyl]phosphine oxide (L) with f-element nitrates resulted in 1:1 complexes. The isolated complexes of ligand L with La(III), Eu(III), Tb(III), and U(VI) nitrates, and with La(III) chloride were studied in the solid state and solution by IR, Raman, and NMR spectroscopy, X-ray analysis, and also DFT calculations. Composition and structure of the complexes vary with lanthanide cation radius. According to the data of elemental analysis, vibrational spectroscopy, and X-ray diffraction, the ligand is coordinated in tridentate mode in crystalline La(III) and solid Eu(III) complexes:[Ln(OPO,N,Oeth-L)(H2O)(O,O-NO3)3], and in monodentate mode in crystalline complex [Tb(OPO-L)(H2O)2(O,O-NO3)3]. Nitrogen atoms of pyridine fragments of the ligand not involved in coordination produce intra- and intermolecular H-bonds with coordinated water molecules in the second coordination sphere of Ln(III). According to IR, NMR spectrometry, and DFT calculations, the structure of coordination polyhedron of the main species of Ln(III) complexes in acetonitrile solutions is retained including coordination of one of pyridine fragments in the second coordination sphere: [Ln{OPO,N, (N*),Oeth-L}(H2O)(O,O-NO3)3] and[Tb{OPO,(N*)-L}(H2O)2(O,O-NO3)3], where Ln = La, Eu, and N* is the nitrogen atom of pyridine fragment producing intramolecular H-bond with coordinated water molecule. According IR and Raman spectroscopy, ligand L is coordinated in bidentate mode in solid complex [UO2(OPO,N-L)(O,O- NO3)], and uncoordinated nitrogen atoms remain free. Solution structure of uranyl complex is labile and depends on solvent nature. Equilibria of complex species with variable coordination of nitrate ions, ligand L , and with probable involvement of water take place in CD3CN and CDCl3 solutions. Photophysical properties of the prepared Eu(III) and Tb(III) complexes were studied. The preliminary assessment of extraction properties of compound L was made. Stability of studied compounds in acetonitrile solutions was examined, and the structure of one of protolysis product of Eu(III) complex, [Eu(LH)(H2O)(NO3)4], was established by micro-IR and X-ray analysis.