Висвітлення діяльності опозиційного руху в УРСР у ІІ пол. 1960-х – поч. 1980-х рр. у наукових дослідженнях

В статті досліджуються основні історіографічні тенденції вивчення діяльності опозиційного руху в УРСР в другій половині 1960-х – початку 1980-х рр.В статье исследуются основные историографические тенденции изучения оппозиционного движения в УССР во второй половине 1960-х – начале 1980-х гг.The article is dedicated to the main historiographical trends in the investigations of oppositional movements in Soviet Ukraine during second half of 1960th – at the beginning 1980th

d-d Dative Bonding Between Iron and the Alkaline-Earth Metals Calcium, Strontium, and Barium

Double deprotonation of the diamine 1,1 '-(tBuCH(2)NH)-ferrocene (1-H-2) by alkaline-earth (Ae) or Eu(II)metal reagents gave the complexes1-Ae (Ae=Mg, Ca, Sr, Ba) and1-Eu.1-Mg crystallized as a monomer while the heavier complexes crystallized as dimers. The Fe...Mg distance in1-Mg is too long for a bonding interaction, but short Fe...Ae distances in1-Ca,1-Sr, and1-Ba clearly support intramolecular Fe...Ae bonding. Further evidence for interactions is provided by a tilting of the Cp rings and the related(1)H NMR chemical-shift difference between the Cp alpha and beta protons. While electrochemical studies are complicated by complex decomposition, UV/Vis spectral features of the complexes support Fe -> Ae dative bonding. A comprehensive bonding analysis of all1-Ae complexes shows that the heavier species1-Ca,1-Sr, and1-Ba possess genuine Fe -> Ae bonds which involve vacant d-orbitals of the alkaline-earth atoms and partially filled d-orbitals on Fe. In1-Mg, a weak Fe -> Mg donation into vacant p-orbitals of the Mg atom is observed

Different formation kinetics and photoisomerization behavior of self-assembled monolayers of thiols and dithiolanes bearing azobenzene moieties

Self-assembled monolayers (SAMs) containing azobenzene moieties are very attractive for a wide range of applications, including molecular electronics and photonics, bio-interface engineering and sensoring. However, very little is known about the aggregation and photoswitching behavior that azobenzene units undergo during the SAM formation process. Here, we demonstrate that the formation of thiol based SAMs containing azobenzenes (denoted as AzoSH) on gold surfaces is characterised by a two step adsorption kinetics, while a three-step assembly process has been identified for dithiolane-based SAMs containing azobenzenes (denoted AzoSS). The H-aggregation on the AzoSS SAMs was found to be remarkably dependent on the time of self-assembly, with less aggregation as a function of time. While photoisomerization of the AzoSH was suppressed for all different assembly times, the reversible trans–cis photoisomerization of AzoSS SAMs formed over 24 hours was clearly observed upon alternating UV and Vis light irradiation. We contend that detailed information on formation kinetics and related optical properties is of crucial importance for elucidating the photoswitching capabilities of azobenzene based SAMs

Enhanced adsorption capacity and selectivity towards strontium ions in aqueous systems by sulfonation of CO2 derived porous carbon

Oxygen-enriched carbon materials derived from carbon dioxide were functionalized using sulfonic acid to remove Sr2+ ions from aqueous solutions. Synthesized sulfonated porous carbon materials (PC-SO3H) showed higher adsorption capacity and selectivity towards Sr2+ than non-functionalized porous carbons (PC). The formation of the C-SO3H functional group in PC-SO3H and its ability to proton exchange with Sr2+ was the main contributor to the enhanced performance. The maximum uptake capacity of Sr2+ by PC-SO3H was 18.97 mg g−1, which was 1.74 times greater than PC. PC-SO3H removed 99.9% and 97.6% of Sr2+ from aqueous solutions with initial Sr2+ concentrations of 5 mg L−1 and 10 mg L−1, respectively. Sr2+ adsorption showed rapid kinetics, reaching the adsorption equilibrium within 1 h with high adsorption capacity at equilibrium which is 3.52 times greater than that of PC. Additionally, PC-SO3H selectively adsorbed Sr2+ even in the presence of excess amounts of competing ions. Sulfonation of oxygen-enriched carbon had a significant effect on enhancing the affinity towards Sr2+ and suppressing adsorption towards other competing ions

Versatile Coordination of Cyclopentadienyl-Arene Ligands and Its Role in Titanium-Catalyzed Ethylene Trimerization

Cationic titanium(IV) complexes with ansa-(η5-cyclopentadienyl,η6-arene) ligands were synthesized and characterized by X-ray crystallography. The strength of the metal-arene interaction in these systems was studied by variable-temperature NMR spectroscopy. Complexes with a C1 bridge between the cyclopentadienyl and arene moieties feature hemilabile coordination behavior of the ligand and consequently are active ethylene trimerization catalysts. Reaction of the titanium(IV) dimethyl cations with CO results in conversion to the analogous cationic titanium(II) dicarbonyl species. Metal-to-ligand backdonation in these formally low-valent complexes gives rise to a strongly bonded, partially reduced arene moiety. In contrast to the η6-arene coordination mode observed for titanium, the more electron-rich vanadium(V) cations [cyclopentadienyl-arene]V(NiPr2)(NC6H4-4-Me)+ feature η1-arene binding, as determined by a crystallographic study. The three different metal-arene coordination modes that we experimentally observed model intermediates in the cycle for titanium-catalyzed ethylene trimerization. The nature of the metal-arene interaction in these systems was studied by DFT calculations.

Predicting Stable Molecular Structures for (RNC)(2)(AuX)-X-I Complexes

Calculations have been performed at the MP2 and DFT levels for investigating the reasons for the difficulties in synthesizing bis(isocyanide)gold(I) halide complexes. Three-coordinated gold(I) complexes of the type (R3P)(2)(AuX)-X-I (1) can be synthesized, whereas the analogous isocyanide complexes (RNC)(2)(AuX)-X-I (2) are not experimentally known. The molecular structures of (R3P)(2)(AuX)-X-I (X = Cl, Br, and I) and (RNC)(2)(AuX)-X-I with X = halide, cyanide, nitrite, methylthiolate, and thiocyanate are compared and structural differences are discussed. Calculations of molecular properties elucidate which factors determine the strength of the gold-ligand interactions in (RNC)(2)(AuX)-X-I. The linear bonding mode of RNC favors a T-shaped geometry instead of the planar Y-shaped trigonal structure of (R3P)(2)(AuX)-X-I complexes that have been synthesized. An increased polarity of the Au-X bond in 2 leads to destabilization of the Y-shaped structure. Chalcogen-containing ligands or cyanide appear to be good X-ligand candidates for synthesis of (RNC)(2)(AuX)-X-I complexes.Peer reviewe