Koszul Bicomplexes and Generalized Koszul Complexes in Projective Dimension One

We describe Koszul type complexes associated with a linear map from any module to a free module, and vice versa with a linear map from a free module to an arbitrary module, generalizing the classical Koszul complexes. Given a short complex of finite free modules, we assemble these complexes to what we call Koszul bicomplexes. They are used in order to investigate the homology of the Koszul complexes in projective dimension one. As in the case of the classical Koszul complexes, this homology turns out to be grade sensitive. In a special setup, we obtain necessary conditions for a map of free modules to be lengthened to a short complex of free modules.     

The Synthesis of New Triazole Ligands and Determination of Complex Stability Constants with Transition Metal Cations in Aqueous Media

Six new triazole compounds were synthesized. These compounds containing the substituted benzylidenamino group were obtained by reaction of 3-(pyridine-4-yl)-5-p-tolyl-4-amino-4H-l,2,4-triazole 1 with the corresponding aldehyde. The reduced forms were prepared with NaBH₄ in methanol. The structures of the compounds were determined by IR, ¹H NMR, and ¹³C NMR spectral data, and their interaction with cations such as Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Ba²⁺, Sr²⁺, Ca²⁺, Cu²⁺, Cr³⁺, Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Pb²⁺ and Ag⁺ were investigated by using UV-visible spectrophotometry. Of the tested metal cations, Cu²⁺, Cr³⁺, Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Pb²⁺ and Ag⁺ complexed with the ligands. The complex stability constants (log ₁₀ K) were measured in slightly acidic aqueous media at 25.0±0.1 °C. These stability constants were determined by measuring the increase in solubility of the nearly insoluble ligand molecule due to complex formation with a soluble cation, and this method is discussed. It was found that the position of chlorine atoms on the benzene ring strongly affects the complexation of Cu²⁺ ion with these ligands.     

Cleavage of acetylenic substituents from camphor-derivatives by copper(I) chloride

Copper(I) chloride was found to be a highly efficient reagent to promote the cleavage of acetylenic substituents from the camphor skeleton of compounds 1 containing two C-C triple bonds as well as from the compounds 6 and 7 containing one. This is a formal reversal of the formation of these compounds by the reaction of acetylides with keto and imino groups in compound 18. The substituent R at the triple bond modifies the reactivity and regioselectivity. As intermediates in the process we identified complexes of the types [Cu(L)_depr] (where (L)_depr denotes a deprotonated camphor-derived ligand (L)) and [CuCl(L)]. Quantum mechanical calculations support and rationalize the experimental results.     

Synthesis and characterization of tris{2-(N,N-bis(diphenylphosphino) aminoethyl} amine derivatives: Application of a palladium(II) complex as a pre-catalyst in the Heck and Suzuki cross-coupling reactions

The polydendate bis(phosphino)amine, tris{2-(N,N-bis(diphenylphosphino)aminoethyl}amine 1 has been prepared in a single step from the reaction of tris(2-aminoethyl)amine with six equivalents of PPh₂Cl in the presence of NEt₃ in THF. Oxidation of 1 with aqueous H₂O₂, elemental sulfur or grey selenium gave the corresponding oxide, sulfide or selenide derivatives. [{(P(E)Ph₂)₂NCH₂CH₂}₃N] (E: 2a O, 2b S, 2c Se), respectively. Reaction of [{(PPh₂)₂NCH₂CH₂}₃N] with 3 equiv. of PdCl₂(cod) or PtCl₂(cod) gave the corresponding chelate complexes, [Pd₃Cl₆1] or [Pt₃Cl₆1]. The new compounds were fully characterized by NMR, IR spectroscopy and elemental analysis. The catalytic activity of the Pd(II) complex was tested in the Suzuki coupling and Heck reactions. The Pd(II) complex catalyzed the Suzuki coupling and Heck reaction affording biphenyls and stilbenes, respectively, in high yields.     

Titanium Salalen Catalyzed Enantioselective Benzylic Hydroxylation

The titanium complex of the cis-1,2-diaminocyclohexane (cis-DACH) derived Berkessel-salalen ligand is a highly efficient and enantioselective catalyst for the asymmetric epoxidation of terminal olefins with hydrogen peroxide (“Berkessel-Katsuki catalyst”). We herein report that this epoxidation catalyst also effects the highly enantioselective hydroxylation of benzylic C−H bonds with hydrogen peroxide. Mechanism-based ligand optimization identified a novel nitro-salalen Ti-catalyst of the highest efficiency ever reported for asymmetric catalytic benzylic hydroxylation, with enantioselectivities of up to 98 % ee, while overoxidation to ketone is marginal. The novel nitro-salalen Ti-catalyst also shows enhanced epoxidation efficiency, as evidenced by e.g. the conversion of 1-decene to its epoxide in 90 % yield with 94 % ee, at a catalyst loading of 0.1 mol-% only.     

Unlocking a (Pseudo)-Mechanically Interlocked Molecule with a Coronene “Shoehorn”

Mechanically interlocked molecules (MIMs) have gained increasing interest during the last decades, not only because of their aesthetic appeal, but also because their unique properties have allowed them to find applications in nanotechnology, catalysis, chemosensing and biomedicine. Herein we describe how a pyrene molecule with four octynyl substituents can be easily encapsulated within the cavity of a tetragold(I) rectangle-like metallobox, by template formation of the metallo-assembly in the presence of the guest. The resulting assembly behaves as a mechanically interlocked molecule (MIM), in which the four long limbs of the guest protrude from the entrances of the metallobox, thus locking the guest inside the cavity of the metallobox. The new assembly resembles a metallo-suit[4]ane, given the number of protruding long limbs and the presence of the metal atoms in the host molecule. However, unlike normal MIMs, this molecule can release the tetra-substituted pyrene guest by the addition of coronene, which can smoothly replace the guest in the cavity of the metallobox. Combined experimental and computational studies allowed the role of the coronene molecule in facilitating the release of the tetrasubstituted pyrene guest to be explained, through a process that we named “shoehorning”, as the coronene compresses the flexible limbs of the guest so that it can reduce its size to slide in and out the metallobox.     

Outstanding Quadratic to Septic Optical Nonlinearity at Dipolar Alkynylmetal-Porphyrin Hybrids

Porphyrins are important macrocycles with applications in several areas including therapy, catalysis, and sensing. Strong nonlinear optical (NLO) responses are the key to fully exploiting the potential of these biocompatible molecules. We herein report that certain metal-alkynyl donor/nitro acceptor-functionalized porphyrins are attractive candidates for NLO applications. We show that specific examples exhibit record quadratic optical nonlinearity, exceptional two-photon absorption, and outstanding three-photon absorption, and we report the first porphyrins that exhibit four-photon absorption. The two-, three-, and four-photon absorption maxima are found at the corresponding multiples of linear absorption bands that time-dependent density functional theory assigns as admixtures of porphyrin-localized π*←π and donor-porphyrin to porphyrin-acceptor charge-transfer transitions.     

Evoking Ferroptosis by Synergistic Enhancement of a Cyclopentadienyl Iridium-Betulin Immune Agonist

Ferroptosis is a form of programmed cell death driven by iron-dependent lipid peroxidation (LPO) with the potential for antitumor immunity activation. In this study, a nonferrous cyclopentadienyl metal-based ferroptosis inducer [Ir(Cp*)(Bet)Cl]Cl ( Ir-Bet ) was developed by a metal-ligand synergistic enhancement (MLSE) strategy involving the reaction of [Ir(Cp*)Cl]₂Cl₂ with the natural product Betulin. The fusion of Betulin with iridium cyclopentadienyl (Ir-Cp*) species as Ir-Bet not only tremendously enhanced the antiproliferative activity toward cancer cells, but also activated ferritinophagy for iron homeostasis regulation by PI3K/Akt/mTOR cascade inhibition with a lower dosage of Betulin, and then evoked an immune response by nuclear factor kappa-B (NF-κB) activation of Ir-Cp* species. Further immunogenic cell death (ICD) occurred by remarkable ferroptosis through glutathione (GSH) depletion, glutathione peroxidase 4 (GPX4) deactivation and ferritinophagy. An in vivo vaccination experiment demonstrated desirable antitumor and immunogenic effects of Ir-Bet by increasing the ratio of cytotoxic T cells (CTLs)/regulatory T cells (Tregs).     

The preparation,crystal structure and electrochemistry of (5Z,5′Z)-2,2′-(alkane-α,ω-diylsulfanyldiyl)bis(5-(3-pyridylmethylene)-3,5-dihydro-4H-imidazol-4-ones) and their complexes with cobalt(II) chloride

A series of S-alkylated derivatives of 2-thiohydantoins, containing two 5-(3-pyridylmethylene)-3,5-dihydro-4H-imiazole-4-one fragments joined by polymethylene bridges with different numbers of carbon atoms, was synthesized. The title (5Z,5′Z)-2,2′-(alkane-α,ω-diylsulfanyldiyl)bis(5-(3-pyridylmethylene)-3,5-dihydro-4H-imidazol-4-ones) (L) were obtained by alkylation of 5-(3-pyridylmethylene)-3-phenyl-2-thiohydantoine by 1,2-dibromoethane, 1,6-dibromohexane or 1,10-dibromodecane in DMF in the presence of potassium carbonate. The complexes of ligands L with CoCl₂ · 6H₂O have been synthesized. It is shown that, regardless of the L:CoCl₂ ratio, complexes with LCoCl₂ composition are obtained in all cases. The structure of the cobalt(II) chloride complex with (5Z,5′Z)-2,2′-(ethane-1,2-diyldisulfanyldiyl)bis(5-(3-pyridylmethylene)-3-phenyl-3,5-dihydro-4H-imidazol-4-one) was determined by means of the RSA method. The cobalt atom in this complex has a tetrahedral ligand environment and it is coordinated by two chloride anions and two nitrogen atoms of pyridine fragments, forming a 19-membered metallocycle. Electrochemical investigations of the synthesized ligands and complexes have been made by CVA and RDE methods. It is established that the first stage of reduction for the complexes takes place on the metal, whereas the first stage of oxidation takes place on the coordinated chloride-anions.