Revisiting the reactivity of Ru3(CO)12 with PhC≡CPh (diphenylacetylene)-new findings of a thermic effect towards higher nuclearity

177-184In this paper, we report tri- and tetranuclear ruthenium carbonyl compounds containing PhC≡CPh ligand showing μ3-η2, μ3-η4, μ4-η2 coordination modes. A one-pot reaction between [Ru3(CO)12] and PhC≡CPh in THF (tetrahydrofuran) at 66 °C has given the new trinuclear compound [Ru3(CO)6(μ-CO)2(μ3-η4-C4Ph4)] (2) in 30% yield together with the previously reported [Ru3(CO)8(μ3-η2-C2Ph2)2] (1) in 25% yield. Compound 1 converts to 2 under refluxing condition in THF. A similar reaction involving [Ru3(CO)12] with PhC≡CPh in refluxing benzene (80 °C) afforded previously reported closo-tetraruthenium compounds [Ru4(CO)12(μ4-η2-C2Ph2)] (3) and [Ru4(CO)10(μ-CO)(μ4-η2-C2Ph2)2] (4) in 25 and 16% yields, respectively, along with 2 in 20% yield. Compounds 1, 2 and 4 have been characterized by single-crystal X-ray diffraction analysis in addition to IR and 1H NMR spectroscopic methods

Molybdenum compounds bearing pymS (pyrimidine-2-thiolato) and tertiary phosphine ligands

741-746In this paper we have reported mono- and dinuclear molybdenum compounds containing doubly bridging pymS (pyrimidine-2-thiolato) and P(Fu)3 {(Fu = (2-furyl)phosphine)} or P(OMe)3 (trimethyl phosphite). One-pot reaction between [Mo(CO)3(NCMe)3] and pymSH (pyrimidine-2-thiol) in the presence of P(Fu)3 in THF at 50 °C gives the previously reported eight coordinate compound [Mo(к2-pymS)4] (1) in 17% yield and two new compounds [Mo(CO)4(P(Fu)3)2] (2) and [Mo2(CO)4(μ-к2-pymS)2(P(Fu)3)2] (3) in 51 and 15% yields, respectively. A similar reaction involving P(OMe)3 furnishes two mononuclear compounds [Mo(CO)2(κ2-pyS)2(P(OMe)3)] (4) and [Mo(CO)4(P(OMe)3)2] (5) in 20 and 35% yields, respectively. Compounds 2 and 4 are characterized by single-crystal X-ray diffraction analysis in addition to IR, 1H NMR and 31P{1H} NMR spectroscopic methods

Synthesis, structure, magnetism, and coordination chemistry of some self assembled polynuclear clusters and grids of first row transition metal ions derived from polytopic hydrazone ligands

A collection of hydrazone based ligands ranging from simple ditopic to pentatopic have been synthesized and allowed to react with different transition metals ions (e.g. Mn(II), Cu(II) ). The ligands varied in terms of their coordination capability (ditopic vs. tritopic ), terminal functional group (e.g. -NH₂, vs. -CH₃), and overall ligand flexibility (e.g. rigid pyridine vs. -NH central piece). The ditopic ligand (e.g. pomp) gave tetranuclear M(II)₄(M = Mn(II), Cu(II)) complexes when treated with Mn(II) and Cu(II) metal salts. In all of the tetranuclear complexes, metal ions were hydrazone oxygen bridged except for the copper case where Cu(II) centers were bridged by a mixture of N-N diazine and hydrazone oxygen groups. Intramolecular antiferromagnetism was observed in all cases. Tritopic ligands with a flexible secondary -NH central piece yielded mostly trinuclear linear complexes with Cu(II) and trinuclear nonlinear complexes with Mn(II) ions. The inability of this class of ligands to form nonanuclear grids was attributed to the unusual flexible nature of the ligands which is unsuitable for grid formation. Intramolecular antiferromagnetism was observed in all of the trinuclear complexes. Tritopic ligands with pyridine as a relatively rigid center piece (e.g. 2pomp) yielded [3 x 3] nonanuclear Mn(II)₉ grids when reacted with Mn(II). However, with Cu(II) ions this ligand yielded octanuclear Cu(II)₈ pinwheel clusters. All of the Mn(II)₉ grids showed intramolecular antiferromagnetism whereas pinwheels were found to show ferromagnetism, which is relatively rare in this class of polynuclear complexes. Changing the choice to two different donor functional groupings gave two unprecedented outcomes. An oxalic acid dihydrazide based ditopic ligand yielded an inorganic [2] catenane, with mixed oxidation states when reacted with Co(II) ions. This is the first example of an inorganic cobalt catenane. However, due to large metal separations, no magnetic exchange coupling was observed in the complex. In another instance, an extended tritopic ligand formed an enormous Cu(II)₃₆ cluster using the extra coordination capability of the oxime substituents at two ends of the ligand. The cluster showed intramolecular antiferromagnetism. A logical and symmetric extension of the tritopic ligand led to a pentatopic ligand which gave a [5 x 5] square Mn(II)₂₅ cluster. STM imaging techniques were employed to explore the structure of the cluster. Topographic images clearly showed the [5 x 5] square grid-like array on a HOPG surface

Synthesis of Novel Tritopic Hydrazone Ligands: Spectroscopy, Biological Activity, DFT, and Molecular Docking Studies

Polytopic organic ligands with hydrazone moiety are at the forefront of new drug research among many others due to their unique and versatile functionality and ease of strategic ligand design. Quantum chemical calculations of these polyfunctional ligands can be carried out in silico to determine the thermodynamic parameters. In this study two new tritopic dihydrazide ligands, N’2, N’6-bis[(1E)-1-(thiophen-2-yl) ethylidene] pyridine-2,6-dicarbohydrazide (L1) and N’2, N’6-bis[(1E)-1-(1H-pyrrol-2-yl) ethylidene] pyridine-2,6-dicarbohydrazide (L2) were successfully prepared by the condensation reaction of pyridine-2,6-dicarboxylic hydrazide with 2-acetylthiophene and 2-acetylpyrrole. The FT-IR, 1H, and 13C NMR, as well as mass spectra of both L1 and L2, were recorded and analyzed. Quantum chemical calculations were performed at the DFT/B3LYP/cc-pvdz/6-311G+(d,p) level of theory to study the molecular geometry, vibrational frequencies, and thermodynamic properties including changes of ∆H, ∆S, and ∆G for both the ligands. The optimized vibrational frequency and (1H and 13C) NMR obtained by B3LYP/cc-pvdz/6-311G+(d,p) showed good agreement with experimental FT-IR and NMR data. Frontier molecular orbital (FMO) calculations were also conducted to find the HOMO, LUMO, and HOMO–LUMO gaps of the two synthesized compounds. To investigate the biological activities of the ligands, L1 and L2 were tested using in vitro bioassays against some Gram-negative and Gram-positive bacteria and fungus strains. In addition, molecular docking was used to study the molecular behavior of L1 and L2 against tyrosinase from Bacillus megaterium. The outcomes revealed that both L1 and L2 can suppress microbial growth of bacteria and fungi with variable potency. The antibacterial activity results demonstrated the compound L2 to be potentially effective against Bacillus megaterium with inhibition zones of 12 mm while the molecular docking study showed the binding energies for L1 and L2 to be −7.7 and −8.8 kcal mol−1, respectively, with tyrosinase from Bacillus megaterium

Supramolecular Mn(II) and Mn(III) Grid Complexes with [Mn9(u2-O)12] Core Structures - Structural, Magnetic, Redox Properties, and Surface Studies

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