Synthesis, structural and mass spectrometric investigations of pyridinium bis(thiosalicylato)mercurate(II)

The previously-described bis(thiosalicylato)mercury(II) complex [Hg(SC6H4-2-CO2H)2],prepared from HgCl2 and thiosalicylic acid (HSC6H4-2-CO2H) with added NaOH, dissolves in pyridine (py), from which the crystalline pyridinium salt (pyH)2[Hg(SC6H4-2-CO2)2] can be isolated as large colourless blocks. Single crystal X-ray crystallography reveals the crystal to comprise two distinct three-molecule aggregates, namely {Hg[SC6H4-2-C(=O)OH]2(NC5H5)2} and {Hg[SC6H4-2-C(=O)O]2(HNC5H5)2}, which differ in the location of the acidic hydrogen atoms, i.e. either compound-bound for the former species or located on the pyridinium cations in the latter. The thiolate ligands are S,O-chelating and the resultant O2S2 four-coordinate geometries are each based on a distorted disphenoidal geometry. The three-molecule aggregates are sustained by hydroxyl-O‒H…N(pyridine) hydrogen bonds in the case of {Hg[SC6H4-2-C(=O)OH]2(NC5H5)2} whereas the second aggregate features charge-assisted pyridinium-N‒H…O(carboxylate) hydrogen bonds. These aggregates are connected into a three-dimensional architecture by a combination of C‒H…O, π…π, Hg…π and O…π interactions. (pyH)2[Hg(SC6H4-2-CO2)2] was also characterised by negative-ion ESI mass spectrometry, where it showed appreciable stability towards capillary exit voltage-induced fragmentation. In contrast, the S-bonded monodentate thiosalicylate complexes RHg(SC6H4-2-CO2) - (R = Et, Ph or ferrocenyl) undergo facile decarboxylation at relatively low voltages, with the phenyl and ferrocenyl complexes subsequently forming RHgSas an additional fragment ion at high voltages. Aggregate ions formed with the sodium counter-cations of the type [(RHgSC6H4-2- CO2)nNan-1] - show appreciable stability towards fragmentation

[Dicyclohexyl(sulfanylidene)-λ⁵-phosphanyl]methanol

The title compound, [dicyclohexyl(sulfanylidene)-λ⁵-phosphanyl]methanol, Cy₂P(=S)CH₂OH (1), was obtained from the reaction between [Cy₂P(CH₂OH)₂]Cl with one molar equivalent of NaOH and an excess of elemental sulfur (powdered). Characterization was by a single-crystal X-ray structure determination as well as IR, and ¹D-NMR (¹H, ¹³C{1H}, ³¹P{1H}), and 2D-NMR (DEPT-135 and HSQC) spectroscopy, ESI mass spectrometry, and elemental analysis. X-ray crystallography on Compound 1 shows the phosphorus atom to be tetrahedrally coordinated within a non-symmetric C₃S donor set but with relatively minor distortions from the ideal geometry. In the molecular packing, hydroxyl-O–H⋯S(thione) hydrogen bonds led to supramolecular helical chains along the b-axis direction

Kinetics and Mechanism of Electron Transfer Reaction of an Adipato Bridged Iron(III)-Salen Complex with Dithionite Ion in Perchloric Acid Medium

Redox kinetics of the reaction of an adipato bridged iron(III)-salen complex, [(Fe(salen))2adi] with dithionite ion, S2O42–, was investigated in perchloric acid at I = 0.05 mol dm–3 (NaClO4) and T = 29 ± 1 °C. Spectrophotometric titrations indicated consumption of one mole of S2O42– per mole of [(Fe(salen))2adi] reduced. Under pseudo-first order conditions of [S2O42–] above ten-fold excess of concentration of [(Fe(salen))2adi], observed rates increased with increase in [S2O42–] and second order rate constants were fairly constant (0.285 ± 0.01 dm3 mol–1 s–1) indicating first order dependence of the rate on [(Fe(salen))2adi]. A plot of logkobs versus log[S2O42–] was linear and gave a slope of 1.0 indicating first order dependence of the rate on [S2O42–]. The reaction rate increased with increase in [H+] within 3 × 10–3 mol dm–3 ≤ [H+] ≤ 14 × 10–3 mol dm–3. The reaction was unaffected by variation of ionic strength and dielectric constant of the medium. Addition of anion and cation did not catalyze the reaction. The reaction has been analyzed on the basis of an inner-sphere mechanism mediated by proton transfer

Platinum(II) complexes containing pyridyl-substituted thiourea dianion and monoanion ligands: Synthesis, structural chemistry, and theoretical investigations

Reactions of cis-[PtCl2(PPh3)2] with the 2-pyridyl-substituted thioureas py(CH2)nNHC(S)NHC6H4R (R = H, OMe or NO2; n = 0, 1 or 2) in methanol with Et3N base, followed by precipitation with water gave good yields of the complexes [Pt{SC(NC6H4R)(N(CH2)npy)}(PPh3)2]. The compounds were characterised 1H NMR, 31P{1H} NMR, FTIR and single crystal X-ray crystallography. The initial NMR investigation indicated the possibility of isomerism in the complexes. 31P{1H} NMR investigations revealed the presence of an initial distal isomer for the dianion complexes, which underwent solution phase isomerization into the proximal isomeric forms of the complexes and/or a mixture of the proximal and distal isomers. The opposite trend was recorded for the monoanionic complex with the formation of an initial proximal isomer and subsequent isomerisation into 1:3 mixture of the distal and proximal isomeric forms of the complex. The degree of isomerization was observed to be related to the difference in energy between the two isomeric forms of the complex and the nature and size of the R substituents in the complex. The molecular geometries of a number of the compounds showed a distorted square-planar geometry defined by a NP2S donor set. The thiourea ligand acts as (N,S)-chelating dianionic ligand so that each donor atom is opposite a phosphane-P atom; a trans-influence is evident on the Pt-P bonds. In each complex, the pyridyl-substituted nitrogen is coordinated to platinum. The cationic complex [Pt{SC(NPh)(NHCH2py)}(PPh3)2]+ was also isolated as its BF4- salt by addition of excess NaBF4 to the reaction mixture. In this complex, the thiourea monoanion coordinates in a distal manner, with the NHCH2py group remote from the platinum centre. Charge-assisted ammonium-Nsingle bondH…N(pyridyl) bonding leads to dimeric aggregates. These, along with the neutral molecules [Pt{SC(Np-C6H4R2)(N(CH2)npy)}(PPh3)2] are assembled into the three-dimensional crystal via weak non-covalent interactions. Characterisation by 31P{1H} NMR spectroscopy showed the presence of several isomeric species in solution

Synthesis, Spectroscopic, Biological and DFT Studies of 2,4,6-Tris(4-Carboxyphenylimino-41-Formylphenoxy)-1,3,5-Triazine and its Trinuclear Dy(III) and Er(III) Salen Capped Complexes

Communication in Physical Sciences 2020, 7(3): 182-202 Authors: Uchechukwu S. Oruma, Pius O. Ukoha, Collins U. Ibeji, Lawrence N. Obasi, Obinna C. Okpareke, Ebubechukwu N. Dim, Klaus Jurkschat and Ponnadurai Ramasami Received 29 August  2021/Accepted 23 September 2021 A tripodal Schiff base ligand, 2,4,6-tris(4-carboxyphenylimino-41-formylphenoxy)-1,3,5-triazine (H3CT) and its trinuclear Dy(III) and Er(III) complexes were synthesized. Characterization of these compounds was done via UV-Visible, IR, 1H, and 13C NMR spectroscopies, elemental analysis, and molar conductivity measurements. The spectral studies indicate that the ligand is hexadentate and coordinates to Dy/Er(III) ions through the oxygen atoms of the carboxylic group. The trinuclear complexes were characterized as being bridged by a carboxylic group to the Dy(III) and Er(III) salen centers and display a coordination number of six. Biological studies revealed that the Dy(III) complex showed the highest activity against tested microorganisms and also gave the highest percentage parasitemia inhibition (84.0 %) relative to Artesunate (87.2 %). DFT calculations were carried out to enhance understanding of H3CT at the molecular level based on  (B3LYP)/6-31+G(d,p). The molecular docking results revealed the binding mode of H3CT complexed with Staphylococcus aureus

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