Group IB metal chemistry : V. Some fluxional complexes containing copper or silver

Fluxional poly(pyrazolyl)borate complexes of copper and silver, including the carbonyl Cu(CO)B(pz)₄, contain coordinated and free pyrazolyl groups, which interchange rapidly on the NMR time scale at room temperature; low temperature limiting spectra can be obtained for some copper complexes at ?100°.     

Effects of Different Solvent Characteristics on the Proton-Ligand and Ni2+-, Sm3+-, AND Yb3+- Ligand Formation Constants of 5,5-Dimethyl-Cyclohexane-2-(2-Hydroxyphenyl)Hydrazono- 1,3-Dione (DCPHD) in Various Mixed Aqueous Solvents-(II)

Complex equilibria of DCPHD with proton and Ni²⁺, Sm³⁺, and Yb³⁺ ions has been measured in various mixed aqueous solvents, viz: isopropanol-water, acetone-water, ethanol-water, and methanol-water. Based on potentiometric equilibrium measurements of hydrogen ion concentration at 30°C, ionic strenght 0.10 M (KNO₃) and in the above various mixed aqueous solvents, the values of the protonation constants of DCPHD and the stability constants of DCPHD with Ni²⁺, Sm³⁺, and Yb³⁺ have been evaluated. The variation of protonation and stability constants with the inverse of dielectric constant or mole fraction of the solvent was studied. Application of Fuoss expression and consideration of electrosatic and non-electrostatic effects are made to explain the values of the constants.     

Heterometric microdetermination of cobalt using nitron as titrant

Small amounts of cobalt (0.1–0.25 mg in 15 ml solution) were determined heterometrically in the presence of potassium thiocyanate by titration with nitron acetate solution. A strong electrolyte (Na₂SO₄) must be added to obtain a clear end point. The titration can be carried out in the presence of a number of diverse ions e.g., Cd²⁺, Ni²⁺, Pb²⁺, Mn²⁺, Cr³⁺, MoO₄^2?, WO₄², CrO₄^2?, NO₃^?, Au³⁺, Pt⁴⁺ without interference; Fe³⁺ can be masked with NaF. Copper and zinc interfere and must be absent. The titration takes about 2–3 min. and the maximum error was 1.5%.     

Syntheses and magneto-structural study of several polynuclear copper(II) complexes derived from 1,3-Bis(dimethylamino)-2-propanolato

The syntheses, structural characterization, and magnetic behavior of the three new polynuclear copper(II) complexes with formulas [Cu(4)(eta(2):mu-CH(3)COO)(2)(mu-OH)(2)(mu-OH(2))(mu-bdmap)(2)](ClO(4))(2).H(2)O (1), [Cu(8)(NCO)(2)(eta(1):mu-NCO)(4)(mu-OH)(2)(mu(3)-OH)(2)(mu-OH(2))(3)(mu-bdmap)(4)](ClO(4))(2)x2H(2)O (2), and [Cu(9)(eta(1):mu-NCO)(8)(mu(3)-OH)(4)(OH(2))(2)(mu-bdmap)(4)](ClO(4))(2).4H(2)O (3), in which bdmapH is 1,3-bis(dimethylamino)-2-propanol, are reported. Tetranuclear complex 1 crystallizes in the triclinic system, space group P, with unit cell parameters a = 12.160(1) A, b = 13.051(1) A, c = 13.235(1) A, alpha = 110.745(1) degrees , beta = 109.683(1) degrees , gamma = 97.014(1), and Z = 2. Octanuclear complex 2 crystallizes in the monoclinic system, space group C2/c, with unit cell parameters a = 26.609(1) A, b = 14.496(1) A, c = 16.652(1) A, beta = 97.814(1) degrees , and Z = 4, and nonanuclear complex 3 crystallizes in the monoclinic system, space group C2/c, with unit cell parameters a = 24.104(1) A, b = 13.542(1) A, c = 24.355(1) A, beta = 109.98(1) degrees , and Z = 4. The magnetic behavior of the three complexes has been checked showing strong antiferromagnetic coupling in all the cases.     

Comparative study of HPLC-DAD and HPTLC for the simultaneous determination of a new multitarget antidiabetic ternary mixture in combined tablets

Qternmet XR® (FDA approval, May 2019) is a multitarget anti-diabetic drug combination composed of metformin (MET), saxagliptin (SAX) and dapagliflozin (DAP). To our present knowledge, no analytical reports were found in the scientific databases for the simultaneous quantification of MET, SAX and DAP in their ternary combined tablets, moreover, no articles have attempted the simultaneous estimation of the cited drugs in any matrix using high-performance liquid chromatography with diode-array detection (HPLC–DAD) or high-performance thin-layer chromatography (HPTLC) technique. The current work represents a comparative study on two developed and validated chromatographic methods for the simultaneous determination of the ternary mixture (MET, SAX and DAP) in pure form and in combined tablet dosage form. The first method is reversed-phase HPLC using Agilent C18 column (4.6 × 250 mm, 5 μm p.s.) with a mobile phase consisting of acetonitrile and acidic aqueous phase pH 3 with a photodiode array detection at 230 nm. The second method is HPTLC in which drug solutions were applied to Merck HPTLC silica gel plates developed with a mixture of chloroform:methanol:water:acetic acid (7.4:2.6:0.5:0.01, v/v) and scanned at 224 nm. Both methods were fully validated following the ICH guidelines in terms of linearity, accuracy, precision, selectivity and robustness.

Representative HPLC (a) and HPTLC (b) chromatograms for a ternary mixture of metformin (MET), saxagliptin (SAX) and dapagliflozin (DAP)

     

Iodometric microdetermination of some insoluble salts of silver,lead and mercury(II)

Summary An indirect iodometric method has been developed for the determination of AgCl, AgBr, AgI, PbCl₂, PbBr₂, PbI₂, PbSO₄ and HgI₂. The method does not require a prior dissolution of the sample. It is based on the exchange reaction between the insoluble salt and hydrogen sulphide, which yields a strong acid corresponding to the anion of the salt and in amount equivalent to the cation. The liberated acid is determined iodometrically. The method is simple, rapid and accurate.

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Zusammenfassung Eine indirekte jodometrische Methode zur Bestimmung von AgCl, AgBr, AgJ, PbCl₂, PbBr₂, PbJ₂, PbSO₄ und HgJ₂ wurde ausgearbeitet. Die Probe muß dazu nicht gelöst werden. Die Bestimmung beruht auf der Austauschreaktion zwischen dem unlöslichen Salz und Schwefelwasserstoff, die zur Freisetzung der dem Anion entsprechenden starken Säure in äquivalenter Menge führt. Diese wird jodometrisch titriert.

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In memoriam Professor Cecil L. Wilson.     

Crystal structure of a new pentadentate symmetrical: di[4-(phenylimino)pentan-2-one] ether. Structural and electrochemical studies of its Co<Superscript>II</Superscript>, Ni<Superscript>II</Superscript>, Cu<Superscript>II</Superscript> and Cd<Superscript>II</Superscript> complexes

The crystal structure of a new symmetrical pentadentate N₂O₃ Schiff base: di[4-(phenylimino)pentan-2-one] ether (H₂L) is described. In the solid state, the ligand appears as a keto-imine tautomer, while in DMSO solution, the eneamine form is observed. This ligand coordinates cobalt(II), nickel(II), copper(II) and cadmium(II). The structures of these new complexes are described using infrared and electronic spectroscopy, ¹H-n.m.r. and d.s.c. The cyclic voltammograms of the ligand and the complexes in DMF are discussed.     

Photochemical reactivities of photosensitive polymers containing chalcone derivatives

Monomeric vinyl chalcone derivatives were prepared by the condensation reaction of p-hydroxybenzaldehyde with acetophenone derivatives in the presence of sodium ethoxide as a base, followed by esterification of their hydroxy groups with methacryloyl chloride. The monomers, 4-(methacryloyloxy)chalcone derivatives, have been polymerized by a free radical technique. Copolymers containing the chalcone groups with different ratios of p-nitrophenylmethacrylate as photosensitizer group have also been prepared. The photosensitivities of the polymeric chalcone derivatives were investigated through their photochemical reaction on exposure to UV light, and by measuring the changes in their UV spectra before and after irradiation. The results obtained from the disappearance rates of the C?C bonds indicate that the photoreactivities of the polymers are largely affected by the position of the substituent in the phenyl ring of the chalcone, the photosensitizer group ratio, and the irradiation time.     

Synthesis,EGFR-TK inhibition and anticancer activity of new quinoxaline derivatives

Abstract

Ethyl 4-substituted-3-oxo-quinoxaline-2-carboxylates 3–5 were obtained via alkylation of ethyl 3-oxo-3,4-dihydroquinoxaline-2-carboxylate (1). Compound 1 was heterocyclized using hydrazines, ethylenediamine, and ethanolamine to give pyrazoloquinoxalines 6, 7, diazepinoquinoxaline 8, and oxazepinoquinoxaline 10. The quinoxaline-2-carboxamides 9, 11, 12 were prepared via condensation of compound 1 with different amines. Compound 1 was thiated using Lawesson’s reagent affording quinoxaline-3-thione 13, in fair yield. In addition, the reaction of 4-methyl-3-oxoquinoxaline 3 with some binucleophiles led to a series of new oxoquinoxaline derivatives 14–18. The molecular structure of compounds 1, 3, and 9 was confirmed by X-ray crystallography.

The anti-proliferative activity showed that among all the tested compounds, compounds 3, (IC₅₀ 2.51?±?3.0, 4.22?±?1.6 and 2.27?±?1.9?µM), 11 (IC₅₀ 1.32?±?2.61, 1.41?±?1.23 and 1.18?±?1.91?µM) and 17 (IC₅₀ 1.72?±?1.32, 1.85?±?0.94 and 1.92?±?4.83?µM) showed noteworthy anti-proliferative effects against the three cancer cell lines, HCT116, HePG2 and MCF7, respectively, compared to the reference drugs doxorubicin (IC₅₀ 1.41?±?0.58, 0.90?±?0.62 and 1.01?±?3.02?µM) and erlotinib (IC₅₀ 1.63?±?0.81, 1.57?±?0.62 and 1.49?±?0.54?µM). Compounds 3 (0.899?nM), 11 (0.508?nM) and 17 (0.807) showed strong EGFR inhibitory activity compared to Erlotinib (0.439?nM) and these results are in agreement with the docking study. These results suggest that compounds could probably be promising anticancer agents with EGFR inhibitory activity.     

Copper(II) mediated anion dependent formation of Schiff base complexes

A tetranuclear mixed ligand copper(II) complex of a pyrazole containing Schiff base and a hydroxyhexahydropyrimidylpyrazole and copper(II) and nickel(II) complexes of the Schiff base having N-donor atoms have been investigated. A 2 equiv amount of 5-methyl-3-formylpyrazole (MPA) and 2 equiv of 1,3-diamino-2-propanol (1,3-DAP) on reaction with 1 equiv of copper(II) nitrate produce an unusual tetranuclear mixed ligand complex [Cu4(L1)2(L2)2(NO3)2] (1), where H2L1 = 1,3-bis(5-methyl-3-formylpyrazolylmethinimino)propane-2-ol and HL2 = 5-methyl-3-(5-hydroxyhexahydro-2-pyrimidyl)pyrazole. In contrast, a similar reaction with nickel(II) nitrate leads to the formation of a hygroscopic intractable material. On the other hand, the reaction involving 2 equiv of MPA and 1 equiv each of 1,3-DAP and various copper(II) salts gives rise to two types of products, viz. [Cu(T3-porphyrinogen)(H2O)]X2 (X = ClO4, NO3, BF4 (2)) (T3-porphyrinogen = 1,6,11,16-tetraza-5,10,15,20-tetrahydroxy-2,7,12,17-tetramethylporphyrinogen) and [Cu(H2L1)X]X x H2O (X = Cl (3), Br (4)). The same reaction carried out with nickel(II) salts also produces two types of compounds [Ni(H2L1)(H2O)2]X2 [X = ClO4 (5), NO3 (6), BF4 (7)] and [Ni(H2L1)X2] x H2O [X = Cl (8), Br (9)]. Among the above species 1, 3, and 5 are crystallographically characterized. In 1, all four copper atoms are in distorted square pyramidal geometry with N4O chromophore around two terminal copper atoms and N5 chromophore around two inner copper atoms. In 3, the copper atom is also in distorted square pyramidal geometry with N4Cl chromophore. The nickel atom in 5 is in a distorted octahedral geometry with N4O2 chromophore, where the metal atom is slightly pulled toward one of the axial coordinated water molecules. Variable-temperature (300 to 2 K) magnetic susceptibility measurements have been carried out for complex 1. The separations between the metal centers, viz., Cu(1)...Cu(2), Cu(2)...Cu(2)A, and Cu(2)A...Cu(1)A are 3.858, 3.89, and 3.858 A, respectively. The overall magnetic behavior is consistent with strong antiferromagnetic interactions between the spin centers. The exchange coupling constants between Cu(1)...Cu(2) and Cu(2)...Cu(2A) centers have turned out to be -305.3 and -400.7 cm(-1), respectively, resulting in a S = 1/2 ground state. The complexes are further characterized by UV-vis, IR, electron paramagnetic resonance, and electrochemical studies.