Synthesis,characterization and antimicrobial studies of mixed ligand silver(I) complexes of thioureas and triphenylphosphine; crystal structure of {[Ag(PPh3)(thiourea)(NO3)]2·[Ag(PPh3)(thiourea)]2(NO3)2}

Mixed ligand silver(I) complexes of triphenylphosphine and thioureas (thiourea (Tu), N-methylthiourea (Metu), N,N′-dimethylthiourea (Dmtu) and N,N′-diethylthiourea (Detu)) with the general formulae, [(Ph₃P)₂Ag(thione)]NO₃ and [(Ph₃P)Ag(thione)₂]NO₃, have been prepared and characterized by elemental analysis, IR and NMR (¹H, ¹³C and ³¹P) spectroscopic methods. The crystal structure of one of them has been determined by X-ray crystallography. The spectral data of the complexes are consistent with sulfur coordination of the thiones to silver(I). The single crystal X-ray structure of complex 1, {[Ag(PPh₃)(thiourea)(NO₃)]₂·[Ag(PPh₃)(thiourea)]₂(NO₃)₂}, shows that the complex consists of two independent centrosymmetric binuclear units, each having the silver atoms coordinated to one PPh₃ and two bridging thiourea molecules. In one of the independent units the silver atom is additionally bound to a nitrate ion, leading to a tetrahedral geometry, while in the other unit the silver atom adopts a trigonal planar environment. Antimicrobial activities of the complexes were evaluated by their minimum inhibitory concentration and the results showed that the complexes show a wide range of activity against two gram-negative bacteria (Escherichiacoli, Pseudomonasaeruginosa) and molds (Aspergillusniger, Penicilliumcitrinum), while the activities were poor against yeasts (Candidaalbicans, Saccharomycescerevisiae). However, the title complex did not show activity against any tested microorganism.     

Synthesis and structural characterization of cadmium(II) complexes of tetramethylthiourea (Tmtu); X-ray structure of [Cd(Tmtu)2Cl2]

The spectral characterization of cadmium(II) complexes of the general formula [Cd(Tmtu)₂X₂] (Tmtu = tetramethylthiourea, X = Cl^?, Br^?, I^?, and SCN^?) as well as the X-ray structure of one of them, [Cd(Tmtu)₂Cl₂] (I) is described. In (I), the cadmium atom lies on a twofold rotation axis and has a distorted tetrahedral coordination environment defined by two S atoms of telramelhylthioures (Tmtu) ligands and two chloride ions. The crystal structure is stabilized by non-classical intramolecular C-H?N and C-H?S hydrogen bonding interactions involving the methyl H and sulfur or nitrogen atoms. The spectroscopic data were discussed in terms of the nature of bonding.     

Non-local symmetries of first-order equations

It is shown how one can transform scalar first-order ordinarydifferential equations which admit non-local symmetries of theexponential type to integrable equations admitting canonicalexponential non-local symmetries. As examples we invoke theAbel equation of the second kind, the Riccati equation and naturalgeneralizations of these. Moreover, our method describes howa double reduction of order for a second-order ordinary differentialequation which admits a two-dimensional Lie algebra of generatorsof point symmetries can be affected if the second-order equationis first reduced in order once by a symmetry which does notspan an ideal of the two-dimensional Lie algebra.     

Electro-elastic interactions and second order anisotropic constitutive equations

Piezoelectricity is usually expressed as an interaction between mechanical and electrical variables. The physics involved is hence governed by a coupling between Maxwell's equations of electromagnetism and the equations of elasticity. Such a coupling takes us through the piezoelectric constitutive relations. In this work, the second order anisotropic constitutive equations are treated, and in particular, the number of independent material constants is computed for all the 32 crystallographic classes.Paper presented, in reduced version, at the 12th Italian National Congress of Theoretical and Applied Mechanics (AIMETA '95), October 1995, Naples, Italy.     

Transition to Chaos in the Floating Half Zone Convection

The transition process from steady convection to chaos is experimentally studied in thermocapillary convections of floating half zone. The onset of temperature oscillations in the liquid bridge of floating half zone and further transitions of the temporal convective behaviour are detected by measuring the temperature in the liquid bridge. The fast Fourier transform reveals the frequency and amplitude characteristics of the flow transition. The experimental results indicate the existence of a sequence of period-doubling bifurcations that culminate in chaos. The measured Feigenbaum numbers are δ2 =4.69 and δ4 = 4.6, which are comparable with the theoretical asymptotic value δ=4.669.     

Synthesis,characterization, and miRNA-mediated PI3K suppressing activity of novel cisplatin-derived complexes of selenones

New therapeutic options are crucially for most cancers, particularly those with poor clinical outcomes. Five new derivatives of cisplatin-containing selenone ligands with the general formula, cis-[Pt(NH₃)₂(Selenone)₂](NO₃)₂ (1–5) were synthesized and characterized using elemental analysis, Infrared, and nuclear magnetic resonance (¹H, ¹³C & ⁷⁷Se) spectroscopy. Spectroscopic and computational data supported the coordination of selenones to platinum(II). The structures of the complexes were predicted using density functional theory calculations. Molecular docking studies were carried out using the AutoDock Tools docking program. The in vitro cytotoxicity of these complexes and cisplatin against three human cancer cell lines, HeLa, A549, and HCT116 was investigated using the MTT assay. The best candidate complex, complex 3, was subjected to mechanistic assessments, including miRNA profiling, PI3K deactivation, and induction of apoptosis. Docking studies showed that all the newly synthesized platinum(II) complexes interacted with the minor DNA groove. The synthesized complexes showed promising cytotoxic effects against the tested cell lines. Complex 3 modulated the miRNA expression signature in A549 cells. Pathway enrichment analyses of differentially expressed miRNA gene targets identified the PI3K/AKT signaling pathway as a promising target. Complex 3 inhibited PI3K activity and induced apoptosis. Collectively, our study identified promising new platinum(II) derivatives such as complex 3, paving the way for future in vitro and in vivo validations and safety studies.