Hassan A. Mohamed

Spectroscopic, thermal and X-ray crystal structure studies of some bis-(pyrazine-2-carboxylato) nickel(II) complexes

Three nickel(II) complexes [Ni(PC)2(H2O)2], 1, [Ni(PC)2(TU)2], 2 and [Ni(PC)2(ABI)2]· 2(H2O), 3, PC = pyrazine-2-carboxylate, TU = thiourea and ABI = 2-aminobenzimidazole, were synthesized and characterized by elemental analysis, IR spectroscopy and thermal analysis. The complexes were also investigated by single crystal X-ray diffraction analysis. Structures of the monomeric complexes showed nickel(II) chelated to two PC ions from an oxygen atom of carboxylate ion and the adjacent hetero nitrogen atom. The three complexes were crystallized in a monoclinic system with P2 1 /c space group for 1, while 2 and 3 had C2/c space groups. The structure of 1 showed two coordinated water molecules occupying the trans positions of a slightly elongated octahedron. The structure of 2 consisted of two PC ions and two thiourea molecules in trans positions. The structure of 3 was different and showed a highly distorted octahedron with two ABI molecules chelated to the nickel ion in cis positions through their hetero nitrogen atoms. Two water molecules of crystallisation were shown in the structure of 3.

Spectroscopic and thermal studies of some Palladium complexes with certain Heterocyclic Nitrogen ligands

Mono- and binuclear palladium complexes were isolated from reactions of [PdCl4]2− with heterocyclic nitrogen donor ligands depending on the type of ligand. Bidentate ligands L–L, where L–L = 2-(2′-pyridyl)-benzimidazole (PBI), 2-pyrazinecarboxylic acid (PC) and 2-pyrazinecarboxamide (PCA) gave the monosubstituted [Pd(L-L)Cl2] complex. Binuclear palladium complexes [Pd(L)Cl2]2 were obtained from reactions with the monodentate ligands 2-aminothiazole (AT) or 2-aminobenzimidazole (ABI). Elemental analyses and spectroscopic studies of the reported complexes allowed structures to be proposed. The thermal properties of the complexes were also investigated by thermogravimetric techniques.

Novel chromium and molybdenum complexes of a dimerized isonicotinic acid hydrazide

Sunlight irradiation of [M(CO)6], M = Cr and Mo with isonicotinic acid hydrazide (inh) was investigated. The photochemical process resulted in dimerization of inh with elimination of a hydrazine molecule to give N′-isonicotinoylisonicotino hydrazide (ininh). Two complexes with molecular formulas [MO2(ininh)] were isolated and characterized by elemental analysis, infrared, mass and 1H NMR spectroscopy. The UV-vis spectra of the complexes in DMSO showed visible bands due to ligand-to-metal charge transfer. Thermal properties of the complexes were investigated by TG thermogravimetry.

Structural studies of some chromium and molybdenum complexes of 5,6-benzoquinoline

Interaction of 5,6-benzoquinoline (BQ) with [Cr(CO)6] in air resulted in the formation of [O2(BQ)Cr(μ-O)2Cr(BQ)O2] (1). Reaction of BQ with [Mo(CO)6] depends on the reaction conditions. In air for a short time, it gave [(BQ)O(CO)Mo(μ-O)2MoO(CO)(BQ)] (2). Prolonged heating in air gave the oxo complex [O2Mo(μ-o)2MoO2(BQ)] (3). Under reduced pressure, the reaction of BQ with [Mo(CO)6] resulted in the formation of [Mo(CO)5(BQ)] (4). The complexes were characterized by elemental analysis, IR, and 1H NMR spectroscopy. The thermal properties of the complexes were investigated by thermogravimetric techniques.

Fluorescence properties of some coumarin dyes and their analytical implication

Fluorescence characteristics of two substituted coumarin dyes have been investigated. The effect of solvent polarity and viscosity on the fluorescence properties of these dyes was examined. It was found that the fluorescence quantum yield (φf) is a steep function of the viscosity. The dependence of φf on viscosity is successfully explained on the basis of the free volume theory of viscosity. Moreover, fluorescence depolarization measurements in media of different viscosities assist in the establishment of an analytical method for microviscosity determination in the interior of some micellar assemblies.

Effect of Dexmedetomidine Infusion on Sublingual Microcirculation in Patients Undergoing On-Pump Coronary Artery Bypass Graft Surgery: A Prospective Randomized Trial

OBJECTIVES Cardiac surgery is characterized by attenuation of microcirculatory perfusion. Dexmedetomidine has been proved to attenuate the microcirculatory derangements evoked by experimental sepsis. The authors investigated the effects of dexmedetomidine infusion on sublingual microcirculation in patients undergoing on-pump coronary artery bypass graft (CABG) surgery. DESIGN Prospective, randomized blinded study. SETTINGS Tertiary university hospital. PARTICIPANTS A total of 70 adults undergoing elective on-pump CABG surgery. INTERVENTION After a standard general anesthesia, participants were allocated randomly to receive either propofol continuous intravenous infusion, 50 to 70 µg/kg/min, or propofol infusion, 50 to 70 µg/kg/min plus dexmedetomidine infusion, 0.5 µg/kg/h, during cardiopulmonary bypass. Microcirculation was studied with side-stream dark field imaging at 3 times: immediately before starting bypass (T0), 30 minutes after initiation of bypass (T1), and 30 minutes after weaning from bypass (T2). MEASUREMENTS AND MAIN RESULTS Microvascular flow index was significantly higher in the dexmedetomidine group at T2 compared to the control group (2.20 ± 0.29 and 1.47 ± 0.30, respectively; p = 0.001). The perfused vessel density was significantly higher in the dexmedetomidine group at T2 compared to the control group (6.1 [3-8.9] mm/mm² and 3.3 [2.2-4.3] mm/mm², respectively; p = 0.01). The total vascular density was significantly higher in the dexmedetomidine group compared to the control group at T1 and T2 (9.9 [7.8-12.6] mm/mm² v 7.4 [6.1-9] mm/mm², p = 0.005; and 9.27 ± 2.27 mm/mm² v 7.24 ± 1.66 mm/mm², p = 0.003, respectively). CONCLUSION This trial demonstrated that dexmedetomidine infusion improved sublingual microcirculation indices in patients undergoing on-pump CABG surgery.

Chelation behaviour of lanthanons witho-arsonodibenzoylmethanephenylhydrazone

SummaryThe chelate formation reaction of La(III), Pr(III), Nd(III), Gd(III), Ho(III), and Er(III) witho-arsonodibenzoylmethanephenylhydrazone has been investigated potentiometrically and conductometrically in 40% (v/v) aqueous ethanol, ionic strength 0.1M. The order of stability constants was found to be La < Pr < Nd > Gd < Ho < Er. The chelates formed have 1:1 and 1:2 stoichiometries (M3+:L). The complexes have been isolated in solid state and have been characterized on the basis of elemental analysis and IR data. Coordination occurs through -NH of the hydrazo and-OH of the arsonic groups.ZusammenfassungDie Reaktion der Chelatbildung von La(III), Pr(III), Nd(III), Gd(III), Ho(III) und Er(III) mito-Arsonodibenzoylmethanphenylhydrazon wurde potentiometrisch und konduktometrisch in 40% (v/v) wäßrigem Ethanol bei einer Ionenstärke von 0.1M untersucht. Die Reihung der Stabilitätskonstanten war La < Pr < Nd > Gd < Ho < Er. Die Chelate haben 1:1 und 1:2 Stöchiometrien (M3+:L). Die Komplexe wurden im Festzustand isoliert und mittels Elementaranalyse und IR-Spektroskopie charakterisiert. Die Koordinierung erfolgt über -NH der Hydrazo- und -OH der Arsongruppe.