Synthesis and Stereochemistry of Some New Spiro-1,3-perhydrooxazines

Summary.  The synthesis and the stereochemistry of new spiro-1,3-perhydrooxazines are reported. The stereoisomerism of these compounds is discussed considering the data of conformational analysis, the helical chirality of the spiro[5.5]undecane skeleton, and the triligand virtual chiral center belonging to the 1,3-perhydrooxazine ring. Received February 21, 2000. Accepted (revised) April 18, 2000     

Aminophylline: thermal characterization and its inhibitory properties for the carbon steel corrosion in acidic environment

Aminophylline (AMF) was studied as corrosion inhibitor for carbon steel in 1.0 mol L^?1 HCl solution using electrochemical measurements associated with UV–Vis spectrophotometry and optical microscopy. Simultaneous thermogravimetry/derivative thermogravimetry and differential scanning calorimetry analysis was performed in order to determine the temperature range in which AMF is an effective inhibitor, without the decomposition risk that could change the inhibition mechanism. Thermal behaviour restricts AMF application as corrosion inhibitor for carbon steel in 1.0 mol L^?1 HCl solution at temperatures ≤45 °C where there are no significant modifications of the adsorption mechanism. According to the results of electrochemical measurements, in association with UV–Vis spectrophotometry and optical microscopy techniques, AMF is a mixed-type inhibitor for carbon steel corrosion in 1.0 mol L^?1 HCl solution, simultaneously suppressing the anodic and cathodic processes and acting via spontaneous physisorption on the metal surfaces.     

PalladiumII and platinumII complexes with heteroditopic 10-(aryl)phenoxarsine (aryl = 2-C6H4OR, R = H, Me, Pr(i)) ligands: solvent-oriented crystallization of cis isomers

The synthesis and characterization of 10-(o-alkoxyphenyl)phenoxarsines 2-ROC6H4As(C6H4)2O (R = H, Me, and Pri, As(C6H4)2O = phenoxarsine) and their platinum(II) and palladium(II) complexes cis-[PtCl2{2-PriOC6H4As(C6H4)2O-kappaAs}2] (1), trans-[PdCl2{2-PriOC6H4As(C6H4)2O-kappaAs}2] (2), cis-[PtCl2{2-HOC6H4As(C6H4)2O-kappaAs}2] (3), cis-[PdCl2{2-HOC6H4As(C6H4)2O-kappaAs}2] (4), cis-[PtI2{2-MeOC6H4As(C6H4)2O-kappaAs}2] (5), and trans-[PdCl2{2-MeOC6H4As(C6H4)2O-kappaAs}2] (6) are reported. The chelate complex cis-[Pt{2-OC6H4As(C6H4)2O-kappaAs,O}2] (7) is also described. The molecular structures of 1-4 and 7 were determined. The short As...O intramolecular interaction found in complexes 1-4 in the solid state was also verified by calculations at the B3LYP/LANL2DZ level for complex 2 and for 10-(o-isopropoxyphenyl)phenoxarsine in the gas phase, and this suggests that the interaction is a characteristic of the ligand rather than a packing effect. Calculations at the B3LYP/LANL2DZ and Oniom(B3LYP/LANL2DZ:uff) levels for complexes 1-4 showed that the solvent plays a crucial role in the crystallization (through geometry constraints) of the kinetically stable cis isomers.     

M(III)(bpym)(CN)(4)](-): a suitable building block to design ferrimagnetic cyano-bridged heterobimetallic chains (M = Fe, Cr; bpym = 2,2'-bypyrimidine)

Two cyano-bridged M(III)Mn(III) [M = Fe () and Cr ()] ferrimagnetic chains are reported; exhibits metamagnetism with two critical fields of 1250 G and 2.0 T which correspond to the overcoming by the applied dc field of the inter- and intrachain magnetic interactions, respectively.     

Designing thermotropic liquid crystalline polyazomethines based on fluorene and/or oxadiazole chromophores

The main objective of this paper was to synthesize luminescent thermotropic liquid crystalline polyazomethines containing chromophoric mesogen, which design has been addressed to optoelectronic materials. The investigation of the thermotropic behavior by three complementary methods of analyses, i.e. polarized optical microscopy, differential scanning calorimetry and wide angle X-ray diffraction, indicated a nematic mesophase for the polymers containing oxadiazole units, either alternating or random ones. A mesomorphic state maintaining the degree of order of the semicrystalline state while being viscous fluid was evidenced too. The photoluminescence spectra recorded for both polymer solutions and films exhibited a blue light emission. These results point to the possibility of obtaining monodomain or multidomain ordered thin films without grain boundaries showing good mechanical and luminescent properties.     

N,N′ and N,O chelated phosphenium cations containing aminotroponiminate or aminotroponate units

New phosphenium cations stabilized by bidentate monoanionic N-isopropyl-2-(isopropylamino)troponiminate or 2-(isopropylamino)troponate units have been synthesized. These complexes were characterized by ³¹P, ¹H and ¹³C NMR spectroscopies, and the molecular structures were determined by X-ray crystallography. These data indicate the formation of N,N′- and N,O-chelate derivatives having three-coordinate phosphorous atoms included in planar heterobicycles. Moreover, computational studies support the presence of high delocalization of the positive charge into the π-conjugated carbon backbone and of the high-lying phosphorus lone-pair orbital.     

Interaction of the low-molecular weight salts with cationic polyelectrolytes

The interaction of several mono-, di-, and trivalent anions with cationic polyelectrolytes having different contents in N,N-dimethyl-2-hydroxypropylen ammonium chloride units (polymer A) or tertiary amine N-atoms and PEG (polymer PEGA) in the main chain was studied by viscosimetric and conductometric measurements. Both methods have shown a stronger interaction for tri- and bi- than for univalent counterions. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2571–2581, 1997     

Synthesis,structural investigations,and DFT calculations on novel 3-(1,3-dioxan-2-yl)-10-methyl-10H-phenothiazine derivatives with fluorescence properties

Comparison studies on the acetalization of 10-methyl-10H-phenothiazine-carbaldehyde with 1,3-propanediol, or 2-substituted-1,3-propanediols, under conventional versus microwave assisted conditions and standard organic solvents versus water, were performed as an attempt toward more environmentally benign synthetic methods. New 3-(1,3-dioxan-2-yl)-10-methyl-10H-phenothiazine derivatives were obtained in high yields by azeotropic distillation of water and in moderate yields by microwave assisted synthesis in different solvents, including water under superheated conditions. The solvent influence upon stabilizing the key intermediates involved in the acetalization mechanism was assumed based on DFT calculations, which indicated a favorable enthalpy profile in water solvent. Structural investigations of the new compounds based on spectroscopic methods (NMR, FT-IR, UV–vis, and MS), were completed with molecular mechanics and semi-empirical DFT calculations, which supported an anancomeric chair conformation of the 1,3-dioxane ring with the phenothiazine substituent in the equatorial position and possible free rotation about the single bond linking the two heterocyclic units. The new compounds display daylight fluorescence characterized by remarkably large Stokes shifts determined by LE spectroscopy.