Copper(II) complexes with the N,N,O-tridentate ligand 6-amino-5-formyl-1,3-dimethyluracilato-(N6)-benzoylhydrazone: synthesis, spectral and XRD studies

From reactions between different Cu(II) salts and the Schiff base 6-amino-5-formyl-1,3-dimethyluracil-benzoylhydrazone (H₂BEZDO) in alcohol, six new copper complexes with simplified formulas [Cu(HBEZDO)(H₂O)(MeOH)]NO₃ (1), [CuCl(HBEZDO)(DMF)] (2), [CuBr(HBEZDO)]·2H₂O (3), CuBr(HBEZDO) (4), Cu(ClO₄)(HBEZDO)·H₂O (5), and Cu(SO₄)_1/2(HBEZDO)·1H₂O (6) were isolated. The structures of compounds 1, 2 and 3 have been established by means of XRD diffraction methods. In the three compounds, the Schiff base acts as a tridentate monodeprotonated ligand through the N(6), N(51) and O(52) atoms, making two five- and six-membered chelate rings. In the structure of 1 and 2, the solvent molecules are coordinated giving square-based pyramidal environments, with the basal plane completed by a MeOH (1) or Cl (2) and the apical positions occupied by the oxygen atom of a water (1) or a DMF molecule (2). The molecular unit of the complex [CuBr(HBEZDO)]·2H₂O (3) is defined by a square-plane containing the three donor atoms of the organic ligand and a bromide ligand (Cu–Br 2.384 Å), but there is a stronger tetragonally elongated pyramidal geometry around the metal, the apical position of the polyhedron being occupied by a weakly bound-to-copper bromine atom (3.086 Å) of a neighbouring molecule. This fact gives the appearance of an apparent dimer with very asymmetric bromine bridges, in which there are no exchange interactions between metal centres. Also, infrared, magnetic and EPR data of the isolated complexes are reported.     

A common method for the determination of several calcium channel blockers using an HPLC system with ultraviolet detection

We report a common HPLC method for the single or simultaneous determination of four calcium channel blockers (CCB), namely diltiazem (DTZ), verapamil (VER), nifedipine (NIF) and nitrendipine (NIT) and their active metabolites demetildiltiazem and deacetildiltiazem (MA and M1), norverapamil (NOR), and dehydronifedipine (DHN). DHN was first synthesised in our laboratory and different pH values of the mobil phase were subsequently prepared and tested for chromatographic separation. The detection system and the environmental light conditions were optimised. The best separations of all analytes were obtained using a C₁₈ column and a mobile phase of methanol, 0.04 M ammonium acetate, acetonitrile and triethylamine (2:2:1:0.04 v/v). Quantitation was performed using imipramine (IMI) as the internal standard. For DTZ and its metabolites (M1 and MA), the wavelength chosen was 237 nm; for VER and its metabolite NOR, it was 210 nm; and, finally for NIF and its metabolite DHN and NIT it was 216 nm. When a simultaneous analysis was carried out the wavelength was of 230 nm. The optimum pH were 7.90 and 7.10 when the separation of NIT and DTZ or VER and NIF were carried out, respectively, and 7.90 when a simultaneous separation was carried out. The detection limit of the assay was less than 8 ng ml⁻¹ for all compounds, with coefficients of variation less than 7% (for inter- and intra-day) over the concentration range of 1–1000 ng ml⁻¹. The retention times were less than 11 min. When NIF or NIT were studied, it was necessary to use a sodium vapour lamp in order to avoid the photodegradation which takes place under daylight conditions.     

Relative stability of the2 A 1g and2 E g states of the C2H 6 + ion

Anab initio study of the relative stability for the states² A _1g and² E _g of C₂H ₆ ⁺ has been carried out. The results of the Open Shell Restricted Hartree-Fock calculations lead to assign the² A _{1 g} as the ground state of the molecule in agreement with previous SCF calculations.The correlation energy associated to both states has been calculated within the correlation hole model and the results, contrary to those obtained from Configuration Interaction calculations, do not alter qualitatively the conclusions from SCF.     

The mass spectra of [17-13C]phyllocladene and [3-13C]methylenecholestane—III

The mass spectra of [17-¹³C]phyllocladene and [3-¹³C]methylenecholestane have been examined. It is shown that there are some rearrangements at 70 e V as in the case of [17-¹³C]kaurene. However, no extensive randomization is evident at the molecular ion level. The results are interesting because very little is known about ¹³C randomization in polycyclic aliphatic hydrocarbons. The percentage retention of label was calculated for each ion.     

Reactions of dimethyldivinylsilane,dimethyldivinyltin and allyltrimethyltin with diethylene (tertiary) phosphine)platinum complexes

The compounds [Pt(C₂H₄)₂(PR₃)] [PR₃ = P-tBu₂Me, P(C₆H₁₁)₃, PPh₃] react dimethyldivinylsilane or dimethyldivinyltin to give chelate complexes [Pt{(CH₂CH)₂MMe₂} (PR₃)] (M = Si or Sn). allyltrimethyltin reacts with various diethylene (tertiary phosphine)platinum compounds with cleavage of the allyl group to afford complexes [Pt(SnMe₃)(η³-C₃H₅)(PR₂)]. The NMR spectra (¹³C, ¹H and ³¹P) of the new compounds have been recorded, and the data are discussed in terms of the structures proposed.     

Synthesis and reactivity of N-[α-acetoxy)-4-pyridylmethyl]-3,5-dimethylbenzamide

The synthesis of N-[(α-acetoxy)-4-pyridylmethyl]-3,5-dimethylbenzamide (4) and its reactivity are described. Since the acetoxy is a good leaving group, 4 gives S_N processes easily.     

Chemistry of dithiocarbamate derivatives of amino acids. Part II. Complexes of nickel(II) with derivatives of branched and cyclic amino acids

Summary Barium salts of the dithiocarbamate derivates of the amino acids: DL-valine, L-valine, DL-leucine, DL-isoleucine and L-proline have been synthesized. The anions have been used to obtain the corresponding nickel(II) complexes in acid form. The complexes are diamagnetic, and coordination takes place in a near-square planar geometry around the nickel(II) ion through the sulphur atoms of the dithiocarbamate moiety, the structure being confirmed by i.r.,¹H n.m.r., u.v.-vis spectros copies and by chemical analysis.No significant difference has been found between the physicochemical properties (i.r. and 'H n.m.r. spectra and magnetic properties) of the complexes prepared from the dithiocarbamate derivatives of DL- and L-valine, but d-d bands in the u.v.-vis spectra show a slight different intensity.     

Reaction of N-(4-pyridylmethyl)benzamide N-oxides with ethyl cyanoacetate in the presence of acetic anhydride

Reaction of N-(4-pyridylmethyl)benzamide N-oxides 2a-f with ethyl cyanoacetate in the presence of acetic anhydride yield dimerization compounds 3a-f and (E)-ethyl 2-cyano-3-(4-pyridyl)-3(benzoylamino)acrylates 4a-f , which react with hydrazine to give 4-cyano-3-(4-pyridyl)-3-pyrazolin-5-one 9 and the corresponding benzamides 10a-f .     

Host–Guest Chemistry Within Cellulose Nanocrystal Gel Receptors

Cellulose nanocrystals (CNCs) spontaneously assemble into gels when mixed with a polyionic organic or inorganic salt. Here, we have used this ion-induced gelation strategy to create functional CNC gels with a rigid tetracationic macrocycle, cyclobis(paraquat-p-phenylene) ( CBPQT ⁴⁺). Addition of [ CBPQT ]Cl₄ to CNCs causes gelation and embeds an active host inside the material. The fabricated CNC gels can reversibly absorb guest molecules from solution then undergo molecular recognition processes that create colorful host–guest complexes. These materials have been implemented in gel chromatography (for guest exchange and separation), and as elements to encode 2- and 3-dimensional patterns. We anticipate that this concept might be extended to design a set of responsive and selective gel-like materials functioning as, for instance, water-pollutant scavengers, substrates for chiral separations, or molecular flasks.     

Synthesis and spectral properties of new complexes between glycine and titanium(III), vanadium(III), chromium(III), iron(III), cobalt(II), nickel(II) and copper(II)

Summary Complexes of formula [MCl₃(glyH)₃] (M=Ti, V and Fe) [CrCl₃(glyH)₂H₂O], [MCl₂(glyH)₂(H₂O)₂] (M=Co and Cu) and [NiCl₂(glyH)₃H₂O] have been prepared and characterized by potentiometric curves, chemical analysis, magnetic properties, i.r. and electronic spectral data.