Further studies on the stereochemistry of sparteine, its isomers and derivatives : Part. I. Synthesis, structure and properties of 16,17-endo-methylene-lupaniumm perchlorate, 17-β-methyllupanine and 17-β-methylsparteine

The reduction of the product (V) obtained from the reaction of δ^16,17-dehydro- lupaninium perchlorate with diazomethane leads to 17-β-methyllupanine (III) (NaBH₄- reduction) or to 17-β-methylsparteine (X) (LiAlH₄-reduction). The structures of III and X were determined by spectroscopic methods (NMR and IR) and further proved by chemical methods. The β-methyl group at C-17 has a pronounced effect on the basicity of III and X. The basicity of in is higher than that of its parent lupanine by about 1.5 pK^*_MCSunits which can be explained by additional stabilization of the C/D boat-chair conformation in III and better solvation conditions than in lupanine. The same effect leads to a decrease of the δpK^*_MCS-value of the diamine X with reference to that of sparteine by ca. 2.6 units. The methyl group in X stabilizes the C/D boat-chair conformation and hinders the formation of an intramolecular hydrogen bond in monoprotonated X, consequently the addition of a second proton is favoured and it is assumed that the diprotonated cations of X and sparteine have different conformations. The reaction intermediate 16,17-endo-methylenelupaninium perchlorate (V) was isolated and its structure was determined.     

Synthesis,spectroscopic studies,and crystal structure of 2,6-diacetylpyridinediphenylhydrazone perchlorate and its complexing ability toward the lanthanides

2,6-diacetylpyridinediphenylhydrazone perchlorate was prepared and characterized by spectroscopic (IR, ESI–MS, UV–Vis, ¹H NMR) and analytical data and its crystal structure was determined by single X-ray analysis. The lanthanum(III), praseodymium(III), and neodymium(III) perchlorate complexes of 2,6-diacetylpyridinediphenylhydrazone were prepared in a direct reaction of the ligand with appropriate metal perchlorates. The spectroscopic and analytical data indicate 1:2 metal to ligand stoichiometry. In all the complexes the hydrazones act as monodeprotonated terdentate NNN donor chelators. The same lanthanum(III) complex was also obtained in a one-step condensation reaction between 2,6-diacetylpyridine and phenylhydrazine in the presence of lanthanum(III) perchlorate.     

Fluorescent derivatives of thromboxane B(2): Synthesis, spectroscopic and immunologic properties

Thromboxane B(2) has been labeled by four fluorescent probes structurally related to coumarin (4-bromomethyl-7-methoxycoumarin, 7-[(chlorocarbonyl) methoxy]-4-methylcoumarin, 4-luminarin) or anthracen (panacyl bromide). The purity of the derivatives determined by liquid chromatography was over 90%. The extinction coefficient, Stokes' shift, quantum yield, life-time and the anisotropy of the emitted fluorescence were determined. Immunorecognition of thromboxane B(2) derivatives was checked by competition immunoassays. Among the derivatives tested, that obtained with 4-luminarin has a suitable Stokes' shift (95 nm), a quantum yield of 0.46, a single value of excited state life-time (9.3 nsec), a well-preserved immunorecognition and a good chemical stability. Preliminary results in competition experiments showed variations in fluorescence anisotropy correlated to thromboxane B(2) concentration.     

Purines. XIV. Synthesis and properties of 8-nitroxanthine and its N-methyl derivatives

Xanthine ( 1 ) and its N-methyl derivatives 2–16 have been nitrated to the corresponding 8-nitro derivatives 17–32 under different reaction conditions. Nitration in glacial acetic acid with nitric acid works well with the N-7 unsubstituted and some of the 9-methylxanthines, respectively, whereas the 7-methylxanthine derivatives react best with nitronium tetrafluoroborate in sulfolane or glacial acetic acid. The 8-nitro group can be displaced nucleophilically to form 8-chloro-, 33, 34 , 8-ethoxy-, 35,36 , and uric acid derivatives 37–40 , respectively. The newly synthesized 8-nitroxanthines have been characterized by elemental analyses, pK-determinations and uv and ¹H-nmr spectra.     

Further studies on the chemistry and structure of n-oxides of sparteine and its derivatives—V: Synthesis and structure of 2-phenylsparteine-n16-oxide,a new case of “sponge” proton

The synthesis of 2-phenylsparteine-N₁₆-oxide (7) and its perchlorate salt (7-H⁺) was carried out. On the basis of spectral data, and by comparison with appropriate sparteine-N-oxides, the mechanism of formation and the structures of the two new compounds were proposed. It was found, the basicity of the new N-oxide is unexpectedly high and comparable to the basicity of quaternary ammonium hydroxides. The structure and the strength of intramolecular H-bond in 7-H⁺ makes 7 an excellent “catcher” proton or specific ”sponge” proton.     

Synthesis, spectroscopic properties and crystal structure determination of 2-(2-pyridin-4-yl-vinyl)-1H-benzimidazole derivatives

Substituted 2-(2-pyridin-4-yl-vinyl)-1H-benzimidazole derivatives 2, 3 and 6 were synthesized. 2-(2-Pyridin-4-yl-vinyl)-1H-benzimidazole 2 and 6-methyl-2-(2-pyridin-4-yl-vinyl)-1H-benzimidazole 3 were prepared by condensation reaction from 3-pyridin-4-yl-acrylic acid and corresponding 1,2-phenylenediamines in polyphosporic acid (PPA). 2,7,11-b-Triaza-benzo[c]fluorene 4 was prepared by photochemical dehydrocyclization reaction of ethanolic solution of 2-(2-pyridin-4-yl-vinyl)-1H-benzimidazole 2. 2-(2-Pyridin-4-yl-vinyl)-3H-benzimidazole-6-carbonitrile 6 was prepared by condensation reaction from 3-pyridin-4-yl-propenal and 4-cyano-1,2-phenylenediamine using p-benzoquinone as oxidants. The structure of novel benzimidazole derivatives has been studied by ¹H and ¹³C NMR, IR, MS, UV/Vis and fluorescence spectroscopy. The structure of 2-(2-pyridin-4-yl-vinyl)-1H-benzimidazole 2 was confirmed by X-ray single crystal structure analysis. The conformation of the molecule is E in regard to substituents position around vinyl double C=C bond. The non-planar molecules are mutually connected via the N–H···N and C–H···N type of intermolecular hydrogen bonds into infinite chains spreading along y axis.     

Synthesis,structure, and spectral fluorescence properties of 1,4-di(5-phenyl-2-oxazolyl)benzene heteroanalogs

Novel organic luminophors belonging to the oxazole and oxadiazole classes of compounds have been synthesized, namely, thiophene and furan analogs of 1,4-di(5-phenyl-2-oxazolyl)benzene. The optical properties of these compunds have been studied both theoretically and experimentally. Their IR spectra have been measured and their UV absorption, fluorescence, and excitation spectra have been analyzed. Details of their electronic structure and their principal spectral fluorescence parameters have been calculated using the PPP method. Possible methods or pathways for improving the spectral fluorescence parameters of organic luminophors in these classes of compounds in the visible region of the spectrum have also been analyzed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1414–1419, October, 1989.     

Synthesis and spectroscopic properties of some thermochromic copper(II) complexes ofN(2-aminoethyl) heterocyclic derivatives

Summary Compounds of the type CuL₂X₂, where L =N(2-aminoethyl)piperazine [N(2-amet)pipz],N(2-aminoethyl)-pyrrolidine [N(2-amet)pyrr] andN(2-aminoethyl)morpholine [N(2-amet)morph] and X = BF ₄ ^– , ClO ₄ ^– and NO ₃ ^– , have been prepared and characterized by means of magnetic moments, e.s.r., electronic and i.r. spectra. Only forN(2-amet)pyrr and Cu[N(2-amet)morph]₂(NO₃)₂ complexes, do the electronic and i.r. spectra suggest polyanion coordination. In particular, as their electronic and i.r. spectra in the 293–393K range are temperature-dependent, it may be ascribed to the presence of a reversible continuous thermochromism arising from a temperature-dependent axial interaction between the anion and the CuN₄ plane, which diminishes as the temperature increases. In all the other complexes, the thermochromism may be associated with a geometry which is more planar forN(2-amet)morph than forN(2-amet)pipz derivatives.     

Spectroscopic studies of poly(vinyl chloride) and its deuterated derivatives

Poly(vinyl chloride) (PVC) and all its deuterated derivatives were prepared by variation of the polymerization method and polymerization temperature to study the structure of PVC and the mechanism of addition polymerization by infrared spectroscopy and high resolution NMR spectroscopy. The CH and CH₂ stretching modes of PVC were assigned completely from the infrared spectra of PVC-αd₁, PVC-β,βd₂ and PVC-d₃. The frequencies of the CCI stretching modes of the polymers depended not only on the substituents in the trans position to the Cl atom across both adjacent C? C bonds, but also on the atom attached to the C atom of the C? Cl bond. The frequency shifts were used to assign the CCl stretching modes of PVC-βd₁ and PVC-α,βd₂ and to study the opening of the double bond of VC in the addition polymerization. The differences of the chemical shifts of the α and β protons of PVC due to the tacticity were determined experimentally by PVC-β,βd₂ and PVC-αd₁ without using the spin-decoupling technique. With PVC-α,βd₂, the conception of the tetrad was required to interpret the four observed peaks whose intensities changed with the polymerization temperature and the trans–cis composition of the monomer used.     

Synthesis, spectroscopic and thermal studies of the copper(II) aspartame chloride complex

Aspartame adduct of copper(II) chloride Cu(Asp)₂Cl₂·2H₂O (Asp=aspartame) is synthesized and characterized by elemental analysis, FT IR, UV/vis, ESR spectroscopies, TG, DTG, DTA measurements and molecular mechanics calculations. Aqueous solution of the green solid absorbs strongly at 774 and 367 nm. According to the FT IR spectra, the aspartame moiety coordinates to the copper(II) ion via its carboxylate ends, whereas the ammonium terminal groups give rise to hydrogen bonding network with the water, the chloride ions or neighboring carboxylate groups. The results suggest tetragonally distorted octahedral environment of the copper ions.     

Complexation of cobalt(II) perchlorate with crown ethers. Synthesis,properties and structure of complexes of cobalt(II) perchlorate with 16-crown-5 and its lariat derivatives

Complexes of cobalt(II) perchlorate with 16-crown-5 (L¹) and its two lariat derivatives, 15,15-dimethyl-16-crown-5 (L²) and 15-(2,5-dioxahexyl)-15-methyl-16-crown-5 (L³), have been prepared and characterized. The crystal structure of [Co(L³)H₂O)](ClO₄)_{_2} has been determined by X-ray crystallography. The cobalt(II) ion is heptacoordinated with five crown ether oxygen atoms at the equatorial plane, a side arm oxygen atom and a water molecule at the apical position. The coordination polyhedron of cobalt is a distorted pentagonal bipyramid with the average Co-O(crown) distance of 2.20(2)Å.     

Synthesis,molecular geometry,spectroscopic studies and thermal properties of Co(II) complexes

Co(II) complexes (1‐4) were prepared and characterized by elemental analyses, infrared spectra, spectral studies, magnetic susceptibility measurements, X‐ray diffraction analysis and thermogravimetric analysis (TGA). The X‐ray diffraction patterns of Co(II) complexes were observed many peaks which indicate the polycrystalline nature. The thermodynamic parameters were calculated by using Coats–Redfern and Horowitz–Metzger methods. The bond length, bond angle and quantum chemical parameters of the Co(II) complexes were studied and discussed. The Co(II) complexes were tested against various Gram‐positive bacteria, Gram‐negative bacteria and fungi. It was found that the Co(II) complex (1) has more antifungal activity than miconazole (antifungal standard drug) against P. italicum at all concentration. The Co(II) complex ( 2 ) has more antibacterial activity than the penicillin against K. pneumoniae at all concentration. The interaction between Co(II) complexes and calf thymus DNA show hypochromism effect. The relationship between the values of HOMO–LUMO energy gap (?E) and the values of intrinsic binding constant (K_b) is revealed increasing of HOMO–LUMO energy gap accompanied by the decrease of K_b.     

Synthesis,crystal and molecular structure and spectroscopic studies (i.r., electronic,13C-n.m.r. and Mössbauer) of the perchlorate of nitrosyltetracyanoiron(II)-μ-cyano-pentaamminecobalt(III)trihydrate and its chromium(III) analogue

Summary The two new title compounds have been synthesized and characterized by x-ray crystal structure and spectroscopic measurements. Both compounds are air-stable and isomorphous. The crystal system, space group and Z for both compounds are: hexagonal, p6₁ and 6. Lattice constants for the Co^III and Cr^III complexes are as follows:a = 9.674(3) Å,c = 37.196(6) Å anda = 9.786(3) Å,c = 37.852(6) A, respectively. The molecular structure shows a great distortion in the Fe-C-N-M torsion angle [–46.8(7)° and –51.3(7)°, respectively] which has been interpreted as due to the presence of the NO ligand. The spectral studies confirm the presence of the -cyano ligand by the clear splitting of the (CN) stretching vibration atca. 2200 cm^–1 and the shift of 15–20 nm towards higher frequencies in the first d-d transition of M^III. The¹³C-n.m.r. spectrum of the diamagnetic Co^III complex confirms the presence of the -cyano ligand in solution and, as in the solid phase, the bridging group iscis to the NO of the nitroprusside. The Mössbauer spectra show that the principal axis component of electric field gradient tensor will most likely be directed in the Fe-NO direction (as in the nitroprusside ion) and not towards the CN bridge.     

Synthesis, 13C NMR and IR spectroscopic studies of gold(I) complexes of imidazolidine-2-thione and its derivatives

The gold(I) complexes of imidazolidine-2-thione and its derivatives were synthesized and their ¹³C NMR and IR spectroscopic studies were carried out. When gold(III) was reacted with the ligands using a 1:4 metal to ligand ratio, gold(III) was reduced to gold(I), the bis complexes of the general formula AuL_nX (where n = 2) were formed. However, when gold(III) was reduced to gold(I) by a reducing agent followed by an addition of the ligand to an aqueous or methanolic solution of gold(I), only mono complexes of the type AuLX were obtained. The structures of the reported complexes are proposed on the basis of their spectroscopic measurements.     

Reactions of 2-pyridylphenylacetonitrile with copper(II) chloride,copper(II) bromide,cobalt(II) chloride and cobalt(II) bromide

Reaction of 2-pyridylphenylacetonitrile with copper(II) chloride and copper(II) bromide in dry ethanol gives the hitherto unreported compound 1,2-di(cyano,phenyl,2′-pyridyl)ethane. The cobalt halides react with 2-pyridylphenylacetonitrile to form 1:1 complexes containing O-ethyl-2-phenyl-2-(2′-pyridyl)acetimidate as ligand. Removal of the ligand by the action of dry liquid ammonia on the complexes provides a better route to the pure imidate than the well known Pinner method.     

Synthesis, spectroscopic properties and crystal structure of mononuclear tricarbonylrhenium(I) chloride complexes carrying 6-functionalised quinoxalines

Two quinoxaline derivatives pqCH₃ and pqCl (where pq stands for 2-(2′-pyridyl)quinoxaline) were prepared by condensation of 2-acetyl pyridyl with 2-amino-4-methylphenylamine or 2-amino-4-chlorophenylamine, correspondingly and were studied spectroscopically and electrochemically, in correlation with the originally reported pq. Their novel corresponded complexes namely, fac-[Re(CO)₃Cl(L)] (where L = pqCH₃2 and pqCl 3) were synthesized, characterized, studied and compared to Re(CO)₃Clpq, 1. Complex 2 crystallizes in space group C2/c with a = 20.4476(17) Å, b = 15.4521(13) Å, c = 15.2887(13) Å, β = 126.1210(11)°, Z = 8 and V = 3902.0(6) Å³. The substitution of -H by -CH₃ or -Cl at 6-position of pq has a minor electronic effect on the pyridyl ring of the ligands, but seems to influence the quinoxaline moiety enough to alter the spectroscopical and electrochemical features.     

Synthesis, spectroscopic, electrochemical and Pb2+-binding studies of tetrathiafulvalene acetylene derivatives

A series of tetrathiafulvalene acetylene derivatives, [TTF-Ctriple bondC-A] [A=C6H4N(CH3)2-4 (1), C6H4OCH3-4 (2), C6H5 (3), C6H4F-4 (4), C6H4NO2-4 (5), C5H4N-2 (6), C5H4N-3 (7), and C5H4N-4 (8)], have been designed and synthesized to provide insight into the nature of the donor-acceptor interaction via a pi-conjugated triple bond. The X-ray crystal structure of [TTF-(Ctriple bondC)-C6H4OCH3-4] (2) reveals that the phenyl ring linked by acetylene is almost coplanar to the plane of TTF with a dihedral angle of 3.6 degrees. The strong intermolecular C-H...O hydrogen bonding was found to direct the molecular helical assemblies with a screw pitch of 5.148 A when viewed along the a-axis. Spectroscopic and electrochemical behaviors of the tetrathiafulvalene acetylene derivatives demonstrate that the TTF unit interacts with the electron-accepting group through the triple bond, thus leading to the intramolecular charge transfer. The pyridine-substituted TTF compounds 6-8 show remarkable sensing and coordinating properties toward Pb2+. Comparison of the spectroscopic and electrochemical properties and the calculation at the B3LYP/6-31G* level available in Gaussian 03 reveals that varying the bridged unit of the TTF-pi-A system from a double bond to a triple bond leads to positive shifts for the first and second oxidation potentials of the TTF moieties, while the extent of intramolecular charge transfer interactions through the pi-conjugated triple bond is smaller than that through the double bond.