Preparation and characterization of four polymeric metal complexes based on the flexible ligand 1H-1,2,4-triazole-1-propionic acid in different conformations

Three 2-D layered coordination polymers with (4,4) topology, {[Cu(trzp)₂(H₂O)]·1.18H₂O} _n (1), {[Co(trzp)₂(H₂O)₂]·2H₂O} _n (2), and {[Cd(trzp)₂(H₂O)]·2H₂O} _n (3), have been synthesized with the flexible, bifunctional ligand 1H-1,2,4-triazole-1-propionate (trzp^?) as a two-connected bridge. In addition, a complicated 3-D MOF [Ag₃(trzp)₂(NO₃)] _n (4) has been obtained with the help of Ag?Ag interactions and trzp^? as a four-connected linker. Htrzp and 1–4 have been characterized by single-crystal X-ray diffraction, elemental analysis, and infrared spectroscopy. The structural analysis showed that Htrzp has a gauche conformation in the solid state. However, both gauche and trans conformers of trzp^? are observed in the crystals of 1; only one conformer of trzp^? exists in the other three compounds (trans conformation in 2 and 3, and gauche conformation in 4). The thermal behaviors of 1–4 have been examined by thermal gravimetric analysis under nitrogen, which revealed that metal cyanide salts M(CN) _n (M?=?Cu(II), Co(II), Cd(II), and Ag(I), n?=?1 or 2) may be an intermediate pyrolytic decomposition product of the corresponding compounds.     

Cycloadditions of 1H-1,3-Benzazaphospholes with o-Chloranil

NH-Functional 1H-1,3-benzazaphospholes 1a–1c and o-chloranil (tetrachloro-o-benzoquinone - TCBQ) undergo rapid [1+4]-cycloaddition in a 1:2 molar ratio to give 2a – 2c as high-melting zwitterionic σ⁶λ⁵-phosphorus compounds. In the case of 2a the yield is high (rel. to TCBQ) even if the reactants were used in a 1:0.5 molar ratio. For the 2-tert-butyl-substituted compounds 2b and 2c the yields were significantly lower, in part by unidentified byproducts. Addition of excess TCBQ to crude 2c containing unconverted 1c did not increase but strongly decrease the amount of 2c . Crystallization and XRD analysis led to detection of a minor side or consecutive product 3c , formally corresponding to P=C bond cleavage and [1+4] cycloaddition of three equivalents TCBQ, two at the phosphinidene and one at the carbene end. NMR spectroscopic data of 2a – 2c including conclusive ¹³C data for 2a give evidence of the structures of the new compounds.     

An Au(III) complex of glycyl- S -serine: a linear polarized IR and 1H- and 13C-NMR investigation

The structure of a mononuclear Au(III) complex of the dipeptide glycyl-S-serine (Gly-Ser) has been predicted using solid-state linear dichroic IR (IR-LD) spectroscopy, based on an orientation technique in a nematic liquid crystal suspension. Results are compared with data from ¹H- and ¹³C-NMR, MS, elemental analysis, thermogravimetry and differential scanning calorimetry. The metal ion is coordinated as a tridentate through NH₂, N (from deprotonated amide) and O (COO^?) groups to form [Au(C₅H₉N₂O₄)Cl], with the fourth position of the square-planar coordination sphere being completed by a Cl^? ion.     

An azide‐bridged copper(II) complex: poly[piperazine‐1,4‐dium [tetra‐μ3‐azido‐κ12N1:N1:N1‐hexa‐μ2‐azido‐κ12N1:N1‐di‐μ2‐azido‐κ4N1:N3‐pentacopper(II)] tetrahydrate]

A new Cu^II–azide complex, {(C₄H₁₂N₂)[Cu₅(N₃)₁₂]·4H₂O}_n, has been synthesized by the reaction of piperazine, Cu(OAc)₂·2H₂O (OAc is acetate) and NaN₃. In the structure, μ₂‐1,1‐ and μ₃‐1,1,1‐azide anions bridge five Cu^II cations to form a linear pentanuclear cluster unit, which is further linked by μ₂‐1,1‐ and μ₂‐1,3‐azide anions to form a two‐dimensional condensed [Cu₅(N₃)₁₂]_n layer. The diprotonated piperazine and the solvent water molecules are hydrogen bonded to the coordination layers to form a three‐dimensional supramolecular network.     

Long-range 1H-15N correlation at natural abundance using gradient-enhanced inverse-detection

Inverse-detected heteronuclear shift correlation efficiency has been significantly augmented by the incorporation of pulsed field gradients (PFG). Phase-cycling requirements for t₁-noise suppression in gradient-enhanced experiments are, for the most part, obviated, making it feasible to acquire data in one or a few transients/t₁ increment. The benefits which acerue for ¹H-¹³C correlation (using GHMQC, GHMBC, and variants of GHMQC-TOCSY) are well documented. Less obvious is the increased facility with which long-range ¹H-¹⁵N correlation spectra can be acquired. An IDR-(Inverted Direct Response)-GHMQC-TOCSY was used to establish unequivocal proton resonance assignments for the alkaloid ajmaline. Long-range ¹H-¹⁵N heteronuclear couplings to the two nitrogen atoms of ajmaline were then probed using a gradient-enhanced ¹H-¹⁵N heteronuclear shift correlation experiment derived from HMQC. Long-range ¹H-¹⁵N couplings in ajmaline are assigned for the first time.     

Two complexes based on 1H-1,2,3-triazole-4,5-dicarboxylic acid: hydrothermal synthesis,crystal structures and spectral properties

[Zn₃(tda)₂(bipy)₂(H₂O)_2?·?4H₂O] _n (1) and [Co₂(Htda)₂(H₂O)₆·5H₂O] (2) have been synthesized and characterized structurally by X-ray diffraction, where H₃tda?=?1H-1,2,3-triazole-4, 5-dicarboxylic acid and 2,2′-bipy?=?2,2′-bipyridine. Their solid-state structures have been characterized by elemental analysis and IR spectroscopy. The molecular unit of 1 consists of two crystallographically unique Zn(II) ions assuming different coordination geometries, the tda^3? exhibits a hexadentate binding mode chelating three Zn(II) ions; neighboring Zn–Zn distances through tda^3? bridges are 5.910(6), 5.888(5), and 6.279(3)?Å, respectively. In 2, two neighboring Co(II) ions are bridged by two Htda^2? ligands, forming a binuclear structure, with Co–Co distance of 4.091?Å and is further linked to generate a 3-D structure via hydrogen bonds. Fluorescent of 1 was investigated.     

4(1H)-Quinolinone Alkaloids. An Efficient Synthesis of Graveoline by Palladium-Catalysed Reductive N-Heterocyclisation

An efficient synthesis of the 4H-quinolone alkaloid graveoline has been achieved by a route featuring an Pd(II)-catalysed reductive N-hetero-cyclisation [CO(3 MPa), Pd(TMB)₂, TMPhen, 170°C, 3h] of 2′-nitrochalcone as a key step.     

On the constitution of the macralstonidines

The alkaloid macralstonidine, which was originally isolated from Alstonia macrophylla WALL . by T. M. SHARP in 1934, has the molecular formula C₄₁H₄₈O₃N₄. The hydrolysis of this dimeric alkaloid yielded the macroline derivative 5 , N_(a)-methyl-sarpagine ( 6 ) and formaldehyde. Partial acid cleavage under deuterating conditions gave 5 -d₉, 6 -d₃ and decadeuterated macralstonidine. On the basis of spectral data, particularly an analysis of the mass spectra of macralstonidine and its decadeutero derivative, structure 2 has been elucidated for this alkaloid.     

Zinc complexes with 3-Pyridinyl-5-(2-salicylideneiminophenyl)-1H-1,2,4-triazoles

New coordination compounds of zinc with 3-(pyridine-2-yl)-5-(2-salicylideneiminophenyl)-1H-1,2,4-triazole (H₂L¹) and 3-(pyridine-4-yl)-5-(2-salicylideneiminophenyl)-1H-1,2,4-triazole (H₂L²) are obtained. According to X-ray diffraction data, binuclear zinc complexes with L¹, namely, [Zn₂L₂¹]. 0.5EtOH and [Zn₂L₂¹] · 2C₄H₈O₂ · 2H₂O obtained in different solvents, are structurally related molecular complexes. The product of the reaction with H₂L² is the {[ZnL²(Py)] · CHCl₃} _n coordination polymer. The 1,2,4-triazoles under study and the complexes on their basis luminesce in solutions with emission maxima ranging from 412 to 503 nm. These coordination compounds in the solid state emit in the green range of the spectrum (λ_max = 496 and 485 nm).     

Acid-catalyzed degradation of poly(2-butyl-1, 3, 6-trioxocane)

Acid-catalyzed degradation of poly(2-butyl-1,3,6-trioxocane) (1) has been studied. With ethyl tosylate as the catalyst, the cyclic monomer 2 was the major product. The minor products are cis and trans isomers of C₃H₇CH?CH? OCH₂CH₂OCH₂CH₂OH, and three stereoisomers of C₃H₇CH?CH? OCH₂CH₂OCH₂CH₂O? CH?CH? C₃H₇ elucidated by ¹H and ¹³C NMR, IR, electron impact and chemical ionization MS, and in the case of 2 also by comparison with an authentic sample. With 98% H₂SO₄ as the catalyst 2 is only a minor product. The major products are diethylene glycol, valeraldehyde, and 1,4-dioxane with some 2-butyl-1,3-dioxolane. Capillary GC/mass spectrometry led to identification of the following less abundant products: tri-n-propylbenzene, α,β-unsaturated aldehydes, and cyclic dimer. The products of H₂SO₄-catalyzed decomposition of polymer were also obtained by heating monomer 2 with H₂SO₄. A detailed mechanism for the formation of the eight-member ring 2 in the decomposition is proposed which involves unzipping proceeds via open carbocation intermediates. According to the principle of microscopic reversibility, the same open carbocation is the propagating species in the polymerization of 2 under similar conditions.     

The trans-Influence in Platinum (II) Complexes. 1H- and 13C-NMR. and X-ray structural studies of tridentate Schiff's base complexes of platinum (II)

¹H- and ¹³C-NMR. data are reported for the complexes [Pt (1) L] and [Pt (2) L]; 1 = OC₆H₄CH ? NCH₂CH₂O, 2 = OC₆H₄CH ? NC₆H₄O; L = PR₃, AsR₃, C ? N (cyclohexyl), DMSO, pyridine, secondary amine. The molecular structures of [Pt (2) (NHEt₂)] (I) and [Pt (2) (PPh₃)] (II) have been determined by X-ray analysis. Relevant bond distances for I: Pt-N (amine) = 2.076 Å, Pt-N (imine) = 2.017 Å, Pt-O = 1.992 Å and 2.002 Å; for II: Pt-P = 2.248 Å, Pt-N = 2.064 Å, Pt-O = 1.964 and 2.005 Å. Both the solid and solution state data are interpreted in terms of differences in the trans influence of the ligand L. The question of metal-ligand d-p π back bonding to the imine is discussed.     

Metastable ion decomposition and collisional activation mass spectra of 1,2,3-triarylpropen-1-ones

Substituents have been found to have a marked influence on the metastable ion decompositions and collisionally activated (CA) fragmentations of the M⁺˙ ion of a number of 1,2,3-triarylpropen-1-ones. An attempt has been made to confirm the structures of the rearrangement ions, [C₁₄H₁₀]⁺˙, [C₁₃H₁₁]⁺˙, [C₁₃H₉]⁺ and [C₁₂H₈]⁺˙ by comparison of their CA spectra with those of the corresponding ions produced from reference compounds. The results imply that [C₁₄H₁₀]⁺˙ and the M⁺˙ ions of phenanthrene and diphenylacetylene have a common structure, [C₁₃H₉]⁺ and the fluorenyl cation have a common structure and [C₁₂H₈]⁺˙ and biphenylene molecular ion have a common structure. The available data indicate that the ion at m/z 167 consists of a mixture of structures, likely possibilities being diphenylmethyl, phenyltropylium and dihydrofluorenyl cations.     

Synthesis of 2,3,4,6,7,8-Hexahydro-5H-1-benzopyran-5-ones and 3-(6-Oxo-1-cyclohexenyl)alkanoic Acids by Reduction of 4,6,7,8-Tetrahydro-2H-1-benzopyran-2,5(3H)-diones

Comparative results on the reduction of 4,6,7,8-tetrahydro-7,7-dimethyl-2H-1-benzopyran-2,5(3H)-diones 1 are reported. Hydride reduction (LiAlH₄ in Et₂O or NaBH₄ in i-PrOH) affords 2,3,4,6,7,8-hexahydro-5H-1-benzopyran-5-ones 5 in 30-60% isolated yield. Photochemical reduction of 1b and 1d (direct irradiation at λ = 300 or 254 nm in i-PrOH, or sensitized irradiation in acetone/i-PrOH or benzene/i-PrOH) gives 3-(6-oxo-1-cyclohexenyl)alkanoic acids 6 in 50–80%, while 1c affords the isomeric 3-(4,4-dimethyl-6-oxo-1-cyclohexenyl)-4-methyl-4-pentenoic acid ( 9 ) in 73% isolated yield. Electrochemical reduction (Hg, CH₃CN, Bu₄N⁺ClO, ?2.6 V vs. Ag/Ag⁺) requires more than 4 Farad/mol for the consumption of 1 without any major product being detected.     

Zur Photochemie von 1H- und 2H-Indazolen in saurer Lösung

On the Photochemistry of 1H- and 2H-Indazoles in Acidic Solution It is shown that 1H- and 2H-indazoles (cf. Scheme 2) on protonation (0, 1N H₂SO₄ in water or alcoholic solution) give analogous indazolium ions (see Fig. 1 and 2) which on irradiation undergo heterolytic cleavage of the N (1), N (2) bond whereby aromatic nitrenium ions in the singlet ground state are formed (cf. Scheme 13). If the para position of these nitrenium ions is not occupied by a substituent (e.g. a methyl group) they are readily trapped by nucleophiles present (e.g. water, alcohols, chloride ions) to yield the corresponding 5-substituted 2-amino-benzaldehydes or acetophenones (cf. Schemes 4–10). Photolysis of indazole ( 4 ) and 3-methyl-indazole ( 5 ) in 0,75N H₂SO₄ in alcoholic solutions gives in addition minor amounts of the corresponding 3-substituted 2-amino-benzaldehydes and acetophenones, respectively (cf. Schemes 6 and 8 and Table 2). Phenylnitrenium ions carrying a methyl group in the para position give in aqueous sulfuric acid mainly the reduction products, i.e. 2-amino-5-methyl-benzaldehydes (cf. Schemes 11 and 12 and Table 3). In methanolic sulfuric acid, in addition to the reduction products, 6-methoxy substituted benzaldehydes are found (cf. Schemes 11 and 12 and Table 3) which are presumably formed by an addition-elimination mechanism (cf. Scheme 18). It is assumed that precursors of the reduction products are the corresponding nitrenium ions in the triplet ground state. Singlet-triplet conversion of the nitrenium ions may become efficient when addition of nucleophiles to the singlet nitrenium ions is reversible (cf. Scheme 22) thus, enhancing the probability of conversion or when conjugation in the singlet nitrenium ions is disturbed by steric effects (cf. Scheme 20) thus, destabilizing the singlet state relative to the triplet state.     

Enantiomerically pure (1S,5R) and racemic 3‐(1‐benzothiophen‐2‐yl)‐8‐azoniabicyclo[3.2.1]oct‐2‐ene acetate

The title compound, C₁₅H₁₆NS⁺·C₂H₃O₂⁻, has been crystallized as both a pure enantiomer (1S,5R) and a racemate. The racemate crystallizes in the space group Cc, with molecules of opposite handedness related to each other by the action of the c‐glide. The enantiomer is essentially isostructural with the racemate, except that the glide symmetry is violated by interchange of CH and CH₂ groups within the seven‐membered ring. The space‐group symmetry is reduced to P1 with two molecules in the asymmetric unit. The enantiomer structure shows disorder of the thiophene ring for one of the molecules in the asymmetric unit. The major component of the disorder has the thiophene ring in the same position as in the racemate, but generates a higher‐energy molecular conformation. The minor disorder component has different intermolecular interactions but retains a more stable molecular conformation.     

Dual Mechanism of an Intramolecular Charge Transfer (ICT)–FRET‐Based Fluorescent Probe for the Selective Detection of Hydrogen Peroxide

A dual‐mechanism intramolecular charge transfer (ICT)–FRET fluorescent probe for the selective detection of H₂O₂ in living cells has been designed and synthesized. This probe used a coumarin–naphthalimide hybrid as the FRET platform and a boronate moiety as the recognition group. Upon the addition of H₂O₂, the probe exhibited a redshifted (73 nm) fluorescence emission, and the ratio of fluorescence intensities at λ =558 and 485 nm (F ₅₅₈/F ₄₈₅) shifted notably (up to 100‐fold). Moreover, there was a good linearity (R ²=0.9911) between the ratio and concentration of H₂O₂ in the range of 0 to 60 μm , with a limit of detection of 0.28 μm (signal to noise ratio (S/N)=3). This probe could also detect enzymatically generated H₂O₂. Importantly, it could be used to visualize endogenous H₂O₂ produced by stimulation from epidermal growth factor.     

4,5-Dihydro-7,8-dimethoxy-1-phenyl-3H-2,3-benzodiazepin-4-one

The title compound, C₁₇H₁₆N₂O₃, is an antagonist for AMPA/kainate receptors. The mol­ecule has its seven-membered oxa­diazo­le ring in a boat conformation. Asymmetry of the two methoxy bond angles is evident, with (Me)O—C—C angles of 115.45 (12) and 124.78 (13)°, and 114.67 (12) and 125.31 (12)°. A centrosymmetric dimer involving the HN—CO moieties, with an N⃛O distance of 2.876 (2) Å, graph set R(8), is further linked into chains through methoxy Csp³—H⃛N hydrogen bonds, with a C⃛N distance of 3.418 (2) Å.     

1H,4H-1,4-diborabuckminsterfullerene with pyridine molecules and ytterbium endo-atom

The competition between the ytterbium endo-atom and the pyridine exo-molecules as nucleophiles interacting with the electron-deficient 1H,4H-1,4-diborabuckminsterfullerene was studied using the quantum chemical DFT PBE0 method. The equilibrium structural parameters, dipole moments, IR spectra, and exothermic effects of the formation of the C₅₈B₂•Py₂ adduct and the endohedral Yb@C₅₈B₂•Py₂ complex were determined. The concept of the state of oxidation/reduction of an atom in a chemical compound has been clarified. The localization of the ytterbium(II) under a pair of equivalent carbon atoms bonded to boron(III) atoms is predicted. The introduction of ytterbium(II) into the adduct cavity weakens exo-bonds with pyridine molecules without changing the oxidation state of boron(III). Each nitrogen atom retains a lone electron pair, coordinated by a boron(III). The ytterbium(II) endo-atom retains 14 electrons in f states.     

Four NiII complexes with the new cyclam–methylimidazole ligand 1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane

Although it has not proved possible to crystallize the newly prepared cyclam–methylimidazole ligand 1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane (L^Im1), the trans and cis isomers of an Ni^II complex, namely trans‐aqua{1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane}nickel(II) bis(perchlorate) monohydrate, [Ni(C₁₅H₃₀N₆)(H₂O)](ClO₄)₂·H₂O, (1), and cis‐aqua{1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane}nickel(II) bis(perchlorate), [Ni(C₁₅H₃₀N₆)(H₂O)](ClO₄)₂, (2), have been prepared and structurally characterized. At different stages of the crystallization and thermal treatment from which (1) and (2) were obtained, a further two compounds were isolated in crystalline form and their structures also analysed, namely trans‐{1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane}(perchlorato)nickel(II) perchlorate, [Ni(ClO₄)(C₁₅H₃₀N₆)]ClO₄, (3), and cis‐{1,8‐bis[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane}nickel(II) bis(perchlorate) 0.24‐hydrate, [Ni(C₂₀H₃₆N₆)](ClO₄)₂·0.24H₂O, (4); the 1,8‐bis[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane ligand is a minor side product, probably formed in trace amounts in the synthesis of L^Im1. The configurations of the cyclam macrocycles in the complexes have been analysed and the structures are compared with analogues from the literature.