Synthesis of layered cathode material Li[CoxMn1−x]O2 from layered double hydroxides precursors

Cathode materials Li[Co_xMn_1−x]O₂ for lithium secondary batteries have been prepared by a new route—precursor method of layered double hydroxides (LDHs). In situ high-temperature X-ray diffraction (HT-XRD) and thermogravimetric analysis coupled with mass spectrometry (TG-MS) were used to monitor the structural transformation during the reaction of CoMn LDHs and LiOH·H₂O: firstly the layered structure of LDHs transformed to an intermediate phase with spinel structure; then the distortion of the structure occurred with the intercalation of Li⁺ into the lattice, resulting in the formation of layered Li[Co_xMn_1−x]O₂ with α-NaFeO₂ structure. Extended X-ray absorption fine structure (EXAFS) data showed that the Co-O bonding length and the coordination number of Co were close to those of Mn in Li[Co_xMn_1−x]O₂, which indicates that the local environments of the transitional metals are rather similar. X-ray photoelectron spectroscopy (XPS) was used to measure the oxidation state of Co and Mn. The influences of Co/Mn ratio on both the structure and electrochemical property of Li[Co_xMn_1−x]O₂ have been investigated by XRD and electrochemical tests. It has been found that the products synthesized by the precursor method demonstrated a rather stable cycling behavior, with a reversible capacity of 122.5 mAh g⁻¹ for the layered material Li[Co_0.80Mn_0.20]O₂.     

Synthesis, characterization and crystal structures of cyclometallated palladium (II) compounds containing difunctional ligands with [P,P], [As,As], [N,N], [P,As], [P,N] and [P,O] donor atoms

Treatment of the chloro-bridged dinuclear complex [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}(μ-Cl)]₂ (1) with homobidentate [P,P], [As,As], [N,N], and heterobidentate [P,As], [P,N] ligands in a 1:1 molar ratio gave the dinuclear complexes [{Pd[3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N](Cl)}₂{μ-L}] (L = Ph₂PC₄H₆(NH)CH₂PPh₂ (2); Ph₂As(CH₂)₂AsPh₂ (3); 1,3-(NH₂CH₂)₂C₆H₄ (4); Ph₂P(CH₂)₂AsPh₂ (5); Ph₂P(CH₂)₂NH₂ (6)), with the bidentate ligands bridging the two cyclometallated fragments.The reaction with the homobidentate ligands in a 1:2 molar ratio in the presence of NaClO₄ afforded the mononuclear compounds [[Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{L-P,P}][ClO₄] (L = Ph₂PC₄H₆(NH)CH₂PPh₂ (7); (o-Tol)₂P(CH₂)₂P(o-Tol)₂ (8)), [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{Ph₂As(CH₂)₂AsPh₂-As,As}][ClO₄] (9) and [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{L-N,N}][ClO₄] (L = NH₂(CH₂)₃NH₂ (10); NH₂(C₆H₈)CH₂(C₆H₈)NH₂ (11); 1,3-(NH₂CH₂)₂C₆H₄ (12); 1,3-(NH₂)₂C₅H₃N (13); NH₂(C₆H₄)O(C₆H₄)NH₂ (14); NMe₂(CH₂)₂NMe₂ (15)), in which the chloro ligands are absent and the bidentate ligands are chelated to the palladium atom.Reaction of 1 with Ph₂P(CH₂)₂AsPh₂ in 1:2 molar ratio in acetone in the presence of NH₄PF₆ afforded the analogous mononuclear compound [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{Ph₂P(CH₂)₂AsPh₂-P,As}][PF₆] (16); whereas reaction with Ph₂P(CH₂)₃NH₂ gave [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{Ph₂P(CH₂)₃N(CMe₂)-P,N}][PF₆] (17), derived from intermolecular condensation between the aminophosphine and acetone. Condensation of the NH₂ group was precluded by change of solvent, using dichloromethane.Iminophoshines also reacted with 1 in 1:2 molar ratio in acetone to give a new series of mononuclear cyclometallated complexes: [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{L-P,N}][ClO₄] (L = Ph₂PC₆H₄C(H)NCy (20); Ph₂PC₆H₄C(H)NC(CH₃)₃ (21); Ph₂PC₆H₄C(H)NNMe₂ (22); Ph₂PC₆H₄C(H)NNHMe (23); Ph₂PC₆H₄C(H)NNHPh (24)). Analogous complexes with a stable P,O-chelate were obtained using bidentate [P,O] donor ligands: [Pd{3,4-(MeO)₂C₆H₂C(H)N(Cy)-C6,N}{L-P,O}][Cl] (L = 2-(Ph₂P)C₆H₄CHO (25); Ph₂PN(Me)C(O)Me (26)).The crystal structures of compounds 1, 5, 15, 16, 18, 20 have been determined by X-ray crystallography.     

One pot synthesis of imidazo[2,1-b]thiazoles and benzo[d]thiazolo[3,2-a]imidazoles

A series of imidazo[2,1-b]thiazole and benzo[d]thiazolo[3,2-a]imidazole analogues were synthesized by stirring an equimolar mixture of dibenzoylacetylene with imidazole/thiazole derivatives in toluene or acetonitrile at room temperature. The products were generated in good yields and characterized by standard analytical techniques such as IR, ¹H NMR, ¹³C NMR and mass spectrometry. The structure of products 19, 20, 22, 24 and 25 were also unambiguously confirmed by single crystal X-ray analysis.     

Synthesis, properties, and oxidizing function of 6-substituted 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]pyrrole-8(7H),10(9H)-dionylium tetrafluoroborates

Uracil-annulated heteroazulenes, 6-substituted 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]pyrrole-8(7H),10(9H)-dionylium tetrafluoroborates 7a,b·BF₄⁻, which are the isoelectronic compounds of 5-dezazaflavin, were synthesized. X-Ray crystal analysis and MO calculations were carried out to clarify the structural characteristics of 7a,b·BF₄⁻. The stability of cations 7a,b is expressed by the pK_R+ values which were determined spectrophotometrically to be 10.9 and 11.2, respectively. The electrochemical reduction of 7a,b exhibited high reduction potentials at −0.84 and −0.87 (V vs Ag/AgNO₃) upon cyclic voltammetry (CV). A good linear correlation between the pK_R+ values and reduction potentials (E1_red) of 7a,b·BF₄⁻ and reference compounds 4·BF₄⁻ and 5·BF₄⁻ was obtained. In a search of the reactivity, reactions of 7a,b·BF₄⁻ with some nucleophiles, hydride and diethylamine, were carried out to clarify that the introduction of nucleophiles to give regio-isomers is dependent on the nucleophile. The photo-induced oxidation reactions of 7a,b·BF₄⁻ toward some alcohols under aerobic conditions were carried out to give the corresponding carbonyl compounds in more than 100% yield [based on compounds 7a,b·BF₄⁻], suggesting the oxidizing function of 7a,b·BF₄⁻ toward alcohols in the autorecycling process.     

Convenient synthesis of 7-aryl-3,4,5,6-tetrahydro-2H-pyrido[4,5-b]- and [2,3-b]-1,5-oxazocine-6-ones

A convenient and diversity-oriented method for synthesis of the novel 7-aryl-3,4,5,6-tetrahydro-2H-pyrido[4,5-b]-1,5-oxazocine-6-one skeleton 1 and the very rarely described 7-aryl-3,4,5,6-tetrahydro-2H-pyrido[2,3-b]-1,5-oxazocine-6-one skeleton 2, featuring cyclization using nucleophilic aromatic substitution (S_NAr) and Suzuki coupling, is described.     

First identification of benzo[cd]phenanthro[1,2,3-lm]perylene by high-pressure liquid chromatography with ultraviolet-visible spectroscopy and mass spectrometry

Benzo[cd]phenanthro[1,2,3-lm]perylene has been identified as a product of supercritical 1-methylnaphthalene pyrolysis from an experiment performed at 585 °C, 110 atm, and 140 s in a supercritical fluid flow reactor. The identification of benzo[cd]phenanthro[1,2,3-lm]perylene is based on the product's mass spectrum, HPLC elution time, and UV absorbance spectrum. The mass spectrum of the identified 1-methylnaphthalene pyrolysis product, called component I here, reveals a molecular weight of 426, corresponding to a C₃₄H₁₈ polycyclic aromatic hydrocarbon (PAH). The extremely long HPLC elution time, 20–48 min longer than those of the four other C₃₄H₁₈ PAH components in this product mixture, indicates that component I has a planar structure with a high length-to-breadth ratio. Annellation theory is used to interpret and compare the UV spectrum of component I with those of the C₃₀H₁₆ benzo[cd]naphtho[1,2,3-lm]perylene and the C₃₆H₁₈ teropyrene, structures with one ring less and one ring more, respectively, than that of component I. This analysis of component I's UV spectrum, in conjunction with its mass spectrum and HPLC elution behavior, all lead to the identification of component I as the nine-ring PAH benzo[cd]phenanthro[1,2,3-lm] perylene, a molecule whose existence has never before been documented.     

Application of cyclic-1,3-diketones in domino and multicomponent reactions: facile route to highly functionalized chromeno[2,3-d]pyrimidinones and diazabenzo[b]fluorenones under solvent-free conditions

A facile and efficient protocol for the synthesis of chromeno[2,3-d]pyrimidinones and diazabenzo[b]fluorenones has been developed by one-pot three-component cyclocondensation of aldehydes, cyclic-1,3-diketones and 1,3-dimethylbarbituric acid in the presence of InCl₃ or P₂O₅ under solvent-free conditions.     

Synthesis and photovoltaic properties of new [1,2,5]thiadiazolo[3,4-c]pyridine-based organic Broadly absorbing sensitizers for dye-sensitized solar cells

In this paper, by introducing [1,2,5]thiadiazolo[3,4-c]pyridine (PT) as an auxiliary acceptor into the molecular design of organic sensitizers, we have synthesized four new dyes (PT1–PT4) for dye-sensitized solar cells (DSSCs) with triphenylamine or N,N-diphenylthiophen-2-amine as the donor units and thiophene or benzene as the π-bridges, respectively. All the structures, optical and electrochemical properties were fully characterized. Nanocrystalline TiO₂ dye-sensitized solar cells were also fabricated using these dyes. Among them, PT2-based DSSCs showed the highest overall conversion efficiency of 6.11% with V_oc=668 mV, J_sc=12.61 mA cm⁻² and a fill factor (FF)=0.74 after a chenodeoxycholic acid (CDCA) treatment under standard illumination condition (100 mW cm⁻² simulated AM 1.5 solar light).     

Short and efficient access to imidazo[1,2-a]pyrrolo[3,2-c]pyridine derivatives

Access to N-protected or N-free imidazo[1,2-a]pyrrolo[3,2-c]pyridine derivatives as potential antiviral compounds was achieved in good yields from N-protected 7-amino-8-halo-2-methylimidazo[1,2-a]pyridines by catalytic coupling of terminal acetylenes under mild conditions using [PdCl₂(PPh₃)₂] or [Cu(Phen)(PPh₃)₂]NO₃.     

Ring transformation of cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium ion to the corresponding pyrrole derivatives via troponeimine intermediates: photo-induced autorecycling oxidizing reactions of some amines

Ring transformation of 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]furan- 8(7H),10(9H)-dionylium tetrafluoroborate 4⁺·BF₄⁻ to 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]pyrrrole-8(7H),10(9H)-dionylium tetrafluoroborate 6a-d⁺·BF₄⁻ consists of the reaction of 4⁺·BF₄⁻ with amines and subsequent exchange of the counter-ion using aq. HBF₄. Reactions of 4⁺·BF₄⁻ with aniline and 4-substituted anilines afforded the corresponding pyrrole derivatives 6a-c⁺·BF₄⁻ directly in good yields. On the other hand, reaction of 4⁺·BF₄⁻ with benzylamine gave the troponeimine intermediate 9, which was not converted to 6d⁺·BF₄⁻ and reverted to 4⁺·BF₄⁻ by adding HBF₄; however, it was converted to 6d⁺·BF₄⁻ upon treatment with (COCl)₂ or SOCl₂, followed by exchange of the counter-ion. In a search for the characteristics of 9, inspection and comparison of the X-ray crystal analyses, NMR and UV-vis spectra, and CV measurement of 9 and N,N-disubstituted troponeimine derivatives 12 were carried out to suggest the remarkable structure of 12 having ionic C-O bonding between the imine-carbon atom and the oxygen atom of the barbituric acid moiety in the solid state. Thus, characteristics of 9 were ascribed to the sterically hindered and favorable conformation of N-protonated troponeimine intermediates. Furthermore, novel photo-induced oxidation reactions of a series of 4⁺·BF₄⁻, 5⁺·BF₄⁻, and 6a,e⁺·BF₄⁻ towards some amines under aerobic conditions were carried out to give the corresponding imines in 455-8362% yields [based on compounds 4⁺, 5⁺, and 6a,e⁺], suggesting the oxidation reaction occurs in an autorecycling process. Mechanistic aspects of the amine-oxidation reaction are also postulated.     

New synthesis of N-substituted benz[g]isoquinoline-3,5,10(2H)-triones

Various N-substituted benz[g]isoquinoline-3,5,10(2H)-triones 7 were prepared starting from vitamin K₃ (menadione) 9. The key steps involve substitution of a benzylic bromide by a primary amine and intramolecular condensation across the ester moiety of a (3-bromomethyl-naphth-2-yl)acetate 8 followed by oxidation with cerium(IV) ammonium nitrate (CAN) and spontaneous dehydrogenation, resulting in the title compounds 7. A selection of the synthesised new compounds was tested in vitro against Mycobacterium tuberculosis.     

Novel synthesis and properties of 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]thiophen-8(7H),10(9H)-dionylium tetrafluoroborate: autorecycling oxidation of some alcohols under photo-irradiation

Three-step reactions starting from 2-chlorotropone with dimethylthiobarbituric acid afforded 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]thiophen-8(7H),10(9H)-dionylium tetrafluoroborate 5·BF₄⁻, which is the isoelectronic compound of the 5-ethyl-3-methyllumiflavinium ion. The X-ray crystal analysis and MO calculation were carried out to clarify the structural characteristics of 5·BF₄⁻. The stability of cation 5 is expressed by the pK_R+ value, which was determined spectrophotometrically as 5.1. The electrochemical reduction of 5 exhibited low reduction potential at −0.53 (V vs Ag/AgNO₃), upon cyclic voltammetry (CV). In a search for the reactivity, reactions of 5·BF₄⁻ with some nucleophiles, hydride, diethylamine, thiols, and methanol, were carried out, which revealed that the introduction of nucleophiles to give regio-isomers is dependent on the nucleophile. The photo-induced oxidation reactions of 5·BF₄⁻ toward some alcohols under aerobic conditions were carried out to give the corresponding carbonyl compounds in more than 100% yield [based on compound 5·BF₄⁻], suggesting the oxidizing function of 5·BF₄⁻ toward alcohols in the autorecycling process. The UV-vis and fluorescence spectra of 5 were studied to suggest the electron transfer from alcohols to the excited 5.     

Preparation of novel pyridine-fused tris-heterocycles; pyrido[4,3-e]pyrrolo-/pyrido[4,3-e]furano[2,3-c]pyridazines and pyrido[3,4-b]pyrrolo[3,2-d]pyrrole

Three novel pyrido-fused tris-heterocycles have been prepared based on a Suzuki coupling and subsequent cyclisation approach. Pyrido[4,3-e]pyrrolo[2,3-c]pyridazine (3b, 77%) and pyrido[4,3-e]furano[2,3-c]pyridazine (5b, 76%) were obtained by intramolecular diazocoupling. Successful diazocoupling of furan (5b) is thus reported for the first time by NOBF₄ generation of the diazonium intermediate. N-TIPS-pyrido[3,4-b]pyrrolo[3,2-d]pyrrole (TIPS-4b) was synthesised by thermal cyclisation of pyridyl nitrene in considerably higher yield (71%) than previously experienced from similar cyclisations, due to TIPS-activation.     

Imidazole-based bifunctional chelates for the “fac-[Re(CO)3]” core

Three monocationic rhenium(I) complexes of the type [Re(CO)₃(L)]Br, containing the bis-imidazole tridentate ligands bis-(2-(1-methylimidazolyl)methyl)amine (L¹), bis-(2-(1-methylimidazolyl)methyl)aminoethanol (L²) and bis-(2-(benzimidazolyl)ethyl)sulfide (L³), were prepared and characterized by ¹H NMR and IR spectroscopy. The complex salt [Re(CO)₃(L²)]Br (2) was also characterized by X-ray crystallography. The structure consists of discrete monocationic monomers with a fac-[Re(CO)₃]⁺ coordination unit, and the remaining three sites are occupied by one amine and two imidazolyl nitrogen donor atoms.     

Novel synthesis and properties of 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborate: autorecycling oxidation of some alcohols under photo-irradiation

Three-step reactions starting from 2-chlorotropone with barbituric acid afforded novel 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborate (9·BF₄⁻), which is the isoelectronic compound of the 5-ethyl-3-methyllumiflavinium ion. The stability of cation 9 is expressed by the pK_R+ value, which was determined spectrophotometrically, as ca. 6.0. The electrochemical reduction of 9 exhibited low reduction potential at −0.58 (V vs Ag/AgNO₃), upon cyclic voltammetry (CV). In a search for the reactivity, reactions of 9·BF₄⁻ with some nucleophiles, hydroxide, hydride, amines, thiols, and methanol, were carried out to exhibit that the introduction of nucleophiles is dependent on the nucleophile itself. The photo-induced oxidation reactions of some alcohols catalyzed by 9·BF₄⁻ under aerobic conditions were carried out to give the corresponding carbonyl compounds in more than 100% yield [based on compound 9·BF₄⁻], suggesting the oxidizing function of 9·BF₄⁻ toward alcohols in the autorecycling process. The UV-vis and fluorescence spectra of 9 were studied to suggest the electron transfer from alcohols to the excited 9.     

Regioselective N-alkylation of imidazo[4,5-b]pyridine-4-oxide derivatives: an experimental and DFT study

Regioselectivities were determined for N-alkylations of imidazo[4,5-b]pyridine-4-oxide and 2-methyl-imidazo[4,5-b]pyridine-4-oxide with benzyl bromide or benzyl iodide at RT using K₂CO₃ in DMF as a base. Experimental attempts have shown that N-1/N-3 ratios slightly varied according to the substitution on C-2 position. This was confirmed by DFT calculations in solvent phase. This computational study has shown first that this N-benzylation reaction passed through a S_N2 mechanism. Moreover, regioselectivity of N-benzylation has appeared essentially governed by ‘steric approach control’. It explained that opposite N-1/N-3 ratios were obtained with imidazo[4,5-b]pyridine-4-oxide and its 2-methyl-substituted analog. Finally, regioselectivities slightly varied with the nature of benzyl halide.     

Synthesis of fused dihydropyrido[e]purines via ring closing metathesis

Ring closing metathesis (RCM) of 8,9-diallylpurines or 9-butenyl-8-vinylpurines with the Grubbs 2nd generation catalyst resulted in fused 6,9- or 8,9-dihydropyrido[e]purines, respectively. The 8,9-dialkenylpurines were prepared from 8-bromopurines after 9-alkenylation and subsequent Stille coupling at C-8 with alkenylstannanes in the presence of Pd(PPh₃)₄ or Pd(PPh₃)₂Cl₂.     

6,8-Dimethylpyrimido[4,5-c]pyridazine-5,7(6H,8H)-dione: new heterocyclizations based on SN-methodology. Unexpected formation of the first iso-π-electronic analogue of the still unknown dibenzo[a,o]pycene

N₍₂₎-Oxide and 3-amino derivatives of 6,8-dimethylpyrimido[4,5-c]pyridazine-5,7(6H,8H)-dione have been shown to react with primary alkylamines in the presence of an oxidant to produce condensed imidazolines or imidazoles. Both conversions based on S_N^H-strategy represent a new approach to imidazoline-(imidazole-)ring annulation. Heterocyclic analogues of the still unknown dibenzo[a,o]pycene were obtained as a by-products of the above transformations upon using of cyclohexylamine.     

Preparation of 2,4,5-trisubstituted pyrazolo[4,3-c]quinolin-3-ones

The preparation of pyrazolo[4,3-c]quinolinones is reported starting from 2-substituted-5-(2-fluorophenyl)-3-oxo-2,4-dihydro-3H-pyrazol-3-ones. A one-pot protocol, in which condensation with an orthoamide followed by substitution with a primary amine and subsequent S_NAr-cyclization to provide rapid access to 4- and 5-substituted pyrazolo[4,3-c]quinolinones was developed.     

Preparation of new pyrido[3,4-b]thienopyrroles and pyrido[4,3-e]thienopyridazines

Two new types of pyrido-fused tris-heterocycles (1a,b and 2a,b) have been prepared from 3-aminopyridine in five/six steps. A synthetic strategy for the preparation of the novel pyrido[3,4-b]thieno[2,3- and 3,2-d]pyrroles (1a,b) and pyrido[4,3-e]thieno[2,3- and 3,2-c]pyridazines (2a,b) has been studied. The Suzuki cross coupling of the appropriate 2- and 3-thienoboronic acids (3,4) and 4-bromo-3-pyridylpivaloylamide (9) afforded the biaryl coupling products (10,11) in high yields (85%). Diazotization of the hydrolysed (2-thienyl)-coupling product (12) and azide substitution gave the 3-azido-4-(2-thienyl)pyridine intermediate (72%, 14). 3-Azido-4-(3-thienyl)pyridine (15) was prepared by exchanging the previous order of reactions. The desired β-carboline thiophene analogues (1a,b) were obtained via the nitrene by thermal decomposition of the azido precursors (14,15). By optimising conditions for intramolecular diazocoupling, the corresponding pyridazine products (72-83%, 2a,b) were afforded.