Comparative study on the Al–Al multiple bond in Na2[Arx′AlAlArx′] and H2[Arx′AlAlArx′] (Arx′?=?C6H3-2, 6-(C6H5)2)

The Al–Al multiple bond in Na₂[Arx′AlAlArx′] (Arx′ = C₆H₃-2,6-(C₆H₅)₂) was investigated and compared with H₂[Arx′AlAlArx′] by electron localization function (ELF) method. The roles of sodium, hydrogen atoms, and bulky ligands in these two complexes were also discussed. The calculated results show that Na₂[Arx′AlAlArx′] and H₂[Arx′AlAlArx′] have different structural and electronic features. In Na₂[Arx′AlAlArx′], the Al–Al bond includes a σ bond, a normal π bond and a slipped π bond. In H₂[Arx′AlAlArx′], the direct Al–Al bond was substituted by two 3-center, 2-electron (3c–2e) bridged bonding, which formed by the hydrogen and two aluminum atoms. The bulky ligands play important stabilizing roles in both Na₂[Arx′AlAlArx′] and H₂[Arx′AlAlArx′].     

Mesogenic and magnetic behavior in cobalt(II) and iron(II) compounds with long alkyl chains

Abstract  

Metal complexes with long alkyl chains [Co(C16-terpy)₃](BF₄)₂ (1), [Fe(C16-terpy)₂](BF₄)₂ (2), [Co(C16-terpy)₂](BPh₄)₂ (3), [Co(C14-terpy)₂](BF₄)₂ (4), and [Fe(C12C10C5-terpy)₂](BF₄)₂ (5) were synthesized and their physical properties characterized, where C16-terpy, C14-terpy, and C12C10C5-terpy are 4′-hexadecyloxy-2,2′:6′,2′′-terpyridine, 4′-tetradecyloxy-2,2′:6′,2′′-terpyridine, and 4′-5′′′-decyl-1′′′-heptadecyloxy-2,2′:6′,2″-terpyridine, respectively. Complexes 1, 2, and 5 exhibited liquid–crystal properties in the temperature ranges of 371–528 K and 466–556 K, and 88–523 K, respectively. Variable-temperature magnetic susceptibility measurements revealed that the Co(II) complexes 1 and 4 exhibited unique spin transitions (T _1/2↓ = 217 K and T _1/2↑ = 260 K for 1 and T _1/2↓ = 250 K and T _1/2↑ = 307 K for 4), so-called ‘reverse spin transition,’ induced by structural phase transitions. Complex 3 exhibited gradual spin-crossover behavior (T _1/2 = 160 K.), and complex 5 exhibited spin transitions (T _1/2↑ = 288 K and T _1/2↓ = 284 K) at the liquid crystal transition temperature. Compounds with multifunction, i.e., magnetic and liquid–crystal properties, are important in the development of molecular materials.     

Solvothermal synthesis and structures of three novel heterometallic microporous coordination polymers assembled from 2-hydroxy-nicotinic acid

Abstract  

Three novel heterometallic microporous coordination polymers {M(Hnico)₃M′} _n (1, M = Co, M′ = K; 2, M = Ni, M′ = K; 3, M = Co, M′ = Na, Hnico is the anion of 2-hydroxy-nicotinic acid, where the proton is transferred from the phenolate hydroxy group to the nitrogen atom of imine pyridine ring) were synthesized by hydrothermal reaction between M(Ac)₂·4H₂O, M′OH and a multifunctional organic aromatic H₂nico ligand and characterized by IR spectrum, elemental analysis, raman spectrum and the single crystal X-ray diffractions. In complexes 1–3, the M²⁺ ions linked three different Hnico ligand formed [M(Hnico)₃]⁻ subunit which further interlinked the six-coordination M′⁺ cation constructed 3D network. The network topology of 1–3 can be simplified a rare 3D (4,4)-connected (4¹²6³) net.     

La3Pd4Zn4 and La3Pt4Zn4 with a different coloring of the Gd3Cu4Ge4-type structure

Abstract  

The intermetallic zinc compounds La₃Pd₄Zn₄ and La₃Pt₄Zn₄ were synthesized by induction melting of the elements in sealed tantalum tubes. The structures were refined from X-ray single-crystal diffractometer data: Gd₃Cu₄Ge₄ type, Immm, a = 1,440.7(5), b = 743.6(2), c = 419.5(2) pm, wR ₂ = 0.0511, 353 F ² for La₃Pd₄Zn₄; and a = 1,439.9(2), b = 748.1(1), c = 415.66(6) pm, wR ₂ = 0.0558, 471 F ² for La₃Pt₄Zn₄ with 23 variables per refinement. The palladium (platinum) and zinc atoms build up a three-dimensional polyanionic [Pd₄Zn₄] (260–281 pm Pd–Zn) and [Pt₄Zn₄] (260–279 pm Pt–Zn) network in which the lanthanum atoms fill cavities of CN 14 (6 Pd/Pt + 8 Zn for La1) and CN 12 (6 Pd/Pt + 6 Zn for La2), respectively. The copper position of the Gd₃Cu₄Ge₄ type is occupied by zinc and the two crystallographically independent germanium sites by palladium (platinum), a new coloring pattern for this structure type. Within the [Pd₄Zn₄] and [Pt₄Zn₄] the Pd2 and Pt2 atoms form Pd2–Pd2 (291 pm) and Pt2–Pt2 (296 pm) dumbbells. The structures of La₃Pd₄Zn₄ and La₃Pt₄Zn₄ are discussed with respect to the prototype Gd₃Cu₄Ge₄ and the Zintl phase Sr₃Li₄Sb₄. Temperature-dependent magnetic susceptibility measurements indicate diamagnetism for La₃Pt₄Zn₄ and Pauli paramagnetism for La₃Pd₄Zn₄.     

Synthesis, structural characterization, and magnetic properties of the metallamacrocycle [Fe6(C11H11N2O3)6(C4H9NO)6]

Abstract  

The 18-metallacrown-6 metallamacrocycle [Fe₆(pmshz)₆(C₄H₉NO)₆] has been synthesized by the self-assembly reaction of iron ions with N-substituted salicylhydrazide ligands. Six Fe(III) ions and six deprotonated N-propanoyl-4-methylsalicylhydrazide (H₃ pmshz) ligands construct a planar 18-membered ring based on Fe–N–N–Fe linkage. Because of the coordination, the ligand enforces the stereochemistry of the Fe(III) ions as a propeller shape with alternating …ΔΛΔΛ… configurations. There is a strong antiferromagnetic exchange interaction between the paramagnetic iron centers.     

Synthesis of imidazo[4,5-a]acridones and imidazo[4,5-a]acridines as potential antibacterial agents

Abstract  

New imidazo[4,5-a]acridone derivatives were synthesized from the rearrangement of 3H-imidazo[4′,5′:3,4]benzo[c]isoxazoles. New imidazo[4,5-a]acridines were obtained from the reaction of imidazo[4,5-a]acridones in boiling POCl₃. All of these compounds exhibited antimicrobial activities comparable to streptomycin as reference drug.     

Determination of heat capacities of PbCrO4(s), Pb2CrO5(s), and Pb5CrO8(s)

Abstract  

Heat capacities of PbCrO₄(s), Pb₂CrO₅(s), and Pb₅CrO₈(s) were measured by differential scanning calorimetry. The measured heat capacities as a function of temperature are expressed as C _p <PbCrO₄> J K⁻¹ mol⁻¹ = 150.37 + 27.74 × 10⁻³ T − 2.80 × 10⁶ T ⁻² (T = 300–750 K), C _p <Pb₂CrO₅> J K⁻¹ mol⁻¹ = 194.55 + 76.09 × 10⁻³ T − 4.64 × 10⁶ T ⁻² (T = 300–700 K), and C _p  <Pb₅CrO₈> J K⁻¹ mol⁻¹ = 323.35 + 184.80 × 10⁻³ T − 5.48 × 10⁶ T ⁻² (T = 300–600 K). From the measured heat capacity data, thermodynamic functions such as enthalpy increments, entropies, and Gibbs energy functions were derived.     

A novel three-dimensional malonate-bridged complex {[Cu4(4,4′- bpy)8(mal)2(H2O)4](ClO4)2(H2O)4(CH3OH)2}n

A novel malonate-bridged copper (II) compound of formula {[Cu₄(4,4′-bpy)₈(mal)₂(H₂O)₄](ClO₄)₂(H₂O)₄(CH₃OH)₂}_n (4,4′-bpy = 4,4′-bipyridine; mal = malonate dianion) has been prepared and structurally characterized by X-ray crystallography. This compound exhibits a novel three-dimensional network being composed of Cu-4,4′-bipyridine layers which are pillared by malonate bridge ligands. The copper(II) ions has two different coordination environment.     

Synthesis of azoles from 3,3′-[(4-alkoxyphenyl)imino]bis(propanoic acid hydrazides)

Abstract  

Reaction of 3,3′-[(4-alkoxyphenyl)imino]bis(propanoic acid hydrazides) with CS₂ in alkaline solution and subsequent acidification gave 5,5′-[[(4-alkoxyphenyl)imino]diethane-2,1-diyl]bis(1,3,4-oxadiazole-2(3H)-thiones). The same dihydrazides on reaction with phenyl isocyanates or phenyl isothiocyanates were converted to bis[N′-(phenylaminocarbonyl)propanoic acid hydrazides] and bis[N′-(phenylaminocarbonothioyl)propanoic acid hydrazides], which underwent cyclization in alkaline medium to produce 5,5′-[[(4-alkoxyphenyl)imino]diethane-2,1-diyl]bis(4-phenyl-2,4-dihydro-3H-1,2,4-triazol-3-ones) and their 3-thio analogues, whereas in sulfuric acid or POCl₃ 5,5′-[[(4-alkoxyphenyl)imino]diethane-2,1-diyl]bis(N-phenyl-1,3,4-oxadiazol-2-amines) and 5,5′-[[(4-alkoxyphenyl)imino]diethane-2,1-diyl]bis(N-phenyl-1,3,4-thiadiazol-2-amines) were obtained.     

Spectrophotometric study of some Mn(II) ternary complexes and their analytical applications

Abstract  

New ternary complexes of Mn(II) with py, bipy, and terpy as primary ligand (L₁) and 2′,4′,5′,7′-tetraiodofluorescein (I₄FlCOOH) as secondary ligand (L₂) were prepared. The stoichiometry for these complexes was found to be Mn(II):L₁:L₂ = 1:2:1, and the complex formula proposed is [Mn(L₁)₂(I₄FlCOO)]⁺. The effect of substituent groups of L₂ and the nitrogen atoms of L₁ on complex formation with Mn(II) was studied. Moreover, the interference of some cations and anions in the determination of Mn(II) by this method was investigated and the interferences of Cu(II) and Fe(III) with Mn(II) in their corresponding alloys were considered. A simple, rapid, and sensitive spectrophotometric method for determination of Mn(II) in its salts and Mn in its alloys is suggested.     

Benzenedicarboxylate-modulated zinc(II)-3,5-bis(3-pyridyl)-1H-1,2,4-triazole frameworks: syntheses, structures and luminescent properties

Abstract  

Based on the polydentate ligand 3,5-bis(3-pyridyl)-1H-1,2,4-triazole (3,3′-Hbpt), three coordination compounds [Zn(3,3′-Hbpt)(ip)]·2H₂O (1), [Zn(3,3′-Hbpt)(5-NO₂-ip)]·H₂O (2), and [Zn(3,3′-Hbpt)₂(H₂pm)(H₂O)₂]·2H₂O (3) have been hydrothermally constructed with H₂ip, 5-NO₂-H₂ip and H₄pm as auxiliary ligands (H₂ip = isophthalic acid, 5-NO₂-H₂ip = 5-NO₂-isophthalic acid, H₄pm = pyromellitic acid). Structural analysis reveals that Zn(II) ions serve as four-coordinated, five-coordinated, and six-coordinated connectors in 1–3, respectively, while 3,3′-Hbpt adopts μ-N_py and N_py coordination modes in two typical conformations in these target coordination compounds. Dependently the applied ligand, compounds 1–3 exhibit either 1D channel, cage or chain structures, respectively. In addition, the luminescence properties of 1–3 have been investigated in the solid state at room temperature.     

Synthesis, crystal structure and properties of a new organic-inorganic hybrid Dawson-like polyoxotungstate [Co(2,2''''-bpy)3]2[Co(2,2''''-bpy)2Cl][Co(2,2''''-bpy)2]H2-[SbW18O60]·4H2O

A new organic-inorganic hybrid polyoxometalate based on Dawson-like polyoxotungstate anion [SbW18O60]9-, formulated [Co(2,2'-bpy)3]2[Co(2,2'-bpy)2Cl][Co(2,2'-bpy)2]H2[SbW18O60]·4H2O (2,2'-bpy= 2,2(-bipyridine) has been synthesized from Sb2O3, Na2WO4, CoCl2, and 2,2'-bipyridine materials by hydrothermal method, and which was characterized by elemental analyses, IR, XPS, EPR, TG, and X-ray single crystal diffraction. Structure analysis shows that the polyoxoanion self-assembled under hydrothermal conditions consists of a Dawson-like polyoxotungstate cluster anion [SbW18O60]9- encapsulating a pyramidal {SbO3} group within the {W18} cluster cage. EPR spectra show that the high-spin octahedral CoⅡ and low-spin CoⅡ ions coexist in the title compound. Magnetic properties indicate that the compound is antiferromagnetic.     

A convenient synthetic route from isatin N-Mannich bases to nitrogen-containing derivatives of isoindigo

Abstract  

The reaction of aminomethylisatins (isatin N-Mannich bases) with hexaethylphosphorous triamide leads to the formation of 1,1′-bis(dialkylaminomethyl)-3,3′-bis(indolin-3-ylidene)-2,2′-diones and 1,1′-bis(1,3-dioxo-1,3-dihydroisoindol-2-ylmethyl)-1H,1′H-[3,3′]bisindolylidene-2,2′-dione.     

Mesogenic and magnetic behavior in cobalt(II) and iron(II) compounds with long alkyl chains

Abstract  Metal complexes with long alkyl chains [Co(C16-terpy)₃](BF₄)₂ (1), [Fe(C16-terpy)₂](BF₄)₂ (2), [Co(C16-terpy)₂](BPh₄)₂ (3), [Co(C14-terpy)₂](BF₄)₂ (4), and [Fe(C12C10C5-terpy)₂](BF₄)₂ (5) were synthesized and their physical properties characterized, where C16-terpy, C14-terpy, and C12C10C5-terpy are 4′-hexadecyloxy-2,2′:6′,2′′-terpyridine, 4′-tetradecyloxy-2,2′:6′,2′′-terpyridine, and 4′-5′′′-decyl-1′′′-heptadecyloxy-2,2′:6′,2″-terpyridine, respectively. Complexes 1, 2, and 5 exhibited liquid–crystal properties in the temperature ranges of 371–528 K and 466–556 K, and 88–523 K, respectively. Variable-temperature magnetic susceptibility measurements revealed that the Co(II) complexes 1 and 4 exhibited unique spin transitions (T _1/2↓ = 217 K and T _1/2↑ = 260 K for 1 and T _1/2↓ = 250 K and T _1/2↑ = 307 K for 4), so-called ‘reverse spin transition,’ induced by structural phase transitions. Complex 3 exhibited gradual spin-crossover behavior (T _1/2 = 160 K.), and complex 5 exhibited spin transitions (T _1/2↑ = 288 K and T _1/2↓ = 284 K) at the liquid crystal transition temperature. Compounds with multifunction, i.e., magnetic and liquid–crystal properties, are important in the development of molecular materials. Graphical Abstract  

Ruthenium-mediated Selective Aromatic Thiolation in the Complex [RuII{o-S—C6H4-(p-R-)—N=N—C3H2NN(1)—R′}2]. Synthesis, Spectroscopic, e.p.r., Electro-chemical Characterization and Spectro-electrochemical Correlation

The reaction of ctc-[Ru(RaaiR′)₂Cl₂] (3a–3i) [RaaiR′=1-alkyl-2-(arylazo)imidazole, p-R—C₆H₄—N=N— C₃H₂NN(1)—R′, R=H, OMe, NO₂, R′=Me, Et, Bz] with KS₂COR′′ (R′′=Me, Et, Pr, Bu or CH₂Ph) in boiling dimethylformamide afforded [Ru^II{o-S—C₆H₄(p-R-)—N=N—C₃H₂NN(1)—R′}₂] (4a–4i), where the ortho-carbon atom of the pendant phenyl ring of both ligands has been selectively and directedly thiolated. The newly formed tridentate thiolate ligands are bound in a meridional fashion. The solution electronic spectra exhibit a strong MLCT band near 700 nm and near 550 nm, respectively in DCM. The molecular geometry of the complexes in solution has been determined by H n.m.r. spectroscopy. Cyclic voltammograms show a Ru(II)/Ru(III) couple near 0.4 V and an irreversible oxidation response near 1.0 V due to oxidation of the coordinated thiol group, along with two successive reversible ligand reductions in the range −0.80–0.87 V (one electron), −1.38–1.42 V (one electron). Coulometric oxidation of the complexes at 0.6 V versus SCE in CH₂Cl₂ produced an unstable Ru(III) congener. When R=Me the presence of trivalent ruthenium was proved by a rhombic e.p.r. spectrum having g₁=2.349, g₂=2.310.     

Stability constants of the Li+, Na+, H3O+, NH4+, Ag+, and K+ complexes of the cone conformer of tetraethyl p-tert-butyltetrathiacalix[4]arene tetraacetate in nitrobenzene saturated with water

Abstract  

From extraction experiments in the two-phase water–nitrobenzene system and γ-activity measurements, the stability constants of the tetraethyl p-tert-butyltetrathiacalix[4]arene tetraacetate (cone)·M⁺ complexes (M⁺ = Li⁺, H₃O⁺, NH₄ ⁺, Ag⁺, or K⁺) were determined in water-saturated nitrobenzene. It was found that these constants increase in the cation order NH₄ ⁺ < K⁺ < H₃O⁺ < Ag⁺ < Li⁺ < Na⁺.     

Novel and chemoselective one-pot synthesis of 4-arylidene-2-phenyl-5(4H)-oxazolones starting from benzyl alcohols promoted by [(C14H24N4)2W10O32]-[bmim]NO3

Abstract  

A new and practical promoter system for one-pot, efficient, chemoselective synthesis of 4-arylidene-2-phenyl-5(4H)-oxazolones using [(C₁₄H₂₄N₄)₂W₁₀O₃₂]-[bmim]NO₃ under solvent-free conditions is described. The present work opens up a new and ecofriendly synthetic route to Erlenmeyer–Pl?chl adducts from primary benzyl alcohols in a one-pot operation.     

Phase equilibria in the Tl2Te-SnTe-Bi2Te3 system

phase equilibria in the Tl₂Te-SnTe-Bi₂Te₃ system were studied by differential thermal analysis (DTA), X-ray powder diffraction, and microhardness measurements. Some polythermal sections and isothermal (at 600 and 800 K) sections of the phase diagram and a projection of the liquidus surface were constructed. It was shown that the system is characterized by the formation of solid solutions with the Tl₅Te₃ structure (δ) and solid solutions based on SnTe (γ₁), Tl₂Te (α), Bi₂Te₃ (β), and two TlBiTe₂ (γ₂ and γ′₂) phases. Their homogeneity regions were determined. The liquidus surface consists of the primary crystallization fields of the β-, γ₁-, γ′₂-, and δ phases and the compounds SnBi₂Te₄ and SnBi₄Te₇. The liquidus of the α phase is degenerate. The primary crystallization fields of phases were determined, and the types and coordinates of in- and monovariant equilibria were found.     

Kinetics of Ag/TiO2-photocatalyzed iodide ion oxidation

Abstract  

Ag-doped TiO₂ (anatase) samples (mass fraction w _Ag = 0.01 and w _Ag = 0.02) of 15.9 and 14.5 nm mean particle size and 11.46 and 10.14 m² g⁻¹ BET surface area were prepared by photodeposition. Doping results in surface plasmon resonance of the metallic silver nanoclusters at around 500 nm, but the absorption edge remains unaltered at 365 nm. Ag-doping remarkably enhances the photooxidation of iodide ion under UV light; iodine formation with Ag/TiO₂ with w _Ag = 0.01 is 16 times greater than with bare TiO₂. The reaction conforms to Langmuir–Hinshelwood kinetics with regard to both I⁻ and O₂. Increase of pH slows down iodine formation and sacrificial electron donors arrest the reaction. Pre-sonication of the catalyst slurry hinders the photocatalysis. Generation of iodine is much greater in acetonitrile than in water. Under the experimental conditions, Ag/TiO₂ with w _Ag = 0.01 is more efficient than Ag/TiO₂ with w _Ag = 0.02, and the enhanced photocatalysis is likely to be because of suppression of electron–hole pair recombination. Kinetic analysis reveals that increasing the Ag mass fraction from 0.01 to 0.02 enhances the surface pseudo-first-order rate constant but inhibits the adsorption of iodide ion and the oxygen molecule on the illuminated oxide surface.