Synthesis,characterization, and reactivity of a novel ruthenium carbonyl cluster containing tri-O-benzyl-d-glucal as a chiral carbohydrate ligand

A chiral carbohydrate ligand 3,4,6-tri-O-benzyl-d-glucal (L) reacts with the cluster triruthenium dodecacarbonyl Ru₃(CO)₁₂ giving a novel chiral cluster Ru₃(μ-H)₂(CO)₉(L-2H) (I) that shows fluxional behavior at room temperature. The reaction of Ru₃(μ-H)₂(CO)₉(L-2H) (I) with triphenylphosphine and diphenylphosphinoethane (dppe) gives two new clusters Ru₃(μ-H)₂(CO)₇(L-2H)(PPh₃)₂ (II) and Ru₃(μ-H)₂(CO)₇(L-2H)(dppe) (III). The new compounds I, II and III have been characterized by a combination of elemental analysis, mass spectrometry, infrared and variable temperature NMR spectroscopy.     

Toward n-channel organic thin film transistors based on a distyryl-bithiophene derivatives

Solution and solid-state properties of two new perfluoroalkyl end-substituted analogues of distyryl-bithiophene (CF₃-DS2T and diCF₃-DS2T) are presented. Vacuum deposited thin films were investigated by atomic force microscopy, X-ray diffraction, and implemented as active layers into organic thin film transistors. While physicochemical measurements in solution suggest a preferential hole injection and transport inside CF₃-DS2T and diCF₃-DS2T films, electrical measurements performed under high vacuum show that CF₃-DS2T behaves as n-type semiconductor while no charge transport was measured in diCF₃-DS2T. The results highlighted the importance of substituents on conjugated backbone and on the resulting fine ordering in solid state to control the charge transport.     

Dipole-dipole transfer between acetone solvates of chlorophyll a and chlorophyll a dihydrate dimers in water/acetone mixtures. A model for P680 sensitized excitation

We describe a simple model for P680 sensitized excitation in photosynthesis. Chl a fluorescence quenching effects observed when water is added to Chl a solutions in acetone are shown to be the result of resonant transfer between acetone solvates of monomeric Chl a, Chl a·Ac, and dimers of Chl a dihydrate. The presence of (Chl a·2H₂O)₂ is evidenced by a 678 nm difference absorbance (ΔA band obtained on conversion of a 680 nm absorption shoulder to polycrystalline Chl a precipitate, (Chl a·H₂O)_n. The equilibration between (Chl a·2H₂O)₂ and Chl a·Ac as a principal mechanism for Chl a·Ac fluorescence quenching is supported by theoretical fits of the data.     

Facial coordination of cyclooctatetraene to a Co2Ni triangle in a heterometallic trinuclear cluster complex

Reaction of [(η-C₅H₅)NiCo₃(CO)₉] (5) with 1,3,5,7-cyclooctatetraene or 1,4-(SiMe₃)₂C₈H₆, respectively, yields the complexes [Co₂Ni(CO)₆(μ₃-η⁸-C₈H₆R₂)] (R=H, SiMe₃) (7a, b). Dramatic modifications of the tetrametallic cluster core and the ligand sphere of 5 to give the trinuclear complex 7 are driven by the preference of the cyclopolyenes for facial (μ₃-η⁸) coordination. The title complexes are the first examples of facial cyclooctatetraene coordination to a heterometallic (Co₂Ni) triangle.     

Activation of a dienediyne model of neocarzinostatin chromophore through an acid mediated solvolysis. Evidence for a new cyclization mode of enyne[3]cumulenes

When treated with 0.1 equiv. of triflic acid, a solution of the Z-configurated dienediyne 19 in a 2:3 mixture of tert-BuSH and CH ₂Cl₂ furnished the brightly yellow enyne[3]cumulene 20 through a S_N-reaction. 20 reacted at room temperature through a Saito-Myers cyclization to the substituted styrenes 31 and 24 and through an unprecedented cycloisomerization to the anthracene 25.     

Photochemical and thermal rearrangements of a benzoylnaphthobarrelene-like system

8-Benzoyl-9-deuterionaphtho[de-2.3.4]bicyclo[3.2.2]nona-2,6,8-triene (12a)rearranges in a photochemical di-π-methane-type process to the l-benzoylatho[de-[2.3.4]tricyclo[4.3.0.0^2,9]nona-3,7-dienes 14a-c.The dihydro derivate 13a and the hydroxypheoylmethyl analogs 21a and 22a undergo similarly regioselective rearrangements to 15a+c, 23a-c, and 24a, respectively. At 298 K the primary photoreaction directly occus from the S₁(n,π^*) and T₂(n,π^*) states, and it proceeds from T₁(π,π^*) and from S₂(π,π^*) either directly or via T₂. At lower temperature on direct irradiation. S₁→T intersystem crossing and triplet reaction compete with reaction from the singlet. The rearrangement 12a→14a-c proceeds along three reaction paths evolving from the two primary photochemical processes of naphthyl-vinyl and vinyl-vinyl bonding in β-position to the CO (12→25+29). Two ground-state triplet diradical intermediates such as 25 and 27 have been shown to intervene consecutively—for the first time in di-π-methane photochemistry. Each has been characterized by ESR and IR, and the second one additionally by fluorescence and fluorescence excitation, and by laser flash photolysis.The failure of products 14a-c to interconvert photochemically is ascribed to efficient energy dissipation through thermally reversible pbotocleavage of the 3-membered ring.Compounds 12 and 14 thermally interconvert in the dark which constitutes the first example of a ground-state counterpart of a di-π-methane photorearrangement. The thermal reaction includes a path with highly regioselective (and possibly concerted) product formation competing with a stepwise process causing positional scrambling. The sequence 12→14 (photochemically; Φ = 1.0 at 366 nm and 298 K) and an electrophile-catalyzed reversal 14→12 in the dark is a model of a chemical light energy storage cycle which can be conducted without loss of reactants.     

Unexpected conversion of a polycyclic thiophene to a macrocyclic anhydride

Oxygenation of 2,5,9,12-tetra(tert-butyl)diacenaphtho[1,2-b:1′,2′-d]-thiophene (1, C₄₀H₄₄S) by peracids gave the cyclic sulfonic ester 4 (2,7,10,13-tetra(tert-butyl)diacenaphtho[1,2-c:1′,2′-e]oxathiin 5,5-dioxide, C₄₀H₄₄O₃S) which, when heated in nitrobenzene, is converted into a complex, macrocyclic anhydride 3 (C₈₀H₈₈O₃), which is derived from two molecules of 4. Further investigation found a likely intermediate in this reaction, 4,4′,7,7′-tetra(tert-butyl)-1,1′-biacenaphthylenylidene-2,2′-dione (5, C₄₀H₄₄O₂), apparently formed from 4 by additional oxidation. Anhydride 3 plausibly arises by Diels-Alder reaction of 4 and 5 followed by several ring fragmentations. The structures of 3, 4, and 5 were unambiguously established by X-ray crystallography.     

Facile cleavage of a phenyl group from SbPh3 by dirhenium carbonyl complexes

The complex Re₂(CO)₈[μ-η²-C(H)C(H)Buⁿ](μ-H) (1) reacts with SbPh₃ at 68 °C to yield the new σ-phenyl dirhenium complex Re₂(CO)₈(SbPh₃)(Ph)(μ-SbPh₂) (4) in 72% yield. Compound 4 contains two rhenium atoms held together by a bridging SbPh₂ ligand. One rhenium atom contains a σ-phenyl group. The other rhenium atom contains a SbPh₃ ligand. Compound 4 was also obtained in 34% yield from the reaction of Re₂(CO)₁₀ with SbPh₃ in the presence of UV–Vis irradiation together with some monorhenium products: HRe(CO)₄SbPh₃ (5), Re(Ph)(CO)₄SbPh₃ (6) and fac-Re(Ph)(CO)₃(SbPh₃)₂ (7) in low yields. Complex 4 is split by reaction with an additional quantity of SbPh₃ to yield the monorhenium SbPh₃ complexes 6, 7 and mer-Re(Ph)(CO)₃(SbPh₃)₂ (8) that contain a σ-phenyl ligand. When 4 was treated with hydrogen, the phenyl ligand was eliminated as benzene and the dirhenium complexes Re₂(CO)₈(μ-SbPh₂)(μ-H) (10), and Re₂(CO)₇(SbPh₃)(μ-SbPh₂)(μ-H) (11), were formed that contain a bridging hydrido ligand. The doubly SbPh₂-bridged dirhenium complex Re₂(CO)₇(SbPh₃)(μ-SbPh₂)₂ (9) that has no metal–metal bond was also formed in these two reactions.     

Chirality sensing of saccharides using a boronic acid-appended chiral ferrocene derivative

A diboronic acid-appended chiral ferrocene derivative (R)-9 was designed and synthesized. This chiral ferrocene scaffold was obtained by resolution of the diastereomer with a monosaccharide derivative. One can therefore expect that (R)-9 would show d/l selectivity for specific monosaccharides. The complex formation of (R)-9 with various saccharides using the two boronic acid functions was conveniently monitored by a change in the circular dichroism (CD) spectra. The CD spectral change (Δ[θ]) induced by added monosaccharides was chiroselective: in particular, d/l-alloses and d/l-galactoses induced the 8.0- and 7.0-fold difference in the magnitude of the CD spectral change. The association constants for d- and l-saccharides (K_D and K_L, respectively) were determined: among them, (R)-9 showed a significant discrimination ability for mannose (K_L/K_D=2.6) and arabinose (K_L/K_D=1/2.4). The origin of d/l selectivity was discussed on the basis of computational studies on (R)-9·saccharide complexes.     

Evidence for a protophosphatase catalysed cleavage of adenosine triphosphate by a dissociative-type mechanism within a receptor-substrate complex

Analogues of ATP and diadenosine 5′,5″′-P₁,P₄-tetraphosphate, Ap₄A, have been used to explore the specificity and mechanism of the proto-ATPase activity of the macrocyclic polyamine [24]-N₆O₂ (1). The results show that (1) has exonuclease-like activity and support a mechanism that is dissociative in character within a pre-associative scheme resulting from receptor-substrate binding.     

Synthesis and the crystal structures of a monoanionic tetrafluorodentate ligand and its complex with lanthanum ion

New organotitanium fluorides [Hdmpy]⁺[(C₅Me₄R)₂Ti₂F₇]⁻ (R=Me 4, Et 5, dmpy=2,6-dimethylpyridine, lutidine) have been prepared from (C₅Me₄R)TiF₃ and 2,6-dimethylpyridine·(HF)₂. The compounds 4 and 5 react with La(CF₃SO₃)₃ to give [La{(C₅Me₄R)₂Ti₂F₇}₃] (R=Me 6, Et 7) containing the [(C₅Me₄R)₂Ti₂F₇]⁻ anion as a tetrafluorodentate ligand in the crystal structures of 4 and 7. The cation–anion pair is connected by a hydrogen bond in 4 and the all-fluorine environment of 12 fluorine atoms coordinated to a lanthanum ion is found in 7.     

Incorporation of a tripodal ligand with a (N,O,O)-donor set into a new family of nickel and cobalt spin clusters

The reaction of Ni(OAc)₂, NiX₂ (X = Cl, Br) or CoCl₂ with the proligand 2-amino-2-methyl-1,3-propanediol (ampdH₂) affords a new family of tetranuclear complexes. The syntheses of [Ni₄(OAc)₄(ampdH)₄] (1) and [M₄X₄(ampdH)₄] (M = Ni, X = Cl, 2; M = Ni, X = Br, 3; M = Co, X = Cl, 4) are reported, together with the single crystal X-ray structures of 1, 2 and 4 and the magnetochemical characterization of 1, 3 and 4. Each member of this family of complexes displays a low symmetry structure that incorporates a {M₄O₄} core unit based on a distorted cubane. Magnetic measurements reveal ferromagnetic exchange interactions for 1, 3 and 4. These give rise to S = 4 ground state spins for the tetranuclear Ni complexes and an anisotropic effective S′ = 2 ground state for the Co complex.     

Synthesis and structure of a chiral areno-bridged [2.4]metacyclophane

The reductive coupling reaction of 1,4-bis(3-acetyl-5-tert-butyl-2-methoxyphenyl)butane 3 was carried out using TiCl₄-Zn in pyridine followed by a McMurry coupling reaction to afford the compounds anti and syn 1,2-dimethyl[2.4]MCP-1-ene 4. Bromination of 4 with BTMA-Br₃ in dry CH₂Cl₂ afforded the interesting compound 1,2-bis-(bromomethyl)-5,15-di-tert-butyl-8,18-dimethoxy[2.4]MCP-1-ene 6 and consecutive debromination with Zn and AcOH in CH₂Cl₂ solution afforded the stable solid 5,15-di-tert-butyl-8,18-dimethoxy-1,2-dimethylene[2.4]MCP 7 in 89% yield. Compound 7 was conveniently employed in a Diels–Alder reaction with dimethyl acetylenedicarboxylate (DMAD) to provide 2-(3′,6′-dihydrobenzo)-5,15-di-tert-butyl-8,18-dimethoxy[2.4]MCP-4′,5′-dimethylcarboxylate 8 in good yield. Diels–Alder adduct 8 was converted into a novel and inherently chiral areno-bridged compound [2.4]MCP 9 by aromatization. The chirality of the two conformers was characterized by circular dichroism (CD) spectra of the separated enantiomer which are perfect mirror images of each other.     

1,8-Diazabicyclo[5.4.0]undec-7-ene as a ligand in an intermediate in selective carbonyl substitution of a ruthenium-cobalt complex

1,8-Diazabicyclo[5.4.0]undec-7-ene, DBU, reacts with (OC)₄Ru(μ-PPh₂)Co(CO)₃ (1) at room temperature to give an intermediate 2, which on protonation in the presence of Co regenerates 1 and on protonation in the presence of PMe₃, gives the monosubstituted product (OC)₃(L)Ru(μ-PPh₂)Co(CO)₃ (3 L = PMe₃). DBU promotes the selective formation of 4(L = PPh₂Me) or 5 (L = Ph₂PCh₂C(Me)CH₂) in one-step from 1, Ph₂PH, and methyl iodide or methallyl chloride, respectively.     

Novel skeletal rearrangements of a diterpene derived from deltaline

Treatment of imines 5 and 7, both prepared from the C₁₉-diterpenoid alkaloid deltaline (1), with NaNO₂–HCl resulted in the formation of diterpene 6 with an eight-membered ring through a sequence of denitrogenation and enlargement of ring B. In addition, two unusual skeletal rearrangements of diterpene 6 were also observed, leading to two structurally novel products 8 and 10. The structures of compounds 8 and 10 were confirmed by their X-ray crystallographic analyses and 2D NMR data.     

The loading of polyoxometalates based compound on reduced graphene oxide,a composite material for electrical energy storage and tetracycline removal

A polyoxometalate based composite material (NiPW₁₂NP/FrGO) was synthesized successfully, in which the nanoparticle of a polyoxometalate compound (NiPW₁₂NP) distributes on carboxylate group functionalized reduced graphene oxide (FrGO) homogenously. There exist intensive chemical bonds between NiPW₁₂NP and FrGO, which guarantees the stability of this composite material. When employed as a cathode material, NiPW₁₂NP/FrGO exhibits high specific capacitance, remarkable rate capability and long-term stability. When the current density is 4 A g⁻¹, a specific capacitance as high as 437.6 F g⁻¹ is achieved by NiPW₁₂NP/FrGO. With NiPW₁₂NP/FrGO serving as cathode and MnO₂ acting as anode, a high performance asymmetric supercapacitor (ASC) is assembled, which possesses a high energy density of 12.96 W h·kg⁻¹ at 0.67 kW kg⁻¹. It also shows a good rate capability, when the current density increases from 4 to 12 A g⁻¹, its specific capacitances decreases from 115.2 to 90.9 F g⁻¹, with 78.9% capacitance retention. After 5000 cycles charge-discharge experiments, 94.3% of its capacitance can be maintained, which exhibits good stability. Furthermore, NiPW₁₂NP/FrGO composite material also shows excellent tetracycline adsorption ability with capacity 288.28 mg g⁻¹, the adsorption can be well described with Temkin model, which suggests electrostatic attraction dominates the adsorption process.     

Multiple hydrogen-bond-induced supramolecular nanostructure from a pincer-like molecule and a [60]fullerene derivative

A new supramolecular self-assembled system between a perylene bisimide bearing diaminopyridine-substituted isophthalamide groups (PP) and a [60]fullerene containing barbituric acid moiety (C₆₀bar) through a complementary six-point hydrogen-bonding interaction was constructed. The formation of hydrogen bonding was confirmed by ¹H NMR spectra studies in CDCl₃. Fluorescence quenching experiments indicated that the fluorescence of PP was greatly quenched by the hydrogen-bonded C₆₀bar (K_sv=2.71×10⁴ M⁻¹). A steady and rapid cathodic 0.15 μA cm⁻² photocurrent response of the PP/C₆₀bar film deposited onto an ITO electrode was produced under the irradiation of 20 mW cm⁻² white light, indicating the presence of photo-induced electron transfer between PP and C₆₀bar. TEM images showed that spherical particles were fabricated by the self-assembly of PP and C₆₀bar through hydrogen-bonding interaction.     

Partial synthesis of isoeucommiol,a new cyclop entenoid-tetrol

Isoeucommiol 3, a cyclopentenoid-tetrol isomer of eucommiol 1, has been prepared by NaBH₄ reduction of the hemiacetal moiety of aucubigenin 4a. The mechanism of this reduction has been investigated by using NaBD₄.     

New dimeric and supramolecular organotin(IV) complexes with a tridentate schiff base as potential biocidal agents

The paper describes the synthesis and structural characterization of six new diorganotin(IV) compounds 1–6, [R₂SnL] and a monoorganotin(IV) derivative, C₄H₉SnClL (7). Here L = N′-(5-bromo-2-oxidobenzylidene)-N-(oxidomethylene)hydrazine ligand with ONO tridentate chelation capability and R = CH₃ (1), C₂H₅ (2), n-C₄H₉ (3), C₆H₅ (4), C₈H₁₇ (5), tert-C₄H₉ (6), The packing diagram offers a supramolecular structure for 1 and a dimeric structure for 4 with distorted square-pyramidal and distorted trigonal geometry, respectively. The different geometry of 1 than 4 can be attributed to the presence of intermolecular non-covalent Sn---O and Sn---H interactions in the former. The antifungal, antibacterial, antiurease and antileishmanial activities of these complexes proved them to be active biologically and may be formulated as new metal-based drugs in future.     

Synthesis and structure of a tungsten dichlorosilyl dihydride complex

The reaction of the donor-stabilized silylene complex cis-Cp¹(CO)₂(H)WSiHPh · THF (3, Cp¹ = η⁵-C₅Me₅) with LiAlH₄ followed by the protonation of the resulting Li[Cp¹(CO)₂W(H)(SiH₂Ph)] (4) with excess CF₃COOH afforded the trihydride complex Cp¹(CO)₂WH₃ (6). The structure of 6 was characterized using variable-temperature NMR studies and X-ray crystal analysis. Deprotonation of 6 with KH gave the anionic dihydride complex K[Cp¹(CO)₂WH₂] (7), which was converted into the dichlorosilyl dihydride complex Cp¹(CO)₂W(H)₂(SiHCl₂) (8) on treatment with trichlorosilane. The X-ray crystal analysis of 8 revealed that it adopts a distorted pseudo-octahedral structure with a short W–Si bond, long Si–Cl bonds, and short contacts between the hydrides and silicon atom. Along with these structural features, the conformation of the silyl ligand around the W–Si bond may suggest the presence of a double interligand hypervalent interaction between the dichlorosilyl and hydrides ligands.