Coordination-driven self-assemblies with a carborane backbone

The design and self-assembly of five new supramolecular complexes (a rectangle, a triangle, a hexagon, and two squares) are described. These assemblies incorporate carborane building blocks and were prepared in excellent yields (>85%). The assemblies and building blocks were characterized with multinuclear NMR spectroscopy, electrospray ionization mass spectrometry, and elemental analysis. Isotopically resolved mass spectrometry data confirm the existence of the rectangle, triangle, and hexagon, and NMR data are consistent with the formation of all five assemblies. The X-ray structures of two linear carborane building blocks, 1,12-(4-CC(C(5)H(4)N)(2)-p-C(2)B(10)H(10) (1) and 1,12-(trans-(Pt(PEt(3))(2)I)CC)(2)-p-C(2)B(10)H(10) (2), are reported: 1 is monoclinic, P2(1)/c, a = 10.6791(4) A, b = 8.0091(14) A, c = 11.6796(4) A, beta = 107.8461(15) degrees , V = 950.89(5) A(3), Z = 2; 2 is monoclinic, C2/c, a = 62.1128(10) A, b = 22.0071(3) A, c = 14.0494(2) A, beta = 89.9411(8) degrees , V = 19204.4(5) A(3), Z = 16. Crystals of the linear linker 1 exhibit close pi-pi pyridine and pyridine-B(carborane) interactions, which are discussed.     

Aggregate of a peptide-containing block copolymer with a lipase

The peptide-containing block copolymer poly(N-acetyliminoethylene)-block-poly(L -phenylalanine) (1) formed large water-soluble aggregates in water due to the hydrophobic and hydrogen-bonding character of the poly(L -phenylalanine) block. The solution properties of 1 were compared with those of the block copolymer poly(N-acetyliminoethylene)-block-poly(N-benzoyliminoethylene) (2) with an analogous structure. 1 formed aggregates even though the poly(phenylalanine) segment was short as compared with 2 in which hydrophobic interaction may be the only driving force to form aggregates. The aggregates have strong capability of incorporating Lipase P and largely increase the hydrolysis activity against p-nitrophenyl propionate as compared with that of free Lipase P.     

Metallohosts with a heart of carbon

Single-crystal X-ray diffraction studies have confirmed that Ni(3)S(3)-based molecular bowls prepared in one-pot reactions capture either CH(2)Cl(2) or C(60). The nature of the pendant substituents (naphthalen-2-ylmethyl, benzyl, or ethyl) around the rim of the bowl dictates the formation of a 1:1 (bowl host-C(60) guest) or 2:1 (capsule host-C(60) guest) architecture. In CDCl(3), the trimeric complexes were found to be in equilibrium with dimeric analogues. For the naphthalen-2-ylmethyl-substituted host, NMR spectroscopic titration data confirmed a 1:1 host-C(60) guest complex in 1,2-Cl(2)C(6)D(4) solution.     

Anion binding with a tripodal amine

Binding studies of the tren-based amine, L (N,N',N' '-tris(2-benzylaminoethyl)amine), with inorganic anions and two crystal structures, [H(3)L][H(2)PO(4)](3).H(3)PO(4) and [H(3)L][Br](3), are reported. NMR titration results indicate that the ligand binds H(2)PO(4)(-) and HSO(4)(-) more strongly than NO(3)(-) and halides. In the crystal structure of the phosphate complex, the ligand is triprotonated with the three arms pointing outward in a trigonal-planar-like arrangement. Four phosphate species are associated with the receptor, and have been assigned as three H(2)PO(4)(-) counterions located between each of the tren arms, and an additional H(3)PO(4) molecule above the quasi-planar tren. The structure of the bromide complex is slightly different, although again the tren receptor is triprotonated and quasi-planar, but in this case C(2v)-like symmetry is seen with two of the arms pointed in the same direction with a bromide ion in between. The other two bromides lie outside of the tren arms.     

Electrophoresis of a biocolloid covered with a cation-absorptive membrane

The electrophoretic behavior of a biocolloid covered with a charged membrane is theoretically analyzed in the present study. Here, the influences of nonuniformly distributed fixed groups, absorption of cations by fixed original functional groups, variation in dielectric constant in the electrophoretic system, and ionic sizes are considered. The results of numerical simulation suggest that a larger absolute value of the electrophoric mobility of biocolloids could be generated by larger membrane electricity. The absolute value of the electrophoric mobility for the nonlinear distribution of the fixed groups is larger than that for the linear distribution of the fixed groups. The absolute value of the electrophoric mobility increases with (1) the concentration of total fixed groups, (2) the cation-absorption equilibrium constant, (3) the nonuniform feature index for functional-groups distribution, (4) the dielectric constants of the inner uncharged membrane zone for only mobile cationic charge and for both mobile cationic and anionic charge, and (5) the effective size of the cations. An increase in the absolute value of the electrophoric mobility can also be resulted from a decrease in the following parameters: (1) the friction coefficient of the biocolloidal membrane phase, (2) the membrane thickness, (3) the dielectric constant of space for all charge and of outer uncharged membrane zone, (4) the effective sizes of anions and fixed groups, and (5) the number of cations and the fixed original functional groups involved in the formation of a cation-functional group complex.     

Zeolite-like nitride-chlorides with a predicted topology

We describe the synthesis and structures of the first tantalum-containing nitride-chlorides, Ba(3)Ta(3)N(6)Cl and Ba(15)Ta(15)N(33)Cl(4), and the structurally related Ba(3)Si(3)N(5)OCl, and their relationship with a theoretical silaceous framework.     

Synthesis of a bimetallic platinum-tungsten complex with a bridging micro-diboranyl-oxycarbyne moiety

The novel bimetallic micro-diboranyl-oxycarbyne bridged platinum-tungsten complex [W{eta(1),micro-CO-B(NMe(2))-B(NMe(2))-(eta(5)-C(5)H(4))}(CO)(2){Pt(PPh(3))(2)}] (W-Pt) () has been synthesised by a two-step reaction, starting from the dilithiated half-sandwich compound Li[W(eta(5)-C(5)H(4)Li)(CO)(3)] () via the ansa-diboranyl-oxycarbyne tungsten complex [W{eta(1)-CO-B(NMe(2))B(NMe(2))(eta(5)-C(5)H(4))}(OC)(2)] () by use of stoichiometric amounts of B(2)(NMe(2))(2)Br(2) and [Pt(eta(2)-C(2)H(4))(PPh(3))(2)], respectively.     

Radical cation of a trimethylenemethane with a nondegenerate ground state

Upon ionization by gamma-irradiation in frozen CFCl(3), or by X-irradiation in an Ar matrix, 2,2,3,3-tetramethylmethylenecyclopropane (MCP-Me4) readily undergoes ring opening to yield the radical cation of 1,1,2,2-tetramethyltrimethylenemethane (TMM-Me4). The hyperfine-coupling constants for TMM-Me4(.+) are (mT) -1.99 (2H), +0.53 (6H), and +0.19 (6H), and the singly occupied orbital closely resembles one of the two degenerate nonbonding pi-MOs (NBMOs) of trimethylenemethane (TMM). Due to the expected effect of the methyl substituents, this "symmetric" NBMO, psi(2+) (b(1)), is energetically favored relative to its "antisymmetric" counterpart, psi(2-) (a(2)), so that the ground state assumes a structure with (2)B(1) symmetry in the C(2v) point group. Calculations show that the ring opening in the primary radical cation MCP-Me4(.+) to yield TMM-Me4(.+) is spontaneous, whereas in the parent system (MCP(.+) --> TMM(.+) a low barrier does exist. In contrast to the previously investigated case of the radical cation of tetramethyleneethane, the "electromer" of TMM-Me4(.+), in which the unpaired electron occupies psi(2-), cannot be attained photochemically.     

Isoxazolidines with a cyclobutane link

N-(Phenacylidene)- and N-(arylaminooxoethylidene)aniline N-oxides form 11 adducts with methylenecyclobutane. The addition of the nitrones proceeds specifically and leads to substituted isoxazolidines in high yields. In the case of N-(phenylaminooxoethylidene)aniline N-oxide it was shown that 1-methylcyclobutene and bicyclobutylidene also undergo cycloaddition to give isoxazolidines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1316–1318, October, 1982.     

Phthalocyanine with a giant dielectric constant

Compound 1 has been prepared by the reaction of 4-nitrophthalonitrile and trans-2-methoxy-4-(2-nitrovinil)phenol by the common method of nucleophilic substitution of an activated nitro group in an aromatic ring. The metallophthalocyanines 2, 3 were prepared by the reaction of a dinitrile derivative with Co(OAc)(2) or Zn(OAc)(2) in DMSO. The lutetium bis-(phthalocyaninato) complex 4 was obtained by treating the dinitrile derivative with lutetium acetate and DBU in 1-hexanol. The new compounds were characterized by elemental analyses, FT-IR, (1)H-NMR, MALDI-TOF MS and UV/Vis spectral data. The spectroscopic data of the new compounds were in accordance with the structures. The temperature and frequency dependence of dielectric and conduction properties of the spin coated film of compounds (2-4) have been studied by fabricating metal-Pc-metal structures. The results show that compound 2 has giant dielectric constant. At a low range of frequency and room temperature, ε' is found to be equal to 2.33 × 10(6), 1.53 × 10(4) and 1.03 × 10(4) for 2, 3 and 4, respectively. The giant dielectric behavior of 2 is mainly attributed to Maxwell-Wagner polarization. The obtained results also indicated that the frequency dependence of the dielectric permittivity, ε'(ω), exhibits non-Debye type relaxation for all temperatures investigated. The ac conductivity results gave a temperature dependent frequency exponent s. The results were compared with the prediction of the Quantum Mechanical Tunneling and Correlated Barrier Hopping models.     

Coupling of a Nucleoside with DNA by a Methyltransferase

How to outwit a methyltransferase: Methyltransferases (Mtases) catalyze the transfer of the activated methyl group from the cofactor S-adenosyl-L -methionine ( 1 ) to acceptors R within a large variety of biomolecules. Through the use of the cofactor analogue 2 a whole nucleoside was coupled to DNA in a Mtase-catalyzed reaction.     

Denting Nanospheres with a Short Peptide

Dented nanospheres show promising potential in drug delivery,nanomotors,etc.However,it is still challenging to prepare them by homopolymer self-assembly because of the strict structural requirements of the homopolymer.Herein,we propose a strategy for preparing dented nanospheres from homopolymers by co-assembly with a short peptide.They were co-assembled from poly(2-hydroxy-3-((4-(ethoxycarbonyl)phenyl)amino)propyl methacrylate) (PHBzoMA59) and (S)-2-((S)-2-((((gH-fluoren-9-yl)methoxy)carbonyl)amino)-3-phenylpro-panamido)-3-phenylpropanoic acid (Fmoc-FF-OH).PHBzoMA homopolymers can only self-assemble into nanospheres without dent,and the addition of a short peptide introduced hydrogen bonding and complementary π-π stacking interactions led to the final dented nanosphere morphology.The weight fractions of the short peptide can be adjusted to regulate the final morphology.It was confirmed that the radius of curvature of the dent on the surface was related to the organic bubble inside the protospheres prepared at critical aggregation concentration(CAC).The organic bubble can be adjusted by altering the kind of organic solvent and solution pH,which allowed control over the dented nanosphere dimension.The use of different organic solvents with various polarities allows adjustment of the interfacial tension,and hence the denting degree.This degree can also be controlled by manipulating the solution pH to (de)protonate the short peptide and homopolymer.Furthermore,the versatility of this method was highlighted by using a different homopolymer and the applicability of the resulting dented nanospheres was demonstrated by decoration with gold nanoparticles.Overall,this study provided important insights and a new simple strategy to prepare dented nanospheres in a controlled fashion.     

Reactions of amines with a dimer of hexafluoropropene and with a perfluorovinyl sulfide prepared with hexafluoropropene

Some reactions of amines with a perfluorovinylsulfide, (CF₃)₂CFSC(CF₃)CFCF(CF₃)₂, prepared from hexafluoropropene (HFP) and sulfur [1] are compared to reactions of the same amines with the thermodynamic dimer of HFP, (CF₃)₂CCFCF₂CF₃. Many new ketenimines, eneamines, amidines, nitriles, and quinoline derivatives are reported.     

Reactions of a stable silylene with halocarbons

An unusual product formation is observed for the insertion reaction of the thermally stable silylene Si[(NCH(2)Bu(t))(2)C(6)H(4)-1,2][abbrev. as Si(NN)] into the carbon-halogen bond of alkyl or aryl halides RHal (Hal=Cl, Br). In general, depending on the halogen, the reaction either results in a disilane of type (NN)Si(Hal)-(R)Si(NN) for Hal=Cl or a mixture of disilane and the monosilane (NN)Si(R)(Hal) for Hal=Br. The results are put into context to previously suggested mechanisms. The disilane (NN)Si(Hal)-(R)Si(NN)(Hal=Cl or Br) is thermally labile and mild thermolysis yields the corresponding monosilane (NN)Si(R)(Hal) and silylene 1. Additionally, strong evidence is presented for a radical pathway for the reaction of 1 and RHal.     

Reductive activation of dioxygen by a myoglobin reconstituted with a flavohemin

We successfully converted myoglobin, an oxygen-storage hemoprotein, into an oxygen-activating hemoprotein like cytochrome P450s by replacing the native hemin with the artificially created flavohemin. The reconstituted myoglobin, rMb(1), was chacterized by ESI-TOF-mass, UV-vis, and fluorescence spectra. The 1H NMR spectrum of cyanomet rMb(1) indicates that two hemin conformers are present in a ratio of 1:1. Upon the addition of NADH to the buffer solution of rMb(1) in the presence of SOD and catalase, the oxymyoglobin was rapidly formed. As compared with the formation of the oxygenated native myoglobin in the presence of 10-N-(acetylaminoethyl)isoalloxazine, the rate constant of the oxyheme formation in rMb(1) is 6 times larger. This is because the flavin covalently linked to the terminal heme propionate functions as an effective mediator of an electron transfer from NADH to the hemin in rMb(1). Furthermore, rMb(1) shows the deformylation activity, when 2-phenylpropionaldehyde (2-PPA) was employed as a substrate. This result indicates that the oxyheme is reductively activated to Fe(III)-peroxoanion (Fe(III)-O22-). The result in this report is the first example of the activation of dioxygen by myoglobin. This study shows the utility of the replacement of the native hemin with a chemically modified one for the functionalization of myoglobin.     

Li-O2 battery with a dimethylformamide electrolyte

Stability of the electrolyte toward reduced oxygen species generated at the cathode is a crucial challenge for the rechargeable nonaqueous Li-O(2) battery. Here, we investigate dimethylformamide as the basis of an electrolyte. Although reactions at the O(2) cathode on the first discharge-charge cycle are dominated by reversible Li(2)O(2) formation/decomposition, there is also electrolyte decomposition, which increases on cycling. The products of decomposition at the cathode on discharge are Li(2)O(2), Li(2)CO(3), HCO(2)Li, CH(3)CO(2)Li, NO, H(2)O, and CO(2). Li(2)CO(3) accumulates in the electrode with cycling. The stability of dimethylformamide toward reduced oxygen species is insufficient for its use in the rechargeable nonaqueous Li-O(2) battery.     

Complexes of a gallium heterocycle with transition metal dicyclopentadienyl and cyclopentadienylcarbonyl fragments, and with a dialkylmanganese compound

The reactivity of several transition metal half sandwich complexes towards an anionic gallium(I) heterocyclic complex, [K(tmeda)][Ga{[N(Ar)C(H)]2}](Ar = C6H3Pri2-2,6), has been investigated. This has led to the anionic half sandwich complexes, [K(tmeda)][(C5H4R)M(CO)n[Ga{[N(Ar)C(H)]2}]](M = V, R = H, n= 3; M = Mn, R = Me, n= 2; M = Co, R = H, n= 1), which crystallographic studies show to form dimers (M = Mn and Co) or a polymer (M = V) through bridging potassium cations. The metal-gallium bond lengths in all complexes are very short which, combined with some spectroscopic evidence, is suggestive of M-Ga pi-bonding. Density functional theory studies of models of all complexes indicate that the level of back-bonding in these complexes is, however, minimal and of a similar order to that seen in analogous complexes incorporating neutral N-heterocyclic carbene ligands. Reactions of the metallocenes, [M(C5H4Me)2](M = V or Cr), with the digallane4, [Ga{[N(Ar)C(H)]2}]2, have afforded the neutral complexes, [M(C5H4Me)2[Ga{[N(Ar)C(H)]2}]], which are thought to be formed via an initial oxidative insertion of the transition metal centre into the Ga-Ga bond of the digallane. X-Ray crystallography shows the complexes to be monomeric. One (M = V) reacts with one equivalent of [K(tmeda)][Ga{[N(Ar)C(H)]2}] to give the crystallographically characterised, anionic bis(gallyl)-complex, [K(tmeda)][V(C5H4Me)2[Ga{[N(Ar)C(H)]2}]2]. For comparison, the reaction of [K(tmeda)][Ga{[N(Ar)C(H)]2}] with [Mn{CH(SiMe3)2}2] was carried out and gave the monomeric, anionic complex, [K(tmeda)][Mn{CH(SiMe3)2}2[Ga{[N(Ar)C(H)]2}]].     

Cocaine detection by a mid-infrared waveguide integrated with a microfluidic chip

A germanium (Ge) strip waveguide on a silicon (Si) substrate is integrated with a microfluidic chip to detect cocaine in tetrachloroethylene (PCE) solutions. In the evanescent field of the waveguide, cocaine absorbs the light near 5.8 μm, which is emitted from a quantum cascade laser. This device is ideal for (bio-)chemical sensing applications.     

Ester hydrolysis by a cyclodextrin dimer catalyst with a metallophenanthroline linking group

A novel beta-cyclodextrin dimer, 1,10-phenanthroline-2,9-dimethyl-bridged-bis(6-monoammonio-beta-cyclodextrin) (phenBisCD, L), was synthesized. Its zinc complex (ZnL) has been prepared, characterized, and applied as a new catalyst for diester hydrolysis. The formation constant (logK(ML)=9.56+/-0.01) of the complex and deprotonation constant (pK(a)=8.18+/-0.04) of the coordinated water molecule were determined by a potentiometric pH titration at (298+/-0.1) K. Hydrolytic kinetics of carboxylic acid esters were performed with bis(4-nitrophenyl) carbonate (BNPC) and 4-nitrophenyl acetate (NA) as substrates. The obtained hydrolysis rate constants showed that ZnL has a very high rate of catalysis for BNPC hydrolysis, giving a 3.89x10(4)-fold rate enhancement over uncatalyzed hydrolysis at pH 7.01, relative to only a 42-fold rate enhancement for NA hydrolysis. Moreover, the hydrolysis second-order rate constants of both BNPC and NA greatly increases with pH. Hydrolytic kinetics of a phosphate diester catalyzed by ZnL was also investigated by using bis(4-nitrophenyl) phosphate (BNPP) as the substrate. The pH dependence of the BNPP cleavage in aqueous buffer shows a sigmoidal curve with an inflection point around pH 8.11, which was nearly identical to the pK(a) value from the potentiometric titration. The k(cat) of BNPP hydrolysis promoted by ZnL was found to be 9.9x10(-4) M(-1) s(-1), which is comparatively higher than most other reported Zn(II)-based systems. The possible intermediate for the hydrolysis of BNPP, BNPC, and NA catalyzed by ZnL is proposed on the basis of kinetic and thermodynamic analysis.     

Gold Redox Catalysis with a Selenium Cation as a Mild Oxidant

Gold-catalyzed alkyne and allene diselenations were developed. Excellent regioselectivity (trans) and good to excellent yields were achieved (up to 98 % with 2 % catalyst loading) with a wide range of substrates. Mechanistic investigation revealed the formation of a vinyl gold(I) intermediate followed by an intermolecular selenium cation migration, suggesting that a gold(I/III) redox process was successfully implemented under mild conditions.