Chiral bisphosphinite metalloligands derived from a P-chiral secondary phosphine oxide

Interaction of PdCl(2)(MeCN)(2) with 2 equiv of (S(P))-(t)BuPhP(O)H (1H) followed by treatment with Et(3)N gave [Pd((1)(2)H)](2)(micro-Cl)(2) (2). Reaction of 2 with Na[S(2)CNEt(2)] or K[N(PPh(2)S)(2)] afforded Pd[(1)(2)H](S(2)CNEt(2)) (3) or Pd[(1)(2)H)[N(PPh(2)S)(2)] (4), respectively. Treatment of 3 with V(O)(acac)(2) (acac = acetylacetonate) and CuSO(4) in the presence of Et(3)N afforded bimetallic complexes V(O)[Pd(1)(2)(S(2)CNEt(2))](2) (5) or Cu[Pd(1)(2)(S(2)CNEt(2))](2) (6), respectively. X-ray crystallography established the S(P) configuration for the phosphinous acid ligands in 3 and 6, indicating that 1H binds to Pd(II) with retention of configuration at phosphorus. The geometry around Cu in 6 is approximately square planar with the average Cu-O distance of 1.915(3) A. Treatment of 2 with HBF(4) gave the BF(2)-capped compound [Pd((1)(2)BF(2))](2)(micro-Cl)(2) (7). The solid-state structure of 7 containing a PdP(2)O(2)B metallacycle has been determined. Chloride abstraction of 7 with AgBF(4) in acetone/water afforded the aqua compound [Pd((1)(2)BF(2))(H(2)O)(2)][BF(4)] (8) that reacted with [NH(4)](2)[WS(4)] to give [Pd((1)(2)BF(2))(2)](2)[micro-WS(4)] (9). The average Pd-S and W-S distances in 9 are 2.385(3) and 2.189(3) A, respectively. Treatment of [(eta(6)-p-cymene)RuCl(2)](2) with 1H afforded the phosphinous acid adduct (eta(6)-p-cymene)RuCl(2)(1H) (10). Reduction of [CpRuCl(2)](x)() (Cp = eta(5)-C(5)Me(5)) with Zn followed by treatment with 1H resulted in the formation of the Zn(II) phosphinate complex [(CpRu(eta(6)-C(6)H(5)))(t)BuPO(2))](2)(ZnCl(2))(2) (11) that contains a Zn(2)O(4)P(2) eight-membered ring.     

Synthesis and photoresponsive study of azobenzene centered polyamidoamine dendrimers

A new series of novel polyamidoamine (PAMAM) dendrimers 4, 5 and 6 possessing azobenzene units specifically at the core were prepared and their reversible trans/cis photoisomerization properties were studied. PAMAM dendritic wedges as well as azo-based PAMAM dendrimers were fully characterized by means of FT-IR, NMR (¹H and ¹³C), mass spectrometry (MALDI-MS), thermogravimetric and elemental analysis.     

A method of three-jet analysis ine + e − annihilation

For three-jet events ine ⁺ e ^? annihilation, a procedure is described to determine all three jet axes by minimizing the sum of squares of transverse momenta. Computations with this procedure show that at high energies the result is quite insensitive to missing particles, such as neurals.     

Epoxy-based polymer bearing activated azo dye (methyl orange) units: novel colorimetric indicator for amines

Novel epoxy-based polymer 2-bearing activated azo dye, 4-(4-sulphophenylazo)-N,N-dimethylaniline (methyl orange), moieties were synthesised by post-azo-coupling reaction of poly(hydroxy ether amine) 1 and investigated sensory responses towards amines. The reversible protonation–deprotonation chemistry of activated azobenzene moiety makes it of potential use as a colorimetric indicator for amines.     

Diamagnetic susceptibility obtained from the six-vertex model and its implications for the high-temperature diamagnetic state of cuprate superconductors

We study the diamagnetism of the six-vertex model with the arrows as directed bond currents. To our knowledge, this is the first study of the diamagnetism of this model. A special version of this model, called the F model, describes the thermal disordering transition of an orbital antiferromagnet, known as d-density wave, a proposed state for the pseudogap phase of the high-T(c) cuprates. We find that the F model is strongly diamagnetic and the susceptibility may diverge in the high-temperature critical phase with power-law arrow correlations. These results may explain the surprising recent observation of a diverging low-field diamagnetic susceptibility seen in some optimally doped cuprates within the d-density wave model of the pseudogap phase.     

Influence of ion–ion correlation on Na+ transport in Na2Ni2TeO6: molecular dynamics study

Molecular dynamics (MD) study of Na⁺ transport in Na₂Ni₂TeO₆ is performed systematically with varying strength of Na⁺–Na⁺ short range repulsions to understand the physical principle governing ion transport mechanism. Na⁺ diffusion is enhanced by nearly an order of magnitude with reduced Na⁺–Na⁺ short range repulsion within the studied range. A similar behavior is also observed in other systems, e.g., AgI and Na₂Zn₂TeO₆, where mobile ions are located closely. The Na⁺ ion occupancy in Na₂Ni₂TeO₆ shows a significant shift from Na1 to Na2 sites gaining some degree of correlation. The study also emphasizes how mobile ion size influences the ionic diffusion. The fresh insight such as microscopic migration pathways, energy barriers, and jumping mechanism of Na⁺ are derived from the study.     

Polyelectrolyte complex membranes for specific cell adhesion

The presentation of bioactive ligands on biomaterial surfaces is often confounded by the adsorption of proteins present in the biological milieu, rendering any type of cellular response nonspecific. We have engineered a polyelectrolyte complex membrane that demonstrates specific adhesion of various cell types for both two-dimensional (2D) and three-dimensional (3D) cell culture systems. Specific cell adhesion is achieved by a three-tiered structure: a silica cross-linked polycation as the bottom (first) tier, a nonfouling polyanion-poly(ethylene glycol) (PEG) conjugate as the intermediate (second) tier, and the cell-adhesion ligand as the top (third) tier. Each tier of the membrane was characterized in terms of chemical composition and dimensions. Epithelial cells (primary human cortical renal cells and a hepatocellular carcinoma cell line) cultured on the membranes exhibited little cell attachment on the polyanion-PEG second tier and good cell adhesion on the RGD-modified third tier. Thus, the second tier allowed the effect of cell adhesion due to the ligand (third tier) to be isolated and distinguished from nonspecific cell attachment to the first tier. For the culturing of cells in three dimensions, the three-tiered membrane system was applied using a highly swellable chitosan membrane as the first tier. The resulting cell-membrane construct was uniformly dispersed and centrifuged to form a matrix that interacted intimately with cells in the form of a pellet. Presentation of RGD in the latter format enhanced the viability of human mesenchymal stem cells (hMSCs) over controls without RGD.     

Interaction of N-(aryl)picolinamides with iridium. N–H and C–H bond activations

Reaction of N-(4-R-phenyl)picolinamide (R = OCH₃, CH₃, H, Cl and NO₂) with [Ir(PPh₃)₃Cl] in refluxing ethanol in the presence of a base (NEt₃) affords two yellow complexes (1-R and 2-R). The 1-R complexes contain an amide ligand coordinated to the metal center as a monoanionic bidentate N,N donor along with two triphenylphosphines, a chloride and a hydride. The 2-R complexes contain an amide ligand coordinated to the metal center as a monoanionic bidentate N,N donor along with two triphenylphosphines and two hydrides. Similar reaction of N-(naphthyl)picolinamide with [Ir(PPh₃)₃Cl] affords two organometallic complexes, 3 and 4. In complex 3 the amide ligand is coordinated to the metal center, via C–H activation of the naphthyl ring at the 8-position, as a dianionic tridentate N,N,C donor, along with two triphenylphosphines and one chloride. Complex 4 is similar to complex 3, except a hydride is bonded to iridium instead of the chloride. Structures of the 1-OCH₃, 2-Cl and 4 complexes have been determined by X-ray crystallography. All the complexes are diamagnetic, and show characteristic ¹H NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry on all the complexes shows a Ir^III–Ir^IV oxidation within 0.50–1.16 V vs. SCE and a reduction of the coordinated amide ligand within −1.02 to −1.25 V vs. SCE.     

Rhodium complexes of 1,3-diaryltriazenes: Usual coordination, N-H bond activation and, N-N and C-N bond cleavage

Reaction of 1,3-diaryltriazenes (R-C₆H₄-NN-(NH)-C₆H₄-R, R = OCH₃, CH₃, H, Cl, NO₂ at the para position) with [Rh(PPh₃)₃Cl] in ethanol in the presence of a base (NEt₃) affords a family of yellow complexes (1-R) containing a PPh₃, two de-protonated triazenes coordinated as bidentate N,N-donors, and an aryl (C₆H₄-R) fragment coordinated in the η¹-fashion. A similar reaction in toluene yields a group of reddish-orange complexes (2-R) containing a PPh₃, two N,N-coordinated triazenes, and a chloride. Structures of the 1-CH₃ and 2-CH₃ complexes have been determined by X-ray crystallography. All the 1-R and 2-R complexes are diamagnetic, and show characteristic ¹H NMR signals and intense MLCT transitions in the visible region. The 1-R and 2-R complexes also fluoresce in the visible region under ambient condition while excited at around 400 nm. Cyclic voltammetry on these complexes shows a Rh(III)-Rh(IV) oxidation (within 0.76-1.68 vs. SCE), followed by an oxidation of the coordinated triazene ligand (except the R = NO₂ complexes). An irreversible reduction of the coordinated triazene is also observed for all the complexes below −0.96 V vs. SCE. In the 1-R and 2-R complexes potential of the Rh(III)-Rh(IV) oxidation correlates linearly with the electron-withdrawing nature of the para-substituent (R).     

Electrophilic ruthenium(VI) nitrido complex containing Kläui's oxygen tripodal ligand

Treatment of [n-Bu4N][Ru(N)Cl4] with [AgL(OEt)] (L(OEt)- = [(eta5-C5H5)Co{P(O)(OEt)2}3]-) afforded the ruthenium(VI) nitrido complex [L(OEt)Ru(N)Cl2] (1), which reacted with PPh3 to give the ruthenium(IV) phosphiniminato complex [L(OEt)Ru(NPPh3)Cl2] (2). The cyclic voltammogram of 2 displays the RuIV/III couple at ca. 0 V vs ferrocenium/ferrocene. Treatment of 1 with Me3NO afforded [LOEtRu(NO)Cl2] (3), which reacted with Ag(OTf) (OTf- = triflate) to give the chloro-bridged tetranuclear ruthenium/silver complex [L(OEt)Ru(NO)Cl2]2[Ag(OTf)]2 (4). Treatment of 1 with Na2S2O3 gave the thionitrosyl complex [L(OEt)Ru(NS)Cl2] (5). The solid-state structures of 1-4 have been established by X-ray crystallography.