Supramolecular Metal Complex with Ferrocene-conjugated Macrocyclic Triaza Crown Ether as Ligand and Its Electrochemical Property

LigandscontainingelectrochemicallyresponsivecentrearegoodsubjectsforthestUdyofintfamolecularandhost-guestillteraction.Forthisreason,tYemendousamoulltsofsuchligandsandtheircomplexeshavebeensynthesized.'-'AnobservationfromthestudiesofthesecomPlexesisthattheguestionhasapermrbationonthehostcelltre.2'7-9Forexample,itwasdocumelltedthatintroductionofCo(II)ionontoN-ferrocenylmethyl-l,4,7-triazacyclononane(fcmtacn)causesapositiveshiftintheredoxpotentialofferrocenylgroupfromthatofferrocenegroupinfree…     

The temperature-dependent red-shift of the visible absorption spectra of crystal violet in alcohol solutions

The visible absorption spectrum of the triphenylmethane dye, crystal violet, in various alcohol solutions at several temperatures has been recorded and subsequently analyzed by computer fitting. The observed spectral changes do not sustain either the earlier temperature-dependent absorption results of Lewis and co-workers or the concept of two ground-state species in equilibrium.     

Steric Effects on Reaction Rates. Rate and equilibrium constants for oxidation of cyclanols

Equilibrium constants for oxidations of cyclanols by cyclohexanone in benzene have been determined in the presence of aluminium isopropoxide. The free energies of the equilibrium (ΔG_ox) are correlated with equilibrium constants for dissociation of cyanohydrins, rate constants for cyclanol oxidation with chromic acid, ketone reduction with sodium borohydride and trifluoroethanolysis of tosylates.     

Efficient synthesis of bromocyclopenta[b] indoles via a bromination ‐ reduction sequence

Substituted cyclopenta[b]indoles are selectively brominated in good yields with excess pyridine ‐ Br₂ charge‐transfer complex (PyBr₂) in a one‐pot reaction to provide 5 and/or 7‐bromoindoles. The mechanism involves the formation of an adduct (addition of bromine on the central double bond) which is subsequently reduced in situ with Zn and AcOH. A variety of functional groups in the cyclopentyl and the benzenoid rings are tolerated.     

On constrained multivariate splines and their approximations

Summary The variational formulation of multivariate spline functions is generalized to include cases where the function has to satisfy inequality constraints such as positivity and convexity. Condition for existence and uniqueness of a solution is given. Approximation to the solution can be obtained by solving the variational problem in a finite dimensional subspace. Conditions for convergence and error estimates of the approximations are presented, both for interpolation problems and smoothing problems. The general theory is illustrated by specific examples including the volume-matching problem and the one-sided thin plate spline.This research is partially supported by the U.S. Army Contract No. DAAG 29-77-G-0207, and by NSF Grant No. MCS-8101836Part of this paper is based on Chapters 2 and 3 of the author's Ph. D. thesis. The author would like to express his sincere thanks to Professor Grance Wahba and to two referees for many helpful comments     

Dinuclear and Mononuclear Platinum(II) and Palladium(II) Complexes with Modified 2,2′‐Dipyridylamine Ligands Featuring a Cisplatin Analogous Structure Motif

In modern cancer therapy the clinical application of platinum‐based drugs is more and more limited by the occurrence of intrinsic or acquired resistances. In this context the potential use of dinuclear platinum complexes in chemotherapy is increasingly relevant. The novel complexes Pd(Bzdpa)Cl₂, Pd₂(C₄H₈(dpa)₂)Cl₄, and Pt₂(C₄H₈(dpa)₂)Cl₄ allow a direct comparison of mono‐ and dinuclear palladium and platinum complexes respectively deriving from a 2,2′‐dipyridylamine (Hdpa) ligand system. They were characterized by single crystal X‐ray analysis as well as infrared spectroscopy and elemental analysis. The cisplatin analogous mononuclear palladium complex Pd(Bzdpa)Cl₂ ( 1 ) (Bzdpa: (2,2′‐dipyridylbenzyl)amine) belongs to a range of 2,2′‐dipyridylamine‐based compounds which were extensively studied in our laboratories. 1 crystallizes in the orthorhombic space group Pna2₁ with a = 13.722(3), b = 13.457(3), c = 9.483(2), V = 1751.1(6) ų, and Z = 4. The metal binding motif of 1 was expanded by a flexible butyl‐linker to form the tetradentate C₄H₈(dpa)₂ ligand. The resulting isotypic dinuclear complexes Pd₂(C₄H₈(dpa)₂)Cl₄·2CH₃CN ( 2 ) and Pt₂(C₄H₈(dpa)₂)Cl₄·2CH₃CN ( 3 ) crystallize in the triclinic space group with a = 7.8427(2), b = 8.7940(2), c = 11.7645 (3), α = 79.219(2)°, β = 84.033(2)°, γ = 87.744(2)°, V = 792.58(3) ų ( 2 ) and a = 7.831(5), b = 8.814(5), c = 11.817(5), α = 79.271(5)°, β = 83.571(5)°, γ = 88.063(5)°, V = 796.3(8) ų ( 3 ), both with one centrosymmetrical molecule in the unit cell.     

Polyvinyl pyridines as flocculating agents

Summary High molecular weight poly 2- and 4-vinyl pyridines were synthesized by ionic polymerisation and their flocculation efficiency tested against kaolin and silica dispersions at pH 3. Low additions of the polymers, around 3 parts per 10₃ parts solid, destabilize the dispersions and clarify silica dispersions to a remarkable extent; however, over-addition of polymer leads to partial restabilization. The flocculation efficiency improves with increase of solids content, especially with clay dispersions. Flocculation efficiency increases with polymer molecular weight, especially over the lower part of the range covered, but is relatively independent of pH in the range 2–4. Quaternization of poly(4-vinyl pyridine) with bromobutane produces a good flocculant for aqueous silica dispersions in which the degree of restabilization on over-dosing depends on the KCI content. TheN-oxide derivatives of the vinyl pyridine polymers do not affect the colloidal stability of silica dispersions. The observations are interpreted in terms of bridging flocculation by the cationic polymer molecules between anionic surface sites on the solid particles.     

The enthalpy of formation of magnesium sulfate ion pairs

The enthalpies of dilution of lithium, sodium, potassium, and magnesium chloride and sulfate solutions in the range 0.1 to 1.0 m have been measured at 30°C with a microcalorimeter. The relative apparent enthalpies φ_L of these solutions have been determined with the aid of an extended form of the Debye-Hückel limiting law $$\phi _L = S_H I^{1/2} [1/(1 + I^{1/2} ) - (\sigma /3)] + {\rm B}{\rm I} + CI^{3/2} $$ whereS _H is the limiting-law slope, σ = 3/I^3/2 × [(1+I^1/2 ? 1/(1+I^1/2 ? 2 ln (2+I^1/2)], andB andC are empirical constants. This equation fits the experimental results to within a standard deviation of 2 cal-mole^?1 for all the salts. The measured φ_L for the MgSO₄ solutions were compared to those calculated using the additivity principle, φ_L(MgCl₂) + φ_L(Na₂SO₄) ? 2φ_L(NaCl), and the extended Debye-Hückel equation. The results of this comparison have been used to calculate the ΔH _A ^o for the formation of MgSO ₄ ⁰ . A value of ΔH _A ^o = 1.15 to 1.36 was obtained, depending upon the φ_L estimates for the free ions Mg²⁺ and SO ₄ ^2? . The results are briefly discussed and compared to the results obtained by other workers.     

POLYMER NETWORK-POLY(ETHYLENE GLYCOL)COMPLEXES WITH SHAPE MEMORY EFFECT

The complexes of poly(methacrylic acid-co-methyl methacrylate) network with poly(ethylene glycol) stabilized byhydrogen bonds were prepared. By introducing the poly(ethylene glycol), a large difference in storage modulus below andabove the glass transition temperature occurred and the complexes exhibited shape memory behaviors. The morphology ofcomplexes was studied by using DSC, WAXD, and DMA. The results indicate that the fixed phase of this kind of novelshape memory materials is the network, and the reversible phase is the amorphous state of PEG:PMAA complex phase. Theshape recoverability almost reaches 100%. This type of complexes can be regarded as a novel shape memory network.     

Synthesis and crystal structure of an imidazolate-bridged dicopper tris(2-aminoethyl)amine complex

The [Cu(tren)(Im)Cu(tren)](ClO4)3·MeCN complex [tren=tris(2-aminoethyl)amine; Im=imidazolate anion] has been synthesized and characterized spectrally. The X-ray crystal structure analysis reveals that the imidazolate anion serves as a bridge to form a noncentrosymmetric dimeric structure in the complex. The co-ordination geometry about each copper(II) ion is a distorted trigonal bipyramid with three primary amine groups of the tren ligand forming the equatorial plane. The tertiary amine group and the imidazolate anion are in the axial positions. This revised version was published online in June 2006 with corrections to the Cover Date.