Dynamics of heteropolymers in dilute solution: effective equation of motion and relaxation spectrum

The dynamics of a heteropolymer chain in solution is studied in the limit of long chain length. Using functional integral representation we derive an effective equation of motion, in which the heterogeneity of the chain manifests itself as a time-dependent excluded volume effect. At the mean field level, the heteropolymer chain is therefore dynamically equivalent to a homopolymer chain with both time-independent and time-dependent excluded volume effects. The perturbed relaxation spectrum is also calculated. We find that heterogeneity also renormalizes the relaxation spectrum. However, we find, to the lowest order in heterogeneity, that the relaxation spectrum does not exhibit any dynamic freezing, at the point when static (equilibrium) ``freezing'' transition occurs in heteropolymer. Namely, the breaking of fluctuation-dissipation theorem (FDT) proposed for spin glass dynamics does not have dynamic effect in heteropolymer, as far as relaxation spectrum is concerned. The implication of this result is discussed

The size of a polymer molecule in semi-dilute solution

The mean-square end-to-end distance for a given polymer in a solution whose concentration lies in the semi-dilute regime has been studied using the field-theoretic formulism. The crossover function which describes the increase in the end-to-end distance as the temperature is raised from the θ-point towards the good solvent limit is calculated (correct to order ε = 4 - d) using the renormalization group. The agreement with the present experimental data obtained by scattering neutrons off a few deuterated chains in the solution is poor.En utilisant le formalisme de la théorie des champs, on calcule la distance quadratique moyenne des extrémités d'un polymère en solution semi-diluée. Cette distance croit avec la température quand on s'éloigne du point θ vers la limite du bon solvant et la fonction de crossover décrivant cette variation est calculée, correctement à l'ordre ε = 4 - d, suivant la méthode du groupe de renormalisation. L'accord avec les résultats expérimentaux foumis par la diffraction des neutrons par des chaînes deutérées en solution n'est pas très bon

Neutral ruthenium(II) complexes of phenylcyanamido ligands

Neutral Ru(II) complexes with the formula trans-[Ru(trpy*)(L 2)(pcyd)] have been prepared, where trpy* = 4,4′,4″-tri-tert-butyl-terpyridine, L 2 = 2-pyrazinecarboxylato (pca), 2-pyridinecarboxylato (pic), acetylacetonato (acac) and pcyd = 3-chlorophenylcyanamido (3-Clpcyd), 2,3-dichlorophenylcyanamido (2,3-Cl 2pcyd), 2,4,6-trichlorophenylcyanamido (2,4,6- Cl 3pcyd), 2,3,4,5-tetrachlorophenylcyanamido (2,3,4,5-Cl 4pcyd) and 3,4,5-trimethoxyphenylcyanamido (3,4,5-(OMe) 3pcyd). Spectroelectrochemistry was performed on these Ru(II) complexes to obtain the visible absorption spectrum of the Ru(III)-cyanamide ligand-to-metal charge transfer chromophore. The Ru(III)-cyanamide metal-ligand coupling elements of these complexes were compared to other Ru(III)-cyanamide complexes

Synthesis of ethylene bis [(2-hydroxy-5,1,3-phenylene) bis methylene] tetraphosphonic acid and their anticorrosive effect on carbon steel in 3%NaCl solution

International audienc

Synthesis, structural characterization, and DFT investigation of azoimine-ruthenium complexes containing aromatic-nitrogen ligands

Seven ruthenium(II) complexes continuing substituted diimine ligands and the azoimine ligand (Az: C6H5N{double bond, long}NC(COCH3){double bond, long}NC6H5) are synthesized and characterized. trans-[Ru(II)(Az)(L)Cl2] [L = 2,2′-bipyridine (bpy) 1, 4,4′-dimethyl-2,2′-bipyridine (dmb) 2, 4,4′-dimethoxy-2,2′-bipyridine (dmeb) 3, 4,4′-di-tertbutyl-2,2′-bipyridine (dtb) 4, 1,10-phenanthroline (phen) 5, 5-amino-1,10-phenanthroline (NH2phen) 6, 5-chlorophenanthroline (Clphen) 7, 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen) 8] are made by the reaction of RuCl3 hydrate and the ligands in the presence of LiCl. These complexes have been characterized by cyclic voltammetry, UV-Vis spectroscopy, electrochemical measurements and X-ray diffraction analysis for 2 and 5. The electrochemical parameters (EL(L)) of the substituted diimine ligands (L) are reported. The absorption spectrum of 5 in acetonitrile has been modeled by time-dependent density functional theory (TD-DFT) using a hybrid functional, B3LYP, as well as the LanL2DZ basis set

Ruthenium(II) complexes with tetradentate pyridylthioazoimine [N,S,N,N] ligands: Synthesis, crystal structure and spectroscopy

The Ru(II) complexes cis-[Ru(L)Cl2] (C1-C3) of novel tetradentate NSNN ligands (L) {where L is C5H4N-CH 2-S-C6H4N=C(COCH3)-N=N-C 6H4X, and X is H (L1), CH3 (L2) and Br (L3)}, were synthesized and characterized by spectroscopy (IR, UV/vis and NMR), cyclic voltammetry and crystallography. The tetradentate ligands were isolated as the amidrazones H2L {where H2L is C5H 4N-CH2-S-C6H4NH-C(COCH 3)+N-NH-C6H4X and X is H (H2L1), CH3 (H2L2) and Br (H2L3)} as shown by crystallography of H2L1, but oxidize to azoimines during the formation of the Ru(II) complexes. A crystallographic analysis of C1 showed that the Ru(II) centre is in a distorted octahedral coordination sphere in which the tetradentate ligand occupies three equatorial sites and one axial site (two azoimine nitrogens and a thio sulfur in the equatorial plane and an axial pyridine nitrogen) and two chlorides occupying axial and equatorial coordination sites. The Ru(II) oxidation state is greatly stabilized by the novel tetradentate ligand, showing Ru(III/II) couples ranging from 1.43 to 1.51 V. The absorption spectrum of C1 in acetonitrile was modelled by time-dependent density functional theory

Synthesis and characterization of ruthenium(II) azoimine-diphosphine mixed-ligand complexes

A novel family of the general type cis-[RuII(dppe)LCl2] {L = C6H5N{double bond, long}NC(COCH3){double bond, long}NAr, Ar = 2,4,6-trimethylphenyl (L1), 2,5-dimethylphenyl (L2), 4-tolyl (L3), phenyl (L4), 4-methoxyphenyl (L5), 4-chlorophenyl (L6), 4-nitrophenyl (L7), 2,5-dichlorophenyl (L8); dppe = Ph2P(CH2)2PPh2} has been synthesized. These complexes have been characterized through analytical, spectroscopic (IR, UV-Vis, and NMR) and electrochemical (cyclic voltammetry) techniques. In addition, complex 4 (where L = L4) has been further characterized by X-ray diffraction analysis. Crystallographic, electrochemical and electronic spectral data are all consistent with the azomethine ligands possessing strong π-acceptor properties. These π-acceptor properties can be "tuned" by a judicious choice of substituent on the azomethine ligand

Variable noninnocence of substituted azobis(phenylcyanamido)diruthenium complexes

The synthetic chemistry of substituted 4,4′-azobis(phenylcyanamide) ligands was investigated, and the complexes [{Ru(tpy)(bpy)}2( μ-L)][PF6]2, where L = 2,2′:5,5′-tetramethyl-4,4′-azobis(phenylcyanamido) (Me4adpc2-), 2,2′-dimethyl-4,4′-azobis(phenylcyanamido) (Me2adpc2-), unsubstituted (adpc2-), 3,3′-dichloro-4,4′-azobis(phenylcyanamido) (Cl2adpc2-), and 2,2′:5,5′-tetrachloro-4,4′-azobis(phenylcyanamido) (Cl4adpc2-), were prepared and characterized by cyclic voltammetry and vis-near-IR (NIR) and IR spectroelectrochemistry. The room temperature electron paramagnetic resonance spectrum of [{Ru(tpy)(bpy)}2( μ-Me4adpc)]3+ showed an organic radical signal and is consistent with an oxidation-state description [RuII, Me4adpc•-, RuII]3+, while that of [{Ru(tpy)(bpy)}2( μ-Cl2adpc)]3+ at 10 K showed a low-symmetry RuIII signal, which is consistent with the description [RuIII, Cl2adpc2-, RuII</su