Calix[4]bis(thiacrown): assembly of an endocyclic disilver(I) complex and exocyclic 3D copper(I) coordination polymers

Calix[4]bis(thiacrown-5) (L) with 1,3-alternating conformation was employed as a strong dinucleating ligand for the soft metal ions AgI and CuI. The reaction of L with AgPF6 afforded a discrete endo-coordinated disilver(I) complex 1, [Ag2L](PF6)2. In contrast, mixed products (2a + 2b) consisting of 3D networks were obtained from the reaction of L and CuI; 2b linked with a Cu4I4 cubane unit was shown to generate photoluminescence, while 2a linked with a Cu2I2 rhomboid unit does not.     

Copper(I) cyanide networks: synthesis, luminescence behavior and thermal analysis. Part 1. Diimine ligands

Metal-organic networks of CuCN with diimines (L) = pyrazine (Pyz), 2-aminopyrazine (PyzNH(2)), quinoxaline (Qox), phenazine (Phz), 4,4'-bipyridyl (Bpy), pyrimidine (Pym), 2-aminopyrimidine (PymNH(2)), 2,4-diaminopyrimidine (Pym(NH(2))(2)), 2,4,6-triaminopyrimidine (Pym(NH(2))(3)), quinazoline (Qnz), pyridazine (Pdz), and phthalazine (Ptz) were studied. Open reflux reactions produced complexes (CuCN)(2)(L) for L = Qox, Phz, Bpy, PymNH(2), Pym(NH(2))(2), Qnz, and Pdz and (CuCN)(3)(L) complexes for L = Pyz, PyzNH(2), Qox, Bpy, Pym(NH(2))(3), and Pdz. Also produced were (CuCN)(3)(Pyz)(2), (CuCN)(PyzNH(2)), (CuCN)7(Pym)(2), (CuCN)(5)(Qnz)(2) and (CuCN)(5)(Ptz)(2). X-ray structures are presented for (CuCN)(2)(Pdz), (CuCN)(2)(PymNH(2)), and (CuCN)(7)(Pym)(2). Hydrothermal reactions yielded additional X-ray structures of (CuCN)(2)(PyzNH(2)), (CuCN)(3)(Pym(NH(2))(2)), (CuCN)(4)(Qnz), a second (CuCN)(2)(Pdz) phase, (CuCN)(5)(Pdz)2, (CuCN)(2)(Ptz), and (CuCN)(7)(Ptz)2. Structural trends, including cuprophilic interactions and cyano-bridged Cu(2)(CN)(2) dimer formation, are discussed. Particularly short Cu...Cu interactions are noted for the novel 4- and 5-coordinate Cu(2)(CN)(2) dimers. Thermal analyses show that most of the complexes decompose with loss of L around 160-180 degrees C. Luminescence behavior is relatively weak in the products.     

Reorganization of highly preorganized hosts upon cation complexation: Ab initio study of fluorospherands

Fluorospherands (F‐spherands) are highly preorganized hosts composed of fluorobenzene or 4‐methylfluorobenzene units attached to one another at their 2,6‐positions. To understand the intrinsic factors affecting cation complexation, we investigated the complexation behavior between F‐spherands and cations using density functional theory (DFT) at the level of B3LYP/6‐31G**. The F6‐spherand (C₆H₃F)₆, ( 1 ) has a highly preorganized spherical cavity, which can encapsulate Li⁺ and Na⁺. Its cavity is not big enough for K⁺ and NH, which prefer external binding. Plausible conformations were studied for F8‐spherand (C₆H₃F)₈. Conformer of D_2d symmetry ( 2b ) is more stable than that of D_4d ( 2a ), in agreement with NMR experiments. The cavity size of F8‐spherand is big enough to encapsulate all cations studied. However, the cavity size of 2b is smaller than that of 2a , which resulted in the guest selectivity. Upon complexation, 2b conformation is more stable for Li⁺ and Na⁺, while 2a conformation is preferred for larger cations such as K⁺ and NH. Thus, the ab initio calculations over these highly preorganized fluorospherands give important insights into their host–guest chemistry. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Cyanide-bridged W(V)-Co(II) double-zigzag chain based on an octacoordinated W precursor: metamagnetism and spin canting

A cyanide-bridged W-Co bimetallic complex (1) with a double-zigzag chain structure was characterized in terms of structure and magnetism. Compound 1 exhibits metamagnetism and spin canting induced by the presence of anisotropic CoII ions and noncovalent interactions.     

Reaction and stabilizing mechanism of the cross-type macromonomers in the dispersion polymerization of styrene

The cross-type (C-VUM) and linear-type (L-VUM) bifunctional vinyl urethane macromonomers and polystyrene (PS) using these macromonomers were synthesized in the dispersion polymerization in ethanol, and the reaction and stabilizing mechanism of the macromonomers was proposed. The structural verification of the macromonomers and PS was studied using (1)H NMR. The weight-average particle size of C-PS (PS prepared with C-VUM) and L-PS (PS prepared with L-VUM) decreased from 4.41 to 1.36 microm and from 3.56 to 1.52 microm, whereas the average-molecular weight of those increased from 34,100 to 100,500 g/mol and from 32,200 to 71,800 g/mol, respectively. The XPS result showed that the C-PS was anchored with a larger amount of PEG than that of the L-PS on the particle surface. Thus, the reaction and stabilizing mechanism of the macromonomers for the formation of PS particles is proposed as the following. The particle surface of the C-PS is surrounded by a large amount of tail shaped macromonomers leading to higher molecular weights and smaller particle sizes. On the other hand, the particle surface of the L-PS is comprised of relatively small amounts of loop shaped macromonomers inducing lower molecular weights and larger particles of L-PS than C-PS.     

Effect of the residual silanol group protection on the liquid chromatographic resolution of racemic primary amino compounds on a chiral stationary phase based on optically active (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6

A liquid chromatographic chiral stationary phase (CSP) based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6, which has been utilized in the resolution of alpha-amino acids, amines and amino alcohols, was treated with excess of n-octyltriethoxysilane to prepare a new improved CSP. The residual silanol groups of the original CSP were protected by n-octyl groups in the new CSP. The chiral recognition ability of the new CSP was superior to that of the original CSP in the resolution of alpha-amino acids, amines and amino alcohols. Retention factors (k1) for the resolution of alpha-amino acids were lower on the new CSP than on the original CSP while those for the resolution of amines and amino alcohols were higher on the new CSP than on the original CSP. The improved chiral recognition ability of the new CSP and the retention behaviors of the two enantiomers on the new CSP have been rationalized to stem from the removal of the non-enantioselective interactions between the analytes and the residual silanol groups of the original CSP and the improved lipophilicity of the CSP.     

Functionalized polymer colloids bearing primary amino groups

Polymer colloids are prepared via radicalic emulsion polymerisation of butylacrylate. Functionalization with amino groups is achieved by copolymerisation of 2-amino-ethylmethacrylates. In order to over-compensate the positive surface charges resulting from the amino groups additionally vinylbenzenesulfonic acid is copolymerized. The size of the resulting particles is controlled by the molar ratio of amino to sulfonic acid groups. The suitability of amino groups for coupling reactions is demonstrated by electrophilic addition of fluorescein-5-isothiocyanate. The resulting particles are characterized by dynamic light scattering and zeta potential measurements as well as by optical spectroscopy. The suitability of labelled particles for optical tracer experiments is demonstrated by fluorescence correlation spectroscopy.     

A facile synthesis of 1‐alkyl‐5‐arylalkoxy‐6‐methoxy‐3,4‐dihydroisoquinolines

1‐Alkyl‐5‐arylalkoxy‐6‐methoxy‐3,4‐dihydroisoquinolines were synthesized by the alkylation of 1‐alkyl‐5‐hydroxy‐6‐methoxy‐3,4‐dihydroisoquinolines with arylalkyl halide in the presence of potassium carbonate. 1‐Alkyl‐5‐hydroxy‐6‐methoxy‐3,4‐dihydroisoquinolines as key precursor prepared from o‐vaniline via 6 steps.     

The distinct signaling mechanisms of microbial sensory rhodopsins in Archaea, Eubacteria and Eukarya

Most of the known archaeal-type microbial rhodopsins are retinal-binding ion transporters, such as bacteriorhodopsin (BR) and proteorhodopsin (PR). Their identification is the result of extensive studies of their photochemical and biophysical properties. The cells containing these pigments, however, use other microbial rhodopsins as photosensors to monitor environmental light signals. From the early studies of sensory rhodopsin I (HsSRI) in Halobacterium salinarum and sensory rhodopsin II (NpSRII) in Natronomonas pharaonis, we now know that several microbial sensory rhodopsins in the other major domain of life relay information on light intensity and quality to the cell. Three of the most studied photosensory transduction mechanisms of these microbial rhodopsins are dealt with in this review. We discuss recent progress in the understanding of genomic organization, photochemical properties and photosignaling mechanisms with respect to biological function.     

Concise synthesis of rodgersinol and determination of the C-10 absolute configuration

Rodgersinol was synthesized via seven linear steps in 31% overall yield, and the absolute configuration of the C-10 stereogenic center was elucidated. The key feature of the synthesis involves the efficient Cu(II)-mediated coupling of two aromatic moieties for the diaryl ether intermediate and the enantioselective construction of the hydroxypropyl substituent by a regio- and stereoselective methyl addition to the chiral aryloxiranes in an inversion manner.