Recoordination of a metal ion in the cavity of a crown compound: a theoretical study 2.* Effect of the metal ion— solvent interaction on the conformations of calcium complexes of arylazacrown ethers

The effect of the local interaction of a metal ion with the solvent on the conformations of calcium complexes of arylazacrown ethers and an azacrown-containing dye was studied using the density functional method with the PBE and B3LYP functionals. The structures were studied and the interaction energies were determined for the calcium complexes with n = 1–12 water or acetonitrile molecules. It was found that the inner coordination sphere of the free Ca²⁺ cation contains six H₂O or seven MeCN molecules. The cation—acetonitrile interaction energy is higher than the cation—water interaction energy up to the moment the second solvation shell of the cation is almost complete (n = 11). The inner coordination sphere of Ca²⁺ in the macrocycle cavity contains at most three water molecules, while the fourth one is displaced to the second coordination sphere. Taking into account the local interaction with the solvent (H₂O or MeCN), the conformers of the calcium complexes of arylazacrown ethers and the azacrown-containing dye were studied. It was shown that the presence of two to four water molecules in the coordination sphere of the cation reduces the relative energies of the conformers with broken metal—nitrogen bond, thus favoring ground-state metal recoordination. For Part 1, see Ref. 1. Dedicated to Academician A.L. Buchachenko on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1981–1992, September, 2005.     

Crown-containing butadienyl dyes. 5. Structure and photoisomerization of a butadienyl dye containing a 15-crown-5 fragment

The structure of the E,E isomer of a butadienyl dye of the benzothiazole series containing a 15-crown-5 fragment was established by X-ray diffraction analysis. The stacking motif of the dye molecules in the crystal structure is, apparently, attributable to intermolecular -interactions between the large conjugated fragments. The possibility of [2+2] photocycloaddition occurring in the crystal is discussed. Reversible geometrical photoisomerization of the dye and its complex with Mg²⁺ in acetonitrile solution was studied by spectrophotometry and ¹H NMR spectroscopy. Photoirradiation of the complex of the E,E isomer with Mg²⁺ leads predominantly to isomerization of the C=C bond adjacent to the benzothiazole fragment. Regioselective E,EZ,E photoisomerization occurs via a singlet mechanism with a quantum yield of about 0.45. The quantum yield of reverse Z,EE,E photoisomerization is approximately 0.52. The structures of different geometrical isomers of the dye complex with Mg²⁺ were calculated by the quantum-chemical density functional theory (DFT).     

Preparation and X-ray structures of complexes of 18-membered crown ethers with polyfunctional guests: Urea and (O-alkyliso)uronium salts

The preparation and X-ray structure determinations of six complexes of urea and (O-n-butyliso)uronium salts with crown ethers are presented. Urea forms isostructural 5:1 adducts with 18-crown-6 (1) and aza-18-crown-6 (2), in which two urea molecules are each hydrogen bonded to two neighbouring hetero atoms of the macroring. The remaining urea molecules form two-dimensional layers alternating with crown ether layers. In both complexes the macroring has theg ⁺ g ⁺ a ag ^– a ag ^– a g ^– g ^– a ag ⁺ a ag ⁺ a conformation withC _i symmetry. In the solid 1:1 complex of O-n-butylisouronium picrate with 18-crown-6 (3) two types of conformations of the macroring were observed: theg ⁺ g ⁺ a ag ^– a ag ⁺ a ag ^– g ^– ag ^– a ag ⁺ a conformation with approximateC _m symmetry and to a lesser extent theg ⁺ g ⁺ a ag ^– a ag ⁺ a g ⁺ g ⁺ a ag ^– a ag ⁺ a conformation with approximateC ₂ symmetry. Both conformations allow the guest to form three hydrogen bonds to the macrocyclic host. Three complexes of 18-crown-6 and uronium salts have been prepared and characterized by X-ray crystallography. The 1:1 complexes with uronium nitrate (4) and uronium picrate (5) both exhibit the sameC ₂ conformation and the same hydrogen bonding scheme as in the least occupied form of the previous complex. A 1:2 complex with uroniump-toluenesulphonate (6) has a different hydrogen bonding scheme (two hydrogen bonds per cation to neighbouring oxygen atoms of the macroring) and a different conformation of the host molecule (theag ⁺ a ag ^– a ag ⁺ a ag ^– a ag ⁺ a ag ^– a conformation with almostD _3d symmetry). An attempt to prepare a solid uronium nitrate complex with diaza-18-crown-6 in the same way as the 18-crown-6·uronium nitrate (1:1) complex did not yield the expected result. Instead X-ray analysis revealed that the uronium ion is dissociated, resulting in the nitrate salt of the diprotonated diaza crown ether (7). Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82058 (26 pages).     

Poly[4-diacetoxyiodo] Styrene–Promoted Thiocyanation of Aromatic Ethers,Anilines, and Indoles

Abstract

Thiocyanation of aromatic ethers, anilines, and indoles have been achieved using ammonium thiocyanate in the presence of poly[4-diacetoxyiodo] styrene (PDAIS) in CH₃CN at room temperature.

GRAPHICAL ABSTRACT     

Copper(I) Coordination Polymers with Alkanedithiol and ‐dinitrile Bridging Ligands

CuI‐based coordination polymers with 1, 2‐ethanedithiol, 3, 6‐dioxa‐1, 8‐octanedithiol and 3‐oxa‐1, 5‐pentanedinitrile as respectively μ‐S, S′ and μ‐N, N′ bridging ligands have been prepared by reaction of CuI with the appropriate alkane derivative in acetonitrile. equation/tex2gif-stack-1.gif[Cu(HSCH₂CH₂SH)₂]I ( 1 ) contains 4⁴ cationic nets, equation/tex2gif-stack-2.gif[(CuI)₂(HSCH₂CH₂OCH₂CH₂OCH₂CH₂SH)] ( 2 ) neutral layers in which stairlike CuI double chains are linked by dithiol spacers. In contrast to these 2D polymers, equation/tex2gif-stack-3.gif[CuI(NCCH₂CH₂OCH₂CH₂CN)] ( 3 ) and equation/tex2gif-stack-4.gif[(CuI)₄(NCCH₂CH₂OCH₂CH₂CN)₂] ( 4 ) both contain infinite chains with respectively (CuI)₂ rings and distorted (CuI)₄ cubes as building units. Solvothermal reaction of CuI with the thiacrown ether 1, 4, 10‐trithia‐15‐crown‐5 (1, 4, 10TT15C5) in acetonitrile affords the lamellar coordination polymer equation/tex2gif-stack-5.gif[(CuI)₃(1, 4, 10TT15C5)] ( 7 ) in which copper atoms of individual CuI double chains are bridged in a μ‐S1, S4 manner. The third sulphur atom S10 of the thiacrown ether coordinates a copper(I) atom from a parallel chain to generate a 2D network.     

Precise synthesis of pH‐responsive copolymers with naphthoic acid side groups via living cationic polymerization

pH‐Responsive homopolymers and copolymers with naphthoic acid side groups were synthesized via base‐assisting living cationic polymerization. To this end, the feasibility of the living cationic polymerization of ethyl 6‐[2‐(vinyloxy)ethoxy]‐2‐naphthoate (EVEN) was first examined using a base‐assisting initiating system. Et_1.5AlCl_1.5 as a Lewis acid catalyst induced the living cationic polymerization of EVEN in the presence of ethyl acetate or 1,4‐dioxane in CH₂Cl₂ at 0 °C. In contrast, the use of naphthoxyethyl vinyl ether (NpOVE), which is a nonsubstituted counterpart, resulted in a poorly controlled polymerization under these conditions. The presence of the carboxy ester was most likely critical in preventing side reactions. A subsequent alkaline hydrolysis of the side‐chain esters quantitatively yielded a carboxy‐containing polymer. Aqueous solutions of this polymer underwent pH‐driven phase separation at pH 7.0. Well‐defined random and block copolymers were also prepared with various functional segments, and their stimuli‐responsive behaviors were investigated in terms of solution transmittance and aggregate size. Block copolymers containing two different pH‐responsive segments formed micelle‐like structures between the two phase‐separated pH values, and dual stimuli‐responsive copolymers containing a pH‐responsive polyacid segment and a thermosensitive segment self‐assembled in the water in response to both the pH and temperature. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5239–5247     

氯代苯二酚双苯醚的合成与抑菌活性研究

为了寻求优良的苯醚类新化合物抑菌剂,本文设计合成了邻(对)苯二酚二-(2-氯-4-羟基苯基)醚,其结构均经1HNMR、IR、MS和元素分析证实,并且测试了化合物对大肠杆菌,金黄色葡萄球菌,白色念珠菌,白色葡萄球菌,变形杆菌,卡他双球菌,青枯假单胞菌的抑菌活性,初步研究结果表明:羟基的位置对活性存在较大影响,羟基的个数对试剂的抑菌活性没有明显的影响。     

COMPETITIVE NMR STUDY OF THE COMPLEXATION OF SOME ALKALINE EARTH AND TRANSITION METAL IONS WITH 12-CROWN-4, 15-CROWN-5 AND BENZO-15-CROWN-5 IN ACETONITRILE SOLUTION USING THE LITHIUM-7 NUCLEUS AS A PROBE

Abstract

⁷Lithium NMR measurements were used to determine the stoichiometry and stability of Li⁺ complexes with 12-crown-4, 15-crown-5 and benzo-15-crown-5 in acetonitrile solution. A competitive ⁷Li NMR technique was also employed to probe the complexation of Mg²⁺, Ca²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Cd²⁺ ions with the same crown ethers. In all cases, the stability of the resulting 1:1 complexes was found to decrease in the order 15-crown-5 > benzo-15-crown-5 > 12-crown-4. Ca²⁺ and Cd²⁺ ions formed the most stable complexes in the series.     

Sequential Extraction-Spectrofluorimetric Determination of Mercury Using Cryptand Ethers

Abstract

A spectrofluorimetric study of the extraction of mercury with 1,2-dichloroethane as an ion-pair formed between the cryptand 2.2.1-mercury complex and the eosinate counter-ion is described.

The detection limit for mercury is 0.7 ng/ml, and the linear working range up to 125 ng/ml of mercury.

The relative standard deviation is found to be 2.0% at the 100 ng/ml level. The proposed method has been tested for the determination of mercury in coal.