Catenar bimetallomesogens derived from quinoxaline–salicylaldimine conjugates

The preparation, characterization, and mesomorphic properties of two series of tridentate N-salicylidene-2-hydroxyanilines and their metal complexes were described. The crystal and molecular structure of bis[2-hydroxy-4-propyloxy-N-(2-hydroxy-3,4-dipropyloxybenzylidene) aniline]copper(II) were determined by means of X-ray analysis. It crystallizes in the monoclinic space group P2(1)/n and a Z=4. The geometry at Cu²⁺ ions is square pyramidal with a THF solvent molecule coordinated. The core structure was nearly flat, and the intramolecular Cu–Cu atoms were separated by ca. 3.0163(6) Å. All compounds 2a formed smectic C phases, and copper complexes 1a–Cu were not mesogenic. In contrast, compound 2e and complexes 1b–Cu, 1d–Cu, 1e–Cu, and 1e–Pd exhibited columnar phases. The lack of mesomorphism in 1e–Zn was attributed to a preferred tetrahedral over square planar geometry. A N_cell equal to 2.44–2.92, calculated from powder XRD data within a 9.0 Å thick indicated that an induced structure correlated by two catenar-shaped molecules was formed in Col_h phases.     

Studies of thermal properties of di(methacryloyloxymethyl)naphthalene–divinylbenzene (DMN–DVB) copolymer and its alkyl-bonded derivatives

This paper presents the thermal properties of highly crosslinked di(methacryloyloxymethyl)naphthalene–divinylbenzene (DMN–DVB) copolymeric microspheres containing polar groups in the structure and their alkyl-bonded derivatives. C₈ and C₁₈ alkyl chains were introduced into the aromatic rings of the DMN–DVB porous copolymer by means of the Friedel–Crafts reaction. As a source of C₈ and C₁₈ alkyl chains, octyl and octadecyl chlorides were used. It was necessary to check whether the introduction of alkyl chains into the structure of polymeric packing had an impact on its thermal properties. The studies were carried out by thermogravimetry coupled online with FTIR spectroscopy and differential scanning calorimetry in inert atmosphere (helium). It was stated that the modified materials showed 20 and 50% mass losses at higher temperatures than the non-modified one while 1% mass loss was observed at lower temperatures. Moreover, an analysis of volatile decomposition products was performed.

     

Synthesis and cytotoxicity of novel cholesterol–cobalt bis(dicarbollide) conjugates

The novel conjugates of cholesterol with cobalt – bis(dicarbollide) were synthesized by the ring-opening reactions of the cyclic oxonium derivatives of [3,3′-Co(C₂B₉H₁₁)₂]^– with the OH group of cholesterol 2-hydroxyethyl ether. The compounds obtained were tested for toxicity to glioblastoma U-87 MG cells and human embryo fibroblasts FECH-15 cells     

Progress in the study of metal–organic materials applying naphthalene diimide (NDI) ligands

1,4,5,8-naphthalenediimide (NDI) derivatives are versatile in coordination and material chemistry due to their large conjugated planar structure and special electron transfer properties. This review presents an overview of metal–organic materials derived from NDIs with their structural models, analytical techniques and potential applications outlined.     

Solubility of naphthalene in aqueous solutions of poly(ethylene glycol)–poly(propylene glycol)–poly(ethylene glycol) triblock copolymers and (2-hydroxypropyl)cyclodextrins

The solubility of naphthalene was investigated in aqueous solutions of triblock copolymers poly(ethylene glycol)–poly(propylene glycol)–poly(ethylene glycol) (PEG–PPG–PEG) and (2-hydroxypropyl)cyclodextrins. The results with solutions of the individual solubilizers were as expected: the solubility enhancement was much higher with a micelle-forming copolymer than with the non-micellizing one and with (2-hydroxypropyl)--cyclodextrin (HPBCD) than with (2-hydroxypropyl)--cyclodextrin (HPACD). Although the formation of inclusion complexes between HPACD and PEG and between HPBCD and PPG is well established, the naphthalene solubility in mixed solutions does not significantly deviate from that predicted for a mixture of independent solubilizers. Thus the interactions between HPCD and PEG–PPG–PEG copolymers are not strong enough to disrupt micelles and aggregates formed by those copolymers. In fact, slight synergetic deviations were observed with the micellizing copolymer, indicating the existence of ternary naphthalene/HPCD/copolymer interactions. For pharmaceutical applications, it is important that the solubilization efficacy of PEG–PPG–PEG copolymers and that of cyclodextrins modified by the 2-hydroxypropyl group would not be compromised if these two types of solubilizers were co-administered.     

Phase diagrams of nonadecane–decalin and nonadecane–naphthalene systems

Phase equilibria in nonadecane–decalin and nonadecane–naphthalene systems are studied. Curves of the liquidus and eutectic temperatures of these systems are calculated using the Schröder–Le Chatelier equation and the strictly regular solutions model (RSM). The calculated values and the experimental data are compared.     

Simple preparation of multi-valent cyclodextrin–carbohydrate conjugates

Several β-cyclodextrin (CD) derivatives conjugated with carbohydrates via aminohexyl linkages have been prepared. These CD-conjugates were demonstrated to be multi-valent ligands by lectin-binding assay.     

Synthesis and Properties of Axial Coordination Reaction of Unsymmetric Leucine Zinc(Ⅱ) Tetraphenylporphyrin with Pyrimidine

In recent years much work has been done on the syntheses and properties of axial coordination reaction of zinc tetraphenylporphyrins with nitrogenous donors in order to better understand the detailed molecuar mechanism of natural zincous enzymes. However,only a few studies have been reported in which the nitrogenous donors are bound to the amino acid metallotetraphenylporphyrins with unsymmetric structures. In this paper, a new unsymmetric leucine tetraphenylporphyrin, 5-(4-leucine butoxyphenyl)-10,15,20-triphenylporphyrin (H₂[Leu-TPP]) and its Zn(Ⅱ) complex (Zn[Leu-TPP]) are synthesized. Their structures are characterized by elemental analysis, UV, IR, fluorescense spectra. The changes of the electronic absorption spectra of axial coordination reaction of Zn[Leu-TPP] with pyrimidine in chloroform are investigated Coordination number (n) and equilibrium constant (β) of the reaction are measured by visible spectra techniques. The changes of standard molar enthalpy (Δ_rH_m^⊙) and molar entropy (Δ_rS_m^⊙) of the reaction are calculated. The obtained data are listed in table 1.     

Synergistic effects of alkali metals in the alkylation of naphthalene and toluene with ethene in the ArH–alkali metal systems in THF (ArH – naphthalene,phenanthrene)

The use of mixtures of metallic lithium and sodium in the naphthalene–alkali metal systems in THF leads to a synergistic acceleration of the naphthalene alkylation with ethene at room temperature and atmospheric pressure. The greatest synergistic effect is observed at a Li:Na molar ratio of 2:1. Under these conditions, the overall conversion of naphthalene into alkylation products (linear 1-alkylnaphthalenes and their dihydro derivatives) attains 88% after 24 h (a (Li + Na):C₁₀H₈ ratio is 2:1). The use of mixtures of metallic lithium and potassium in such systems results, however, in a synergistic retardation of the alkylation process. The strongest retarding effect is observed at a Li:K molar ratio of 1:1. The efficiency of the toluene alkylation with ethene in the naphthalene–alkali metal systems in THF is also increased on the replacement of lithium or sodium by their mixtures. The best results are obtained at a Li:Na molar ratio of 1:3. With this Li:Na ratio, toluene is almost quantitatively converted into linear and α-branched higher monoalkylbenzenes (24 h, (Li + Na):C₁₀H₈ = 2:1). The rate of the naphthalene alkylation with ethene in the presence of toluene is enhanced as well on an introduction of mixtures of lithium and sodium into the system. However the maximum of the activity is shifted here towards higher lithium content (Li:Na = 1:1). A similar synergistic effect of lithium and sodium was found on studying the toluene alkylation with ethene in the phenanthrene–Li–Na systems in THF (a (Li + Na):phenanthrene ratio is 3:1). An addition of potassium to sodium also considerably increases the efficiency of the toluene and naphthalene alkylation with ethene in the naphthalene-based systems. The possible mechanism of the alkali metal synergism in the above-mentioned alkylation reactions is discussed.     

Reactions of α-Aminoalkylphosphonates with Iso(thio)cyanatophosphates(phosphonates,phosphinates). Synthesis of 1,3,4-Diazaphospholidines and 1,3,4-Oxaza(thiaza)phospholines

Phenyl -aminoalkylphosphonates add to phenyl iso(thio)cyanates to give saturated heterocycles, 1,3,4-diazaphospholidin-2-(thi)ones. The reaction of diphenyl (-methylamino)benzylphosphonate with diethyl isothiocyanatophosphate involves initial formation of 1,3,4-tiazaphospholidine-2-thiones containing exo- and endocyclic phosphorus atoms. These products are readily hydrolyzed in air, yielding diethyl isothio- cyanatophosphate and phenyl hydrogen (-methylamino)benzylphosphonate. The final products of the reaction of chloromethyl isocyanatophosphonates with aminoalkylphosphonates are 1,3,4-oxazaphospholines. Phenyl aminoalkylphosphonates react with chloromethyl isocyanatophosphonates to give saturated heterocycles, 1,3,4-diazaphospholidines, whereas with chloromethyl isothiocyanatophosphonates 1,3,4-thiazaphospholines are formed.     

Synthesis of cyclodextrin–pyrrole conjugates possessing tuneable carbon linkers

Cyclodextrins are naturally occurring cyclic oligosaccharides consisting of glucose units. The main feature of cyclodextrins is the ability to accommodate various lipophilic compounds in their interior, which determines them to be popular helpers to the mankind. However, there is still a demand for new derivatives for advanced applications. Herein, we report the synthesis of β-cyclodextrin–pyrrole conjugates. Their preparation is based on an amide bond formation or copper(I)-catalysed azide-alkyne cycloaddition between β-cyclodextrin and pyrrole derivatives. The main advantage of the synthetic approach lies in the possibility to attach the substituent in β-position, because polypyrroles possessing a substituent in this position are generally more conductive than the N-substituted ones. Moreover, the presented synthetic route is general and allows tuning the properties (various types of connections and lengths) of a linker. The presented cyclodextrin–pyrrole derivatives thus open the door for new applications in the field of sensors or tissue engineering.     

The shape of protein–polymer conjugates in dilute solution

Protein–polymer conjugation can significantly affect many different aspects of protein behavior, ranging from their solution properties to their ability to form solution and bulk nanostructured materials. An underlying fundamental question is how the molecular design affects the shape of the conjugate and, consequently, its properties. This work measures the molecular configuration of model protein–polymer conjugates in dilute solution using small-angle neutron scattering (SANS) and uses quantitative model fitting to understand the shape of the molecules. Form factor measurements of four model bioconjugates of the red fluorescent protein mCherry and the polymers poly(N-isopropylacrylamide), poly(hydroxypropyl acrylate), poly(oligoethylene glycol acrylate), and poly(ethylene glycol) show that these protein–polymer conjugates are well described by a recently developed scattering function for colloid–polymer conjugates that explicitly incorporates excluded volume interactions in the polymer configuration. In the regime where the protein does not exhibit strong interactions with the polymer, modeling the protein–polymer interactions using a purely repulsive Weeks–Chandler–Andersen potential also leads to a coarse-grained depiction of the conjugate that agrees well with its scattering behavior. The coarse-grained model can additionally be used for systems with varying protein–polymer interactions, ranging from purely repulsive to strongly attractive, which may be useful for conjugates with strong electrostatic or hydrophobic attractive interactions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 292–302     

Enantiospecific Synthesis of (–)-Cuspareine and (–)-Galipinine

An enantiospecific route to the synthesis of tetrahydroquinoline alkaloids (–)-cuspareine and (–)-galipinine is reported. Coupling of an iodide derivative of D-serine with aromatic dithianes and Pd-catalyzed intramolecular C–N coupling are the key steps in the synthesis.     

Synthesis,antioxidant and anticancer screenings of berberine–indole conjugates

Research on Chemical Intermediates - A variety of heterocyclic nitrogen cores in the form of indole moieties were linked to the natural isoquinoline alkaloid molecule berberine to achieve...     

Sequence and linker dependent chiral dimerization of DNA–porphyrin conjugates

Circular dichroism (CD), UV–vis absorption, fluorescence, and resonance light scattering (RLS) spectroscopies were used to elucidate the role of the DNA sequence, linkers between DNA and porphyrin, and metal in the porphyrin coordination center on the self-assembly of DNA–porphyrin conjugates. A series of eight non-self-complementary DNA–porphyrin conjugates have been synthesized with zinc and free-base porphyrins covalently attached to the short ODNs (A₈ or T₈) via amide or phosphate linker. A small structural modification (e.g., amide linker replaced by the phosphate linker) showed a dramatic effect on the aggregation properties of DNA–porphyrin conjugates and greatly altered their spectroscopic properties. At low ionic strength, porphyrin aggregation was not observed for any conjugate. An increase in the ionic strength caused two out of eight conjugates to form chiral porphyrin dimers.     

Fluorometric determination of sugars using fluorescein-labeled concanavalin A–glycogen conjugates

The fluorescence of fluoresceinisothiocyanate-labeled concanavalin A (FITC-Con A) was quenched by forming an FITC-Con A–glycogen conjugate and dequenched upon addition of sugars to the conjugate solution due to disaggregation of the conjugate. However, fluorescence quenching was barely observed upon formation of FITC-Con A–dextran conjugate. The sugar-induced fluorescence response of the FITC-Con A–glycogen conjugate depended significantly on the type of sugar: methylated α-D-glucose and α-D-mannose both induced high and rapid responses, while the responses to D-mannose and D-glucose were moderate. In contrast, no response was observed in the presence of D-galactose due to a lack of affinity to Con A. Thus, it is apparent that D-glucose and other sugars can be detected via the fluorescence of the FITC-Con A–glycogen conjugate.      

Determination of the stability constants of Pb–(DIPSO)x–(OH)y and Pb–(AMPSO)x–(OH)y systems

In this work, complexation between lead ion and the ligands 3-[N,N-bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO) and N-(1,1-dimethyl-2-hydroxyethyl)-3-amino-2-hydroxypropanesulfonic acid (AMPSO), which are commercial pH buffers, is presented. Both ligands form complexes with lead in their pH buffer range (between pH 6.5 and 8.5 for DIPSO and between pH 8.0 and 9.0 for AMPSO). The final models and the overall stability constants, which are reported here, were determined by direct current polarography and glass electrode potentiometry [only for the Pb–(DIPSO)_x–(OH)_y system] at 25.0 °C and 0.1 M KNO₃ ionic strength. For the Pb–(DIPSO)_x–(OH)_y system, the proposed final model contains PbL, PbL₂, PbL₂(OH), and PbL₂(OH)₂ with stability constants, as log β, of 3.4 ± 0.1, 6.35 ± 0.15, 12.8 ± 0.2, and 18.0 ± 0.3, respectively. For the Pb–(AMPSO)_x–(OH)_y system, the species observed are PbL, PbL(OH), and PbL(OH)₂ with stability constants, as log β, of 2.9 ± 0.5, 9.4 ± 0.1, and 14.5 ± 0.2, respectively. For AMPSO, the possible adsorption of the ligand at the mercury electrode surface was evaluated by alternating current polarography through calculation of the capacitance of the double layer.     

Photoinduced charge separation of phenothiazine–platinum–naphthalene diimide triads linked by twisted phenylene bridges

Two triads (i.e., 3PTZ–Pt–MNDI and 10PTZ–Pt–MNDI) consisting of 3-phenothiazine (3PTZ) or 10-phenothiazine (10PTZ), bipyridine–diacetylide platinum complex (Pt), and naphthalene diimide (MNDI) chromophores linked by highly twisted biphenylene spacers have been prepared. The formation and decay of the charge-separated (CS) states in toluene were studied by use of picosecond and nanosecond laser photolysis via selective excitation of the Pt moiety. The time required for formation of the CS state, PTZ⁺–Pt–MNDI^?, from PTZ–³Pt*–MNDI was determined to be τ _CS = 280 ps for 3PTZ⁺–Pt–MNDI^? and τ _CS = 230 ps for 10PTZ⁺–Pt–MNDI^?. The lifetimes of the CS states were determined to be τ _CR1 = 75 ns (95 %) and τ _CR2 = 285 ns (5 %) for 3PTZ⁺–Pt–MNDI^? and τ _CR = 830 ns for 10PTZ⁺–Pt–MNDI^?. Formation and decay of the CS states are discussed in terms the Marcus theory and the spin-correlated radical pair mechanism.