Journal of Inclusion Phenomena and Macrocyclic Chemistry最新文献

Tetrakis(l,3-dihydrobenzoxazine) calix[4]resorcinarenes 4–6 were synthesized via the Mannich reaction from the corresponding resorcin[4]arenes 1–3 with S-(−)-α-methylbenzylamine or R-(+)-α-methylbenzylamine and formaldehyde (aq.). The products were well characterized by FT-IR, ¹H NMR, ¹³C NMR spectroscopies and single crystal X-ray diffraction analysis. Molecular structures of compounds 4, 5 and 6 showed the same R/S configuration to the starting amines. Compounds 4–6 are stabilized by a collar of intramolecular hydrogen bonding networks between the hydroxy groups and the oxygens from the benzoxazine rings. Compounds 4 and 5 could encapsulate the guest molecules of acetone and dichloromethane, respectively. The UV and ¹H NMR titration experiments were performed to study the host-guest chemistry between compound 4 and small acetone molecules, indicating that compound 4 exhibited encapsulation behavior towards acetone molecules through hydrogen bonding interactions.

Nanoporous carbon materials have always presented a special interest due to their properties, which include adsorption (especially of gases), catalyst activity, fluorescence, and luminescence. Their porosity leads to a high surface area, making them suited for assisting processes, such as synthesis (especially carboxylation and electrolytic reduction), catalysis (particularly electrocatalysts and photocatalysis), and separation. Considering these features, carbon nanotubes, graphene oxide, and graphene quantum dots have been extensively investigated for pharmaceutical applications. Coming from either organic, inorganic or synthetic precursors, the nanoporous carbon composites are of great value as adsorbent for the removal of various pollutants. Apart from the removal of pollutants, nanopores serve to separate single stranded and double stranded DNA in solution and rapid DNA sequencing. While the size of the pores depends on the method used for preparation, from a usage standpoint, the nanopores are micropores ((< ! 2 ~ text {nm})), mesopores ((2 !- ! 50 ~text {nm})) and macropores ((> ! 50 ~ text {nm})). The methods of investigation related with nanoporous carbon materials often include X ray diffraction, scanning electron microscopy, fourier transform infrared spectroscopy, transmission electron microscopy, X ray photoelectron spectroscopy, thermogravimetric analysis and X ray powder diffraction. This review summarizes the most recent studies in developing nanoporous carbon materials for various pharmacautical applications including bio-sensing, drug delivery, tissue engineering, biomedicine, gene transfection or cancer therapy. New porous carbon materials, including metal organic frameworks, carbon dots and nanotubes, have been detailed in this review.

In biological systems, biomolecules achieve sophisticated functions based on both thermodynamic control and kinetic control. In contrast, in artificial supramolecular systems, molecular recognition behaviors in host–guest systems or self-assembly processes under thermodynamic control have been widely investigated for several decades. Recently, kinetic control of these processes has attracted more interest. This review describes three approaches for the kinetic control of supramolecular systems based on coordination chemistry. The discussion first focuses on the kinetic control of guest uptake of host–guest systems. The guest binding kinetics (i.e., guest uptake/release rate) can be basically controlled by the change in the aperture sizes of the host molecules. The second part provides representative examples of unveiling guest uptake/exchange mechanisms for a variety of supramolecular host–guest systems, which is important for the rational design of host molecules and prediction of their specific functions for future studies. The kinetic control of metal-assisted self-assembly processes is also introduced in the last part. The discussion especially focuses on investigation of the self-assembly pathway, control of the kinetic stability of self-assembled complexes, and the speed tuning of self-assembly processes by modulating the individual metal–ligand exchange rate.

The monitoring of shifting of the redox potential of macrocyclic complexes towards anodic or cathodic regions, which acts as a mediator in many electrocatalytic events, is made possible by inserting electron donating or electron withdrawing group into their frameworks. Herein, using a template strategy, two [14]-membered N₄-macrocyclic complexes (denoted as complex A and complex B) with similar molecular cores but different phenyl moieties were prepared and characterized using multiple characterization techniques. The characterization results suggested a saddle-shaped geometry for these complexes, which might be due to the steric repulsions between the benzenoid and amidic moieties on the macrocyclic framework, as also supported by theoretical computations. Further, to investigate the electrochemical behaviors of these complexes, cyclic voltammetry was used and found that the Fe^3+/2+ redox potential was systematically shifted in anodic direction with the increment of phenyl moieties on the [14]-membered N₄-macrocyclic core. DFT calculations indicated the down-shifting in the most occupied molecular orbital due to the increased phenyl conjugation, which could be correlated with the shifting of Fe^3+/2+ redox potential. Biological evaluation of these complexes has also been carried out.

Purpose

Due to the mentionable importance of macrocyclic compounds different metal complexes with a new macrocyclic ligand have been prepared in this study. To materialize this expectation, a new N-pendent derivative L_AZ was prepared by the interaction between isomeric ligand, L_A (a C-chiral isomer of 3,10-C-meso-Me₈[14]ane) and CH₃I at 1:4 ratio under reflux in methanolic solution. L_AZ underwent complexation with Ni(II), Cu(II) and Zn(II) salts to form four coordinated square planar orange [NiL_AZ](ClO₄)₂ square planar violet [CuL_AZ](ClO₄)₂, and five coordinated square pyramidal white [ZnL_AZ(NO₃)](NO₃) complexes respectively. The axial addition reactions on [CuL_AZ](ClO₄)₂ with NCS⁻, NO₃⁻, NO₂⁻, Cl⁻, Br⁻ and I⁻ afforded different colored six coordinated octahedral axial addition products: purple [CuL_AZ(NCS)₂]; pink [CuL_AZ(NO₃)(ClO₄)]; pink [CuL_AZ(NO₂)(ClO₄)]; pink [CuL_AZCl(ClO₄)]; pink [CuL_AZBr₂] and deep blue [CuL_AZI(ClO₄)] respectively.

Methods

The compounds were characterized on the basis of different analytical parameters. Antibacterial and antifungal activities of newly prepared compounds were investigated by using standard methods.

Results

The metal complexes of L_AZ showed different geometries with required coordination. Theses complexes also showed electrolytic behavior in different solvents. The ligand L_AZ and its metal complexes exhibit moderate antimicrobial activities toward different phytopathogenic bacteria and fungi.

A novel derivatives of tetraazacalix[4]arene[2]triazine-based catalysts for enantioselective Michael addition reactions of nitroolefins and diketones were presented. Chiral moieties were connected to the heteroatom-bridged calix-triazin scaffold by reactions of (S)- or (R)-(+)-1-(1-Naphthyl)ethylamine with tetraazacalix[4]arene[2]triazine. To utilize the catalytic activity of the chiral catalysts, diketones reacted with a wide variety of trans-β-nitrostyrenes in Toluene, respectively, obtaining the Michael products in excellent yields and enantiomeric excesses (up to 96% yield and 99% ee).

Graphical abstract

Cyclodextrins (CDs) and their chemical derivatives are well-known as effective carriers for low-water-soluble molecules for pharmaceutical and other industrial applications. We have carried out the synthesis of PEGylated β-CDs through ether chemical bond linkage between β-CD and poly(ethylene glycol) methyl ether (MPEG). The combination of β-CD with poly(ethylene glycol) will benefit from PEG’s properties including high water solubility, nontoxicity, non-immunogenicity, biocompatibility, and biodegradability. The synthesis proceeded through three steps: (a) tosylation of MPEG; (b) deprotonation of hydroxyl groups of β-CD using NaH; and (c) the combination of the above two intermediates through the S_N2 mechanism to obtain the MPEG-β-CD compounds. The products were confirmed by MALDI-TOF mass spectrometry, and their structures were analyzed using ¹H 2D COSY and ROESY NMR methods. It was found that the site of PEGylation occurred on the (OH)6 site of β-CD. The inclusion property of the MPEG-β-CDs was demonstrated by forming inclusion complexes with 1-fluroroadamantane. We anticipate that the newly added properties of the MPEG to β-CD promote their pharmaceutical and other industrial applications.

The impact of β-CD on 4 benzophenones (BPs) [namely, BP, HBP, d-HBP, t-HBP] and its resultant effect on the ultraviolet protection factor (UPF) of poplin cotton fabric are tested. Drastic enhancement in the UPF values for BPs:β-CD complexes treated fabrics is noticed (than the untreated/fabric treated with free BPs). The impact of β-CD on the tautomerism of hydroxyl substituted BPs are demonstrated by investigatingthe guest (BPs:absorbers)-host(β-CD:enhancer) process. Orientation of -OH substituted benzene towards 1^° rim and positioning of C = O group of BPs in the middle of β-CD could be attributed to the steric effect driven preference of the guest molecules for achieving a rigid fit. Rigid fit rendered by β-CD improves the photostability of BPs and dissipates UVR efficiently through keto-enol tautomerization. With the highest UPF (= 51) d-HBP:β-CD complex is identified as a potential application material for producing sun-protective clothing.

Host–guest complexation of betulin 3,28-diphthalate (DPhB), that is poorly soluble in water and is an amphiphilic compound, with β-cyclodextrin (β-CD) was studied by spectrophotometry in 10 mM sodium tetraborate solution at pH 9.18 (ionic strength of 20 mM). This interaction was found to lead to a bathochromic shift of the DPhB absorption bands and an increase in absorption. Using the first derivative spectra of solutions with a fixed concentration of DPhB (0.01 mM) and a variable concentration of β-CD (0–10 mM), the logarithms of binding constants for 1:1 and 1:2 complexes of DPhB with β-CD were determined with 95% confidence intervals at 25 °C: 4.13 (4.03–4.20) and 6.30 (4.72–6.59). To eliminate systematic errors, the assumption that the equilibrium CD concentration in solution was equal to its total concentration was not used in this study. The obtained value for the 1:1 complex is consistent with the value determined earlier by affinity capillary electrophoresis (ACE), while the constant for the 1:2 complex is slightly lower than that from ACE, which can be explained by a higher concentration of DPhB; however, the use of this concentration is reasonable to reduce the measurement error. DPhB was found to form micelles at pH 9.18 and the critical micelle concentration (CMC) measured was 0.13 mM. This is a possible reason why the experimental points obtained at higher concentrations of DPhB than CMC are not described within the framework of theories that take into account the formation of 1:1 or both 1:1 and 1:2 complexes.