Journal of Inclusion Phenomena and Macrocyclic Chemistry最新文献

Distinct association constants related to including the phenylurea herbicide diuron into β-CD were reported along experiments carried out over the years. From the literature, we found association constants for this particular system corresponding to 125 M⁻¹ (2002), 750 ± 50 M⁻¹(2004), 175.86 ± 4.21 M⁻¹(2012), and 269.73 M⁻¹ (2019). Since the association constants are essential parameters for CD-based systems, we decided to apply the recently developed theoretical multi-equilibrium GFN2-xTB quantum approach to determine the most representative value for diuron included in β-CD. Within the additional investigation of linuron and neburon, other phenyl urea herbicides comprising chlorine atoms attached to the aromatic ring investigated within the experimental study published in 2002, we apply our theoretical approach to treat 16,308 arrangements in aqueous media. We concluded that an experimental binding constant equal to 750 ± 50 M⁻¹ is coherent to the diu@β-CD system. Furthermore, the GFN2-xTB/multi-equilibrium approach suggests that K (lin@β-CD) < K(neb@β-CD) < K (diu@β-CD) and distinct guest orientations contribute to each binding constant in solution.

Graphical Abstract

Two new zinc(II) coordination polymers [Zn(bpba)₂(NO₃)₂]_n (1) and [Zn(bpba)(SO₄)]_n•2nH₂O•nDMF (2) were successfully synthesized by reacting zinc(II) ions with bis(4-pyridyl)benzylamine (bpba) containing different counter anions (NO₃⁻ and SO₄²⁻). The resulting polymers were fully characterized using various experimental techniques: single-crystal X-ray diffraction analysis, elemental analysis, infrared spectra, ultraviolet/visible spectra, and thermogravimetric analysis. Single-crystal X-ray analyses revealed that the zinc(II) ions in 1 and 2 are tetra-coordinated and adopt a distorted tetrahedral geometry. Polymer 1 exhibits a one-dimensional helical chain structure, which extends into two-dimensional supramolecular networks through hydrogen bonding and C-H•••π interactions. Polymer 2 adopts a three-dimensional network structure resulting from the coordination of zinc(II) and sulfate ions as well as bpba ligands. An investigation of the solid-state photoluminescence properties of the polymers at room temperature revealed that their emissions were redshifted compared with those of the free ligand, which is attributed to metal-perturbed intra-ligand charge transfer.

Introduction

In attempt to find new type of artificial receptors towards neurotransmitters, NMR studies were carried out on the supramolecular complexation of serotonin and dopamine with a dioxa-pentaaza-cyclophane derived from diethylenetriaminepentaacetic acid (known as DTPA) in neutral aqueous media, in which the macrocycle composed of three phenylene groups is negatively charged with three anionic -CH₂ CO₂⁻ arms, whereas the aromatic neurotransmitters carry a cationic -NH₃⁺ group.

Objectives

The main objective of the present study is to find new types of artificial receptors towards neurotransmitters.

Methods

Aromatic protons in the cyclophane exhibit up-field shifts due to the ring current effect of the neurotransmitters in NMR titration; the through-space interaction is confirmed by NOESY (Nuclear Overhauser Enhancement and Exchange Spectroscopy). Geometry optimization shows that the macrocycle can encapsulate either neurotransmitter molecule to form a 1:1-inclusion complex in which electrostatic and hydrogen-bonding interaction operate between the functional groups of the component molecules.

Results

The through-space interaction is stronger for serotonin because of its better fitness to the macrocyclic cavity. The thermodynamic stabilities of the complexes are about 20 M⁻¹ in D₂O and are very slightly decreased in the coexistence of electrolytes.

Conclusion

The complexation is promoted by the electrostatic and hydrogen bonds. The resulting ion-pair is stabilized by the successive encapsulation, which protects the weak bonds against the electrostatic field of the electrolyte. The combination of multiple types of interacting sites may be crucial in the design of receptors that can function under isotonic conditions.

Stability constants of supramolecular host-guest complexes between water-soluble sodium salts of thiacalix[4]arene sulfonic acid (TCS), thiacalix[4]arene methylphosphonic acid (TCPA), calix[4]arene methylene-bisphosphonic acid (CMBPA) (hosts) and the antiretroviral drugs Tenofovir (TFV) and Emtricitabine (FTC) (guests) were determined by HPLC method in 90/10, (v/v) water/acetonitrile solution (K_A values 1.2 × 10³ − 9.3 × 10³ M^− 1). DFT calculations show that the conformationally flexible calixarenes adopt the conformation (cone or 1,3-alternate preferably) suitable to form a number of intermolecular hydrogen bonds with the guest molecules. The water-soluble, low cytotoxic, synthetically available anionic calixarenes TCSA, TCPA and CMBPA with practically unlimited possibilities of chemical modification have the prospect of application in formulations of the antiretroviral drugs and the creation of vectors for their delivery systems.

Considering that many vitamins can be easily degraded, developing ways to avoid the degradation process and the availability of these vitamins is essential. Thus, this study aims to use layered zinc hydroxysalt (LHS) as a slow-release option that provides thermal stability for administering vitamins. Two compounds were synthesized, LHS/B3-1, which presented basal spacing of 9.63 Å, corresponding to a vitamin monolayer, and LHS/B3-2, which is a mixture of two phases, one with a basal distance of 9.92 Å and a secondary one with a basal distance of 15.43 Å, corresponding to a vitamin monolayer and bilayer, respectively. After intercalation, an increase of 175 °C in the thermal stability of vitamin B3 was observed, occasioned by the interaction with the layers of the matrix. Vitamin B3 was slowly released from LHS/B3-1 and LHS/B3-2, and 68.8% and 56.9% were released in 44 h, respectively. The release of the vitamin from LHS/B3-1 and LHS/B3-2 was divided into three stages. The results suggest that surface diffusion is initially involved in the release of B3 from intercalation products, where the anion dissociates from the surface of LHSs, followed by B3 release controlled by a diffusion process via intra-particle or surface diffusion.

Graphical Abstract

TADDOL5 possesses the ability to form complexes with the heterocyclic guest species DIO, PYR, PIP and MOR, and 1:1 (PYR, PIP, MOR) and 2:1 (DIO) H:G inclusion compounds were isolated after host crystallization experiments from these solvents. Guest competition experiments revealed that PIP and MOR were preferred by TADDOL5, while PYR and DIO were less favoured; the selectivity of this host compound for these guests was thus demonstrated to be in the order PIP > MOR > PYR > DIO. SCXRD analyses explained this host preferential order: PIP experienced the shorter and more linear (host)O‒H···N(guest) hydrogen bond with TADDOL5, followed by MOR and PYR. DIO was also retained in the crystal of the complex by means of a hydrogen bond with TADDOL5 of the (host)O‒H···O(guest) type. Hirshfeld surface investigations did not provide further understanding for the host selectivity behaviour when crystallized from mixed guests, but the relative thermal stability of the complex with preferred PIP formed the most stable complex while the inclusion compound with DIO, least favoured, was characterised by the lowest stability.

Graphical abstract

In this study, we report the synthesis and structural characterization of a new chiral macrocyclic dilactam (1) using (R)-phenylglycinol as a key building block. Macrocyclic polyether dilactams, such as this compound, have garnered attention for their ability to form complexes with cations, anions, heavy-metal ions, and neutral organic molecules, displaying potential biological applications as molecular or ion receptors and antibiotics. Building on our expertise in synthesizing chiral piperidine derivatives for alkaloid synthesis, we employed efficient diastereoselective strategies to develop this macrocycle. The complete structural assignment, crucial for correlating structural patterns with biological activity, was achieved through two-dimensional NMR spectroscopy and X-ray diffraction analysis. This work provides valuable insights into the design of diaza-crown ethers with potential applications in supramolecular systems and medicinal chemistry.

Diamide macrocycles are valuable intermediates for the synthesis of aza crown compounds as well as more complex ligands such as various cryptands and cryptohemispherands. Their versatility in many fields, such as chemistry, biochemistry, biophysics, biology, agriculture, industry, medicine, molecular diagnosis, sensors, and phase transfer catalysts, has captured the interest of many. In the first step, 2,4-dimethylphenol was converted to the oxythiobis [4,6-dimethylphenyl] (1) by reacting with thionyl chloride. Then, oxythiobis [4,6-dimethyl phenoxy methyl acetate] (2) was obtained from the reaction of oxythiobis [4,6-dimethylphenyl] (1) with methyl chloroacetate. The reaction of oxythiobis [4,6-dimethyl phenoxy methyl acetate] (2), with a diethylenetriamine, produced the tri-aza dibenzo sulfoxide macrocyclic diamides (3). Bis [tri-aza dibenzo sulfoxide macrocyclic diamides] (4) was prepared from the reaction of tri-aza dibenzo sulfoxide macrocyclic diamides (3) with a suitable active compound such as diacid or dichloride. The structures of all synthesized compounds were characterized by ¹H NMR, ¹³C NMR, FT-IR, and mass spectra.

Two pairs of diastereomerically pure calix[4]arene phosphoric acid derivatives with ABHH and ABCH substitution patterns were synthesized via phosphorylation and phosphotropic rearrangement on the narrow rim. These new cone-shaped, inherently chiral calixarenes were tested as organocatalysts in the stereoselective aza-Diels–Alder reaction of imines with Danishefsky's diene, as well as in the stereoselective epoxide ring opening.

Pillar[n]arenes are a relatively new family of macrocyclic molecular hosts, consisting of methylene-linked phenol-based monomers attached in a para-substituted configuration. The macrocyclic nature of these molecules provides a well-defined internal cavity, into which smaller guest molecules can be included to form supramolecular host-guest inclusion complexes. The para-oriented attachment yields relatively rigid cylindrical or pillar-like molecular and cavity shapes, hence the name. In addition to the unique shape of these cavities (compared to the related meta-substituted calixarenes, for example), the aromatic nature of the cavity walls also contributes to distinctive host properties of pillar[n]arenes and guest affinities. Neutral pillar[n]arenes, such as those with alkyl substituents, are generally insoluble in water, and thus their host properties are studied in nonaqueous media. This review article will provide a comprehensive summary of the reported host binding studies of pillar[n]arenes in nonaqueous solution. A wide range of specific pillar[n]arenes have been studied in this way, as have a wide variety of sizes and types of guests. The emphasis will be on studies in which the value of the binding association constant K_a was measured and reported, to consider the effect of guest size, shape, and nature and the host size and substituents on the binding ability of pillar[n]arenes. The main objective of the paper is to provide a summary and overview of the host binding abilities of this fascinating family of molecular hosts in nonaqueous solution.

Graphical abstract