Macrocyclic Receptors for Identification and Selective Binding of Substrates of Different Nature

Molecular recognition of host/guest molecules represents the basis of many biological processes and phenomena. Enzymatic catalysis and inhibition, immunological response, reproduction of genetic information, biological regulatory functions, the effects of drugs, and ion transfer—all these processes include the stage of structure recognition during complexation. The goal of this review is to solicit and publish the latest advances in the design and sensing and binding abilities of porphyrin-based heterotopic receptors with well-defined geometries, the recognition ability of which is realized due to ionic, H-bridge, charge transfer, hydrophobic, and hydrophilic interactions. The dissection of the considered low-energy processes at the molecular scale expands our capabilities in the development of effective systems for controlled recognition, selective delivery, and prolonged release of substrates of different natures (including drugs) to their sites of functioning

Molecular Recognition of Imidazole Derivatives by Co(III)-Porphyrins in Phosphate Buffer (pH = 7.4) and Cetylpyridinium Chloride Containing Solutions

By means of spectrophotometric titration and NMR spectroscopy, the selective binding ability of the Co(III)-5,15-bis-(3-hydroxyphenyl)-10,20-bis-(4-sulfophenyl)porphyrin (Co(III)P1) and Co(III)-5,15-bis-(2-hydroxyphenyl)-10,20-bis-(4-sulfophenyl)porphyrin (Co(III)P2) towards imidazole derivatives of various nature (imidazole (L1), metronidazole (L2), and histamine (L3)) in phosphate buffer (pH 7.4) has been studied. It was found that in the case of L2, L3 the binding of the “first” ligand molecule by porphyrinates Co(III)P1 and Co(III)P2 occurs with the formation of complexes with two binding sites (donor–acceptor bond at the center and hydrogen bond at the periphery of the macrocycle), while the “second” ligand molecule is added to the metalloporphyrin only due to the formation of the donor–acceptor bond at the macrocycle coordination center. The formation of stable complexes with two binding sites has been confirmed by density functional theory method (DFT) quantum chemical calculations and two-dimensional NMR experiments. It was shown that among the studied porphyrinates, Co(III)P2 is more selective towards to L1-L3 ligands, and localization of cobalt porphyrinates in cetylpyridinium chloride (CPC) micelles does not prevent the studied imidazole derivatives reversible binding. The obtained materials can be used to develop effective receptors for recognition, delivery, and prolonged release of drug compounds to the sites of their functioning. Considering that cetylpyridinium chloride is a widely used cationic biocide as a disinfectant, the designed materials may also prove to be effective antimicrobial agents

Molecular Recognition of Imidazole Derivatives by Co(III)-Porphyrins in Phosphate Buffer (pH = 7.4) and Cetylpyridinium Chloride Containing Solutions

By means of spectrophotometric titration and NMR spectroscopy, the selective binding ability of the Co(III)-5,15-bis-(3-hydroxyphenyl)-10,20-bis-(4-sulfophenyl)porphyrin (Co(III)P1) and Co(III)-5,15-bis-(2-hydroxyphenyl)-10,20-bis-(4-sulfophenyl)porphyrin (Co(III)P2) towards imidazole derivatives of various nature (imidazole (L1), metronidazole (L2), and histamine (L3)) in phosphate buffer (pH 7.4) has been studied. It was found that in the case of L2, L3 the binding of the “first” ligand molecule by porphyrinates Co(III)P1 and Co(III)P2 occurs with the formation of complexes with two binding sites (donor–acceptor bond at the center and hydrogen bond at the periphery of the macrocycle), while the “second” ligand molecule is added to the metalloporphyrin only due to the formation of the donor–acceptor bond at the macrocycle coordination center. The formation of stable complexes with two binding sites has been confirmed by density functional theory method (DFT) quantum chemical calculations and two-dimensional NMR experiments. It was shown that among the studied porphyrinates, Co(III)P2 is more selective towards to L1-L3 ligands, and localization of cobalt porphyrinates in cetylpyridinium chloride (CPC) micelles does not prevent the studied imidazole derivatives reversible binding. The obtained materials can be used to develop effective receptors for recognition, delivery, and prolonged release of drug compounds to the sites of their functioning. Considering that cetylpyridinium chloride is a widely used cationic biocide as a disinfectant, the designed materials may also prove to be effective antimicrobial agents

Porphyrazines with annulated diazepine rings. 3.⊗ MgII Complex of 4-tert-Butylphenyl Substituted Tetra(1,4-diazepino)porphyrazine: Synthesis and Peculiar Effect of Solvent on Its Spectral Properties

5,7-Di(4-tert-butylphenyl)-6H-1,4-diazepine-2,3-dicarbonitrile, prepared by condensation of di(4-tert-butylbenzoyl) methane with diaminomaleodinitrile, affords upon template cyclotetramerization in the presence of magnesium(II) butoxide in n-butanol the MgII complex of octa-4-tert-butylphenyl substituted tetra(1,4-diazepino)porphyrazine. The strong solvent effect on its UV-Vis and 1H NMR spectral properties is rationalized in terms of dimerization occurring very likely due to intermolecular hydrogen bonding between diazepine nitrogen atoms and water molecules. The monomer is present exclusively only in diluted solutions of aprotic solvents such as dimethyl sulfoxide and dimethylformamide. Addition of water or methanol leads to dimerization. The dimer exists also in pyridine and tetrahydrofuran solutions, as well in benzene and dichloromethane containing residual water or alcohol. The UV-Vis spectrum of the monomer is typical for MgII porphyrazines and contains a single Q band at ca. 680 nm. In its 1H NMR spectrum the resonance of the CH2 protons is not observed at ambient temperatures but appear as a broad signal at 4.4-4.5 ppm above 100 °C, which is characteristic for rapid inversion of the 1,4-diazepine ring in the 6H form. The Q band of the dimer is split into two components (major at 640-645 nm and minor at 680-685 nm). The dimer gives two doublets of the diastereotopic CH2 protons (5.9-7.1 ppm for the equatorial and 4.8-6.1 ppm for the axial CH2 protons, depending on the solvent) with characteristic geminal splitting of ca. 11-12 Hz. Formation of the dimer hinders the inversion of diazepine rings and two sharp doublets are observed even above 100 °C. © ISUCT Publishing

Porphyrazines with annulated diazepine rings. 4. Synthesis and properties of Mg-II tetradiazepinoporphyrazine carrying exocyclic styryl fragments

A novel tetradiazepinoporphyrazine MgII complex bearing eight peripheral styryl substituents, [St(8)TDzPAMg(H2O)] (St = -CH=CHAr, where Ar = 4-methoxyphenyl) was prepared by template cyclotetramerization of the corresponding precursor - 5,7-distyryl substituted diazepino-2,3- dicarbonitrile - in the presence of Mg-II butoxide in n-butanol. UV-visible and H-1 NMR spectral data indicate that the complex is strongly aggregated in non-coordinating solvents (dichloromethane, chloroform, benzene), it is dimeric in pyridine, whereas it is predominantly monomeric in dimethylsulfoxide and dimethylformamide. The fluorescence response is high for solutions in which the monomeric form is prevalent, but it is strongly quenched as the content of the dimer is increased. Evidence was obtained that dimerization occurs due to intermolecular hydrogen bonding between acidic CH2 groups in the diazepine ring (6H form) of one molecule with meso- and/or diazepine N atoms of another molecule, dimerization being also contributed by the presence of chlatrated water. In the presence of fluoride anions the dimer is destroyed with formation of the monomeric species, which is changed to the 1H form upon heating, as indicated by H-1 NMR spectra

Nanoaggregates of Copper Porphyrazine in Floating Layers and Langmuir-Schaefer films

Aggregation behavior of unsubstituted copper porphyrazine (CuPaz) on the water surface was studied by analysis of compression curves, Brewster angle microscopy (BAM), and optical spectroscopy. The structure and stability of the CuPaz aqua aggregates in the floating layers are determined by hydration degree that depends on initial surface concentration and surface pressure. Langmuir-Schaefer (LS) films of CuPaz were prepared by deposition of the variously structured floating layers and studied by X-ray scattering technique and optical spectroscopy. Stable and labile structures were detected and compared with the floating CuPaz aqua aggregates. Conditions of formation of the stable four-stacked nanoaggregates in LS films were determined. A model comprising both nucleation of CuPaz on the water surface and structural transformations in the solid films is proposed