G. M. Mamardashvili

Binding ability of Zn-tetraarylporphyrins with two, four and eight 4-(4-(3,6-bis(t-butyl)carbazol-9-ylphenyl)-1,2,3-triazole end groups towards N-containing substrates of different nature

The binding ability of Zn-tetraarylporphyrins with two, four and eight 4-carbazolylphenyl-1,2,3-triazole end groups towards 1,4-diazabicyclo[2.2.2]octane, pyridine and 1,2,3-triazole in toluene was studied by spectrophotometric and 1H NMR titration. It was determined that due to a good geometric match of the ligand size to the size of the intramolecular cavities of the porphyrinic receptor, and by the existence of additional π–π and/or hydrogen bonding interactions between the ligand and the triazole fragments of the porphyrin, the Zn-tetraarylporphyrin with eight 4-carbazolylphenyl-1,2,3-triazole end groups could be used as an effective receptor for 1,2,3-triazole and other small heterocycles such as pyridine. Taking into account the fact that binding is accompanied by a clear and easily identifiable response in the UV–vis spectra of the reaction mixture, this metalloporphyrin could be considered as a molecular optical sensing device for small heterocyclic substrates.

Calix[4]arene-porphyrin molecular receptors for selective binding of ethylenediamines

A new zinc calix[4]arene-bis-porphyrinate was synthesized and its 1 : 1 and 1 : 2 complexation reaction with ehtylenediamine, diethylenediamine, and triethylenediamine in toluene at 298 K was studied by spectrophotometric titration and 1H NMR.

Tetrapyrrolic compounds as hosts for binding of halides and alkali metal cations

In this paper the binding of halides and alkali metal cations with porphyrin hosts is reported. The halide ions are complexed with diprotonated porphyrin macrocycle with high affinity and stable complexes of 1:1 and 1:2 structures with halide ions are formed. Strong (up to 300 times) quenching of the porphyrin fluorescence has been found upon the titration of porphyrin solutions with iodide ions. It was established that both static quenching upon formation of the non-fluorescent complex and dynamic diffusion-controlled quenching took place. It is shown that the halide ions binding isotherms can be linearized with double-logarithmic plots. The alkali metal cations are trapped with mono-meso-arylporphyrins containing a conformationally mobile complexing polyether fragment on the benzene ring with a terminal pyridine ring. The alkali metal cation binding constant depends on the polyether chain length. The five-membered (n = 5) polyether chain provides very high binding selectivity for potassium over lithium or sodium. The potassium complexation constants 3.6 × 105 and 7.2 × 104 M-1 have been obtained for Zn2+ complex and diprotonated porphyrin, respectively. For signaling of the alkali cation complexation, it is proposed to use the binding between the terminal pyridine ring with either the Lewis acidic site (chelated Zn2+ ion) or the diprotonated macrocycle core (H4P2+) acting as salt bridging site.

The effect of a solvent on complexation of Zn porphyrinates with pyridine

Spectrophotometric titration was used to study complexation reactions of Zn 2,3,7,8,12,13,17,18-octaethylporphyrinate and Zn 5,10,15,20-tetraphenylporphyrinate with pyridine in binary solvents toluenemethanol and toluene-ethanol at different alcohol concentrations at 20°C. Capability of both porphyrinates to give complexes with pyridine in a binary solvent, i.e., toluene-monobasic alcohol, was found to decrease by more than one order of magnitude as the alcohol concentration increased from 0 to 1 mole fraction. The effect of the solvent polarity and extent of its association due to hydrogen bonds on the complexing capability of both porphyrinates was discussed.

Complexation of zinc octaalkylporphyrin with mono-, di-, and triethylenediamines in toluene

The complexation of zinc octaalkylporphyrin with mono-, di-, and triethylenediamines in toluene was studied by spectrophotometry using the molar ratio method and by 1H NMR. The effect of the structure of the two-center organic base on the formation of 1 : 1 or 2 : 1 metal porphyrin-ligand complex was established. The stability constants of the resulting complexes were calculated and the concentration ranges of their existence were determined.

The effect of the structure of aliphatic diamines on their interaction with zinc porphyrinates

The complex formation of zinc 2,8,12,18-tetramethyl-3,7,13,17-tetraethylporphyrinate, 5,17-bis(zinc 2,8,12,18-tetramethyl-3,7,13,17-tetraethyl-10-phenylporphyrinate)-25,27-dimethoxy-26,28-dihydroxycalic-[4]-arene, and 5,17-bis(zinc 2,8,12,18-tetramethyl-3,7,13,17-tetraethyl-10-phenylporphyrinate)-25,27-dimethoxy-26,28-crwon-[6]-calix-[4]-arene with 1,2-diaminoethane, 1,3-diaminopropane, and 1,2-di-(dimethylamino)ethane in toluene was studied by spectrophotometric molar ratio method and 1H NMR. The effect of the diamine structure on the formation of “internal” and “external” porphyrinate-ligand complexes of the composition 1 :1 and 1 :2 was established. The stability constants of the complexes obtained were calculated and the concentration intervals of their formation were determined.

Reactions of Cu(II) and Co(II) acetates, acetylacetonates, and valinates with α,α-Dipyrrolylemethen

The reactions of Co(II) and Cu(II) acetates, valinates, and acetylacetonates with 3,3′,5,5′-tetramethyl-4,4′-dibutyldipyrrolylmethen (HL) in DMF at 298.15 K are studied by spectrophotometric method. The compositions and thermodynamic constants of formation of the Cu(II) and Co(II) complexes are determined using the methods of molar ratios and continuous changes. With an excess in Cu(II) acetate or acetylacetonate, the formation of mixed-ligand complexes CuL(OAc) and CuL(Acac), respectively, was observed, whereas CuL2 complex was detected in the case of HL excess. At either ratio of the reagent concentrations, reactions of Co(II) acetate and acetylacetonate with HL always afforded CoL2 complex, while in the case of Cu(II) and Co(II) valinates, only one amino acid ligand was replaced to give ML(Val) complexes (HVal is valine). The chelating capability of the ligand HL toward the Cu2+ ion was found to be higher than that toward the Co2+ ion.

Complexation of Zn Arylporphyrinates with Leucine Methyl Ester

Extra coordination of L-leucine methyl ester with seventeen different Zn arylporphyrinates is studied by spectrophotometric titration and capability of Zn porphyrinates with the active OH groups to recognize LeiOCH3 in toluene at 20°C is determined. The formation of associates of the composition amino acid ether–porphyrinate depending on the substituent positions in a macrocycle is studied by the 1H NMR method. The most strong donor–acceptor bonds between Zn porphyrinate and LeiOCH3 are observed in the case of pyridine-substituted porphyrins and porphyrins with phenyl rings containing electron-donor substituents in the m-position. The best recognizing capabilities with respect to leucine are shown by Zn porphyrinates with di- and tetra-4-OH-phenyl substitution in the meso-positions of a macrocycle.

Molecular recognition of nitrogen – containing bases by Zn[5,15-bis-(2,6-dodecyloxyphenyl)]porphyrin

Abstract By means of spectrophotometric titration and 1H NMR spectroscopy, the selective binding ability of the Zn-5,15-bis-(2,6-dodecyloxyphenyl)porphyrin towards nitrogen containing organic molecules of various nature has been studied. It has been found that the presence of long alkoxy substituents at the ortho-positions of the Zn-porphyrin phenyl rings prevents the axial coordination of tertiary amines and, conversely, creates favourable conditions for binding of a primary diamine due to the presence of additional binding sites, namely the oxygen atoms of the ortho–ortho′- dodecyloxy substituents of the meso phenyl groups. The formation of stable complexes with multiple binding sites has been confirmed by DFT quantum chemical calculations and two-dimensional NMR experiments.

Synthesis of calix[4]arene-bis(tin(Iv)porphyrins) and supramolecular complexes on their basis

Selective substitution of one of the two trans hydroxy groups of calix[4]arene-bis(porphyrinatotin(IV)) resulted in supramolecular tetramer assemblies based thereon with parallel and perpendicular arrangement of tetrapyrrole macrocyclic rings, which were characterized by UV spectroscopy, 1H NMR, and elemental analysis data.