Yulia Yu. Enakieva

Unusual Formation of a Stable 2D Copper Porphyrin Network

Copper(II) 5,15-bis(diethoxyphosphoryl)-10,20-diphenylporphyrin was obtained and characterized by means of cyclic voltammetry, electron paramagnetic resonance, Fourier transform infrared, and UV-visible spectroscopy. Three crystalline forms were grown and studied by means of X-ray diffraction methods (single crystal and powder). The highly electron-withdrawing effect of phosphoryl groups attached directly to the porphyrin macrocycle results in a self-assembling process, with formation of a stable 2D coordination network, which is unusual for copper(II) porphyrins. The resulting 2D structure is a rare example of an assembly based on copper(II) porphyrins where the copper(II) central metal ion is six-coordinated because of a weak interaction with two phosphoryl groups of adjacent porphyrins. The other polymorph of copper(II) 5,15-bis(diethoxyphosphoryl)-10,20-diphenylporphyrin contains individual (isolated) porphyrin molecules with four-coordinated copper(II) in a distorted porphyrin core. This polymorph can be obtained only by slow diffusion of a copper acetate/methanol solution into solutions of free base 5,15-bis(diethoxyphosphoryl)-10,20-diphenylporphyrin in chloroform. It converts to the 2D structure after dissolution in chloroform followed by consecutive crystallizations, using slow diffusion of hexane. A six-coordinated copper(II) porphyrin containing two axially coordinated dioxane molecules was also obtained and characterized by X-ray diffraction crystallography. The association of copper(II) 5,15-bis(diethoxyphosphoryl)-10,20-diphenylporphyrin in solution was also studied.

Synthesis of meso-polyphosphorylporphyrins and example of self-assembling

Pd-catalyzed coupling reactions have been used to prepare meso-phosphorylporphyrins. A 2D metal-organic network formed via P horizontal lineO...Zn axial supramolecular coordination of 5,15-bis(diethoxyphosphoryl)-10,20-diphenylporphyrin is the first example of a 2D framework based on phosphorylporphyrin derivatives.

Solvent-induced supramolecular assemblies of crown-substituted ruthenium phthalocyaninate: morphology of assemblies and non-linear optical properties

The information concerning the architecture of supramolecular assemblies, which are composed of ruthenium(II) tetra-15-crown-5-phthalocyaninate with axially coordinated triethylenediamine molecules, has been obtained with the application of atomic force microscopy. The ensembles are formed in Ru(II) complex solutions in chloroform and tetrachloroethane. The number of molecules and their relative orientation in supramolecular assemblies were estimated in dependence of the solvent (chloroform, tetrachloroethane) and the heating temperature. Samples fabricated after heating of the Ru(II) complexes solution in tetrachloroethane formed stable supramolecular wires of 600 nm and more in length. The third-order non-linear optical characteristics of complexes in tetrachloroethane solution were studied by the z-scanning method. Molecular polarizability of the complex is about 4.5 × 10-32 esu. The polarizability attributed to one molecule increases by a factor of 3.6 when the individual molecule assembles into a supramolecular aggregate.

Electrochemical and Spectroelectrochemical Studies of Diphosphorylated Metalloporphyrins. Generation of a Phlorin Anion Product

Two series of diphosphoryl-substituted porphyrins were synthesized and characterized by electrochemistry and spectroelectrochemistry in nonaqueous media containing 0.1 M tetra-n-butylammonium perchlorate (TBAP). The investigated compounds are 5,15-bis(diethoxyphosphoryl)-10,20-diphenylporphyrins (Ph)2(P(O)(OEt)2)2PorM and 5,15-bis(diethoxyphosphoryl)-10,20-di(para-carbomethoxyphenyl)porphyrins (PhCOOMe)2(P(O)(OEt)2)2PorM where M = 2H, Co(II), Ni(II), Cu(II), Zn(II), Cd(II), or Pd(II). The free-base and five metalated porphyrins with nonredox active centers undergo two ring-centered oxidations and two ring-centered reductions, the latter of which is followed by a chemical reaction of the porphyrin dianion to give an anionic phlorin product. The phlorin anion is electroactive and can be reoxidized by two electrons to give back the starting porphyrin, or it can be reversibly reduced by one electron at more negative potentials to give a phlorin dianion. The chemical conversion of the porphyrin dianion to a phlorin anion proceeds at a rate that varies with the nature of the central metal ion and the solvent. This rate is slowest in the basic solvent pyridine as compared to CH2Cl2 and PhCN, giving further evidence for the involvement of protons in the chemical reaction leading to phlorin formation. Calculations of the electronic structure were performed on the Ni(II) porphyrin dianion, and the most favorable atoms for electrophilic attack were determined to be the two phosphorylated carbon atoms. Phlorin formation was not observed after the two-electron reduction of the cobalt porphyrins due to the different oxidation state assignment of the doubly reduced species, a Co(I) π anion radical in one case and an M(II) dianion for all of the other derivatives. Each redox reaction was monitored by thin-layer UV-visible spectroelectrochemistry, and an overall mechanism for each electron transfer is proposed on the basis of these data.

Synthesis and Self-Organization of Zinc β-(Dialkoxyphosphoryl)porphyrins in the Solid State and in Solution

The first synthesis and self-organization of zinc β-phosphorylporphyrins in the solid state and in solution are reported. β-Dialkoxyphosphoryl-5,10,15,20-tetraphenylporphyrins and their Zn(II) complexes have been synthesized in good yields by using Pd- and Cu-mediated carbon-phosphorous bond-forming reactions. The Cu-mediated reaction allowed to prepare the mono-β-(dialkoxyphosphoryl)porphyrins 1 Zn-3 Zn starting from the β-bromo-substituted zinc porphyrinate ZnTPPBr (TPP = tetraphenylporphyrin) and dialkyl phosphites HP(O)(OR)(2) (R = Et, iPr, nBu). The derivatives 1 Zn-3 Zn were obtained in good yields by using one to three equivalents of CuI. When the reaction was carried out in the presence of catalytic amounts of palladium complexes in toluene, the desired zinc derivative 1 Zn was obtained in up to 72% yield. The use of a Pd-catalyzed C-P bond-forming reaction was further extended to the synthesis of β-poly(dialkoxyphosphoryl)porphyrins. An unprecedented one-pot sequence involving consecutive reduction and phosphorylation of H(2)TPPBr(4) led to the formation of a mixture of the 2,12- and 2,13-bis(dialkoxy)phosphorylporphyrins 5 H(2) and 6 H(2) in 81% total yield. According to the X-ray diffraction studies, 1 Zn and 3 Zn are partially overlapped cofacial dimers formed through the coordination of two Zn centers by two phosphoryl groups belonging to the adjacent molecules. The equilibrium between the monomeric and the dimeric species exists in solutions of 1 Zn and 3 Zn in weakly polar solvents according to spectroscopic data (UV/Vis absorption and NMR spectroscopy). The ratio of each form is dependent on the concentration, temperature, and traces of water or methanol. These features demonstrated that zinc β-phosphorylporphyrins can be regarded as new model compounds for the weakly coupled chlorophyll pair in the photosynthesis process.

Electrochemical and spectroelectrochemical studies of β-phosphorylated Zn porphyrins

The electrochemical and spectroelectrochemical properties of two β-phosphorylated Zn porphyrins, [2-diethoxyphosphoryl-5,10,15,20-tetraphenylporphyrinato]zinc (1) and [2-diisopropoxyphosphoryl-5,10,15,20-tetraphenylporphyrinato]zinc (2), are reported in CH2Cl2 and PhCN containing tetrabutylammonium perchlorate (TBAP) or tetrabutylammonium hexafluorophosphate (TBAPF6) as supporting electrolyte. Under certain solution conditions, three one-electron reductions are observed, with the last process being attributed to the product of a chemical reaction following formation of the porphyrin dianion. Two or three oxidations are observed for the same compounds, again depending upon the solution conditions. In some cases, two well-defined and well-separated one electron oxidations are observed but in others the first one-electron abstraction to give the porphyrin radical cation is split into two redox processes, separated from each other by 110–140 mV. This splitting of the first oxidation into two processes is attributed to linking of the two porphyrins which results when a P=O unit of the phosphoryl substituent on one porphyrin binds to the Zn(II) center of a second porphyrin, resulting in dimer formation. The interaction between the two macrocycles is discussed in terms of the difference in potentials between the two split redox processes (ΔE1/2) and the overall data is compared with that for other porphyrin dimers and bis-macrocycles reported in the literature.

Layer-by-layer assembly of porphyrin-based metal–organic frameworks on solids decorated with graphene oxide

Fabrication of metal–organic frameworks (MOFs) as films on surfaces is a challenging and actively developed field in the context of potential applications of surface-integrated MOFs (SURMOFs) in sensing, catalysis and molecular electronics. Herein, we report a method for the preparation of composites of graphene oxide (GO) and zinc tetracarboxyphenyl porphyrin SURMOFs, which are potentially useful as synergetic catalysts on planar solid supports. The SURMOF films were assembled via layer-by-layer coordination of zinc porphyrins with ZnAc2 clusters on the ultrathin surface coatings of GO. We found that non-covalent adsorption of zinc acetate on the GO films is essential for anchoring porphyrin molecules in the growth-initiating template layer. UV-vis spectroscopy provided evidence for a stepwise assembly of the deposited SURMOF films. By using a combination of X-ray diffraction, scanning electron microscopy and atomic force microscopy methods, we show that the resulting GO-associated SURMOFs exhibit a leaflet-like planar morphology with out-of-plane periodicity. Because of the influence of the well-defined surface geometry, the molecular organization in thin SURMOFs is different from that of synthetic bulk materials with a similar composition. The results of BET method measurements suggest that the fabricated SURMOF films have exceptionally large surface areas and adsorption capacities. Our results provide a basis for new types of composite SURMOF structures using GO surface coatings as growth-guiding scaffolds for metal–organic coordination networks integrated with various solid supports.

Supramolecular Architectures Based on Phosphonic Acid Diesters

GRAPHICAL ABSTRACT Abstract The interest of phosphonic acid dialkyl esters for generation of metal-organic materials is discussed using derivatives of porphyrin and 1,10-phenanthroline series as representative examples.

Synthesis of porphyrin-bis(polyazamacrocycle) triads via Suzuki coupling reaction

Suzuki–Miyaura cross-coupling reaction has been used for the synthesis of tricyclic architectures based on trans-A2B2-porphyrins and bisaminal-protected polyazamacrocycles which are linked directly or by a p-phenylene spacer. This modular approach allowed the synthesis of ligands with various substituted porphyrin macrocycles and bisaminal-protected tetraazamacrocycles possessing different cavity sizes. These molecules can be assembled into dimers using a DABCO linker. Deprotection of these compounds afforded porphyrin-bis(polyazamacrocycle) triads.

Gallium(III) and Indium(III) Complexes with meso-Monophosphorylated Porphyrins: Synthesis and Structure. A First Example of Dimers Formed by the Self-Assembly of meso-Porphyrinylphosphonic Acid Monoester

The synthesis and structural characterization, both in solution by means of 1H and 31P NMR and UV-vis spectroscopies and in the solid state by X-ray diffraction on single crystal, of a series of gallium(III) and indium(III) meso-mono(diethoxyphosphoryl)porphyrins bearing different peripheral substituents as well as the corresponding monoesters and phosphonic acids are reported. This work describes the first example of the X-ray structure of a self-assembled dimer formed via strong binding between the oxygen atom of the phosphonate substituent and the gallium(III) cations of adjacent porphyrin molecules [Ga-O = 1.9708(13) Å].