Victor N. Nemykin

The key role of peripheral substituents in the chemistry of phthalocyanines and their analogs

The preparation and optical properties of peripherally substituted phthalocyanines and their analogs (i.e. naphthalocyanines, anthracyanines, aza-analogs of phthalocyanines, and tetraazaporphyrins) have been widely discussed. This review highlights methodologies that have been published in poorly known and mostly unavailable Russian journals.

A new highly fluorescent and symmetric pyrrole-BF2 chromophore: BOPHY.

The new fluorescent chromophore BOPHY can be readily synthesized in two steps from commercially available reagents via the coupling of pyrrole-2-carboxaldehyde with hydrazine followed by reaction with BF3. The resultant symmetric and dimeric tetracycle is composed of two BF2 units in six-membered chelate rings appended with pyrrole units on the periphery. The quantum yields of fluorescence for the unmodified compound and the tetramethyl variant are near unity, with values of 95 and 92%, respectively, in CH2Cl2. We have probed the electronic structure of this compound via cyclic voltammetry and density functional theory analysis.

Interpretation of the UV−vis Spectra of the meso(Ferrocenyl)-Containing Porphyrins using a TDDFT Approach: Is Gouterman’s Classic Four-Orbital Model Still in Play?

The vertical excitation energies of H(2)TPP [TPP = 5,10,15,20-tetraphenylporphyrin(2-)], H(2)FcPh(3)P [FcPh(3)P = 5-ferrocenyl-10,15,20-triphenylporphyrin(2-)], cis-H(2)Fc(2)Ph(2)P [cis-Fc(2)Ph(2)P = 5,10-bisferrocenyl-15,20-diphenylporphyrin (2-)], trans-H(2)Fc(2)Ph(2)P [trans-Fc(2)Ph(2)P = 5,15-bisferrocenyl-10,20-diphenylporphyrin(2-)], H(2)Fc(3)PhP [H(2)Fc(3)PhP = 5,10,15-trisferrocenyl-20-phenylporphyrin(2-)], and H(2)TFcP [TFcP = 5,10,15,20-tetraferrocenylporphyrin(2-)] were investigated using a time-dependent density functional theory (DFT) approach and compared to their experimental UV-vis spectra in the 10,000-30,000 cm(-1) region. It was shown that the lowest energy transitions in meso(ferrocenyl)-containing porphyrins have predominantly ferrocene-to-porphyrin charge transfer character, while the porphyrin-centered π-π* transitions predicted by the Goutermans classic four-orbital model still have the largest intensities in the UV-vis region. The number of predominantly ferrocene-to-porphyrin charge transfer transitions increases with the number of ferrocene substituents and becomes dominant in H(2)TFcP.

Tetraferrocenylporphyrins as active components of self-assembled monolayers on gold surface

Novel tetraferrocenylporphyrins-containing self-assembled monolayers were prepared employing two different approaches. Self-assembled monolayers were characterized using UV-Vis spectroscopy and cyclic voltammetry (CV) whereas their photoelectrochemical properties were investigated by photocurrent generation (PG) experiments.

Design, preparation, X-ray crystal structure, and reactivity of o-alkoxyphenyliodonium bis(methoxycarbonyl)methanide, a highly soluble carbene precursor.

The preparation, X-ray structure, and reactivity of new, highly soluble, and reactive iodonium ylides derived from malonate methyl ester and bearing an ortho substituent on the phenyl ring are reported. These new reagents show higher reactivity than common phenyliodonium ylides in the Rh-catalyzed cyclopropanation, C-H insertion, and transylidation reactions under homogeneous conditions.

New developments in chemistry of organometallic porphyrins and their analogs

In this mini-review, new developments in chemistry of organometallic porphyrins and their analogs reported between 2007 and mid 2012 have been discussed. Synthetic strategies for preparation, as well as properties of metallocenyl-type compounds in which organometallic substituents connected to the porphyrinoid via (i) axial coordination; (ii) covalent bond to meso- or β-pyrrolic position; or (iii) β,β′-fused into the aromatic system as well as porphyrinoids with organometallic fragments σ-bonded in η1-fashion were overviewed.

Long-range metal–metal coupling in transition-metal 5,10,15,20-tetraferrocenylporphyrins

Redox properties of several transition-metal MTFcP complexes (TFcP2− = 5,10,15,20-tetraferrocenylporphyrin, M = Co2+, Ni2+, Cu2+, and Zn2+) were investigated using electrochemical (CV and DPV), spectroelectrochemical, and chemical oxidation approaches. Electrochemical experiments conducted in a low-polarity solvent using a non-coordinating electrolyte are crucial for the sequential oxidation of ferrocene substituents along with porphyrin-based single-electron oxidation and reduction processes. The first ferrocene oxidation process in all MTFcP complexes is separated by at least 140 mV from the next three ferrocene based oxidations. The second, third, and fourth redox processes in the ferrocene region are more closely spaced, with the largest separation observed in CuTFcP and CoTFcP complexes. Mixed-valence compounds were observed and characterized by spectroelectrochemical and chemical oxidation approaches. In all cases, intervalence charge transfer (IVCT) bands were detected confirming the existence of the iron-based mixed-valence [MTFcP]n+ (n = 1–3) species and suggesting long-range metal–metal coupling in the target systems. The resulting data from the mixed-valence [MTFcP]n+ (n = 1–3) complexes matched very closely to the metal-free poly(ferrocenyl)porphyrins previously reported and were assigned as Robin and Day Class II mixed-valence compounds. In the case of CoTFcP, the selective oxidation of a central metal was also demonstrated in the presence of the strong ligand-field anions using oxygen as an oxidant.

Synthesis, Characterization, and Electron-Transfer Processes in Indium Ferrocenyl-Containing Porphyrins and Their Fullerene Adducts

Three new indium(III) tetra- and penta(ferrocenyl)-substituted porphyrins of the general formula XInTFcP [X = Cl(-), OH(-), or Fc(-); TFcP = 5,10,15,20-tetraferrocenylporphyrin(2-); Fc = ferrocene] have been prepared and characterized by UV-vis, magnetic circular dichroism (MCD), (1)H, (13)C, 2D, and variable-temperature NMR spectroscopy, as well as elemental analysis. Molecular structures of the ClInTFcP, FcInTFcP, and FcInTFcP@4C60 complexes were determined by X-ray crystallography with the last compound being not only the first example of a C60 adduct to the organometallic porphyrins but also the first structure in which organometallic porphyrin antennas intercalated into four electron-transfer channels. The electronic structures and relative energies of individual atropisomers, as well as prospective electron-transfer properties of fullerene adducts of XInTFcP complexes, were investigated by the Density Functional Theory (DFT) approach. Redox properties of XInTFcP complexes were investigated using electrochemical (CV and DPV), spectroelectrochemical, and chemical oxidation approaches. Electrochemical experiments conducted in low-polarity solvent using noncoordinating electrolyte were crucial for the sequential oxidation of ferrocene substituents in XInTFcP compounds. In agreement with DFT calculations, the axial ferrocene ligand in FcInTFcP, with direct In-C σ-bond has a 240 mV lower oxidation potential compared to the first oxidation potential for equatorial ferrocene substituents connected to the porphyrin core. The first equatorial ferrocene oxidation process in all XInTFcP complexes is separated by at least 150 mV from the next three ferrocene based oxidations. The second, third, and fourth redox processes in the ferrocene region are more closely spaced. The addition of the bulky axial ferrocene ligand results in significantly larger rotational barriers for equatorial ferrocene substituents in FcInTFcP compared to the other complexes and leads to better defined redox waves in cyclic voltammetry (CV) and differential pulse voltammetry (DPV) experiments. Mixed-valence compounds of the general formula [XInTFcP](n+) (n = 1, 2) were observed and characterized by spectroelectrochemical and chemical oxidation approaches. In all cases, the presence of the intense intervalence charge transfer (IVCT) bands associated with the oxidation of a single equatorial ferrocene substituent were detected in the NIR region confirming the presence of the iron-based mixed-valence species and suggesting long-range metal-metal coupling in the target systems. The resulting data from the mixed-valence [XInTFcP](n+) (n = 1, 2) complexes matched very closely to the previously reported MTFcP and metal-free poly(ferrocenyl)porphyrins and were assigned as Robin and Day Class II mixed-valence compounds.

Photoinduced charge transfer in short-distance ferrocenylsubphthalocyanine dyads.

Two new ferrocenylsubphthalocyanine dyads with ferrocenylmethoxide (2) and ferrocenecarboxylate (3) substituents directly attached to the subphthalocyanine ligand via the axial position have been prepared and characterized using NMR, UV-vis, and magnetic circular dichroism (MCD) spectroscopies as well as X-ray crystallography. The redox properties of the ferrocenyl-containing dyads 2 and 3 were investigated using the cyclic voltammetry (CV) approach and compared to those of the parent subphthalocyanine 1. CV data reveal that the first reversible oxidation is ferrocene-centered, while the second oxidation and the first reduction are localized on the subphthalocyanine ligand. The electronic structures and nature of the optical bands observed in the UV-vis and MCD spectra of all target compounds were investigated by a density functional theory polarized continuum model (DFT-PCM) and time-dependent (TD)DFT-PCM approaches. It has been found that in both dyads the highest occupied molecular orbital (HOMO) to HOMO-2 are ferrocene-centered molecular orbitals, while HOMO-3 as well as lowest unoccupied molecular orbital (LUMO) and LUMO+1 are localized on the subphthalocyanine ligand. TDDFT-PCM data on complexes 1-3 are consistent with the experimental observations, which indicate the dominance of π-π* transitions in the UV-vis spectra of 1-3. The excited-state dynamics of the dyads 2 and 3 were investigated using time-correlated single photon counting, which indicates that fluorescence quenching is more efficient in dyad 3 compared to dyad 2. These fluorescence lifetime measurements were interpreted on the basis of DFT-PCM calculations.

A Novel Hemiporphyrazine Comprising Three Isoindolediimine and Three Thiadiazole Units

Incorporation of three metal ions (Ni or Cu) in the macrocyclic ring and the formation of hexamers following a 3+3 approach are novel features of the hemiporphyrazines (one example shown) formed by the condensation of 2,5-diamino-1,3,4-triazole with isoindolediimines. This is in contrast to the corresponding reactions with diaminotriazoles, which afford 2+2 products.