Triply Linked Corrole Dimers

The oxidation of 10–10′ singly linked corrole dimers with DDQ at low concentration in CHCl₃ afforded meso–meso, β–β, β–β triply linked 2H‐corrole dimers (with two inner NH groups in each corrole unit), which exhibited characteristic ¹H NMR and absorption spectra attributable to their nonaromatic electronic networks. These 2H‐corrole dimers were reduced with NaBH₄ to aromatic 3H‐corrole dimers, which were unstable and easily oxidized back to the 2H‐corrole dimers upon exposure to air. Bis(zinc(II)) complexes of the 2H‐corrole dimers were synthesized and characterized as rare examples of nonaromatic zinc(II) corrole complexes.     

Fused Corrole Dimers Interconvert between Nonaromatic and Aromatic States through Two‐Electron Redox Reactions

A singly linked corrole dimer was synthesized by condensation of a dipyrromethane‐1‐carbinol with 1,1,2,2‐tetrapyrroethane. Oxidation of the dimer gave doubly linked corrole dimers 9 and 10 as the first examples of fused corrole dimers involving a meso–meso linkage. Dimers 9 and 10 exhibit characteristic ¹H NMR spectra, absorption spectra, excited‐state dynamics, and two‐photon absorption (TPA) values, which indicate the nonaromatic nature of 9 and the aromatic nature of 10 . Interestingly, 9 is fairly stable despite its unusual 2H‐corrole structure, which has been ascribed to the presence of two direct connections between the individual corrole units.     

meso‐Cumulenic 2H‐Corroles from meso‐Ethynyl‐3H‐corroles

Alkynyl‐substituted 3H‐corrole 9 a was converted to [3]cumulenic 2H‐corrole 10 a by treatment with trimethylsilyl chloride (TMSCl), and 1,3‐butadiyne‐bridged 3H‐corrole dimer 11 b was transformed into [5]cumulene‐bridged 2H‐corrole dimer 12 b by oxidation with PbO₂. Both 10 a and 12 b were metalated to form Zn^II complexes 10 a‐Zn and 12 b‐Zn . The structures of 10 a‐Zn and 12 b‐Zn show planar conformations with bond‐length alternations that are analogous to those of tetraaryl [n]cumulenes. The cumulenic corrole dimers 12 b and 12 b‐Zn display large NIR absorption bands in the range of 700–1400 nm (maximum ϵ≈1.0×10⁵ m ⁻¹ cm⁻¹) owing to the effective π‐conjugation between the two corrole units through the [5]cumulene bridge.     

[CuCl3(H2O)]− complexes aggregated to form hydrate columns in methyl‐substituted pyridinium or piperidinium salts

1,2,3‐Trimethylpyridinium aquatrichloridocuprate(II), (C₈H₁₂N)[CuCl₃(H₂O)], (I), 3,4‐dimethylpyridinium aquatrichloridocuprate(II), (C₇H₁₀N)[CuCl₃(H₂O)], (II), and 2,3‐dimethylpyridinium aquatrichloridocuprate(II), (C₇H₁₀N)[CuCl₃(H₂O)], (III), exhibit the same fundamental structure, with (I) and (II) isomorphous and with the unit‐cell constants of (III) similar to the reduced unit‐cell constants of (I) and (II). The distorted square‐planar [CuCl₃(H₂O)]⁻ complex [mirror symmetric in (I) and (II)] forms two semicoordinate Cu...Cl bonds to a neighboring complex to produce a dimer with 2/m symmetry [only inversion symmetry in (III)]. The semicoordinate Cu...Cl bond length of the dimer shows significant elongation at 295 K compared with that at 100 K, while the coordinate Cu—Cl bond lengths are slightly contracted at 295 K compared with those at 100 K. The inorganic dimers are linked by eight hydrogen bonds to four neighboring dimers to establish a checkerboard network layer in the ab plane, with voids between the dimers that accommodate, on both sides, inversion‐related organic cation pairs. The organic cations are required by mirror‐plane symmetry to be disordered in (I) and (II). The organic cations and [CuCl₃(H₂O)]⁻ complexes are nearly coplanar and tilted out of the layer plane to establish a hybrid organic–inorganic layer structure parallel to (202) [(11) in (III)], with hydrate columns (defined by water molecules) and hydrophobic columns (defined by methyl groups) parallel to each other [and along the 2₁ axes in (I) and (II)]. In 1,1‐dimethylpiperidinium aquatrichloridocuprate(II), (C₇H₁₆N)[CuCl₃(H₂O)], (IV), the bulkier organic cation prevents semicoordinate bonding between complexes, which are hydrogen bonded side‐to‐side in zigzag chains that place water molecules in columns along half of the 2₁ axes.     

The Corrole Radical

The reaction of 5,10,15‐trimesitylcorrole (H₃cor) with tungsten hexachloride and tungsten hexacarbonyl resulted in the unexpected formation of the 3,17‐dichloro‐5,10,15‐trimesitylcorrole radical (H₂cor*) as an air‐stable product. X‐ray crystallography proved the planarization of the corrole radical structure, which was rationalized by the reduced steric hindrance of two versus three hydrogen atoms inside the N₄ cavity. Although the aromaticity was lost, no specific changes in C C or C N bond distances could be observed. The regioselectivity of the two‐fold chlorination is the result of the nucleophilic attack of chloride ions to an oxidized corrole macrocycle, and is supported by DFT results. The corrole radical acts as a dianionic ligand and allows the insertion of the divalent zinc(II) cation, which usually does not form neutral corrole complexes.     

The Corrole Radical

The reaction of 5,10,15‐trimesitylcorrole (H₃cor) with tungsten hexachloride and tungsten hexacarbonyl resulted in the unexpected formation of the 3,17‐dichloro‐5,10,15‐trimesitylcorrole radical (H₂cor*) as an air‐stable product. X‐ray crystallography proved the planarization of the corrole radical structure, which was rationalized by the reduced steric hindrance of two versus three hydrogen atoms inside the N₄ cavity. Although the aromaticity was lost, no specific changes in C? C or C? N bond distances could be observed. The regioselectivity of the two‐fold chlorination is the result of the nucleophilic attack of chloride ions to an oxidized corrole macrocycle, and is supported by DFT results. The corrole radical acts as a dianionic ligand and allows the insertion of the divalent zinc(II) cation, which usually does not form neutral corrole complexes.     

Desymmetrization of meso diols using enantiopure zinc (II) dimers: Synthesis and chiroptical properties

The one‐pot metal templated synthesis of enantiopure binuclear Zn (II) complexes Zn₂L¹–Zn₂L⁴ were obtained by treating (1R,2R)‐diphenylethylenediamine or (1S,2S)‐diphenylethylenediamine with 2‐hydroxy‐5‐methyl‐1,3‐benzenedicarboxaldehyde or 4‐tert‐butyl‐2,6‐diformylphenol and zinc acetate. The chiroptical properties of the complexes were studied by using circular dichroism spectroscopy. These ΔΔ and ΛΛ complexes were used as enantioselective catalysts for desymmetrization of meso diol to achieve monobenzoylated product with 96% yield and 88% ee.     

Structural and spectroscopic characterization of two new blue luminescent pyridylbenzimidazole zinc(II) complexes

Luminescent metal complexes are used in photooptical devices. Zinc(II) complexes are of interest because of the ability to tune their color, their high thermal stability and their favorable carrier transport character. In particular, some zinc(II) complexes with aryl diimine and/or heterocyclic ligands have been shown to emit brightly in the blue region of the spectrum. Zinc(II) complexes bearing derivatized imidazoles have been explored for possible optoelectronic applications. The structures of two zinc(II) complexes of 5,6‐dimethyl‐2‐(pyridin‐2‐yl)‐1‐[(pyridin‐2‐yl)methyl]‐1H‐benzimidazole (L), namely dichlorido(dimethylformamide‐κO){5,6‐dimethyl‐2‐(pyridin‐2‐yl‐κN)‐1‐[(pyridin‐2‐yl)methyl]‐1H‐benzimidazole‐κN³}zinc(II) dimethylformamide monosolvate, [ZnCl₂(C₂₀H₁₈N₄)(C₃H₇NO)]·C₃H₇NO, (I), and bis(acetato‐κ²O,O′){5,6‐dimethyl‐2‐(pyridin‐2‐yl‐κN)‐1‐[(pyridin‐2‐yl)methyl]‐1H‐benzimidazole‐κN³}zinc(II) ethanol monosolvate, [Zn(C₂H₃O₂)₂(C₂₀H₁₈N₄)]·C₂H₅OH, (II), are reported. Complex (I) crystallized as a dimethylformamide solvate and exhibits a distorted trigonal bipyramidal coordination geometry. The coordination sphere consists of a bidentate L ligand spanning axial to equatorial sites, two chloride ligands in equatorial sites, and an O‐bound dimethylformamide ligand in the remaining axial site. The other complex, (II), crystallized as an ethanol solvate. The Zn^II atom has a distorted trigonal prismatic coordination geometry, with two bidentate acetate ligands occupying two edges and a bidentate L ligand occupying the third edge of the prism. Complexes (I) and (II) emit in the blue region of the spectrum. The results of density functional theory (DFT) calculations suggest that the luminescence of L results from π*←π transitions and that the luminescence of the complexes results from interligand charge‐transfer transitions. The orientation of the 2‐(pyridin‐2‐yl) substituent with respect to the benzimidazole system was found to have an impact on the calculated HOMO–LUMO gap (HOMO is highest occupied molecular orbital and LUMO is lowest unoccupied molecular orbital).     

Adducts of bis(acetylacetonato)zinc(II) with 1,10‐phenanthroline and 2,2′‐bipyridine

In each of the zinc(II) complexes bis(acetylacetonato‐κ²O,O′)(1,10‐phenanthroline‐κ²N,N′)zinc(II), [Zn(C₅H₇O₂)₂(C₁₂H₈N₂)], (I), and bis(acetylacetonato‐κ²O,O′)(2,2′‐bipyridine‐κ²N,N′)zinc(II), [Zn(C₅H₇O₂)₂(C₁₀H₈N₂)], (II), the metal center has a distorted octahedral coordination geometry. Compound (I) has crystallographically imposed twofold symmetry, with Z′ = 0.5. The presence of a rigid phenanthroline group precludes intramolecular hydrogen bonding, whereas the rather flexible bipyridyl ligand is twisted to form an intramolecular C—H...O interaction [the chelated bipyridyl ligand is nonplanar, with the pyridyl rings inclined at an angle of 13.4 (1)°]. The two metal complexes are linked by dissimilar C—H...O interactions into one‐dimensional chains. The present study demonstrates the distinct effects of two commonly used ligands, viz. 1,10‐phenanthroline and 2,2′‐bipyridine, on the structures of metal complexes and their assembly.     

Three zinc iodide complexes based on phosphane ligands: syntheses,structures, optical properties and TD–DFT calculations

Three zinc iodide complexes based on phosphane ligands, namely diiodidobis(triphenylphosphane‐κP)zinc(II), [ZnI₂(C₁₈H₁₅P₂)₂], ( 1 ), diiodidobis[tris(4‐methylphenyl)phosphane‐κP]zinc(II), [ZnI₂(C₂₁H₂₁P₂)₂], ( 2 ), and [bis(diphenylphosphoryl)methane‐κ²O,O′]zinc(II) tetraiodidozinc(II), [Zn(C₂₅H₂₂O₂P₂)₃][ZnI₄], ( 3 ), have been synthesized and characterized. Single‐crystal X‐ray diffraction revealed that the structures of ( 1 ) and ( 2 ) are both mononuclear four‐coordinated ZnI₂ complexes containing two monodentate phosphane ligands, respectively. Surprisingly, ( 2 ) spontaneously forms an acentric structure, suggesting it might be a potential second‐order NLO material. The crystal structure of complex ( 3 ) is composed of two parts, namely a [Zn(dppmO₂)₃]²⁺ cation [dppmO₂ is bis(diphenylphosphoryl)methane] and a [ZnI₄]²⁻ anion. The UV–Vis absorption spectra, thermal stabilities and photoluminescence spectra of the title complexes have also been studied. Time‐dependent density functional theory (TD–DFT) calculations reveal that the low‐energy UV absorption and the corresponding light emission both result from halide‐ligand charge‐transfer (XLCT) excited states.     

Two isomorphous ZnII/CoII complexes with tri‐tert‐butoxysilanethiol and histamine,and (4‐hydroxymethyl‐1H‐imidazole‐κN)bis(tri‐tert‐butoxysilanethiolato‐κ2O,S)zinc(II)

The complexes [2‐(1H‐imidazol‐4‐yl‐κN³)ethylamine‐κN]bis(tri‐tert‐butoxysilanethiolato‐κS)cobalt(II), [Co(C₁₂H₂₇O₃SSi)₂(C₅H₉N₃)], and [2‐(1H‐imidazol‐4‐yl‐κN³)ethylamine‐κN]bis(tri‐tert‐butoxysilanethiolato‐κS)zinc(II), [Zn(C₁₂H₂₇O₃SSi)₂(C₅H₉N₃)], are isomorphous. The central Zn^II/Co^II ions are surrounded by two S atoms from the tri‐tert‐butoxysilanethiolate ligand and by two N atoms from the chelating histamine ligand in a distorted tetrahedral geometry, with two intramolecular N—H...O hydrogen‐bonding interactions between the histamine NH₂ groups and tert‐butoxy O atoms. Molecules of the complexes are joined into dimers via two intermolecular bifurcated N—H...(S,O) hydrogen bonds. The Zn^II atom in [(1H‐imidazol‐4‐yl‐κN³)methanol]bis(tri‐tert‐butoxysilanethiolato‐κ²O,S)zinc(II), [Zn(C₁₂H₂₇O₃SSi)₂(C₄H₆N₂O)], is five‐coordinated by two O and two S atoms from the O,S‐chelating silanethiolate ligand and by one N atom from (1H‐imidazol‐4‐yl)methanol; the hydroxy group forms an intramolecular hydrogen bond with sulfur. Molecules of this complex pack as zigzag chains linked by N—H...O hydrogen bonds. These structures provide reference details for cysteine‐ and histidine‐ligated metal centers in proteins.     

Bis‐copper(II) Complex of Triply‐linked Corrole Dimer and Its Dication

Copper complexes of corroles have recently been a subject of keen interest due to their ligand non‐innocent character and unique redox properties. Here we investigated bis‐copper complex of a triply‐linked corrole dimer that serves as a pair of divalent metal ligands but can be reduced to a pair of trivalent metal ligands. Reaction of triply‐linked corrole dimer 2 with Cu(acac)₂ (acac=acetylacetonate) gave bis‐copper(II) complex 2Cu as a highly planar molecule with a mean‐plane deviation value of 0.020 Å, where the two copper ions were revealed to be divalent by ESR, SQUID, and XPS methods. Oxidation of 2Cu with two equivalents of AgBF₄ gave complex 3Cu , which was characterized as a bis‐copper(II) complex of a dicationic triply‐linked corrole dimer not as the corresponding bis‐copper(III) complex. In accord with this assignment, the structural parameters around the copper ions were revealed to be quite similar for 2Cu and 3Cu . Importantly, the magnetic spin–spin interaction differs depending on the redox‐state of the ligand, being weak ferromagnetic in 2Cu and antiferromagnetic in 3Cu .     

Two ZnII coordination complexes assembled by trithiocyanuric acid and two different N‐donor auxiliary ligands

The dipyridyl‐type building blocks 4‐amino‐3,5‐bis(pyridin‐3‐yl)‐1,2,4‐triazole (3‐bpt) and 4,4′‐bipyridine (bpy) have been used to assemble with Zn^II in the presence of trithiocyanuric acid (ttcH₃) to afford two coordination compounds, namely bis[4‐amino‐3,5‐bis(pyridin‐3‐yl)‐1,2,4‐triazole‐κN³]bis(trithiocyanurato‐κ²N,S)zinc(II), [Zn(C₃H₂N₃S₃)₂(C₁₂H₁₀N₆)₂]·2H₂O, (1), and catena‐poly[[[bis(trithiocyanurato‐κ²N,S)zinc(II)]‐μ‐4,4′‐bipyridine‐κ²N:N′] 4,4′‐bipyridine monosolvate], {[Zn₂(C₃H₂N₃S₃)₄(C₁₀H₈N₂)₃]·C₁₀H₈N₂}_n, (2). Single‐crystal X‐ray analysis indicates that complex (1) is a mononuclear structure, while complex (2) presents a one‐dimensional chain coordination motif. In both complexes, the central Zn^II cation adopts an octahedral geometry, coordinated by four N‐ and two S‐donor atoms. Notably, trithiocyanurate (ttcH₂⁻) adopts the same bidentate chelating coordination mode in each complex and exists in the thione tautomeric form. The 3‐bpt co‐ligand in (1) adopts a monodentate coordination mode and serves as a terminal pendant ligand, whereas the 4,4′‐bipyridine (bpy) ligand in (2) adopts a bidentate–bridging coordination mode. The different coordination characters of the different N‐donor auxiliary ligands lead to structural diversity for complexes (1) and (2). Further analysis indicates that the resultant three‐dimensional supramolecular networks for (1) and (2) arise through intermolecular N—H...S and N—H...N hydrogen bonds. Both complexes have been further characterized by FT–IR spectroscopy and elemental analyses.     

Granisetron,an antiemetic drug,and its cobalt complex

The crystal structures of granisetron [systematic name: 1‐methyl‐N‐(9‐methyl‐9‐azabicyclo[3.3.1]nonan‐7‐yl)indazole‐3‐carboxamide], C₁₈H₂₄N₄O, (I), an antinauseant and antiemetic agent, and its Co^II complex, diaqua[1‐methyl‐N‐(9‐methyl‐9‐azoniabicyclo[3.3.1]nonan‐7‐yl)indazole‐3‐carboxamide]cobalt(II) tetrachloride dodecahydrate, [Co(C₁₈H₂₅N₄O)₂(H₂O)₂]Cl₄·12H₂O, (II), have been determined by X‐ray diffraction. The granisetron molecule is in an extended conformation in both structures. Twisting of the central carboxamide group facilitates the Co^II coordination in (II). The Co^II atom is located on an inversion centre. The azabicyclononane ring adopts a chair–boat conformation in both structures. The molecules in (I) are linked into centrosymmetric dimers and form tetracyclic rings through C—H...O hydrogen‐bonding interactions. The simultaneous presence of free chloride ions in conjunction with a number of hydration water molecules in (II) provides interesting hydrogen‐bond patterns. This study can aid in the investigation of the properties of metal complexes with active pharmaceuticals in which the drug molecules play the role of a ligand.     

Tris(1,10‐phenanthroline‐κ2N,N′)iron(II) bis(2,4,5‐tricarboxybenzoate) monohydrate and tris(2,2′‐bipyridine‐κ2N,N′)iron(II) 2,5‐dicarboxybenzene‐1,4‐dicarboxylate–benzene‐1,2,4,5‐tetracarboxylic acid–water (1/1/2)

The title compounds, tris(1,10‐phenanthroline‐κ²N,N′)iron(II) bis(2,4,5‐tricarboxybenzoate) monohydrate, [Fe(C₁₂H₈N₂)₃](C₁₀H₅O₈)₂·H₂O, (I), and tris(2,2′‐bipyridine‐κ²N,N′)iron(II) 2,5‐dicarboxybenzene‐1,4‐dicarboxylate–benzene‐1,2,4,5‐tetracarboxylic acid–water (1/1/2), [Fe(C₁₀H₈N₂)₃](C₁₀H₄O₈)·C₁₀H₆O₈·2H₂O, (II), were obtained during an attempt to synthesize a mixed‐ligand complex of Fe^II with an N‐containing ligand and benzene‐1,2,4,5‐tetracarboxylic acid via a solvothermal reaction. In both mononuclear complexes, each Fe^II metal ion is six‐coordinated in a distorted octahedral manner by six N atoms from three chelating 1,10‐phenanthroline or 2,2′‐bipyridine ligands. In compound (I), the Fe^II atom lies on a twofold axis in the space group C2/c, whereas (II) crystallizes in the space group P2₁/n. In both compounds, the uncoordinated carboxylate anions and water molecules are linked by typical O—H...O hydrogen bonds, generating extensive three‐dimensional hydrogen‐bond networks which surround the cations.     

Nickel and zinc complexes with a monodentate heterocycle and tridentate Schiff base ligands: self‐assembly to one‐ and two‐dimensional supramolecular networks via hydrogen bonding

In the complex (morpholine)[2‐hydroxy‐N′‐(5‐nitro‐2‐oxidobenzylidene)benzohydrazidato]nickel(II), [Ni(C₁₄H₉N₃O₅)(C₄H₉NO)], (I), the Ni^II center is in a square‐planar N₂O₂ coordination geometry. The complex bis[μ‐2‐hydroxy‐N′‐(2‐oxidobenzylidene)benzohydrazidato]bis[(morpholine)zinc(II)], [Zn₂(C₁₄H₁₀N₂O₃)₂(C₄H₉NO)₂], (II), consists of a neutral centrosymmetric dimer with a coplanar Zn₂(μ₂‐O)₂ core. The two Zn^II centers are bridged by phenolate O atoms. Each Zn^II center exhibits a distorted square‐pyramidal stereochemistry, in which the four in‐plane donors come from the O,N,O′‐tridentate 2‐hydroxy‐N′‐(2‐oxidobenzylidene)benzohydrazidate(2−) ligand and a symmetry‐related phenolate O atom, and the axial position is coordinated to the N atom from the morpholine molecule. There are intramolecular phenol–hydrazide O—H...N hydrogen bonds present in both (I) and (II). In (I), square‐planar nickel complexes are linked by intermolecular morpholine–morpholine N—H...O hydrogen bonds, leading to a one‐dimensional chain, while in (II) an infinite two‐dimensional network is formed via intermolecular hydrogen bonds between the coordinated morpholine NH groups and the uncoordinated phenolate O atoms.     

Pd(II) complexes of Schiff bases and their application as catalysts in Mizoroki–Heck and Suzuki–Miyaura cross‐coupling reactions

Schiff bases of 2‐(phenylthio)aniline, (C₆H₅)SC₆H₄N?CR (R = (o‐CH₃)(C₆H₅), (o‐OCH₃)(C₆H₅) or (o‐CF₃)(C₆H₅)), and their palladium complexes (PdLCl₂) were synthesized. The compounds were characterized using ¹H NMR and ¹³C NMR spectroscopy and micro analysis. Also, electrochemical properties of the ligands and Pd(II) complexes were investigated in dimethylformamide–LiClO₄ solution with cyclic and square wave voltammetry techniques. The Pd(II) complexes showed both reversible and quasi‐reversible processes in the ?1.5 to 0.3 V potential range. The synthesized Pd(II) complexes were evaluated as catalysts in Mizoroki–Heck and Suzuki–Miyaura cross‐coupling reactions. Copyright © 2015 John Wiley & Sons, Ltd.     

Different patterns of supramolecular assembly in constitutionally similar 6‐arylimidazo[2,1‐b][1,3,4]thiadiazoles

Four imidazo[2,1‐b][1,3,4]thiadiazoles containing a simply‐substituted 6‐aryl group have been synthesized by reaction of 2‐amino‐1,3,4‐thiadiazoles with bromoacetylarenes using microwave irradiation and brief reaction times. 6‐(2‐Chlorophenyl)imidazo[2,1‐b][1,3,4]thiadiazole, C₁₀H₆ClN₃S, (I), 6‐(2‐chlorophenyl)‐2‐methylimidazo[2,1‐b][1,3,4]thiadiazole, C₁₁H₈ClN₃S, (II), 6‐(3,4‐dichlorophenyl)imidazo[2,1‐b][1,3,4]thiadiazole, C₁₀H₅Cl₂N₃S, (III), and 6‐(4‐fluoro‐3‐methoxyphenyl)‐2‐methylimidazo[2,1‐b][1,3,4]thiadiazole, C₁₂H₁₀FN₃OS, (IV), crystallize with Z′ values of 2, 1, 1 and 2 respectively. The molecular skeletons are all nearly planar and the dihedral angles between the imidazole and aryl rings are 1.51 (8) and 7.28 (8)° in (I), 9.65 (7)° in (II), 10.44 (8)° in (III), and 1.05 (8) and 7.21 (8)° in (IV). The molecules in (I) are linked by three independent C—H...N hydrogen bonds to form ribbons containing alternating R₂²(8) and R₄⁴(18) rings, and these ribbons are linked into a three‐dimensional array by three independent π‐stacking interactions. Both (II) and (III) contain centrosymmetric dimers formed by π‐stacking interactions but hydrogen bonds are absent, and the molecules of (IV) are linked into centrosymmetric R₂²(8) dimers by C—H...N hydrogen bonds. Comparisons are made with a number of related compounds.     

An Electron‐Deficient Porphyrin Tape

Hexakis(pentafluorophenyl)‐substituted meso–meso‐linked Zn^II–diporphyrin ( 9 ), which was prepared by the acid‐catalyzed cross‐condensation of 1,1,2,2‐tetrapyrroethane ( 5 ) with dipyrromethane dicarbinol ( 6 ), was converted into meso–meso,β‐β,β‐β triply linked Zn^II–diporphyrin 3 by oxidation with 2,3‐dichloro‐5,6‐dicyanobenzoquinone (DDQ) and Sc(OTf)₃. Beside the red‐shifted absorption spectrum and split first oxidation potential that are common to the triply‐linked Zn^II–diporphyrins, diporphyrin 3 exhibited considerably improved chemical stability owing to a lowered HOMO and good solubility in common organic solvents. The two‐photon absorption (TPA) cross‐section and S₁‐state lifetime of compound 3 were 1700 GM and 3.3 ps, respectively.     

DNA binding and nuclease activity of cationic iron(IV) and manganese(III) corrole complexes

Cationic meso(4‐N‐methylpyridyl)‐based metallocorroles, μ‐oxo iron corrole dimer ( 1b ) and manganese corrole monomer ( 2b ), were synthesized and characterized. The interactions of these two metal corrole complexes with CT‐DNA were studied by UV–visible, fluorescence and circular dichroism spectroscopic methods, as well as by viscosity measurements. The results revealed that 1b interacts with CT‐DNA in a difunctional binding mode, i.e. non‐classical intercalation and outside groove binding with H‐aggregation, while 2b can interact with CT‐DNA via an outside groove binding mode only. The binding constants K_b of 1b and 2b were 4.71 × 10⁵ m ^?1 and 2.17 × 10⁵ m ^?1, respectively, indicating that 1b can bind more tightly to CT‐DNA than 2b . Furthermore, both complexes may cleave the supercoiled plasmid DNA efficiently in the presence of hydrogen peroxide or tert‐butyl hydroperoxide (TBHP), albeit 1b exhibited a little higher efficiency. The inhibitor tests suggested that singlet oxygen and high‐valent (oxo)iron(VI) corrole or (oxo)manganese(V) corrole might be the active intermediates responsible for the oxidative DNA scission. Copyright © 2014 John Wiley & Sons, Ltd.