Carbocations Confined in a Thiatriazuliporphyrin Frame.

In the search for tricarbaporphyrinoids, a three-component acid-catalyzed condensation of azulene, 2,5-bis[(p-tolyl)hydroxymethyl]thiophene, and an aryl aldehyde has been elaborated, affording the appropriate thiatriazuliporphyrinogens. The subsequent oxidation yielded a rare example of a macrocyclic organic tetracation, which can be readily and reversibly converted into macrocyclic tri- and dicarbocations by addition of one or two hydroxides bound at the meso position(s). Further insight into the influence of carbocation formation on the geometry, electronic structure, and magnetic manifestation in (1) H NMR spectroscopy has been obtained by using density functional theory calculations.

A Rhodium-Mediated Contraction of Benzene to Cyclopentadiene: Transformations of Rhodium(III) m-Benziporphyrin.

The contraction of benzene is one of an exclusive group of reactions where the cleavage of aromatic structure is of fundamental importance. Rhodium(III) m-benziporphyrin undergoes an unprecedented transformation of the built-in m-phenylene in which a perimeter carbon atom is extruded to form rhodium(III) 21-carbaporphyrin, stabilizing the formyl-unit-substituted rhodacyclopropane motif.

From para-Benziporphyrin to Rhodium(III) 21-Carbaporphyrins: Imprinting Rh⋅⋅⋅η(2)-CC, Rh⋅⋅⋅η(2)-CO, and Rh⋅⋅⋅η(2)-CH Coordination Motifs.

Rhodium(III) para-benziporphyrin alters the fundamental reactivity of the built-in para-phenylene moiety. Due to additional macrocyclic stabilization, a sequence of intramolecular rearrangements are triggered to afford rhodium(III) 21-carbaporphyrin, which incorporates the rhodacyclopropane motif. The peculiar reversible transformations of the bridging methylene unit provide an example of selective and reversible aliphatic C-H bond elimination.

A fused meso-aminoporphyrin: a switchable near-IR chromophore.

An aryl amine attached to the meso position of a porphyrin controls the π-delocalization using a redox process or a protonation/deprotonation centered at the meso-nitrogen. An easily accessible modulated motif affords a switchable near-IR chromophore as reflected by significant changes in absorption and fluorescence spectra.

Phenanthriporphyrin: an antiaromatic aceneporphyrinoid as a ligand for a hypervalent organophosphorus(V) moiety.

The incorporation of a phenanthrene moiety into a porphyrin framework results in the formation of a hybrid macrocycle—phenanthriporphyrin—merging the structural features of polycyclic aromatic hydrocarbons and porphyrins. An antiaromatic aceneporphyrinoid, adopting the trianionic {CCNN} core, is suitable for the incorporation of a phosphorus(V) center to form a hypervalent organophosphorus(V) derivative.

Oxatriphyrins(2.1.1) incorporating an ortho-phenylene motif.

An understanding of fundamental aspects of archetypal organic structural motifs remains a key issue faced by the experimental and theoretical chemists. Two possible bonding modes for a disubstituted benzene ring, that is a meta and para, determines the π delocalization for oligomeric structures. When the less abundant ortho-substituted variant is introduced into a triphyrin(2.

Synthesis and switching the aromatic character of oxatriphyrins(2.1.1).

Triangularly shaped, contracted porphyrinoids belong to a group of molecules where the geometry significantly modifies the observed electronic properties. The need for a controllable, effective, and widely applicable approach to triphyrins drives extensive research towards macrocyclic materials that act as potential controlling motifs by switching their aromaticity. Two isomeric thiophene-fused triphyrins(2.

Towards true carbaporphyrinoids: synthesis of 21-carba-23-thiaporphyrin.

In the search for porphyrinoids with a built-in cyclopentadienyl moiety (true carbaporphyrins), a rational synthesis of carbathiaporphyrin, the synthons, has been elaborated. The donors (C,N,S,N) in the porphyrinic core of carbathiaporphyrinoids are potentially of fundamental importance for generating organometallic complexes, as exemplified through formation of the palladium(II) complex.

Gold(III)-mediated contraction of benzene to cyclopentadiene: from p-benziporphyrin to gold(III) true tetraarylcarbaporphyrin.

The reaction of p-benziporphyrin, sodium tetrachloroaurate(III) dihydrate, and potassium carbonate in dichloromethane yielded gold(III) 5,10,15,20-tetraaryl-21-carbaporphyrin owing to the contraction of p-phenylene to cyclopentadiene. This molecule is the very first representative of a true 5,10,15,20-tetraaryl-21-carbaporphyrin complex where four trigonal donor atoms are involved in equatorial coordination. The contraction adds an unprecedented route to numerous organic transformations of aromatic compounds catalyzed by simple gold(III) compounds.

Copper(II) thiaethyneporphyrin and copper(II) 21-phosphoryl N-confused porphyrin hybrids. intramolecular copper(II)-carbon interaction inside of a porphyrinoid surrounding.

Stabilization of unusual organocopper(II) species via the very efficient protection of the copper(II)-carbon bond has been achieved encapsulating the copper(II) center in the coordination core of suitably constructed carbaporphyrinoids. Copper(II) was inserted into hybrid N-confused porphyrins which contain 21-diphenylphosphoryl-, 21-diphenylthiophosphoryl-, or 21-phosphinodithioic substituents or into 20-thiaethyneporphyrin, an aromatic porphyrinoid, which combines two structural motifs of 21-thiaporphyrin and ethyne. Two distinctly different types of the copper(II)-carbon bond have been detected.

Regioselective phosphorylation and thiophosphorylation of N-confused porphyrin: a route to hybrid carbaporphyrinoids.

N-confused porphyrin (NCP) undergoes controlled regioselective phosphorylations at the inner, outer or both carbon atoms of the inverted pyrrole ring. Reactivity centered at the internal carbon atom is enhanced in the Ag(III) NCP's whereas the preference for perimeter substitution is characteristic of free base NCP. The addition of S(8) resulted in the formation of thio-derivatives containing 21-diphenylthiophosphoryl or 21-phosphinodithioic substituents.

Toward aceneporphyrinoids: synthesis and transformations of palladium(II) meso-anthriporphyrin.

meso-Anthriporphyrin is a carbaporphyrinoid with an anthracene ring embedded in the tripyrrolic framework. The coordination of palladium(II) results in a specific intramacrocyclic metal(II)-η(2)-CC interaction which facilitates the cleavage to palladium(II) acyclic oligopyrrole with the appended anthracene moiety.

Core-modified hexaphyrin: synthesis and characterization of 31,34-disilahexaphyrinoid.

Condensation of 16-silatripyrrane with pentafluorobenzaldehyde under catalytic conditions followed by DDQ oxidation leads to 31,34-disilahexaphyrinoid--a four times reduced derivative of 31,34-disilahexaphyrin which contains two built-in silole units flanked by four tetrahedrally hybridized meso carbons. In the preferred folded macrocyclic conformation the silole rings remain perpendicular to each other. The steric hindrance of bulky substituents at silicon atoms and β-positions of siloles prevented aromatization.

Nickel(II) and palladium(II) thiaethyneporphyrins. Intramolecular metal(II)-η2-CC interaction inside a porphyrinoid frame.

3,18-Diphenyl-8,13-di-p-tolyl-20-thiaethyneporphyrin ([18]thiatriphyrin(4.1.1)), which formally contains an C1-C2 ethyne moiety instead of pyrrole embedded in the macrocyclic framework of 21-thiaporphyrin, was obtained in a modification of the "3 + 1" approach using the ethyne analogue of tripyrrane (1,4-diphenyl-1,4-di(pyrrol-2-yl)but-2-yne) and 2,5-bis(p-tolylhydroxymethyl)thiophene.

Common origin, common fate: regular porphyrin and N-confused porphyrin yield an identical tetrapyrrolic degradation product.

The formation of an identical linear tetrapyrrole observed in the course of photooxidation of meso-tetraarylporphyrin and its N-confused isomer can be explained as a result of 1,2- and 1,3-dioxygen addition, respectively, as substantiated by DFT calculations.

Protonated N-confused porphyrin dimer: formation, structure, and guest binding.

The protonation of 3,3'-bis(meso-tetratolyl-2-aza-21-carbaporphyrin) with various acids was studied. The stepwise formation of mono-, di-, and tetracationic species was shown on the basis of UV-vis-near-IR and low-temperature (1)H NMR. Upon going from di- to tetraprotonated form, the bis(porphyrinoid) skeleton changes its conformation from cisoid to bent-transoid, which was found by single-crystal X-ray analyses, 2D NMR, and density functional theory (DFT) calculations.

A flexible porphyrin-annulene hybrid: a nonporphyrin conformation for meso-tetraaryldivacataporphyrin.

An annulene-porphyrin hybrid, the diaaza-deficient porphyrin 5,10,15,20-tetraaryl-21,23-divacataporphyrin, has been synthesized by an extrusion of tellurium atom(s) from 5,10,15,20-tetraaryl-21,23-ditelluraporphyrin under treatment with HCl. In addition, a monoaza-deficient 5,10,15,20-tetraaryl-21-tellura-23-vacataporphyrin was formed in the same reaction. The two new members of the vacataporphyrin family were characterized by X-ray crystallography, as well as UV/Vis and NMR spectroscopy.

Enantiomer resolution of intrinsically chiral C21-alkylated N-confused porphyrin complexes.

The resolution of stereoisomers of C21-alkylated nickel(II) complexes of N-confused porphyrin (NCP) was performed by means of chiral-phase HPLC with an effectiveness of above 90 % molar ratio for each isomer. The reverse signs of the Cotton effects in the circular dichroism (CD) spectra of the separated fractions are indicative of the pair of enantiomers. The application of low-temperature 2D NMR methods to the separated diastereomers of the system comprising a chiral 2-(S)-methylbutyl substituent, in connection with the CD spectra and relative HPLC migration rates, allowed the assignment of the absolute configuration of the chiral C21-substituted complexes of NCP.

Transformations of N-confused porphyrin triggered by insertion of silicon(IV).

N-confused porphyrin, 5,10,15,20-tetraaryl-2-aza-21-carbaporphyrin, dissolved in triethylamine reacts with dichloromethylsilane yielding the methylsilicon(IV) complex of 5,10,15,20-tetraaryl-2-aza-21-hydroxy-21-carbaporphyrin. Addition of aldehydes or ketones (acetone, acetaldehyde acetophenone, butanone, propanal, benzaldehyde, p-methylbenzaldehyde, p-methoxybenzaldehyde, terephthaldehyde) into the insertion mixture triggered the profound transformation of N-confused porphyrin to form the methylsilicon(IV) complex of N-fused porphyrin derivative substituted at the inner C(9) position by a hydroxyalkyl moiety derived from aldehyde or ketone. The macrocyle is structurally related to an aromatic N-fused inner phlorin while the coordination polyhedron of bound silicon resembles the trigonal bipyramid.

Organocopper(II) complex of 21-diphenylphosphoryl-carbaporpholactone hybrid: a side-on coordination mode of copper(II).

The diphenylphosphoryl-carbaporpholactone hybrid is a new aromatic porphyrinoid, which preserves the essential features of the carbaporpholactone frame and provides a suitable environment allowing stabilization of the organocopper(II) complex affording a peculiar side-on coordination of copper(II).

Tetraazuliporphyrin tetracation.

At the crossroads: A unique carbon-bridged annulene motif--dehydroquatyrin--is imprinted into the molecular structure of the tetraazuliporphyrin tetracation (see picture). The macrocycle, which lies at the intersection of annulene, carbocation, and porphyrin chemistry, is obtained by the standard condensation of azulene and arylaldehyde followed by oxidation. The meso positions of the tetracation are susceptible to anionic or weak nucleophilic attack.

Phosphorus complexes of N-fused porphyrin and its reduced derivatives: new isomers of porphyrin stabilized via coordination.

N-fused isophlorin 3 and its tautomeric phlorin forms 4 and 5, the new constitutional isomers of porphyrin which preserve the basic skeleton of their maternal N-fused porphyrin, have been identified in the course of investigation of phosphorus insertion into N-fused porphyrin 2. N-fused porphyrin reacts with PCl3 in toluene yielding phosphorus(V) N-fused isophlorin 3-P wherein the macrocycle acts as a trianionic tridentate ligand. The identical product has been formed in the reaction of N-confused porphyrin 1 and POCl3 or PCl3.