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The coordination chemistry of corrole has witnessed a great improvement in the past few years and its Periodic Table has been widened to be so large that it is compared with that of porphyrins. However, Ni and Zn ions, commonly used with porphyrins for both synthetic and theoretical purposes, are sparsely reported in the case of corroles. Here, we report synthetic protocols for preparing Ni and Zn triarylcorrole complexes. In the case of Zn, the preliminary oxidation of the free base corrole in DMSO to the neutral corrole radical is a necessary step to obtain the coordination of the metal ion, because the direct reaction led to the formation of an open-chain tetrapyrrole. The Ni complex could be directly obtained by heating the free base corrole and Ni(II) salt to 100 °C in a DMSO solution containing FeCl3. The non-innocent nature of the corrole ligand for both complexes has been elucidated by EPR, and in the case of the Zn derivative the first spectroelectrochemical characterization is presented. peerReviewed

The development of chemical sensors is an urgent need for both environmental and health issues. The breakthrough needed for the advancement of these devices is the development of efficient receptors. Porphyrins have been widely used as sensing layers in chemical sensors, but their integration with nanostructures can greatly boost the performance of these macrocycles, improving from one side the stability of the sensing layer, and from the other, offering additional interaction mechanisms with target analytes. We present here some recent examples of hybrid materials prepared by the integration of porphyrins with metal and metal oxide nanoparticles, porphyrin-based metal organic frameworks and their exploitation as sensing layers in chemical sensors.

Owing to the electron‐donating and ‐accepting nature of corroles (Corr) and phthalocyanines (Pc), respectively, we designed and developed two novel covalently linked Corr‐Pc conjugates. The synthetic route allows the preparation of the target conjugates in satisfying yields. Comprehensive steady‐state absorption, fluorescence, and electrochemical assays enabled insights into energy and electron‐transfer processes upon photoexcitation. Coordinating a pyridine‐appended subphthalocyanine (SubPc) to the Pc of the conjugate sets up the ways and means to realize the first example of an array composed by three different porphyrinoids, which drives a cascade of energy and charge‐transfer processes. Importantly, the SubPc assists in stabilizing the charge‐separated state, that is, one‐electron oxidized Corr and the one electron‐reduced Pc, upon photoexcitation by means of a reductive charge transfer to the SubPc. To the best of our knowledge, this is the first case of an intramolecular oxidation of a Corr within electron‐donor–acceptor conjugates by means of just photoexcitation. Moreover, the combination of Corr, Pc, and SubPc guarantees panchromatic absorption across the visible range of the solar spectrum, with the SubPc covering the „green gap“ that usually affects porphyrinoids., Cascades: The preparation of two covalently linked corrole‐Zn phthalocyanine dyads is reported. The coordination of a pyridine‐appended perfluorinated subphthalocyanine to the zinc phthalocyanine leads to the formation of supramolecular triads. Corrole acts as electron donor upon photoexcitation, with subphthalocyanine as the final acceptor. These cascade‐like charge phenomena make these triads promising materials in molecular photovoltaics (see figure).

Porphyrinoids are considered perfect candidates for their incorporation into electron donor–acceptor (D–A) arrays due to their remarkable optoelectronic properties and low reorganization energies. For the first time, a series of subphthalocyanine (SubPc) and corrole (Cor) were covalently connected through a short-range linkage. SubPc axial substitution strategies were employed, which allowed the synthesis of the target molecules in decent yields. In this context, a qualitative synthetic approach was performed to reverse the expected direction of the different electronic events. Consequently, in-depth absorption, fluorescence, and electrochemical assays enabled the study of electronic and photophysical properties. Charge separation was observed in cases of electron-donating Cors, whereas a quantitative energy transfer from the Cor to the SubPc was detected in the case of electron accepting Cors, This work was supported by the Spanish MINECO, PID2020- 116490GB I00 (Porphyrinoids, T.T) and by the Italian PRIN MIUR “SUNSET“ 2017EKCS35_002. IMDEA-Nanociencia also acknowledges support from the “Severo Ochoa” Programme for Centres of Excellence in R&D (MINECO, Grant SEV-2016-0686)

In this work, we report the investigation of Fe and Co triphenylcorrole complexes supported on two different carbon supports as eletrocatalysts for the ORR in neutral pH media, comparing their performances with the corresponding tetra- phenylporphyrin complexes. Cyclic voltammetry experiments were acquired in neutral phosphate buffer demonstrating that corroles exhibit a superior catalytic activity towards ORR than porphyrins, as demonstrated by more positive oxygen reduc- tion peak potential (Epr) and half-wave potential (E1/2) values of corroles. Also, iron complexes performed better than cobalt ones, showing an ORR activity even superior to that of platinum taken as reference, as demonstrated by RDE experiments. We investigated the role of the axial ligand on the ORR activity of the macrocycles, and we found that Epr and E1/2 values are more positive along the series: PPh3Co < py2Co = μ-oxoFe2 < FeCl. By contrast, there was not much difference in activity support- ing the porphyrinoids on carbon nanotubes or carbon black pearls, indicating that the effect of carbon support is less im- portant to that of the axial ligand. The results allowed pointing at iron corroles as a promising class of molecular catalysts for application as cathodes in biolectrochemical systems at neutral pH, such as microbial fuel cells.

Electron-donating corroles (Cor) were integrated with electron-accepting phthalocyanines (Pc) to afford two different non-covalent Cor ⋅ Pc systems. At the forefront was the coordination between a 10-meso-pyridine Cor and a ZnPc. The complexation was corroborated in a combination of NMR, absorption, and fluorescence assays, and revealed association with binding constants as high as 10

Two synthetic routes for the preparation of the water soluble 5,10,15‐tris(4‐sulfonatophenyl)corrole are reported. The first approach explores the chlorosulfonation reaction on the phosphorus complex of 5,10,15‐tris(4‐trimethylsilylphenyl)corrole. Following this route, the P complex of the target corrole has been obtained in low yields, while the major product was the tetrasubstituted complex, with the additional sulfonyl group regioselectively introduced at the 2‐position. To widen the scope of the reaction, the direct preparation of the 5,10,15‐tris(4‐sulfonatophenyl)corrole has been pointed out, affording both the target corrole and the intermediate chlorosulfonyl derivative in reasonable yields. The photophysical properties and the protonation equilibria of both corroles have been investigated, showing that 5,10,15‐tris(4‐sulfonatophenyl)corrole does not aggregate in acidic solutions, different from the analogous porphyrin.

The coordination chemistry of corrole is one of the most intriguing aspects of this contracted porphyrinoid, for both theoretical and practical reasons. Corrole, in fact, shows a remarkable coordinative versatility, and several elements have been coordinated in formally high oxidation states, because of its trianionic character as ligand and the high electron density. These feature s , however, prompt corrole to show a non innocent ligand character, making difficult to elucidate the electronic structure of the corresponding complexes. These characteristics make corrole complexes of interest for a wide range of application fields, going from catalysis to chemical sensors. The important progresses in the synthetic pathways of this macrocycle have also been an important factor to widen the “periodic table” of metallocorroles, which is now large as much as that of the corresponding metalloporphyrins. All these features make corrole one of the most popular macrocycle in the porphyrinoids field. This is confirmed by the impressive number of the published articles related to metal complexes of corrole in the 2016–2018 period, which is the focus of this review.

Two different copper and gallium arylcorroles have been functionalized using the Vilsmeier-Haack reaction. A further Knoevenagel reaction with cyanoacetic acid was performed on both complexes, affording the desired products with yields above 90 %. The newly synthesized compounds have been thoroughly characterized by a combination of spectroscopic methods, optical analyses, and X-ray crystallography. Moreover, they have been tested as anchoring groups for the hydrothermal synthesis of ZnO nanoparticles. The morphology of the heterogeneous composites has been studied by SEM, EDS and fluorescence microscopy analyses, thus confirming the presence of the corrole macrocycle in the hybrid material.

Porphyrins and carbon nanomaterials are among the most widely investigated and applied compounds, both offering multiple options to modulate their optical, electronic and magnetic properties by easy and well-established synthetic manipulations. Individually, they play a leading role in the development of efficient and robust chemical sensors, where they detect a plethora of analytes of practical relevance. But even more interesting, the merging of the peculiar features of these single components into hybrid nanostructures results in novel materials with amplified sensing properties exploitable in different application fields, covering the areas of health, food, environment and so on. In this contribution, we focused on recent examples reported in literature illustrating the integration of different carbon materials (i.e., graphene, nanotubes and carbon dots) and (metallo)porphyrins in heterostructures exploited in chemical sensors operating in liquid as well as gaseous phase, with particular focus on research performed in the last four years.

The reaction of 5,10,15-tritolylcorrole with 3-dimethylaminoacrolein (3-DMA) and POCl3 gives a further example of the rebel reactivity of this contracted macrocycle. While no evidence was obtained for the formation of the expected &beta, acrolein corrole, the inner core substituted N21,N22-3-formylpropylcorrole and the 10-acrolein isocorrole were the reaction products. By increasing the temperature or the amount of the Vilsmeier reagent, the 10-isocorrole became the unique reaction product. The formation of the isocorrole by electrophilic attack of the Vilsmeier reagent to the 10-position of the corrole is unprecedented in the porphyrinoids field and it could pave the way for a novel route to the preparation of stable isocorroles.

A low-cost on-paper sensor based on 5,10,15-tritolylcorrolatocobalt(III) triphenylphosphine, CoTTCorr(PPh3), was developed for cyanide detection in aqueous solutions. The sensor was coupled to a smartphone and used a home-written color intensity analysis software in order to record and interpret the colorimetric response. The detection of cyanide was possible down to 0.053 mg/L, an order of magnitude lower than the value of 0.5 mg/L set by the World Health Organization (WHO) for safe short-term exposure of cyanide in potable water. The colorimetric sensor had selectivity toward cyanide ions over the anions Cl-, Br, F-, NO2, SCN-, OA[Formula: see text]-,ClO4-, H2PO4- and HCO3- while the influence of NO3- ions on the sensor optical response towards cyanide was overcome by optimization of the ionophore/anion-exchanger ratio inside the sensing material. The best performance was obtained for the optode with an ionophore to exchanger ratio of 1:3. The optimized optodes were employed for quantification of cyanide content added to potable water and saliva.

A series of 5,10,15-triarylcorroles has been prepared, with the meso-aryl rings functionalized with different substituents to investigate their influence on the aryl ring rotation with respect to the corrole plane. The study has been carried out by different NMR techniques, allowing the complete assignment of the 1H NMR spectra and giving insights on the kinetic and thermodynamic factors driving the atropisomerism in triarylcorrole derivatives.

Corrole continues to attract the interest of different research groups, since this macrocycle shows peculiar and intriguing characteristics, which open its application in different fields. In the last few years, we have been interested to exploit corrole derivatives as receptors in chemical sensors, because the peculiar coordination chemistry of this contracted macrocycle can allow the preparation of optimized cross sensitive sensor arrays. For this reason, the functionalization of the corrole is a fundamental step for the optimization of the macrocycle features for the target application. We have been interested in the introduction at the peripheral positions of the corrole ring of different substituents, because they can allow the preparation of hybrid materials. These hybrid materials have been successfully exploited to develop chemical sensors. The characterization of these species, together the applications of the functionalized corroles will be presented and discussed.

We report a low-cost sensing platform for effective naked-eye detection of fluoride ion in aqueous media. The sensor is based on silicon complex of 5,10,15-tritolylcorrole (SiTTCorr) deposited on paper support and designed in a particular way that permits it to perform in a unique sensing event an internal sensor self-calibration and subsequent analysis of fluoride ion in a concentration range from 20 [Formula: see text]g/L to 200 mg/L with a LOD 9 [Formula: see text]g/L, much lower than the WHO guideline value of 1.5 mg/L for fluoride in drinking water. The influence of tetradodecylammonium chloride (TDACl) anion exchanger addition to the performance of SiTTCorr-based sensors was studied and the sensor with optimal ionophore: exchanger [Formula: see text] 2:1 ratio demonstrated the highest sensitivity. The evident color variation of SiTTCorr-based optode from dark pink to intense green occurred upon addition of increasing concentrations of fluoride. A smartphone application equipped with home-written color intensity analysis software as a detector of developed sensor output permitted fluoride content quantification in bottled water and toothpaste samples. Moreover, since at the quantification step the SiTTCorr color variation was significant for the red component of visible light and increase of fluoride content evidently changed this color from red to yellow and then to green, the developed optode was compared to a kind of chemical traffic light, able to detect the presence of fluoride in permitted, borderline or dangerous concentrations, respectively.

Reaction of 2-amino-3-(pyrrol-1-yl)-5,10,15-tris(4-tert-butylphenyl)corrolato copper(II) with arylaldehydes affords novel π-extended β,β'-pyrrolo(1,2-a)pyrazino-fused corroles via a Pictet-Spengler reaction. Corrole shows an unprecedented reaction pathway, leading to a mixture of phenyl-substituted and nonsubstituted pyrrolopyrazino annulated species as reaction products.

A novel method for the preparation of corroles with β-fused pyrazino rings was developed, exploiting a one-pot reaction of 2,3-diaminocorroles (or 2,3,17,18-tetraaminocorroles) with different diones; a variety of π-extended corroles were obtained in moderate yields as copper complexes, which can then be demetallated to give the corresponding free base in good yields.

Corrole continues to attract the interest of different research groups, since this macrocycle shows peculiar and intriguing characteristics, which open its application in different fields. For this reason, the functionalization of the corrole is a fundamental step for the optimization of the macrocycle features for the target application. We have been interested in the introduction at the peripheral positions of the corrole ring of acroleyl groups by Vilsmeier reaction, because they can allow the preparation of hybrid materials by grafting the corrole derivative onto poly-acrolein microballs. These hybrid materials have been successfully exploited to develop chemical sensors. The regioselectivity of the Vilsmeier reaction strongly depends on the corrole structure and in the case of the free base the macrocyclic inner core showed an unexpected reactivity. The characterization of these species, together the applications of the functionalized corroles will be presented and discussed.

Copper and gallium β-acrolein corroles have been obtained by reaction of corrole complexes with 3-(dimethylamino)-acrolein/phosphoryl chloride (3-DMA/POCl3) under Vilsmeier conditions. In the case of the Ga complex, up to four acroleyl substituents have been introduced at the β-peripheral positions of the corrole macrocycle. The introduction of the acroleyl moiety on the corrole scaffold strongly influences the photophysical behaviour of the Ga corroles.

The impressive chemistry shown by porphyrins in natural systems is particularly attractive for exploitation in chemical sensors. In these devices the sensing mechanisms can mimic most of the porphyrin biological reactivity, such as reversible binding, activation of small molecules, redox activity, and photoactivated processes. The simultaneous presence of multiple binding mechanisms allows porphyrins to interact with a large variety of analytes. This feature reduces the selectivity, but prompts the development of sensor arrays, where the cross-selectivity of more sensors is used to classify and identify samples characterized by a complex composition. Since 1995 the Sensors Group of the University of Rome Tor Vergata has exploited these features to prepare sensor arrays based on different transducers and aimed at several applications. These kinds of devices have been reported as electronic noses (gaseous phase analytes) and electronic tongues (liquid phase analytes) to underline that their working mechanisms are tentatively similar to that of biological senses. We report here some of the results obtained.

Thin film deposition of porphyrinoids is a critical step for the development of reliable chemical sensors. The binding properties, in liquid phase, of these compounds should be in fact preserved as much as possible in the solid state, to allow an efficient recognition of target analytes. However, the solid-state arrangements of these macrocycles could offer additional binding mechanisms that exceed those possible to the single molecules allowing to even enhance the superb binding versatility of porphyrinoids. In this manuscript, we have reviewed mostly our approach for the thin film deposition of porphyrinoids, going from the simple, noncontrolled techniques to the preparation of composite inorganic/organic materials. All these opportunities drive the aggregation of porphyrinoids by supramolecular interactions and the possibility to merge their properties with those of inorganic materials open the way to an almost unlimited possibility to prepare optimized sensing layers.

Complexes of 5,10,15-triferrocenylcorrole were synthesized from the crude free-base corrole product obtained by the reaction of ferrocenyl aldehyde and pyrrole. Direct formation of the complex in this manner leads to an increase of the reaction yield by protecting the corrole ring toward oxidative decomposition. The procedure was successful and gave the expected product in the case of the copper and triphenylphosphinecobalt complexes, but an unexpected result was obtained in the case of the nickel derivative, where metal insertion led to a ring opening of the macrocycle at the 5 position, giving as a final product a linear tetrapyrrole nickel complex bearing two ferrocenyl groups. The purified 5,10,15-triferrocenylcorrole complexes have been fully characterized by a combination of spectroscopic methods, electrochemistry, spectroelectrochemistry, and density functional theory calculations. Copper derivatives of 10-monoferrocenyl- and 5,15-diferrocenylcorrole were prepared to investigate how the number and position of the ferrocenyl groups influenced the spectroscopic and electrochemical properties of the resulting complexes. A complete assignment of resonances in the (1)H and (13)C NMR spectra was performed for the cobalt and nickel complexes, and detailed electrochemical characterization was carried out to provide additional insight into the degree of communication between the meso-ferrocenyl groups on the conjugated macrocycle and the central metal ion of the ferrocenylcorrole derivatives.

The introduction of alkynyl groups at the β-pyrrolic positions of dibrominated corrole derivatives was attempted by using both Sonogashira and Stille coupling methodologies. An efficient bromination protocol was developed by using a silver corrolate, which enabled the regioselective preparation of the 3,17-Br2 isomer in high yield. Whereas unsatisfactory results were obtained by applying Sonogashira reaction conditions, the Stille methodology produced, for the first time, novel 3,17-diphenylethynylcorrole derivatives in good to excellent yields. A mild demetalation protocol of the silver complex led to the corresponding corrole free base, opening the way for the preparation of different metal complexes and further elaboration of the corrole platform by using alkyne chemistry. Regioselective dibromination of corrole and subsequent Stille cross-coupling allow the successful preparation of triarylcorroles functionalized at the β positions with alkynyl substituents. These derivatives represent a novel approach to modulate the macrocycle properties, opening the way for corrole-based molecular architectures featuring extensive π conjugation.

After the definition of efficient synthetic routes for the preparation of triarylcorroles, the functionalization of these macrocycles is becoming a necessary and challenging field of research. One important synthetic step is the introduction of substituents able to influence the electronic distribution in the macrocyclic ring. A valuable target would be a corrole macrocycle with some β-pyrrole positions occupied by methyl groups, while exploiting other positions to introduce electron-withdrawing substituents. To explore the scope of this approach, we investigated the bromination and the nitration of the corrole ring and the desired products have been obtained in moderate to good yield. The successful preparation of selectively halogenated corroles is particularly interesting since they are suitable substrates for the preparation of more complex partially alkylated structures using modern cross coupling methodologies.

The sulfonation reaction has been particularly useful to prepare amphiphilic derivatives of 5,10,15-tris(pentafluorophenyl)corrole, but it has been limited to this corrole. We have studied the scope of this reaction, using 5,10,15-triphenylcorrole as the prototypical example of corrole structure. The reaction protocol has been modified to avoid the corrole aggregation, which limited its reactivity in the neat chlorosulfonic acid. Surprisingly, the reaction shows an unprecedented regioselectivity for corrole derivatives, affording 3 as the main product, but also corrole 5, which is the first example of monosubstituted corrole on pyrrole B. By modulating the corrole:chlorosulfonic acid reagent ratio, it has been possible to obtain the antipodal disubstituted product 6, demonstrating again a not usual regioselectivity for corrole substitution. These results allow the preparation of novel amphiphilic corrole derivatives, which open up their potential applications in different fields.

a b s t r a c t Two palladium complexes, the (Pd( 2 -ol)(8-(di-tert-butylphosphinooxy)quinoline)) and (Pd( 2 -ol)(8- (di-tert-butylphosphinooxy)-2-methylquinoline)), have been used as sensing materials to functionalize quartz crystal microbalances (QCM). The developed sensors have been tested to determine carbon monoxide in air. The reversible binding of CO observed in CH2Cl2 solution for both complexes is retained in the solid state. The functionalized QCMs showed good reproducibility and sensitivity toward CO detec- tion. While CO detection was not influenced by the presence of molecular hydrogen and methane, the humidity reduced the sensors sensitivity, although the functionalized QCMs were still able to discriminate CO.

An innovative and efficient β-functionalization of [5,10,15-tris-(4-methylphenyl)corrolato]Cobalt derivatives introduced an acrolein substituent, which allowed the copolymerization with pure acrolein. The obtained hybrid microparticles have been used as sensing materials of quart microbalance gas sensors. The sensing properties have been tested by exposure to different volatile organic compounds chosen as model analytes. Results show an improved sensitivity of the hybrid microparticles respect to the individual constituents.

Porphyrins and related macrocycles have been intensively exploited as sensing materials in chemical sensors, since in these devices they mimic most of their biological functions, such as reversible binding, catalytic activation, and optical changes. Such a magnificent bouquet of properties allows applying porphyrin derivatives to different transducers, ranging from nanogravimetric to optical devices, also enabling the realization of multifunctional chemical sensors, in which multiple transduction mechanisms are applied to the same sensing layer. Potential applications are further expanded through sensor arrays, where cross-selective sensing layers can be applied for the analysis of complex chemical matrices. The possibility of finely tuning the macrocycle properties by synthetic modification of the different components of the porphyrin ring, such as peripheral substituents, molecular skeleton, coordinated metal, allows creating a vast library of porphyrinoid-based sensing layers. From among these, one can select optimal arrays for a particular application. This feature is particularly suitable for sensor array applications, where cross-selective receptors are required. This Review briefly describes chemical sensor principles. The main part of the Review is divided into two sections, describing the porphyrin-based devices devoted to the detection of gaseous or liquid samples, according to the corresponding transduction mechanism. Although most devices are based on porphyrin derivatives, seminal examples of the application of corroles or other porphyrin analogues are evidenced in dedicated sections.

The synthesis, spectroscopic, and optical properties of the water-soluble phosphorus complex of a 2-sulfonato-10-(4-sulfonatophenyl)-5,15-dimesitylcorrole have been investigated. The compound was prepared by adopting a novel strategy for the corrole sulfonation, leading to the regioselective isomer in an almost quantitative yield. The phosphorus coordination has a key role in determining the corrole substitution pattern, limiting the formation of poly-substituted species, which affected the reaction of the corrole free base. The resulting complex shows excellent optical properties in terms of emission quantum yield, also in polar protic solvents, including water. 31P NMR spectroscopy in CD3OD indicates that the P sulfonate complex has been isolated in a hexacoordinated geometry with two different ligands (L1=-OH, L2=-OCH3), and it is prone to axial ligand exchange with methanol, with no evidence of intermediate pentacoordinated species. The morphological characterization of thin layers of the P corrole deposited onto an Au(111) surface showed that the addition of an intermediate layer of reduced graphene oxide allows for a better control of corrole aggregation, inducing also transformation of the Au(111) reconstructed surface. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

An efficient β-functionalization of [5,10,15-tris-(4-methylphenyl)corrolato]cobalt derivatives through a Vilsmeier-type reaction allows the introduction of an acrolein substituent, which is subsequently copolymerized with pure acrolein. The obtained hybrid microspheres are exploited as nanogravimetric chemical sensors. The sensing properties of the developed sensors are tested through exposure to different volatile organic compounds chosen as model analytes. The results show improved sensor sensitivity of the resulting devices for all the tested analytes with respect to sensors functionalized with either corrole or polyacrolein. The enhanced properties are attributed to the accurate and tunable merging of the properties of both exploited materials.

The reaction of 5,10,15-tris(4-tert-butylphenyl)corrole with 2,3-bis(bromomethyl)-5,6-dicyanopyrazine provides a new example of corrole ring expansion to a hemiporphycene derivative. The ring expansion is regioselective, with insertion of the pyrazine derivative at the 5-position of the corrole ring, affording the corresponding 5-hemiporphycene. Different macrocyclic products accompany formation of the 5-hemiporphycene, depending on the reaction experimental conditions. Br-substitued 5-hemiporphycenes and the 2-Br substituted corrole were obtained in 1,2,4-trichlorobenzene, while in refluxing toluene traces of an inner core substituted corrole were observed together with a significant amount of the unreacted corrole. These results provide an important indication of the reaction pathway. The coordination behavior of the 5-hemiporphycene, together with detailed electrochemical characterization of the free-base and some metal complexes, provides evidence for the reactivity of the peripheral pyrazino group.

β–Nitrocorrole derivatives are potentially valuable platforms for the preparation of a wide range of more elaborated corrole derivatives possessing unique chemical functionalities and electronic properties. Here we report our results on the chemical manipulation of a copper 3-NO2-triarylcorrolate using different organic reactions, all involving the reduction of –NO2 to –NH2 at an early stage, followed by further transformations. By way of a β-acylated copper corrolate, a novel corrole derivative bearing an alkyl azide group on the peripheral positions was obtained and exploited in the Huisgen 1,3-dipolar cycloaddition.

The β-nitration reaction carried out on the corrole macrocycle has been shown to be extremely regioselective, although the reduced symmetry of the macrocycle could potentially lead to a huge number of possible regioisomers. We recently reported that the careful use of AgNO 2/ NaNO 2 as a nitrating system enabled the achievement in good yields of mono- and dinitro-derivatives on both corrole free base and its copper complex, proving to be an efficient and cost-effective method. In this work, we present a detailed study of the scope of this method using TtBuCorrH 3 as a model corrole. A further increase of the oxidant pushes the nitration up to the functionalization of three β-pyrrolic positions, although concomitant decomposition of the macrocycle is also observed. The application of the proven nitration method with a five-fold excess of both silver and sodium nitrites with respect to corrole, afforded the 2,3,17-( NO 2)3- TtBuPCorrCu as the main product, in 25% yield, together with traces of another compound identified by X-ray crystallographic analysis as the 3,8,17-( NO 2)3- TtBuPCorrCu isomer. In light of these recent results, we also reinvestigated the characterization of the nitration products obtained from bis-substitution reactions, allowing among others the identification of the copper 3,8-( NO 2)2 corrolate.

A diiminoisoindolo-pyrazino unit was annulated to the β-pyrrolic position of the Zn complex of tetraphenylporphyrin, giving a macrocycle with an expanded π system in satisfactory yields. The crystal structure of this derivative evidenced the formation of a hydrogen bond network. The interaction of the β-fused isoindoline porphyrin derivative with nucleotides and nucleic acids has been investigated.

A thoroughly structural characterization of (TTC)GePh (TTC [Formula: see text] 5,10,15-tritolylcorrole; Ph [Formula: see text] phenyl) in solution has been carried out through a combination of 2D NMR (1H-1H COSY, 1H-1H ROESY, 1H-[Formula: see text]C HSQC and 1H-[Formula: see text]C HMBC) experiments and density functional theory (DFT) calculations of the molecular and electronic structure and the shielding constants. The 1H and [Formula: see text]C chemical shifts computed at DFT-S12g and DFT-SAOP levels of theory nicely reproduce the experimental values, the agreement between theory and experiment being especially good for the DFT-S12g results. The calculations prove to be able to capture the fine details of the NMR spectra and to resolve some assignment ambiguities related to the inherent conformational flexibility of the macrocycle. The calculations also provide an explanation of the observed chemical shift trends in terms of diamagnetic and paramagnetic components of the shielding tensor.

Hierarchical self-assembly of porphyrins is an intrigue research field, which can lead to the design of functional materials. Porphyrin derivatives self-assembling under hierarchical control allows to understand the principles governing molecular recognition processes, as demonstrated for meso-tetrakis(4-phosphonatophenyl)porphyne (H2TPPP) whose polyprotic nature is responsible for a pH-dependent hierarchical aggregation. Herein, self-assembly of meso-tris(4-phosphonatophenyl)corrole (TPPC) in aqueous solution has been spectroscopically studied and compared to that of TPPP. The corrole aggregation does not follow the hierarchical rules that govern the porphyrin counterpart due to the accessibility of the core of the macrocycle to protons, promoted by the reduced number of involved intermolecular H-bonds.

Functionalization of corrole at its peripheral positions is an intriguing field of research, since the unusual reactivity of this macrocycle usually makes it difficult to predict the reaction products. We have investigated the introduction of halogen atoms at the corrole β-positions by using haloacids as reagents. Different behavior, in terms of number and position of the units introduced, was observed: chlorination yielded mono and disubstituted corrole, whereas bromination only afforded mono-substitution, even if on different positions. Iodination did not occur on the corrole free base, while the protection of the inner core by chelation with silver ion gave better results and a symmetric diiodinated corrole was isolated. 2D NMR analysis and X-ray crystallography provided useful information about the site of these corrole functionalizations.

The reaction of 5,10,15-tritolylcorrole with EtMgBr opens the way for novel functionalizations of the corrole ring. DDQ oxidation of the macrocycle, followed by addition of the Grignard reagent, led to the formation of 5- and 10-alkyl substituted isocorroles in satisfying yields. Together with the one-pot formation of these isocorrole isomers, the use of such a nucleophile evidenced the competitive reactivity of the macrocycle β-positions, leading to the formation of 2-bromo- and 3-bromo-5,10,15-tritolylcorrole. While the formation of these monobromocorrole derivatives is not unprecedented, this is the first time the isomers have been separated and fully characterized. Furthermore, the higher yields of the 2-substituted species highlight a useful regioselectivity for the substitution reaction.