Copper Corroles Research Articles

Molecular Geometry and Electronic Structure of Copper Corroles.

Copper corroles are known for their unique multiconfigurational electronic structures in the ground state, which arise from the transfer of electrons from the π orbitals of the corrole to the d-orbital of copper. While density functional theory (DFT) provides reasonably good molecular geometries, the determination of the ground spin state and the associated energetics is heavily influenced by functional choice, particularly the percentage of the Hartree-Fock exchange. Using extended multireference perturbation theory methods (XMS-CASPT2), the functional choice can be assessed. The molecular geometries and electronic structures of both the unsubstituted and the meso-triphenyl copper corroles were investigated. A minimal active space was employed for structural characterization, while larger active spaces are required to examine the electronic structure. The XMS-CASPT2 investigations conclusively identify the ground electronic state as a multiconfigurational singlet (S0) with three dominant electronic configurations in its lowest energy and characteristic saddled structure. In contrast, the planar geometry corresponds to the triplet state (T0), which is approximately 5 kcal/mol higher in energy compared to the S0 state for both the bare and substituted copper corroles. Notably, the planarity of the T0 geometry is reduced in the substituted corrole compared with that in the unsubstituted one. By analyzing the potential energy surface (PES) between the S0 and T0 geometries using XMS-CASPT2, the multiconfigurational electronic structure is shown to transition toward a single electron configuration as the saddling angle decreases (i.e., as one approaches the planar geometry). Despite the ability of the functionals to reproduce the minimum energy structures, only the TPSSh-D3 PES is reasonably close to the XMS-CASPT2 surface. Significant deviations along the PES are observed with other functionals.

Deciphering Electronic and Structural Effects in Copper Corrole/Graphene Hybrids.

Non-covalent hybrid materials based on graphene and A3 -type copper corrole complexes were computationally investigated. The corroles complexes contain strong electron-withdrawing fluorinated substituents at the meso positions. Our results show that the non-innocent character of corrole moiety modulates the structural, electronic, and magnetic properties once the hybrid systems are held. The graphene-corrole hybrids displayed outstanding stability via the interplay of dispersion and electrostatic driving forces, while graphene act as an electron reservoir. The hybrid structures exposed an intriguing magneto-chemical performance, compared to the isolated counterparts, that evidenced how structural and electronic effects contributed to the magnetic response for both ferromagnetic and antiferromagnetic cases. Directional spin polarization and spin transfer from the corrole to the graphene surface participate in the amplification. Finally, there are relations between the spin transfer, the magnetic response, and the copper distorted ligand field, offering exciting hints about modulating the magnetic response. Therefore, this work shows that copper corroles emerged as versatile building blocks for graphene hybrid materials, especially in applications requiring a magnetic response.

Copper corrole immobilized onto reduced graphene oxide: An efficient electrocatalyst for hydrogen evolution reaction

First-row transition metal complexes derived from corrole-based ligands are considered efficient catalysts for hydrogen evolution reaction (HER). They are known to enhance the rate of hydrogen production by lowering the energy barrier in the water-splitting process. Here, the synthesis and characterization of a copper corrole complex (CuN2CA) having amine functionality on corrole has been reported. This complex is immobilized onto reduced graphene oxide (CuN2CA-rGO) that exhibited excellent electrocatalytic activity towards hydrogen evolution reaction (HER) with a significantly lower onset potential of -0.57 V vs. NHE efficiency of the corrole complex has significantly been improved when combined with reduced graphene oxide (rGO).

Solvent-Induced Spin-State Change in Copper Corroles.

The electronic structure of copper corroles has been a topic of debate and revision since the advent of corrole chemistry. The ground state of these compounds is best described as an antiferromagnetically coupled Cu(II) corrole radical cation. In coordinating solvents, these molecules become paramagnetic, and this is often accompanied by a color change. The underlying chemistry of these solvent-induced properties is currently unknown. Here, we show that a coordinating solvent, such as pyridine, induces a change in the ground spin state from an antiferromagnetically coupled Cu(II) corrole radical cation to a ferromagnetically coupled triplet. Over time, the triplet reacts to produce a species with spectral signatures that are characteristic of the one-electron-reduced Cu(II) corrole. These observations account for the solvent-induced paramagnetism and the associated color changes that have been observed for copper corroles in coordinating solvents.

Ultrafast Dynamics and Strong Two-Photon Absorption Properties of Nonplanar β-Functionalized “Push–Pull” Copper Corroles with a Mixed Substituent Pattern

A new series of nonplanar and unsymmetrically β-functionalized "push-pull" copper corroles, CuTPC(CHO)R7 [R = H, Br, Ph, Me, or 2-thienyl (Th)], were synthesized and characterized to elucidate the effect of β-functionalization and nonplanarity on the photophysical, redox, and nonlinear optical (NLO) properties on the corrole ring. The synthetic route to unsymmetrically β-octasubstituted copper corroles includes bromination of CuTPC(CHO) to get CuTPC(CHO)Br7 in 80% yield, which was further subjected to the Pd-catalyzed Suzuki reaction. CuTPC(CHO)Br7 exhibited a large red shift in the Soret band (Δλmax = 35-40 nm) and both the Q bands (Δλmax = 10-50 nm), as compared to CuTPC and CuTPC(CHO). CuTPC(CHO)Br7 was 510 and 290 mV anodically shifted in the first oxidation and the first reduction compared to CuTPC owing to the strong -I effect of CHO and Br groups. Density functional theory studies revealed that all the β-octasubstituted copper corroles exhibited highly nonplanar saddle-shape conformation of the corrole ring. Very high torsional saddling was observed for CuTPC(CHO)Th7 (79-83°) than that for CuTPC (49-53°), even larger than that for CuTPCBr8 (67-70°). Femtosecond laser-induced third-order NLO studies from these copper corroles showed strong two-photon absorption cross-sections (0.48-6.98 × 104 GM) and self-focusing-type positive nonlinear refraction behavior. The observed structure-dependent two-photon absorption coefficients (β) are in the range of ∼2.7-20.9 × 10-12 m/W, and the n2 values are in the range of ∼0.64-6.45 × 10-18 m2/W. The present results may facilitate a new window for these copper corroles in nonlinear optical devices, femtosecond optical limiters, and many other ultrafast photonic applications.

Ground state singlet-to-triplet conversion of copper corrole radical by β-benzo-fusion

Materials with facilely tunable spin configurations based on metal-radical coordination systems have potential applications for electronics and spintronics. Here, we report the ground state conversion of copper corrole radicals from singlet to triplet via the extension of the π-conjugation system by benzo-fusion at the β-position of corrole ligand. NMR spectroscopy, SQUID measurements and computational studies all support the ferromagnetic coupling between the Cu(II) center and corrole π-radical of benzo-fused copper corrole 2-Cu, which is in sharp contrast with the antiferromagnetic coupling in regular non-extended copper corroles. The triplet 2-Cu is highly stable in air, and X-ray diffraction analysis revealed its unique highly planar corrole macrocycle. This work offers a promising strategy for creating high-spin systems in non-innocent metallocorroles.

Probing the effect of molecular structure saddling on ultrafast charge migration via time-resolved x-ray diffraction

Metal-corroles are macrocycle organic molecules with numerous practical applications. In particular, copper corroles exhibit an interesting saddled geometry, which has attracted significant attention from theoreticians and experimentalists over the years. The present work is dedicated to understand the effect of structural saddling in a copper corrole on potential probe signals via imaging ultrafast coherent electron dynamics. A linearly polarized pulse is used to trigger the electron dynamics and time-resolved x-ray diffraction is employed to image the triggered dynamics. It is found that the symmetry reduction in the time-resolved diffraction signals and electronic flux densities is a signature of the saddling in a copper corrole during ultrafast charge migration. Moreover, analysis of the electronic flux density reveals that the diagonal nitrogen atoms mediate coherent charge migration between them via a central copper atom. Correlation of the flux densities and the diffraction signals indicates that the signature of the charge migration is encoded in time-resolved diffraction signals. A comparison of the static diffraction signals of nonsaddled planar copper porphyrin and saddled nonplanar copper corrole in their ground states is made.

Here’s looking at the reduction of noninnocent copper corroles via anion induced electron transfer

Here’s looking at the reduction of noninnocent copper corroles via anion induced electron transfer

Mechanochemical synthesis of freebase and metal corroles

Herein, we report on the mechanochemical reaction of pyrrole and substituted benzaldehyde precursors to produce freebase corroles and demonstrate the one-pot mechanochemical synthesis of 5,10,15-Tris(4-[Formula: see text]-butylphenyl)corrole (H[Formula: see text]-buPhC), in which both, the condensation and oxidation reactions steps, took place in the ball mill. Moreover, we could achieve the mechanochemical synthesis of copper corroles with decent overall yields of 10–12%. With the mechanochemical approach we could shift the EcoScale obtained from common synthesis procedures to significant more positive values and the E-factor for the mechanochemical copper insertion was lowered by factor of 3.0.

Influence of interfering gases on a carbon monoxide differential sensor based on SAW devices functionalized with cobalt and copper corroles

During the last decades, the potential impact of indoor air quality on human health has stimulated an interest in hazardous compounds survey such as carbon monoxide (CO). The detection of this compound has consequently become a vital need. To address this issue, we propose a Surface Acoustic Wave (SAW) device functionalized with metallocorroles used for the selective detection of CO. Here, we insist on the necessity to detect CO in the presence of interferents, such as O2 that is obviously present in the air, CO2 present in significant quantity in urban area (400 ppm) and humidity (H2O) which is a well-known interferent in the case of SAW-based gas sensors. We report the interest of a differential configuration of the sensor that takes advantage of accurate organic layers, to lower the sensitivity to outer parameters as well as interferents. The sensitivity of the sensor under various conditions and the repeatability of the measurements are finally shown to assess the efficiency of our device.

Copper Corrole as an Efficient Catalyst for Esterification of Allylic sp3-C—H Bonds with Carboxylic Acids

Copper Corrole as an Efficient Catalyst for Esterification of Allylic sp³-C—H Bonds with Carboxylic Acids

Copper Corrole Catalyzed Esterification of C(sp3)-H with Carboxylic Acids via Cross-Dehydrogenative Coupling Reaction

Copper Corrole Catalyzed Esterification of C(sp3)-H with Carboxylic Acids via Cross-Dehydrogenative Coupling Reaction

Biometal Corrole Active Esters and Their Amino Acid and Peptide Conjugates

The synthesis of a series of A2B‐corroles with 4‐carboxyphenyl substituent is described. The macrocycles are prepared from dipyrromethanes and 4‐formylbenzoic acid under Gryko conditions. Redox active biometal complexes are formed from the corrole carboxylic acids with the metal ions of cobalt, iron, and manganese, but not with copper. From all free corrole bases and metal complexes, the respective active esters are obtained in good yields by condensation with NHS (N‐hydroxysuccinimide) and EDC (1‐ethyl‐3‐dimethylaminopropyl‐carbodiimide). Starting from the active esters of the free corrole bases, the copper corroles are accessible in acceptable yields. Oxidation‐ and spin states of the biometal corroles correspond to those of simple corroles and are confirmed spectroscopically and magnetically. Ethylenediamine is efficiently coupled with the corrole carboxylic acids by EDC, whereby selective two‐fold coupling is observed. For the coupling to NαBoc‐lysine as well as NαFmoc‐lysine the use of corrole active esters is advantageous. The metalation of corroles carrying N‐protected lysine side chains turns out to proceed only with loss of most of the material. Here, the coupling of the amino acid building block with the metal corrole active ester proved to be the synthetically more applicable variant. The resulting NαFmoc‐lysine conjugates of both a free base corrole and a manganese corrole complex are shown to be suitable for use in Merrifield solid phase peptide synthesis.

Selective SAW-Based Carbon Monoxide Differential Sensor Functionalized with Cobalt Corroles: Influence of Interfering Gases

Introduction During the last two decades, the potential impact of indoor air quality on human health has stimulated an interest in hazardous compounds survey such as carbon monoxide (CO) [1]. The French Institute for Health Surveillance (InVS) reports that accidental domestic poisoning by the CO affects about 1000 households in France each year [2], and is responsible for about 100 deaths. The detection of this compounds has consequently become a need. To address it, we here report results on the capability of functionalized Surface Acoustic Wave (SAW) devices for the selective detection of CO. Here we insist on the necessity to detect CO in presence of interferent such as O2 that is obviously present in the air and CO2 present in significant quantity in urban area. Material SAW delay lines based on Love waves, shown in figure 1, are used to probe mass of sensitive materials deposited as a thin layer on its surface. These devices consist in two-port delay lines built on quartz. The Love wave is generated and detected using interdigited transducers (IDTs) and the frequency operation is in the vicinity of 125 MHz. A 1.5 µm thick silica guiding layer is deposited onto the IDTs providing a propagation path which permit the guidance of the acoustic wave. For the functionalization of the sensor, we take advantage of the great capabilities of cobalt corroles to trap CO molecules at the sensor’s surface with selectivity [3]. Because of the structure of the corroles, small molecules such as N2, O2 and CO2 can be trapped within by mean of weak interactions. In the particular case of CO, stronger chemical interactions are involved reaching high selectivity for this gas. In addition to this intrinsic selectivity, a second corrole has been selected to be used as a reference. This corrole exhibits the same structure as the cobalt corrole, so that it interacts with interferents in a similar way, but has no affinity to the target gaz. Method Two SAWs delay lines (A and B) shown in figure 1 are respectively coated with cobalt- and copper-corroles by mean of a spray coating method. The quantity of corroles deposited on the device is monitored during the process to avoid the deposition of an excessive amount of corroles that would damage the sensor signal compromising its proper functioning. They are then heated at 90°C for an hour under vacuum to remove the ammonia ligands present on the cobalt to prevent the corrole’s degradation in solid state. A gas-mixing bench composed of mass-flow controllers allow for generating various gas mixtures. The so prepared mixtures are sent to a dedicated test chamber that may feature up to six delay lines. Once the sensors are in the chamber, a primary vacuum and a heating is applied to remove any contaminant. A carrier gas composed of different gas of interest (N2, O2, CO2) then flows at 500 sccm through the chamber and CO is then injected at different concentrations. The shift of the synchronous frequency of the delay lines consecutive to gas adsorption is then monitored by mean of a dedicated electronics that delivers information similar to those from a classical network analyzer. Results and Conclusions As we can see in figure 2 the differential acquisition using a copper corrole allows stabilizing the sensor’s signal. Indeed, the drift of the signal on the delay line functionalized with cobalt corrole can be compensated by subtracting the one from the delay line functionalized with copper corrole. This differential acquisition results in a stable basic level of the phase signal and also an improved repeatability of the measurements (figure 3).As expected from previous work [4], we noticed a linear correlation between CO concentration, in the 100 to 7000 ppm range, and the phase shift velocity undergone by the sensors regardless of the composition of the carrier gas (figure 4). From there, we determined the sensitivity of the sensors in presence of interfering gas. It appeared that the presence of 20 % of oxygen, known as the main interferent in this measurement, in the carrier gas tends to lower by 5.5 % the sensitivity in comparison with a pure nitrogen carrier gas (figure 4). The presence of CO2 at 20 000 ppm, which represents 50 times the mean concentration in Paris, lowers the sensitivity by 19.3 % (figure 4). From these results, the selective interaction between the cobalt corrole and CO has been verified and the possibility to use it as part of a selective CO sensor has been evidenced.

Copper Complexes of CF3-Substituted Corroles for Affecting Redox Potentials and Electrocatalysis

Electrocatalysis by first-row transition metals chelated by porphyrins, corroles, and related macrocycles gains increased attention due to the need of developing approaches for clean and renewable energy. While some of the above complexes display good catalytic activity, their performance often suffers from much larger overpotentials than the extremely efficient, but not sustainable metal, platinum. Intrigued by the report of copper corroles as catalysts for the electrochemical conversion of protons to hydrogen gas, we hypothesized that trifluoromethylation of corroles would be most effective for inducing a positive shift of the potentials required for reduction of the copper chelated thereby. A combination of methodologies allowed for full characterization of the tris- and tetra-CF3-substituted complexes and elucidation of their unique structural, physical, and chemical properties. The desired outcome was also achieved, as the potential required for reduction to the copper(I) oxidation state, postulated to be the catalytically active species, was the least negative. The tris-substituted complex was found to be a particularly good electrocatalyst for production of hydrogen from protons, with a remarkably early catalytic onset potential.

Oxidative Formation and Redox Properties of 9‐Methylisocorroles

Cationic nickel(II), palladium(II), and copper(II) isocorrole complexes were obtained from linear tetrapyrrolic 2,2′‐bidipyrrin precursors by metal‐templated oxidative macrocyclization reactions using silver(I) tetrafluoroborate as the oxidant in 40–69 % yield. The new compounds were characterized by optical and resonance methods. Two products from overoxidation and attack of nucleophiles were identified by means of single‐crystal X‐ray diffraction, elucidating possible H atom transfer processes during and after the macrocyclization step. The redox behavior was studied by UV/Vis‐spectroelectrochemistry, and the complexes were found to show different stabilities of the electrogenerated radicals, depending on the nature of the central transition metal ion. A one‐electron reduction step at low potential is common for all species, but reversible only in the case of nickel, and an irreversible reaction of a copper derivative was found to produce copper corrole.

DNA interaction and photodynamic antitumor activity of transition metal mono-hydroxyl corrole

A series of iron(III), manganese(III) and copper(III) mono-hydroxyl corrole complexes had been prepared and well characterized by UV–vis, 1H NMR, 19F NMR and HR-MS. These metallocorroles may bind to CT-DNA through external binding mode. Metallocorrole Fe-2c exhibited significant phototoxicity and low toxicity toward A549 tumor cells. While manganese (III) and copper (III) corroles showed hypotoxicity to A549, MCF-7 and HepG-2 tumor cells, whether under dark or illumination conditions. All tested metallocorroles exhibited non-toxicity to human normal cells (GES-1) with or without irradiation at 625 nm. Cell cycle analysis indicated that metallocorrole Fe-2c arrested the cell cycle at G2/M phase and increased the Sub-G1 phase in A549 cell lines. It was mainly localized at mitochondria and could significantly reduce mitochondrial membrane potential after photodynamic treatment, which would further induce tumor cell apoptosis.

X-ray Absorption Spectroscopy as a Probe of Ligand Noninnocence in Metallocorroles: The Case of Copper Corroles.

The question of ligand noninnocence in Cu corroles has long been a topic of discussion. Presented herein is a Cu K-edge X-ray absorption spectroscopy (XAS) study, which provides a direct probe of the metal oxidation state, of three Cu corroles, Cu[TPC], Cu[Br8TPC], and Cu[(CF3)8TPC] (TPC = meso-triphenylcorrole), and the analogous Cu(II) porphyrins, Cu[TPP], Cu[Br8TPP], and Cu[(CF3)8TPP] (TPP = meso-tetraphenylporphyrin). The Cu K rising-edges of the Cu corroles were found to be about 0-1 eV upshifted relative to the analogous porphyrins, which is substantially lower than the 1-2 eV shifts typically exhibited by authentic Cu(II)/Cu(III) model complex pairs. In an unusual twist, the Cu K pre-edge regions of both the Cu corroles and the Cu porphyrins exhibit two peaks split by 0.8-1.3 eV. Based on time-dependent density functional theory calculations, the lower- and higher-energy peaks were assigned to a Cu 1s → 3d x2- y2 transition and a Cu 1s → corrole/porphyrin π* transition, respectively. From the Cu(II) porphyrins to the corresponding Cu corroles, the energy of the Cu 1s → 3d x2- y2 transition peak was found to upshift by 0.6-0.8 eV. This shift is approximately half that observed between Cu(II) to Cu(III) states for well-defined complexes. The Cu K-edge XAS spectra thus show that although the metal sites in the Cu corroles are more oxidized relative to those in their Cu(II) porphyrin analogues, they are not oxidized to the Cu(III) level, consistent with the notion of a noninnocent corrole. The relative importance of σ-donation versus corrole π-radical character is discussed.

Preparation of new semiconducting corrole nanostructures and their application as gas sensor

Herein, the meso-phenyl substituted corrolato copper complex Cu[Cor(Ph)2(p-HOPh)] 1 [Cor(Ph)2(p-HOPh) = 10-(4-hydroxylphenyl)-5,15-diphenylcorrole] is designed and successfully synthesized. Its self-assembly property is comparatively investigated with that of the analogue meso-phenyl substituted corrolato copper complex Cu[Cor(p-CH3OOCPh)3] 2 [Cor(p-CH3OOCPh)3 = 5,10,15-tris(p-carboxymethylphenyl)corrole] by various spectroscopic methods. The H-aggregate nature was revealed in both nanostructures formed from copper corroles 1 and 2 during the self-assembling process. But, in n-hexane copper corrole 1 self-assembled into large scale needle-like nanostructures, while copper corrole 2 self-assembled into ribbon-like bundles with long and flexible fibrils. The devices fabricated from these nanostructures display excellent semiconducting performance, with the electric conductivity as high as 1.8 × 10−4 for 1 and 2.0 × 10-3 S cm-1 for 2, respectively. Meanwhile, this two kinds of nanostructures exhibit highly sensitive n-type response to NO2 gas in the range of 100 ppb to 1 ppm at room temperature. Particularly, their sensor responses are fitting non-linear curves with respect to the NO2 gas concentrations (R2 > 0.99), suggesting the great potential applications of the copper corrolato derivatives in the field of chemical sensors.

Hydrogen and Oxygen Evolution Reactions Catalyzed By Single Site Metal Porphyrins and Corroles

Catalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are key steps involved in artificial photosynthesis for solar-energy conversion for the production of clean, carbon-free, and renewable energy sources, and thus they are considered to be appealing ways to eliminate the energy and environmental problems caused by burning fossil fuels. Extensive efforts have been made to develop efficient and robust catalysts for these two processes. Research on mononuclear metal complexes has attracted increasing attention recently because not only they are capable of catalyzing HER and OER as efficiently as multinuclear metal complexes, but also there are several advantages in synthesis and mechanism studies by using single site catalysts. In this talk, we will introduce hydrogen and oxygen evolution reactions catalyzed by single site metal porphyrins and corroles.1-6 References (1) Zhang, W.; Lai, W. Z.; Cao, R. Energy-Related Small Molecule Activation Reactions: Oxygen Reduction and Hydrogen and Oxygen Evolution Reactions Catalyzed by Porphyrin- and Corrole-Based Systems. Chem. Rev. 2017, 117, 3717-3797. (2) Han, Y. Z.; Fang, H. Y.; Jing, H. Z.; Sun, H. L.; Lei, H. T.; Lai, W. Z.; Cao, R. Singly Versus Doubly Reduced Nickel Porphyrins for Proton Reduction: Experimental and Theoretical Evidence for a Homolytic Hydrogen-Evolution Reaction. Angew. Chem. Int. Ed. 2016, 55, 5457-5462. (3) Lei, H. T.; Fang, H. Y.; Han, Y. Z.; Lai, W. Z.; Fu, X. F.; Cao, R. Reactivity and Mechanism Studies of Hydrogen Evolution Catalyzed by Copper Corroles. ACS Catal. 2015, 5, 5145-5153. (4) Lei, H. T.; Liu, C. Y.; Wang, Z. J.; Zhang, Z. Y.; Zhang, M. N.; Chang, X. M.; Zhang, W.; Cao, R. Noncovalent Immobilization of a Pyrene-Modified Cobalt Corrole on Carbon Supports for Enhanced Electrocatalytic Oxygen Reduction and Oxygen Evolution in Aqueous Solutions. ACS Catal. 2016, 6, 6429-6437. (5) Han, Y. Z.; Wu, Y. Z.; Lai, W. Z.; Cao, R. Electrocatalytic Water Oxidation by a Water-Soluble Nickel Porphyrin Complex at Neutral pH with Low Overpotential. Inorg. Chem. 2015, 54, 5604-5613. (6) Sun, H. L.; Han, Y. Z.; Lei, H. T.; Chen, M. X.; Cao, R. Cobalt Corroles with Phosphonic Acid Pendants as Catalysts for Oxygen and Hydrogen Evolution from Neutral Aqueous Solution. Chem. Commun. 2017, 53, 6195-6198. Figure 1