Synthesis of Vanadyl Complexes of N-Confused Porphyrins and Their Bromoperoxidase-like Catalytic Activity

Two new vanadyl complexes of N-confused porphyrins (NCPs), [VONCTPP] (V-1) and [VONCP(OMe)8] (V-2), have been synthesized for the first time and investigated as a catalyst for the oxidative bromination reaction of phenol and its derivatives. This article further delineates crystal structures, photophysical, and redox properties of both the vanadyl complexes. Complexes V-1 and V-2 exhibited a significant red shift in their absorption spectra compared with their respective free bases. The single-crystal structure of V-1 revealed that the complex is in the 2H tautomeric form, while EPR studies revealed the +4 oxidation state of vanadium metal having an axial compression with dxy1 configuration. Catalytic potential for bromoperoxidases-like activity has been explored for both complexes V-1 and V-2 for the first time in NCP chemistry with excellent TOF values (4.7-6.3 s-1 for V-1 and 7.3-8.7 s-1 for V-2) using KBr as a source of bromine and H2O2 as a green oxidant in aqueous acidic medium at 298 K. Notably, both catalysts show excellent recyclability over five cycles. The vanadyl-metalated NCPs exhibit excellent stability in the air.

Synthesis, Spectral, Redox, and Sensing Studies of β-Dicyanovinyl-Appended Corroles and Their Metal Complexes

A new family of β-dicyanovinyl (DCV)-appended corroles represented as MTPC(MN) (where M = 3H, Cu, Ag, and Co(PPh₃) and MN = malononitrile and TPC = 5,10,15-triphenylcorrole) were synthesized starting from the free base mono β-formyl corrole, H₃TPC(CHO), and characterized along with their respective MTPC(CHO) and MTPC complexes as to their spectroscopic and electrochemical properties in nonaqueous media. Comparisons between the two series of corroles demonstrate a pronounced substituent effect of the β-DCV group on the physicochemical properties making the MTPC(MN) derivatives substantially easier to reduce and more difficult to oxidize than the formyl or unsubstituted corroles. In addition, the colorimetric and spectral detection of 11 different anions (X) in the form of tetrabutylammonium salts (TBAX, X = PF₆^-, OAc^-, H₂PO₄^-, CN^-, HSO₄^-, NO₃^-, ClO₄^-, F^-, Cl^-, Br^-, and I^-) were also investigated in nonaqueous media. Of the investigated anions, only CN^- was found to induce changes in the UV-vis and ¹H NMR spectra of the β-DCV metallocorroles. This data revealed that CuTPC(MN) and AgTPC(MN) act as chemodosimeters for selective cyanide ion detection via a nucleophilic attack at the vinylic carbon of the DCV substituent, while (PPh₃)CoTPC(MN) acts as a chemosensor for cyanide ion sensing via axial coordination to the cobalt metal center. A low-limit detection of cyanide ions was observed at 1.69 ppm for CuTPC(MN) and 1.17 ppm for AgTPC(MN) in toluene.

Oxido-Molybdenum(V) Corroles as Robust Catalysts for Oxidative Bromination and Selective Epoxidation Reactions in Aqueous Media under Mild Conditions

Two new meso-substituted oxido-molybdenum corroles were synthesized and characterized by various spectroscopic techniques. In the thermogram, MoO[TTC] (1) exhibited excellent thermal stability up to 491 °C while MoO[TNPC] (2) exhibited good stability up to 318 °C. The oxidation states of the molybdenum(V) were verified by electron paramagnetic resonance (EPR) spectroscopy and exhibited an axial compression with d_xy¹ configuration. Oxido-molybdenum(V) complexes were utilized for the selective epoxidation of various olefins with high TOF values (2066-3287 h^-1) in good yields in a CH₃CN/H₂O (3:2, v/v) mixture in the presence of hydrogen peroxide as a green oxidant and NaHCO₃ as a promoter. The oxidative bromination catalytic activity of oxido-molybdenum(V) complexes in an aqueous medium has been reported for the first time. Surprisingly, MoO[TNPC] (2) biomimics of the vanadium bromoperoxidase (VBPO) enzyme activity exhibited remarkably high TOF values (36 988-61 646 h^-1) for the selective oxidative bromination of p-cresol and other phenol derivatives. Catalyst MoO[TNPC] (2) exhibited higher TOF values and better catalytic activity than catalyst MoO[TTC] (1) due to the presence of electron-withdrawing nitro groups evident from cyclic voltammetric studies.

Corroles at work: a small macrocycle for great applications

Corrole chemistry has witnessed an impressive boost in studies in the last 20 years, thanks to the possibility of preparing corrole derivatives by simple synthetic procedures. The investigation of a large number of corroles has highlighted some peculiar characteristics of these macrocycles, having features different from those of the parent porphyrins. With this progress in the elucidation of corrole properties, attention has been focused on the potential for the exploitation of corrole derivatives in different important application fields. In some areas, the potential of corroles has been studied in certain detail, for example, the use of corrole metal complexes as electrocatalysts for energy conversion. In some other areas, the field is still in its infancy, such as in the exploitation of corroles in solar cells. Herein, we report an overview of the different applications of corroles, focusing on the studies reported in the last five years.

β-Bis-CF3-substituted phosphorus corroles, theory and experiments

All constitutional isomers of beta bis-CF3 substituted (tpfc)PF2 were geometrically optimized and studied electronically. The six synthetically accessed compounds were characterized (of the 18 possible) by NMR spectroscopy and other techniques.

The inner oxygen-substituted strategy effects on structure, aromaticity and absorption spectra of corrole isomers: A theoretical study

Corrole and oxaporphyrin have been successfully synthesized and applied in many research fields such as organic photoelectronics and sensors with the unique photophysical and chemical properties. However, the low synthesis yields of oxacorrole drive researchers turning their attention to theoretical studies for more reasonable molecular structure as the appeal of energy conservation and green chemistry. Corroles, oxacorroles (OC) and dioxacorroles (DOC), a total of 14 molecules, are calculated to systematically explore their structures, intramolecular hydrogen bonds, molecular aromatic and absorption spectral properties influenced by the inner O atoms positions with density functional theory (DFT) and time-dependent density functional theory (TDDFT). The smaller NICS(1)_ZZ values of oxacorrole (-35.23 ppm to -33.54 ppm) and dioxacorrole (-34.91 ppm to -33.24) than these of corroles (-32.97 ppm and -33.12 ppm) indicate that the O atoms attendances can increase the molecular aromaticity. The gradually increasing energy gaps of H-8 to H-3 from Corrole1 and Corrole2 to DOC series and the larger charge of C_O (+0.208e-+0.380e) than that of C_N (+0.065e-+0.177e) illustrate that the substitution of O can reduce the degeneracy degree of energy levels and change the charge distributions. With Hirshfeld method, the molecular orbital contributions of H-1, HOMO, LUMO and L+1 exhibit the regular effects of O atoms positions on orbital energy and electron absorption spectra. For series 1, 23O is beneficial to the red shift of electron absorption spectra. These theoretical conclusions manifest that OC1-23 and DOC1-1 possess the excellent absorption characteristics in the visible region, which can be used as potential materials in the fields of photoelectric materials.

Corroles: The Hitherto Elusive Parent Macrocycle and its Metal Complexes

Corroles, macrocycles that owe their name to the cobalt-chelating prosthetic group of vitamin B12 and share numerous features with the iron-chelating porphyrin present in heme proteins/enzymes, constantly cross new boundaries ever since stable derivatives became easily accessible. Particularly important is the increasing utilization of corroles and the corresponding metal complexes for the benefit of mankind, in terms of new drug candidates for treating various diseases and as catalysts for sustainable energy relevant processes. One challenge is to gain access to the plain macrocycle, as to allow for full elucidation of the most fundamental properties of corroles. We have obtained the substituent-free corrole by several surprising and conceptually different pathways. Selected features of the corresponding metal complexes are illuminated, for pointing towards unique phenomena that are anticipated to largely expand the horizon regarding their utilization for contemporary catalysis.

Solvent Effects on the Phosphorescence of Gold(III) Complexes Chelated by β-Multisubstituted Corroles

A set of gold corrole complexes containing four different β-substituent groups (Br/I/CF₃), namely, 4Br-Au, 4I-Au, and 4CF₃-Au, were investigated; all showed room temperature phosphorescence. The phosphorescence quantum yields of the corroles were determined using tetraphenylporphyrin as a reference: Φ_ph (4I-Au, 0.75%) > Φ_ph (4Br-Au, 0.64%) > Φ_ph (4CF₃-Au, 0.38%). 4CF₃-Au exhibited near-IR emission (858 nm, aerobic); absorbance intensity for the Q-band was higher than that for the Soret band. Complex 4I-Au showed a longer phosphorescence lifetime (82 μs) compared to those of 4Br-Au (53 μs) and 4CF₃-Au (28 μs; N₂, tol). Thermally activated delayed fluorescence (TADF) emission of 4I/Br-Au complexes was observed: stronger emission intensity correlated with increasing temperature. Good negative correlations for 4I/Br-Au were observed between the Soret band absorption energy and the solvent polarizability: excited states of 4I/Br-Au are more polar than their ground states. TD-DFT calculations revealed very fast intersystem crossing (ISC) rate constants, 2.20 × 10¹² s^-1 (4CF₃-Au) > 1.96 × 10¹¹ s^-1 (4Br-Au) > 1.15 × 10¹¹ s^-1 (4I-Au), and importantly, the reverse intersystem crossing (rISC) rate constants are determined as 1.68 × 10⁷ s^-1 (4I-Au) > 2.40 × 10³ s^-1 (4Br-Au) ≫ 8.09 × 10^-8 s^-1 (4CF₃-Au). The exceptionally low rISC rate constant of 4CF₃-Au is attributed to its more steric and deformed structure bearing a larger energy gap between the S₁ and T₁ states.

Minding our P-block and Q-bands: paving inroads into main group corrole research to help instil broader potential

Main group chemistry is often considered less "dynamic" than transition metal (TM) chemistry because of predictable VSEPR-based central atom geometries, relatively slower redox switching and lack of electronic d-d transitions. However, we delineate what has been made possible with main group chemistry to give it its proper due and up-to-date treatment. The huge untapped potential regarding photophysical properties and functioning hereby spurred us to review a range of corrole reports addressing primarily photophysical trends, synthetic aspects, and important guidelines regarding substitution and inorganic principles. We also look at Ag and Au systems and also consider substitutions such as CF3, halogens, additives and also counterions. Throughout, as well as at the end of this review, we suggest various future directions; further future industrial catalytic and health science research is encouraged.

Investigation of the biological and photophysicochemical properties of new non-peripheral fluorinated phthalocyanines

The photophysicochemical and biological properties of new fluorinated phthalocyanines were examined. The synergistic effect of phthalocyanines used as colorants in ink formulas with other chemicals available was investigated for the first time.

Clean Ar-Me conversion to Ar-aldehyde with the aid of carefully designed metallocorrole photocatalysts

Toluene, p-xylene and mesitylene were cleanly converted to their corresponding monoaldehydes via mild photooxygenation utilizing transition metal and main group β-CF₃-substituted corroles. Aldehyde yield increased as more electron-donating CH₃ groups are present on the substrate. 4-P was most efficient (TON ∼ 1072, mesitylene) via the singlet oxygen vis the superoxide mechanism.

Enhanced Synthetic Access to Tris-CF3-Substituted Corroles

Separate focus on the oligomerization and oxidative cyclization steps required for the synthesis of 5,10,15-tris(trifluoromethyl)corrole revealed [bis(trifluoroacetoxy)iodo]benzene (PIFA) as a superior alternative oxidant. Under optimized conditions, the pure free-base corrole was obtained with a 6-fold increase in chemical yield and an 11-fold rise in isolated material per synthesis. The corresponding gallium(III) and manganese(III) complexes were isolated by adding the appropriate metal salt prior to corrole purification.