Synthesis and reactivity studies of a tin(II) corrole complex

Accessing Homo- and Heterobimetallic Complexes with a Dianionic Pentadentate Ligand

The tetrapyrazolylpyridyl diborate (B2Pz4Py) ligand provides a suitable platform for the isolation of heterobimetallic main-group element compounds as well as homotetrametallic copper complexes. The heterobimetallic tin(II)-lithium(I) (1) and tin(II)-thallium(I) (2) complexes have been synthesized, isolated, and fully characterized including single-crystal X-ray diffraction analysis. When reacted with copper(I) sources, complex 2 grants access to a homotetrametallic copper(I) complex (4). Upon subsequent oxidation, 4 gives rise to the bimetallic copper(II) complex 5, in which the two copper(II) centers are connected via a bridging bromido ligand (CuII-μ-Br-CuII).

Oxo(corrolato)vanadium(iv) catalyzed epoxidation: oxo(peroxo)(corrolato)vanadium(v) is the true catalytic species

Oxo(corrolato)vanadium(iv) complexes are highly efficient oxidizers in the presence of H2O2 and KHCO3, and oxo(peroxo)(corrolato)vanadium(v) complexes are the catalytic intermediate.

Dimeric Corrole Analogs of Chlorophyll Special Pairs

Chlorophyll special pairs in photosynthetic reaction centers function as both exciton acceptors and primary electron donors. Although the macrocyclic natural pigments contain Mg(II), the central metal in most synthetic analogs is Zn(II). Here we report that insertion of either Al(III) or Ga(III) into an imidazole-substituted corrole affords an exceptionally robust photoactive dimer. Notably, attractive electronic interactions between dimer subunits are relatively strong, as documented by signature changes in NMR and electronic absorption spectra, as well as by cyclic voltammetry, where two well-separated reversible redox couples were observed. EPR spectra of one-electron oxidized dimers closely mimic those of native special pairs, and strong through-space interactions between corrole subunits inferred from spectroscopic and electrochemical data are further supported by crystal structure analyses (3 Å interplanar distances, 5 Å lateral shifts, and 6 Å metal to metal distances).

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.

Formation of monomeric Sn(ii) and Sn(iv) perfluoropinacolate complexes and their characterization by 119Sn Mössbauer and 119Sn NMR spectroscopies

The synthesis and characterization of a series of Sn(ii) and Sn(iv) complexes supported by the highly electron-withdrawing dianionic perfluoropinacolate (pin^F) ligand are reported herein. Three analogs of [Sn^IV(pin^F)₃]^2- with NEt₃H⁺ (1), K⁺ (2), and {K(18C6)}⁺ (3) counter cations and two analogs of [Sn^II(pin^F)₂]^2- with K⁺ (4) and {K(15C5)₂}⁺ (5) counter cations were prepared and characterized by standard analytical methods, single-crystal X-ray diffraction, and ¹¹⁹Sn Mössbauer and NMR spectroscopies. The six-coordinate Sn^IV(pin^F) complexes display ¹¹⁹Sn NMR resonances and ¹¹⁹Sn Mössbauer spectra similar to SnO₂ (cassiterite). In contrast, the four-coordinate Sn^II(pin^F) complexes, featuring a stereochemically-active lone pair, possess low ¹¹⁹Sn NMR chemical shifts and relatively high quadrupolar splitting. Furthermore, the Sn(ii) complexes are unreactive towards both Lewis bases (pyridine, NEt₃) and acids (BX₃, Et₃NH⁺). Calculations confirm that the Sn(ii) lone pair is localized within the 5s orbital and reveal that the Sn 5p_x LUMO is energetically inaccessible, which effectively abates reactivity.

Intercalation of manganese-mefenamic acid complex into double stranded of calf thymus DNA

The interaction of the [Mn(mef)₂(phen)H₂O] complex in which mef is mefenamic acid drug and phen is 1,10 phenanthrolin ligand with calf thymus DNA (ct-DNA) was studied by using different spectroscopic methods, molecular docking and viscometery. The competitive fluorescence and UV-Vis absorption spectroscopy indicated that the complex interacted with ctDNA via intercalating binding mode with the binding constant of 1.16 × 10⁴ Lmol^-1. The thermodynamic studies showed that the reaction between the complex and ctDNA is exothermic. Furthermore, the complex induced changes in DNA viscosity. Circular dichroism spectroscopy (CD) was employed to measure the conformational changes of ctDNA in the presence of the complex and verified intercalation binding mode. The molecular modeling results illustrated that the complex interacted via intercalation by relative binding energy of -28.45 kJ mol^-1.

Synthesis, characterization and photodynamic activity of Sn(iv) triarylcorroles with red-shifted Q bands

A tin(iv)corrole with meso-thien-2-yl rings has significantly red-shifted Q bands and is found to have favourable photodynamic therapy activity.

DNA-binding, photocleavage and anti-cancer activity of tin(IV) corrole

A new tin(IV) corrole, 5,10,15-tris(4-methoxycarbonylphenyl) corrole tin(IV) (1-Sn) was synthesized and characterized. The DNA binding, photocleavage and anti-cancer activity were studied and compared with its free-base. The interaction of 1-Sn and its free-base 1 with calf thymus DNA had been investigated by spectroscopic methods, viscosity measurements and molecular docking analysis. The results revealed that 1-Sn and 1 could interact with calf thymus DNA via an outside groove binding mode. Furthermore, although 1 displayed no photonuclease activity, 1-Sn exhibited good photonuclease activity as indicated by agarose gel electrophoresis, and superoxide anion might be the active intermediate for the DNA scission. Finally, 1 was nontoxic but 1-Sn displayed cytotoxicity towards A549 tumor cell lines.

Thermodynamic and reactivity studies of a tin corrole-cobalt porphyrin heterobimetallic complex

A heterobimetallic complex, (TPFC)Sn-Co(TAP) (TPFC = 5,10,15-tris(pentafluorophenyl)corrole, TAP = 5,10,15,20-tetrakis(p-methoxyphenyl)porphyrin), was synthesized. The complex featured a Sn-Co bond with a bond dissociation enthalpy (BDE) of 30.2 ± 0.9 kcal mol^-1 and a bond dissociation Gibbs free energy (BDFE) of 21.0 ± 0.2 kcal mol^-1, which underwent homolysis to produce the (TPFC)Sn radical and (TAP)Co^II under either heat or visible light irradiation. The novel tin radical (TPFC)Sn, being the first four-coordinate tin radical observed at room temperature, was studied spectroscopically and computationally. (TPFC)Sn-Co(TAP) promoted the oligomerization of aryl alkynes to give the insertion products (TPFC)Sn-(CH 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 C(Ar)) _n -Co(TAP) (n = 1, 2, or 3) as well as 1,3,5-triarylbenzenes. Mechanistic studies revealed a radical chain mechanism involving the (TPFC)Sn radical as the key intermediate.

Electronic Structure of Corrole Derivatives: Insights from Molecular Structures, Spectroscopy, Electrochemistry, and Quantum Chemical Calculations

Presented herein is a comprehensive account of the electronic structure of corrole derivatives. Our knowledge in this area derives from a broad range of methods, including UV-vis-NIR absorption and MCD spectroscopies, single-crystal X-ray structure determination, vibrational spectroscopy, NMR and EPR spectroscopies, electrochemistry, X-ray absorption spectroscopy, and quantum chemical calculations, the latter including both density functional theory and ab initio multiconfigurational methods. The review is organized according to the Periodic Table, describing free-base and main-group element corrole derivatives, then transition-metal corroles, and finally f-block element corroles. Like porphyrins, corrole derivatives with a redox-inactive coordinated atom follow the Gouterman four-orbital model. A key difference from porphyrins is the much wider prevalence of noninnocent electronic structures as well as full-fledged corrole^•2- radicals among corrole derivatives. The most common orbital pathways mediating ligand noninnocence in transition-metal corroles are the metal(d_z2)-corrole("a_2u") interaction (most commonly observed in Mn and Fe corroles) and the metal(d_x2-y2)-corrole(a_2u) interaction in coinage metal corroles. Less commonly encountered is the metal(d_π)-corrole("a_1u") interaction, a unique feature of formal d⁵ metallocorroles. Corrole derivatives exhibit a rich array of optical properties, including substituent-sensitive Soret maxima indicative of ligand noninnocence, strong fluorescence in the case of lighter main-group element complexes, and room-temperature near-IR phosphorescence in the case of several 5d metal complexes. The review concludes with an attempt at identifying gaps in our current knowledge and potential future directions of electronic-structural research on corrole derivatives.

Synthesis and reactivity of tantalum corrole complexes

Reaction of the free base corrole (Mes₂(p-OMePh)corrole)H₃ with tantalum trialkyl precursors TaMe₃Cl₂ and TaBn₃N^tBu resulted in the formation of the tantalum dichloride (1) and tantalum imido (4) corrole complexes via alkane elimination. The X-ray crystal structures of these two compounds have been determined and the structural parameters are discussed. The Ta centre of 1 was found to sit out of the plane of the corrole ring by 0.903 Å and is cis-ligated, similarly to what has been reported for group 4 porphyrin complexes. From complex 1 we synthesized the dimethyl derivative (2), the reactivity of which is compared to an analogous tantalum dimethyl porphyrin cation. The imido complex 4 reacted with triphenylmethanol and 4-methylbenzyl alcohol, resulting in different extents of protonation of the imido group.

Strategies for Corrole Functionalization

This review covers the functionalization reactions of meso-arylcorroles, both at the inner core, as well as the peripheral positions of the macrocycle. Experimental details for the synthesis of all known metallocorrole types and for the N-alkylation reactions are presented. Key peripheral functionalization reactions such as halogenation, formylation, carboxylation, nitration, sulfonation, and others are discussed in detail, particularly the nucleophilic aromatic substitution and the participation of corroles in cycloaddition reactions as 2π or 4π components (covering Diels-Alder and 1,3-dipolar cycloadditions). Other functionalizations of corroles include a large diversity of reactions, namely Wittig reactions, reactions with methylene active compounds, formation of amines, amides, and imines, and metal catalyzed reactions. At the final section, the reactions involving oxidation and ring expansion of the corrole macrocycle are described comprehensively.

Fighting Cancer with Corroles

Corroles are exceptionally promising platforms for the development of agents for simultaneous cancer-targeting imaging and therapy. Depending on the element chelated by the corrole, these theranostic agents may be tuned primarily for diagnostic or therapeutic function. Versatile synthetic methodologies allow for the preparation of amphipolar derivatives, which form stable noncovalent conjugates with targeting biomolecules. These conjugates can be engineered for imaging and targeting as well as therapeutic function within one theranostic assembly. In this review, we begin with a brief outline of corrole chemistry that has been uniquely useful in designing corrole-based anticancer agents. Then we turn attention to the early literature regarding corrole anticancer activity, which commenced one year after the first scalable synthesis was reported (1999-2000). In 2001, a major advance was made with the introduction of negatively charged corroles, as these molecules, being amphipolar, form stable conjugates with many proteins. More recently, both cellular uptake and intracellular trafficking of metallocorroles have been documented in experimental investigations employing advanced optical spectroscopic as well as magnetic resonance imaging techniques. Key results from work on both cellular and animal models are reviewed, with emphasis on those that have shed new light on the mechanisms associated with anticancer activity. In closing, we predict a very bright future for corrole anticancer research, as it is experiencing exponential growth, taking full advantage of recently developed imaging and therapeutic modalities.

Structural, electrochemical and spectroelectrochemical study on the geometric and electronic structures of [(corrolato)AuIII]n (n = 0, +1, −1) complexes

UV-vis-NIR/EPR spectroelectrochemical investigations on Au^III corroles display NIR electrochromism, the origins of which are all on corrole-centered processes.

NMR spectroscopy of the phenyl derivative of germanium(IV) 5,10,15-tritolylcorrole

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.

Stabilization of hexa-coordinated P(v) corroles by axial silyloxy groups

We report the stabilization of the hexa-coordination environment for P(v) corroles using alkyl/aryl substituted silyloxy groups as axial ligands. The P(v) corroles are highly fluorescent and highly stable under electrochemical conditions.

NIR-emissive iridium(iii) corrole complexes as efficient singlet oxygen sensitizers

The observed phosphorescence of the studied Ir(iii)corroles at ambient temperature appears at much longer wavelengths than the previously reported Ir(iii) porphyrin/corrole derivatives. Efficiencies of these compounds in the generation of singlet oxygen are also studied for the first time.

Uranium-mediated oxidative addition and reductive elimination

This Perspective article summarises the emerging research topic of uranium-mediated oxidative addition and reductive elimination.

A cytotoxic and cytostatic gold(iii) corrole

The bis-sulfonated Au(iii) corrole (1-Au) was found to be much more cytotoxic and cytostatic than its Ga(iii) analog 1-Ga, which might be attributed to the lower affinity of 1-Au to serum albumin.