Efficient Electron Transfer Driven by Excited-State Structural Relaxation in Corrole-Perylenedimiide Dyad

A sterically encumbered trans-A2B-corrole possessing a perylenediimide (PDI) scaffold in close proximity to the macrocycle has been synthesized via a straightforward route. Electronic communication as probed via steady-state absorption or cyclic voltammetry is weak in the ground state, in spite of the corrole ring and PDI being bridged by an o-phenylene unit. The TDDFT excited-state geometry optimization suggests after excitation the interchromophoric distance is markedly reduced, thus enhancing the through-space electronic coupling between the corrole and the PDI. This is corroborated by the strong deviation of the emission spectrum originating from both PDI and corrole in the dyad. Selective excitation of both donor and acceptor units triggers efficient sub-picosecond electron transfer and hole transfer, respectively, followed by fast charge recombination. In comparison to previously studied corrole-PDI dyads, both charge separation and charge recombination occur faster, because of the structural relaxation in the excited state.

De Novo Access to BODIPY C-Glycosides as Linker-Free Nonsymmetrical BODIPY-Carbohydrate Conjugates

Recent years have witnessed an increasing interest in the synthesis and study of BODIPY-glycoconjugates. Most of the described synthetic methods toward these derivatives involve postfunctional modifications of the BODIPY core followed by the covalent attachment of the fluorophore and the carbohydrate through a "connector". Conversely, few de novo synthetic approaches to linker-free carbohydrate-BODIPY hybrids have been described. We have developed a reliable modular, de novo, synthetic strategy to linker-free BODIPY-sugar derivatives using the condensation of pyrrole C-glycosides with a pyrrole-carbaldehyde derivative mediated by POCl3. This methodology allows labeling of carbohydrate biomolecules with fluorescent-enough BODIPYs within the biological window, stable in aqueous media, and able to display singlet oxygen generation.

Milestones in corrole chemistry: historical ligand syntheses and post-functionalization

Corroles are synthetic porphyrin analogs that contain one meso carbon atom lesser and bear a trianionic N4 metal-chelating core. They require in-depth preparative chemistry, demonstrate unique coordination chemistry and have impressive and diverse physical properties, and these are commonly compared to their respective porphyrins. The corrole's macrocyclic system is inherently electron rich and chelates metal ions in a more compact, less symmetric tetranitrogen cavity compared to that of porphyrins. Herein, we cover the highlights of the corrole research through the decades by first reviewing, in a chronological sense, multi-step syntheses; some routes have since been discontinued. This is followed by describing post-functionalization of already formed corroles via reactions performed on either the macrocycle's periphery or the inner nitrogen atoms or on the existing substituents. We do also mention milestones in literature reviewing, publication of encyclopedias, and the creation of professional organizations and conferences (ICPP) which make up the corrole/porphyrin research landscape. Also highlighted are still existing challenges and future perspectives.

Simple Dipyrrin Analogues of Prodigiosin for Use as Colistin Adjuvants

Multidrug resistant (MDR) bacteria are an increasing public health problem. One promising alternative to the development of new antibiotics is the use of antibiotic adjuvants, which would allow the continued use of FDA-approved antibiotics that have been rendered ineffective due to resistance. Herein, we report a series of dipyrrins and pyrrole derivatives designed as analogues of prodigiosin and obatoclax, several of which potentiate the activity of colistin against Klebsiella pneumoniae, with lead compounds also potentiating colistin against Acinetobacter baumannii and Pseudomonas aeruginosa.

Synthesis, Reactivity, and Properties of a Class of π-Extended BODIPY Derivatives

A new family of π-extended BODIPY derivatives were obtained through the condensation of aldehyde and pyrrole in aqueous solution in the presence of HCl. The new rigid π-framework extends beyond the dipyrromethene unit, which is significantly different from classical BODIPYs in the electronic configuration. Both π-extended BODIPYs displayed intense absorption and moderate emission with maxima around 565 and 620 nm, respectively, and showed interesting reactivity toward various nucleophiles. Moreover, these π-extended BODIPYs were developed as fluorescent probes for rapid and selective detection of GSH and were successfully applied for live-cell imaging.

Synthesis of 7,12-bis(4-(di(1H-pyrrol-2-yl)methyl)phenyl)benzo[k]fluoranthene from a new dialdehyde as a novel fluorometric bis-Dipyrromethane derivative

Dipyrromethanes are useful mediator structures which can be used as a part of other molecules such as bis-porphyrins and their derivations. Various methods have been developed for their synthesis. This study presents the synthesis of a new bis-dipyrromethane, 7,12-bis(4-(di(1H-pyrrol-2-yl)methyl)phenyl)benzo[k]fluoranthene, using the Lewis acid catalyzed reaction between a new dialdehyde and pyrrole at room temperature. The UV spectroscopic and fluorometric properties of the final product and precursors were determined. The newly synthesized product with desirable UV spectroscopic and fluorometric properties has the potential to be applied as a part of bis-porphyrins or it can be used for other purposes in future studies.

Physicochemical and computational insight of 19F NMR and emission properties of meso-(o-aryl)-BODIPYs

Magnetic differentiation of the fluorine atoms was observed. The trends were explained in terms of their rotational energy barriers, group electronegativity and σ-Hammett.

Use of the Nascent Isocyclic Ring to Anchor Assembly of the Full Skeleton of Model Chlorophylls

The chlorophyll skeleton contains a chlorin macrocycle and an annulated fifth (or isocyclic) ring bearing 13¹-oxo and 13²-carbomethoxy substituents. The isocyclic ring has traditionally been constructed by annulation of an intact tetrapyrrole macrocycle. Here, a complementary route employs reaction of a gem-dimethyl-substituted dihydrodipyrrin-carboxaldehyde (AD half) and a dipyrromethane bearing a 3-methoxy-1,3-dioxopropyl group (BC half). A McMurry-like reaction of a 2-(2-nitro-5-oxohexyl)pyrrole was employed to construct the second pyrrole ring in one of three BC halves, whereas the other two were prepared by known routes. An AD half and a BC half were joined by Knoevenagel condensation at room temperature, affording the AD,BC-substituted 2-methoxycarbonyl-2-propenone. The subsequent reaction of three AD, BC-propenones (mixture of Z,E-isomers) in CH₃CN containing InCl₃ and In(OTf)₃ at 80 °C afforded the chlorophyll skeleton as the chloroindium(III) chelate; the reaction proceeds via Nazarov cyclization (to form the isocyclic ring), S_EAr (to construct the macrocycle), and 2e^-,2H⁺ oxidation (to give the aromatic chromophore). The absorption spectra of the complexes closely resemble that of chlorophyll a. The present work exploits the nascent isocyclic ring as an anchor for directed assembly of the AD and BC halves, forming both the chlorin macrocycle and the isocyclic ring in a single-flask transformation.

Current Advances in the Synthesis of Valuable Dipyrromethane Scaffolds: Classic and New Methods

This review presents the most recent developments on the synthesis of dipyrromethanes, covering classical synthetic strategies, using acid catalyzed condensation of pyrroles and aldehydes or ketones, and recent breakthroughs which allow the synthesis of these type of heterocycles with new substitution patterns.

Chasing BODIPY: Enhancement of Luminescence in Homoleptic Bis(dipyrrinato) ZnII Complexes Utilizing Symmetric and Unsymmetrical Dipyrrins

Dipyrromethene metal complexes are fascinating molecules that have applications as light-harvesting systems, luminophores, and laser dyes. Recently, it has been shown that structurally rigid bis(dipyrrinato) zinc(II) complexes exhibit high fluorescence with comparable quantum yields to those of boron dipyrromethenes or BODIPYs. Herein, eight new bis(dipyrrinato) Zn^II complexes, obtained from symmetric and unsymmetrical functionalization of the dipyrromethene structure through a Knoevenagel reaction, are reported. It was possible not only to vary the maximum visible absorption from 490 to 630 nm, but also to enhance the emission quantum yield up to 66 %, which is extraordinarily high for homoleptic bis(dipyrrinato) zinc complexes. These results pave the way for designing highly luminescent bis(dipyrrinato) zinc complexes.

Phosphorescent rhenium-dipyrrinates: efficient photosensitizers for singlet oxygen generation

A series of rhenium(i) dipyrrinato complexes (Re1–Re8) have been prepared and characterized; their crystal structures, phosphorescence and singlet oxygen generation studies are reported.

New types of Cu and Ag clusters supported by the pyrrole-based NNN-pincer type ligand

While the neutral ligand 2,5-bis(3,5-dimethylpyrazolylmethyl)pyrrole gives the dihalide ion bridged binuclear and coordination polymers, its anionic form affords a new type of tetranuclear ‘hourglass’ shaped copper(i) and triangular silver(i) clusters owing to its increased denticity.

C–H oxidation and chelation of a dipyrromethane mediated rapid colorimetric naked-eye Cu(ii) chemosensor

Selective C–H oxidation and chelation of DPMs mediated by copper is demonstrated and utilized in the development of a rapid colorimetric naked-eye Cu(ii) chemosensor.

Synthesis of Corroles and Their Heteroanalogs

Corroles have come a long way from being a curiosity to being a mainstream research topic. They are now regularly synthesized in numerous research laboratories worldwide with diverse specific aims in mind. In this review we present a comprehensive description of corroles' synthesis, developed both before and after 1999. To aid the investigator in developing synthetic strategies, some of the sections culminate in tables containing comparisons of various methodologies leading to meso-substituted corroles. The remaining challenges are delineated. In the second part of this review, we also describe the syntheses of isocorroles and heteroanalogs of corroles such as triazacorroles (corrolazines), 10-heterocorroles, 21-heterocorroles, 22-heterocorroles, N-confused corroles, as well as norcorroles. The review is complemented with a short outlook.

Nucleophilic Aromatic Substitution on Pentafluorophenyl-Substituted Dipyrranes and Tetrapyrroles as a Route to Multifunctionalized Chromophores for Potential Application in Photodynamic Therapy

The application of porphyrinoids in biomedical fields, such as photodynamic therapy (PDT), requires the introduction of functional groups to tune their solubility for the biological environment and to allow a coupling to other active moieties or carrier systems. A valuable motif in this regard is the pentafluorophenyl (PFP) substituent, which can easily undergo a regiospecific nucleophilic replacement (S_N Ar) of its para-fluorine atom by a number of nucleophiles. Here, it is shown that, instead of amino-substitution on the final porphyrinoid or BODIPY (boron dipyrromethene), the precursor 5-(PFP)-dipyrrane can be modified with amines (or alcohols). These dipyrranes were transformed into amino-substituted BODIPYs. Condensation of these dipyrranes with aldehydes gave access to trans-A₂ B₂ -porphyrins and trans-A₂ B-corroles. By using pentafluorobenzaldehyde, it was possible to introduce another para-fluorine atom, which enabled the synthesis of multifunctionalized tetrapyrroles. Furthermore, alkoxy- and amino-substituted dipyrranes were applied to the synthesis of A₃ B₃ -hexaphyrins. The polar porphyrins that were prepared by using this method exhibited in vitro PDT activity against several tumor cell lines.

An easily accessible and recyclable copper nanoparticle catalyst for the solvent-free synthesis of dipyrromethanes and aromatic amines

A facile method to prepare a reusable copper nanocatalyst is reported.

Green synthesis of dipyrromethanes in aqueous media catalyzed by SO3H-functionalized ionic liquid

A mild, efficient and metal-free method was described for the green synthesis of dipyrromethanes from aldehydes and unsubstituted pyrrole catalyzed by SO₃H-functionalized ionic liquids (SO₃H-ILs) in aqueous media at room temperature.

Hydrophilic bioconjugatable trans-AB-porphyrins and peptide conjugates

Porphyrins bearing a single bioconjugatable group and a single water-solubilization motif in a trans-AB-architecture (with no other substituents) provide a compact design of value for studies in diverse disciplines. Established synthetic methods have been employed to prepare four new free base porphyrins and one Mn ( III ) chelate. The hydrophilic motif includes 4-N-methylpyridinium, 2,4,6-tris(carboxymethoxy)phenyl, 2,6-bis(phosphonomethoxy)phenyl, and carboxy; the bioconjugatable unit includes carboxy, maleimido, and N-hydroxysuccinimido (NHS) ester. Bioconjugation experiments with a protected porphyrin-diphosphate or unprotected porphyrin-diphosphonate were examined in organic solution or water, respectively. Both approaches were employed to conjugate to the ε-amino group of Lys11 in AcKPV- NH 2, a tripeptide fragment [ Ac -α-MSH(11-13)- NH 2] of melanocyte stimulating hormone, yielding porphyrin-peptide conjugates.

New meso-substituted corroles possessing pentafluorophenyl groups – synthesis and spectroscopic characterization

In this paper, the synthesis and spectroscopic characterization of new free-base corroles substituted with different peripheral groups are reported.

Synthesis and structural characterization of silver(i), copper(i) coordination polymers and a helicate palladium(ii) complex of dipyrrolylmethane-based dipyrazole ligands: the effect of meso substituents on structural formation

A striking difference in the structures of silver complexes was observed because of the different substituents at the meso carbon atom of the dipyrrolylmethane-based ligand.

Soluble meso-tetrakis(arylethynyl)porphyrins — synthesis and optical properties

Trans- A 2 B 2-tetrakis(arylethynyl)porphyrins with suitable solubility in CH 2 Cl 2, CHCl 3, EtOAc , acetone and toluene have been obtained for the first time. Among two possible strategies the one comprising the synthesis of 5,15-dibromo-10,20-bis[(isopropylsilyl)ethynyl]porphyrin proved to be more efficient. The pathway towards densely substituted arylacetylenes has been optimized. The use of previously identified 3,4,5-trialkoxyaryl substituent was crucial for achieving the reasonable solubility. The optical properties of meso-substituted tetrakis(arylethynyl)porphyrins were studied showing that strong polarization imparted by direct conjugation of all four substituents with porphyrin core resulted not only in strong absorption of red light but also in a relatively long triplet lifetime. Meso-tetrakis(arylethynyl)porphyrins have a significantly longer lifetime of T1 state than bis(arylethynyl)porphyrins and in their case all the states are mixtures of transitions between the HOMO-1, HOMO and LUMO, LUMO+1 MOs. We show that the presence of two additional arylethynyl substituents at meso-positions enhance the maximum two-photon absorption cross-section of trans- A 2 B 2-tetrakis(arylethynyl)porphyrins by more than one order of magnitude. Maximum values as high as σ2 = 500 GM at 950 nm result from realization of suitable conditions for effective resonance enhancement along with a lowering of the energy and intensification of the two-photon allowed transitions in the Soret region.