Mariusz Tasior

Corrole−Fullerene Dyads: Formation of Long-Lived Charge-Separated States in Nonpolar Solvents

The first example of covalently linked free-base corrole-fullerene dyads is reported. In the newly synthesized dyads, the free-energy calculations performed by employing the redox and singlet excited-state energy in both polar and nonpolar solvents suggested the possibility of electron transfer from the excited singlet state of corrole to the fullerene entity. Accordingly, steady-state and time-resolved emission studies revealed efficient fluorescence quenching of the corrole entity in the dyads. Further studies involving femtosecond laser flash photolysis and nanosecond transient absorption studies confirmed electron transfer to be the quenching mechanism, in which the electron-transfer product, the fullerene anion radical, was able to be spectrally characterized. The rate of charge separation, kCS, was found to be on the order of 10(10)-10(11) s(-1), suggesting an efficient photoinduced electron-transfer process. Interestingly, the rate of charge recombination, kCR, was slower by 5 orders of magnitude in nonpolar solvents, cyclohexane and toluene, resulting in a radical ion-pair lasting for several microseconds. Careful analysis of the kinetic and thermodynamic data using the Marcus approach revealed that this novel feature is due to appropriately positioning the energy level of the charge-separated state below the triplet states of either of the donor and acceptor entities in both polar and nonpolar solvents, a feature that was not evident in donor-acceptor dyads constructed using symmetric tetrapyrroles as electron donors.

New on-bead near-infrared fluorophores and fluorescent sensor constructs.

The facile synthesis and photophysical characterization of new on-bead fluorophores and fluorescent sensors are described. The unique covalent immobilization strategy results in highly fluorescent beads with sharp emission profiles between 650 and 800 nm. Illustrative examples include imaging in an aqueous cellular environment and adaptation to include off/on sensing functionality, proven by a prototypical detection of gaseous HCl.

Parallel synthesis of meso-substituted corroles and meso-substituted [22]pentaphyrins(1.1.1.0.0) from diacyl-dipyrromethanes

A new method was devised for the synthesis of 1,9-diacyldipyrromethanes - crucial intermediates in the synthesis of meso-substituted corroles and porphyrins with different substituents. The diacylodipyrromethanes formation involves acylation of dipyrromethanes with salts made in situ from POCl3 and tertiary amides. This modified Vilsmeier approach gives higher yields and no concomitant formation of monoacyldipyrromethanes as compared with the Grignard route. Moreover, compounds possessing groups previously inaccessible (CN, NO2 etc.) can be synthesized. During optimization of the transformation of diacyldipyrromethanes into meso-substituted corroles it was found that if macrocyclization reaction mediated by DDQ is performed in the presence of large excess of pyrrole, meso-substituted [22]pentaphyrins(1.1.1.0.0) can be obtained in moderate yield. The currently described procedure constitutes a new method for the synthesis of these valuable porphyrinoids. Corroles possessing interesting, easy to transform, functional groups were obtained in 3-40% yield.

Extension of Pyrrolopyrrole π-System: Approach to Constructing Hexacyclic Nitrogen-Containing Aromatic Systems

A facile three-step approach to synthesizing quinoline-fused pyrrolopyrroles is reported. The crucial step in this synthesis is the condensation of 2-aminophenyl substituted pyrrolopyrroles with aromatic aldehydes. The resulting hexacyclic ladder-type dyes strongly absorb UV radiation and exhibit fluorescence at 450-510 nm. The presence of pyridine-type and pyrrole-type nitrogen atoms is important for the electronic properties of this almost planar heterocycle. These heteroatoms, along with the addition of moderate electron-withdrawing and electron-accepting substituents, provide a means for fine-tuning of the emission characteristics of the polycyclic conjugates.

Corroles bearing diverse coumarin units — synthesis and optical properties

Two strategies were shown to be efficient in the construction of corroles with appended coumarin units. Direct condensation of formyl-coumarins with dipyrromethanes leads to a diverse range of trans-A2B-corroles in moderate yields. We showed that the strategy consisting of synthesis of various hydroxycoumarins followed by nucleophilic aromatic substitution with pentafluorobenzaldehyde and subsequent condensation of the resulting coumarin-aldehyde with dipyrromethanes is the most general methodology for the preparation of such dyads. The second, more demanding but also more efficient approach is based on Sonogashira coupling of ethynylphenylcorroles with suitably functionalized bromocoumarins. A broad range of structurally diverse coumarins were employed with absorption ranging from 300 to 460 nm. Spectroscopic properties of all eight dyads studied suggest that the linker components are weakly electronically coupled.

Meso-substituted corroles bearing peripheral donor sites

Various pathways towards corroles bearing additional donor sites especially those with diazacrown units have been evaluated. Macrocyclic diamidation based on the reaction of diamines with diesters was found to be the key step in the overall synthetic scheme. This strategy was applied successfully to the synthesis of three compounds possessing macrocyclic diamide or diamine moieties. In addition, a meso-picolyl derivatized corrole was prepared. The new ligands were investigated with respect to the regioselectivity of transition metal insertion. Mononuclear corrolates of copper and cobalt are formed as the only isolable products, if simple copper and cobalt precursors and standard metalation protocols are applied. The results prove, that corroles can be used as selectively coordinating building blocks in multi-compartment ligand systems with peripheral crown ether and pyridyl functionalization.

Synthesis and Properties of Ladder-Type BN-Heteroacenes and Diazabenzoindoles Built on a Pyrrolopyrrole Scaffold

A simple, three-step synthesis of BN-heteroacenes and diazabenzoindoles based on the pyrrole[3,2-b]pyrrole scaffold has been developed. The incorporation of BN units has proven to be effective in modulating the electronic properties and molecular geometries of the π-conjugated backbone, creating a new type of heteroarenes. The unique planar structure and high rigidity of BN-compounds result in very high absorption coefficients and high fluorescence quantum yields, and, at the same time, very small Stokes shifts. A striking difference has been observed for a second type of derivatives: diazabenzoindoles, which remain virtually nonfluorescent, despite having a similar, rigid structure. The former class of heterocycles is characterized by a strong absorption around 400 nm and intense fluorescence observed in the 395-426 nm region, which results in very small Stokes shifts of less than 900 cm(-1).

Corrole–imide dyads — Synthesis and optical properties

Two rarely seen building blocks have been incorporated into light absorbing arrays: corroles and 2,3-naphthalimides. General synthetic strategy consisting in direct condensation of formyl substituted aromatic imides with dipyrranes led to diverse range of trans-A2B-corroles in acceptable yields. Spectroscopic properties of all five dyads studied suggest that regardless the imides structure, components are weakly electronically coupled. Positioning 2,3-naphthalimide unit partially above the corrole core leads to slight alteration of their optical properties. Dyads bearing blue-absorbing imide components display different behavior depending on their structure. In corrole linked with naphthalenyl-naphthalene-1,8-carboximide a 100% effective energy transfer reaction from the imide component to the corrole component occurred. On the contrary, in small, strongly polarized amino-cyano-phthalimide neither efficient energy-nor electron-transfer could be detected and excitation leads to fluorescence from both components.

Hydrogen Bonds Involving Cavity NH Protons Drives Supramolecular Oligomerization of Amido‐Corroles

trans-A2 B-Corroles with amide substituents at different positions versus the macrocyclic core have been synthesized. Their self-organizing properties have been comprehensively evaluated both in solid-state and in solution. The rigid arrangement of the amide functionality with the corrole ring led to the formation of strong intramolecular interactions and precluded intermolecular interactions. Replacement of sterically hindered C6 F5 substituents at positions 5 and 15 with smaller electron-withdrawing CO2 Me groups resulted in significant changes in the self-assembly pattern. With these substituents, tetramers formed in a crystalline state, in which one of the H-pyrrole subunits is out of the corrole plane. This allows the N-H group to form a hydrogen bond with a neighboring carbonyl group of the n-butyl amide fragment. DOSY NMR studies showed that amido-corroles bearing the OCH2 CONHnBu motif formed dimers in millimolar solutions in nonpolar solvents and the dimers existed in equilibrium with monomers. However, the corroles possessing meso-ester groups did not form dimers in polar tetrahydrofuran. Comprehensive optical studies allowed the absorption and emission features of the monomer corroles to be characterized in dilute solutions.