Engineering topics

Rong, Jie

Publications and source records attributed to Rong, Jie.

7 records

DOE OSTI2022

Balancing Panchromatic Absorption and Multistep Charge Separation in a Compact Molecular Architecture

A panchromatic triad and a charge-separation triad are joined in a crossbar architecture to capture solar energy. The panchromatic triad (T) is comprised of a central free-base porphyrin that is strongly coupled via direct ethyne linkages to two perylene-monoimides. Here, the charge-separation unit incorporates a free-base or zinc chlorin (C or ZnC) as a hole acceptor (or electron donor) and a perylene-diimide (PDI) as an electron acceptor, both attached to the porphyrin via diphenylethyne linkers. The free-base porphyrin is common to both light-harvesting and charge-separation motifs. The chlorin and PDI also function as ancillary light absorbers, complementing direct excitation of the panchromatic triad to produce the discrete lowest excited state of the array (T*). Attainment of full charge separation across the pentad entails two steps: (1) an initial excited-state hole/electron transfer process to oxidize the chlorin (and reduce the triad) or reduce the PDI (and oxidize the triad); and (2) subsequent ground-state electron/hole migration to produce oxidized chlorin and reduced PDI. Full charge separation for pentad ZnC-T-PDI to generate ZnC + -T-PDI¯ occurs with a quantum yield of ~30% and mean lifetime ~1 μs in dimethyl sulfoxide. For C-T-PDI, initial charge separation is followed by rapid charge recombination. The molecular designs and studies reported here reveal the challenges of balancing the demands for charge separation (linker length and composition, excited-state energies, redox potentials, and medium polarity) with the constraints for panchromatic absorption (strong electronic coupling of the porphyrin and two perylene-monoimide units) for integrated function in solar-energy conversion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Panchromatic Absorbers Tethered for Bioconjugation or Surface Attachment

The syntheses of two triads are reported. Each triad is composed of two perylene-monoimides linked to a porphyrin via an ethyne unit, which bridges the perylene 9-position and a porphyrin 5- or 15-position. Each triad also contains a single tether composed of an alkynoic acid or an isophthalate unit. Each triad provides panchromatic absorption (350–700 nm) with fluorescence emission in the near-infrared region (733 or 743 nm; fluorescence quantum yield ~0.2). The syntheses rely on the preparation of trans-AB-porphyrins bearing one site for tether attachment (A), an aryl group (B), and two open meso-positions. The AB-porphyrins were prepared by the condensation of a 1,9-diformyldipyrromethane and a dipyrromethane. The installation of the two perylene-monoimide groups was achieved upon the 5,15-dibromination of the porphyrin and the subsequent copper-free Sonogashira coupling, which was accomplished before or after the attachment of the tether. The syntheses provide relatively straightforward access to a panchromatic absorber for use in bioconjugation or surface-attachment processes.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2022

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. In this study, 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.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Meso bromination and derivatization of synthetic bacteriochlorins

Here, the ability to prepare and tailor synthetic analogues of native bacteriochlorophylls enables diverse applications. A de novo route entails dimerization of a dihydrodipyrrin-acetal to afford the corresponding 5-methoxy and/or 5-unsubstituted bacteriochlorin, wherein each pyrroline ring contains a gem-dimethyl group to ensure stability toward adventitious dehydrogenation. The presence of a 5-methoxy group facilitates bromination at the distal meso-(15-)position. While bromination of 5-unsubstituted bacteriochlorins typically affords a mixture of brominated products, here the presence of two substitution patterns (2,12-dicarboethoxy, 2,12-diacetyl) has been found to facilitate selective meso-bromination in the absence of the methoxy substituent. The introduction of a single meso-bromine atom in a bacteriochlorin opens opportunities for Pd-mediated derivatization, which include (1) preparation of four ethynylphenyl building blocks (and two benchmark bacteriochlorins) with long-wavelength absorption bands tuned across 725–757 nm, for use in preparation of multichromophore arrays; (2) installation of a bioconjugatable group to free base bacteriochlorins or a copper bacteriochlorin, the latter for possible use in photoacoustic imaging; and (3) installation of an S-acetylthio group for surface attachment. Altogether, 25 new bacteriochlorins are described including 5 meso-bromobacteriochlorin intermediates and 12 target bacteriochlorins.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Synthesis of bacteriochlorins bearing diverse β-substituents

Synthetic bacteriochlorins, analogues of native bacteriochlorophylls, provide absorption in the near-infrared spectral region and hence are valuable for fundamental studies in photochemistry and applications ranging from solar energy conversion to photomedicine. The full realization of such opportunities hinges on access to synthetically malleable bacteriochlorins. Here, two established routes that rely on self-condensation of a dihydrodipyrrin-acetal or dihydrodipyrrin-carboxaldehyde have been exploited to prepare 6 bacteriochlorins (2 new, 4 known in improved fashion). Each bacteriochlorin contains a gem-dimethyl group in the reduced, pyrroline ring to ensure stability toward adventitious dehydrogenation. These and related synthetic bacteriochlorins have been derivatized to tailor the perimeter of the macrocycle with diverse groups, affording 9 additional new bacteriochlorins and 4 known bacteriochlorins. By direct installation and/or derivatization, the scope of attached entities in this collection includes alkyl, amino, aryl, bromo, carboethoxy, oxo, phenylethynyl, and pyridyl. Furthermore, the bacteriochlorins are suited for surface attachment, bioconjugation, water-solubilization, vibrational studies, and elaboration into multichromophore arrays. Altogether the synthesis of 25 new compounds (11 bacteriochlorins, 14 precursors) is described.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Phenylene-linked tetrapyrrole arrays containing free base and diverse metal chelate forms – Versatile synthetic architectures for catalysis and artificial photosynthesis

Tetrapyrrole macrocycles are central to photosynthesis yet a single macrocycle does not carry out photosynthesis; rather, assemblies of tetrapyrrole macrocycles work in concert in antenna complexes, reaction centers, and electron-transport chains to harvest sunlight, funnel excited-state energy and separate charge for biological use. A longstanding theme in artificial photosynthesis has been to construct covalently linked “arrays” of metalated and free base tetrapyrrole macrocycles for fundamental studies of such processes, which entail excited-state and ground-state interactions. Among linkers in arrays chemistry, the 1,2-, 1,3-, or 1,4-disubstituted phenylene unit has proved very attractive owing to the resulting short distance, defined architecture, and appropriate extent of electronic coupling of adjacent macrocycles to give rapid electron and/or energy transfer while largely retaining desired spectral features. Eight distinct strategies to construct phenylene-linked tetrapyrrole arrays are identified in a review with comprehensive coverage since inception in the early 1970s through mid-year 2021. The arrays predominantly incorporate porphyrins with very few chlorins and bacteriochlorins, reflecting historic availability of synthetic methods for macrocycle formation. Of the eight strategies, only two appear applicable to (bacterio)chlorins. While studies in artificial photosynthesis have largely fueled this field, applications in catalysis have also been examined. Altogether >400 arrays are covered. The review delves into synthesis and molecular design, sketches photophysical properties, and suggests unrealized opportunities in arrays chemistry.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Electronic Structure and Excited-State Dynamics of Rylene–Tetrapyrrole Panchromatic Absorbers

Panchromatic absorbers have potential applications in molecular-based energy-conversion schemes. A prior porphyrin–perylene dyad (P-PMI, where “MI” denotes monoimide) coupled via an ethyne linker exhibits panchromatic absorption (350–700 nm) and a tetrapyrrole-like lowest singlet excited state with a relatively long singlet excited-state lifetime (τ S ) and increased fluorescence quantum yield (Φ f ) versus the parent porphyrin. To explore the extension of panchromaticity to longer wavelengths, three arrays have been synthesized: a chlorin–terrylene dyad (C-TMI), a bacteriochlorin–terrylene dyad (B-TMI), and a perylene–porphyrin–terrylene triad (PMI-P-TMI), where the terrylene, a π-extended homologue of perylene, is attached via an ethyne linker. Characterization of the spectra (absorption and fluorescence), excited-state properties (lifetime, yields, and rate constants of decay pathways), and molecular-orbital characteristics reveals unexpected subtleties. The wavelength of the red-region absorption band increases in the order C-TMI (705 nm) < PMI-P-TMI (749 nm) < B-TMI (774 nm), yet each array exhibits diminished Φ f and shortened τ S values. The PMI-P-TMI triad in toluene exhibits Φ f = 0.038 and τ S = 139 ps versus the all-perylene triad (PMI-P-PMI) for which Φ f = 0.26 and τ S = 2000 ps. The results highlight design constraints for auxiliary pigments with tetrapyrroles to achieve panchromatic absorption with retention of viable excited-state properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗