Research

Jump to: Review

11 pages, 3208 KiB

Open AccessCommunication

Complexity-Building ESIPT-Assisted Synthesis of Fused Polyheterocyclic Sulfonamides

by Srinivas Beduru and Andrei G. Kutateladze

Molecules 2023, 28(18), 6549; https://doi.org/10.3390/molecules28186549 - 10 Sep 2023

Viewed by 656

Excited State Intramolecular Proton Transfer (ESIPT), originally discovered and explored in depth in a number of extensive photophysical studies, is more recently rediscovered as a powerful synthetic tool, offering rapid access to complex polyheterocycles. In our prior work we have employed ESIPT in [...] Read more.

Excited State Intramolecular Proton Transfer (ESIPT), originally discovered and explored in depth in a number of extensive photophysical studies, is more recently rediscovered as a powerful synthetic tool, offering rapid access to complex polyheterocycles. In our prior work we have employed ESIPT in aromatic o-keto amines and amides, leading to diverse primary photoproducts—complex quinolinols or azacanes possessing a fused lactam moiety—which could additionally be modified in short, high-yielding postphotochemical reactions to further grow complexity of the heterocyclic core scaffold and/or to decorate it with additional functional groups. Given that sulfonamides are generally known as privileged substructures, in this study we pursued two goals: (i) To explore whether sulfonamides could behave as proton donors in the context of ESIPT-initiated photoinduced reactions; (ii) To assess the scope of subsequent complexity-building photochemical and postphotochemical steps, which give access to polyheterocyclic molecular cores with fused cyclic sulfonamide moieties. In this work we show that this is indeed the case. Simple sulfonamide-containing photoprecursors produced the sought-after heterocyclic products in experimentally simple photochemical reactions accompanied by significant step-normalized complexity increases as corroborated by the Böttcher complexity scores. Full article

(This article belongs to the Special Issue Chemical Insights in Photofunctional Organic Compounds—a Themed Issue Dedicated to Professor Vaidhyanathan Ramamurthy)

► Show Figures

Scheme 1

18 pages, 8166 KiB

Open AccessArticle

Non-Covalent Assembly of Multiple Fluorophores in Edible Protein/Lipid Hydrogels for Applications in Multi-Step Light Harvesting and White-Light Emission

by Jingwen Ding and Challa V. Kumar

Molecules 2023, 28(16), 6028; https://doi.org/10.3390/molecules28166028 - 12 Aug 2023

Viewed by 694

Abstract

The design and production of biodegradable and sustainable non-toxic materials for solar-energy harvesting and conversion is a significant challenge. Here, our goal was to report the preparation of novel protein/lipid hydrogels and demonstrate their utility in two orthogonal fundamental studies—light harvesting and white-light [...] Read more.

The design and production of biodegradable and sustainable non-toxic materials for solar-energy harvesting and conversion is a significant challenge. Here, our goal was to report the preparation of novel protein/lipid hydrogels and demonstrate their utility in two orthogonal fundamental studies—light harvesting and white-light emission. Our hydrogels contained up to 90% water, while also being self-standing and injectable with a syringe. In one application, we loaded these hydrogels with suitable organic donor-acceptor dyes and demonstrated the energy-transfer cascade among four different dyes, with the most red-emitting dye as the energy destination. We hypothesized that the dyes were embedded in the protein/lipid phase away from the water pools as monomeric entities and that the excitation of any of the four dyes resulted in intense emission from the lowest-energy acceptor. In contrast to the energy-transfer cascade, we demonstrate the use of these gels to form a white-light-emitting hydrogel dye assembly, in which excitation migration is severely constrained. By restricting the dye-to-dye energy transfer, the blue, green, and red dyes emit at their respective wavelengths, thereby producing the composite white-light emission. The CIE color coordinates of the emission were 0.336 and 0.339—nearly pure white-light emission. Thus, two related studies with opposite requirements could be accommodated in the same hydrogel, which was made from edible ingredients by a simple method. These gels are biodegradable when released into the environment, sustainable, and may be of interest for energy applications. Full article

(This article belongs to the Special Issue Chemical Insights in Photofunctional Organic Compounds—a Themed Issue Dedicated to Professor Vaidhyanathan Ramamurthy)

► Show Figures

Graphical abstract

15 pages, 5166 KiB

Open AccessArticle

Photochemical Uncaging of Aldehydes and Ketones via Photocyclization/Fragmentation Cascades of Enyne Alcohols: An Unusual Application for a Cycloaromatization Process

by Adam Campbell, Nikolas R. Dos Santos and Igor Alabugin

Molecules 2023, 28(15), 5704; https://doi.org/10.3390/molecules28155704 - 28 Jul 2023

Viewed by 924

Abstract

We utilized a cycloaromatization reaction driven by relief of excited state antiaromaticity to photouncage aldehydes and ketones. We developed several synthetic routes towards the synthesis of photocaged carbonyls as allylically substituted 3-(2-(arylethynyl)phenyl)prop-2-en-1-ols. A library of photocaged aryl aldehydes and ketones containing donors and [...] Read more.

We utilized a cycloaromatization reaction driven by relief of excited state antiaromaticity to photouncage aldehydes and ketones. We developed several synthetic routes towards the synthesis of photocaged carbonyls as allylically substituted 3-(2-(arylethynyl)phenyl)prop-2-en-1-ols. A library of photocaged aryl aldehydes and ketones containing donors and acceptors, as well as several photocaged fragrance aldehydes and the steroid 5α-cholestan- 3 -one, were synthesized and demonstrated photouncaging in good to excellent yields. Full article

(This article belongs to the Special Issue Chemical Insights in Photofunctional Organic Compounds—a Themed Issue Dedicated to Professor Vaidhyanathan Ramamurthy)

► Show Figures

Figure 1

13 pages, 2759 KiB

Open AccessArticle

Influence of Al₂O₃ Overlayers on Intermolecular Interactions between Metal Oxide Bound Molecules

by Erica S. Knorr, Cody T. Basquill, Isabella A. Bertini, Ashley Arcidiacono, Drake Beery, Jonathan P. Wheeler, J. S. Raaj Vellore Winfred, Geoffrey F. Strouse and Kenneth Hanson

Molecules 2023, 28(12), 4835; https://doi.org/10.3390/molecules28124835 - 17 Jun 2023

Viewed by 1783

Abstract

Intermolecular interactions on inorganic substrates can have a critical impact on the electrochemical and photophysical properties of the materials and subsequent performance in hybrid electronics. Critical to the intentional formation or inhibition of these processes is controlling interactions between molecules on a surface. [...] Read more.

Intermolecular interactions on inorganic substrates can have a critical impact on the electrochemical and photophysical properties of the materials and subsequent performance in hybrid electronics. Critical to the intentional formation or inhibition of these processes is controlling interactions between molecules on a surface. In this report, we investigated the impact of surface loading and atomic-layer-deposited Al₂O₃ overlayers on the intermolecular interactions of a ZrO₂-bound anthracene derivative as probed by the photophysical properties of the interface. While surface loading density had no impact on the absorption spectra of the films, there was an increase in excimer features with surface loading as observed by both emission and transient absorption. The addition of ALD overlayers of Al₂O₃ resulted in a decrease in excimer formation, but the emission and transient absorption spectra were still dominated by excimer features. These results suggest that ALD may provide a post-surface loading means of influencing such intermolecular interactions. Full article

(This article belongs to the Special Issue Chemical Insights in Photofunctional Organic Compounds—a Themed Issue Dedicated to Professor Vaidhyanathan Ramamurthy)

► Show Figures

Graphical abstract

15 pages, 5937 KiB

Open AccessArticle

Facile Scale-Up of the Flow Synthesis of Silver Nanostructures Based on Norrish Type I Photoinitiators

by Mahzad Yaghmaei, Connor R. Bourgonje and Juan C. Scaiano

Molecules 2023, 28(11), 4445; https://doi.org/10.3390/molecules28114445 - 30 May 2023

Cited by 1 | Viewed by 1171

Abstract

Silver nanoparticles have become one of the most commercially and industrially relevant nanomaterials of the 21st century, owing to their potent antibacterial properties, as well as their useful catalytic and optical properties. Although many methods have been explored to produce AgNPs, we favor [...] Read more.

Silver nanoparticles have become one of the most commercially and industrially relevant nanomaterials of the 21st century, owing to their potent antibacterial properties, as well as their useful catalytic and optical properties. Although many methods have been explored to produce AgNPs, we favor the photochemical approach using photoinitiators to produce AgNPs, owing to the high degree of control over reaction conditions, and the generation of so-called AgNP ‘seeds’ that can be used as-is, or as precursors for other silver nanostructures. In this work, we explore the scale-up of AgNP synthesis using flow chemistry and assess the usefulness of a range of industrial Norrish Type 1 photoinitiators in terms of flow compatibility and reaction time, as well as the resulting plasmonic absorption and morphologies. We establish that while all the photoinitiators used were able to generate AgNPs in a mixed aqueous/alcohol system, photoinitiators that generate ketyl radicals showed the greatest promise in terms of reaction times, while also showing greater flow compatibility compared to photoinitiators that generate 𝛼-aminoalkyl and α-hydroxybenzyl radicals. These findings help to establish a guideline for adapting photochemical AgNP syntheses to flow systems, helping to improve the scalability of the method in one of the largest industries in nanomaterial chemistry. Full article

(This article belongs to the Special Issue Chemical Insights in Photofunctional Organic Compounds—a Themed Issue Dedicated to Professor Vaidhyanathan Ramamurthy)

► Show Figures

Graphical abstract

13 pages, 2490 KiB

Open AccessArticle

Optical Window to Polarity of Electrolyte Solutions

by Omar O’Mari and Valentine I. Vullev

Molecules 2023, 28(11), 4360; https://doi.org/10.3390/molecules28114360 - 26 May 2023

Cited by 2 | Viewed by 849

Abstract

Medium polarity plays a crucial role in charge-transfer processes and electrochemistry. The added supporting electrolyte in electrochemical setups, essential for attaining the needed electrical conductivity, sets challenges for estimating medium polarity. Herein, we resort to Lippert–Mataga–Ooshika (LMO) formalism for estimating the Onsager polarity [...] Read more.

Medium polarity plays a crucial role in charge-transfer processes and electrochemistry. The added supporting electrolyte in electrochemical setups, essential for attaining the needed electrical conductivity, sets challenges for estimating medium polarity. Herein, we resort to Lippert–Mataga–Ooshika (LMO) formalism for estimating the Onsager polarity of electrolyte organic solutions pertinent to electrochemical analysis. An amine derivative of 1,8-naphthalimide proves to be an appropriate photoprobe for LMO analysis. An increase in electrolyte concentration enhances the polarity of the solutions. This effect becomes especially pronounced for low-polarity solvents. Adding 100 mM tetrabutylammonium hexafluorophosphate to chloroform results in solution polarity exceeding that of neat dichloromethane and 1,2-dichloroethane. Conversely, the observed polarity enhancement that emerges upon the same electrolyte addition to solvents such as acetonitrile and N,N-dimethylformamide is hardly as dramatic. Measured refractive indices provide a means for converting Onsager to Born polarity, which is essential for analyzing medium effects on electrochemical trends. This study demonstrates a robust optical means, encompassing steady-state spectroscopy and refractometry, for characterizing solution properties important for charge-transfer science and electrochemistry. Full article

(This article belongs to the Special Issue Chemical Insights in Photofunctional Organic Compounds—a Themed Issue Dedicated to Professor Vaidhyanathan Ramamurthy)

► Show Figures

Figure 1

13 pages, 2670 KiB

Open AccessArticle

Spectroscopic Insights of an Emissive Complex between 4′-N,N-Diethylaminoflavonol in Octa-Acid Deep-Cavity Cavitand and Rhodamine 6G

by Fabiano da Silveira Santos, Elamparuthi Ramasamy, Lilian Camargo da Luz, Vaidhyanathan Ramamurthy and Fabiano Severo Rodembusch

Molecules 2023, 28(11), 4260; https://doi.org/10.3390/molecules28114260 - 23 May 2023

Viewed by 992

Abstract

Excited-state chemistry relies on the communication between molecules, making it a crucial aspect of the field. One important question that arises is whether intermolecular communication and its rate can be modified when a molecule is confined. To explore the interaction in such systems, [...] Read more.

Excited-state chemistry relies on the communication between molecules, making it a crucial aspect of the field. One important question that arises is whether intermolecular communication and its rate can be modified when a molecule is confined. To explore the interaction in such systems, we investigated the ground and excited states of 4′-N,N-diethylaminoflavonol (DEA3HF) in an octa acid-based (OA) confined medium and in ethanolic solution, both in the presence of Rhodamine 6G (R6G). Despite the observed spectral overlap between the flavonol emission and the R6G absorption, as well as the fluorescence quenching of the flavonol in the presence of R6G, the almost constant fluorescence lifetime at different amounts of R6G discards the presence of FRET in the studied systems. Steady-state and time-resolved fluorescence indicate the formation of an emissive complex between the proton transfer dye encapsulated within water-soluble supramolecular host octa acid (DEA3HF@(OA)₂) and R6G. A similar result was observed between DEA3HF:R6G in ethanolic solution. The respective Stern–Volmer plots corroborate with these observations, suggesting a static quenching mechanism for both systems. Full article

(This article belongs to the Special Issue Chemical Insights in Photofunctional Organic Compounds—a Themed Issue Dedicated to Professor Vaidhyanathan Ramamurthy)

► Show Figures

Figure 1

12 pages, 5504 KiB

Open AccessArticle

Phosphates Induced H-Type or J-Type Aggregation of Cationic Porphyrins with Varied Side Chains

by Zhiliang Li, Charles J. Zeman IV, Silvano Valandro, Jose Paolo O. Bantang and Kirk S. Schanze

Molecules 2023, 28(10), 4115; https://doi.org/10.3390/molecules28104115 - 16 May 2023

Cited by 1 | Viewed by 1617

Abstract

Non-covalent interactions have been extensively used to fabricate nanoscale architectures in supramolecular chemistry. However, the biomimetic self-assembly of diverse nanostructures in aqueous solution with reversibility induced by different important biomolecules remains a challenge. Here, we report the synthesis and aqueous self-assembly of two [...] Read more.

Non-covalent interactions have been extensively used to fabricate nanoscale architectures in supramolecular chemistry. However, the biomimetic self-assembly of diverse nanostructures in aqueous solution with reversibility induced by different important biomolecules remains a challenge. Here, we report the synthesis and aqueous self-assembly of two chiral cationic porphyrins substituted with different types of side chains (branched or linear). Helical H-aggregates are induced by pyrophosphate (PPi) as indicated by circular dichroism (CD) measurement, while J-aggregates are formed with adenosine triphosphate (ATP) for the two porphyrins. By modifying the peripheral side chains from linear to a branched structure, more pronounced H- or J-type aggregation was promoted through the interactions between cationic porphyrins and the biological phosphate ions. Moreover, the phosphate-induced self-assembly of the cationic porphyrins is reversible in the presence of the enzyme alkaline phosphatase (ALP) and repeated addition of phosphates. Full article

(This article belongs to the Special Issue Chemical Insights in Photofunctional Organic Compounds—a Themed Issue Dedicated to Professor Vaidhyanathan Ramamurthy)

► Show Figures

Figure 1

18 pages, 5178 KiB

Open AccessArticle

Photochemistry and Photophysics of Cholesta-5,7,9(11)-trien-3β-ol in Ethanol

by Jack Saltiel, Sumesh B. Krishnan, Shipra Gupta, Anjan Chakraborty, Edwin F. Hilinski and Xinsong Lin

Molecules 2023, 28(10), 4086; https://doi.org/10.3390/molecules28104086 - 14 May 2023

Viewed by 1069

Abstract

Cholesta-5,7,9(11)-trien-3β-ol (9,11-dehydroprovitamin D₃, CTL) is used as a fluorescent probe to track the presence and migration of cholesterol in vivo. We recently described the photochemistry and photophysics of CTL in degassed and air-saturated tetrahydrofuran (THF) solution, an aprotic solvent. The zwitterionic [...] Read more.

Cholesta-5,7,9(11)-trien-3β-ol (9,11-dehydroprovitamin D₃, CTL) is used as a fluorescent probe to track the presence and migration of cholesterol in vivo. We recently described the photochemistry and photophysics of CTL in degassed and air-saturated tetrahydrofuran (THF) solution, an aprotic solvent. The zwitterionic nature of the singlet excited state, ¹CTL* is revealed in ethanol, a protic solvent. In ethanol, the products observed in THF are accompanied by ether photoadducts and by photoreduction of the triene moiety to four dienes, including provitamin D₃. The major diene retains the conjugated s-trans-diene chromophore and the minor is unconjugated, involving 1,4-addition of H at the 7 and 11 positions. In the presence of air, peroxide formation is a major reaction channel as in THF. X-ray crystallography confirmed the identification of two of the new diene products as well as of a peroxide rearrangement product. Full article

(This article belongs to the Special Issue Chemical Insights in Photofunctional Organic Compounds—a Themed Issue Dedicated to Professor Vaidhyanathan Ramamurthy)

► Show Figures

Graphical abstract

14 pages, 4466 KiB

Open AccessArticle

Chiral Binaphthalene Building Blocks for Self-Assembled Nanoscale CPL Emitters

by Yu-Yu Hsieh, Jing-Jong Shyue, Yu-Chiang Chao, Ken-Tsung Wong and Dario M. Bassani

Molecules 2023, 28(8), 3382; https://doi.org/10.3390/molecules28083382 - 11 Apr 2023

Viewed by 1452

Abstract

The introduction of biuret hydrogen-bonding sites onto chiral binaphthalene-based chromophores was investigated as a route to sub-micron-sized, vesicle-like aggregates endowed with chiroptical properties. The synthesis was conducted from the corresponding chiral 4,4′-dibromo-1,1′-bis(2-naphthol) via Suzuki–Miyaura coupling to afford luminescent chromophores whose emission spectrum could [...] Read more.

The introduction of biuret hydrogen-bonding sites onto chiral binaphthalene-based chromophores was investigated as a route to sub-micron-sized, vesicle-like aggregates endowed with chiroptical properties. The synthesis was conducted from the corresponding chiral 4,4′-dibromo-1,1′-bis(2-naphthol) via Suzuki–Miyaura coupling to afford luminescent chromophores whose emission spectrum could be tuned from blue to yellow-green through extension of the conjugation. For all compounds, the spontaneous formation of hollow spheres with a diameter of ca. 200–800 nm was evidenced by scanning electron microscopy, along with strong asymmetry in the circularly polarized absorption spectra. For some compounds, the emission also displayed circular polarization with values of g_lum = ca. 10^–3 which could be increased upon aggregation. Full article

(This article belongs to the Special Issue Chemical Insights in Photofunctional Organic Compounds—a Themed Issue Dedicated to Professor Vaidhyanathan Ramamurthy)

► Show Figures

Graphical abstract

16 pages, 3226 KiB

Open AccessArticle

Molecular Characteristics of Water-Insoluble Tin-Porphyrins for Designing the One-Photon-Induced Two-Electron Oxidation of Water in Artificial Photosynthesis

by Arun Thomas, Yutaka Ohsaki, Ryosuke Nakazato, Fazalurahman Kuttassery, Siby Mathew, Sebastian Nybin Remello, Hiroshi Tachibana and Haruo Inoue

Molecules 2023, 28(4), 1882; https://doi.org/10.3390/molecules28041882 - 16 Feb 2023

Cited by 6 | Viewed by 1573

Abstract

Faced with the new stage of water oxidation by molecular catalysts (MCs) in artificial photosynthesis to overcome the bottle neck issue, the “Photon-flux density problem of sunlight,” a two-electron oxidation process forming H₂O₂ in place of the conventional four-electron oxidation [...] Read more.

Faced with the new stage of water oxidation by molecular catalysts (MCs) in artificial photosynthesis to overcome the bottle neck issue, the “Photon-flux density problem of sunlight,” a two-electron oxidation process forming H₂O₂ in place of the conventional four-electron oxidation evolving O₂ has attracted much attention. The molecular characteristics of tin(IV)-tetrapyridylporphyrin (SnTPyP), as one of the most promising MCs for the two-electron water oxidation, has been studied in detail. The protolytic equilibria among nine species of SnTPyP, with eight pK_a values on the axial ligands’ water molecules and peripheral pyridyl nitrogen atoms in both the ground and excited states, have been clarified through the measurements of UV-vis, fluorescence, ¹H NMR, and dynamic fluorescence decay behaviour. The oxidation potentials in the Pourbaix diagram and spin densities by DFT calculation of the one-electron oxidized form of each nine species have predicted that the fully deprotonated species ([SnTPyP(O⁻)₂]²⁻) and the singly deprotonated one ([SnTPyP(OH)(O⁻)]⁻) serve as the most favourable MCs for visible light-induced two-electron water oxidation when they are adsorbed on TiO₂ for H₂ formation or SnO₂ for Z-scheme CO₂ reduction in the molecular catalyst sensitized system of artificial photosynthesis. Full article

(This article belongs to the Special Issue Chemical Insights in Photofunctional Organic Compounds—a Themed Issue Dedicated to Professor Vaidhyanathan Ramamurthy)

► Show Figures

Graphical abstract

Review

Jump to: Research

16 pages, 4368 KiB

Open AccessReview

Photoactivatable BODIPYs for Live-Cell PALM

by Yang Zhang, Yeting Zheng, Andrea Tomassini, Ambarish Kumar Singh and Françisco M. Raymo

Molecules 2023, 28(6), 2447; https://doi.org/10.3390/molecules28062447 - 07 Mar 2023

Cited by 1 | Viewed by 1877

Abstract

Photoactivated localization microscopy (PALM) relies on fluorescence photoactivation and single-molecule localization to overcome optical diffraction and reconstruct images of biological samples with spatial resolution at the nanoscale. The implementation of this subdiffraction imaging method, however, requires fluorescent probes with photochemical and photophysical properties [...] Read more.

Photoactivated localization microscopy (PALM) relies on fluorescence photoactivation and single-molecule localization to overcome optical diffraction and reconstruct images of biological samples with spatial resolution at the nanoscale. The implementation of this subdiffraction imaging method, however, requires fluorescent probes with photochemical and photophysical properties specifically engineered to enable the localization of single photoactivated molecules with nanometer precision. The synthetic versatility and outstanding photophysical properties of the borondipyrromethene (BODIPY) chromophore are ideally suited to satisfy these stringent requirements. Specifically, synthetic manipulations of the BODIPY scaffold can be invoked to install photolabile functional groups and photoactivate fluorescence under photochemical control. Additionally, targeting ligands can be incorporated in the resulting photoactivatable fluorophores (PAFs) to label selected subcellular components in live cells. Indeed, photoactivatable BODIPYs have already allowed the sub-diffraction imaging of diverse cellular substructures in live cells using PALM and can evolve into invaluable analytical probes for bioimaging applications. Full article

(This article belongs to the Special Issue Chemical Insights in Photofunctional Organic Compounds—a Themed Issue Dedicated to Professor Vaidhyanathan Ramamurthy)

► Show Figures