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A Themed Issue in Honor of Professor David I. Schuster's Great Contribution

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A special issue of Photochem (ISSN 2673-7256).

Deadline for manuscript submissions: closed (30 September 2022) | Viewed by 28291

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Prof. Dr. Dirk M. Guldi

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Department of Chemistry and Pharmacy, Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, 91052 Erlangen, Germany
Interests: molecular hybrids; quantum dots; quantum rods and nanoparticles
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Dear Colleagues,

This Special Issue of Photochem is dedicated to Professor David Schuster in celebration of his 86th birthday and to mark his long and outstanding research career in Organic Photochemistry. Professor Schuster was born in Brooklyn, New York, in 1935. He graduated from Columbia College in New York City in 1956 and received his PhD in Chemistry and Physics from Caltech in 1960. Following a highly productive postdoctoral year with Howard Zimmerman at the University of Wisconsin Madison, he joined the faculty of New York University by invitation of Kurt Mislow in September 1961. He retired from full time teaching in 2005 though remained active in research until 2011. He continued to go to his office at NYU and to attend departmental seminars until the long lockdown due to the COVID-19 pandemic beginning in March 2020.

Schuster has conducted truly notable research in mechanistic organic photochemistry, inspired by the pioneering work of Zimmerman and of George Hammond at Caltech. During the early stages of his career at NYU, he conducted landmark research on photorearrangements of cyclohexadienones and cyclohexenones as well as [2+2] photocycloaddition reactions, including complex stereochemical studies that were critical in verifying predictions of the (then) new Woodward–Hoffmann rules for orbital symmetry control of photochemical reactions. During a sabbatical year with George Porter at the Royal Institution in London in 1968–1969, he performed the very first studies on the dynamic behavior of short-lived triplet excited states using the newly developed nanosecond flash photolysis process. In subsequent years, he pioneered microsecond and nanosecond flash techniques and was among the first to use time-resolved single photon counting and photoacoustic calorimetry to study the dynamics of fundamental photochemical processes. Notably, he was among the first to determine the energies and lifetimes of transient triplet 1,4-biradicals using time-resolved photoacoustic calorimetry. His many reviews in these areas are comprehensive and insightful contributions to the literature of photochemistry. For his many achievements, Schuster was elected a Fellow of the Inter-American Photochemical Society in 2005, for “lifetime achievements in and contribution to the photochemical sciences”. He also received the ACS Cope Scholar Award in 2012.

Beginning in the early 1990s, Professor Schuster’s research turned to the photochemistry and photophysics of fullerenes, beginning with photoinduced [2+2] additions of cyclic enones to pristine C60 and C70. His attention then turned to the synthesis and photophysics of artificial photosynthetic donor–acceptor (DA) systems in which porphyrins and other suitable groups act as electron donors and C60 acts as the electron acceptor, using a wide variety of covalent linkers. These studies were carried out with distinguished collaborators, most notably Dirk Guldi at the University of Erlangen-Nürnberg in Germany. It was discovered that back electron transfer in charge-separated states of porphyrin–fullerene hybrid systems generated by solar energy photons occurs in the Marcus inverted region. The finding of relatively long-lived charge-separated states of such systems in turn impacts designs for the construction of functional nanoscale organic photovoltaic devices, yields, and transient absorption measurements on picosecond and nanosecond time scales. Additionally, time-resolved electron paramagnetic resonance studies in collaboration with Haim Levanon’s group in Israel provided insight into the spin dynamics of these nanomolecular systems at low temperatures.

In the final phase of his career, Schuster’s research has centered on the construction of rotaxanes and catenanes in which the donor (porphyrins, phthalocyanines, ferrocene) and acceptor (C60) moieties are mechanically rather than covalently linked. This work has shed light on topological control of through-bond vs. through-space long-range intramolecular electron and energy transfer processes. He and his collaborators demonstrated that a series of energy and electron transfer processes occur along an energy gradient to give long-lived charge-separated radical pair states with 2–3 nm separation of charged centers and lifetimes in the microsecond time domain. Such materials have great potential for use in devices for solar energy conversion.

Schuster and his wife Carlotta now reside near Lincoln Center in New York, where they continue to pursue their lifelong interest in music and the arts and their deep involvement with the cultural and gastronomic life of their beloved city, now re-emerging following the shutdown due to the disastrous COVID-19 pandemic.

Prof. Dr. Dirk M. Guldi
Guest Editor

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Keywords

photochemistry
photophysics
solar energy conversion
photoinduced electron transfer
photoinduced energy transfer
fullerenes
rotaxanes
catenanes
triplet states
porphyrins

Published Papers (13 papers)

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14 pages, 426 KiB

Open AccessArticle

Effect of the Donor/Acceptor Size on the Rate of Photo-Induced Electron Transfer

by Nikolai V. Tkachenko

Photochem 2022, 2(4), 918-931; https://doi.org/10.3390/photochem2040059 - 30 Nov 2022

Cited by 2 | Viewed by 1558

Abstract

The photo-induced electron transfer has been under intensive investigation for a few decades already, and a good understanding of the reaction was developed based on thorough study of the molecular donor–acceptor (DA) system. The recent shift to hybrid DA systems opens the question of transferring the knowledge to analyze and design these new materials. One of the apparent differences is the size increase of the donor or acceptor entities. The electronic wave functions of larger entities occupy a larger volume, but since these are still one-electron wave functions, their amplitudes are lower. A simple analysis proposed here demonstrates that this leads to roughly inverse third power dependence of the electron transfer rate constant on the donor or acceptor size,

k_{E T} \propto R^{- 3}

. This dependence can be observed upon switching from molecular to quantum dot donor in DA systems with a fullerene acceptor. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor David I. Schuster's Great Contribution)

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17 pages, 3309 KiB

Open AccessArticle

Photobehavior of an Acidochromic Dinitrophenyl-Hydrazinylidene Derivative: A Case of Total Internal Conversion

by Letizia Mencaroni, Alessio Cesaretti, Giuseppe Consiglio, Fausto Elisei, Cosimo Gianluca Fortuna and Anna Spalletti

Photochem 2022, 2(4), 849-865; https://doi.org/10.3390/photochem2040054 - 10 Oct 2022

Cited by 1 | Viewed by 1338

Abstract

Research in photochemistry is always looking for novel compounds that can serve a role in applications ranging from medicine to environmental science. Push–pull compounds with protonable groups represent an interesting class of molecules in this sense, as they can prove to be sensitive to changes in both the acidity and polarity of the medium, becoming valuable as sensors and probes. Hence, in this work, a new dinitrophenyl-hydrazinylidene derivative with multiple protonable centers has been specifically designed and synthesized. The molecule showed an important acidochromism in the visible, with three differently-protonated species under acidic, neutral, and basic conditions, each characterized by a peculiar absorption spectrum. The photophysical characterization of this compound revealed an ultrafast excited-state deactivation, as described by femtosecond transient absorption experiments, and the hints of charge-transfer dynamics, as supported by the observed solvatochromism and quantum-mechanical calculations. These properties led to almost undetectable fluorescence that, together with negligible intersystem crossing and the absence of reactive pathways, points to the preference for a total non-radiative deactivation mechanism, i.e., internal conversion. This intriguing behavior stimulates interest in light of possible applications of the investigated acidochromic dye as a probe in photoacoustic imaging, which offers an alternative to classical fluorescence imaging. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor David I. Schuster's Great Contribution)

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18 pages, 2243 KiB

Open AccessArticle

Efficient Access of Phenyl-Spaced 5,5′-Bridged Dinuclear Ruthenium Metal Complexes and the Effect of Dynamic Ligand Exchange on Catalysis

by Martin Lämmle, Steffen Volk, Madelyn Klinkerman, Marius Müßler, Alexander K. Mengele and Sven Rau

Photochem 2022, 2(4), 831-848; https://doi.org/10.3390/photochem2040053 - 06 Oct 2022

Cited by 1 | Viewed by 1412

Abstract

Herein, we present the synthesis, characterization, and light-driven hydrogen evolution activity of two dinuclear Ru-Pt complexes, Rup(ph)pPtX₂ (X = Cl, I), comprising a new phenyl-spaced 5,5′-bis-phenanthroline p(ph)p bridging ligand. The two complexes only differ in the nature of the halide ligand at the catalytic center. Structural, photophysical, electrochemical, as well as photochemical characterization techniques revealed that the variations of single components of the intramolecular system provide a strong influence on the stability even in non-catalytic conditions. Interestingly, varying electron density at the catalytic center, mainly influenced by the coordinating halide at the catalytic center, as shown by ¹⁹⁵Pt NMR spectroscopy, strongly influences the photocatalytic efficiency. Furthermore, intensive investigations on the potential catalytic mechanism showed that small structural variations (e.g., halide exchange) not only affect catalytic activity but can also switch the main catalytic mechanism from an initially molecular one to a fully heterogeneous, colloid-driven hydrogen evolution. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor David I. Schuster's Great Contribution)

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16 pages, 5440 KiB

Open AccessArticle

Awakening a Molecular Mummy: The Inter-and Intramolecular Photochemistry of Pyromellitic Diimides with Alkyl Carboxylates

by Wolfgang H. Kramer, Donya Razinoubakht, Gurjit Kaur, Axel Klein, Simon Garbe, Jörg Neudörfl, Sabrina Molitor, Anne Zimmer and Axel G. Griesbeck

Photochem 2022, 2(3), 717-732; https://doi.org/10.3390/photochem2030046 - 24 Aug 2022

Viewed by 1727

Abstract

Pyromellitic acid diimides are not as chemically unreactive as conjecturable (and presupposed) from their numerous applications as electron acceptor units or electron carriers in molecular donor–acceptor dyads or triads. Similar to the corresponding phthalimides, electronically excited pyromellitic diimides oxidize alkyl carboxylates in aqueous solution via intermolecular electron transfer (PET) processes, which eventually results in radical–radical combination products, e.g., the benzylation product 6 from N,N′-dimethyl pyromellitic diimide 5. The analogous product 7 was formed with pivalic acid as tert-butyl radical source. One additional product 8 was isolated from alkylation/dearomatization and multiple radical additions, respectively, after prolonged irradiation. In intramolecular versions, from N-carboxyalkylated pyromellitic diimides 9a–e (C₁ to C₅-spaced), degradation processes were detected, e.g., the cyclization products 10 from the GABA substrate 9c. In sharp contrast to phthalimide photochemistry, the green pyromellitic diimide radical anion was detected here by UV-vis absorption (λ_abs = 720 nm), EPR (from 9d), and NMR spectroscopy for several intramolecular electron transfer examples. Only the yellow 1,4-quinodial structure is formed from intermolecular PET, which was deduced from the absorption spectra (λ_abs = 440 nm) and the subsequent chemistry. The pyromellitimide radical anion lives for hours at room temperature in the dark, but is further degraded under photochemical reaction conditions. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor David I. Schuster's Great Contribution)

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22 pages, 11299 KiB

Open AccessFeature PaperArticle

Consecutive Multicomponent Coupling-Addition Synthesis and Chromophore Characteristics of Cyclohexene-Embedded Merocyanines and Cyanines

by Julian Papadopoulos, Tabea Gerlach, Guido J. Reiss, Bernhard Mayer and Thomas J. J. Müller

Photochem 2022, 2(3), 672-693; https://doi.org/10.3390/photochem2030044 - 19 Aug 2022

Cited by 2 | Viewed by 1409

Abstract

Merocyanines with embedded butadiene structure in a cyclohexane scaffold are readily obtained by consecutive three-component alkynylation-addition sequences in moderate to excellent yield. Moreover, employing pyrrolidine as an amine provides a pseudo four-component synthesis of related cyanines by carbonyl condensation of the heterocyclic amine in excellent yield. While the merocyanines are essentially nonluminescent, pentamethine cyanines show luminescence with low quantum yield. TDDFT calculations using various exchange correlation hybrid functionals in the gas phase and explicit continuum of dichloromethane underline that the lowest energy absorption bands are highly solvent dependent for a merocyanine and cyanine model. The blue-shifted deviation from the experimental spectra agrees with related merocyanine and cyanine systems. The lowest energy absorption band of merocyanines contains n-π* character, which rationalizes the absence of luminescence. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor David I. Schuster's Great Contribution)

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16 pages, 2602 KiB

Open AccessArticle

Comparison of the Photodynamic Effect of Two Chlorins, Photodithazine and Fotoenticine, in Gliosarcoma Cells

by Letícia Corrêa Fontana, Juliana Guerra Pinto, Jéssica Aparecida Magalhães, Dayane Batista Tada, Rainara Moreno Sanches de Almeida, Cristina Pacheco-Soares and Juliana Ferreira-Strixino

Photochem 2022, 2(1), 165-180; https://doi.org/10.3390/photochem2010013 - 25 Feb 2022

Cited by 3 | Viewed by 2031

Abstract

The treatment and prognosis of cancers of the nervous system remain unfavorable to the patient, which makes it necessary to study alternative therapies as primary or adjuvant treatments to existing methods. Photodynamic Therapy (PDT) is a method that consists of combining a photosensitizer (PS), a light source at the appropriate wavelength, and molecular oxygen, forming reactive oxygen species (ROS), leading to death in the target cell. The objective of this work was to compare the effects of PDT with two chlorins, Photodithazine (PDZ) and Fotoenticine (FTC), in 9L/lacZ gliosarcoma cell lines. Both chlorins, together with an LED device at 660 nm with a fluence of 10 J/cm², were included in the study. It was observed that the response to therapy depends on the concentration and type of PS used. In addition, PDZ showed a higher quantum yield of singlet oxygen generation than FTC. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor David I. Schuster's Great Contribution)

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16 pages, 5813 KiB

Open AccessArticle

Photoreactions of Sc₃N@C₈₀ with Disilirane, Silirane, and Digermirane: A Photochemical Method to Separate I_h and D_5h Isomers

by Masahiro Kako, Kyosuke Miyabe, Shinpei Fukazawa, Shinji Kanzawa, Masanori Yasui, Michio Yamada, Yutaka Maeda, Zdeněk Slanina, Filip Uhlík, Ludwik Adamowicz, Ilias Papadopoulos, Dirk M. Guldi, Makoto Furukawa, Shigeru Nagase and Takeshi Akasaka

Photochem 2022, 2(1), 122-137; https://doi.org/10.3390/photochem2010010 - 07 Feb 2022

Cited by 1 | Viewed by 2177

Abstract

Under photoirradiation, Sc₃N@I_h-C₈₀ reacted readily with disilirane 1, silirane 4, and digermirane 7 to afford the corresponding 1:1 adducts, whereas Sc₃N@D_5h-C₈₀ was recovered without producing those adducts. Based on these results, we described a novel method for the exclusive separation of I_h and D_5h isomers of Sc₃N@C₈₀. The method includes three procedures: selective derivatization of Sc₃N@I_h-C₈₀ using 1, 4, and 7, facile HPLC separation of pristine Sc₃N@D_5h-C₈₀ and Sc₃N@I_h-C₈₀ derivatives, and thermolysis of Sc₃N@I_h-C₈₀ derivatives to collect pristine Sc₃N@I_h-C₈₀. In addition, laser flash photolysis experiments were conducted to elucidate the reaction mechanism. Decay of the transient absorption of ³Sc₃N@I_h-C₈₀^* was observed to be enhanced in the presence of 1, indicating the quenching process. When Sc₃N@D_5h-C₈₀ was used, the transient absorption was much less intensive. Therefore, the quenching of ³Sc₃N@D_5h-C₈₀^* by 1 could not be confirmed. Furthermore, we applied time-dependent density functional theory (TD-DFT) calculations of the photoexcited states of Sc₃N@C₈₀ to obtain insights into the reaction mechanism. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor David I. Schuster's Great Contribution)

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11 pages, 1894 KiB

Open AccessArticle

A P-61 Black Widow Inspired Palladium Biladiene Complex for Efficient Sensitization of Singlet Oxygen Using Visible Light

by Anthony T. Rice, Glenn P. A. Yap and Joel Rosenthal

Photochem 2022, 2(1), 58-68; https://doi.org/10.3390/photochem2010005 - 11 Jan 2022

Cited by 5 | Viewed by 2413

Abstract

Photodynamic therapy (PDT) is a promising treatment option that ablates cancerous cells and tumors via photoinduced sensitization of singlet oxygen. Over the last few decades, much work has been devoted to the development of new photochemotherapeutic agents for PDT. A wide variety of macrocyclic tetrapyrrole based photosensitizers have been designed, synthesized and characterized as PDT agents. Many of these complexes have a variety of issues that pose a barrier to their use in humans, including biocompatibility, inherent toxicity, and synthetic hurdles. We have developed a non-traditional, non-cyclic, and non-aromatic tetrapyrrole ligand scaffold, called the biladiene (DMBil1), as an alternative to these traditional photosensitizer complexes. Upon insertion of a heavy atom such as Pd²⁺ center, Pd[DMBil1] generates singlet oxygen in substantial yields (Φ_Δ = 0.54, λ_exc = 500 nm) when irradiated with visible light. To extend the absorption profile for Pd[DMBil1] deeper into the phototherapeutic window, the tetrapyrrole was conjugated with alkynyl phenyl groups at the 2- and 18-positions (Pd[DMBil2-PE]) resulting in a significant redshift while also increasing singlet oxygen generation (Φ_Δ = 0.59, 600 nm). To further modify the dialkynyl-biladiene scaffold, we conjugated a 1,8-diethynylanthracene with to the Pd[DMBil1] tetrapyrrole in order to further extend the compound’s π-conjugation in a cyclic loop that spans the entire tetrapyrrole unit. This new compound (Pd[DMBil2-P61]) is structurally reminiscent of the P61 Black Widow aircraft and absorbs light into the phototherapeutic window (600–900 nm). In addition to detailing the solid-state structure and steady-state spectroscopic properties for this new biladiene, photochemical sensitization studies demonstrated that Pd[DMBil2-P61] can sensitize the formation of ¹O₂ with quantum yields of Φ_Δ = 0.84 upon irradiation with light λ = 600 nm. These results distinguish the Pd[DMBil2-P61] platform as the most efficient biladiene-based singlet oxygen photosensitizer developed to date. When taken together, the improved absorption in the phototherapeutic window and high singlet oxygen sensitization efficiency of Pd[DMBil2-P61] mark this compound as a promising candidate for future study as an agent of photodynamic cancer therapy. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor David I. Schuster's Great Contribution)

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23 pages, 4217 KiB

Open AccessArticle

Photophysics and Electrochemistry of Biomimetic Pyranoflavyliums: What Can Bioinspiration from Red Wines Offer

by Eli Misael Espinoza, John Anthony Clark, Mimi Karen Billones, Gustavo Thalmer de Medeiros Silva, Cassio Pacheco da Silva, Frank Herbert Quina and Valentine Ivanov Vullev

Photochem 2022, 2(1), 9-31; https://doi.org/10.3390/photochem2010003 - 06 Jan 2022

Cited by 3 | Viewed by 2481

Abstract

Natural dyes and pigments offer incomparable diversity of structures and functionalities, making them an excellent source of inspiration for the design and development of synthetic chromophores with a myriad of emerging properties. Formed during maturation of red wines, pyranoanthocyanins are electron-deficient cationic pyranoflavylium dyes with broad absorption in the visible spectral region and pronounced chemical and photostability. Herein, we survey the optical and electrochemical properties of synthetic pyranoflavylium dyes functionalized with different electron-donating and electron-withdrawing groups, which vary their reduction potentials over a range of about 400 mV. Despite their highly electron-deficient cores, the exploration of pyranoflavyliums as photosensitizers has been limited to the “classical” n-type dye-sensitized solar cells (DSSCs) where they act as electron donors. In light of their electrochemical and spectroscopic properties, however, these biomimetic synthetic dyes should prove to be immensely beneficial as chromophores in p-type DSSCs, where their ability to act as photooxidants, along with their pronounced photostability, can benefit key advances in solar-energy science and engineering. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor David I. Schuster's Great Contribution)

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14 pages, 4709 KiB

Open AccessArticle

Foam-like 3D Graphene as a Charge Transport Modifier in Zinc Oxide Electron Transport Material in Perovskite Solar Cells

by Mohamed Salleh Mohamed Saheed, Norani Muti Mohamed, Balbir Singh Mahinder Singh, Qamar Wali, Mohamed Shuaib Mohamed Saheed and Rajan Jose

Photochem 2021, 1(3), 523-536; https://doi.org/10.3390/photochem1030034 - 08 Dec 2021

Cited by 2 | Viewed by 2433

Abstract

The effect of foam-like 3D graphene (3DG) in an electron transport material (ETM), viz. ZnO thin film, on the steady-state photoluminescence (PL), light-harvesting efficiency (LHE), photocurrent density (J_SC), photovoltage (V_OC), and charge transport parameters of perovskite solar cells (PSCs) are systematically investigated. The ETM is developed by spin coating a ZnO precursor solution containing varying amounts of 3DG on conducting glass substrates and appropriate annealing. A significant improvement in the photoconversion efficiency of PSCs is observed for a low concentration of 3DG in ZnO. The current–voltage and electrochemical impedance spectroscopy measurements show that the addition of 3DG enhances the V_OC due to efficient electron–hole separation and charge transport compared to the pristine ZnO. These studies offer a route for further advances in enhancing the optoelectronic properties of ETM for artificial photosynthesis and photocatalysis devices. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor David I. Schuster's Great Contribution)

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18 pages, 3539 KiB

Open AccessArticle

Photodynamic Effect of 5,10,15,20-Tetrakis[4-(3-N,N-dimethylaminopropoxy)phenyl]chlorin towards the Human Pathogen Candida albicans under Different Culture Conditions

by Paula V. Cordero, Darío D. Ferreyra, María E. Pérez, María G. Alvarez and Edgardo N. Durantini

Photochem 2021, 1(3), 505-522; https://doi.org/10.3390/photochem1030033 - 03 Dec 2021

Cited by 1 | Viewed by 1895

Abstract

Photocytotoxic activity sensitized by 5,10,15,20-tetrakis[4-(3-N,N-dimethylaminopropoxy)phenyl]chlorin (TAPC) was investigated in Candida albicans under different culture conditions. Planktonic cells incubated with 2.5 μM TAPC were eradicated after 5 min irradiation with white light. Studies in the presence of reactive oxygen species scavengers indicated the involvement of mainly a type II mechanism. Furthermore, cell growth of C. albicans was suppressed in the presence of 5 μM TAPC. A decrease in pseudohyphae survival of 5 log was found after 30 min irradiation. However, the photokilling of this virulence factor reached a 1.5 log reduction in human serum. The uptake of TAPC by pseudohyphae decreased in serum due to the interaction of TAPC with albumin. The binding constant of the TAPC-albumin complex was ~10⁴ M⁻¹, while the bimolecular quenching rate constant was ~10¹² s⁻¹ M⁻¹, indicating that this process occurred through a static process. Thus, the photoinactivation of C. albicans was considerably decreased in the presence of albumin. A reduction of 2 log in cell survival was observed using 4.5% albumin and 30 min irradiation. The results allow optimizing the best conditions to inactivate C. albicans under different culture conditions. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor David I. Schuster's Great Contribution)

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26 pages, 23730 KiB

Open AccessReview

Nanostructured Luminescent Micelles: Efficient “Functional Materials” for Sensing Nitroaromatic and Nitramine Explosives

by Shashikana Paria, Prasenjit Maity, Rafia Siddiqui, Ranjan Patra, Shubhra Bikash Maity and Atanu Jana

Photochem 2022, 2(1), 32-57; https://doi.org/10.3390/photochem2010004 - 10 Jan 2022

Cited by 6 | Viewed by 3245

Abstract

Luminescent micelles are extensively studied molecular scaffolds used in applied supramolecular chemistry. These are particularly important due to their uniquely organized supramolecular structure and chemically responsive physical and optical features. Various luminescent tags can be incorporated with these amphiphilic micelles to create efficient luminescent probes that can be utilized as “chemical noses” (sensors) for toxic and hazardous materials, bioimaging, drug delivery and transport, etc. Due to their amphiphilic nature and well-defined reorganized self-assembled geometry, these nano-constructs are desirable candidates for size and shape complementary guest binding or sensing a specific analyte. A large number of articles describing micellar fluorogenic probes are reported, which are used for cation/anion sensing, amino acid and protein sensing, drug delivery, and chemo-sensing. However, this particular review article critically summarizes the sensing application of nitroaromatic (e.g., trinitrotoluene (TNT), trinitrobenzene (TNB), trinitrophenol (TNP), dinitrobenzene (DNB), etc.) and nitramine explosives (e.g., 1,3,5-trinitro-1,3,5-triazinane, trivially named as “research department explosive” (RDX), 1,3,5,7-tetranitro-1,3,5,7-tetrazocane, commonly known as “high melting explosive” (HMX) etc.). A deeper understanding on these self-assembled luminescent “functional materials” and the physicochemical behavior in the presence of explosive analytes might be helpful to design the next generation of smart nanomaterials for forensic applications. This review article will also provide a “state-of-the-art” coverage of research involving micellar–explosive adducts demonstrating the intermolecular charge/electron transfer (CT/ET) process operating within the host–guest systems. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor David I. Schuster's Great Contribution)

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23 pages, 5582 KiB

Open AccessReview

A Brief History of Photoactive Interlocked Systems Assembled by Transition Metal Template Synthesis

by Vitor H. Rigolin, Liniquer A. Fontana and Jackson D. Megiatto, Junior

Photochem 2021, 1(3), 411-433; https://doi.org/10.3390/photochem1030025 - 21 Oct 2021

Viewed by 2482

Abstract

More than three decades of research efforts have yielded powerful methodologies based on transition metal template-directed syntheses for the assembly of a huge number of interlocked systems, molecular knots, machines and synthesizers. Such template techniques have been applied in the preparation of mechanically linked electron donor–acceptor artificial photosynthetic models. Consequently, synthetic challenging photoactive rotaxanes and catenanes have been reported, in which the chromophores are not covalently linked but are still associated with undergoing sequential energy (EnT) and electron transfer (ET) processes upon photoexcitation. Many interlocked photosynthetic models produce highly energetic, but still long-living charge separated states (CSS). The present work describes in a historical perspective some key advances in the field of photoactive interlocked systems assembled by transition metal template techniques, which illustrate the usefulness of rotaxanes and catenanes as molecular scaffolds to organize electron donor–acceptor groups. The effects of molecular dynamics, molecular topology, as well as the role of the transition metal ion used as template species, on the thermodynamic and kinetic parameters of the photoinduced energy and electron transfer processes in the interlocked systems are also discussed. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor David I. Schuster's Great Contribution)

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