All evolutionary biological processes lead to a change in heritable traits over successive generations. The responsible genetic information encoded in DNA is altered, selected, and inherited by ...mutation of the base sequence. While this is well known at the biological level, an evolutionary change at the molecular level of small organic molecules is unknown but represents an important prerequisite for the emergence of life. Here, we present a class of prebiotic imidazolidine‐4‐thione organocatalysts able to dynamically change their constitution and potentially capable to form an evolutionary system. These catalysts functionalize their building blocks and dynamically adapt to their (self‐modified) environment by mutation of their own structure. Depending on the surrounding conditions, they show pronounced and opposing selectivity in their formation. Remarkably, the preferentially formed species can be associated with different catalytic properties, which enable multiple pathways for the transition from abiotic matter to functional biomolecules.
Prebiotically plausible imidazolidine‐4‐thione organocatalysts are able to dynamically adapt to their environment by mutation of their own structure. Depending on the surrounding conditions, a distinct preference for certain species was identified, that correlates with the catalytic activity. This variation and selection mechanism allows for ongoing evolution of catalytic properties to create the complex diversity of life.
Organocatalysis is a powerful approach to extend and (enantio‐) selectively modify molecular structures. Adapting this concept to the Early Earth scenario offers a promising solution to explain their ...evolution into a complex homochiral world. Herein, we present a class of imidazolidine‐4‐thione organocatalysts, easily accessible from simple molecules available on an Early Earth under highly plausible prebiotic reaction conditions. These imidazolidine‐4‐thiones are readily formed from mixtures of aldehydes or ketones in presence of ammonia, cyanides and hydrogen sulfide in high selectivity and distinct preference for individual compounds of the resulting catalyst library. These organocatalysts enable the enantioselective α‐alkylation of aldehydes under prebiotic conditions and show activities that correlate with the selectivity of their formation. Furthermore, the crystallization of single catalysts as conglomerates opens the pathway for symmetry breaking.
Kick‐start for the origin of life: A class of imidazolidine‐4‐thione organocatalysts has been identified enabling enantioselective α‐alkylation of aldehydes under prebiotic conditions. These catalysts are easily accessible from simple molecules available on an Early Earth under highly plausible prebiotic reaction conditions. Remarkably, they crystallize as conglomerate facilitating the process of spontaneous symmetry breaking.
Imidazolidine-4-thiones have been suggested as potential prebiotic organocatalysts for light-driven α-alkylations of aldehydes by bromoacetonitrile. However, imidazolidine-4-thiones react with ...bromoacetonitrile to give
-cyanomethylated dihydroimidazoles. Kinetic studies show that enamines derived from these cyclic secondary amines and aldehydes are more nucleophilic than enamines derived from aldehydes and MacMillan organocatalysts.
The acetate-initiated aliphatic isocyanate trimerization to isocyanurate was investigated by state-of-the-art analytical and computational methods. Although the common cyclotrimerization mechanism ...assumes the consecutive addition of three equivalents of isocyanate to acetate prior to product formation, we found that the underlying mechanism is more complex. In this work, we demonstrate that the product, in fact, is formed via the connection of two unexpected catalytic cycles, with acetate being only the precatalyst. The initial discovery of a precatalyst activation by quantum chemical computations and the resulting first catalysis cycle were corroborated by mass spectrometric and NMR experiments, thereby additionally revealing a catalyst migration to the second catalytic cycle. These results were further confirmed by computations, completing the full mechanistic understanding of this catalytic system. Identification of a side product with undesired properties for final coating applications allows for process optimization in the chemical industry.
State‐of‐the‐art perovskite‐based solar cells employ expensive, organic hole transporting materials (HTMs) such as Spiro‐OMeTAD that, in turn, limits the commercialization of this promising ...technology. Herein an HTM (EDOT‐Amide‐TPA) is reported in which a functional amide‐based backbone is introduced, which allows this material to be synthesized in a simple condensation reaction with an estimated cost of <$5 g−1. When employed in perovskite solar cells, EDOT‐Amide‐TPA demonstrates stabilized power conversion efficiencies up to 20.0% and reproducibly outperforms Spiro‐OMeTAD in direct comparisons. Time resolved microwave conductivity measurements indicate that the observed improvement originates from a faster hole injection rate from the perovskite to EDOT‐Amide‐TPA. Additionally, the devices exhibit an improved lifetime, which is assigned to the coordination of the amide bond to the Li‐additive, offering a novel strategy to hamper the migration of additives. It is shown that, despite the lack of a conjugated backbone, the amide‐based HTM can outperform state‐of‐the‐art HTMs at a fraction of the cost, thereby providing a novel set of design strategies to develop new, low‐cost HTMs.
In order to reduce the cost of hole transporting materials (HTMs) for perovskite solar cells, the amide‐bond is introduced in the backbone resulting in a straightforward synthesis. Despite the lack of conjugation, the here presented HTM (EDOT‐Amide‐TPA) outperforms state‐of‐the‐art materials in performance, showing over 20% power conversion efficiency, and stability, which is assigned to the unique properties of the amide‐bond.
The current state-of-the-art hole transporting materials (HTM) for perovskite solar cells are generally synthesized via cross-coupling reactions that require expensive catalysts, inert reaction ...conditions and extensive product purification, resulting in high costs and therefore limiting large-scale commercialisation. Here we describe a series of HTMs prepared via simple and clean Schiff-base condensation chemistry with an estimated material cost in the range of 4–54 $ per g. The optoelectronic and thermal properties of the materials are linked to the changes in the chemical structure of the HTMs, which allow us to extract design rules for new materials, supported by density functional theory calculations. Charge transport measurements show hole mobilities in the range of 10 −5 to 10 −7 cm 2 V −1 s −1 . Upon addition of LiTFSI the HTMs can be oxidized, resulting in a large increase in the conductivity of the hole transporting layer (HTL). When employed as HTL in perovskite solar cells, power conversion efficiencies close to those of spiro-OMeTAD are obtained. In particular, devices prepared with Diazo-OMeTPA show a higher open-circuit voltage. Furthermore, we show that azomethine-based HTMs can act as effective moisture barriers, resulting in a significant increase in the stability of the underlying perovskite film. We assign the improved properties to the presence of a dipole in our molecules which promotes a close molecular packing and thus leads to a high density of the as-formed HTM films, preventing the ingress of water. This work shows that HTMs prepared via condensation chemistry are not only a low-cost alternative to spiro-OMeTAD, but also act as a functional barrier against moisture-induced degradation in perovskite solar cells.
Abstract
Alle evolutionsbiologischen Prozesse führen zu einer Veränderung der vererbbaren Merkmale über nachfolgende Generationen hinweg. Die in der DNA kodierte genetische Information wird durch ...Mutation der Basensequenz verändert, selektiert und vererbt. Während dies auf der biologischen Ebene gut verstanden wird, ist eine evolutionäre Veränderung auf der molekularen Ebene kleiner organischer Moleküle unbekannt, stellt aber eine wichtige Voraussetzung für die Entstehung von Leben dar. In dieser Arbeit stellen wir eine Klasse von präbiotischen Imidazolidin‐4‐thion‐Organokatalysatoren vor, die ihre Zusammensetzung dynamisch ändern können und möglicherweise in der Lage sind, ein evolutionäres System zu bilden. Diese Katalysatoren funktionalisieren ihre Bausteine und passen sich durch Mutation ihrer eigenen Struktur dynamisch an ihre (selbst modifizierte) Umgebung an. Abhängig von den Umgebungsbedingungen zeigen sie eine ausgeprägte und gegensätzliche Selektivität bei ihrer Bildung. Bemerkenswerterweise können die bevorzugt gebildeten Spezies mit unterschiedlichen katalytischen Eigenschaften verbunden sein, die mehrere Wege für den Übergang von abiotischer Materie zu funktionellen Biomolekülen ermöglichen.
Perovskite solar cells have shown an exceptionally fast increase in performance. So far, most high performing devices comprise expensive hole transport material (HTM) which are synthesized using ...tedious synthetic procedures, resulting in a high cost and thereby limit the potential use in large-scale applications. In a quest to find low-cost chemistry to link the building blocks, we explore hydrazone-based small molecules in this work. These materials can be synthesized in a simple condensation reaction, with water being the only side product leading to a low material cost of less than $10 per g. When used as hole transporting layers in perovskite solar cells, highly reproducible performance was obtained, similar to state-of-the-art materials, with the main difference being a small open-circuit voltage loss due to increased interfacial recombination. Thus, we show that hydrazone-based materials have the potential to compete in performance with materials obtained via cross-coupling reactions at a fraction of their cost.
Imidazolidine-4-thiones have been suggested as potential prebiotic organocatalysts for light-driven α-alkylations of aldehydes by bromoacetonitrile. However, imidazolidine-4-thiones react with ...bromoacetonitrile to give
S
-cyanomethylated dihydroimidazoles. Kinetic studies show that enamines derived from these cyclic secondary amines and aldehydes are more nucleophilic than enamines derived from aldehydes and MacMillan organocatalysts.
Enamine intermediates in the organocatalytic α-cyanomethylation of enolisable aldehydes were identified and their reactivities on the Mayr nucleophilicity scale determined.
Alle evolutionsbiologischen Prozesse führen zu einer Veränderung der vererbbaren Merkmale über nachfolgende Generationen hinweg. Die in der DNA kodierte genetische Information wird durch Mutation der ...Basensequenz verändert, selektiert und vererbt. Während dies auf der biologischen Ebene gut verstanden wird, ist eine evolutionäre Veränderung auf der molekularen Ebene kleiner organischer Moleküle unbekannt, stellt aber eine wichtige Voraussetzung für die Entstehung von Leben dar. In dieser Arbeit stellen wir eine Klasse von präbiotischen Imidazolidin‐4‐thion‐Organokatalysatoren vor, die ihre Zusammensetzung dynamisch ändern können und möglicherweise in der Lage sind, ein evolutionäres System zu bilden. Diese Katalysatoren funktionalisieren ihre Bausteine und passen sich durch Mutation ihrer eigenen Struktur dynamisch an ihre (selbst modifizierte) Umgebung an. Abhängig von den Umgebungsbedingungen zeigen sie eine ausgeprägte und gegensätzliche Selektivität bei ihrer Bildung. Bemerkenswerterweise können die bevorzugt gebildeten Spezies mit unterschiedlichen katalytischen Eigenschaften verbunden sein, die mehrere Wege für den Übergang von abiotischer Materie zu funktionellen Biomolekülen ermöglichen.
Präbiotisch plausible Imidazolidin‐4‐thion‐Organokatalysatoren sind in der Lage, sich durch Mutation ihrer eigenen Struktur dynamisch an ihre Umgebung anzupassen. In Abhängigkeit von den Umgebungsbedingungen wurde eine deutliche Präferenz für bestimmte Arten identifiziert, die mit der katalytischen Aktivität korreliert. Dieser Variations‐ und Selektionsmechanismus ermöglicht eine kontinuierliche Evolution der katalytischen Eigenschaften, die die komplexe Vielfalt des Lebens hervorbringt.
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