Periodic Reporting for period 1 - COSY-PANTERA (Controlled Synthesis of Panchromatic Electrochromic Polytriarylamines)
Periodo di rendicontazione: 2022-06-01 al 2024-05-31
π-Conjugated macrocycles are important in materials science and supramolecular chemistry due to their large, highly conjugated nature, which is useful for molecular recognition, e.g. environmental remediation by removing toxic heavy metals, and optoelectronic applications, e.g. production of smart, sustainable electronic devices. Despite their potential, π-conjugated macrocycles’ difficult multi-step synthesis has precluded their widespread use. Among these, azaparacyclophanes (APCs) are appealing due to their fully π-conjugated, shape-persistent macrocyclic structures with triarylamine (TAA) units. These macromolecules are ideal active layer materials in organic electronics and display unique optical, electronic, and magnetic properties. COSY-PANTERA aimed to address this synthetic challenge by developing an efficient and catalytic one-step strategy, herein termed catalyst-transfer macrocyclization (CTM) methodology for APC synthesis. Hence, the primary objective accomplished was a novel simple, inexpensive, reproducible, reliable and environmentally-friendly high-yield efficient synthetic method that produces structurally precise APCs with various ring sizes and substituents under mild reaction conditions.
The one-step CTM reaction provides a practical, efficient method for synthesizing APCs with high yield and scalability potential. The reaction's versatility and the ability to operate under different regimes make it a valuable tool for expanding the chemical space of APCs. Further optimization and mechanistic understanding can enhance its applicability in synthesizing topologically complex macrocycles for various applications in materials science and beyond.
The results of this project are expected to have a significant impact on the field of materials science by providing easier access to numerous APCs, which can then be more readily integrated into optoelectronic devices. This new method could significantly broaden the chemical space and application potential of these materials, making them more viable for commercial use. By simplifying the production process, the project is positioned to accelerate the development and implementation of advanced organic semiconductor materials in commercial electronic products. The ability to produce APCs more efficiently could lead to innovations in a variety of high-technology applications, from more efficient flexible solar cells to advanced display technologies, thereby contributing to advancements in sustainable energy and electronics.
The one-step CTM reaction provides a practical, efficient method for synthesizing APCs with high yield and scalability potential. The reaction's versatility and the ability to operate under different regimes make it a valuable tool for expanding the chemical space of APCs. Further optimization and mechanistic understanding can enhance its applicability in synthesizing topologically complex macrocycles for various applications in materials science and beyond.
The results of this project are expected to have a significant impact on the field of materials science by providing easier access to numerous APCs, which can then be more readily integrated into optoelectronic devices. This new method could significantly broaden the chemical space and application potential of these materials, making them more viable for commercial use. By simplifying the production process, the project is positioned to accelerate the development and implementation of advanced organic semiconductor materials in commercial electronic products. The ability to produce APCs more efficiently could lead to innovations in a variety of high-technology applications, from more efficient flexible solar cells to advanced display technologies, thereby contributing to advancements in sustainable energy and electronics.
Activities performed. COSY-PANTERA involved extensive experimental and computational studies focused on unravelling the mechanisms behind the formation of APC macrocycles through an unprecedented intramolecular cross-coupling event. These activities included:
a) Synthesis optimization. Development of optimized synthetic procedures to form APCs, particularly focusing on understanding the conditions that favor the formation of either 4- or 6-membered rings depending on the monomer design.
b) Electrochemical analysis. Detailed electrochemical analyses, including cyclic voltammetry (CV) and differential pulse voltammetry (DPV), were performed to understand the redox properties of synthesized macrocycles.
c) Spectroelectrochemical studies. Spectroelectrochemical (SEC) analyses were conducted to evaluate the electrochromic properties of selected macrocycles, demonstrating their potential in electrochromic devices.
Main achievements. Beyond the fundamental knowledge gained through these comprehensive studies, the following key achievements are summarized.
a) Discovery of new macrocyclic APCs. The project successfully synthesized numerous new APCs, which depending on the molecular design, produced either 4- or 6-membered rings as the most abundant species within each APC class.
b) Mechanistic understanding of the CTM process. Extensive experimental studies indicated that the CTM process is of living nature. Computational studies suggested that hydrogen-bond interactions play a key role in the formation of 5- and 6-membered ring APCs, whilst the kinetics of the reductive elimination step in the formation of APCs increase with ring size, hence, explaining the formation of larger rings.
c) Electrochromic color tuning. The APCs demonstrated promising electrochromic properties, with significant color changes observed under different applied potentials, making them potential candidates for electrochromic device applications, such as the proof-of-principle prototype ECDs made.
a) Synthesis optimization. Development of optimized synthetic procedures to form APCs, particularly focusing on understanding the conditions that favor the formation of either 4- or 6-membered rings depending on the monomer design.
b) Electrochemical analysis. Detailed electrochemical analyses, including cyclic voltammetry (CV) and differential pulse voltammetry (DPV), were performed to understand the redox properties of synthesized macrocycles.
c) Spectroelectrochemical studies. Spectroelectrochemical (SEC) analyses were conducted to evaluate the electrochromic properties of selected macrocycles, demonstrating their potential in electrochromic devices.
Main achievements. Beyond the fundamental knowledge gained through these comprehensive studies, the following key achievements are summarized.
a) Discovery of new macrocyclic APCs. The project successfully synthesized numerous new APCs, which depending on the molecular design, produced either 4- or 6-membered rings as the most abundant species within each APC class.
b) Mechanistic understanding of the CTM process. Extensive experimental studies indicated that the CTM process is of living nature. Computational studies suggested that hydrogen-bond interactions play a key role in the formation of 5- and 6-membered ring APCs, whilst the kinetics of the reductive elimination step in the formation of APCs increase with ring size, hence, explaining the formation of larger rings.
c) Electrochromic color tuning. The APCs demonstrated promising electrochromic properties, with significant color changes observed under different applied potentials, making them potential candidates for electrochromic device applications, such as the proof-of-principle prototype ECDs made.
From the wide variety of synthesized APCs selected examples were evaluated for their electrochromic properties, displaying reversible color transitions at different oxidation states. This indicated potential applications in electrochromic devices due to the large shifts in absorption spectra at low oxidation potentials (~1.5 V). Evaluation of their optical properties revealed that their luminescence characteristics (observed fluorescence quantum yields and molar absorption coefficients) differ significantly according to their molecular design. X-ray crystallography unambiguously confirmed the expected cyclic atomic connectivity and revealed their structural properties, e.g. showing how ring size and configuration influence molecular structure, such as bond angles and conformations. The synthetic CTM process was optimized, including various parameters like temperature, pre-catalysts, concentration, solvent, and reaction time. Overall, it was found that the CTM reaction could be carried out even under standard laboratory conditions with high yields, without compromising the quality of the obtained materials.
The development of the one-step catalyst-transfer macrocyclization (CTM) method represents a significant achievement in the synthesis of π-conjugated macrocyclic azaparacyclophanes (APCs). Their studied optoelectronic properties and their application in electrochromic devices (ECDs) as proof-of-concept highlight the value of this research, promising impactful advancements in both fundamental chemistry and technological innovation.
The development of the one-step catalyst-transfer macrocyclization (CTM) method represents a significant achievement in the synthesis of π-conjugated macrocyclic azaparacyclophanes (APCs). Their studied optoelectronic properties and their application in electrochromic devices (ECDs) as proof-of-concept highlight the value of this research, promising impactful advancements in both fundamental chemistry and technological innovation.