Organic acids play an important role in atmospheric chemistry, particularly in the formation of aerosol particles. They are often detected with hydronium, ammonium, or nitrate chemical ionization sources, which are generally soft ionization sources but may cause fragmentation. Here we explore the reactivity of adipic acid, an analogue to the alpha-pinene oxidation product pinic acid, upon complexation with ammonium. Mass spectra and mass-selective vibrational spectra show that even mild activation, consistent with normal operation of an electrospray ionization source, yields (adipic acid)H+ and neutral ammonia. This is traced to a specific structural motif in which both protonated carboxylic acid carbonyl groups combine to form a site that is locally more basic than ammonia. Further mild collisional activation yields sequential loss of two water molecules, the known behavior of carboxylic acids in superacids, necessitating abstraction of at least one hydrogen from a CH group. Deuterium labeling experiments confirm that the second step indeed involves CH hydrogen atoms. Comparison of vibrational spectra and quantum chemical calculations allows us to assign structures for each step, identifying several ring structures but notably not forming the minimum energy structure upon the first loss of water. ESI of a range of linear dicarboxylic acids shows this to be a common feature of this class of organic acids. We propose a mechanism that explains this reactivity and discuss possible atmospheric implications of these observations.
有机酸在大气化学，特别是气溶胶粒子的形成中发挥着重要作用。它们通常用氢离子、铵或硝酸盐化学电离源进行检测，这些化学电离源通常是软电离源，但可能会导致碎裂。在此，我们探讨了己二酸（α-蒎烯氧化产物蒎酸的类似物）与铵络合后的反应性。质谱和质量选择性振动光谱显示，即使是与电喷雾电离源正常操作相一致的轻度活化，也会产生（己二酸）H+ 和中性氨。这可追溯到一种特殊的结构模式，其中质子化的两个羧酸羰基结合形成一个局部碱性高于氨的位点。进一步的温和碰撞活化产生了两个水分子的连续损失，这是已知的羧酸在超酸中的行为，需要从 CH 基团中抽取至少一个氢。氘标记实验证实，第二步确实涉及 CH 氢原子。通过比较振动光谱和量子化学计算，我们可以为每一步分配结构，确定几个环状结构，但值得注意的是，在第一次失水时没有形成最小能量结构。一系列线性二羧酸的 ESI 显示，这是这类有机酸的共同特征。我们提出了一种机制来解释这种反应性，并讨论了这些观察结果可能对大气产生的影响。
{"title":"Unusual Confinement-Induced Basicity and Proton-Mediated CH Activity of an Adipic Acid-Ammonium Cluster","authors":"Christopher, Johnson, John, Kreinbihl, Nicoline, Frederiks, Kathleen, Nickson, Emily, Racow, Melanie, Chiu, Annapoorani, Hariharan","doi":"10.26434/chemrxiv-2022-xqj08-v3","DOIUrl":"https://doi.org/10.26434/chemrxiv-2022-xqj08-v3","url":null,"abstract":"Organic acids play an important role in atmospheric chemistry, particularly in the formation of aerosol particles. They are often detected with hydronium, ammonium, or nitrate chemical ionization sources, which are generally soft ionization sources but may cause fragmentation. Here we explore the reactivity of adipic acid, an analogue to the alpha-pinene oxidation product pinic acid, upon complexation with ammonium. Mass spectra and mass-selective vibrational spectra show that even mild activation, consistent with normal operation of an electrospray ionization source, yields (adipic acid)H+ and neutral ammonia. This is traced to a specific structural motif in which both protonated carboxylic acid carbonyl groups combine to form a site that is locally more basic than ammonia. Further mild collisional activation yields sequential loss of two water molecules, the known behavior of carboxylic acids in superacids, necessitating abstraction of at least one hydrogen from a CH group. Deuterium labeling experiments confirm that the second step indeed involves CH hydrogen atoms. Comparison of vibrational spectra and quantum chemical calculations allows us to assign structures for each step, identifying several ring structures but notably not forming the minimum energy structure upon the first loss of water. ESI of a range of linear dicarboxylic acids shows this to be a common feature of this class of organic acids. We propose a mechanism that explains this reactivity and discuss possible atmospheric implications of these observations.","PeriodicalId":9813,"journal":{"name":"ChemRxiv","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Self-driving laboratories and automated experiments can accelerate the design workflow and decrease errors associated with experiments that characterize membrane transport properties. Within this study, we use 3D printing to design a custom stirred cell that incorporates inline conductivity probes in the retentate and permeate streams. The probes provide a complete trajectory of the salt concentrations as they evolve over the course of an experiment. Here, automated diafiltration experiments are used to characterize the performance of commercial NF90 and NF270 polyamide membranes over a predetermined range of KCl concentrations from 1-100 mM. The measurements obtained by the inline conductivity probes are validated using offline post-experiment analyses. Compared to traditional filtration experiments, the probes decrease the amount of time required for an experimentalist to characterize membrane materials by more than 50× and increase the amount of information generated by 100×. Device design principles to address the physical constraints associated with making conductivity measurements in confined volumes are proposed. Overall, the device developed within this study provides a foundation to establish high-throughput, automated membrane characterization techniques.
自动驾驶实验室和自动化实验可以加快设计工作流程，减少与表征膜传输特性的实验相关的误差。在这项研究中，我们使用 3D 打印技术设计了一个定制的搅拌池，在回流液和渗透液中加入了在线电导探针。探针可提供盐浓度在实验过程中演变的完整轨迹。在这里，自动重滤实验用于鉴定商用 NF90 和 NF270 聚酰胺膜在 1-100 mM 氯化钾浓度预定范围内的性能。在线电导探头获得的测量结果通过离线实验后分析进行了验证。与传统的过滤实验相比，该探头使实验人员表征膜材料所需的时间减少了 50 倍以上，所产生的信息量增加了 100 倍。针对在密闭体积内进行电导率测量的相关物理限制，提出了设备设计原则。总之，本研究开发的设备为建立高通量、自动化的膜表征技术奠定了基础。
{"title":"Automated Membrane Characterization: In-situ Monitoring of the Permeate and Retentate Solutions using a 3D Printed Permeate Probe Device","authors":"Jonathan, Ouimet, Faraj, Al-Badani, Xinhong, Liu, Laurianne, Lair, Zachary, Muetzel, Alexander, Dowling, William, Phillip","doi":"10.26434/chemrxiv-2024-31fl1-v2","DOIUrl":"https://doi.org/10.26434/chemrxiv-2024-31fl1-v2","url":null,"abstract":"Self-driving laboratories and automated experiments can accelerate the design workflow and decrease errors associated with experiments that characterize membrane transport properties. Within this study, we use 3D printing to design a custom stirred cell that incorporates inline conductivity probes in the retentate and permeate streams. The probes provide a complete trajectory of the salt concentrations as they evolve over the course of an experiment. Here, automated diafiltration experiments are used to characterize the performance of commercial NF90 and NF270 polyamide membranes over a predetermined range of KCl concentrations from 1-100 mM. The measurements obtained by the inline conductivity probes are validated using offline post-experiment analyses. Compared to traditional filtration experiments, the probes decrease the amount of time required for an experimentalist to characterize membrane materials by more than 50× and increase the amount of information generated by 100×. Device design principles to address the physical constraints associated with making conductivity measurements in confined volumes are proposed. Overall, the device developed within this study provides a foundation to establish high-throughput, automated membrane characterization techniques.","PeriodicalId":9813,"journal":{"name":"ChemRxiv","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-19DOI: 10.26434/chemrxiv-2024-f9bv7
Yinan, Xu, Samuel, Varner, Yezhi, Jin, Gustavo, Pérez-Lemus, Joan, Montes de Oca, Zhen-Gang, Wang, Juan, de Pablo
Water auto-ionization is critical in a wide range of chemical, biological, physical, and industrial processes. In this work, we describe a series of hitherto unknown collective molecular processes leading to auto-ionization. Specifically, by combining machine-learned interatomic potentials and spectral adaptive biasing force techniques, we determine the relevant free energy landscape of water auto-ionization. At ambient conditions, the free energy profile reveals two distinct saddle points, each leading to the formation of three- and four-member water wires. The wires feature an individual Zundel ion and a proton diffusion-like transition state, respectively. At elevated temperatures, the auto-ionization process exhibits a more concerted hydrogen transfer mechanism and reveals an alternative pathway involving the synchronous diffusion of Zundel ion pairs, with the ion pair corresponding to an energetic local minimum on the free energy surface. These findings help resolve long-standing conflicting views of the mechanism of water auto-ionization and provide new avenues for the study of proton behavior in different aqueous environments.
{"title":"Long Molecular Wires and the Auto-ionization of Water","authors":"Yinan, Xu, Samuel, Varner, Yezhi, Jin, Gustavo, Pérez-Lemus, Joan, Montes de Oca, Zhen-Gang, Wang, Juan, de Pablo","doi":"10.26434/chemrxiv-2024-f9bv7","DOIUrl":"https://doi.org/10.26434/chemrxiv-2024-f9bv7","url":null,"abstract":"Water auto-ionization is critical in a wide range of chemical, biological, physical, and industrial processes. In this work, we describe a series of hitherto unknown collective molecular processes leading to auto-ionization. Specifically, by combining machine-learned interatomic potentials and spectral adaptive biasing force techniques, we determine the relevant free energy landscape of water auto-ionization. At ambient conditions, the free energy profile reveals two distinct saddle points, each leading to the formation of three- and four-member water wires. The wires feature an individual Zundel ion and a proton diffusion-like transition state, respectively. At elevated temperatures, the auto-ionization process exhibits a more concerted hydrogen transfer mechanism and reveals an alternative pathway involving the synchronous diffusion of Zundel ion pairs, with the ion pair corresponding to an energetic local minimum on the free energy surface. These findings help resolve long-standing conflicting views of the mechanism of water auto-ionization and provide new avenues for the study of proton behavior in different aqueous environments.","PeriodicalId":9813,"journal":{"name":"ChemRxiv","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Temperature is a fundamental parameter in any chemical process, affecting reaction rates, selectivity, and more. Typically, chemists think of temperature as a homogeneous property, remaining unchanged throughout the reaction in space and time. Recently, photothermal materials have been emerging as an exciting tool opening new paths for innovative research, challenging the viewpoint described above. Herein, we develop a synthesis and in-situ assembly technique for metal-organic frameworks (MOFs) based on the distinct heterogeneous heating of photothermal materials under visible light. Notably, a simple cobalt chloride molecular complex was utilized as an efficient and stable light-to-heat converter for initial MOF formation. A thorough investigation of the assembly mechanism revealed the key role photothermal activation had in the formation of the superstructures. Finally, palladium nanoparticles (NP) were utilized as competing photothermal agents shedding light on the dynamics between different heat sources within a reaction and resulting in MOF-NP composites. This work highlights the versatility of the photothermal approach in the synthesis of advanced materials introducing a promising route to the micro/nano assembly of different materials.
{"title":"Molecular photothermal activation assisted synthesis, and orthogonal assembly of metal-organic-framework","authors":"Yossi, Weizmann, Aritra, Biswas, Nir, Lemcoff, Ofir, Shelonchik","doi":"10.26434/chemrxiv-2024-vmk13","DOIUrl":"https://doi.org/10.26434/chemrxiv-2024-vmk13","url":null,"abstract":"Temperature is a fundamental parameter in any chemical process, affecting reaction rates, selectivity, and more. Typically, chemists think of temperature as a homogeneous property, remaining unchanged throughout the reaction in space and time. Recently, photothermal materials have been emerging as an exciting tool opening new paths for innovative research, challenging the viewpoint described above. Herein, we develop a synthesis and in-situ assembly technique for metal-organic frameworks (MOFs) based on the distinct heterogeneous heating of photothermal materials under visible light. Notably, a simple cobalt chloride molecular complex was utilized as an efficient and stable light-to-heat converter for initial MOF formation. A thorough investigation of the assembly mechanism revealed the key role photothermal activation had in the formation of the superstructures. Finally, palladium nanoparticles (NP) were utilized as competing photothermal agents shedding light on the dynamics between different heat sources within a reaction and resulting in MOF-NP composites. This work highlights the versatility of the photothermal approach in the synthesis of advanced materials introducing a promising route to the micro/nano assembly of different materials.","PeriodicalId":9813,"journal":{"name":"ChemRxiv","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267382","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
By integrating different types of catalysts in the same system, hybrid catalysis emerges as an attractive and competitive approach. Within the framework of valorizing sustainably sourced bio-based products, we herein present a synthetic method for producing amides from alcohols and the bio-sourced 5-aminomethyl-2-furancarboxylic acid (AMFC). This approach utilizes supported gold metal nanoparticles as heterogeneous chemocatalysts, in conjunction with an acyl-coenzyme A ligase (ACL). By combining the actions of these catalysts, aliphatic mono- and di-alcohols are converted to the corresponding AMFC-derived amides with yields of up to 65% in aqueous buffer at 60 °C. This process requires only the addition of the enzyme and associated reactants in the same vessel for the second step in an one-pot/two-steps procedure.
通过在同一系统中整合不同类型的催化剂，混合催化技术成为一种极具吸引力和竞争力的方法。在对可持续来源的生物基产品进行价值评估的框架内，我们在此介绍一种从醇和生物来源的 5-aminomethyl-2-furancarboxylic acid (AMFC) 生产酰胺的合成方法。这种方法利用支撑金纳米金属颗粒作为异相化学催化剂，并与酰基辅酶 A 连接酶 (ACL) 结合使用。通过结合这些催化剂的作用，脂肪族一元醇和二元醇可在 60 °C 的水性缓冲液中转化为相应的 AMFC 衍生酰胺，产率高达 65%。该工艺只需在同一容器中加入酶和相关反应物，即可完成一锅/两步法的第二步。
{"title":"Hybrid synthesis of AMFC-derived amides using supported gold nanoparticles and acyl-coenzyme A ligases","authors":"Lucas, Bisel, Aurélie, Fossey-Jouenne, Richard, Martin, Jonathan, Bassut, Antoine, Lancien, Louis, Mouterde, Vivien, Herrscher, Muriel, Billamboz, Carine, Vergne-Vaxelaire, Rénato, Froidevaux, Anne, Zaparucha, Egon, Heuson","doi":"10.26434/chemrxiv-2024-2d7wr","DOIUrl":"https://doi.org/10.26434/chemrxiv-2024-2d7wr","url":null,"abstract":"By integrating different types of catalysts in the same system, hybrid catalysis emerges as an attractive and competitive approach. Within the framework of valorizing sustainably sourced bio-based products, we herein present a synthetic method for producing amides from alcohols and the bio-sourced 5-aminomethyl-2-furancarboxylic acid (AMFC). This approach utilizes supported gold metal nanoparticles as heterogeneous chemocatalysts, in conjunction with an acyl-coenzyme A ligase (ACL). By combining the actions of these catalysts, aliphatic mono- and di-alcohols are converted to the corresponding AMFC-derived amides with yields of up to 65% in aqueous buffer at 60 °C. This process requires only the addition of the enzyme and associated reactants in the same vessel for the second step in an one-pot/two-steps procedure.","PeriodicalId":9813,"journal":{"name":"ChemRxiv","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A novel molecular structure that merges the fields of molecular optical cycling with molecular photoswitching is presented. It is based on a photoswitching molecule azobenzene functionalized with one and two CaO- groups, which can act as optical cycling centers (OCCs). This paper characterizes the electronic structure of the resulting model systems, focusing on three questions: (1) how the electronic states of the photoswitch are impacted by a functionalization with an OCC; (2) how the states of the OCC are impacted by the scaffold of the photoswitch; (3) whether the OCC can serve as spectroscopic probe of isomerization. The experimental feasibility of the proposed design and the advantages that organic synthesis can offer in fur- ther functionalization of the molecular scaffold are also discussed. This work brings into the field of molecular optical cycling a new dimension of chemical complexity, intrinsic only to polyatomic molecules.
{"title":"Photoswitching molecules functionalized with optical cycling centers provide a novel platform for studying chemical transformations in ultracold molecules","authors":"Paweł, Wójcik, Taras , Khvorost, Guanming , Lao, Guozhu, Zhu, Antonio, Macias Jr, Justin, Caram, Wesley, Campbell, Miguel, García-Garibay, Eric, Hudson, Anastassia , Alexandrova, Anna, Krylov","doi":"10.26434/chemrxiv-2024-l71cj","DOIUrl":"https://doi.org/10.26434/chemrxiv-2024-l71cj","url":null,"abstract":"A novel molecular structure that merges the fields of molecular optical cycling with molecular photoswitching is presented. It is based on a photoswitching molecule azobenzene functionalized with one and two CaO- groups, which can act as optical cycling centers (OCCs). This paper characterizes the electronic structure of the resulting model systems, focusing on three questions: (1) how the electronic states of the photoswitch are impacted by a functionalization with an OCC; (2) how the states of the OCC are impacted by the scaffold of the photoswitch; (3) whether the OCC can serve as spectroscopic probe of isomerization. The experimental feasibility of the proposed design and the advantages that organic synthesis can offer in fur- ther functionalization of the molecular scaffold are also discussed. This work brings into the field of molecular optical cycling a new dimension of chemical complexity, intrinsic only to polyatomic molecules.","PeriodicalId":9813,"journal":{"name":"ChemRxiv","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The development of stable and tunable polycyclic aromatic compounds (PACs) is crucial for advancing organic optoelectronics. Conventional polycyclic aromatic hydrocarbons (PAHs), such as acenes, often suffer from poor stability due to photooxidation and oligomerization, which are linked to their frontier molecular orbital energy levels. To address these limitations, we have designed and synthesized a new class of π-expanded indoloindolizines by merging indole and indolizine moieties into a single polycyclic framework. Guided by the Glidewell-Lloyd rule—which predicts that in fused polycyclic systems, larger rings lose aromaticity in favor of smaller ones—we achieved precise modulation of the electronic structure by controlling the aromaticity of specific rings. Benzannulation at targeted positions allowed fine-tuning of the HOMO-LUMO gap, leading to distinct shifts in optoelectronic properties. We developed a scalable synthetic protocol to produce a wide range of π-expanded derivatives. The structural, electronic, and optical properties of these compounds were extensively characterized. Single-crystal X-ray diffraction confirmed their molecular structure, while theoretical calculations provided insights into the observed experimental trends. These indoloindolizines exhibit vivid colors and fluorescence across the visible spectrum, and their enhanced stability against photooxidation compared to acenes makes them promising candidates for practical applications in optoelectronic devices. Reactivity studies demonstrated high regioselectivity in electrophilic substitutions, highlighting the indole-like behavior of these compounds and opening avenues for further functionalization. Overall, our work establishes indoloindolizines as a promising platform for the development of stable, tunable organic materials for optoelectronic applications. By leveraging rational molecular design guided by the Glidewell-Lloyd rule, we offer a new pathway for molecular design in organic electronics, potentially enhancing device performance and longevity.
开发稳定、可调的多环芳烃化合物（PACs）对于推动有机光电子学的发展至关重要。传统的多环芳烃（PAHs），例如烯类，往往由于光氧化和低聚作用而导致稳定性差，这与其前沿分子轨道能级有关。为了解决这些局限性，我们通过将吲哚和吲嗪分子合并到一个单一的多环框架中，设计并合成了一类新的π-扩展吲哚吲嗪类化合物。根据格莱德韦尔-劳埃德（Glidewell-Lloyd）规则的预测，在融合多环体系中，较大的环会失去芳香性，而较小的环则具有芳香性，因此我们通过控制特定环的芳香性实现了对电子结构的精确调节。在目标位置进行苯并氮化可对 HOMO-LUMO 间隙进行微调，从而使光电特性发生明显变化。我们开发了一种可扩展的合成方案，以生产各种 π 扩展衍生物。我们对这些化合物的结构、电子和光学特性进行了广泛表征。单晶 X 射线衍射证实了它们的分子结构，而理论计算则为观察到的实验趋势提供了见解。这些吲哚吲哚嗪类化合物在可见光谱范围内表现出鲜艳的色彩和荧光，而且与烯类化合物相比，它们的光氧化稳定性更强，因此有望在光电设备中得到实际应用。反应研究表明，亲电取代具有很高的区域选择性，突出了这些化合物的类吲哚行为，并为进一步官能化开辟了途径。总之，我们的工作为开发稳定、可调的光电应用有机材料提供了一个前景广阔的平台。通过利用以 Glidewell-Lloyd 规则为指导的合理分子设计，我们为有机电子学的分子设计提供了一条新的途径，从而有可能提高器件的性能和寿命。
{"title":"Design, Synthesis, and Optoelectronic Properties of π-Expanded Indoloindolizines.","authors":"Przemysław, Gaweł, Abhishek, Pareek, Muhammad Yasir , Mehboob, Maciej, Majdecki, Hubert, Szabat, Piotr, Połczyński, Cina, Foroutan-Nejad, Maja, Morawiak","doi":"10.26434/chemrxiv-2024-q9j9k","DOIUrl":"https://doi.org/10.26434/chemrxiv-2024-q9j9k","url":null,"abstract":"The development of stable and tunable polycyclic aromatic compounds (PACs) is crucial for advancing organic optoelectronics. Conventional polycyclic aromatic hydrocarbons (PAHs), such as acenes, often suffer from poor stability due to photooxidation and oligomerization, which are linked to their frontier molecular orbital energy levels. To address these limitations, we have designed and synthesized a new class of π-expanded indoloindolizines by merging indole and indolizine moieties into a single polycyclic framework. Guided by the Glidewell-Lloyd rule—which predicts that in fused polycyclic systems, larger rings lose aromaticity in favor of smaller ones—we achieved precise modulation of the electronic structure by controlling the aromaticity of specific rings. Benzannulation at targeted positions allowed fine-tuning of the HOMO-LUMO gap, leading to distinct shifts in optoelectronic properties. We developed a scalable synthetic protocol to produce a wide range of π-expanded derivatives. The structural, electronic, and optical properties of these compounds were extensively characterized. Single-crystal X-ray diffraction confirmed their molecular structure, while theoretical calculations provided insights into the observed experimental trends. These indoloindolizines exhibit vivid colors and fluorescence across the visible spectrum, and their enhanced stability against photooxidation compared to acenes makes them promising candidates for practical applications in optoelectronic devices. Reactivity studies demonstrated high regioselectivity in electrophilic substitutions, highlighting the indole-like behavior of these compounds and opening avenues for further functionalization. Overall, our work establishes indoloindolizines as a promising platform for the development of stable, tunable organic materials for optoelectronic applications. By leveraging rational molecular design guided by the Glidewell-Lloyd rule, we offer a new pathway for molecular design in organic electronics, potentially enhancing device performance and longevity.","PeriodicalId":9813,"journal":{"name":"ChemRxiv","volume":"110 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-19DOI: 10.26434/chemrxiv-2024-2pdt3
Stephanie L., Wunder, Tutan Das, Aka, Thomas, Boller, Graham, Dobereiner
Perfluorinated alkyl substances (PFAS) are important environmental hazards that enter microorganisms and animal tissues via their cellular membranes, where they bind to both proteins and lipids1. The interaction of a prevalent PFAS, perfluorooctane sulfonic acid (PFOS), with a model cell membrane composed of dipalmitoyl phosphatidylcholine (DPPC) was investigated as a function of molar ratio of DPPC/PFOS in both multilamellar vesicles (MLVs) and large unilamellar vesicles (LUVs). The PFOS was both prepared and incubated with the vesicles and its incorporation into the LUVs and MLVs was monitored by nano- differential scanning calorimetry (for phase transition temperatures, Tm) and by dynamic light scattering (DLS) or optical microscopy for size. For MLVs and LUVs prepared with PFOS, no pretransition was observed. The LUVs and MLVs remained intact for up to 30 days with sizes ~ 100nm for LUVs and ~ 10-100 μm for MLVs. At DPPC/PFOS ~ 75/1 to 7.5/1, there was a single Tm, that decreased and broadened as the DPPC/PFOS molar ratio decreased, as previously observed.2 At higher PFOS concentrations, DPPC/PFOS < 5/1, two or three phase transitions were observed, with one Tm at a temperature close to that of the neat MLVs/LUVs and one at lower temperature. This was interpreted as phase separation into PFOS rich and PFOS poor domains. When MLVs were incubated with PFOS, both the main (Tm) and pretransition (Tpre), characteristic of neat DPPC, were observed, indicating the presence of bilayers with no incorporated PFOS. The intensity of Tm decreased with increased time, temperature (i.e. faster above than below Tm) and the external PFAS concentration, and Tpre increased (T = Tm - Tpre decreased). Concurrently, a phase transition in the MLVs at lower temperature was observed and disappeared with time. These results indicate that there was progressive penetration of the PFOS from the outer leaflets (that had incorporated PFOS) to the interior bilayers (that had no incorporated PFOS) of the MLVs, and by implication that there was passive diffusion of PFOS across (not just into) the DPPC bilayers, which occurred more quickly above than below Tm. While diffusion of PFOS across cellular membranes has previously been observed, this effect has been attributed to association with membrane proteins.
{"title":"Phase Separation and Passive Diffusion of Perfluorooctane Sulfonic Acid (PFOS) in Multilamellar and Unilamellar Vesicles","authors":"Stephanie L., Wunder, Tutan Das, Aka, Thomas, Boller, Graham, Dobereiner","doi":"10.26434/chemrxiv-2024-2pdt3","DOIUrl":"https://doi.org/10.26434/chemrxiv-2024-2pdt3","url":null,"abstract":"Perfluorinated alkyl substances (PFAS) are important environmental hazards that enter microorganisms\u0000and animal tissues via their cellular membranes, where they bind to both proteins and lipids1. The\u0000interaction of a prevalent PFAS, perfluorooctane sulfonic acid (PFOS), with a model cell membrane\u0000composed of dipalmitoyl phosphatidylcholine (DPPC) was investigated as a function of molar ratio of\u0000DPPC/PFOS in both multilamellar vesicles (MLVs) and large unilamellar vesicles (LUVs). The PFOS was both\u0000prepared and incubated with the vesicles and its incorporation into the LUVs and MLVs was monitored by\u0000nano- differential scanning calorimetry (for phase transition temperatures, Tm) and by dynamic light\u0000scattering (DLS) or optical microscopy for size. For MLVs and LUVs prepared with PFOS, no pretransition\u0000was observed. The LUVs and MLVs remained intact for up to 30 days with sizes ~ 100nm for LUVs and ~\u000010-100 μm for MLVs. At DPPC/PFOS ~ 75/1 to 7.5/1, there was a single Tm, that decreased and broadened\u0000as the DPPC/PFOS molar ratio decreased, as previously observed.2 At higher PFOS concentrations,\u0000DPPC/PFOS < 5/1, two or three phase transitions were observed, with one Tm at a temperature close to\u0000that of the neat MLVs/LUVs and one at lower temperature. This was interpreted as phase separation into\u0000PFOS rich and PFOS poor domains. When MLVs were incubated with PFOS, both the main (Tm) and\u0000pretransition (Tpre), characteristic of neat DPPC, were observed, indicating the presence of bilayers with\u0000no incorporated PFOS. The intensity of Tm decreased with increased time, temperature (i.e. faster above\u0000than below Tm) and the external PFAS concentration, and Tpre increased (T = Tm - Tpre decreased).\u0000Concurrently, a phase transition in the MLVs at lower temperature was observed and disappeared with\u0000time. These results indicate that there was progressive penetration of the PFOS from the outer leaflets\u0000(that had incorporated PFOS) to the interior bilayers (that had no incorporated PFOS) of the MLVs, and by\u0000implication that there was passive diffusion of PFOS across (not just into) the DPPC bilayers, which\u0000occurred more quickly above than below Tm. While diffusion of PFOS across cellular membranes has\u0000previously been observed, this effect has been attributed to association with membrane proteins.","PeriodicalId":9813,"journal":{"name":"ChemRxiv","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267369","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-19DOI: 10.26434/chemrxiv-2024-q6ssd
Rana , Kiani, Huiying , Sheng, Timo, Held, Oliver , Löhmann, Sebastian , Risse, Pouya, Partovi-Azar, Daniel, Sebastiani
Sulfur/carbon copolymers have emerged as a promising alternative for conventional crystalline sulfur cathodes for lithium-sulfur batteries. Among these, sulfur–n–1,3– diisopropenylbenzene (S/DIB) copolymers, which present a network of DIB molecules interconnected via sulfur chains, have particularly shown a good performance and, there- fore, have been under intensive experimental and theoretical investigations. However, their structural complexity and flexibility have hindered a clear understanding of their structural evolution during redox reactions at an atomistic level. Here, by performing state-of-the-art finite-temperature ab initio Raman spectroscopy simulations, we inves- tigate the spectral fingerprints of S/DIB copolymers during consecutive reactions with lithium. We discuss in detail Raman spectral changes in particular frequency ranges which are common in S/DIB copolymers having short sulfur chains and those consisting of longer ones. We also highlight those distinctive spectroscopic fingerprints specific to local S/DIB structures containing only short or long sulfur chains. This distinction could serve to help distinguish between them experimentally. Our theoretically predicted results are in a good agreement with experimental Raman measurements on coin cells at different discharge stages. This work represents, for the first time, an attempt to compute operando Raman spectra using quantum-chemical calculations and provides a guideline for Raman spectral changes of arbitrary electrodes during the discharge.
{"title":"Toward Ab initio Simulation of Operando Raman Spectroscopy: Application to Sulfur/Carbon Copolymer Cathodes in Li-S Batteries","authors":"Rana , Kiani, Huiying , Sheng, Timo, Held, Oliver , Löhmann, Sebastian , Risse, Pouya, Partovi-Azar, Daniel, Sebastiani","doi":"10.26434/chemrxiv-2024-q6ssd","DOIUrl":"https://doi.org/10.26434/chemrxiv-2024-q6ssd","url":null,"abstract":"Sulfur/carbon copolymers have emerged as a promising alternative for conventional crystalline sulfur cathodes for lithium-sulfur batteries. Among these, sulfur–n–1,3– diisopropenylbenzene (S/DIB) copolymers, which present a network of DIB molecules interconnected via sulfur chains, have particularly shown a good performance and, there- fore, have been under intensive experimental and theoretical investigations. However, their structural complexity and flexibility have hindered a clear understanding of their structural evolution during redox reactions at an atomistic level. Here, by performing state-of-the-art finite-temperature ab initio Raman spectroscopy simulations, we inves- tigate the spectral fingerprints of S/DIB copolymers during consecutive reactions with lithium. We discuss in detail Raman spectral changes in particular frequency ranges which are common in S/DIB copolymers having short sulfur chains and those consisting of longer ones. We also highlight those distinctive spectroscopic fingerprints specific to local S/DIB structures containing only short or long sulfur chains. This distinction could serve to help distinguish between them experimentally. Our theoretically predicted results are in a good agreement with experimental Raman measurements on coin cells at different discharge stages. This work represents, for the first time, an attempt to compute operando Raman spectra using quantum-chemical calculations and provides a guideline for Raman spectral changes of arbitrary electrodes during the discharge.","PeriodicalId":9813,"journal":{"name":"ChemRxiv","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-19DOI: 10.26434/chemrxiv-2024-9091h-v2
Giuseppe Maria Junior, Barca, Calum, Snowdon
Second-order Møller-Plesset perturbation theory (MP2) using the Resolution of the Identity approximation (RI-MP2) is a widely used method for computing molecular energies beyond the Hartree-Fock mean-field approximation. However, its high computational cost and lack of efficient algorithms for modern supercomputing architectures limit its applicability to large molecules. In this paper, we present the first distributed-memory many-GPU RI-MP2 algorithm explicitly designed to utilize hundreds of GPU accelerators for every step of the computation. Our novel algorithm achieves near-peak performance on GPU-based supercomputers through the development of a distributed memory algorithm for forming RI-MP2 intermediate tensors with zero inter-node communication, except for a single O(N^2) asynchronous broadcast, and a distributed memory algorithm for the O(N^5) energy reduction step, capable of sustaining near-peak performance on clusters with several hundred GPUs. Comparative analysis shows our implementation outperforms state-of-the-art quantum chemistry software by over 3.5 times in speed while achieving an eightfold reduction in computational power consumption. Benchmarking on the Perlmutter supercomputer, our algorithm achieves 11.8 PFLOP/s (83% of peak performance) performing and the RI-MP2 energy calculation on a 314-water cluster with 7,850 primary and 30,144 auxiliary basis functions in 4 minutes on 180 nodes and 720 A100 GPUs. This performance represents a substantial improvement over traditional CPU-based methods, demonstrating significant time-to-solution and power consumption benefits of leveraging modern GPU-accelerated computing environments for quantum chemistry calculations.
{"title":"An Efficient RI-MP2 Algorithm for Distributed Many-GPU Architectures","authors":"Giuseppe Maria Junior, Barca, Calum, Snowdon","doi":"10.26434/chemrxiv-2024-9091h-v2","DOIUrl":"https://doi.org/10.26434/chemrxiv-2024-9091h-v2","url":null,"abstract":"Second-order Møller-Plesset perturbation theory (MP2) using the Resolution of the Identity approximation (RI-MP2) is a widely used method for computing molecular energies beyond the Hartree-Fock mean-field approximation. However, its high computational cost and lack of efficient algorithms for modern supercomputing architectures limit its applicability to large molecules. In this paper, we present the first distributed-memory many-GPU RI-MP2 algorithm explicitly designed to utilize hundreds of GPU accelerators for every step of the computation. Our novel algorithm achieves near-peak performance on GPU-based supercomputers through the development of a distributed memory algorithm for forming RI-MP2 intermediate tensors with zero inter-node communication, except for a single O(N^2) asynchronous broadcast, and a distributed memory algorithm for the O(N^5) energy reduction step, capable of sustaining near-peak performance on clusters with several hundred GPUs. Comparative analysis shows our implementation outperforms state-of-the-art quantum chemistry software by over 3.5 times in speed while achieving an eightfold reduction in computational power consumption. Benchmarking on the Perlmutter supercomputer, our algorithm achieves 11.8 PFLOP/s (83% of peak performance) performing and the RI-MP2 energy calculation on a 314-water cluster with 7,850 primary and 30,144 auxiliary basis functions in 4 minutes on 180 nodes and 720 A100 GPUs. This performance represents a substantial improvement over traditional CPU-based methods, demonstrating significant time-to-solution and power consumption benefits of leveraging modern GPU-accelerated computing environments for quantum chemistry calculations.","PeriodicalId":9813,"journal":{"name":"ChemRxiv","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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