Imperial College London

Dr Florian Glöcklhofer

Faculty of Natural SciencesDepartment of Chemistry

Visiting Researcher
 
 
 
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Contact

 

f.glocklhofer Website

 
 
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Location

 

Molecular Sciences Research HubWhite City Campus

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Summary

 

Publications

Publication Type
Year
to

65 results found

Aitchison CM, Albrecht K, Awaga K, Cameron J, Data P, Fukazawa A, Glöcklhofer F, Ie Y, Luscombe CK, Marcilla R, Nakatsuka N, Nishide H, Schroeder BC, Singh M, Skabara P, Takeda Y, Tani Y, Uematsu T, Xie G, Yadav D, Yakiyama Yet al., 2024, Organic batteries: general discussion, Faraday Discussions, Vol: 250, Pages: 145-161, ISSN: 1359-6640

Journal article

Aitchison CM, Albrecht K, Awaga K, Cameron J, Data P, Glöcklhofer F, Guo X, Heeney M, Hudson ZM, Ie Y, Luscombe CK, Matsuo T, Nakanishi T, Nakatsuka N, Nishide H, Sasaki Y, Schroeder BC, Singh M, Skabara P, Takeda Y, Tani Y, Torsi L, Tsuchiya Y, Uematsu T, Yadav D, Yanai Net al., 2024, Organic neuromorphics and bioelectronics: general discussion, Faraday Discussions, Vol: 250, Pages: 83-95, ISSN: 1359-6640

Journal article

Aitchison CM, Albrecht K, Awaga K, Bergmann K, Calbo J, Cameron J, Clark J, Collins M, Data P, Dos Santos P, Fujigaya T, Fujino T, Fukazawa A, Glöcklhofer F, Guo X, Heeney M, Hudson ZM, Ie Y, Ishii W, Luscombe CK, Marcilla R, Matsuo T, Miyazaki S, Nakagawa S, Nakanishi T, Nakatsuka N, Nishide H, Sasaki Y, Schroeder BC, Singh M, Skabara P, Takeda Y, Tanaka Y, Tani Y, Tsuchiya Y, Tsutsui Y, Uematsu T, Xie G, Yanai Net al., 2024, Excitonic organic materials for photochemical and optoelectronic applications: general discussion, Faraday Discussions, Vol: 250, Pages: 298-334, ISSN: 1359-6640

Journal article

Ding B, Bhosale M, Bennett T, Heeney M, Plasser F, Esser B, Glöcklhofer Fet al., 2024, Reducing undesired solubility of squarephaneic tetraimide for use as an organic battery electrode material, Faraday Discussions, Vol: 250, Pages: 129-144, ISSN: 1359-6640

Locally aromatic alkyl-N-substituted squarephaneic tetraimide (SqTI) conjugated macrocycles are four-electron reducible, owing to global aromaticity and presumed global Baird aromaticity of the dianion and tetraanion states, respectively. However, their good solubility inhibits their application as a battery electrode material. By applying sidechain removal as a strategy to reduce SqTI solubility, we report the development of its unsubstituted derivative SqTI-H, which was obtained directly from squarephaneic tetraanhydride by facile treatment with hexamethyldisilazane and MeOH. Compared to alkyl-N-substituted SqTI-Rs, SqTI-H exhibited further improved thermal stability and low neutral state solubility in most common organic solvents, owing to computationally demonstrated hydrogen-bonding capabilities emanating from each imide position on SqTI-H. Reversible solid state electrochemical reduction of SqTI-H to the globally aromatic dianion state was also observed at -1.25 V vs. Fc/Fc+, which could be further reduced in two stages. Preliminary testing of SqTI-H in composite electrodes for lithium-organic half cells uncovered imperfect cycling performance, which may be explained by persistent solubility of reduced states, necessitating further optimisation of electrode fabrication procedures to attain maximum performance.

Journal article

Bennett TLR, Marsh AV, Turner JM, Plasser F, Heeney M, Glöcklhofer Fet al., 2023, Functionalisation of conjugated macrocycles with type I and II concealed antiaromaticity via cross-coupling reactions, Molecular Systems Design & Engineering, Vol: 8, Pages: 713-720, ISSN: 2058-9689

Conjugated macrocycles can exhibit concealed antiaromaticity; that is, despite not being antiaromatic, under specific circumstances, they can display properties typically observed in antiaromatic molecules due to their formal macrocyclic 4n π-electron system. Paracyclophanetetraene (PCT) and its derivatives are prime examples of macrocycles exhibiting this behaviour. In redox reactions and upon photoexcitation, they have been shown to behave like antiaromatic molecules (requiring type I and II concealed antiaromaticity, respectively), with such phenomena showing potential for use in battery electrode materials and other electronic applications. However, further exploration of PCTs has been hindered by the lack of halogenated molecular building blocks that would permit their integration into larger conjugated molecules by cross-coupling reactions. Here, we present two dibrominated PCTs, obtained as a mixture of regioisomers from a three-step synthesis, and demonstrate their functionalisation via Suzuki cross-coupling reactions. Optical, electrochemical, and theoretical studies reveal that aryl substituents can subtly tune the properties and behaviour of PCT, showing that this is a viable strategy in further exploring this promising class of materials.

Journal article

Wang Z, Hu Y, Xie Y, Qie F, Guo J, Zhang L, Shi C, Glöcklhofer F, Zhen Yet al., 2023, 1D slipped stacking microribbon-like crystals based on 6,13-dicyanopentacene for ambipolar charge transport, Science China Materials, Vol: 66, Pages: 2429-2435, ISSN: 2199-4501

Featuring small charge transport scattering, mesoscale size, and easy fabrication, one-dimensional self-assembled micro/nanomaterials (1D-MNMs) based on organic π-conjugated systems can be facilely incorporated into integrated microcircuits. Although tremendous progress has been made in 1D-MNMs based on p- or n-channel organic semiconductors, examples of lD-MNMs based on ambipolar organic semiconductors are scarce. Herein, we achieved a novel 1D-MNM based on 6,13-dicyanopentacene (DCP) with a 1D slipped stacking motif using the physical vapor transport method. The DCP-based 1D-MNM showed outstanding, well-balanced ambipolar charge transport with electron and hole mobilities of up to 0.34 and 0.38 cm2 V−1 s−1, respectively, which are among the best ambipolar transport characteristics of 1D-MNMs. Furthermore, a complementary inverter based on the ambipolar 1D-MNM of DCP was also constructed with a gain of up to 7, indicating potential application in organic logic circuits.

Journal article

Eder S, Ding B, Thornton DB, Sammut D, White AJP, Plasser F, Stephens IEL, Heeney M, Mezzavilla S, Glöcklhofer Fet al., 2022, Squarephaneic tetraanhydride: a conjugated square‐shaped cyclophane for the synthesis of porous organic materials, Angewandte Chemie International Edition, Vol: 61, Pages: 1-8, ISSN: 1433-7851

Aromatic carboxylic anhydrides are ubiquitous building blocks in organic materials chemistry and have received considerable attention in the synthesis of organic semiconductors, pigments, and battery electrode materials. Here we extend the family of aromatic carboxylic anhydrides with a unique new member, a conjugated cyclophane with four anhydride groups. The cyclophane is obtained in a three-step synthesis and can be functionalised efficiently, as shown by the conversion into tetraimides and an octacarboxylate. Crystal structures reveal the high degree of porosity achievable with the new building block. Excellent electrochemical properties and reversible reduction to the tetraanions are shown for the imides; NMR and EPR measurements confirm the global aromaticity of the dianions and evidence the global Baird aromaticity of the tetraanions. Considering the short synthesis and unique properties, we expect widespread use of the new building block in the development of organic materials.

Journal article

Eder S, Ding B, Thornton DB, Sammut D, White AJP, Plasser F, Stephens IEL, Heeney M, Mezzavilla S, Glöcklhofer Fet al., 2022, Squarephaneic Tetraanhydride: A Conjugated Square-Shaped Cyclophane for the Synthesis of Porous Organic Materials, Angewandte Chemie, Vol: 134, Pages: e202212623-e202212623, ISSN: 0044-8249

Aromatic carboxylic anhydrides are ubiquitous building blocks in organic materials chemistry and have received considerable attention in the synthesis of organic semiconductors, pigments, and battery electrode materials. Here we extend the family of aromatic carboxylic anhydrides with a unique new member, a conjugated cyclophane with four anhydride groups. The cyclophane is obtained in a three-step synthesis and can be functionalised efficiently, as shown by the conversion into tetraimides and an octacarboxylate. Crystal structures reveal the high degree of porosity achievable with the new building block. Excellent electrochemical properties and reversible reduction to the tetraanions are shown for the imides; NMR and EPR measurements confirm the global aromaticity of the dianions and evidence the global Baird aromaticity of the tetraanions. Considering the short synthesis and unique properties, we expect widespread use of the new building block in the development of organic materials.

Journal article

Rimmele M, Glöcklhofer F, Heeney M, 2022, Post-polymerisation approaches for the rapid modification of conjugated polymer properties, Materials Horizons, Vol: 9, Pages: 2678-2697, ISSN: 2051-6355

Post-polymerisation functionalisation provides a facile and efficient way for the introduction of functional groups on the backbone of conjugated polymers. Using post-polymerisation functionalisation approaches, the polymer chain length is usually not affected, meaning that the resulting polymers only differ in their attached functional groups or side chains, which makes them particularly interesting for investigating the influence of the different groups on the polymer properties. For such functionalisations, highly efficient and selective reactions are needed to avoid the formation of complex mixtures or permanent defects in the polymer backbone. A variety of suitable synthetic approaches and reactions that fulfil these criteria have been identified and reported. In this review, a thorough overview is given of the post-polymerisation functionalisations reported to date, with the methods grouped based on the type of reaction used: cycloaddition, oxidation/reduction, nucleophilic aromatic substitution, or halogenation and subsequent cross-coupling reaction. Instead of modifications on the aliphatic side chains of the conjugated polymers, we focus on modifications directly on the conjugated backbones, as these have the most pronounced effect on the optical and electronic properties. Some of the discussed materials have been used in applications, ranging from solar cells to bioelectronics. By providing an overview of this versatile and expanding field for the first time, we showcase post-polymerisation functionalisation as an exciting pathway for the creation of new conjugated materials for a range of applications.

Journal article

Eder S, Thornton DB, Ding B, Sammut D, White AJP, Plasser F, Stephens IEL, Heeney M, Mezzavilla S, Glöcklhofer Fet al., 2022, Squarephaneic Tetraanhydride: A Conjugated Square-Shaped Cyclophane for the Synthesis of Porous Organic Materials

<jats:p>Aromatic carboxylic anhydrides are ubiquitous building blocks in organic materials chemistry. In particular, dianhydrides and their conversion into imides have received considerable attention in the synthesis of organic semiconductors, pigments, and battery electrode materials. Here we extend the family of aromatic carboxylic anhydrides with a unique new member, a conjugated cyclophane with four anhydride groups. The cyclophane, named squarephaneic tetraanhydride due to its square shape, is obtained in a three-step synthesis; the anhydride groups are located at the corners and allow for efficient functionalisation, as shown by the conversion into imides and carboxylates. The crystal structures of the tetraanhydride and one of the imides demonstrate the high degree of porosity achievable with the new building block. Electrochemical measurements in solution and solid state are also presented. Considering the short synthesis and unique properties, we expect widespread use of the new building block in the development of organic materials.</jats:p>

Working paper

Pletzer M, Plasser F, Rimmele M, Heeney M, Glöcklhofer Fet al., 2022, [2.2.2.2]Paracyclophanetetraenes (PCTs): cyclic structural analogues of poly(p‑phenylene vinylene)s (PPVs), Open Research Europe, Vol: 1, Pages: 1-19, ISSN: 2732-5121

Background: Poly(p-phenylene vinylene)s (PPVs) and [2.2.2.2]paracyclophanetetraene (PCT) are both composed of alternating π-conjugated para-phenylene and vinylene units. However, while the former constitute a class of π-conjugated polymers that has been used in organic electronics for decades, the latter is a macrocycle that only recently revealed its potential for applications such as organic battery electrodes. The cyclic structure endows PCT with unusual properties, and further tuning of these may be required for specific applications. Methods: In this article, we adopt an approach often used for tuning the properties of PPVs, the introduction of alkoxy (or alkylthio) substituents at the phenylene units, for tuning the optoelectronic properties of PCT. The resulting methoxy- and methylthio-substituted PCTs, obtained by Wittig cyclisation reactions, are studied by UV-vis absorption, photoluminescence, and cyclic voltammetry measurements, and investigated computationally using the visualisation of chemical shielding tensors (VIST) method. Results: The measurements show that substitution leads to slight changes in terms of absorption/emission energies and redox potentials while having a pronounced effect on the photoluminescence intensity. The computations show the effect of the substituents on the ring currents and chemical shielding and on the associated local and global (anti)aromaticity of the macrocycles, highlighting the interplay of local and global aromaticity in various electronic states. Conclusions: The study offers interesting insights into the tuneability of the properties of this versatile class of π-conjugated macrocycles.

Journal article

Pletzer M, Plasser F, Rimmele M, Heeney M, Glöcklhofer Fet al., 2021, [2.2.2.2]Paracyclophanetetraenes (PCTs): cyclic structural analogues of poly(p‑phenylene vinylene)s (PPVs), Publisher: F1000Research

Background: Poly(p-phenylene vinylene)s (PPVs) and [2.2.2.2]paracyclophanetetraene (PCT) are both composed of alternating π-conjugated para-phenylene and vinylene units. However, while the former constitute a class of π-conjugated polymers that has been used in organic electronics for decades, the latter is a macrocycle that only recently revealed its potential for applications such as organic battery electrodes. The cyclic structure endows PCT with unusual properties, and further tuning of these may be required for specific applications. Methods: In this article, we adopt an approach often used for tuning the properties of PPVs, the introduction of alkoxy (or alkylthio) substituents at the phenylene units, for tuning the optoelectronic properties of PCT. The resulting methoxy- and methylthio-substituted PCTs, obtained by Wittig cyclisation reactions, are studied by UV-vis absorption, photoluminescence, and cyclic voltammetry measurements, and investigated computationally using the visualisation of chemical shielding tensors (VIST) method. Results: The measurements show that substitution leads to slight changes in terms of absorption/emission energies and redox potentials while having a pronounced effect on the photoluminescence intensity. The computations show the effect of the substituents on the ring currents and chemical shielding and on the associated local and global (anti)aromaticity of the macrocycles, highlighting the interplay of local and global aromaticity in various electronic states. Conclusions: The study offers interesting insights into the tuneability of the properties of this versatile class of π-conjugated macrocycles.

Working paper

Szakacs Z, Glocklhofer F, Plasser F, Vauthey Eet al., 2021, Excited-state symmetry breaking in 9,10-dicyanoanthracene-based quadrupolar molecules: the effect of donor-acceptor branch length, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 23, Pages: 15150-15158, ISSN: 1463-9076

Journal article

Rimmele M, Nogala W, Seif-Eddine M, Roessler M, Heeney M, Plasser F, Glöcklhofer Fet al., 2021, Functional group introduction and aromatic unit variation in a set of π‑conjugated macrocycles: revealing the central role of local and global aromaticity, Organic Chemistry Frontiers, Vol: 8, Pages: 4730-4745, ISSN: 2052-4110

π-Conjugated macrocycles are molecules with unique properties that are increasingly exploited for applications and the question of whether they can sustain global aromatic or antiaromatic ring currents is particularly intriguing. However, there are only a small number of experimental studies that investigate how the properties of π‑conjugated macrocycles evolve with systematic structural changes. Here, we present such a systematic experimental study of a set of [2.2.2.2]cyclophanetetraenes, all with formally Hückel antiaromatic ground states, and combine it with an in-depth computational analysis. The study reveals the central role of local and global aromaticity for rationalizing the observed optoelectronic properties, ranging from extremely large Stokes shifts of up to 1.6 eV to reversible fourfold reduction, a highly useful feature for charge storage/accumulation applications. A recently developed method for the visualization of chemical shielding tensors (VIST) is applied to provide unique insight into local and global ring currents occurring in different planes along the macrocycle. Conformational changes as a result of the structural variations can further explain some of the observations. The study contributes to the development of structure–property relationships and molecular design guidelines and will help to understand, rationalize, and predict the properties of other π‑conjugated macrocycles.

Journal article

Plasser F, Glöcklhofer F, 2021, Visualisation of chemical shielding tensors (VIST) to elucidate aromaticity and antiaromaticity, European Journal of Organic Chemistry, Vol: 2021, Pages: 2529-2539, ISSN: 1434-193X

Aromaticity is a central concept in chemistry, pervading areas from biochemistry to materials science. Recently, chemists also started to exploit intricate phenomena such as the interplay of local and global (anti)aromaticity or aromaticity in non‐planar systems and three dimensions. These phenomena pose new challenges in terms of our fundamental understanding and the practical visualisation of aromaticity. To overcome these challenges, a method for the visualisation of chemical shielding tensors (VIST) is developed here that allows for a 3D visualisation with quantitative information about the local variations and anisotropy of the chemical shielding. After exemplifying the method in different planar hydrocarbons, we study two non‐planar macrocycles to show the unique benefits of the VIST method for molecules with competing π‐conjugated systems and conclude with a norcorrole dimer showing clear evidence of through‐space aromaticity. We believe that the VIST method will be a highly valuable addition to the computational toolbox.

Journal article

Rimmele M, Nogala W, Seif-Eddine M, Roessler MM, Heeney M, Plasser F, Glöcklhofer Fet al., 2021, Functional Group Introduction and Aromatic Unit Variation in a Set of π-Conjugated Macrocycles: Revealing the Central Role of Local and Global Aromaticity

<jats:p>π-Conjugated macrocycles are molecules with unique properties that are increasingly exploited for applications and the question of whether they can sustain global aromatic or antiaromatic ring currents is particularly intriguing. However, there are only a small number of experimental studies that investigate how the properties of π-conjugated macrocycles evolve with systematic structural changes. Here, we present such a systematic experimental study of a set of [2.2.2.2]cyclophanetetraenes, all with formally Hückel antiaromatic ground states, and combine it with an in-depth computational analysis. The study reveals the central role of local and global aromaticity for rationalizing the observed optoelectronic properties, ranging from extremely large Stokes shifts of up to 1.6 eV to reversible fourfold reduction, a highly useful feature for charge storage/accumulation applications. A recently developed method for the visualization of chemical shielding tensors (VIST) is applied to provide unique insight into local and global ring currents occurring in different planes along the macrocycle. Conformational changes as a result of the structural variations can further explain some of the observations. The study contributes to the development of structure–property relationships and molecular design guidelines and will help to understand, rationalize, and predict the properties of other π-conjugated macrocycles.</jats:p>

Working paper

Rimmele M, Nogala W, Seif-Eddine M, Roessler MM, Heeney M, Plasser F, Glöcklhofer Fet al., 2021, Functional Group Introduction and Aromatic Unit Variation in a Set of π-Conjugated Macrocycles: Revealing the Central Role of Local and Global Aromaticity

<jats:p>π-Conjugated macrocycles are molecules with unique properties that are increasingly exploited for applications and the question of whether they can sustain global aromatic or antiaromatic ring currents is particularly intriguing. However, there are only a small number of experimental studies that investigate how the properties of π-conjugated macrocycles evolve with systematic structural changes. Here, we present such a systematic experimental study of a set of [2.2.2.2]cyclophanetetraenes, all with formally Hückel antiaromatic ground states, and combine it with an in-depth computational analysis. The study reveals the central role of local and global aromaticity for rationalizing the observed optoelectronic properties, ranging from extremely large Stokes shifts of up to 1.6 eV to reversible fourfold reduction, a highly useful feature for charge storage/accumulation applications. A recently developed method for the visualization of chemical shielding tensors (VIST) is applied to provide unique insight into local and global ring currents occurring in different planes along the macrocycle. Conformational changes as a result of the structural variations can further explain some of the observations. The study contributes to the development of structure–property relationships and molecular design guidelines and will help to understand, rationalize, and predict the properties of other π-conjugated macrocycles.</jats:p>

Working paper

Yoo D-J, Heeney M, Glocklhofer F, Choi JWet al., 2021, Tetradiketone macrocycle for divalent aluminium ion batteries, Nature Communications, Vol: 12, Pages: 1-9, ISSN: 2041-1723

Contrary to early motivation, the majority of aluminium ion batteries developed to date do not utilise multivalent ion storage; rather, these batteries rely on monovalent complex ions for their main redox reaction. This limitation is somewhat frustrating because the innate advantages of metallic aluminium such as its low cost and high air stability cannot be fully taken advantage of. Here, we report a tetradiketone macrocycle as an aluminium ion battery cathode material that reversibly reacts with divalent (AlCl2+) ions and consequently achieves a high specific capacity of 350 mAh g−1 along with a lifetime of 8000 cycles. The preferred storage of divalent ions over their competing monovalent counterparts can be explained by the relatively unstable discharge state when using monovalent AlCl2+ ions, which exert a moderate resonance effect to stabilise the structure. This study opens an avenue to realise truly multivalent aluminium ion batteries based on organic active materials, by tuning the relative stability of discharged states with carrier ions of different valence states.

Journal article

Kafourou P, Park B, Luke J, Tan L, Panidi J, Glöcklhofer F, Kim J, Anthopoulos TD, Kim J, Lee K, Kwon S, Heeney Met al., 2021, One‐step sixfold cyanation of benzothiadiazole acceptor units for air‐stable high‐performance n‐type organic field‐effect transistors, Angewandte Chemie, Vol: 133, Pages: 6035-6042, ISSN: 0044-8249

Reported here is a new high electron affinity acceptor end group for organic semiconductors, 2,1,3‐benzothiadiazole‐4,5,6‐tricarbonitrile (TCNBT). An n‐type organic semiconductor with an indacenodithiophene (IDT) core and TCNBT end groups was synthesized by a sixfold nucleophilic substitution with cyanide on a fluorinated precursor, itself prepared by a direct arylation approach. This one‐step chemical modification significantly impacted the molecular properties: the fluorinated precursor, TFBT IDT, a poor ambipolar semiconductor, was converted into TCNBT IDT, a good n‐type semiconductor. The electron‐deficient end group TCNBT dramatically decreased the energy of the highest occupied and lowest unoccupied molecular orbitals (HOMO/LUMO) compared to the fluorinated analogue and improved the molecular orientation when utilized in n‐type organic field‐effect transistors (OFETs). Solution‐processed OFETs based on TCNBT IDT exhibited a charge‐carrier mobility of up to μe≈0.15 cm2 V−1 s−1 with excellent ambient stability for 100 hours, highlighting the benefits of the cyanated end group and the synthetic approach.

Journal article

Heeney M, Kafourou P, Park B, Luke J, Luxi T, Panidi J, Glöcklhofer F, Kim J, Anthopoulos TD, Kim J-S, Lee K, Kwon Set al., 2021, One-step six-fold cyanation of benzothiadiazole acceptor Units for air-stable high-performance n-type organic field-effect transistors, Angewandte Chemie International Edition, Vol: 60, Pages: 5970-5977, ISSN: 1433-7851

We report a new high electron affinity acceptor end group for organic semiconductors, 2,1,3-benzothiadiazole-4,5,6-tricarbonitrile (TCNBT). An n-type organic semiconductor with an indacenodithiophene (IDT) core and TCNBT end groups was synthesized by a six-fold nucleophilic substitution with cyanides on a fluorinated precursor, itself prepared by a direct arylation approach. This one-step chemical modification was found to significantly impact the molecular properties: the fluorinated precursor, TFBT IDT, a poor ambipolar semiconductor, was converted into TCNBT IDT, a good n-type semiconductor. The highly electron-deficient end group TCNBT dramatically decreased the energy of the highest occupied and lowest unoccupied molecular orbitals (HOMO/LUMO) compared to the fluorinated analogue and improved the molecular orientation when utilized in n-type organic field-effect transistors (OFETs). Solution-processed OFETs based on TCNBT IDT exhibited a charge carrier mobility of up to µ e ≈ 0.15 cm 2 V -1 s -1 with excellent ambient stability for 100 hours, highlighting the benefits of the cyanated end group and the synthetic approach.

Journal article

Hodsden T, Thorley KJ, Basu A, White AJP, Wang C, Mitchell W, Glocklhofer F, Anthopoulos TD, Heeney Met al., 2021, The influence of alkyl group regiochemistry and backbone fluorination on the packing and transistor performance of N-cyanoimine functionalised indacenodithiophenes, Materials Advances, Vol: 2, Pages: 1706-1714

The synthesis of two novel n-type molecular organic semiconductors based on a fluorinated indacenodithiophene core in combination with an electron withdrawing N-cyanoimine group is reported, and the influence of the regiochemistry of the solubilizing sidechain is investigated. The N-cyanoimine is confirmed to be a strongly electron accepting group, which in combination with the core fluorination resulted in high electron affinities for both materials. Single crystal analysis demonstrated that whilst both materials arrange in ordered slipped stacks with close π–π stacking distances (∼3.40 Å), significant differences in electron transfer integrals for the two regioisomers were observed, relating to differences in relative molecular displacement along the π-stacking direction. Organic thin-film transistors fabricated via blade-coating displayed electron mobility up to 0.13 cm2 V−1 s−1 for the isomer with the larger transfer integral.

Journal article

Plasser F, Glöcklhofer F, 2021, Visualisation of Chemical Shielding Tensors (VIST) to Elucidate Aromaticity and Antiaromaticity

<jats:p>Aromaticity is a central concept in chemistry, pervading areas from biochemistry to materials science. Recently, chemists also started to exploit intricate phenomena such as the interplay of local and global (anti)aromaticity or aromaticity in non-planar systems and three dimensions. These phenomena pose new challenges in terms of our fundamental understanding and the practical visualisation of aromaticity. To overcome these challenges, a method for the visualisation of chemical shielding tensors (VIST) is developed here that allows for a 3D visualisation with quantitative information about the local variations and anisotropy of the chemical shielding. After exemplifying the method in different planar hydrocarbons, we study two non-planar macrocycles to show the unique benefits of the VIST method for molecules with competing pi-conjugated systems and conclude with a norcorrole dimer showing clear evidence of through-space aromaticity. We believe that the VIST method will be a highly valuable addition to the computational toolbox.</jats:p>

Working paper

Plasser F, Glöcklhofer F, 2021, Visualisation of Chemical Shielding Tensors (VIST) to Elucidate Aromaticity and Antiaromaticity

<jats:p>Aromaticity is a central concept in chemistry,pervading areas from biochemistry to materials science. Recently, chemists alsostarted to exploit intricate phenomena such as the interplay of local andglobal (anti)aromaticity or aromaticity in non-planar systems and threedimensions. These phenomena pose new challenges in terms of our fundamentalunderstanding and the practical visualisation of aromaticity. To overcome thesechallenges, a method for the visualisation of chemical shielding tensors (VIST)is developed here that allows for a 3D visualisation with quantitativeinformation about the local variations and anisotropy of the chemicalshielding. After exemplifying the method in different planar hydrocarbons, westudy two non-planar macrocycles to show the unique benefits of the VIST methodfor molecules with competing pi-conjugated systems and conclude with anorcorrole dimer showing clear evidence of through-space aromaticity. Webelieve that the VIST method will be a highly valuable addition to thecomputational toolbox.</jats:p>

Working paper

Plasser F, Glöcklhofer F, 2021, 3D Visualisation of Chemical Shielding Tensors (VIST) to Elucidate Aromaticity and Antiaromaticity

<jats:p>Aromaticity is a central concept in chemistry, pervading areas from biochemistry to materials science. Recently, synthetic chemists started to exploit more intricate phenomena such as the interplay of local and global (anti)aromaticity as well as aromaticity in non-planar systems and three dimensions. These phenomena pose new challenges in terms of our fundamental understanding and the practical visualisation of aromaticity, its local variations and anisotropy. To overcome these challenges, a method for the visualisation of chemical shielding tensors (VIST) is developed here. The VIST method is based on nucleus-independent chemical shifts but, in contrast to other methods, allows for a 3D visualisation with quantitative information about the local variations and anisotropy of the chemical shielding. The VIST method is exemplified in benzene to show its main properties, in phenanthrene to highlight various degrees of local aromaticity, and in cyclobuta[l]phenanthrene to illustrate the interplay between local aromaticity and antiaromaticity in its singlet ground state and Baird aromaticity in its triplet excited state.</jats:p><jats:p>Subsequently, the interplay of local and global aromaticity is investigated in two non-planar macrocycles, paracyclophanetetraene and [8]cycloparaphenylene, exemplifying the unique benefits of the VIST method for studying (anti)aromaticity in molecules with competing $\pi$-conjugated systems aligned in different planes.</jats:p><jats:p>Finally, a stacked norcorrole dimer is studied, showing clear evidence of through-space aromaticity. In summary, we believe that the VIST method will be a highly valuable addition to the computational toolbox of chemists studying (anti)aromaticity or considering it in their molecular design.</jats:p>

Working paper

Pletzer M, Plasser F, Rimmele M, Heeney M, Glöcklhofer Fet al., 2021, [2.2.2.2]Paracyclophanetetraenes (PCTs): cyclic structural analogues of poly(p‑phenylene vinylene)s (PPVs), Open Research Europe, Vol: 1, Pages: 111-111, ISSN: 2732-5121

<b>Background</b>: Poly( <i>p</i>-phenylene vinylene)s ( <b>PPV</b>s) and [2.2.2.2]paracyclophanetetraene ( <b>PCT</b>) are both composed of alternating π-conjugated <i>para</i>-phenylene and vinylene units. However, while the former constitute a class of π-conjugated polymers that has been used in organic electronics for decades, the latter is a macrocycle that only recently revealed its potential for applications such as organic battery electrodes. The cyclic structure endows <b>PCT</b> with unusual properties, and further tuning of these may be required for specific applications. <b>Methods</b>: In this article, we adopt an approach often used for tuning the properties of <b>PPV</b>s, the introduction of alkoxy (or alkylthio) substituents at the phenylene units, for tuning the optoelectronic properties of <b>PCT</b>. The resulting methoxy- and methylthio-substituted <b>PCT</b>s, obtained by Wittig cyclisation reactions, are studied by UV-vis absorption, photoluminescence, and cyclic voltammetry measurements, and investigated computationally using the visualisation of chemical shielding tensors (VIST) method. <b>Results</b>: The measurements show that substitution leads to slight changes in terms of absorption/emission energies and redox potentials while having a pronounced effect on the photoluminescence intensity. The computations show the effect of the substituents on the ring currents and chemical shielding and on the associated local and global (anti)aromaticity of the macrocycles, highlighting the interplay of local and global aromaticity in various electronic states. <b>Conclusions</b>: The study offers interesting insights into the tuneability of the properties of this versatile class of π-conjugated macrocycles.

Journal article

Wang S, Shaw J, Han Y, Fei Z, Glöcklhofer F, Heeney Met al., 2020, Multibranched aliphatic side chains for π-conjugated polymers with a high density of ‘unshielded’ aromatics, Chemical Communications, Vol: 56, Pages: 12138-12141, ISSN: 1359-7345

Strongly solubilising multibranched aliphatic side chains for π-conjugated polymers are reported, enabling soluble polymers with a high density of unsubstituted, ‘unshielded’ aromatics.

Journal article

Taublaender MJ, Mezzavilla S, Thiele S, Glöcklhofer F, Unterlass MMet al., 2020, Hydrothermale synthese von konjugierten polymeren am beispiel von pyrronpolymeren und polybenzimidazolen, Angewandte Chemie, Vol: 132, Pages: 15160-15171, ISSN: 0044-8249

Various polyimides and polyamides have recently been prepared by hydrothermal synthesis in nothing but H 2 O under high pressure and high temperature conditions. However, none of these polymers have a conjugated polymer backbone. We hereby report an extension of the synthetic scope of this simple and naturally environmentally friendly polymerisation technique to the production of conjugated polymers. Selected representatives of two different polymer classes, pyrron polymers and polybenzimidazoles, were synthesized hydrothermally. In addition to a mechanistic discussion of polymer formation, an electrochemical characterization of the most promising product is presented.

Journal article

Taublaender MJ, Mezzavilla S, Thiele S, Glöcklhofer F, Unterlass MMet al., 2020, Hydrothermal generation of conjugated polymers using the example of pyrrone polymers and polybenzimidazoles, Angewandte Chemie International Edition, Vol: 59, Pages: 15050-15060, ISSN: 1433-7851

Various polyimides and polyamides have recently been prepared via hydrothermal synthesis in nothing but H2 O under high-pressure and high-temperature conditions. However, none of the prepared polymers feature a truly conjugated polymer backbone. Here, we report on an expansion of the synthetic scope of this straightforward and inherently environmentally friendly polymerization technique to the generation of conjugated polymers. Selected representatives of two different polymer classes, pyrrone polymers and polybenzimidazoles, were generated hydrothermally. We present a mechanistic discussion of the polymer formation process as well as an electrochemical characterization of the most promising product.

Journal article

Taublaender MJ, Mezzavilla S, Thiele S, Glöcklhofer F, Unterlass MMet al., 2020, Back Cover: Hydrothermal Generation of Conjugated Polymers Using the Example of Pyrrone Polymers and Polybenzimidazoles (Angew. Chem. Int. Ed. 35/2020), Angewandte Chemie International Edition, Vol: 59, Pages: 15268-15268, ISSN: 1433-7851

Journal article

Taublaender MJ, Mezzavilla S, Thiele S, Glöcklhofer F, Unterlass MMet al., 2020, Hydrothermal Generation of Conjugated Polymers Using the Example of Pyrrone Polymers and Polybenzimidazoles, Angewandte Chemie, ISSN: 0044-8249

Journal article

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