Functional Organic Materials Research Articles

Pd‐Catalyzed Cyclization of Alkynyl Norbornene Derivatives for the Synthesis of Benzofused Heteroarenes

AbstractModular approaches, which allow a systematic variation of heteroaromatic cores and substituents, are crucial for the development of heteroaromatic drug candidates and organic functional materials. A new strategy involving the cyclization of heteroarenes tethered with alkynes through a norbornene bridge was developed. The precursors were readily prepared by a three‐component coupling process of heteroaryl halides, norbornadiene, and terminal alkynes. The Pd catalytic system derived from Pd(OAc)2and 2‐(pyrazol‐1‐yl)pyridine transformed a variety of five‐membered heteroarenes to the corresponding benzofused products, including (di)benzothiophene, indazole, carbazole, indole, and benzofuran, with aryl and alkyl substituents at the C4(C7) position. During the cyclization process, the norbornene ring underwent a retro‐Diels‐Alder reaction, serving as an acetylene synthon. This approach was used to synthesize naphthalene derivatives from electron‐rich arenes, demonstrating its versatility in the annulation of (hetero)aromatic rings.magnified image

Vibratile Dihydrophenazines with Controllable Luminescence Enabled by Precise Regulation of π-Conjugated Wings

Vibratile Dihydrophenazines with Controllable Luminescence Enabled by Precise Regulation of π-Conjugated Wings

Preface

The 2021 7th International Conference on Advances in Energy, Environment and Chemical Engineering (AEECE 2021) was to be held in Chengdu, China during July 9-11, 2021. The idea of the conference is for the scientists, scholars, engineers and students from the Universities all around the world and the industry to present ongoing research activities, and hence to foster research relations between the Universities and the industry. AEECE 2021 will keep promoting the information exchange on Energy, Environment and Chemical Engineering, which aims to promote international academic exchange and international cooperation, and provides an opportunity for researchers around the world to exchange ideas and latest research results, in both theory and application of Energy, Environment and Chemical Engineering.The conference model was divided into two sessions, including oral presentations and keynote speeches. In the first part, some scholars, whose submissions were selected as the excellent papers, were given 15 minutes to perform their oral presentations one by one. Then in the second part, keynote speakers were each allocated 30-45 minutes to hold their speeches. In this conference, we were greatly honored to have invited three elites as our Conference Chair. There were over 90 experts and scholars in the area of Energy, Environment and Chemical Engineering representing different famous universities and institutes around the globe to attend the conference.During the conference, we were pleased to invite five distinguished experts to present their insightful speeches. Prof.Lei Guo, our first keynote speaker, from Tongren University, China. He has conducted a series of studies in various areas such as electrochemistry, organic chemistry, corrosion science, as well as theoretical simulations. Prof. Wenjie Liao, from Sichuan University, China. He had outstanding research in Coupled human-environment systems, Industrial ecology, Life cycle assessment, Energy and environmental policy analysis. Prof. Kew-Yu Chen, from Feng Chia University, Taiwan, China. He devoted to Functional organic small molecule materials and other related research area. Prof. Mohammad Dalour Hossen Beg, from Universiti Malaysia, Pahang, Malaysia. His major research area is Polymer and Composites. Prof. Dongfang Yang, our finale keynote speaker, from Guizhou Minzu University, China. His research area: Environment, Ecology, Bio-geochemistry, Materials Science and Engineering.The participants of the conference were from most part of the world, with background of either academia or industry, even well-known enterprise. The success and prosperity of the conference is reflected high level of the papers received. The proceedings are a compilation of the accepted papers and represent an interesting outcome of the conference. AEECE 2021 for exchange of research findings, analysis, information and knowledge in areas which include but are not limited to: Energy Science and Engineering, Chemical Engineering and Technology, Environmental Science and Environmental Engineering and other related topics.We would like to acknowledge all of those who supported AEECE 2021. Each individual and institutional help are very important for the success of this conference. Especially we would like to thank the organizing committee for their valuable advices in the organization and helpful peer review of the papers. We sincerely hope that AEECE 2021 will be a forum for excellent discussions that will put forward new ideas and promote collaborative researches. We are sure that the proceedings will serve as an important research source of references and the knowledge, which will lead to not only scientific and engineering progress but also other new products and processes.The Committee of AEECE 2021List of Committee member are available in this pdf

Investigation of mesomorphic, photophysical and gelation behavior in aroylhydrazone based liquid crystals: Observation of mesophase crossover phenomena

Five series of substituted aroylhydrazones having two alkoxy chains at 3- and 5- positions at amide end of the molecule have been synthesized; wherein each series differ from each other in terms of number and position of alkoxy chains at imine end. The compounds of first series with the single alkoxy chain at 4-position at imine end self-assembled into columnar hexagonal mesophase. The lower homologues of the series with alkoxy chains at 3- and 5- positions at imine end showed a transition from columnar hexagonal to columnar rectangular mesophase in cooling cycle while the higher homologues exhibited columnar hexagonal mesophase. The series with alkoxy chains at 3- and 4- positions exhibited columnar rectangular mesophase. All the homologues of series with alkoxy chains at 2-, 3- and 4- positions showed a transition from columnar rectangular to columnar oblique mesophase in cooling cycle. The series with alkoxy chains at 3-, 4- and 5- positions exhibited transition in columnar hexagonal mesophase. The mesophase crossover from one columnar mesophase to the other was found to be dependent on the chain length as well as on the temperature during the self-assembly process in these molecules. The temperature dependent columnar mesophase crossover has been observed for the first time in these systems. The substitution pattern showed an influence on the photophysical properties. The number and position of alkoxy chains played a critical role in the formation of gel in these molecules. These liquid crystalline gelators have application potential in organic optoelectronic functional materials and devices.

Silicon Compounds in Sponges

A comparative study of the microscopic morphology and chemical characteristics of spicules of Hexactinellids (Hexactinellida) with different structural features of the skeletons, as well as the freshwater Baikal sponge belonging to the class of common sponges (Demospongia), was carried out. The trace element composition of sponge spicules was determined by X-ray fluorescence spectrometry. The spicules of siliceous sponges contain many elements, arranged in decreasing order of concentration: Si, Ca, Fe, Cl, K, Zn, and others. It was shown that the surface layer of sea sponges contains mainly carbon (C), oxygen (O), and to a lesser extent nitrogen (N), silicon (Si), and sodium (Na). The spicules of the studied siliceous sponges can be divided into two groups according to the phase composition, namely one containing crystalline calcium compounds and one without them. Analysis of infrared absorption spectra allows us to conclude that the sponges Euplectella aspergillum, E. suberia and Dactylocalyx sp. contain silica partially bound to the organic matrix, while the silica skeleton of the sponges of the other group (Schulzeviella gigas, Sericolophus sp., Asconema setubalense, Sarostegia oculata, Farrea sp. and Lubomirskia baicalensis sp.) practically does not differ from the precipitated SiO2. This comparative study of the chemical composition of the skeletons of marine Hexactinellids and common freshwater sponge allows us to conclude that there are no fundamental differences in the chemical composition of spicules, and all of them can be used as a starting material for creating new composite silicon–organic functional materials.

An Update on Cyclohepta[b]indoles

AbstractThe cyclohepta[b]indole scaffold constitutes a salient structural motif in natural products as well as in men‐made pharmaceutically active ingredients. Cyclohepta[b]indoles consist of an indole nucleus fused to a seven‐membered carbacycle. Interest in cyclohepta[b]indole chemistry originates from natural product chemistry and medicinal chemistry. The chemistry of cyclohepta[b]indole‐based organic functional materials may be a research area with some potential. The state of the art of cyclohepta[b]indoloid chemism has been comprehensively and scholarly summarized by the leading review article of Stempel and Gaich in 2016. Following this lead, our Minireview covers the literature from 2016 to 2021.

S/Se-embedded acenaphthylene-imide-containing polycyclic heteroaromatic hydrocarbon

Acenapththylene-imide (AnI), similar to naphthalene diimide (NDI), is an outstanding building block for organic functional materials and has gained a lot of research attention. Herein, Sulphur and Selenium-embedded AnI-containing polycyclic aromatic hydrocarbon molecules, AnI-SQ and AnI-SeQ, with [1,2,5]thiadiazolo[3,4-g]quinoxaline (SQ) and [1,2,5]selenadiazolo[3,4-g]quinoxaline (SeQ) are designed and synthesized with low-lying LUMO energy levels. The absorption and emission of AnI-SQ and AnI-SeQ displayed a bathochromic shift upon protonation of the C = N bond. Besides, theoretical calculation indicates remarkable rigid planar backbones for both AnI-SQ and AnI-SeQ. Through self-assembly with polymeric Pluronic® F-127, corresponding hydrophilic nanoparticles (NPs) were prepared with low cytotoxicity. And AnI-SQ NPs could be applied for in vitro two-photon fluorescence imaging.

4]Cyclo-N-alkyl-2,7-carbazoles: Influence of the Alkyl Chain Length on the Structural, Electronic, and Charge Transport Properties.

Macrocycles possessing radially oriented π-orbitals have experienced a fantastic development. However, their incorporation in organic electronic devices remains very scarce. In this work, we aim at bridging the gap between organic electronics and nanorings by reporting the first detailed structure-properties-device performance relationship study of organic functional materials based on a nanoring system. Three [4]cyclo-N-alkyl-2,7-carbazoles bearing different alkyl chains on their nitrogen atoms have been synthesized and characterized by combined experimental and theoretical approaches. This study includes electrochemical, photophysical, thermal, and structural solid-state measurements and charge transport properties investigations. An optimized protocol of the Pt approach has been developed to synthesize the [4]cyclocarbazoles in high yield (52-64%), of great interest for further development of nanorings, especially in materials science. The charge transport properties of [4]cyclocarbazoles and model compound [8]cycloparaphenylene ([8]CPP) have been studied. Although no field effect (FE) mobility was recorded for the benchmark [8]CPP, FE mobility values of ca. 10-5 cm2·V-1·s-1 were recorded for the [4]cyclocarbazoles. The characteristics (threshold voltage VTH, subthreshold swing SS, trapping energy ΔE) recorded for the three [4]cyclocarbazoles appear to be modulated by the alkyl chain length borne by the nitrogen atoms. Remarkably, the space-charge-limited current mobilities measured for the [4]cyclocarbazoles are about 3 orders of magnitude higher than that of [8]CPP (1.37/2.78 × 10-4 cm2·V-1·s-1 for the [4]cyclocarbazoles vs 1.21 × 10-7 cm2·V-1·s-1 for [8]CPP), highlighting the strong effect of nitrogen bridges on the charge transport properties. The whole study opens the way to the use of nanorings in electronics, which is now the next step of their development.

Preface

Introduction The sixth interdisciplinary scientific forum with international participation “New materials and promising technologies” was held online with 23 on 27 November 2020. The main organizers of the event were the Council of Young Scientists of the Russian Academy of Sciences and the Coordinating Council for Youth Affairs in the Scientific and Educational Spheres under the Council for Science and Education under the President of the Russian Federation.The co-organizers were the Russian Academy of Sciences, Russian Chemical Society named after. DI. Mendeleev, Institute of Organic Chemistry named after. N.D.. Zelinsky RAS, A. A. Baykov Institute of Metallurgy and Materials Science RAS, Russian University of Chemical Technology named after D.I.. Mendeleev, All-Russian Scientific Research Institute of Phytopathology, Moscow Regional Research Clinical Institute named after. M. F. Vladimirsky, National Research Institute of Public Health named after N.A.. Semashko, Institute of Biochemical Physics named after N.M.. Emanuel RAS, Moscow State Regional University, Rossotrudnichestvo.The purpose of the forum is to form new successful scientific groups, the involvement of young specialists in the field of research and development, the development of cooperation between Russian and international research organizations, representatives of authorities, industry, business, mass media, as well as strengthening interdisciplinary ties in the scientific community, promoting the integration of science and industry in Russia to create new materials and promising technologies.The forum was opened by Andrei Leonidovich Kotelnikov, Chairman of the Council of Young Scientists of the Russian Academy of Sciences, Marchenkov Nikita Vladimirovich Acting. head of the Kurchatov complex of synchrotron-neutron research, National Research Center “Kurchatva Institute”, Chairman of the Coordinating Council for Youth Affairs in the Scientific and Educational Spheres of the Council for Science and Education under the President of the Russian Federation, RAS Academician Khokhlov Alexey Removich Vice-President of RAS, Director General of the Russian Science Foundation Alexander Vitalievich Khlunov, Academician of the Russian Academy of Sciences Egorov Mikhail Petrovich Academician- Secretary of the Department of Chemistry and Materials Sciences of the Russian Academy of Sciences Director of the Institute of Organic Chemistry named after. N.D.. Zelensky RAS, Academician of the Russian Academy of Sciences Tsivadze Aslan Yusupovich President of the Russian Chemical Society named after. DI. Mendeleev, Scientific Director of the Institute of Physical Chemistry and Electrochemistry named after A.N.. Frumkin Institute of Physical Chemistry and Electrochemistry RAS, Sevostyanov Mikhail Anatolyevich Deputy Chairman of the Council of Young Scientists of the Russian Academy of Sciences, Chairman of the Forum Organizing Committee.A workshop was held on the first day of the Forum “How research results become news” and round tables “Human factor, as a guarantee of development” and “Scientometrics - management and communication tools in science”.Within the framework of the forum, twelve sections worked in the following areas:“Organic functional materials” “Additive technologies” “Nanomaterials and Nanotechnologies” “Health-saving of the population: management technologies” “Construction materials” “New materials and technologies in the oil and gas industry. Gas, oil, energy” “Perspective processes in metallurgy” “Materials and technologies for green chemistry” “Inorganic functional materials” “Biomaterials and Technologies” “Experimental methods of research of materials and structures” “Materials and technologies for agriculture”.More than 700 scientists from Russia, Azerbaijan, Belarus, Of Kazakhstan, Moldova, Tajikistan, Of Uzbekistan, France and Czech Republic, which contributed to the emergence of not only national, but also international contacts from different cities of the Russian Federation. The forum presented 226 oral presentations.

Recent Developments in Polymeric Assemblies and Functional Materials by Halogen Bonding

AbstractPolymers have long been known to us for their versatile utility in our daily lives. With many years of successful advancement in controlled polymer synthesis and supramolecular chemistry, currently an amalgamation of these two fields is becoming increasingly important for generating modern‐day emerging polymeric materials. Hydrogen bonding and other noncovalent interactions like π‐stacking, host‐guest interaction, electrostatic interaction, metal‐ligand coordination have been explored much to this context, unlike the recently emerged halogen bonding, which indeed shows advantageous features like superior hydrophobicity, directionality and polar solvent resistance compared to ubiquitous hydrogen bonding. Hence, rendering these properties of halogen bonding into polymeric domain for generating functional materials for application in advance nanotechnologies is highly desirable. In the recent years, substantial progress has been made in fulfilling this challenging goal. This is evident from the escalating number of scientific publications in this research area every year. In this minireview, we have summarized the most recent developments in the field of halogen bonded polymeric assemblies and supramolecular polymers and discussed them in the context of their emerging materials properties and functions. Emphasis is given on highlighting various design criteria adopted in crystal engineering, covalent and supramolecular polymers in the past five years for constructing diverse organic functional materials, viz. liquid crystals, photoresponsive and photochromic materials, biomaterials and gels, self‐healing materials and many others by virtue of this highly directional supramolecular tool. In conclusion, a brief perspective on the advantages, challenges and future prospects in this rapidly growing field of research is discussed.

Comparing molecular and electronic properties of perylene tetracarboxylic diimides decorated at 1,6- and 1,7-bay-positions using DFT/TDDFT method

Geometrical structures and singlet vertical excitations of perylene tetracarboxylic diimides decorated at 1,6- and 1,7-bay positions investigated using density functional theory and its time dependent formalism. Such compounds are attracting much attention in the field of organic functional materials science. While 1,7-PDI regioisomers are synthetically accessible in pure form, it is still a challenging task to obtain 1,6-regioisomers in pure form. Ground state equilibrium geometries were optimized using the B3LYP functional with triple-ζ quality TZVP basis set. Introduction of either bromine or amino substituent groups at 1,6(7)-positions distorts the planarity of perylene core. Core twisting is larger for the derivatives substituted at 1,6-positions. For computing singlet vertical excitation energies, global hybrids B3LYP, PBE0 and range-separated hybrid CAM-B3LYP density functionals tested. B3LYP computed the most accurate excitation energies against experimental absorption maximum (λmax), with a mean absolute deviation (MAD) of 0.050 eV when solvent effects included. N-alkyl substituents at the bay positions shift the absorption maxima towards the ∼700 nm region. Red shifting is more efficient with 1,7-substitution, while 1,6-amino substituted PDIs display an additional absorption peak resulting from HOMO-1 to LUMO electronic transition appearing as extension of lowest energy absorption band and covers a broader region of visible spectrum. Such electronic transition is hardly detectable for 1,7-regioisomers. Calculations reveal that amino substituted 1,6-regioisomers display lower-lying HOMOs compared to the respective 1,7-regioisomers. This observation is in line with the NBO analysis, suggesting higher contribution of side groups to HOMO levels in 1,7-regioisomers. Plotted frontier molecular orbital isodensity surfaces reveal that electron density distribution is affected markedly from the position of amino substituents on PDI core.

Fabrication of Functional Materials for Dye-sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) have been developed as a promising photovoltaic cell type in recent decades because of their low cost, environmental friendliness, ease of fabrication, and suitability for a wide range of indoor and outdoor applications, especially under diverse shaded and low-light condition. They are typically composed of three main components: a transparent conducting oxide (TCO) substrate-based working electrode with wide-bandgap semiconductors and dye sensitizer molecules, an electrolytic mediator based on redox couple species, and a TCO-based counter electrode consisting of catalyst materials. The development of intrinsic and functional organic, inorganic, metal oxide, composite, and carbon-based materials has been intensively studied to enhance the efficiency of DSSCs. A simple and low-cost fabrication process that uses natural products is also considered essential for further large-scale production. In this article, we review the fabrication of various functional materials and their effects on DSSC performance.

Cascade Oxidative C-H Annulation of Thiophenes: Heck-Type Pathway Enables Concise Access to Thienoacenes.

The pursuit of efficient synthetic route to thienoacenes represents an appealing yet challenging task in the fields of both organic synthetic chemistry and organic functional materials. In this work, we disclose a rhodium-catalyzed cascade C-H annulation of phenacyl phosphoniums with (benzo)thiophenes via a Heck-type pathway to provide a new class of planar thienoacenes, which involves the formation of three Caryl -Caryl bonds and one Caryl -O bond in a single operation. The neutral S,O-heteroacenes exhibit superior stability and adopt a herringbone-like packing mode with efficient π-π stacking in the crystals, suggesting their potential in organic semiconducting materials. This work first exemplifies the superiority of cascade oxidative C-H annulation involving a Heck-type pathway in the development of concise access to heteroacenes.

Cascade Oxidative C−H Annulation of Thiophenes: Heck‐Type Pathway Enables Concise Access to Thienoacenes

AbstractThe pursuit of efficient synthetic route to thienoacenes represents an appealing yet challenging task in the fields of both organic synthetic chemistry and organic functional materials. In this work, we disclose a rhodium‐catalyzed cascade C−H annulation of phenacyl phosphoniums with (benzo)thiophenes via a Heck‐type pathway to provide a new class of planar thienoacenes, which involves the formation of three Caryl‐Caryl bonds and one Caryl−O bond in a single operation. The neutral S,O‐heteroacenes exhibit superior stability and adopt a herringbone‐like packing mode with efficient π–π stacking in the crystals, suggesting their potential in organic semiconducting materials. This work first exemplifies the superiority of cascade oxidative C−H annulation involving a Heck‐type pathway in the development of concise access to heteroacenes.

Materials and devices for flexible and stretchable photodetectors and light-emitting diodes

Recently, significant efforts have been directed at overcoming the limitations of conventional rigid optoelectronic devices, particularly their poor mechanical stability under bending, folding, and stretching deformations. One of major approaches for rendering optoelectronic devices mechanically deformable is to replace the conventional electronic/optoelectronic materials with functional nanomaterials or organic materials that are intrinsically flexible/stretchable. Further, advanced device designs and unconventional fabrication methods have also contributed to the development of soft optoelectronic devices. Accordingly, new devices such as bio-inspired curved image sensors, wearable light emitting devices, and deformable bio-integrated optoelectronic devices have been developed. In this review, recent progress in the development of soft optoelectronic materials and devices is outlined. First, various materials such as nanomaterials, organic materials, and their hybrids that are suitable for developing deformable photodetectors, are presented. Then, the nanomaterials and organic/polymeric materials that are applicable in deformable light-emitting diodes are described. Finally, representative system-level applications of flexible and stretchable photodetectors and light-emitting diodes are reviewed, and future prospects are discussed.

Quantum Dynamics of Exciton Transport and Dissociation in Multichromophoric Systems.

Due to the subtle interplay of site-to-site electronic couplings, exciton delocalization, nonadiabatic effects, and vibronic couplings, quantum dynamical studies are needed to elucidate the details of ultrafast photoinduced energy and charge transfer events in organic multichromophoric systems. In this vein, we review an approach that combines first-principles parameterized lattice Hamiltonians with accurate quantum dynamical simulations using advanced multiconfigurational methods. Focusing on the elementary transfer steps in organic functional materials, we address coherent exciton migration and creation of charge transfer excitons in homopolymers, notably representative of the poly(3-hexylthiophene) material, as well as exciton dissociation at polymer:fullerene heterojunctions. We emphasize the role of coherent transfer, trapping effects due to high-frequency phonon modes, and thermal activation due to low-frequency soft modes that drive a diffusive dynamics.

Machine Learning Enables Highly Accurate Predictions of Photophysical Properties of Organic Fluorescent Materials: Emission Wavelengths and Quantum Yields.

The development of functional organic fluorescent materials calls for fast and accurate predictions of photophysical parameters for processes such as high-throughput virtual screening, while the task is challenged by the limitations of quantum mechanical calculations. We establish a database covering >4300 solvated organic fluorescent dyes with 3000 distinct compounds and develop a new machine learning approach aimed at efficient and accurate predictions of emission wavelength and photoluminescence quantum yield (PLQY). Our feature engineering has given rise to a functionalized structure descriptor (FSD) and a comprehensive general solvent descriptor (CGSD), whereby a highly black-box computational framework is realized with consistently good accuracy across different dye families, ability of describing substitution effects and solvent effects, efficiency for large-scale predictions, and workability with on-the-fly learning. Evaluations with unseen molecules suggest a remarkable mean absolute error of 0.13 for PLQY and 0.080 eV for emission energy, the latter comparable to time-dependent density functional theory (TD-DFT) calculations. An online prediction platform was constructed based on the ensemble model to make predictions in various solvents. Our statistical learning methodology will complement quantum mechanical calculations as an efficient alternative approach for the prediction of these parameters.

Enhanced Photovoltaic Efficiency via Control of Self-Assembly in Cyanopyridone-Based Oligothiophene Donors.

The optoelectronic properties of functional π-conjugated organic materials are affected by their ability to self-assemble within thin films of devices. There are limited reports that demonstrate the positive impact of self-assembly on the photovoltaic performance of organic solar cells. Here, we demonstrate that hydrogen-bonded supramolecular arrays of a cyanopyridone-based oligothiophene donor, CP6, show notable improvement in photovoltaic performance upon self-assembly into a nanofibrous network. The honeycomb-like blend network exhibited higher hole mobility, leading to efficient charge generation and transport. The photovoltaic performance of CP6 was superior to that of two structural analogues, CP5 and CP1, and was attributed to the enhanced capability of CP6 to self-assemble into a film morphology favorable for BHJ devices. The BHJ devices comprising CP6 and the conventional fullerene acceptor (PC71BM) exhibited an efficiency of 7.26%, which is greater than that of CP5 (5.19%) and CP1 (3.11%) and is among the best-performing, cyanopyridone-based oligothiophene donors described to date.

Thiophene‐Fused Naphthodiphospholes: Modulation of the Structural and Electronic Properties of Polycyclic Aromatics by Precise Fusion of Heteroles

For polycyclic aromatics with heterole-fused structures, the orientation of fused heterole rings as well as the geometry of their fused structures has a large impact on the physicochemical properties. In this study, a series of isomers of thiophene-fused naphthodiphospholes was designed and synthesized. Systematic investigation unveiled the explicit impact of heterole-fused structures on their structural and electronic properties. The isomers with 1,2/5,6-fused structure display phosphorescence due to enhanced spin-orbit coupling, whereas the isomers with 2,3/6,7-fused structure exhibit intense fluorescence. The trans isomers exhibited 1D slip π-stacked arrangement. In contrast, the cis isomers displayed 2D herringbone structure or columnar structure with a cavity. Therefore, the precisely controlled fusion of heterole rings is a universal approach to uncover their intrinsic properties for versatile applications as organic functional materials.

Monitoring molecular vibronic coherences in a bichromophoric molecule by ultrafast X-ray spectroscopy.

The role of quantum-mechanical coherences in the elementary photophysics of functional optoelectronic molecular materials is currently under active study. Designing and controlling stable coherences arising from concerted vibronic dynamics in organic chromophores is the key for numerous applications. Here, we present fundamental insight into the energy transfer properties of a rigid synthetic heterodimer that has been experimentally engineered to study coherences. Quantum non-adiabatic excited state simulations are used to compute X-ray Raman signals, which are able to sensitively monitor the coherence evolution. Our results verify their vibronic nature, that survives multiple conical intersection passages for several hundred femtoseconds at room temperature. Despite the contributions of highly heterogeneous evolution pathways, the coherences are unambiguously visualized by the experimentally accessible X-ray signals. They offer direct information on the dynamics of electronic and structural degrees of freedom, paving the way for detailed coherence measurements in functional organic materials.