Charge Transfer Crystals

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystal Engineering".

Deadline for manuscript submissions: closed (31 July 2020) | Viewed by 21640

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Dipartimento di Scienze Chimiche, della Vita e della Sostenibilità Ambientale, Università di Parma, 43124 Parma, Italy
Interests: spectral properties crystalline materials; molecular crystals; phase transitions in organic solids; organic semiconductors; organic superconductors; thin films
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Special Issue Information

Dear Colleagues,

Charge transfer (CT) interaction is at the basis of many fascinating phenomena in condensed matter. The interaction acquired particular relevance in the field of crystalline organic conductors and superconductors, as CT crystals offered the first realization of these materials. Indeed, three Crystals Special Issues have been devoted to this mature but still very active field: “Molecular Conductors” edited by Reizo Kato in 2012, “Advances in Organic Conductors and Superconductors” edited by Martin Dressel in 2017, and “Structure and Properties of Molecular Conductors” edited by Manuel Almeida, due in 2020. Further, research on the remarkable neutral–ionic phase transition occurring in mixed stack CT crystals has been the focus of another Crystals Special Issue, “The Neutral–Ionic Phase Transition”, edited by Anna Painelli and myself in 2017.

On the other hand, several others research lines on CT crystals have emerged in the last few years, both at the fundamental or speculative level and in the burgeoning field of organic materials. Just to cite a few, I mention crystal engineering and crystal growth techniques, polymorphism, ambipolar semiconductors, ferroelectrics and multiferroics, and so on. Since the underlying physics and chemistry remain the same, and often also the basic molecular structures, I believe the time has come for a Special Issue that will cover the field of CT crystals from a broader and unifying perspective.

This Special Issue is then aimed at providing a stimulating and up-to-date outlook on CT crystals’ research. Scientists working in a wide range of disciplines are invited to contribute with original papers or short reviews on their activity in the field, following the lines suggested by (but not limited to) the Special Issue keywords.

Prof. Dr. Alberto Girlando
Guest Editor

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Keywords

  • Crystal engineering
  • Crystal growth techniques
  • Phase transitions
  • New electron-donor or acceptor molecules
  • Polymorphism
  • Organic semiconductors
  • Organic metals
  • Organic ferroelectric and multiferroic
  • Light emission properties
  • Theoretical modeling and computational methods

Published Papers (5 papers)

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Research

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17 pages, 3368 KiB  
Article
Tetrathiafulvalene: A Gate to the Mechanochemical Mechanisms of Electron Transfer Reactions
by Richard Chen, Mehmet Kerem Gokus and Silvina Pagola
Crystals 2020, 10(6), 482; https://doi.org/10.3390/cryst10060482 - 5 Jun 2020
Cited by 8 | Viewed by 3150
Abstract
This report describes aspects of our previous studies of the mechanochemical synthesis of charge transfer complexes of the electron donor tetrathiafulvalene, which are relevant to the use of laboratory X-ray powder diffraction for ex situ monitoring of mechanochemical reactions toward investigating their mechanisms. [...] Read more.
This report describes aspects of our previous studies of the mechanochemical synthesis of charge transfer complexes of the electron donor tetrathiafulvalene, which are relevant to the use of laboratory X-ray powder diffraction for ex situ monitoring of mechanochemical reactions toward investigating their mechanisms. In particular, the reaction of tetrathiafulvalene and chloranil was studied under neat mechanochemical conditions and liquid-assisted grinding with diethyl ether (1 μL/mg). The product in both cases is the green tetrathiafulvalene chloranil polymorph and the mechanism of the redox reaction is presumably the same. However, while the kinetic profile of the neat mechanochemical synthesis was fitted with a second-order rate law, that of the overall faster liquid-assisted grinding reaction was fitted with the Ginstling-Brounshtein 3D diffusion-controlled model. Hence, the diffusional processes and mass transfer bringing the reactants together and separating them from products must be different. Diffraction measurements sensitive to crystalline phases and amorphous material, combined with in situ monitoring by spectroscopic techniques, will ultimately afford a better understanding of mechanochemical reaction mechanisms, a hot topic in mechanochemistry. Full article
(This article belongs to the Special Issue Charge Transfer Crystals)
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9 pages, 3180 KiB  
Article
(Perylene)3-(TCNQF1)2: Yet Another Member in the Series of Perylene–TCNQFx Polymorphic Charge Transfer Crystals
by Tommaso Salzillo, Raffaele G. Della Valle, Elisabetta Venuti, Aldo Brillante, Gabriele Kociok-Köhn, Daniele Di Nuzzo, Matteo Masino and Alberto Girlando
Crystals 2020, 10(3), 177; https://doi.org/10.3390/cryst10030177 - 6 Mar 2020
Cited by 4 | Viewed by 2841
Abstract
The 3:2 Charge Transfer (CT) co-crystal (Perylene)3(TCNQF1)2 is grown by the Physical Vapor Transport (PVT) method, and characterized structurally and spectroscopically. Infrared analysis of the charge sensitive modes reveals a low degree of charge transfer (less than 0.1) [...] Read more.
The 3:2 Charge Transfer (CT) co-crystal (Perylene)3(TCNQF1)2 is grown by the Physical Vapor Transport (PVT) method, and characterized structurally and spectroscopically. Infrared analysis of the charge sensitive modes reveals a low degree of charge transfer (less than 0.1) between donor and acceptor molecules. The crystal is isostructural to the other 3:2 CT crystals formed by Perylene with TCNQF2 and TCNQF4, whereas such stoichiometry and packing is not known for the CT crystals with non-fluorinated TCNQ. The analysis of the isostructural family of 3:2 Perylene–TCNQFx (x = 1,2,4) co-crystal put in evidence the role of weak FHC bonding in stabilizing this type of structure Full article
(This article belongs to the Special Issue Charge Transfer Crystals)
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22 pages, 7202 KiB  
Article
Structure of Imidazolium-N-phthalolylglycinate Salt Hydrate: Combined Experimental and Quantum Chemical Calculations Studies
by Mohammad Usman, Rais Ahmad Khan, Mohammad H. Jaafar, Ali Alsalme and Sartaj Tabassum
Crystals 2020, 10(2), 91; https://doi.org/10.3390/cryst10020091 - 5 Feb 2020
Cited by 1 | Viewed by 2263
Abstract
An organic supramolecular salt hydrate (imidazolium:N-phthalolylglycinate:H2O; IM+-NPG-HYD) has been examined for its charge-transfer (CT) characteristics. Accordingly, IM+–NPG–HYD has been characterized thoroughly using various spectroscopic techniques. Combined experimental and quantum chemical studies, along [...] Read more.
An organic supramolecular salt hydrate (imidazolium:N-phthalolylglycinate:H2O; IM+-NPG-HYD) has been examined for its charge-transfer (CT) characteristics. Accordingly, IM+–NPG–HYD has been characterized thoroughly using various spectroscopic techniques. Combined experimental and quantum chemical studies, along with wave function analysis, were performed to study the non-covalent interactions and their role in CT in the supramolecular salt hydrate. Notably, IM+–NPG–HYD crystalizes in two configurations (A and B), both of which are held together via non-covalent interactions to result in a three-dimensional CT supramolecular assembly. The through-space CT occurs from NPG (donor) to IM+ (acceptor), and this was mediated via non-covalent forces. We demonstrated the role of π–π stacking interactions (mixed-stacking donor-acceptor interactions) in the presence of charge-assisted hydrogen bonds in the regulation of CT properties in the self-assembly of the IM+–NPG–HYD salt hydrate. Full article
(This article belongs to the Special Issue Charge Transfer Crystals)
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Review

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18 pages, 7111 KiB  
Review
The Stoichiometry of TCNQ-Based Organic Charge-Transfer Cocrystals
by Jiaoyang Gao, Huifei Zhai, Peng Hu and Hui Jiang
Crystals 2020, 10(11), 993; https://doi.org/10.3390/cryst10110993 - 2 Nov 2020
Cited by 9 | Viewed by 4489
Abstract
Organic charge-transfer cocrystals (CTCs) have attracted significant research attention due to their wide range of potential applications in organic optoelectronic devices, organic magnetic devices, organic energy devices, pharmaceutical industry, etc. The physical properties of organic charge transfer cocrystals can be tuned not only [...] Read more.
Organic charge-transfer cocrystals (CTCs) have attracted significant research attention due to their wide range of potential applications in organic optoelectronic devices, organic magnetic devices, organic energy devices, pharmaceutical industry, etc. The physical properties of organic charge transfer cocrystals can be tuned not only by changing the donor and acceptor molecules, but also by varying the stoichiometry between the donor and the acceptor. However, the importance of the stoichiometry on tuning the properties of CTCs has still been underestimated. In this review, single-crystal growth methods of organic CTCs with different stoichiometries are first introduced, and their physical properties, including the degree of charge transfer, electrical conductivity, and field-effect mobility, are then discussed. Finally, a perspective of this research direction is provided to give the readers a general understanding of the concept. Full article
(This article belongs to the Special Issue Charge Transfer Crystals)
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28 pages, 8074 KiB  
Review
Angle-Resolved Photoemission Study on the Band Structure of Organic Single Crystals
by Ke Wang, Ben Ecker and Yongli Gao
Crystals 2020, 10(9), 773; https://doi.org/10.3390/cryst10090773 - 1 Sep 2020
Cited by 6 | Viewed by 8303
Abstract
Angle-resolved photoemission spectroscopy (ARPES) is a vital technique, collecting data from both the energy and momentum of photoemitted electrons, and is indispensable for investigating the electronic band structure of solids. This article provides a review on ARPES studies of the electronic band structure [...] Read more.
Angle-resolved photoemission spectroscopy (ARPES) is a vital technique, collecting data from both the energy and momentum of photoemitted electrons, and is indispensable for investigating the electronic band structure of solids. This article provides a review on ARPES studies of the electronic band structure of organic single crystals, including organic charge transfer conductors; organic semiconductors; and organo-metallic perovskites. In organic conductors and semiconductors, band dispersions are observed that are highly anisotropic. The Van der Waals crystal nature, the weak electron wavefunction overlap, as well as the strong electron-phonon coupling result in many organic crystals having indiscernible dispersion. In comparison, organo-metallic perovskite halides are characterized by strong s-p orbitals from the metal and halide at the top of the valence bands, with dispersions similar to those in inorganic materials. Full article
(This article belongs to the Special Issue Charge Transfer Crystals)
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