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Functional Molecular Materials Insights—a Themed Issue in Honour of Professor...
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Functional Molecular Materials Insights—a Themed Issue in Honour of Professor Manuel Almeida on the Occasion of His 70th Birthday

A special issue of Magnetochemistry (ISSN 2312-7481). This special issue belongs to the section "Magnetic Materials".

Deadline for manuscript submissions: closed (20 October 2023) | Viewed by 30414

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Dr. Laura C. J. Pereira

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Guest Editor
C2TN, Center for Nuclear Sciences and Technologies, DECN, Department of Nuclear Sciences and Engineering, Instituto Superior Técnico, University Lisbon, P-2695-066 Bobadela LRS, Portugal
Interests: multifunctional and nanostructured materials; molecular magnetism; magnetic properties of materials; chemistry and physics of f-elements
Special Issues, Collections and Topics in MDPI journals
Dr. Dulce Belo

E-Mail Website
Guest Editor
C2TN, Center for Nuclear Sciences and Technologies, DECN, Department of Nuclear Sciences and Engineering, Instituto Superior Técnico, University Lisbon, P-2695-066 Bobadela LRS, Portugal
Interests: SCMM; transition metal bisdithiolenes; transport properties; molecular electronics; molecular design

Special Issue Information

Dear Colleagues,

The development of functional molecular materials has become one of the main challenges for chemists, physics, and materials researchers. Molecular materials are based on well-designed molecular building blocks, prepared by advanced organic/inorganic synthetic methods, and crystal engineering plays a fundamental role in obtaining the desired (nano)structures. Crystal engineering has enabled the development of materials with tuneable chemical and physical solid-state properties. The field has evolved significantly, with a growing number of molecular materials capable not only of reproducing the different types of properties commonly found in other materials, but also of showing new ones. For this reason, multifunctional materials are potentially useful in technological applications, namely in electronic devices, sensors, and in spintronics.

This Special Issue of Magnetochemistry aims to publish a collection of state-of-the-art research papers illustrating the recent achievements on the development of molecular materials, especially those with unconventional magnetic and transport properties, as well as their potential applications, particularly addressing the topics listed below:

  • Design and preparation of new molecular building blocks;
  • Molecular materials for next-generation batteries;
  • Molecular materials with high-performance electronic and magnetic properties;
  • Molecular materials in electronic devices;
  • Molecular materials for bioscience and bioelectronics;
  • New optical, magnetic and electrical sensors for advanced electronic applications;
  • Electronic processes and relevant phenomena in molecular materials.

Dr. Laura C. J. Pereira
Dr. Dulce Belo
Guest Editors

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Magnetochemistry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • multifunctional and nanostructured materials
  • molecular magnetism
  • magnetic properties
  • transport properties
  • magnetic conductors
  • molecular electronics
  • chemistry and physics of organic-based molecules
  • SCMM
  • single-molecule magnets
  • molecular design
  • spintronics
  • transition metal bisdithiolenes
  • spin-crossover compounds
  • strongly correlated electronic systems

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Published Papers (16 papers)

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Editorial

Jump to: Research, Review, Other

4 pages, 179 KiB  
Editorial
Functional Molecular Materials Insights
by Laura C. J. Pereira and Dulce Belo
Magnetochemistry 2024, 10(1), 1; https://doi.org/10.3390/magnetochemistry10010001 - 20 Dec 2023
Viewed by 1590
Abstract
In the commemorative Special Issue titled “Insights into Functional Molecular Materials—A Themed Collection Honoring Professor Manuel Almeida on His 70th Birthday”, eminent researchers from around the globe in the field of molecular materials science come together to acknowledge and celebrate the notable scientific [...] Read more.
In the commemorative Special Issue titled “Insights into Functional Molecular Materials—A Themed Collection Honoring Professor Manuel Almeida on His 70th Birthday”, eminent researchers from around the globe in the field of molecular materials science come together to acknowledge and celebrate the notable scientific contributions of Professor Almeida [...] Full article
(This article belongs to the Special Issue Functional Molecular Materials Insights—a Themed Issue in Honour of Professor Manuel Almeida on the Occasion of His 70th Birthday)

Research

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10 pages, 3890 KiB  
Article
Synthesis and Structural and Magnetic Properties of Polycrystalline GaMo4Se8
by José F. Malta, Marta S. C. Henriques, José A. Paixão and António P. Gonçalves
Magnetochemistry 2023, 9(7), 182; https://doi.org/10.3390/magnetochemistry9070182 - 12 Jul 2023
Viewed by 1419
Abstract
GaMo4Se8, is a lacunar spinel where skyrmions have been recently reported. This compound belongs to the GaM4X8 family, where M is a transition metal (V or Mo) and X is a chalcogenide (S or Se). [...] Read more.
GaMo4Se8, is a lacunar spinel where skyrmions have been recently reported. This compound belongs to the GaM4X8 family, where M is a transition metal (V or Mo) and X is a chalcogenide (S or Se). In this work, we have obtained pure GaMo4Se8 in polycrystalline form through an innovative two-step synthetic route. Phase purity and chemical composition were confirmed through the Rietveld refinement of the powder XRD pattern, the sample characterisation having been complemented with SEM analysis. The magnetic phase diagram was investigated using DC (VSM) and AC magnetometry, which disclosed the presence of cycloidal, skyrmionic and ferromagnetic phases in polycrystalline GaMo4Se8. Full article
(This article belongs to the Special Issue Functional Molecular Materials Insights—a Themed Issue in Honour of Professor Manuel Almeida on the Occasion of His 70th Birthday)
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9 pages, 1596 KiB  
Communication
Nonthermal Equilibrium Process of Charge Carrier Extraction in Metal/Insulator/Organic Semiconductor/Metal (MIOM) Junction
by Hiroyuki Tajima, Takeshi Oda and Tomofumi Kadoya
Magnetochemistry 2023, 9(7), 180; https://doi.org/10.3390/magnetochemistry9070180 - 11 Jul 2023
Cited by 1 | Viewed by 1235
Abstract
This paper presents the concept and experimental evidence for the nonthermal equilibrium (NTE) process of charge carrier extraction in metal/insulator/organic semiconductor/metal (MIOM) capacitors. These capacitors are structurally similar to metal/insulator/semiconductor/(metal) (MIS) capacitors found in standard semiconductor textbooks. The difference between the two capacitors [...] Read more.
This paper presents the concept and experimental evidence for the nonthermal equilibrium (NTE) process of charge carrier extraction in metal/insulator/organic semiconductor/metal (MIOM) capacitors. These capacitors are structurally similar to metal/insulator/semiconductor/(metal) (MIS) capacitors found in standard semiconductor textbooks. The difference between the two capacitors is that the (organic) semiconductor/metal contacts in the MIOM capacitors are of the Schottky type, whereas the contacts in the MIS capacitors are of the ohmic type. Moreover, the mobilities of most organic semiconductors are significantly lower than those of inorganic semiconductors. As the MIOM structure is identical to the electrode portion of an organic field-effect transistor (OFET) with top-contact and bottom-gate electrodes, the hysteretic behavior of the OFET transfer characteristics can be deduced from the NTE phenomenon observed in MIOM capacitors. Full article
(This article belongs to the Special Issue Functional Molecular Materials Insights—a Themed Issue in Honour of Professor Manuel Almeida on the Occasion of His 70th Birthday)
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19 pages, 22520 KiB  
Article
Dirac Cone Formation in Single-Component Molecular Conductors Based on Metal Dithiolene Complexes
by Reizo Kato and Takao Tsumuraya
Magnetochemistry 2023, 9(7), 174; https://doi.org/10.3390/magnetochemistry9070174 - 6 Jul 2023
Cited by 1 | Viewed by 1522
Abstract
Single-component molecular conductors exhibit a strong connection to the Dirac electron system. The formation of Dirac cones in single-component molecular conductors relies on (1) the crossing of HOMO and LUMO bands and (2) the presence of nodes in the HOMO–LUMO couplings. In this [...] Read more.
Single-component molecular conductors exhibit a strong connection to the Dirac electron system. The formation of Dirac cones in single-component molecular conductors relies on (1) the crossing of HOMO and LUMO bands and (2) the presence of nodes in the HOMO–LUMO couplings. In this study, we investigated the possibility of Dirac cone formation in two single-component molecular conductors derived from nickel complexes with extended tetrathiafulvalenedithiolate ligands, [Ni(tmdt)2] and [Ni(btdt)2], using tight-biding models and first-principles density-functional theory (DFT) calculations. The tight-binding model predicts the emergence of Dirac cones in both systems, which is associated with the stretcher bond type molecular arrangement. The DFT calculations also indicate the formation of Dirac cones in both systems. In the case of [Ni(btdt)2], the DFT calculations, employing a vdW-DF2 functional, reveal the formation of Dirac cones near the Fermi level in the nonmagnetic state after structural optimization. Furthermore, the DFT calculations, by utilizing the range-separated hybrid functional, confirm the antiferromagnetic stability in [Ni(btdt)2], as observed experimentally. Full article
(This article belongs to the Special Issue Functional Molecular Materials Insights—a Themed Issue in Honour of Professor Manuel Almeida on the Occasion of His 70th Birthday)
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16 pages, 1086 KiB  
Article
On the Size of Superconducting Islands on the Density-Wave Background in Organic Metals
by Vladislav D. Kochev, Seidali S. Seidov and Pavel D. Grigoriev
Magnetochemistry 2023, 9(7), 173; https://doi.org/10.3390/magnetochemistry9070173 - 4 Jul 2023
Cited by 2 | Viewed by 1314
Abstract
Most high-Tc superconductors are spatially inhomogeneous. Usually, this heterogeneity originates from the interplay of various types of electronic ordering. It affects various superconducting properties, such as the transition temperature, the magnetic upper critical field, the critical current, etc. In this paper, [...] Read more.
Most high-Tc superconductors are spatially inhomogeneous. Usually, this heterogeneity originates from the interplay of various types of electronic ordering. It affects various superconducting properties, such as the transition temperature, the magnetic upper critical field, the critical current, etc. In this paper, we analyze the parameters of spatial phase segregation during the first-order transition between superconductivity (SC) and a charge- or spin-density wave state in quasi-one-dimensional metals with imperfect nesting, typical of organic superconductors. An external pressure or another driving parameter increases the transfer integrals in electron dispersion, which only slightly affects SC but violates the Fermi surface nesting and suppresses the density wave (DW). At a critical pressure Pc, the transition from a DW to SC occurs. We estimate the characteristic size of superconducting islands during this phase transition in organic metals in two ways. Using the Ginzburg–Landau expansion, we analytically obtain a lower bound for the size of SC domains. To estimate a more specific interval of the possible size of the superconducting islands in (TMTSF)2PF6 samples, we perform numerical calculations of the percolation probability via SC domains and compare the results with experimental resistivity data. This helps to develop a consistent microscopic description of SC spatial heterogeneity in various organic superconductors. Full article
(This article belongs to the Special Issue Functional Molecular Materials Insights—a Themed Issue in Honour of Professor Manuel Almeida on the Occasion of His 70th Birthday)
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18 pages, 3251 KiB  
Article
Band Structure Evolution during Reversible Interconversion between Dirac and Standard Fermions in Organic Charge-Transfer Salts
by Ryuhei Oka, Keishi Ohara, Kensuke Konishi, Ichiro Yamane, Toshihiro Shimada and Toshio Naito
Magnetochemistry 2023, 9(6), 153; https://doi.org/10.3390/magnetochemistry9060153 - 9 Jun 2023
Cited by 3 | Viewed by 2437
Abstract
Materials containing Dirac fermions (DFs) have been actively researched because they often alter electrical and magnetic properties in an unprecedented manner. Although many studies have suggested the transformation between standard fermions (SFs) and DFs, the non-availability of appropriate samples has prevented the observation [...] Read more.
Materials containing Dirac fermions (DFs) have been actively researched because they often alter electrical and magnetic properties in an unprecedented manner. Although many studies have suggested the transformation between standard fermions (SFs) and DFs, the non-availability of appropriate samples has prevented the observation of the transformation process. We observed the interconversion process of DFs and SFs using organic charge-transfer (CT) salts. The samples are unique in that the constituents (the donor D and acceptor A species) are particularly close to each other in energy, leading to the temperature- and D-A-combination-sensitive CT interactions in the solid states. The three-dimensional weak D–A CT interactions in low-symmetry crystals induced the continuous reshaping of flat-bottomed bands into Dirac cones with decreasing temperature; this is a characteristic shape of bands that converts the behavior of SFs into that of DFs. Based on the first-principles band structures supported by the observed electronic properties, round-apex-Dirac-cone-like features appear and disappear with temperature variation. These band-structure snapshots are expected to add further detailed understanding to the related research fields. Full article
(This article belongs to the Special Issue Functional Molecular Materials Insights—a Themed Issue in Honour of Professor Manuel Almeida on the Occasion of His 70th Birthday)
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7 pages, 350 KiB  
Article
Driving a Molecular Spin-Peierls System into a Short Range Ordered State through Chemical Substitution
by Adam Berlie, Ian Terry and Marek Szablewski
Magnetochemistry 2023, 9(6), 150; https://doi.org/10.3390/magnetochemistry9060150 - 8 Jun 2023
Viewed by 1190
Abstract
Chemically altering molecules can have dramatic effects on the physical properties of a series of very similar molecular compounds. A good example of this is within the quasi-1D spin-Peierls system potassium TCNQ (TCNQ = 7,7,8,8-tetracyanoqunidimethane), where substitution of TCNQF4 for TCNQ has [...] Read more.
Chemically altering molecules can have dramatic effects on the physical properties of a series of very similar molecular compounds. A good example of this is within the quasi-1D spin-Peierls system potassium TCNQ (TCNQ = 7,7,8,8-tetracyanoqunidimethane), where substitution of TCNQF4 for TCNQ has a dramatic effect on the 1D interactions, resulting in a drop in the corresponding spin-Peierls transition temperature. Within this work, we extend the investigation to potassium TCNQBr2, where only two protons of TCNQ can be substituted with bromine atoms due to steric constraints. The new system exhibits evidence for a residual component of the magnetism when probed via magnetic susceptibility measurements and muon spin spectroscopy. The observations suggest that the system is dominated by short range, and potentially disordered, correlations within the bulk phase. Full article
(This article belongs to the Special Issue Functional Molecular Materials Insights—a Themed Issue in Honour of Professor Manuel Almeida on the Occasion of His 70th Birthday)
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11 pages, 4802 KiB  
Communication
Two One-Dimensional Copper-Oxalate Frameworks with the Jahn–Teller Effect: [(CH3)3NH]2[Cu(μ-C2O4)(C2O4)]·2.5H2O (I) and [(C2H5)3NH]2[Cu(μ-C2O4)(C2O4)]·H2O (II)
by Bin Zhang, Yan Zhang, Zheming Wang, Yang Sun, Tongling Liang, Mei Liu and Daoben Zhu
Magnetochemistry 2023, 9(5), 120; https://doi.org/10.3390/magnetochemistry9050120 - 29 Apr 2023
Cited by 2 | Viewed by 1483
Abstract
Two one-dimensional oxalate-bridged Cu(II) ammonium salts, [(CH3)3NH]2[Cu(μ-C2O4)(C2O4)]·2.5H2O (I) and [(C2H5)3NH]2[Cu(μ-C2O4)(C2O4 [...] Read more.
Two one-dimensional oxalate-bridged Cu(II) ammonium salts, [(CH3)3NH]2[Cu(μ-C2O4)(C2O4)]·2.5H2O (I) and [(C2H5)3NH]2[Cu(μ-C2O4)(C2O4)]·H2O (II) were obtained and characterized. They were composed of ammonium: (CH3)3NH+ in (I), (C2H5)3NH+ in (II), [Cu(μ-C2O4)(C2O4)2−]n and H2O. The Jahn–Teller-distorted Cu(II) is octahedrally coordinated by six O atoms from three oxalates and forms a one-dimensional zigzag chain. The hydrogen bonds between ammonium, the anion and H2O form a three-dimensional network. There is no hydrogen bond between the anion chains. They were insulated at 20 °C with a relative humidity of 40%. Ferromagnetic and weak-ferromagnetic behaviors were observed in I and II, separately. No long-range ordering was observed above 2 K. Full article
(This article belongs to the Special Issue Functional Molecular Materials Insights—a Themed Issue in Honour of Professor Manuel Almeida on the Occasion of His 70th Birthday)
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16 pages, 2174 KiB  
Article
A Simulation Independent Analysis of Single- and Multi-Component cw ESR Spectra
by Aritro Sinha Roy, Boris Dzikovski, Dependu Dolui, Olga Makhlynets, Arnab Dutta and Madhur Srivastava
Magnetochemistry 2023, 9(5), 112; https://doi.org/10.3390/magnetochemistry9050112 - 23 Apr 2023
Cited by 1 | Viewed by 2221
Abstract
The accurate analysis of continuous-wave electron spin resonance (cw ESR) spectra of biological or organic free-radicals and paramagnetic metal complexes is key to understanding their structure–function relationships and electrochemical properties. The current methods of analysis based on simulations often fail to extract the [...] Read more.
The accurate analysis of continuous-wave electron spin resonance (cw ESR) spectra of biological or organic free-radicals and paramagnetic metal complexes is key to understanding their structure–function relationships and electrochemical properties. The current methods of analysis based on simulations often fail to extract the spectral information accurately. In addition, such analyses are highly sensitive to spectral resolution and artifacts, users’ defined input parameters and spectral complexity. We introduce a simulation-independent spectral analysis approach that enables broader application of ESR. We use a wavelet packet transform-based method for extracting g values and hyperfine (A) constants directly from cw ESR spectra. We show that our method overcomes the challenges associated with simulation-based methods for analyzing poorly/partially resolved and unresolved spectra, which is common in most cases. The accuracy and consistency of the method are demonstrated on a series of experimental spectra of organic radicals and copper–nitrogen complexes. We showed that for a two-component system, the method identifies their individual spectral features even at a relative concentration of 5% for the minor component. Full article
(This article belongs to the Special Issue Functional Molecular Materials Insights—a Themed Issue in Honour of Professor Manuel Almeida on the Occasion of His 70th Birthday)
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11 pages, 3423 KiB  
Communication
A New Organic Conductor of Tetramethyltetraselenafulvalene (TMTSF) with a Magnetic Dy(III) Complex
by Qingyun Wan, Masanori Wakizaka, Haitao Zhang, Yongbing Shen, Nobuto Funakoshi, Chi-Ming Che, Shinya Takaishi and Masahiro Yamashita
Magnetochemistry 2023, 9(3), 77; https://doi.org/10.3390/magnetochemistry9030077 - 6 Mar 2023
Cited by 2 | Viewed by 2134
Abstract
A new molecular conductor of (TMTSF)5[Dy(NCS)4(NO3)2]CHCl3 was prepared using the electrochemical oxidation method. The complex crystallizes in the Cmc21 (36) space group, where the partially-oxidized TMTSF molecules form a 1D (one-dimensional) column structure. [...] Read more.
A new molecular conductor of (TMTSF)5[Dy(NCS)4(NO3)2]CHCl3 was prepared using the electrochemical oxidation method. The complex crystallizes in the Cmc21 (36) space group, where the partially-oxidized TMTSF molecules form a 1D (one-dimensional) column structure. The crystal shows a semiconducting behavior with a room temperature conductivity of 0.2 S·cm−1 and an activation energy of 34 meV at ambient pressure. Full article
(This article belongs to the Special Issue Functional Molecular Materials Insights—a Themed Issue in Honour of Professor Manuel Almeida on the Occasion of His 70th Birthday)
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9 pages, 697 KiB  
Article
Superconductivity and Fermi Surface Studies of β″-(BEDT-TTF)2[(H2O)(NH4)2Cr(C2O4)3]·18-Crown-6
by Brett Laramee, Raju Ghimire, David Graf, Lee Martin, Toby J. Blundell and Charles C. Agosta
Magnetochemistry 2023, 9(3), 64; https://doi.org/10.3390/magnetochemistry9030064 - 24 Feb 2023
Cited by 1 | Viewed by 1961
Abstract
We report rf-penetration depth measurements of the quasi-2D organic superconductor β″-(BEDT-TTF)2[(H2O)(NH4)2Cr(C2O4)3]·18-crown-6, which has the largest separation between consecutive conduction layers of any 2D organic metal with a [...] Read more.
We report rf-penetration depth measurements of the quasi-2D organic superconductor β″-(BEDT-TTF)2[(H2O)(NH4)2Cr(C2O4)3]·18-crown-6, which has the largest separation between consecutive conduction layers of any 2D organic metal with a single packing motif. Using a contactless tunnel diode oscillator measurement technique, we show the zero-field cooling dependence and field sweeps up to 28 T oriented at various angles with respect to the crystal conduction planes. When oriented parallel to the layers, the upper critical field, Hc2=7.6 T, which is the calculated paramagnetic limit for this material. No signs of inhomogeneous superconductivity are seen, despite previous predictions. When oriented perpendicular to the layers, Shubnikov–de Haas oscillations are seen as low as 6 T, and from these we calculate Fermi surface parameters such as the superconducting coherence length and Dingle temperature. One remarkable result from our data is the high anisotropy of Hc2 in the parallel and perpendicular directions, due to an abnormally low Hc2⊥=0.4 T. Such high anisotropy is rare in other organics and the origin of the smaller Hc2⊥ may be a consequence of a lower effective mass. Full article
(This article belongs to the Special Issue Functional Molecular Materials Insights—a Themed Issue in Honour of Professor Manuel Almeida on the Occasion of His 70th Birthday)
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9 pages, 1964 KiB  
Article
Vibronic Relaxation Pathways in Molecular Spin Qubit Na9[Ho(W5O18)2]·35H2O under Pressure
by Janice L. Musfeldt, Zhenxian Liu, Diego López-Alcalá, Yan Duan, Alejandro Gaita-Ariño, José J. Baldoví and Eugenio Coronado
Magnetochemistry 2023, 9(2), 53; https://doi.org/10.3390/magnetochemistry9020053 - 9 Feb 2023
Viewed by 2087
Abstract
In order to explore how spectral sparsity and vibronic decoherence pathways can be controlled in a model qubit system with atomic clock transitions, we combined diamond anvil cell techniques with synchrotron-based far infrared spectroscopy and first-principles calculations to reveal the vibrational response of [...] Read more.
In order to explore how spectral sparsity and vibronic decoherence pathways can be controlled in a model qubit system with atomic clock transitions, we combined diamond anvil cell techniques with synchrotron-based far infrared spectroscopy and first-principles calculations to reveal the vibrational response of Na9[Ho(W5O18)2]·35H2O under compression. Because the hole in the phonon density of states acts to reduce the overlap between the phonons and f manifold excitations in this system, we postulated that pressure might move the HoO4 rocking, bending, and asymmetric stretching modes that couple with the MJ = ±5, ±2, and ±7 levels out of resonance, reducing their interactions and minimizing decoherence processes, while a potentially beneficial strategy for some molecular qubits, pressure slightly hardens the phonons in Na9[Ho(W5O18)2]·35H2O and systematically fills in the transparency window in the phonon response. The net result is that the vibrational spectrum becomes less sparse and the overlap with the various MJ levels of the Ho3+ ion actually increases. These findings suggest that negative pressure, achieved using chemical means or elongational strain, could further open the transparency window in this rare earth-containing spin qubit system, thus paving the way for the use of device surfaces and interface elongational/compressive strains to better manage decoherence pathways. Full article
(This article belongs to the Special Issue Functional Molecular Materials Insights—a Themed Issue in Honour of Professor Manuel Almeida on the Occasion of His 70th Birthday)
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Graphical abstract

15 pages, 923 KiB  
Article
Giant Angular Nernst Effect in the Organic Metal α-(BEDT-TTF)2KHg(SCN)4
by Danica Krstovska, Eun Sang Choi and Eden Steven
Magnetochemistry 2023, 9(1), 27; https://doi.org/10.3390/magnetochemistry9010027 - 10 Jan 2023
Cited by 1 | Viewed by 1725
Abstract
We have detected a large Nernst effect in the charge density wave state of the multiband organic metal α-(BEDT-TTF)2KHg(SCN)4. We find that apart from the phonon drag effect, the energy relaxation processes that govern the electron–phonon interactions and [...] Read more.
We have detected a large Nernst effect in the charge density wave state of the multiband organic metal α-(BEDT-TTF)2KHg(SCN)4. We find that apart from the phonon drag effect, the energy relaxation processes that govern the electron–phonon interactions and the momentum relaxation processes that determine the mobility of the q1D charge carriers have a significant role in observing the large Nernst signal in the CDW state in this organic metal. The emphasised momentum relaxation dynamics in the low field CDW state (CDW0) is a clear indicator of the presence of a significant carrier mobility that might be the main source for observation of the largest Nernst signal. The momentum relaxation is absent with increasing angle and magnetic field, i.e., in the high-field CDW state (CDWx) as evident from the much smaller Nernst effect amplitude in this state. In this case, only the phonon drag effect and electron–phonon interactions are contributing to the transverse thermoelectric signal. Our findings advance and change previous observations on the complex properties of this organic metal. Full article
(This article belongs to the Special Issue Functional Molecular Materials Insights—a Themed Issue in Honour of Professor Manuel Almeida on the Occasion of His 70th Birthday)
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10 pages, 2270 KiB  
Article
Effect of External Pressure on the Metal–Insulator Transition of the Organic Quasi-Two-Dimensional Metal κ-(BEDT-TTF)2Hg(SCN)2Br
by Sergei I. Pesotskii, Rustem B. Lyubovskii, Gennady V. Shilov, Vladimir N. Zverev, Svetlana A. Torunova, Elena I. Zhilyaeva and Enric Canadell
Magnetochemistry 2022, 8(11), 152; https://doi.org/10.3390/magnetochemistry8110152 - 8 Nov 2022
Cited by 1 | Viewed by 1827
Abstract
The metal–insulator transition in the organic quasi-two-dimensional metal κ-(BEDT-TTF)2Hg(SCN)2Br at TMI ≈ 90 K has been investigated. The crystal structure changes during this transition from monoclinic above TMI to triclinic below TMI. A theoretical study [...] Read more.
The metal–insulator transition in the organic quasi-two-dimensional metal κ-(BEDT-TTF)2Hg(SCN)2Br at TMI ≈ 90 K has been investigated. The crystal structure changes during this transition from monoclinic above TMI to triclinic below TMI. A theoretical study suggested that this phase transition should be of the metal-to-metal type and brings about a substantial change of the Fermi surface. Apparently, the electronic system in the triclinic phase is unstable toward a Mott insulating state, leading to the growth of the resistance when the temperature drops below TMI ≈ 90 K. The application of external pressure suppresses the Mott transition and restores the metallic electronic structure of the triclinic phase. The observed quantum oscillations of the magnetoresistance are in good agreement with the calculated Fermi surface for the triclinic phase, providing a plausible explanation for the puzzling behavior of κ-(BEDT-TTF)2Hg(SCN)2Br as a function of temperature and pressure around 100 K. The present study points out interesting differences in the structural and physical behaviors of the two room temperature isostructural salts of κ-(BEDT-TTF)2Hg(SCN)2X with X = Br, Cl. Full article
(This article belongs to the Special Issue Functional Molecular Materials Insights—a Themed Issue in Honour of Professor Manuel Almeida on the Occasion of His 70th Birthday)
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Review

Jump to: Editorial, Research, Other

19 pages, 5980 KiB  
Review
Spin-Peierls, Spin-Ladder and Kondo Coupling in Weakly Localized Quasi-1D Molecular Systems: An Overview
by Jean-Paul Pouget
Magnetochemistry 2023, 9(2), 57; https://doi.org/10.3390/magnetochemistry9020057 - 13 Feb 2023
Cited by 3 | Viewed by 1944
Abstract
We review the magneto-structural properties of electron–electron correlated quasi-one- dimensional (1D) molecular organics. These weakly localized quarter-filled metallic-like systems with pronounced spin 1/2 antiferromagnetic (AF) interactions in stack direction exhibit a spin charge decoupling where magnetoelastic coupling picks up spin 1/2 to pair [...] Read more.
We review the magneto-structural properties of electron–electron correlated quasi-one- dimensional (1D) molecular organics. These weakly localized quarter-filled metallic-like systems with pronounced spin 1/2 antiferromagnetic (AF) interactions in stack direction exhibit a spin charge decoupling where magnetoelastic coupling picks up spin 1/2 to pair into S = 0 singlet dimers. This is well illustrated by the observation of a spin-Peierls (SP) instability in the (TMTTF)2X Fabre salts and related salts with the o-DMTTF donor. These instabilities are revealed by the formation of a pseudo-gap in the spin degrees of freedom triggered by the development of SP structural correlations. The divergence of these 1D fluctuations, together with the interchain coupling, drive a 3D-SP ground state. More surprisingly, we show that the Per2-M(mnt)2 system, undergoing a Kondo coupling between the metallic Per stack and the dithiolate stack of localized AF coupled spin ½ (for M = Pd, Ni, Pt), enhances the SP instability. Then, we consider the zig-zag spin ladder DTTTF2-M(mnt)2 system, where unusual singlet ground state properties are due to a combination of a 4kF charge localization effect in stack direction and a 2kF SP instability along the zig-zag ladder. Finally, we consider some specific features of correlated 1D systems concerning the coexistence of symmetrically different 4kF BOW and 4kF CDW orders in quarter-filled organics, and the nucleation of solitons in perturbed SP systems. Full article
(This article belongs to the Special Issue Functional Molecular Materials Insights—a Themed Issue in Honour of Professor Manuel Almeida on the Occasion of His 70th Birthday)
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17 pages, 6147 KiB  
Perspective
Lanthanide-Based Metal–Organic Frameworks with Single-Molecule Magnet Properties
by Fabio Manna, Mariangela Oggianu, Narcis Avarvari and Maria Laura Mercuri
Magnetochemistry 2023, 9(7), 190; https://doi.org/10.3390/magnetochemistry9070190 - 22 Jul 2023
Cited by 9 | Viewed by 2487
Abstract
Lanthanide metal–organic frameworks (Ln-MOFs) showing single-molecule magnet (SMM) properties are an ever-growing family of materials where the magnetic properties can be tuned by various interrelated parameters, such as the coordinated solvent, temperature, organic linkers, lanthanide ions and their coordination environment. An overview of [...] Read more.
Lanthanide metal–organic frameworks (Ln-MOFs) showing single-molecule magnet (SMM) properties are an ever-growing family of materials where the magnetic properties can be tuned by various interrelated parameters, such as the coordinated solvent, temperature, organic linkers, lanthanide ions and their coordination environment. An overview of the general synthetic methodologies to access MOFs/Ln-MOFs and the peculiarities and parameters to control and/or fine-tune their SMM behavior is herein presented. Additionally, diverse challenging strategies for inducing SMM/SIM behavior in an Ln-MOF are discussed, involving redox activity and chirality. Furthermore, intriguing physical phenomena such as the CISS effect and CPL are also highlighted. Full article
(This article belongs to the Special Issue Functional Molecular Materials Insights—a Themed Issue in Honour of Professor Manuel Almeida on the Occasion of His 70th Birthday)
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