scholarly journals Reversible Switching of Organic Diradical Character via Iron-Based Spin-crossover

2020 ◽  
Author(s):  
Airi Kawamura ◽  
Jiaze Xie ◽  
Jan-Niklas Boyn ◽  
Kate Jesse ◽  
Andrew McNeece ◽  
...  
Keyword(s):  
Spin Crossover ◽  
Variable Temperature ◽  
Singlet Ground State ◽  
Diverse Range ◽  
Thermally Induced ◽  
Near Ir ◽  
Diradical Character ◽  
Unusual Phenomenon ◽  
Potential Applicability ◽  
External Stimuli

Organic diradicals are uncommon species that have been intensely studied for their unique properties and potential applicability in a diverse range of innovative fields. While there is a growing class of stable and well characterized organic diradicals, there has been recent focus on how diradical character can be controlled or modulated with external stimuli. Here we demonstrate that a diiron complex bridged by the doubly oxidized ligand tetrathiafulvalene-2,3,6,7-tetrathiolate (TTFtt<sup>2−</sup>) undergoes a thermally induced Fe-centered spin-crossover which yields significant diradical character on TTFtt<sup>2−</sup>. UV-vis-Near-IR, Mössbauer, NMR, and EPR spectroscopies with magnetometry, crystallography, and advanced theoretical treatments suggest that this diradical character arises from a shrinking TTFtt<sup>2−</sup> π-manifold from the Fe(II)-centered spin-crossover. The TTFtt<sup>2</sup><sup>− </sup>centered diradical is predicted to have a singlet ground state by theory and variable temperature EPR. This unusual phenomenon demonstrates that inorganic spin transitions can be used to modulate organic diradical character.

scholarly journals Reversible Switching of Organic Diradical Character via Iron-Based Spin-crossover

2020 ◽  
Author(s):  
Airi Kawamura ◽  
Jiaze Xie ◽  
Jan-Niklas Boyn ◽  
Kate Jesse ◽  
Andrew McNeece ◽  
...  
Keyword(s):  
Spin Crossover ◽  
Variable Temperature ◽  
Singlet Ground State ◽  
Diverse Range ◽  
Thermally Induced ◽  
Near Ir ◽  
Diradical Character ◽  
Unusual Phenomenon ◽  
Potential Applicability ◽  
External Stimuli

Organic diradicals are uncommon species that have been intensely studied for their unique properties and potential applicability in a diverse range of innovative fields. While there is a growing class of stable and well characterized organic diradicals, there has been recent focus on how diradical character can be controlled or modulated with external stimuli. Here we demonstrate that a diiron complex bridged by the doubly oxidized ligand tetrathiafulvalene-2,3,6,7-tetrathiolate (TTFtt<sup>2−</sup>) undergoes a thermally induced Fe-centered spin-crossover which yields significant diradical character on TTFtt<sup>2−</sup>. UV-vis-Near-IR, Mössbauer, NMR, and EPR spectroscopies with magnetometry, crystallography, and advanced theoretical treatments suggest that this diradical character arises from a shrinking TTFtt<sup>2−</sup> π-manifold from the Fe(II)-centered spin-crossover. The TTFtt<sup>2</sup><sup>− </sup>centered diradical is predicted to have a singlet ground state by theory and variable temperature EPR. This unusual phenomenon demonstrates that inorganic spin transitions can be used to modulate organic diradical character.

scholarly journals Smart molecular/MoS2 Heterostructures Featuring Light and Thermally-Induced Strain Driven by Spin Switching

2020 ◽  
Author(s):  
Ramón Torres-Cavanillas ◽  
Marc Morant-Giner ◽  
Garin Escorcia-Ariza ◽  
Julien Dugay ◽  
J. Canet-Ferrer ◽  
...  
Keyword(s):  
Spin Crossover ◽  
Molecular System ◽  
Spin States ◽  
Electrical And Optical Properties ◽  
Molecular Sensing ◽  
Thermally Induced ◽  
Covalent Grafting ◽  
External Stimuli ◽  
Hybrid Interface ◽  
Spin Switching

In this work we exploit the ability of spin-crossover molecules to switch between two spin states, upon the application of external stimuli, to prepare smart molecular/2D heterostructures. Through the chemical design of the hybrid interface, that involves a covalent grafting between the two components, we obtain a hybrid heterostructure formed by spin-crossover nanoparticles anchored on chemically functionalized monolayers of semiconducting MoS2. In the resulting hybrid, the strain generated by the molecular system over the MoS2 layer, as a consequence of a thermal or light-induced spin switching, results in a dramatic and reversible change of its electrical and optical properties. This novel class of smart molecular/2D heterostructures could open the way towards a novel generation of hybrid multifunctional materials and devices of direct application in highly topical fields like electronics, spintronics or molecular sensing.

2,6-/1,5-Naphthoquinodimethane bridged porphyrin dimer diradicaloids

2020 ◽  
Vol 24 (01n03) ◽  
pp. 220-229 ◽  
Author(s):  
Hejian Zhang ◽  
Jinseok Kim ◽  
Hoa Phan ◽  
Tun Seng Herng ◽  
Tullimilli Y. Gopalakrishna ◽  
...  
Keyword(s):  
Cross Section ◽  
Near Infrared ◽  
Energy Gap ◽  
Magnetic Measurements ◽  
Variable Temperature ◽  
Photon Absorption ◽  
Singlet Ground State ◽  
Triplet Energy ◽  
Diradical Character ◽  
Cross Section Formula

2,6-Naphthoquinodimethane (2,6-NQDM)- and 1,5-naphthoquinodimethane (1,5-NQDM)-bridged porphyrin dimers, 2,6-P2 and 1,5-P2, were synthesized as relatively stable compounds. Both exhibit open-shell singlet ground state according to variable-temperature (VT) NMR and magnetic measurements, as well as restricted active space spin-flip (RAS-SF) calculations. The 1,5-P2 isomer has a larger diradical character ([Formula: see text], based on the RAS-SF calculations) and smaller singlet-triplet energy gap ([Formula: see text] kcal/mol, based on SQUID measurements) compared to the 2,6-P2 isomer ([Formula: see text], [Formula: see text] kcal/mol). In addition, 2,6-P2 shows intense one-photon absorption (OPA) ([Formula: see text] nm, [Formula: see text] M[Formula: see text] cm[Formula: see text] and a large two-photon absorption (TPA) cross-section ([Formula: see text] GM at 1400 nm) in the near-infrared region, while 1,5-P2 with larger diradical character displays red-shifted but weaker OPA ([Formula: see text] nm, [Formula: see text] M[Formula: see text] cm[Formula: see text] and a smaller TPA cross-section ([Formula: see text] GM at 1600 nm). Both compounds show four reversible redox waves and 1,5-P2 has a smaller electrochemical energy gap (1.06 eV vs.1.16 eV for 2,6-P2). Therefore, the bridge structure has a significant impact on the diradical character, electronic properties, and magnetic behaviors of the obtained porphyrin-based diradicaloids.

scholarly journals Smart molecular/MoS2 Heterostructures Featuring Light and Thermally-Induced Strain Driven by Spin Switching

2020 ◽  
Author(s):  
Ramón Torres-Cavanillas ◽  
Marc Morant-Giner ◽  
Garin Escorcia-Ariza ◽  
Julien Dugay ◽  
J. Canet-Ferrer ◽  
...  
Keyword(s):  
Spin Crossover ◽  
Molecular System ◽  
Spin States ◽  
Electrical And Optical Properties ◽  
Molecular Sensing ◽  
Thermally Induced ◽  
Covalent Grafting ◽  
External Stimuli ◽  
Hybrid Interface ◽  
Spin Switching

In this work we exploit the ability of spin-crossover molecules to switch between two spin states, upon the application of external stimuli, to prepare smart molecular/2D heterostructures. Through the chemical design of the hybrid interface, that involves a covalent grafting between the two components, we obtain a hybrid heterostructure formed by spin-crossover nanoparticles anchored on chemically functionalized monolayers of semiconducting MoS2. In the resulting hybrid, the strain generated by the molecular system over the MoS2 layer, as a consequence of a thermal or light-induced spin switching, results in a dramatic and reversible change of its electrical and optical properties. This novel class of smart molecular/2D heterostructures could open the way towards a novel generation of hybrid multifunctional materials and devices of direct application in highly topical fields like electronics, spintronics or molecular sensing.

Spin-crossover in an iron(iii) complex showing a broad thermal hysteresis

2021 ◽  
Author(s):  
Cyril Rajnák ◽  
Romana Mičová ◽  
Ján Moncoľ ◽  
Ľubor Dlháň ◽  
Christoph Krüger ◽  
...  
Keyword(s):  
Schiff Base ◽  
Schiff Base Ligand ◽  
Spin Crossover ◽  
Thermal Hysteresis ◽  
Mononuclear Complex ◽  
Hysteresis Width ◽  
Thermally Induced

A pentadentate Schiff-base ligand 3,5Cl-L2− and NCSe− form a iron(iii) mononuclear complex [Fe(3,5Cl-L)(NCSe)], which shows a thermally induced spin crossover with a broad hysteresis width of 24 K between 123 K (warming) and 99 K (cooling).

scholarly journals Recent Progress in the Synthesis and Characterization of Diarylethene-based MOFs

2014 ◽  
Vol 70 (a1) ◽  
pp. C1223-C1223
Author(s):  
Jason Benedict ◽  
Ian Walton ◽  
Dan Patel ◽  
Jordan Cox
Keyword(s):  
Chemical Properties ◽  
Building Blocks ◽  
Synthesis And Characterization ◽  
Next Generation ◽  
Design Synthesis ◽  
Thermally Induced ◽  
Potential Applications ◽  
External Stimuli ◽  
Physical And Chemical

Metal-organic Frameworks (MOFs) remain an extremely active area of research given the wide variety of potential applications and the enormous diversity of structures that can be created from their constituent building blocks. While MOFs are typically employed as passive materials, next-generation materials will exhibit structural and/or electronic changes in response to applied external stimuli including light, charge, and pH. Herein we present recent results in which advanced photochromic diarylethenes are combined with MOFs through covalent and non-covalent methods to create photo-responsive permanently porous crystalline materials. This presentation will describe the design, synthesis, and characterization of next-generation photo-switchable diarylethene based ligands which are subsequently used to photo-responsive MOFs. These UBMOF crystals are, by design, isostructural with previously reported non-photoresponsive frameworks which enables a systematic comparison of their physical and chemical properties. While the photoswitching of the isolated ligand in solution is fully reversible, the cycloreversion reaction is suppressed in the UBMOF single crystalline phase. Spectroscopic evidence for thermally induced cycloreversion will be presented, as well as a detailed analysis addressing the limits of X-ray diffraction techniques applied to these systems.

scholarly journals Structural movies of the gradual spin-crossover in a molecular complex at various physical scales

2016 ◽  
Vol 18 (40) ◽  
pp. 28307-28315 ◽  
Author(s):  
S. Lakhloufi ◽  
M. H. Lemée-Cailleau ◽  
G. Chastanet ◽  
P. Rosa ◽  
N. Daro ◽  
...  
Keyword(s):  
Spin State ◽  
Molecular Complex ◽  
Spin Crossover ◽  
Structural Determination ◽  
Thermally Induced ◽  
Mononuclear Iron

The thermally induced Spin-CrossOver (SCO) undergone by the mononuclear iron(ii) complex [Fe(PM-AzA)2(NCS)2] (PM = N-2′-pyridylmethylene, AzA = 4-(phenylazo)aniline) is fully pictured by a quasi-continuous structural determination all along the spin-state modification within the sample.

scholarly journals Quantum Chemical Modeling of Pressure-Induced Spin Crossover in Octahedral Metal-Ligand Complexes

2019 ◽  
Author(s):  
Tim Stauch ◽  
Romit Chakraborty ◽  
Martin Head-Gordon
Keyword(s):  
Carbon Monoxide ◽  
Molecular Electronics ◽  
Spin Crossover ◽  
Strong Field ◽  
Spin Transition ◽  
Nuclear Forces ◽  
Chemical Modeling ◽  
Metal Centers ◽  
State Switching ◽  
External Stimuli

Spin state switching on external stimuli is a phenomenon with wide applicability ranging from molecular electronics to gas activation in nanoporous frameworks. Here we model spin crossover as a function of hydrostatic pressure in octahedrally coordinated transition metal centers by applying a field of effective nuclear forces that compress the molecule towards its centroid. For spin crossover in first-row transition metals coordinated by hydrogen, nitrogen, and carbon monoxide, we find the pressure required for spin transition to be a function of ligand position in the spectrochemical sequence. While pressures on the order of 1 GPa are required to flip spins in homogeneously ligated octahedral sites, we demonstrate a five-fold decrease in spin transition pressure for the archetypal strong field ligand carbon monoxide in octahedrally coordinated Fe<sup>2+</sup> in [Fe(II)(NH<sub>3</sub>)<sub>5</sub>CO]<sup>2+</sup>.

scholarly journals Open-shell Donors and Closed-shell Acceptors in Organic Solar Cells

2021 ◽  
Author(s):  
Zhongxin Chen ◽  
Yuan Li ◽  
Wenqiang Li ◽  
Weiya Zhu ◽  
Miao Zeng ◽  
...  
Keyword(s):  
Solar Cells ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Organic Solar Cells ◽  
Ground State ◽  
Variable Temperature ◽  
Closed Shell ◽  
Open Shell ◽  
Singlet Ground State ◽  
Spin Resonance

The active materials of organic solar cells are widely recognized to show closed-shell singlet ground state and their electron spin resonance signals are attributed to the defects and impurities. Herein, we disclose the inherent open-shell singlet ground state of donors and the closed-shell structure of acceptors via the combination of variable temperature NMR, electron spin resonance, superconducting quantum interference device and theoretical calculation, providing a new perspective to understand the intrinsic molecular structure in organic solar cells.

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