Spin‐crossover (SCO) active transition metal complexes are an important class of switchable molecular materials due to their bistable spin‐state switching characteristics at or around room ...temperature. Vacuum‐sublimable SCO complexes are a subclass of SCO complexes suitable for fabricating ultraclean spin‐switchable films desirable for applications, especially in molecular electronics/spintronics. Consequently, on‐surface SCO of thin‐films of sublimable SCO complexes have been studied employing spectroscopy and microscopy techniques, and results of fundamental and technological importance have been obtained. This Review provides complete coverage of advances made in the field of vacuum‐sublimable SCO complexes: progress made in the design and synthesis of sublimable functional SCO complexes, on‐surface SCO of molecular and multilayer thick films, and various molecular and thin‐film device architectures based on the sublimable SCO complexes.
This review provides a complete account of the on‐surface spin‐state switching behavior of films of spin‐crossover (SCO) complexes of molecular to multilayer thickness. SCO‐based molecular and thin‐film device architectures fabricated employing vacuum sublimation are also described.
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•Recent trends and advances in spin crossover (SCO) research direction are reviewed.•SCO active hybrid materials (molecules, nanoparticles) have been synthesized.•The application ...potential of SCO complexes in various fields is elaborated.•Electrical and spin transport characteristics of SCO active entities are discussed.
The design and synthesis of functional molecules with controllable properties are at the forefront of modern materials chemistry research due to their diverse applicability, especially in device miniaturization. Spin crossover (SCO) complexes can be switched between low (LS) and high spin (HS) magnetic states with the help of an external perturbation, and are promising candidates for the realization of molecule-based electronic and spintronic components, such as switching and memory elements. Although the area is relatively old and a multitude of SCO active transition metal complexes of d4-d7 electronic configuration have been reported, the field continues to grow, and several interesting research directions have emerged. In this context, the present review attempts to give a concise overview of recent trends in SCO research. Attempts devoted towards rendering multifunctionality to the SCO systems in order to bridge the gap between laboratory and reality, and efforts made to study spin state dependence of physical property modulation such as electrical conductance from single molecule level to bulk, prerequisite for the realization of SCO-based devices, are emphasized by discussing the most relevant past and recent literature.
The success of the emerging field of solid-state optical quantum information processing (QIP) critically depends on the access to resonant optical materials. Rare-earth ion (REI)-based molecular ...systems, whose quantum properties could be tuned taking advantage of molecular engineering strategies, are one of the systems actively pursued for the implementation of QIP schemes. Herein, we demonstrate the efficient polarization of ground-state nuclear spins-a fundamental requirement for all-optical spin initialization and addressing-in a binuclear Eu(III) complex, featuring inhomogeneously broadened
D
→
F
optical transition. At 1.4 K, long-lived spectral holes have been burnt in the transition: homogeneous linewidth (Γ
) = 22 ± 1 MHz, which translates as optical coherence lifetime (T
) = 14.5 ± 0.7 ns, and ground-state spin population lifetime (T
) = 1.6 ± 0.4 s have been obtained. The results presented in this study could be a progressive step towards the realization of molecule-based coherent light-spin QIP interfaces.
The realization of spin‐crossover (SCO)‐based applications requires study of the spin‐state switching characteristics of SCO complex molecules within nanostructured environments, especially on ...surfaces. Except for a very few cases, the SCO of a surface‐bound thin molecular film is either quenched or heavily altered due to: (i) molecule–surface interactions and (ii) differing intermolecular interactions in films relative to the bulk. By fabricating SCO complexes on a weakly interacting surface, the interfacial quenching problem is tackled. However, engineering intermolecular interactions in thin SCO active films is rather difficult. Here, a molecular self‐assembly strategy is proposed to fabricate thin spin‐switchable surface‐bound films with programmable intermolecular interactions. Molecular engineering of the parent complex system Fe(H2B(pz)2)2(bpy) (pz = pyrazole, bpy = 2,2′‐bipyridine) with a dodecyl (C12) alkyl chain yields a classical amphiphile‐like functional and vacuum‐sublimable charge‐neutral FeII complex, Fe(H2B(pz)2)2(C12‐bpy) (C12‐bpy = dodecyl2,2′‐bipyridine‐5‐carboxylate). Both the bulk powder and 10 nm thin films sublimed onto either quartz glass or SiOx surfaces of the complex show comparable spin‐state switching characteristics mediated by similar lamellar bilayer like self‐assembly/molecular interactions. This unprecedented observation augurs well for the development of SCO‐based applications, especially in molecular spintronics.
Self‐assembly and spin crossover go hand in hand, leading to the realization of comparable spin‐state switching characteristics of a pseudoamphiphilic charge‐neutral and vacuum‐sublimable functional SCO complex in bulk and thin film states with implications for the development of large‐area spintronics devices based on SCO complexes.
Studies on the spin-state switching characteristics of surface-bound thin films of spin-crossover (SCO) complexes are of interest to harness the device utility of the SCO complexes. ...Molecule–substrate interactions govern the SCO of surface-bound films in direct contact with the underlying substrates. In this study, we elucidate the role of molecule–substrate interactions on the thermal- and light-induced spin-state switching characteristics of a functional SCO-complexFe(H2B(pz)2)2COOC12H25-bipy (pz = pyrazole, C12-bpy = dodecyl2,2′-bipyridine-5-carboxylate) deposited at a submonolayer coverage on a highly oriented pyrolytic graphite (HOPG) substrate. A spin-state coexistence of 42% low-spin (LS) and 58% high-spin (HS) is observed for the 0.4 ML deposit of the complex at 40 K, in contrast to the complete spin-state switching observed in the bulk and in SiO x -bound 10 nm thick films. Cooling the sample to 10 K results in a decrease of the LS fraction to 36%, attributed to soft-X-ray-induced excited spin-state trapping (SOXIESST). Illumination of the sample with a green light (λ = 520 nm) at 10 K caused the LS-to-HS switching of the remaining (36%) LS complexes, by a process termed light-induced excited spin-state trapping (LIESST). The mixed spin-state in the submonolayer coverage of Fe(H2B(pz)2)2COOC12H25-bipy highlights the role of molecule–HOPG substrate interactions in tuning the thermal SCO characteristics of the complex. The 100% HS state obtained after light irradiation indicates the occurrence of efficient on-surface light-induced spin switching, encouraging the development of light-addressable molecular devices based on SCO complexes.
An erbium triple‐decker complex featuring a 9,10‐diborataanthracene middle deck and two substituted cyclooctatetraene outer decks is depicted on the cover. The magnetic interaction between the two ...erbium ions is highlighted, since the title compound allows the evaluation of the 9,10‐diborataanthracene ligand for possible exchange interactions. In addition, the two ligands that compose the triple‐decker complexes are displayed. The title compound represents the first triple‐decker complexes of lanthanides with a six‐membered ring, as illustrated by Eufemio Moreno‐Pineda, Peter W. Roesky et al. in their Research Article (e202401372).
Herein, we present the first report on the synthesis of rare‐earth complexes featuring a 9,10‐diborataanthracene ligand. This 14‐π‐electron ligand is highly reductive and was previously used in ...small‐molecule activation. Salt elimination reactions between dipotassium 9,10‐diethyl‐9,10‐diborataanthracene K2(DEDBA) and LnIII(η8‐CotTIPS)(BH4)(thf)x (CotTIPS=1,4‐(iPr3Si)2C8H6) in a 1 : 1 ratio yielded heteroleptic sandwich complexes K(η8‐CotTIPS)LnIII(η6‐DEDBA) (Ln=Y, Dy, Er). These compounds form Lewis‐base‐free one‐dimensional coordination polymers when crystallised from toluene. In contrast, reaction of K2(DEDBA) and LnIII(η8‐CotTIPS)(BH4)(thf)x in a 1 : 2 ratio led to the formation of heteroleptic triple‐decker complexes (η8‐CotTIPS)LnIII(μ‐η6:η6‐DEDBA)LnIII(η8‐CotTIPS) (Ln=Y, Dy, Er). Notably, these are not only the first lanthanide triple‐decker compounds featuring a six‐membered ring as a deck but also the first trivalent lanthanide triple‐decker featuring a heterocycle in the coordination sphere. Magnetic investigations reveal that K(η8‐CotTIPS)LnIII(η6‐DEDBA) (Ln=Dy, Er) and (η8‐CotTIPS)ErIII(μ‐η6:η6‐DEDBA)ErIII(η8‐CotTIPS) exhibit Single‐Molecule Magnet (SMM) behaviour. In the case of (η8‐CotTIPS)LnIII(μ‐η6:η6‐DEDBA)LnIII(η8‐CotTIPS) (Ln=Dy, Er), the introduction of a second near lanthanide ion results in strong antiferromagnetic interactions, allowing the enhancement of the magnetic characteristic of the system, compared to the quasi isolated counterpart. This research renews the overlooked coordination chemistry of the DBA ligand and expands it to encompass rare‐earth elements.
The first rare‐earth complexes featuring diborataanthracene ligands are showcased. These are not only the first lanthanide triple‐decker compounds featuring a six‐membered ring as a deck but also the first lanthanide triple‐decker featuring a heterocycle in the coordination sphere.
Sunflower oil with high oleic acid content is in great demand due to its nutritional as well as industrial benefits. The trait is mainly controlled by dominant alleles at a major gene,
Ol
, with ...other modifiers. The objectives of this research were to map the oil content, oleic acid and linoleic acid content in sunflower seeds. An F2 mapping population from cytoplasmic male-sterile line COSF 7A (33–35 % oleic acid) and high oleic acid inbred line HO 5–13 (88–90 % oleic acid) was developed and phenotyped for oil content, oleic acid and linoleic acid content at the F2 seed level. High phenotypic and genotypic coefficients of variation were recorded for oleic acid and linoleic acid content. High heritability and high genetic advance as percent of mean was recorded for oleic acid and linoleic acid content. This indicated the presence of the additive type of gene action controlling the traits oleic acid content and linoleic acid content. The
Ol
gene was mapped to linkage group (LG) 14 and tightly linked to the marker HO_Fsp_b. In addition, two more quantitative trait loci (QTLs) for oleic acid content were identified in LG8 and LG9. Two QTLs for oil content and two QTLs for linoleic acid content were also identified. All these QTLs explained over 10 % of phenotypic variation. A study was conducted with 13 genotypes differing in oil quality as well as quantity over three seasons to assess the reliability of the identified QTLs over seasons. It resulted in the identification of two potential QTLs for oleic acid as well as linoleic acid content with the markers ORS 762 and HO_Fsp_b. These markers explained more than 57.6–66.6 % of phenotypic variation. Hence it can be concluded that these markers/QTLs would be useful in the marker-assisted selection breeding programme to improve oil quality. The present study also indicated the presence of at least two other genomic regions controlling oleic and linoleic acid content in sunflower.
Abstract
Wegen ihres bistabilen, bei Raumtemperatur schaltbaren Spinzustands bilden aktive Übergangsmetallkomplexe mit Spin‐Crossover (SCO) eine wichtige Gruppe von schaltbaren molekularen ...Materialien. Aus vakuumsublimierbaren SCO‐Komplexen, einer Untergruppe der SCO‐Komplexe, lassen sich ultrareine Filme mit schaltbarem Spin herstellen, wie sie insbesondere in der molekularen Elektronik/Spintronik benötigt werden. Dünne Filme aus sublimierbaren SCO‐Komplexen wurden deshalb mit spektroskopischen und mikroskopischen Techniken auf ihren oberflächenabhängigen SCO untersucht. In diesem Aufsatz werden vakuumsublimierbare SCO‐Komplexe und ihre Entwicklung umfassend beschrieben, insbesondere die Fortschritte im Design und in der Herstellung von sublimierbaren funktionalen SCO‐Komplexen, in der Ausprägung desoberflächenabhängigen SCO in molekularen Multilagenfilmen und die Konstruktion von Bauelementen mit molekularen Dünnschicht‐Architekturen von sublimierbaren SCO‐Komplexen als aktive Schaltelemente.
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