Stable Radicals of the Heavy p‐Block Elements

Konu, Jari; Chivers, Tristram

doi:10.1002/9780470666975.ch10

Cited by 21 publications

(4 citation statements)

References 73 publications

(59 reference statements)

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“…From a practical perspective, the greatest challenges for the future, but also the greatest opportunities, lie in chemical synthesis, the demanding task of designing, building, and then crystallizing stable, main group heavy atom radicals in which dimerization is suppressed, and yet strong 3D magnetic exchange networks are preserved. While the neutral S–N and Se–N heterocycles described here have provided a rich array of magnetically active materials, exploration of π-delocalized inorganic ring systems based on other heavy p-block elements may eventually prove equally rewarding . In this regard, an understanding of the structural properties of Te–N heterocycles is steadily emerging and may yield breakthroughs.…”

Section: Future Prospectsmentioning

confidence: 95%

Magnetic Ordering and Anisotropy in Heavy Atom Radicals

2015

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Recent developments in stable radical chemistry have afforded "heavy atom" radicals, neutral open-shell (S = 1/2) molecular species containing heavy p-block elements (S, Se), which display solid-state magnetic properties once considered exclusive to conventional metal-based magnets. These highly spin-delocalized radicals do not associate in the solid state and yet display extensive networks of close intermolecular interactions. Spin density on the heavy atoms allows for increased isotropic and spin-orbit mediated anisotropic exchange effects. Structural variations induced by chemical modification and physical pressure, coupled with ab-initio methods to estimate exchange energies, have facilitated the development of predictive structure/property relationships. These results, coupled with detailed theoretical analyses and magnetic resonance spectroscopic measurements, have provided insight into the magnetic structure of ferromagnetic and spin-canted antiferromagnetic ordered materials as well as an understanding of the importance of spin-orbit coupling contributions to magnetic hysteresis and anisotropy. Isotropic and anisotropic ferromagnetic exchange can also be enhanced indirectly by the incorporation of heavy atoms into nonspin-bearing sites, where they can contribute to multi-orbital spin-orbit coupling.

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Section: Future Prospectsmentioning

confidence: 95%

Magnetic Ordering and Anisotropy in Heavy Atom Radicals

2015

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“…Main-group element radicals are typically transient species, which are formed as highly reactive intermediates in many transformation reactions and chemical processes . Persistent carbon-centered radicals such as the triphenyl methyl radical Ph 3 C· (Gomberg radical), which was initially reported more than 100 years ago, are still intensely studied, and the structure-directing role of dispersion interactions in triaryl methyl radicals was only recently demonstrated. , In addition, main-group element radicals containing the lighter elements, i.e., boron, silicon, and nitrogen, also have been studied to some extent, whereas the number of persistent or stable radicals of heavier main-group elements is still limited, , even though new strategies to stabilize these highly reactive species including coordination of σ-donating carbenes have been developed in the past decade. − …”

Section: Introductionmentioning

confidence: 99%

Synthesis of a Ga-Stabilized As-Centered Radical and a Gallastibene by Tailoring Group 15 Element–Carbon Bond Strengths

et al. 2019

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A convenient synthetic route to Ga-stabilized pnictogen-centered radicals and gallapnictenes by manipulation of pnictogen-carbon bond strengths is presented. Two equivalents of LGa (L = HC[C(Me)N(Dip)]2, Dip = 2,6-i-Pr2C6H3) react with Cp Ar AsCl2 (Cp Ar = C5(4-t-BuC6H4)5) with formation of the arsenic-centered radical [L(Cl)Ga]2As• 1. In contrast, the analogous reaction with TerSbCl2 (Ter = 2,6-Mes2C6H3; Mes = 2,4,6-Me3C6H2) yields the gallastibene LGa=SbTer 2 containing a Ga-Sb double bond, whereas reactions of DipSbCl2 with one and two equivalents of LGa give the monoinsertion and bisinsertion products L(Cl)GaSb(ClDip 3 and [L(Cl]Ga]2SbDip 4, respectively. 1 -4 were structurally characterized by single crystal X-ray diffraction. The description of 1 as arsenic-centered radical is consistent with results of EPR and DFT studies. The π-bonding in LGa=SbTer 2 is estimated to 10.68 kcal mol -1 by variable-temperature (VT) NMR spectroscopy, and DFT studies reveal a significant π-bonding interaction between Sb and Ga. ASSOCIATED CONTENTThe Supporting Information is available free of charge via the Internet at http://pubs.acs.org. Experimental procedures, 1 H, 13 C NMR, IR and EPR spectra, crystallographic details, bond lengths and angles of 1 -4 and results from quantum chemical calculations (pdf).

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“…The bond lengths of N1–O1 and N2–O2 are 1.272(2) and 1.279(2) Å, typical of NITR radicals. 25 The O–N–C–N–O part is nearly coplanar as expected due to orbital conjugation, but forms a dihedral angle of 53.67° with the 2-TrzPm group, which is close to the dihedral angle in other related radicals of the functionalized benzimidazole rings (NITBzImH and NITMeBzImH). 12 The assignment of the nitrogen atoms in 2-TrzPm is according to the molecular structure of 2-TrzPm, together with the diffraction data.…”

Section: Resultsmentioning

confidence: 57%