From High-Spin Organic Molecules to Organic Polymers with Magnetic Ordering

Rajca, Andrzej

doi:10.1002/1521-3765(20021104)8:21<4834::aid-chem4834>3.0.co;2-e

Cited by 138 publications

(112 citation statements)

References 34 publications

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“…Binding studies by UV−vis were performed to obtain a binding isotherm and fitted with a 2:1 binding equation to obtain the two macroscopic association constants (see Supporting Information for details). A Hill coefficient of 0.59 was obtained for 2 with CB [7], suggesting a negative cooperativity of binding. A macroscopic K a1 of 3.0 × 10 4 M −1 , with an error of less than 15%, for 2 with CB [7] was obtained, which is within error of other values for unlinked viologen radical cations with CB [7].…”

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confidence: 99%

“…A Hill coefficient of 0.59 was obtained for 2 with CB [7], suggesting a negative cooperativity of binding. A macroscopic K a1 of 3.0 × 10 4 M −1 , with an error of less than 15%, for 2 with CB [7] was obtained, which is within error of other values for unlinked viologen radical cations with CB [7]. 34 It should be noted that we also detect by EPR the single-line spectrum of the radical anion of SO 2 in addition to 2.…”

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confidence: 99%

“…22−28 Notably, it has been reported that viologen cation radicals exist in equilibrium with a diamagnetic dimer in solution. 23,24,26 In other studies, it has been shown that viologen dications and viologen cation radicals form noncovalent complexes with CB [7], a supramolecular host consisting of seven methylene-linked glycouril units wrapped into a macrocyclic container. 29−34 Thus, we considered it might be possible to synthesize a viologen cation radical that could be switched between diamagnetic and paramagnetic forms using noncovalent chemistry with CB [7].…”

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confidence: 99%

“…35,36 In particular, a three-carbon tether unit has been shown to lead to efficient intramolecular dimerization for viologen. 23,37,38 Thus, we synthesized the propyl-tethered bis(viologen) dication diradical 2 that has a concentration-independent intramolecular dimerization switchable between diamagnetic and paramagnetic forms using noncovalent chemistry with CB [7] (see Figure 1). The results of EPR titration studies, UV−vis switching studies, and computational studies indicate the propyl-linked bis(viologen) dication diradical 2 is a diamagnetic species that can be switched to the paramagnetic form by formation of a ternary complex with CB [7].…”

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confidence: 99%

“…18,23,25 Compound 2 has a max absorption at 850 nm, while the free radical has a max absorption at 760 nm (See Figure 3), which allowed for identification of the state of the compound during cycling. We cycled this switch five times by alternating addition of 2 equiv of CB [7] with 2 equiv of 3 in a cuvette and inspecting the dilution-corrected absorbances. The 5 cycles show complete return to the diamagnetic dimer.…”

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A Noncovalently Reversible Paramagnetic Switch in Water

et al. 2013

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We report an organo-paramagnetic switch consisting of a linked bis(viologen) dication diradical that can be cycled reversibly between diamagnetic and paramagnetic states via noncovalent guest-host chemistry with cucurbit [7]uril (CB[7]) in room-temperature water. Computations suggest that the nature of the interaction between the viologen cation radical units is that of a pi dimer (pimer). Molecules with switchable magnetic properties have possible applications in spintronics, data storage devices, chemical sensors, building blocks for materials with switchable bulk magnetic properties, as well as magnetic resonance probes for biological applications. DisciplinesOrganic Chemistry | Other Chemistry | Physical Chemistry CommentsReprinted (adapted) with permission from J. Am. Chem. Soc., 2013, 135 (29) O rganic molecules with magnetic properties hold promise

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A Noncovalently Reversible Paramagnetic Switch in Water

et al. 2013

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The Synthesis and Characterization of Stable Radicals Containing the Thiazyl (SN) Fragment and Their Use as Building Blocks for Advanced Functional Materials

Hicks

2010

Stable Radicals

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Diradicals and Carbenes

Bachrach

2014

Computational Organic Chemistry

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Reactive intermediates play a critical role in the chemist's understanding of many reaction mechanisms. 1 Given their often fleeting appearance, experimental observation, let alone acquiring any property data on them, can be a great challenge. It is not, therefore, surprising that computational chemistry has been a strong partner with experiment in gaining knowledge of a broad spectrum of reactive intermediates.In this chapter, we focus on the class of reactive intermediates that bear at least two unpaired electrons: diradicals and carbenes. The exact definition of a diradical is somewhat in the eye of the beholder. Salem and Rowland 2 provided perhaps the most general, yet effective, definition-a diradical is a molecule that has two degenerate or nearly degenerate orbitals occupied by two electrons. With this definition, carbenes can be considered as a subcategory of diradicals. In a carbene, the two degenerate molecular orbitals are localized about a single carbon atom.The chemistry of radicals has been described many times. 3 -6 Likewise, the chemistry of diradicals and carbenes has been the subject of many reviews. 7 -16 Two issues will guide our presentation in this chapter. First and foremost, we discuss examples of diradicals and carbenes, where computational chemistry has greatly aided in understanding the properties, structure, and chemistry of these intermediates. A theme that will emerge here is the strong collaborative relationship between experimental and computational chemists that greatly aided in resolving the controversies and discrepancies that arose in trying to understand these unusual species. The second aspect of this chapter is that computational studies of diradicals and (especially) carbenes helped to establish the discipline of computational chemistry. In fact, the first example we discuss in this chapter is the nature of methylene, which is the topic that many claim to have single handedly won over skeptics to the advantages and power of computational chemistry.Following the section on methylene, we present the chemistry of phenylcarbene and phenylnitrene and describe how computational chemistry helped detail why these two closely related molecules behave so differently. A discussion of tetramethyleneethane (TME) and oxyallyl diradicals explores how theories of apparently simple molecules may be quite complicated. Next, we discuss the chemistry of Computational Organic Chemistry, Second Edition. Steven M. Bachrach

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From High-Spin Organic Molecules to Organic Polymers with Magnetic Ordering

Cited by 138 publications

References 34 publications

A Noncovalently Reversible Paramagnetic Switch in Water

A Noncovalently Reversible Paramagnetic Switch in Water

The Synthesis and Characterization of Stable Radicals Containing the Thiazyl (SN) Fragment and Their Use as Building Blocks for Advanced Functional Materials

Diradicals and Carbenes

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