Radicals organized by disk shaped aromatics – polymorphism and co-crystals that tune inter-electron exchange

Akpinar, Handan; Mague, Joel T.; Novak, Miguel A.; Friedman, Jonathan R.; Lahti, Paul M.

doi:10.1039/c1ce06096a

Cited by 20 publications

(19 citation statements)

References 39 publications

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“…Infrared (IR) spectra were recorded using a Bruker Alpha FTIR spectrophotometer with attenuated total reflectance (ATR) accessory. The radicals PyrNN and PyrIN were synthesized according to previously described procedures [19]. Reflectance spectra were obtained using an Ocean Optics USB2000+ VIS-NIR spectrometer.…”

Section: General Methodsmentioning

confidence: 99%

Copper(II) coordination compounds with sterically constraining pyrenyl nitronyl nitroxide and imino nitroxide

2016

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2-(1'-Pyrenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (PyrNN) and 2-(1'-pyrenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl (PyrIN) form pentacoordinate metal-radical complexes with Cu(hfac) 2 : [Cu(hfac) 2 PyrNN] and [Cu(hfac) 2 PyrIN], 1 and 2, respectively. In 1, one aminoxyl unit of PyrNN coordinates to Cu(II) in a distorted square pyramidal environment. In 2, an unusual example of monodentate Cu-N coordination of the imino nitroxide, PyrIN, gives an environment intermediate between square pyramidal and trigonal bipyramid. Both complexes show novel close contacts of the pyrene π-electron cloud with the Cu(II) ion. Compound 1 has a particularly short Cu-O(N) bond of 1.948 Å, giving strong intramolecular antiferromagnetic (AFM) spin-pairing and an absence of significant paramagnetic susceptibility response. The magnetic behavior of compound 2 indicates copper-radical intramolecular ferromagnetic exchange of 2J = 151 cm-1 , and intermolecular AFM spin pairing of 2J =-220 cm-1 due to close antiparallel contacts between non-coordinated NO units. EPR spectra for both complexes are silent at 293 and 77 K. UB97D/6-31G(d) computations find strong antiferromagnetic (2J =-213 cm-1) and ferromagnetic (2J = 610 cm-1) intramolecular metalradical exchange in 1 and 2, respectively in agreement with experimental results.

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Section: General Methodsmentioning

confidence: 99%

Copper(II) coordination compounds with sterically constraining pyrenyl nitronyl nitroxide and imino nitroxide

2016

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“…m.p. : 190–191 °C26b); EPR (toluene, 9.65 GHz): 7.2 gauss (2 N); MS (FAB): m / z : calcd for C 23 H 21 N 2 O 2 : 357.2; found: 357.2.…”

Section: Methodsmentioning

confidence: 99%

A Cobalt Pyrenylnitronylnitroxide Single‐Chain Magnet with High Coercivity and Record Blocking Temperature

Vaz

Cassaro

Akpinar

et al. 2014

Chemistry A European J

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104

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Coordination of a [Co(hfac)2] moiety (hfac = hexafluoroacetylacetonate) with a nitronylnitroxide radical linked to bulky, rigid pyrene (PyrNN) gives a helical 1:1 chain complex, in which both oxygen atoms of the radical NO(·) groups are bonded to Co(II) ions with strong antiferromagnetic exchange. The complex shows single-chain magnet (SCM) behavior with frequency-dependent magnetic susceptibility, field-cooled and zero-field-cooled susceptibility divergence with a high blocking temperature of around 14 K (a record among SCMs), and hysteresis with a very large coercivity of 32 kOe at 8 K. The magnetic behavior is partly related to good chain isolation induced by the large pyrene units. Two magnetic relaxation processes have been observed, a slower one attributable to longer, and a faster one attributable to short chains. No evidence of magnetic ordering has been found.

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“…[5][6] Lately the stable aminoxyl radicals attached to several polyaromatic hydrocarbons (PAH) have been synthesized and proved their application in rechargeable batteries, sensors, organic field effect transistors and quantum magnets. [7][8][9][10][11][12] The PAH bearing aminoxyl radical moieties are also found to exhibit photoexcited high spin states. [13][14] The enhanced photo-stability of pentacene was achieved by attaching the nitronylnitroxide moiety.…”

Section: Introductionmentioning

confidence: 98%

Positional Isomers of Tetramethoxypyrene-based Mono- and Biradicals

Ravat

Baumgarten

2015

J. Phys. Chem. B

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The positional isomers of tert-butylnitroxide (NO) substituted 4,5,9,10-tetramethoxypyrene-based mono- and biradical are synthesized. While the biradical 2,7-TMPNO in which two NO radical moieties are attached at the nodal plane of pyrene adopts a semiquinoid structure, the 1,6- and 1,8-isomers of the same exist in biradical form. The tuning of the antiferromagnetic exchange interactions is achieved by synthesizing the positional isomers of the biradical while maintaining the same radical moiety as well as the π spacer.

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Radicals organized by disk shaped aromatics – polymorphism and co-crystals that tune inter-electron exchange

Cited by 20 publications

References 39 publications

Copper(II) coordination compounds with sterically constraining pyrenyl nitronyl nitroxide and imino nitroxide

Copper(II) coordination compounds with sterically constraining pyrenyl nitronyl nitroxide and imino nitroxide

A Cobalt Pyrenylnitronylnitroxide Single‐Chain Magnet with High Coercivity and Record Blocking Temperature

Positional Isomers of Tetramethoxypyrene-based Mono- and Biradicals

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