Crystal Engineering of Tolane Bridged Nitronyl Nitroxide Biradicals: Candidates for Quantum Magnets

Physica Status Solidi (b)

2019

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An overview of organic biradicals directed towards triplon excitations in higher ordered crystalline states is provided. The topic started from the idea to control the intramolecular spin exchange interaction in a sizable but not too large extent, in order to provide also decent intermolecular spin interactions in a crystalline lattice. The predictability of exchange couplings through DFT calculations of optimized geometries turns out to be limited, such that the molecules need to be synthesized and crystallized for further in‐depth characterizations. For crystal structure geometries, most often then a good agreement of calculated intra‐ and intermolecular exchange interactions with those later determined experimentally is found. Finally, it is demonstrated that by choosing well balanced size of both interactions a field‐induced higher ordered magnetic state becomes accessible.

Section: Resultsmentioning

confidence: 97%

Tuning the Magnetic Exchange Interactions in Organic Biradical Networks

Physica Status Solidi (b)

2019

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“…Serendipitously during the course of our study on organic biradical systems for the Bose-Einstein condensation we found the molecule BPNO (N,N'-([1,1'-biphenyl]-4,4'-diyl)bis(N-(tertbutylaminoxyl)) which exists in semi-quinoid form ( Figure 3). [27][28][29] At room temperature BPNO showed doublet EPR spectrum. Even after several purifications by column followed by repetitive crystallization no improvement in EPR spectrum was observed.…”

Section: Introductionmentioning

confidence: 98%

“Tschitschibabin type biradicals”: benzenoid or quinoid?

Ravat

Phys. Chem. Chem. Phys.

2015

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Our findings provide a better understanding of the discrepancies related to the discussion in the literature on the ground state of Tschitschibabin's hydrocarbon. A series of phenylene bridged bisnitroxide molecules were designed and studied for the comparison. The simple theoretical and experimental methodologies have been developed and utilized to understand the singlet biradicaloids which exist in semi-quinoid form and exhibits characteristics of biradicaloid and quinoid form simultaneously.

“…[21][22] The calculations were executed with the Gaussian 09 program package 23 employing the unrestricted 24 BLYP functional [25][26][27] and the 6-31G(d) basis set. 28 The geometry of biradical 2,7-TMPNO was taken from X-ray diffraction determinations without further optimization.…”

Section: Dft Calculationsmentioning

confidence: 99%

Positional Isomers of Tetramethoxypyrene-based Mono- and Biradicals

Ravat

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.