6-Oxophenalenoxyl derivatives covalently linked to TTF moieties: synthesis, ESR/ENDOR measurements, and DFT calculations

Morita, Yasushi; Kawai, Junya; Haneda, Naoki; Nishida, Shinsuke; Fukui, Kozo; Nakazawa, Shigeaki; Shiomi, Daisuke; Sato, Kazunobu; Takui, Takeji; Kawakami, Takashi; Yamaguchi, Kizashi; Nakasuji, Kazuhiro

doi:10.1016/s0040-4039(01)01564-7

Cited by 23 publications

(7 citation statements)

References 19 publications

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“…However, its unique electronic properties have attracted interest towards this molecule from many fields of chemistry. 14 Early works on the preparation of diradicals containing both tetrathiafulvalene and a spin carrier, usually nitrosyl or nitronyl nitroxide groups, linked directly or by a p-benzene group were carried out by Sugawara et al 15,16 and Yamaguchi et al 17,18 Following this line, Pilkington et al have developed recently a new synthetic strategy for the preparation of two stable organic heterospin diradicals, TTF and verdazyl, that are linked covalently through two different bridges, namely a cross conjugated pyridine 19 and an alkene p-system, 20 both of which allow communication via exchange interactions between the unpaired electrons residing on both TTF and verdazyl moieties. Verdazyl radicals constitute an interesting family of radicals which are sufficiently stable to be characterized magnetically 21 and theoretically.…”

Section: Introductionmentioning

confidence: 99%

Towards understanding of magnetic interactions within a series of tetrathiafulvalene–π conjugated-verdazyl diradical cation system: a density functional theory study

Polo

Alberola

Andrés

et al. 2008

Phys. Chem. Chem. Phys.

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The intramolecular magnetic exchange coupling constants (J) for a series of tetrathiafulvalene (TTF) and verdazyl diradical cations connected by a range of pi conjugated linkers have been investigated by means of methodology based on unrestricted density functional theory. The magnetic interaction between radicals is transmitted via pi-electron conjugation for all considered compounds. The calculation of J yields strong or medium ferromagnetic coupling interactions (in the range of 56 and 300 K) for diradical cations connected by linkers with an even number of carbon atoms that are able to provide a spin polarization pathway, while antiferromagnetic coupling is predicted when linkers with an odd number of carbon atoms are employed. The topological analysis of spin density distributions have been used to reveal the effects of the spin polarization on both linkers and spin carriers. The absence of heteroatoms that impede the spin polarization pathway, and the existence of a unique spin polarization path instead of several possible competitive routes are factors which contribute to large positive J values favoring ferromagnetic interactions between the two terminal pi-radicals. The magnitude of J depends strongly on the planarity of the molecular structure of the diradical cation since a more effective orbital overlap between the two pi-systems can be achieved. Hence, the dependence of J on the torsion angle (theta) of each spin carrier has been analyzed. In this respect, our findings show that this geometrical distortion reduces largely the calculated J values for ferromagnetic couplings, leading to weak antiferromagnetic interactions for a torsion angle of 90 degrees .

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Section: Introductionmentioning

confidence: 99%

Towards understanding of magnetic interactions within a series of tetrathiafulvalene–π conjugated-verdazyl diradical cation system: a density functional theory study

Polo

Alberola

Andrés

et al. 2008

Phys. Chem. Chem. Phys.

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“…The assembly strategy follows mainly the already reported syntheses of phenalenyl and oxophenalenoxyl derivatives. 49 , 51 , 53 , 58…”

Section: Resultsmentioning

confidence: 99%

“…The syntheses towards the key intermediate 14 were performed by adapting previously reported protocols for phenalenyl and oxophenalenoxyl derivatives ( Scheme 2A ). 49 , 51 , 53 , 58 The required 2,7-diboromo-3,6-dimethoxynaphthalene 8 was obtained by bromination of naphthalene-2,7-diole 6 in AcOH, followed by dehalogenation with tin in AcOH to afford 7 , which was further methylated with methyl iodide and potassium carbonate in acetone giving 8 . In our experiment, the literature-known 2,7-dibromo-3,6-dimethoxynaphthalene 8 was obtained in 78% yield over three steps.…”

Section: Synthesismentioning

confidence: 99%

2,5-Diaryl 6-hydroxyphenalenones for Single-Molecule Junctions

et al. 2022

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A modular access to 2,5-diaryl 6-hydroxyphenalenone derivatives is developed and demonstrated by a small series of 5 molecules. Within this series, the structures 1 and 2 expose terminal methylsulfanyl anchor groups, enabling their integration in a single molecule junction. The modular synthesis is based on Suzuki cross coupling of the aryl substituents as boronic acid precursors with 5,8-dibromo-2-(tert.butyl)-4,9-dimethoxy-2,3-dihydro-1H-phenalen-1-one, and the subsequent transformation of the product to the desired 2,5-diaryl 6-hydroxyphenalenone in a reduction/deprotection sequence. The new structures are fully characterized and their optical and electrochemical properties are analysed. For the derivatives 1 and 2 suitable for single molecule junctions, the corresponding oxophenalenoxyl radicals 1R and 2R were obtained by oxidation and analysed by EPR-spectroscopy. Preliminary mechanical break junction experiments with 1 display the structure’s ability to form transient single molecule junctions. The intention behind the molecular design is to profit from the various redox states of the structure (including the neutral radical) as molecular switch in an electro-chemically triggered single molecule transport experiment.

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“…Its unique electronic properties have drawn attention toward this molecule from various fields of chemistry . Research has been carried out on the synthesis of diradicals containing both tetrathiafulvalene and a spin carrier, usually nitrosyl or nitronyl nitroxide group, linked directly or by a p -benzene group, by Sugawara et al , and Yamaguchi et al , Pilkington et al , investigated mixed diradicals constructed from TTF and verdazyl and found moderately high and positive magnetic exchange coupling constants ( J , on the order of 167 cm −1 ) for most of them . This observation gave rise to our interest in TTF-NN mixed diradicals.…”

Section: Introductionmentioning

confidence: 99%

Very Strongly Ferromagnetically Coupled Diradicals from Mixed Radical Centers. II. Nitronyl Nitroxide Coupled to Tetrathiafulvalene via Spacers

et al. 2010

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We predict large and positive intramolecular magnetic exchange coupling constants (J) for coupled diradicals constructed from nitronyl nitroxide and tetrathiafulvalene monoradical moieties. These diradicals have the general formula TTF-coupler-NN, where the couplers are mostly aromatic systems. Unrestricted density functional methodology (UB3LYP) has been used to optimize the molecular geometries of the triplet diradicals using the 6-311 g(d,p) basis set. This has been followed by single-point UB3LYP calculations for triplet and broken symmetry (BS) states using 6-311++g(3df,3pd) basis and the optimized triplet geometries. We find that the species comprising of ethylene (geminal coupling) and pyridine as couplers have singlet ground states whereas the other species have triplet ground states. These findings are in support of the spin alternation rule. The largest J value we predict is 648.6 cm(-1) for the molecule with the spacer pyrrole. We also determine the percent weightings of triplet and singlet components in the BS state, estimate the diradical nature, and calculate the relative weights of different singlet and triplet component functions in the BS solution in each case.

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6-Oxophenalenoxyl derivatives covalently linked to TTF moieties: synthesis, ESR/ENDOR measurements, and DFT calculations

Cited by 23 publications

References 19 publications

Towards understanding of magnetic interactions within a series of tetrathiafulvalene–π conjugated-verdazyl diradical cation system: a density functional theory study

Towards understanding of magnetic interactions within a series of tetrathiafulvalene–π conjugated-verdazyl diradical cation system: a density functional theory study

2,5-Diaryl 6-hydroxyphenalenones for Single-Molecule Junctions

Very Strongly Ferromagnetically Coupled Diradicals from Mixed Radical Centers. II. Nitronyl Nitroxide Coupled to Tetrathiafulvalene via Spacers

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