Preparation of meso-tetra(4-galvinolphenyl)porphyrin—A building block for molecular magnetic materials

Shultz, David A.; Knox, D. A.; Morgan, Larry W.; Sandberg, Kay A.; Tew, Gregory N.

doi:10.1016/s0040-4039(00)60593-2

Cited by 8 publications

(7 citation statements)

References 22 publications

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“…[19][20][21][22][23][24][25][26][27][28][29][30][31] Recent examples include porphyrins bearing phenyl carbene groups, 32,33 manganese(II) porphyrin-tetracyanoethylene complexes, 34 tetragalvinolphenyl and bis(semiquinone)porphyrin systems. 35,36 In π-conjugated molecular systems such as these, the relationship between the sign of the exchange coupling and the orbital topology is well understood. [37][38][39] However, controlling its magnitude is challenging because it is highly dependent on the molecular structure.…”

Section: Introductionmentioning

confidence: 99%

Spin−Spin Interactions in Porphyrin-Based Monoverdazyl Radical Hybrid Spin Systems

Poddutoori

Pilkington²,

Alberola

et al. 2010

Inorg. Chem.

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The spin-spin interactions in a complex consisting of a metalloporphyrin with a verdazyl radical attached at one of the beta positions of the porphyrin ring are investigated. The X-ray crystal structure of the copper porphyrin complex shows that the plane of the verdazyl moiety is oriented such that it is nearly perpendicular to the plane of the porphyrin ring so that weak magnetic interactions between the metal and radical are expected. Consistent with this expectation, magnetic susceptibility and continuous-wave electron paramagnetic resonance (EPR) measurements of the copper (d(9)) and vanadyl (d(1)) versions of the porphyrin show that the metal and radical are weakly antiferromagnetically coupled. Thus, the ground state is a singlet, but the triplet state is thermally accessible above approximately 5 K. Spin-polarized transient EPR measurements of the free-base analogue show that its lowest excited state is a quartet, indicating that the verdazyl radical couples ferromagnetically to the triplet excited state of the porphyrin. Low-temperature transient EPR measurements on the vanadyl porphyrin reveal that the lowest excited quintet state is populated. This implies that the antiferromagnetic coupling between the metal and radical observed in the ground state is switched to a ferromagnetic arrangement in the excited state by the presence of the unpaired electrons in the pi and pi* orbitals of the porphyrin.

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Section: Introductionmentioning

confidence: 99%

Spin−Spin Interactions in Porphyrin-Based Monoverdazyl Radical Hybrid Spin Systems

Poddutoori

Pilkington²,

Alberola

et al. 2010

Inorg. Chem.

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“…[31][32][33][34][35] Our efforts have focused on preparing new porphyrins as building blocks for coordination polymers and complexes with interesting magnetic or magneto-optic properties. 31,32,[36][37][38] Herein, we describe the syntheses and electron paramagnetic resonance (EPR) spectral characterizations of porphyrins 1-3 (Scheme 1), which have stable nitroxide and stable semiquinone (SQ) complexes covalently attached to trans-meso positions of the porphyrin ring. One of these compounds, 3, has been structurally characterized.…”

Section: Introductionmentioning

confidence: 99%

Electron Spin−Spin Exchange Coupling Mediated by the Porphyrin π System

et al. 2006

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The syntheses and electron paramagnetic resonance (EPR) spectral characterizations of porphyrins (1-3) substituted with two radical groups bound to trans-meso positions are described. One of these compounds, 3, has been studied by variable-temperature magnetic susceptibility and has been structurally characterized. Biradical porphyrin 3 is monoclinic, space group P2(1)/n, with a = 12.239(2) A, b = 17.819(3) A, c = 34.445(7) A, alpha = 90 degrees , beta = 97.466(3) degrees , gamma = 90 degrees , and Z = 2. The bis(nitroxide) porphyrins 1 and 2 exhibit fluid solution EPR spectra consistent with |J| >> |a|. No evidence was observed for conformational modulation of J by rotation about single bonds as shown by the lack of change of the EPR spectra as a function of temperature. The bis(semiquinone) porphyrin 3 exhibits frozen-solution EPR spectra with zero-field splitting and a Deltam(s) = 2 transition characteristic of a triplet state. The intensity of the Deltam(s) = 2 transition of 3 was measured as a function of temperature, and the data fit according to a singlet-triplet model to yield J(3,solution) = -75 cm(-1) (H = - 2Jŝ1.ŝ2). Polycrystalline samples of porphryin 3 were examined by variable-temperature magnetometry. The paramagnetic susceptibility data were fit using a modified Bleaney-Bowers equation to give J(3,solid) = -29 cm(-1) (H = - 2Jŝ(1).ŝ(2)). The antiferromagnetic J values are consistent with the pi topology of the porphyrin ring.

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“…Miller et al 17 are studying a series of Mn(II) porphyrin-TCNE complexes that order magnetically at surprising high temperatures. 18 We are preparing radical-substituted metalloporphyrins for the construction of coordination polymers with interesting magnetic properties 19,20 (hereafter, 'porphyrin' refers to metalloporphyrin). Porphyrins are attractive from a synthetic point of view for four reasons: (1) there are 12 positions at which substituents can be attached, i.e.…”

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confidence: 99%

Semiempirical computational assessment of porphyrins as building blocks for molecule‐based magnets: spin–spin coupling in radical‐substituted metalloporphyrins

Shultz¹,

Sandberg²

1999

J. Phys. Org. Chem.

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Semiempirical PM3-RHF-CI calculations were used to probe structure-exchange coupling relationships in radical-substituted Zn(II) porphyrins. The results support a number of important design elements for creating high-spin molecules from metalloporphyrins and the corresponding pi-cation radicals. The calculations showed that inactive porphyrin-active phenoxy union mode provides stronger exchange coupling than active porphyrin-inactive phenoxy union mode. Connecting radicals to the metalloporphyrin core via an ethynyl linkage eliminates severe torsion, permitting a coplanar alignment of the two pi systems. Metalloporphyrins could be excellent redox-activated exchange couplers: porphyrin radical cation exchange couples attached radicals more effectively than the neutral porphyrin. Finally, the magnitude of exchange coupling between a metalloporphyrin pi-cation radical depends on the nature of the attached radical. The results of the calculations were explained using a coupler spin analysis. Copyright

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Preparation of meso-tetra(4-galvinolphenyl)porphyrin—A building block for molecular magnetic materials

Cited by 8 publications

References 22 publications

Spin−Spin Interactions in Porphyrin-Based Monoverdazyl Radical Hybrid Spin Systems

Spin−Spin Interactions in Porphyrin-Based Monoverdazyl Radical Hybrid Spin Systems

Electron Spin−Spin Exchange Coupling Mediated by the Porphyrin π System

Semiempirical computational assessment of porphyrins as building blocks for molecule‐based magnets: spin–spin coupling in radical‐substituted metalloporphyrins

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