Proton nuclear magnetic resonance contact shifts of octahedral iron(II), cobalt(II), and nickel(II) imidazole complexes

Wicholas, Mark; Mustacich, Robert V.; Johnson, B.; Smedley, Terry A.; May, Joan C.

doi:10.1021/ja00841a019

Cited by 13 publications

(3 citation statements)

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“…The shifts for the various imidazole protons as listed in Table are downfield for the NH, 2-H, 4-H, and 5-H protons. This pattern is generally consistent with major contribution from σ-spin delocalization − as described previously for [Ni II (SDPDTP)(R-Im)]Cl . and other nickel(II)-imidazole complexes. − …”

Section: Resultssupporting

confidence: 89%

5,20-Diphenyl-10,15-bis(p-tolyl)-21-selenaporphyrin and Its Nickel(II) Complexes¹

et al. 1996

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The synthesis of a new monoheteroporphyrin, 5,20-diphenyl-10,15-bis(p-tolyl)-21-selenaporphyrin (SeDPDTPH), is reported. The 21-selenaporphyrin has been characterized by 1H NMR, 13C NMR, mass spectrometry, and UV−visible spectra and an X-ray structural analysis. The free base selenaporphyrin SeDPDTPH crystallizes in the monoclinic space group P21/n with a =19.848(3) Å, b = 8.8410(14) Å, c = 20.503(4) Å, β = 103.375(12)° at 125 K with Z = 4. Refinement of all 4577 unique reflections and 453 parameters yielded R 1 = 0.096 (based on F 2). The presence of selenium atom elongates the macrocycle along the N(1)−N(3) axis when compared to a regular porphyrin. The π delocalization pattern is altered in the selenophene moiety in relation to the free selenophene. SeDPDTPH undergoes a two-step proton addition in solution. Mono- and dication formation results in distortion of the planar 21-selenaporphyrin structure. The monocation structure is solvent dependent as shown by the 1H NMR titration experiments. Insertion of Ni(II) into 21-selenaporphyrin yields NiII(SeDPDTP)Cl (S = 1, μeff = 3.3 μB). The electronic spectrum of this complex is porphyrin-like with a strong Soret band at 433 nm. The 1H NMR spectra of the high-spin nickel(II) complexes of 21-selenaporphyrin have been recorded and assigned by means of the selective deuteration, line width considerations, and a 2D COSY experiment. The characteristic pattern of pyrrole (downfield) and selenophene (upfield) resonances has been established. Direct σ-π spin density transfer has been proposed to explain the upfield shift of the selenophene protons. Imidazole replaces the chloride ligand to form five- and six-coordinate complexes. The spectroscopic and chemical properties of NiII(SeDPDTP)Cl resemble those of nickel(II) complexes with 21-thiaporphyrin. To account for these similarities, we suggest that the selenophene moiety is bent out of the porphyrin plane in NiII(SeDPDTP)Cl. Such a geometry allows metal ion to interact with selenium of selenophene in a side-on fashion.

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Section: Resultssupporting

confidence: 89%

5,20-Diphenyl-10,15-bis(p-tolyl)-21-selenaporphyrin and Its Nickel(II) Complexes¹

et al. 1996

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“…This pattern is generally consistent with major contribution from -spin delocalization. 43 The sign change observed for 2-CH3 and 2-H resonances suggests some contribution from a delocalization mechanism. 44 In imidazole coordination to iron, including iron porphyrins, the upfield (downfield) shift of 2-H and downfield (upfield) shift of 2-CH3 are considered as evidence for the -delocalization mechanism.…”

Section: Discussionmentioning

confidence: 97%

Nuclear magnetic resonance study of the molecular and electronic structure of nickel(II) tetraphenyl-21-thiaporphyrins

Lisowski¹,

Latos‐Grażyński²,

Szterenberg³

1992

Inorg. Chem.

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“…The positive signs of A of H and C can be explained by σ spin delocalization mechanism. [22] An octahedral Ni 2+ (S = 1) complex has a (t 2g ) 6 (e g ) 2 configuration and e g orbitals are the SOMO of this complex. One of the e g orbitals is composed of d x 2 −y 2 orbital of the nickel ion and σ orbitals of the ligand The other possible mechanism that induces spin density distribution is spin polarization mechanism, originally introduced by McConnell and Chesnut to explain negative spin densities in aromatic radicals.…”

Section: Spin Density Distribution Of the Imidazole Ligand And Possibmentioning

confidence: 99%

Solid-state high-resolution NMR studies on spin density distribution of a ferromagnetic coordination polymer: Ni(NCS)2(Him)2

Maruta

Takeda

2005

Polyhedron

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We determined hyperfine coupling constants (hfcc) of the imidazole ligand in a ferromagnetic coordination polymer, di-μ-thiocyanatobis(imidazole)nickel(II), using 1H-, 2H-, and 13C-MAS-NMR. Partially or fully deuterated sample was prepared to measure temperature dependence of the isotropic shifts of NMR signals. We obtained hfcc of AC = +0.57, +0.69, +1.88 MHz for 2-, 4-, 5-carbon and AH = +0.66, +0.37, +0.48, +0.53 MHz for 1-, 2-, 4-, 5-proton in the imidazole ligand, respectively, which indicates that unpaired electron in dx2*y2 orbital of Ni(II) ion delocalizes over the imidazole ligand. On the basis of the NMR and DFT results, we proposed an interchain superexchange pathway through N-H...S hydrogen bond.http://www.sciencedirect.com/science/journal/0277538

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Proton nuclear magnetic resonance contact shifts of octahedral iron(II), cobalt(II), and nickel(II) imidazole complexes

Cited by 13 publications

References 4 publications

5,20-Diphenyl-10,15-bis(p-tolyl)-21-selenaporphyrin and Its Nickel(II) Complexes¹

5,20-Diphenyl-10,15-bis(p-tolyl)-21-selenaporphyrin and Its Nickel(II) Complexes¹

Nuclear magnetic resonance study of the molecular and electronic structure of nickel(II) tetraphenyl-21-thiaporphyrins

Solid-state high-resolution NMR studies on spin density distribution of a ferromagnetic coordination polymer: Ni(NCS)2(Him)2

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Proton nuclear magnetic resonance contact shifts of octahedral iron(II), cobalt(II), and nickel(II) imidazole complexes

Cited by 13 publications

References 4 publications

5,20-Diphenyl-10,15-bis(p-tolyl)-21-selenaporphyrin and Its Nickel(II) Complexes1

5,20-Diphenyl-10,15-bis(p-tolyl)-21-selenaporphyrin and Its Nickel(II) Complexes1

Nuclear magnetic resonance study of the molecular and electronic structure of nickel(II) tetraphenyl-21-thiaporphyrins

Solid-state high-resolution NMR studies on spin density distribution of a ferromagnetic coordination polymer: Ni(NCS)2(Him)2

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Resources

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5,20-Diphenyl-10,15-bis(p-tolyl)-21-selenaporphyrin and Its Nickel(II) Complexes¹

5,20-Diphenyl-10,15-bis(p-tolyl)-21-selenaporphyrin and Its Nickel(II) Complexes¹