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  • 1
    Electronic Resource
    Electronic Resource
    The NMR spectra of the porphyrins. 17For Part 16, see Ref. 1. - Metalloporphyrins as diamagnetic shift reagents, structural and specificity studies (1982)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 18 (1982), S. 45-52 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nature of the metalloporphyrin-ligand complexes produced by zinc, magnesium and cobalt porphyrins with basic ligands has been investigated using the diamagnetic ring current shifts of the porphyrin on the ligand protons. The metal to nitrogen bond lengths in some metallo-meso-tetraphenylporphyrin (pyridine) complexes have been determined and compared with the data of the crystalline complexes. The geometry of the Zn meso-tetraphenylporphyrin complexes with 2-picoline, quinoline and isoquinoline has been investigated. Steric interactions between the ligand and the porphyrin in 2-picoline and quinoline produce a dramatic increase in the Zn—N bond length when compared to the unstrained analogues pyridine and isoquinoline. This large increase is associated with comparatively minor angle distortions in the complex. The specificity of the Zn meso-tetraphenylporphyrin complexation shifts has been determined for a range of benzyl and butyl compounds. The complexation shift is linearly related to the basicity of the ligand for a wide range of basicities.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270180111
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  • 2
    Electronic Resource
    Electronic Resource
    A novel use of cobalt(III) meso-tetraphenylporphyrin as a chiral shift reagent (1984)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 22 (1984), S. 57-60 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The NMR spectra of the diastereomeric complexes formed by the coordination of nitrogenous enantiomeric bases with cobalt(III) meso-tetraphenylporphyrin (CoTPP) allow the immediate differentiation of these complexes. The spectra are interpreted on the basis of symmetry (RR and SS) and pseudo-chirality (RS and SR) considerations. The effects are observed in both the proton and carbon spectra and the complexes are stable in both CDCl3 and DMSO-d4 solution. This technique, in principle, allows the ready determination of the optical purity of multifunctional ligands.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270220113
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  • 3
    Electronic Resource
    Electronic Resource
    The NMR spectra of the porphyrins: 23For Part 22, see Ref. 1. - Metalloporphyrins as diamagnetic shift reagents, chemical applications (1983)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 21 (1983), S. 637-642 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some applications illustrating the use of zinc (II) meso-tetraphenylporphyrin (ZnTPP) as a diamagnetic shift reagent are described. The complexation shifts (ΔP) in a series of substituted pyridines are shown to be determined by both the basicity of the coordinating nitrogen atom and steric effects of ortho-substituents. The selectivity of ZnTPP (N»O) in the simplification of the spectra of multifunctional ligands is demonstrated. Addition of the reagent neither affects the rotamer populations of the Inderal side-chain nor produces any distortion of the 2-benzylmorpholine ring. In addition, the substrate-reagent solution may be shaken with D2O to identify exchangeable protons. The application of ZnTPP in structural problems involving substituted imidazo[2,1-b]thiazoles and 2-benzyl-1,3-dioxopyrrolo[3,4-c]pyridines allows unambiguous identification of the possible structural isomers. To overcome the solvent limitations of ZnTPP, the more soluble Co(III)TPPBr can be used successfully as a shift reagent in DMSO-d6, CD3OD and acetone-d6 solutions.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/omr.1270211009
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  • 4
    Electronic Resource
    Electronic Resource
    The NMR spectra of the porphyrins 16For Part 15 see Ref. 1. - zinc(II) meso-tetraphenylporphyrin (Zn TPP) as a diamagnetic shift reagent. A quantitative ring current model (1980)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 14 (1980), S. 418-425 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The facile preparation of zinc(II) meso-tetraphenylporphyrin (Zn TPP) and derivatives from substituted benzaldehydes and pyrrole, combined with the calculation of ring current shifts in these molecules, provides a useful series of selective diamagnetic shift reagents. The porphyrin-ligand equilibrium is examined for some nitrogenous bases and the complexation shifts (δP values) are obtained in precisely the same manner as LIS. The parameterization of the double-dipole model of the porphyrin ring current is given, with the inclusion of the phenyl ring currents and free rotation about the substrate-Zn bond. Precise agreement with the porphyrin proton chemical shifts and the complexation shifts of the geometrically rigid substrates of pyridine, 4-picoline and quinuclidine is obtained. In contrast, the 13C complexation shifts in these molecules are subject to additional effects other than the ring current shift.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270140519
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  • 5
    Electronic Resource
    Electronic Resource
    The NMR spectra of porphyrins 20For Part 19 see Ref. 1. - proton and 13C characterization of porphyrin atropisomers (1982)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 19 (1982), S. 204-210 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation, isolation and characterization by proton and 13C NMR of the four possible atropisomers of meso-tetra(2-methoxy-1-naphthyl)porphyrin is described. Chemical shift differences due to atropisomerization effects are observed in the porphyrin and naphthyl rings. Comparison of the naphthyl chemical shifts with those of the model compound 1-isopropenyl-2-methoxynaphthalene allows the shifts due to the porphyrin ring current to be isolated. The observed Δδ values of the naphthyl protons agree well with those calculated from the previously described porphyrin ring current model, and allow both the angle of tilt of the naphthyl ring and the dihedral angle of the 2-methoxy substituent to be estimated. In contrast, the Δδ values for the naphthyl carbons bear no relationship to the calculated ring current shifts. Calculations of the total ring current contribution (porphyrin plus naphthyl rings) at the different naphthyl rings of the unsymmetric type III isomer show that at least part of the observed atropisomerism effects are due to the long-range current shifts of the naphthyl rings. The results also provide a clear demonstration of the identity of the porphyrin ring current in the free base and porphyrin dication.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270190409
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  • 6
    Electronic Resource
    Electronic Resource
    The NMR spectra of the porphyrins: 24For Part 23, see Ref. 1. - The NMR spectra of some tetraarylchlorins (1983)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 21 (1983), S. 745-756 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and complete assignment of the 1H NMR spectra of 5-(o-pivaloylaminophenyl)-10,15,20-triphenylporphyrin (PIVTPP) and its two chiral dihydro adducts 3,4-dihydro-(PIVPTPC-I)- and 7,8-dihydr- (PIVPTPC-II)-porphyrins are reported. The use of the zinc complexes of the chlorins as chiral shift reagents with optically active bases is discussed. Comparison of the observed shift differences between the chlorins and the parent porphyrin with those calculated by a ring current model shows that a decrease in the ring current occurs on chlorin formation, and also specific effects occur at the reduced pyrrole ring, presumably reflecting different steric constraints.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/omr.1270211207
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  • 7
    Electronic Resource
    Electronic Resource
    15N NMR studies of guanidines. I - hydrogen bonding and electronic effects in conformationally flexible guanidines (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 383-388 
    Details
    ISSN: 0749-1581
    Keywords: NMR ; 15N NMR ; guanidines ; heterocycles ; hydrogen bonding ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogen bonding and electron distribution in some heterocyclic guanidines were studied by 15N NMR spectroscopy, using other substituted guanidines as points of reference. Solvent effects were used to distinguish the 15N NMR signals for their two sp2 nitrogen atoms, since ring nitrogen forms an intramolecular hydrogen bond and so is much less sensitive to solvent than is the guanidine unit. The effect of substituent is discussed in terms of competition between through-resonance and the more localized resonance of the π-inductive effect. These are favoured, respectively, by oxygen (nitro, acyl) and nitrogen (cyano) acceptor groups, whereas heterocycles, also nitrogen acceptors, occupy an intermediate position. Among the latter class, there are indications that the balance between these forms of resonance may be influenced by competitive conjugation with ring π-donor heteroatoms.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260330510
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  • 8
    Electronic Resource
    Electronic Resource
    15N NMR studies of guanidines. IIFor Part I, see p. 383. - the fused-in guanidine unit of some oxoheterocycles: A combined 15N NMR, 13C NMR and IR study (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 389-394 
    Details
    ISSN: 0749-1581
    Keywords: NMR ; 15N NMR ; 13C NMR ; IR ; guanidines ; oxoheterocycles ; isomerism ; tautomerism ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 15N NMR spectroscopy was used to extend previous studies, by 13C NMR and IR spectroscopy, of fused oxoheterocycles which contain the guanidine unit. These compounds fall into three clearly definable structural types, through-conjugated, ring-conjugated or imide-like, any or all of which may result from the cyclization reactions used for their synthesis. It is shown that 15N NMR and IR criteria are of equal value in distinguishing these, whereas 13C NMR is in general unhelpful. A qualitative correlation exists between v(C=N) for the guanidine unit, and the summed 15N NMR chemical shifts for the two π-donor nitrogen atoms. The present observations should help to establish spectroscopic criteria for structural elucidation.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260330511
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