Conformations of Chlorophylls a and a′ and their Magnesium-Free Derivatives as Revealed by Circular Dichroism and Proton Magnetic Resonance

1981 ◽  
Vol 36 (8) ◽  
pp. 1000-1009 ◽  
Author(s):  
Paavo H. Hynninen ◽  
Gunnel Sievers
Keyword(s):  
Circular Dichroism ◽  
Magnetic Resonance ◽  
Electronic Absorption ◽  
Proton Magnetic Resonance ◽  
Nmr Spectra ◽  
Cd Spectra ◽  
Steric Strain ◽  
Methyl Group ◽  
H Nmr ◽  
Circular Dichroïsm

Abstract The electronic absorption (UV/VIS), circular dichroism (CD) and proton magnetic resonance (1H NMR) spectra have been recorded for C-10 epimeric chlorophylls a and a′, pheophytins a and a′ as well as pheophorbides a and a′. Although the epimers in each pair showed virtually identical UV/VIS spectra, their CD spectra were profoundly different and exhibited opposite signs at most wavelengths in the UV region. The differences were interpreted as arising, in part, from different C-10 configurations, and, in part, from conformational alterations induced by the steric strain in the crowded periphery of the macrocycle. The conformational alterations were also clearly indicated by the 1H NMR Δδ-values observed for the α,β and δ methine protons, the C-10 protons and most methyl group protons of the epimers in each pair. This was considered to imply changes in the geometry of the whole macrocycle. The Δδ-values were larger for the Mg-free epimers than for the chlorophyll epimers, which shows that the central Mg-atom makes the macrocycle more rigid. Correlations between the signs of the CD bands and configurations are discussed.

Aliphatic diazo compounds. XII. The synthesis of 5-endo-hetero-atom-substituted 3-diazo-2-norbornanones and the proton magnetic resonance spectra of these diazo ketones and their precursors

1979 ◽  
Vol 57 (13) ◽  
pp. 1656-1667 ◽  
Author(s):  
Peter Yates ◽  
Gordon F. Hambly
Keyword(s):  
Magnetic Resonance ◽  
Long Range ◽  
Proton Magnetic Resonance ◽  
Nmr Spectra ◽  
Steric Effect ◽  
Diazo Compounds ◽  
Lower Field ◽  
Methyl Group ◽  
H Nmr ◽  
Basic Alumina

Treatment of 6-endo-acetoxy-5,5-dimethyl-2,3-norbornanedione (6) with tosylhydrazine gives the 2-tosylhydrazone (7), which is converted to 5-endo-acetoxy-3-diazo-6,6-dimethyl-2-norbornanone (1) by basic alumina; the exclusive formation of the 2-tosylhydrazone is ascribed to the smaller steric effect of the endo C-6 acetoxyl relative to the endo C-5 methyl group. The 6-endo-methoxy analogue of 6, 17, and the related 6-endo-chloro- and 6-endo-bromo-1,5,5-trimethyl-2,3-norbornanediones (23 and 26) are similarly converted to the corresponding α-diazo ketones 2–4. The 1H nmr spectra of the diazo ketones 1–4 have their C-1 bridgehead proton signals shifted to higher field relative to the corresponding bridgehead proton signals of the related α-diketones, whereas the C-4 bridgehead proton signals of 1 and 2 are shifted to lower field in relation to the corresponding α-diketone signals. The 1H nmr spectra of the α-diketones show an unusual long range coupling (4J ≥ 1 Hz) between the C-4 bridgehead protons and the exo C-6 protons that is significantly smaller or absent in the spectra of the related diazo ketones and monoketones. In all of these types of compound an endo-methoxyl or -acetoxyl group at C-5(6) shifts the exo and endo C-6(5) methyl signals to lower and higher field, respectively, whereas an endo-halo substituent at C-5(6) shifts both the exo and endo C-6(5) methyl signals to lower field.

Contribution to the structure of aluminium caprolactamate based on the study of infrared and proton magnetic resonance spectra

1979 ◽  
Vol 44 (9) ◽  
pp. 2772-2779 ◽  
Author(s):  
Otomar Kříž ◽  
Bohuslav Čásenský
Keyword(s):  
Magnetic Resonance ◽  
Low Temperature ◽  
Oxygen Atom ◽  
Proton Magnetic Resonance ◽  
Nmr Spectra ◽  
Membered Ring ◽  
Aluminium Atom ◽  
Molecular Weights ◽  
H Nmr

Aluminium caprolactamate (I) was prepared by the reaction of ε-caprolactam with isopropyliminoalane (II) in benzene. IR and 1H-NMR spectra of I in various solvents are described as well as low-temperature 1H-NMR spectra in hexane and dichlormethane. On the basis of these results together with the determination of molecular weights, structural arrangement was proposed for the dimer of I containing an eight-membered ring formed by two -O-C-N-bridges between aluminium atoms and two caprolactam ligands on each aluminium atom bonded through oxygen atom of carbonyl.

Synthesis and nuclear magnetic resonance spectra of platinum compounds with thiourea derivatives

1985 ◽  
Vol 63 (9) ◽  
pp. 2425-2429 ◽  
Author(s):  
F. D. Rochon ◽  
J. Bariyanga ◽  
P. C. Kong
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Sulfur Atom ◽  
Nmr Spectra ◽  
Intramolecular Interaction ◽  
Platinum Compounds ◽  
Thiourea Derivatives ◽  
Methyl Group ◽  
H Nmr ◽  
Nuclear Magnetic Resonance Spectra

Compounds of the type trans-[PtL2T2]Cl2 where L = NH3, methylamine, dimethylamine, pyridine, and 2-aminopyrimidine and T = N-methylthiourea and N,N′-dimethylthiourea and where L = NH3 and T = N,N,N′,N′-tetramethylthiourea have been synthesized. The 1H nmr spectra have shown that the thiourea derivatives are bonded to platinum by the sulfur atom. The methyl protons of N-methylthiourea and one methyl group protons of N,N′-dimethylthiourea in the complexes, where L is aromatic, showed resonance at higher field after coordination to the metal. This was explained by an intramolecular interaction between the methyl group and the aromatic ring. The nmr spectra of the [PtT4]Cl2 compounds were also measured.

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