Pyrrole Pigments Research Articles

Transition-metal Complexes of Pyrrole Pigments. XIII. Reduction and Coordination Behaviors of the Cobalt(II) Complexes of 1,19-Disubstituted Tetradehydrocorrins as Demonstrated by the Presence of Various Bases

Abstract The interaction of various bases with the cobalt(II) complexes of 1,19-disubstituted tetradehydrocorrins (Co(II)–TDHC) was investigated. The parent cobalt(II) complexes were shown to undergo ready reduction at the nuclear cobalt(II) with the unsolvated hydroxide ion as well as with bulky triethylamine. A relatively large positive reduction potential of Co(II)–TDHC is responsible for these novel electron transfer reactions. Less hindered amines (B), on the other hand, failed to show such electron transfer reactions with the cobalt(II) complexes and Co(II)–TDHC became the pentacoordinated complex by taking up an amine base in the axial position: Co(II)–TDHC+B\ightleftharpoonsB–Co(II)–TDHC. For the interaction of 4-substituted pyridines with the cobalt(II) complex, the general behavior of the equilibrium constants was interpreted in terms of the amine basicity and the Hammett equation by referring to the corresponding behavior of the porphyrin complexes. The weaker coordination tendency of some aliphatic amines and hindered pyridines toward Co(II)–TDHC was attributed to their electronic and steric effects in the coordination process. The intrinsic correlation between electronic and stereochemical characteristics pertaining to the tetradehydrocorrin skeleton and the nature of nuclear cobalt(II) was discussed on the basis of these observations.

Transition-metal Complexes of Pyrrole Pigments. XII. Optical and Magnetic Resonance Spectra of the Cobalt(II) and Nickel(II) Complexes of 1,19-Disubstituted Tetradehydrocorrins

Abstract The cobalt(II) and nickel(II) complexes of 1,19-dimethyl- and 1,19-diethoxycarbonyltetradehydrocorrins were prepared by the template reaction as functioned by metal ions from the corresponding 1,19-disubstituted 1,19-dideoxybiladiene-ac’s. The absorption bands appearing in the energy region greater than 15000 cm−1 were attributed to the π→π* transitions within a ligand molecule. The ligand-field bands were observed in the lower energy region (<15000 cm−1) for the cobalt(II) complexes in which cobalt(II) assumes the C2v coordination symmetry: 2A1←2A1, 2A2←2A1,2B2←2A1, and 2B1←2A1 in an increasing order of energy. The vibrational spectra provided evidences for the formation of the tetradehydrocorrin complexes with perchlorate ion as the counter ion. The angular methyl groups placed at the 1- and 19-positions of tetradehydrocorrins showed the abnormally large up-field shift (2.0 ppm) of their proton signal relative to the parent biladiene-ac’s due to the magnetic anisotropy of the adjacent pyrrole rings A and D. For a 1,19-diethyoxycarbonyltetradehydrocorrin complex, the 1,19-substituents were also placed in the shielding zone of the neighboring pyrrole rings. In the case of the cyclized 2,8,12,18-tetra(2-ethoxycarbonylethyl) derivative, the ethyl ester groups of the 2,18-substituents were presumably placed in a conformational space different from that occupied by those of the 8,12-substituents according to the proton NMR behaviors. The parent biladiene-ac which carries ethoxycarbonyl groups at the 1,19-positions caused a up-field shift of its methine (at bridge positions) proton signal upon cyclization due to the loss of electronic conjugation of carbonyl groups with pyrrole rings, in consistent with the vibrational data. The ESR spectra were measured in chloroform-benzene (2 : 1) at 77 K in the presence and absence of pyridine. The cobalt(II) complexes were identified as of low-spin square-planar type with the unpaired electron in the cobalt dz2 orbital. The coordination capability of 2-ethoxycarbonylethyl groups, which are directly bound to the pyrrole rings in the cyclized metal complex system, was also suggested.

Transition-metal complexes of pyrrole pigments. Part VII. Cobalt(II) and zinc(II) chelates of some tripyrrene-b and bilene-b ligands

The cobalt(II) and zinc(II) chelates of 1′,6-diethoxycarbonyl-1,2,3,4,5,6′-hexamethyitripyrrene-b and 1,19-di-ethoxycarbonyl-2,3,7,8,12,13,17,18-octamethyl-1,19-dideoxybilene-b in a ligand to metal ratio of 2:1 were prepared and investigated by electronic, i.r., and n.m.r. spectroscopy. A co-ordination geometry close to a regular tetrahedron (D2 symmetry) around the metal atoms was assigned to these chelates.

Pyrrole pigments in normal and congenitally anaemic mice (+/+, W/Wv, ha/ha, nb/nb, mk/mk, f/f and sla/Y)

1. Values for faecal urobilinogen (UBG), serum bilirubin, and free erythrocyte protoporphyrin (FEP) are reported for normal and anaemic mice with six different hereditary anaemias. 2. Greatly increased faecal UBG and elevated serum bilirubin were found in mice with severe haemolytic anaemia (nb/nbandha/ha). 3. Mice with microcytosis (mk/mk) and sex-linked anaemia (sla/Y), both showed increased FEP and only moderate increase of faecal UBG. 4. Values for W/W v mice fell within the normal ranges. 5. FEP levels in normal 15-day foetal red cells were extremely high. Levels for 15-day flexed anaemic foetuses (f/f) were lower, but markedly aboved adult level.

Transition metal complexes of pyrrole pigments. IV. Electronic and vibrational spectra of cobalt(II), nickel(II), and copper(II) complexes of some substituted dipyrromethenes

Transition metal complexes of pyrrole pigments. IV. Electronic and vibrational spectra of cobalt(II), nickel(II), and copper(II) complexes of some substituted dipyrromethenes

Interrelationship of pyrrole and globin metabolism in beta-thalassaemia.

Detailed metabolic studies in a case of β‐thalassaemia intermedia following 14C‐2‐glycine administration demonstrate some of the interrelationships of pyrrole pigments and haemoglobins, and some secondary effects of a β‐thalassaemia mutation.Marked increase in the early‐labelled fraction of faecal bile pigment was confirmed; labelling rose to a maximum at 5 days, in advance of the haem peak, and was approximately three times greater than maximum haem labelling.Urinary coproporphyrins were increased in quantity, thus allowing complete serial determinations of radioactivity, which was at its maximum within 24 hours. The urine also contained a brown pigment, probably a dipyrrole, which had a labelling pattern resembling that of the urinary coproporphyrins, with maximum activity in the first sample. It is suggested that the ‘dipyrrole’may arise by early destruction of redundant haem associated with α‐chains.At all times, haemoglobin F was more highly labelled than haemoglobin A in both the haem and the globin moieties. Mean cell survival estimated graphically from the various curves was approximately 32 days. Haem/globin ratios were similar to those reported previously in normal subjects and in thalassaemia.

Transition-metal complexes of pyrrole pigments. I. Electronic and vibrational spectra of cobalt(II), nickel(II) and copper(II) complexes of some dipyrromethenes

The cobalt, nickel(II), and copper(II) complexes of 3,4,5-trimethyl-, 3,3′,5,5′-tetramethyl- and 3,3′,4,4′,5,5′-hexamethyldipyrromethene have been synthesized in this work and investigated by visible, near-infrared, infrared and far-infrared spectroscopy. The ligand-field bands for these metal complexes have provided valuable information on their geometry around the central metal atoms. Namely, the copper complexes assume the tetragonally distorted tetrahedral configuration while the nickel and cobalt complexes are approximately regular tetrahedral. Moreover, the removal of the 5′-methyl group of a dipyrromethene moiety in the copper complexes results in a significant structural alteration to the further flattened tetrahedron. In the far-infrared spectra, the prominent absorption peaks which can be associated with the metal-ligand stretching modes have been observed in the 400–350 cm −1 range. In addition, strong bands appearing at ∼1600 cm −1 have been assigned to the pyrroles-skeletal stretching mode. After examination of these infrared spectral data, the strength of the coordinate bonds has been noticed to increase in the order: Cu<Ni≳Co. The lowered strength of coordinate bonds for the copper complexes and the nature of coordinate bonds involved in the metal complexes of this work were discussed in connection with their stereochemistry.

Comprehensive Biochemistry. Volume 9: Pyrrole Pigments, Isoprenoid Compounds, Phenolic Plant Constituents. Marcel Florkin , Elmer H. Stotz

<i>Comprehensive Biochemistry. Volume 9: Pyrrole Pigments, Isoprenoid Compounds, Phenolic Plant Constituents</i>. Marcel Florkin , Elmer H. Stotz

Comprehensive Biochemistry. Section II: Chemistry of Biological Compounds. Vol 9: Pyrrole Pigments, Isoprenoid Compounds and Phenolic Plant Constituents.

Comprehensive Biochemistry. Section II: Chemistry of Biological Compounds. Vol 9: Pyrrole Pigments, Isoprenoid Compounds and Phenolic Plant Constituents.

Organic Chemistry for Biochemists

Comprehensive Biochemistry Vol. 9: Pyrrole Pigments, Isoprenoid Compounds and Phenolic Plant Constituents. Pp. xiv + 265. 70s. Vol. 10: Sterols, Bile Acids and Steroids. Pp. xii + 209. 55s. Edited by Marcel Florkin, Elmer H. Stotz, (Amsterdam, London and New York: Elsevier Publishing Company, 1963.)

Liversidge Research Lecture. Chemical structure and biological function of the pyrrole pigments and enzymes.

Liversidge Research Lecture. Chemical structure and biological function of the pyrrole pigments and enzymes.

Relative Stabilities of Chelate Compounds of Pyrrole Pigments1

Relative Stabilities of Chelate Compounds of Pyrrole Pigments¹

Pyrrole pigments.

The Hippo pathway was initially discovered in Drosophila melanogaster as a key regulator of tissue growth. It is an evolutionarily conserved signaling cascade regulating numerous biological processes, including cell growth and fate decision, organ size ...Read More

Biogenetic origin of the pyrrole pigments

Biogenetic origin of the pyrrole pigments