1925-61-7Relevant academic research and scientific papers
Pyrrophens: Pyrrole-Based Hexadentate Ligands Tailor-Made for Uranyl (UO22+) Coordination and Molecular Recognition
Forbes, Madeleine G.,Gorden, Anne E. V.,Gorden, John D.,Mayhugh, Jacob T.,Niklas, Julie E.
, (2020)
Derivatives of a novel pyrrole-containing Schiff base ligand system (called "pyrrophen") are presented which feature substituted phenylene linkers (R1 = R2 = H (H2L1); R1 = R2 = CH3 (H2L2)) and a binding pocket modeled after macrocyclic species. These lig
Steric control of mesocate and helicate formation: Bulky pyrrol-2-yl Schiff base complexes of Zn2+
Gorden, A. E. V.,Gorden, J. D.,Hiti, E. A.,Mayhugh, J. T.,Niklas, J. E.,Wilkinson, G. R.
, (2022/01/14)
Regioisomerism about a phenyl spacer alters the number of nuclei which participate in self-assembly with pyrrole/schiff base ditopic ligands. The bulky benzyl ester substituents favor formation of di- and tetranuclear (but not trinuclear) complexes. The r
Size-Selective Hydroformylation by a Rhodium Catalyst Confined in a Supramolecular Cage
Nurttila, Sandra S.,Brenner, Wolfgang,Mosquera, Jesús,van Vliet, Kaj M.,Nitschke, Jonathan R.,Reek, Joost N. H.
, p. 609 - 620 (2019/01/04)
Size-selective hydroformylation of terminal alkenes was attained upon embedding a rhodium bisphosphine complex in a supramolecular metal–organic cage that was formed by subcomponent self-assembly. The catalyst was bound in the cage by a ligand-template approach, in which pyridyl–zinc(II) porphyrin interactions led to high association constants (>105 m?1) for the binding of the ligands and the corresponding rhodium complex. DFT calculations confirm that the second coordination sphere forces the encapsulated active species to adopt the ee coordination geometry (i.e., both phosphine ligands in equatorial positions), in line with in situ high-pressure IR studies of the host–guest complex. The window aperture of the cage decreases slightly upon binding the catalyst. As a result, the diffusion of larger substrates into the cage is slower compared to that of smaller substrates. Consequently, the encapsulated rhodium catalyst displays substrate selectivity, converting smaller substrates faster to the corresponding aldehydes. This selectivity bears a resemblance to an effect observed in nature, where enzymes are able to discriminate between substrates based on shape and size by embedding the active site deep inside the hydrophobic pocket of a bulky protein structure.
Synthesis and properties of mesobilirubins XIIγ and XIIIγ and their mesobiliverdins
Sabido, Portia Mahal G.,Lightner, David A.
, p. 775 - 789 (2014/05/20)
The title pigments, with propionic acid groups displaced to the lactam end rings, were synthesized for the first time by the "1 + 2 + 1" approach, coupling two equivalents of a monopyrrole to a dipyrrylmethane (to give XIIγ), or the "2 + 2" approach, self-coupling two equivalents of a dipyrrinone (to give XIIIγ). Using the "1 + 2 + 1" approach, mesobilirubin IIIα was also prepared. Mesobilirubins XIIγ and XIIIγ are more polar than mesobilirubin IIIα and unlike IIIα cannot effectively engage the propionic acid groups in intramolecular hydrogen bonding to the dipyrrinone components. The new mesobilirubins give exciton coupled circular dichroism spectra in the presence of human serum albumin or quinine, with the XIIγ isomer exhibiting Cotton effect intensities nearly as strong as those from the IIIα isomer; whereas, the XIIIγ isomer exhibits far weaker intensities. Mesobilirubin IIIα requires glucuronidation for hepatobiliary elimination; whereas, XIIγ and XIIIγ do not, and they are excreted intact across the liver into bile. The corresponding biliverdins XIIγ and XIIIγ are reduced only slowly by biliverdin IXα reductase, in contrast to the fast reduction of the natural IXα isomer. Graphical abstract: [Figure not available: see fulltext.]
Effect of meso-substituents on the osmium tetraoxide reaction and pinacol-pinacolone rearrangement of the corresponding vic-dihydroxyporphyrins
Chen,Medforth,Smith,Alderfer,Dougherty,Pandey
, p. 3930 - 3939 (2007/10/03)
To investigate the effects of electron-donating and electron-withdrawing substituents upon the reaction of porphyrins with osmium tetraoxide, and the pinacol-pinacolone rearrangement of the resulting diols, a series of meso-substituted porphyrins were prepared by total synthesis. Porphyrins with electron-donating substitutents at the meso-positions gave vic-dihydroxychlorins in which the adjacent pyrrole subunit was predominantly oxidized. No such selectivity was observed in a porphyrin containing a methoxycarbonyl as the electron-withdrawing group, whereas a formyl substituent again resulted in oxidation at the pyrrole unit adjacent to the meso-substituent. Under pinacol-pinacolone conditions, vic-dihydroxy chlorins containing 4-methoxyphenyl or 3,5-dimethoxyphenyl groups at the meso-position showed preferential migration of the ethyl group over the methyl group to give 8-ketochlorins, whereas the diol with an n-heptyl substituent under similar reaction conditions gave both 7- and 8-ketochlorins. In contrast, the diol containing a meso-formyl substituent produced the corresponding 7-ketochlorin exclusively. These results indicate that it is not possible to predict the reactivity of meso-substituted porphyrins in the osmium tetraoxide reaction nor the general substituent migratory aptitudes in the pinacol-pinacolone rearrangement based on simple electronic arguments, most likely because many parameters (e.g., meso-β-pyrrolic steric crowding and long-range electronic effects) ultimately determine the reactivity. The structural assignments of the porphyrin diols and the keto-analogues were confirmed by extensive 1H NMR studies; some of the dihydroxychlorins and ketochlorins were found to display unusual features in their 1H NMR spectra.
Substituted pyrroles
Mamardashvili,Kluyeva,Golubchicov
, p. 89 - 92 (2007/10/03)
A stepwise synthesis of a-unsubstituted pyrroles with desired substituents in the β-positions of the ring has been devised.
Synthesis and spectra of substituted pyrroles
Mamardashvili,Golubchikov
, p. 1056 - 1059 (2007/10/03)
A procedure was developed for synthesis of α-unsubstituted pyrroles with a desired arrangement of substituents in the β-positions.
SYNTHESIS OF RIGIDLY LINKED TRIAD MOLECULES BASED ON OCTAALKYLPORPHYRIN, CAPABLE OF MULTISTEP ELECTRON TRANSFER
Gribkov, A.A.,Borovkov, V.V.,Evstigneeva, R.P.,Sakata, Y.
, p. 905 - 915 (2007/10/02)
We have designed and carried out the synthesis of triad model systems containing octaalkylporphyrin, benzoquinone, and trichlorobenzoquinone with an oxidation-reduction potential gradient in the molecule.The quinone moieties are fixed relative to the porphyrin using spirononane and methylene spacers.
Electron transfer in bis-porphyrin donor-acceptor compounds with polyphenylene spacers shows a weak distance dependence
Helms, Anna,Heiler, David,McLendon, George
, p. 6227 - 6238 (2007/10/02)
A series of phenylene-bridged bis-porphyrin adducts have been synthesized, containing one, two, or three phenyl bridges. Complete synthetic details are provided. For studies of photochemical electron transfer, mixed metals wre incorporated, with zinc in one porphyrin macrocycle and FeIII (bis-imidazole) in the other macrocycle. When photoexcited, an electron is transferred from Zn to FeIII. The rate of this process drops only slowly with distance: kα exp(βr), with β = 0.4 A?-1. This dependence can be predicted by a simple theory which assumes that the drop does not reflect increased distance, but rather reflects the break in conjugation which occurs at each phenyl juncture due to the biphenyl twist angle of ca. 50°. Inefficient overlap in this angle results in a rate drop of ca. 6-fold per phenyl ring, in good agreement with the observed results.
THE TOTAL SYNTHESIS OF BILIVERDINS OF BIOLOGICAL INTEREST
Awruch, Josefina,Frydman, Benjamin
, p. 4137 - 4146 (2007/10/02)
The total synthesis of eight biliverdin isomers was achieved by oxidation of the corresponding 1,19-di-t-butyloxycarbonyl-b-bilenes.One of the biliverdin isomers is mesobiliverdin IXα - a dipropionate bilitriene -, one is a diacetate bilitriene, three iso
