HOMEPRODUCTSCOMPANYCONTACTFAQResearchDictionaryPharmaSign Up FREE or Login

Siamese-twin porphyrin: a pyrazole-based expanded porphyrin of persistent helical conformation.

Abstract
The 3+3-type synthesis of a pyrazole-based expanded porphyrin 22 H4, a hexaphyrin analogue named Siamese-twin porphyrin, and its homobimetallic diamagnetic nickel(II) and paramagnetic copper(II) complexes, 22 Ni2 and 22 Cu2, are described. The structure of the macrocycle composed of four pyrroles and two pyrazoles all linked by single carbon atoms, can be interpreted as two conjoined porphyrin-like subunits, with the two opposing pyrazoles acting as the fusion points. Variable-temperature 1D and 2D NMR spectroscopic analyses suggested a conformationally flexible structure for 22 H4. NMR and UV/Vis spectroscopic evidence as well as structural parameters proved the macrocycle to be non-aromatic, though each half of the molecule is fully conjugated. UV/Vis and NMR spectroscopic titrations of the free base macrocycle with acid showed it to be dibasic. In the complexes, each metal ion is coordinated in a square-planar fashion by a dianionic, porphyrin-like {N4} binding pocket. The solid-state structures of the dication and both metal complexes were elucidated by single-crystal diffractometry. The conformations of the three structures are all similar to each other and strongly twisted, rendering the molecules chiral. The persistent helical twist in the protonated form of the free base and in both metal complexes permitted resolution of these enantiomeric helimers by HPLC on a chiral phase. The absolute stereostructures of 22 H6(2+), 22 Ni2, and 22 Cu2 were assigned by a combination of experimental electronic circular dichroism (ECD) investigations and quantum-chemical ECD calculations. The synthesis of the first member of this long-sought class of expanded porphyrin-like macrocycles lays the foundation for the study of the interactions of the metal centers within their bimetallic complexes.
AuthorsLina K Blusch, Yasmin Hemberger, Kevin Pröpper, Birger Dittrich, Franziska Witterauf, Michael John, Gerhard Bringmann, Christian Brückner, Franc Meyer
JournalChemistry (Weinheim an der Bergstrasse, Germany) (Chemistry) Vol. 19 Issue 19 Pg. 5868-80 (May 03 2013) ISSN: 1521-3765 [Electronic] Germany
PMID23576406 (Publication Type: Journal Article)
CopyrightCopyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Join CureHunter, for free Research Interface BASIC access!

Take advantage of free CureHunter research engine access to explore the best drug and treatment options for any disease. Find out why thousands of doctors, pharma researchers and patient activists around the world use CureHunter every day.
Realize the full power of the drug-disease research graph!


Choose Username:
Email:
Password:
Verify Password:
Enter Code Shown: