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Panchromatic π‐Extended Porphyrins from Conjugation with Quinones
Author(s) -
Banala Srinivas,
Wurst Klaus,
Kräutler Bernhard
Publication year - 2016
Publication title -
chempluschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.801
H-Index - 61
ISSN - 2192-6506
DOI - 10.1002/cplu.201600115
Subject(s) - porphyrin , conjugated system , quinone , naphthoquinone , chromophore , chemistry , photochemistry , covalent bond , metal , benzoquinone , metal ions in aqueous solution , combinatorial chemistry , stereochemistry , organic chemistry , polymer
Typical porphyrins are coloured compounds due to their characteristic wavelength‐selective visible light absorptions. An exceptional “blackened” Zn II –porphyrin was recently obtained from fusing the β,β′‐positions of the porphyrin core with four quinone units. Here, studies with metal‐free and Ni II ‐containing analogues are reported. These quinone‐fused porphyrins were prepared from the corresponding β,β′‐tetrasulfolenoporphyrins via thermally generated porphyrindienes, which were trapped by [4+2] cycloaddition as benzoquinone cycloadducts, which were subsequently oxidised. By using this strategy, metal‐free and Ni II ‐containing porphyrins with one, two, three or four conjugated naphthoquinone moieties were prepared efficiently. The presence of the π‐conjugated naphthoquinone moieties changed the porphyrin chromophores profoundly, giving broadly absorbing “blackened” pigments. The influence of coordinated Ni II ions, or of the absence of a metal ion in the modified porphyrin core, on their structural and spectroscopic properties was explored. Blackened quinone‐conjugated porphyrins might be pigments suitable for solar energy conversion. With their unique peripheral functional groups they are also a set of porphyrins “programmed” for further covalent extension. Thus, they are building blocks for the preparation of supra‐porphyrinoid assemblies that might be useful in optoelectronics and in the nanosciences.