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Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method
Published on: July 19, 2019
Extending conjugation in porphyrin dimer carbocations
Karl J Thorley1, Harry L Anderson
1Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, UKOX1 3TA.
Organic & Biomolecular Chemistry
|June 8, 2010
Summary
Researchers synthesized porphyrin dimer carbocations with tunable near-IR absorption. Longer conjugated bridges shift absorption to longer wavelengths, offering potential for new optical materials.
Area of Science:
- Organic Chemistry
- Materials Science
- Photophysics
Background:
- Porphyrins are versatile macrocycles with diverse applications.
- Conjugated systems are crucial for optical and electronic properties.
- Near-infrared (NIR) absorbing materials are of significant interest.
Purpose of the Study:
- To synthesize novel porphyrin dimer carbocations.
- To investigate the effect of conjugated bridge length on NIR absorption.
- To understand the relationship between structure and spectral properties.
Main Methods:
- Addition of alkynyl porphyrins to carbonyl compounds.
- Acid-catalyzed cyclization to form carbocations.
- Spectroscopic analysis (UV-Vis-NIR) in solution.
Main Results:
- A series of porphyrin dimer tertiary alcohols were prepared.
- Conjugated carbocations with 3-9 carbon bridges were formed.
- Strong NIR absorption (1000-1800 nm) was observed, with a bathochromic shift per alkyne.
- The longest chromophore absorbed at 1623 nm.
- Absorption properties were influenced by pi-system symmetry.
- Cation stability decreased with increasing bridge length.
Conclusions:
- Alkynyl porphyrin addition provides access to NIR-absorbing carbocations.
- Bridge length significantly tunes NIR absorption, similar to polymethine cyanines.
- Symmetry plays a key role in spectral characteristics.
- Stability is a limiting factor for longer bridge systems.
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