Enforcing Extended Porphyrin J-Aggregate Stacking in Covalent Organic Frameworks
Niklas Keller1, Mona Calik1, Dmitry Sharapa2
1Department of Chemistry and Center for NanoScience (CeNS) , University of Munich (LMU) , Butenandtstrasse 5-13 , 81377 Munich , Germany.
Journal of the American Chemical Society
|November 6, 2018
Summary
Covalent organic frameworks (COFs) enable porphyrin J-aggregates for enhanced light harvesting. This breakthrough offers new possibilities for photocatalysis, solar energy, and biomedical applications.
Area of Science:
- Materials Science
- Supramolecular Chemistry
- Organic Chemistry
Background:
- Covalent organic frameworks (COFs) offer tunable porous materials for diverse applications.
- Porphyrins are crucial in electroactive materials but face packing challenges in COFs.
- Nonplanar porphyrin structures and electrostatic interactions hinder crystalline assembly.
Purpose of the Study:
- To synthesize and characterize porphyrin-containing imine-linked COFs with specific linear bridges.
- To investigate the structural and optical properties of these novel porphyrin-based COFs.
- To explore the formation of porphyrin J-aggregates within a COF framework.
Main Methods:
- Synthesis of porphyrin-containing imine-linked COFs using various dicarboxaldehydes.
- X-ray diffraction analysis to determine crystal structures.
- Density-functional theory (DFT) calculations for structural elucidation.
- Steady-state and time-resolved optical spectroscopy to study optical properties.
Main Results:
- Successful synthesis of porphyrin-based COFs with thieno[3,2-b]thiophene-2,5-dicarboxaldehyde bridges.
- Elucidation of crystal structure revealing loss of porphyrin symmetry and formation of slipped J-aggregate stacks.
- Observation of porphyrin J-aggregates on a >50 nm scale with red-shifted Q-bands and enhanced absorption.
- Demonstration of COFs as templates for covalently embedded porphyrin J-aggregates.
Conclusions:
- Porphyrin-based COFs can template the formation of extended porphyrin J-aggregates.
- This strategy overcomes porphyrin packing challenges in crystalline frameworks.
- These COFs are promising for photocatalysis, solar light harvesting, and biomedical applications.
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