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The characterization of the stability of self-assembled supramolecular systems is critical for numerous applications that rely on non-covalent interactions between the components. However, in phthalocyanines (Pcs), the coordination of ligands to the central metal is typically not accompanied by significant spectral changes, complicating the determination of association constants (K1). In this study, we developed a reliable and widely applicable method based on fluorescence and absorption spectroscopy that allows straightforward determination of K1 for a broad range of ligands, from heterocyclic to purely aliphatic, with weak (K1~10^2 M⁻¹) to strong (K1~10^7 M⁻¹) binding affinities. The method benefits from the full characterization of unique J-dimers of Pcs, which are formed via coordination between the peripheral substituent of one molecule and the central metal of another Pc in a series of metal octa(dialkylamino)azaphthalocyanines. These J-dimers exhibit significantly red-shifted absorption bands (up to ~710 nm), and retained red fluorescence with significant Stokes shifts (~35-40 nm), making them ideal for spectroscopic analysis. The developed method allowed for the direct determination of dimerization constants (KD) by monitoring temperature-induced J-dimer disassembly. Determined KD values ranged from 10^8 to 10^15 M⁻¹, with the bulkiness of the coordinating substituents being the primary factor affecting dimerization strength. The insights gained could be instrumental in the rational design of self-coordinating supramolecular systems that are important in, for example, energy and electron transfer processes.

Rights:

• cc-by-nc-3.0
  

Keyword: phthalocyanine, J-dimers, supramolecular system, association constant, ligand

Date published: 2024-12-31

Publisher: Royal Society of Chemistry (RSC)

Journal:

• Inorganic Chemistry Frontiers (ISSN: 20521553) vol. 12 issue. 4 p. 1590-1608

Funding:

• Grantová Agentura České Republiky 23-06177S
• Ministerstvo Školství, Mládeže a Tělovýchovy CZ.02.01.01/00/22_008/0004607
• Ministry of Education, Youth and Sports, Czech Republic LL2318
• Charles University, Czech Republic SVV 260 666

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1039/d4qi02834a

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Updated at: 2025-02-13 12:30:44 +0900

Published on MDR: 2025-02-13 12:30:44 +0900