Volume 64, Issue 28 e202505772
Research Article

Modulation of Photoluminescence of BODIHY Dye Using Water-Soluble Coordination Cages With Different Shapes

Valiyakath Abdul Rinshad

Valiyakath Abdul Rinshad

Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bengaluru, 560012 India

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Prajoy Kumar Mitra

Prajoy Kumar Mitra

School of Chemistry, Indian Institute of Science Education and Research, Thiruvananthapuram, 695551 India

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Sailendra Pradhan

Sailendra Pradhan

Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bengaluru, 560012 India

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Dr. Yapamanu Adithya Lakshmanna

Corresponding Author

Dr. Yapamanu Adithya Lakshmanna

School of Chemistry, Indian Institute of Science Education and Research, Thiruvananthapuram, 695551 India

E-mail: [email protected]; [email protected]

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Prof. Dr. Partha Sarathi Mukherjee

Corresponding Author

Prof. Dr. Partha Sarathi Mukherjee

Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bengaluru, 560012 India

E-mail: [email protected]; [email protected]

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First published: 07 May 2025

Graphical Abstract

The fluorescence of Boron difluoride hydrazone (BODIHY) (G1) dye was effectively controlled through confinement within coordination cages of different shapes. The encapsulation of G1 within a double-square cage (MC1) resulted in a highly emissive solution, whereas similar confinement within an octahedral cage (MC2) exhibited a weak emission. Moreover, we achieved turn-on emission of G1 through the displacement of G1 from MC2 to MC1.

Abstract

The confinement of guest molecules within supramolecular hosts can alter their photophysical properties. However, the shapes of the hosts in regulating the guest's emission remains underexplored. Herein, we investigate how the shape of the host alters the emission behavior of boron difluoride hydrazone (BODIHY) (G1) dye encapsulated within two iso-stoichiometric water-soluble coordination cages: MC1 (double-square cage) and MC2 (octahedral cage). Encapsulation of G1 within MC1 results in a highly emissive solution, whereas similar confinement in MC2 leads to a non-emissive host–guest solution. A similar trend was observed with different sets of iso-stoichiometric cages MC3 (double-square cage) and MC4 (octahedral cage). Using a combination of femtosecond transient absorption and time-resolved fluorescence spectroscopy, we observed that the disparity in fluorescence behavior of BODIHY is attributed to charge transfer interactions between the guest and ligand panels of cages. The shape of the coordination cage dictates the preorganization of the guest within the cavity, thereby suppressing or promoting this charge transfer interactions. Moreover, we demonstrate a turn-on emission of BODIHY dye due to its preferential binding to a double-square cage. These findings provide fundamental insights into host-mediated modulation of the guest's photophysics and offer a blueprint for designing supramolecular systems with tunable emissive behavior.

Conflict of Interests

The authors declare no conflict of interest.

Data Availability Statement

Data involved in this work are included in this article and the corresponding supplementary materials. The crystal structure of (G1)2⊂MC1 is available in the CCDC database under CCDC-2403903.

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