Manipulating Exciton Dynamics in Glassy Porphyrin Assemblies toward Near-Infrared Luminescence

03 June 2025, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Despite the high demand of cutting-edge applications for near-infrared (NIR)-luminescent chromophores, their development is hindered by the decrease in the emission efficiency with the narrowing optical bandgap (energy gap law). Herein, we established a correlation between the structural and NIR-luminescent properties of glassy porphyrin assemblies by comparing a systematic series of 11 proquinoidal-arylene-linked porphyrins 1π, each bearing two 3,4,5-tris((S)-dihydrocitronellyloxy)phenyl groups. The elastic and branched alkyl substituents were found to play a pivotal role in defining the distinctive photophysical properties of 1π. Specifically, 1π exhibited a bathochromic shift of the electronic absorption band, which was attributed to the slipped-cofacial ar-rangement of π-stacked porphyrin planes, and a substantial Stokes shift in the solid-state photoluminescence, which was mediated by exciton–phonon coupling within an elastic π-stacking lattice. The double-strand state (1π)2 formed an excimers and exhibited NIR photoluminescence in cyclohexane. The NIR photoluminescence was further enhanced in the abovementioned assemblies, in which case the increased Stokes shift led to solid-state NIR photoluminescence extending into the NIR-II region (> 1000 nm). The results of femtosecond photoluminescence upconversion measurements indicated that the NIR luminescence largely originated from exciton self-trapping.

Keywords

Near-infrared luminescence
Porphyrin
excimer
self-trapped exciton

Supplementary materials

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Title
SI for Manipulating Exciton Dynamics in Glassy Porphyrin Assemblies toward Near-Infrared Luminescence
Description
Results of (i) thermodynamic analysis in cyclohexane, (ii) GIWAXD, DSC, and CLSM measurements performed on thin films, (iii) pico- and femtosecond photodynamic analysis, (iv) theoretical investiga-tions using (TD)DFT calculations, and (v) full characterization of the newly synthesized compounds are provided in the Supporting Information.
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