Solvent effects on the intramolecular charge transfer excited state of 3CzClIPN: a broadband transient absorption study

• Published in: Physical chemistry chemical physics : PCCP Vol. 26; no. 2; pp. 139 - 145
• Main Authors: Zheng, Ruofei, Cheng, Meixin, Ma, Ruishu, Schipper, Derek, Pichugin, Kostyantyn, Sciaini, Germán
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 03.01.2024
• Subjects: Absorption; Broadband; Carbazoles; Charge transfer; Excitation; Organic chemistry; Solvation; Solvent effect; Solvents
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d3cp04975b

The prediction of solvent properties using molecular probes often relies on correlating steady-state absorption and fluorescence measurements, as well as determining absorption maxima and/or Stokes shifts. In this study, we employ femtosecond broadband transient absorption (fs-bb-TA) spectroscopy to investigate the spectroscopic behaviour of the intramolecular charge transfer (ICT) excited state of 3CzClIPN (2,4,6-tri(9 H -carbazol-9-yl)-5-chloroisophthalonitrile), a representative ICT organic molecule, in both aromatic and non-aromatic solvents. Unlike observations in non-aromatic media, fs-bb-TA spectra of 3CzClIPN in aromatic solvents exhibit enhanced spectral broadening that strongly correlates with the solvent's polarity. We hypothesise that this spectral broadening originates from a wider configurational energy landscape experienced by the positively charged carbazole Cz + group, owing to the larger size and, consequently, reduced solvation effectiveness of aromatic solvent molecules. Broadening of intramolecular charge-transfer excited-state absorption of 3CzClIPN in aromatic solvents: a local probe of the medium's polarity.