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Fluorosolvatochromism of monomethyl indoles: further evidence in support of a new photophysical model for the indole chromophore
Author(s) -
Catalán Javier
Publication year - 2015
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.3414
Subject(s) - bathochromic shift , chemistry , solvatochromism , chromophore , indole test , solvent , photochemistry , stereochemistry , fluorescence , organic chemistry , quantum mechanics , physics
In this study, we investigated whether a change exists in the emitting state of the monomethyl indoles, dissolved in 1‐chlorobutane (ClB) and 2‐methylbutane (2MB), resulting from a dipolarity increase of the solvent. Analysis of the solvatochromism of monomethyl indoles in ClB at 343–133 K and in 2MB at 293–113 K leads to the following conclusions: (i) the state S 1 is the greatest contributor to the structured emission of 4‐Me‐, 5‐Me‐, and 7‐MeIndole; (ii) lowering the temperature of solutions of these compounds in ClB or 2MB below 113 K leads not to a structureless emission or bathochromic shift typical for an S 1 ′ state; (iii) 1‐Me‐, 2‐Me‐, 3‐Me‐, and 6‐MeIndole exhibit a structured emission typical for an S 1 state in 2MB but show an invariably structureless emission, subject to a red shift in ClB as the temperature is lowered, which is suggestive for an S 1 ′ emitting state; and (iv) lowering the temperature of solutions of the previous compounds below 133 K causes their emission spreading to become structured and blueshifted (two typical features for an emission from their S 1 state). Copyright © 2015 John Wiley & Sons, Ltd.