Open AccessStructure and Conformation of Novel BODIPY Ugi Adducts
Author(s) -
ArroyoCórdoba Ismael Javier,
GamboaVelázquez Gonzalo,
AvilaOrtiz Claudia Gabriela,
LeyvaRamírez Marco A.,
CortezPicasso María Teresa,
GarcíaRevilla Marco A.,
RamírezOrnelas Diana E.,
PeñaCabrera Eduardo,
Juaristi Eusebio
Publication year - 2022
Publication title -
chemistryopen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 29
ISSN - 2191-1363
DOI - 10.1002/open.202200197
Subject(s) - chemistry , bodipy , adduct , aniline , crystallography , ring flip , crystal structure , chemical shift , aromaticity , ring (chemistry) , molecule , organic chemistry , physics , quantum mechanics , fluorescence
Two novel BODIPY‐Ugi (boron dipyrromethene) adducts exhibit peculiar room temperature (T=20 °C) H‐1 NMR spectra in that several protons located at the aromatic aniline‐type ring are lost in the baseline. This observation revealed the existence of a dynamic conformational process where rotation around the C−N bond is hindered. Variable‐temperature H‐1 and C‐13 NMR spectroscopic analysis confirmed this conclusion; that is, low‐temperature spectra show distinct signals for all four aromatic protons below coalescence, whereas average signals are recorded above coalescence (T=+120 °C). Particularly interesting was the rather large difference in chemical shifts for the ortho protons below coalescence, Δδ=1.45 ppm, which was explained based on DFT computational analysis. Indeed, the calculated lowest‐energy gas‐phase conformation of the BODIPY Ugi adducts locates one half of the aniline‐type ring in the shielding anisotropic cone of the bridge phenyl ring in the BODIPY segment. This is in contrast to the solid‐state conformation established by X‐ray diffraction analysis that shows a nearly parallel arrangement of the aromatic rings, probably induced by crystal packing forces.