TY - JOUR
T1 - Assessing the Structure of Octastate Molecular Switches Using 1H NMR Density Functional Theory Calculations
AU - Hadj Mohamed, Slim
AU - Quertinmont, Jean
AU - Delbaere, Stéphanie
AU - Sanguinet, Lionel
AU - Champagne, Benoît
N1 - Funding Information:
This work, carried out within the MORIARTY project, has benefited from financial support from Wallonie-Bruxelles International (WBI), from the Fund for Scientific Research (F.R.S.-FNRS), from the French Ministry of Foreign and European Affairs, and from the Ministry of Higher Education and Research in the frame of the Hubert Curien partnerships. S.H.M. thanks the Fonds Spećial de Recherche of UNamur for his Ph.D. grant while J.Q. thanks the “Actions de Recherche Concerteés” (ARC) of the Direction geńeŕ ale de l’Enseigne-ment non Obligatoire et de la Recherche Scientifique of the French Community of Belgium, under convention no. 15/20- 068, for his Ph.D. grant. This work was also supported by funds from the Francqui Foundation. S.D. and L.S. thank ANR SIMI 7 for financial support (grant no.: 2011 BS08 007 02). The calculations were performed on the computers of the Consortium des Équipements de Calcul Intensif, including those of the Technological Platform of High-Performance Computing, for which we gratefully acknowledge the financial support of the FNRS-FRFC (Conventions No. 2.4.617.07.F and 2.5020.11) and of the University of Namur.
Publisher Copyright:
© 2017 American Chemical Society.
Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2018/1/25
Y1 - 2018/1/25
N2 - Density functional theory calculations are used to reveal the relationships between the structures, energies, and NMR signatures of an octastate molecular switch composed of a dithienylethene (DTE) unit covalently linked to an indolino[2,1-b]oxazolidine (BOX) moiety through an ethylenic junction. Both the DTE and BOX moieties can adopt open or closed forms. The ethylenic junction can be Z or E, but the latter has been confirmed to be, by far, more stable than the former for all BOX/DTE combinations. In addition, when the DTE is open, the two thienyl units can fold to form parallel conformers, by opposition to the antiparallel or unfolded conformers. Usually parallel conformers present a higher energy than the antiparallel ones, but in the case of compound 2 having a bulky substituent (R = pPh-SMe) on the terminal thienyl group, the enthalpy of one conformer is very close (1−2 kJ mol−1) to that of the most stable antiparallel one, making photocyclization less efficient. These conformational differences and the presence of parallel DTE forms have been substantiated by analyzing experimental 1H NMR chemical shifts in light of their calculated values. These 1H NMR chemical shift calculations led to the following statements: (i) Going from state I (DTE open, BOX closed) to state II (both DTE and BOX are open) the H8 proton of compound 1 (R = Me) is deshielded by ∼0.15 ppm. (ii) The deshielding of H8 proton of compound 2 is larger and attains 0.41 ppm whereas H7 is more shielded by 0.11 ppm. (iii) Then, going from compound 1 to compound 2 leads to deshielding of both H7 and H8 protons. As a consequence, the difference of photochromism gating efficiency among compounds 1, 2, and 3 (R = pPh-OMe) can be attributed to the stabilization of parallel conformer due to an establishment of an intramolecular interaction with BOX opening.
AB - Density functional theory calculations are used to reveal the relationships between the structures, energies, and NMR signatures of an octastate molecular switch composed of a dithienylethene (DTE) unit covalently linked to an indolino[2,1-b]oxazolidine (BOX) moiety through an ethylenic junction. Both the DTE and BOX moieties can adopt open or closed forms. The ethylenic junction can be Z or E, but the latter has been confirmed to be, by far, more stable than the former for all BOX/DTE combinations. In addition, when the DTE is open, the two thienyl units can fold to form parallel conformers, by opposition to the antiparallel or unfolded conformers. Usually parallel conformers present a higher energy than the antiparallel ones, but in the case of compound 2 having a bulky substituent (R = pPh-SMe) on the terminal thienyl group, the enthalpy of one conformer is very close (1−2 kJ mol−1) to that of the most stable antiparallel one, making photocyclization less efficient. These conformational differences and the presence of parallel DTE forms have been substantiated by analyzing experimental 1H NMR chemical shifts in light of their calculated values. These 1H NMR chemical shift calculations led to the following statements: (i) Going from state I (DTE open, BOX closed) to state II (both DTE and BOX are open) the H8 proton of compound 1 (R = Me) is deshielded by ∼0.15 ppm. (ii) The deshielding of H8 proton of compound 2 is larger and attains 0.41 ppm whereas H7 is more shielded by 0.11 ppm. (iii) Then, going from compound 1 to compound 2 leads to deshielding of both H7 and H8 protons. As a consequence, the difference of photochromism gating efficiency among compounds 1, 2, and 3 (R = pPh-OMe) can be attributed to the stabilization of parallel conformer due to an establishment of an intramolecular interaction with BOX opening.
UR - http://www.scopus.com/inward/record.url?scp=85041189101&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.7b11221
DO - 10.1021/acs.jpcc.7b11221
M3 - Article
SN - 1932-7447
VL - 122
SP - 1800
EP - 1808
JO - Journal of Physical Chemistry C: Nanomaterials and interfaces
JF - Journal of Physical Chemistry C: Nanomaterials and interfaces
IS - 3
ER -