Assessing the Structure of Octastate Molecular Switches Using 1H NMR Density Functional Theory Calculations

Slim Hadj Mohamed, Jean Quertinmont, Stéphanie Delbaere, Lionel Sanguinet, Benoît Champagne

Research output: Contribution to journalArticle

Abstract

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.
Original languageEnglish
Pages (from-to)1800-1808
Number of pages9
JournalThe Journal of Physical Chemistry C
Volume122
Issue number3
DOIs
Publication statusPublished - 25 Jan 2018

Fingerprint

Density functional theory
Protons
switches
Switches
Nuclear magnetic resonance
Chemical shift
density functional theory
nuclear magnetic resonance
chemical equilibrium
protons
Photochromism
photochromism
Enthalpy
Stabilization
stabilization
enthalpy
signatures
energy
oxazolidine
interactions

Cite this

@article{0bf168844860431db9bf24f516311db9,
title = "Assessing the Structure of Octastate Molecular Switches Using 1H NMR Density Functional Theory Calculations",
abstract = "Density functional theory calculations are used to revealthe relationships between the structures, energies, and NMR signatures ofan octastate molecular switch composed of a dithienylethene (DTE) unitcovalently linked to an indolino[2,1-b]oxazolidine (BOX) moiety throughan ethylenic junction. Both the DTE and BOX moieties can adopt openor closed forms. The ethylenic junction can be Z or E, but the latter hasbeen confirmed to be, by far, more stable than the former for all BOX/DTE combinations. In addition, when the DTE is open, the two thienylunits can fold to form parallel conformers, by opposition to theantiparallel or unfolded conformers. Usually parallel conformers present ahigher energy than the antiparallel ones, but in the case of compound 2having 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 themost 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.",
author = "{Hadj Mohamed}, Slim and Jean Quertinmont and St{\'e}phanie Delbaere and Lionel Sanguinet and Beno{\^i}t Champagne",
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Assessing the Structure of Octastate Molecular Switches Using 1H NMR Density Functional Theory Calculations. / Hadj Mohamed, Slim; Quertinmont, Jean; Delbaere, Stéphanie; Sanguinet, Lionel; Champagne, Benoît.

In: The Journal of Physical Chemistry C, Vol. 122, No. 3, 25.01.2018, p. 1800-1808.

Research output: Contribution to journalArticle

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

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PY - 2018/1/25

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N2 - Density functional theory calculations are used to revealthe relationships between the structures, energies, and NMR signatures ofan octastate molecular switch composed of a dithienylethene (DTE) unitcovalently linked to an indolino[2,1-b]oxazolidine (BOX) moiety throughan ethylenic junction. Both the DTE and BOX moieties can adopt openor closed forms. The ethylenic junction can be Z or E, but the latter hasbeen confirmed to be, by far, more stable than the former for all BOX/DTE combinations. In addition, when the DTE is open, the two thienylunits can fold to form parallel conformers, by opposition to theantiparallel or unfolded conformers. Usually parallel conformers present ahigher energy than the antiparallel ones, but in the case of compound 2having 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 themost 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 revealthe relationships between the structures, energies, and NMR signatures ofan octastate molecular switch composed of a dithienylethene (DTE) unitcovalently linked to an indolino[2,1-b]oxazolidine (BOX) moiety throughan ethylenic junction. Both the DTE and BOX moieties can adopt openor closed forms. The ethylenic junction can be Z or E, but the latter hasbeen confirmed to be, by far, more stable than the former for all BOX/DTE combinations. In addition, when the DTE is open, the two thienylunits can fold to form parallel conformers, by opposition to theantiparallel or unfolded conformers. Usually parallel conformers present ahigher energy than the antiparallel ones, but in the case of compound 2having 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 themost 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.

U2 - 10.1021/acs.jpcc.7b11221

DO - 10.1021/acs.jpcc.7b11221

M3 - Article

VL - 122

SP - 1800

EP - 1808

JO - Journal of physical chemistry. C

JF - Journal of physical chemistry. C

SN - 1932-7447

IS - 3

ER -