TY - JOUR
T1 - Photochromism of tetrahydroindolizines. Part XXVI
T2 - Mechanochemical synthesis, tunable photophysical properties and combined experimental and theoretical studies of novel photochromic tetrahydroindolizines
AU - Ahmed, Saleh A.
AU - El Guesmi, Nizar
AU - Alsulami, Anas A.B.
AU - Moussa, Ziad
AU - Alzahrani, Abdullah Y.A.
AU - Obaid, Rami J.
AU - Maurel, François
AU - Abdel-Wahab, Aboel Magd A.
N1 - Funding Information:
The authors would like to acknowledge the Deanship of Scientific Research at Umm Al-Qura University, for supporting this work by Grant code: 22UQU4320545DSR08. Dr. Ziad Moussa is grateful to the United Arab Emirates University (UAEU) and to the Research Office for supporting the research developed in his laboratory and reported herein (SUREPLUS Grant code G00003918).
Publisher Copyright:
© 2022 Elsevier B.V.
PY - 2023/3/1
Y1 - 2023/3/1
N2 - Herein, eighteen novel photochromic tetrahydroindolizines (THIs) have been successfully prepared using a well-established mechanochemical synthetic approach. These products were obtained in good to excellent yields and the purification process was relatively straightforward devoid of any isolation challenges. The new THIs incorporate various substituents in region C (base part) which include both electron donating and withdrawing groups in the ortho, meta and para positions of the phenyl ring. The absorption maxima (λmax) of both closed form (THI) and the colored form (betaine, after UV-irradiation) were spectrophotometrically determined in dichloromethane solution. The colored betaines displayed two absorption maxima, one between 472 and 485 nm, and the second one appearing in the white region between 658 and 724 nm with tailing extending to the near infra-red (NIR) region. The impact of the nature and position of substituent in the 10′b-phenyl ring on the absorption of the betaines indicated that substitution in the ortho-position with absorption maxima between 658 and 690 nm leads to a hypsochromic shift largely caused by the steric effect of the substituents in the o-position of the THI molecule 10′b-phenyl ring compared to the meta- and para-substituted species with absorption maxima between 700 and 724 nm. The calculated ring closure thermodynamic activation parameters of colored betaines were found to be in good agreement with previous reported results. The 1,5-electrocyclization reaction kinetics of the investigated photochromic THIs were monitored and calculated. Intriguingly, substitution with electron donating and withdrawing groups in the o-, m-, and p-positions of the phenyl ring enabled distinctive tunability of the kinetic behavior. Furthermore, possible mechanism of the thermal 1,5-electrocyclization back reaction of betaines was explored based on density functional theory calculations (DFT), delivering more understanding into ring opening and ring closure processes in addition to the distinct THI-substituents effect (region C). The geometries and the relative energies of the THI, betaine isomers, and transition states along reaction coordinates were optimized and assessed by DFT. Based on the obtained synthetic methodology results, unprecedent tunability of the photochromic properties and the combined experimental and theoretical studies, the current work launches a new dimension and contributes further developments to the field of high-performance photochromic materials.
AB - Herein, eighteen novel photochromic tetrahydroindolizines (THIs) have been successfully prepared using a well-established mechanochemical synthetic approach. These products were obtained in good to excellent yields and the purification process was relatively straightforward devoid of any isolation challenges. The new THIs incorporate various substituents in region C (base part) which include both electron donating and withdrawing groups in the ortho, meta and para positions of the phenyl ring. The absorption maxima (λmax) of both closed form (THI) and the colored form (betaine, after UV-irradiation) were spectrophotometrically determined in dichloromethane solution. The colored betaines displayed two absorption maxima, one between 472 and 485 nm, and the second one appearing in the white region between 658 and 724 nm with tailing extending to the near infra-red (NIR) region. The impact of the nature and position of substituent in the 10′b-phenyl ring on the absorption of the betaines indicated that substitution in the ortho-position with absorption maxima between 658 and 690 nm leads to a hypsochromic shift largely caused by the steric effect of the substituents in the o-position of the THI molecule 10′b-phenyl ring compared to the meta- and para-substituted species with absorption maxima between 700 and 724 nm. The calculated ring closure thermodynamic activation parameters of colored betaines were found to be in good agreement with previous reported results. The 1,5-electrocyclization reaction kinetics of the investigated photochromic THIs were monitored and calculated. Intriguingly, substitution with electron donating and withdrawing groups in the o-, m-, and p-positions of the phenyl ring enabled distinctive tunability of the kinetic behavior. Furthermore, possible mechanism of the thermal 1,5-electrocyclization back reaction of betaines was explored based on density functional theory calculations (DFT), delivering more understanding into ring opening and ring closure processes in addition to the distinct THI-substituents effect (region C). The geometries and the relative energies of the THI, betaine isomers, and transition states along reaction coordinates were optimized and assessed by DFT. Based on the obtained synthetic methodology results, unprecedent tunability of the photochromic properties and the combined experimental and theoretical studies, the current work launches a new dimension and contributes further developments to the field of high-performance photochromic materials.
KW - 1,5-Electrocyclization
KW - Heterocyclic dihydroisoquinoline bases
KW - Kinetics
KW - Photochromic
KW - Tetrahydroindolizine (THI)
KW - Theoretical calculations
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U2 - 10.1016/j.jphotochem.2022.114439
DO - 10.1016/j.jphotochem.2022.114439
M3 - Article
AN - SCOPUS:85145562590
SN - 1010-6030
VL - 437
JO - Journal of Photochemistry and Photobiology A: Chemistry
JF - Journal of Photochemistry and Photobiology A: Chemistry
M1 - 114439
ER -