10.1021/acs.jpcc.8b07408.s002
Sheng Ding
Sheng
Ding
He Lin
He
Lin
Yuming Yu
Yuming
Yu
Lang Liu
Lang
Liu
Caiming Deng
Caiming
Deng
Jianzhang Zhao
Jianzhang
Zhao
Dianzeng Jia
Dianzeng
Jia
Molecular Orbital Delocalization/Localization-Induced
Crystal-to-Crystal Photochromism of Schiff Bases without <i>ortho</i>-Hydroxyl Groups
American Chemical Society
2018
photochromic Schiff bases
Photochromic Schiff bases
decolored form
photochromism
Hydroxyl Groups Solid-state photochromic compounds
UV
2018-09-09 00:00:00
Dataset
https://acs.figshare.com/articles/dataset/Molecular_Orbital_Delocalization_Localization-Induced_Crystal-to-Crystal_Photochromism_of_Schiff_Bases_without_i_ortho_i_-Hydroxyl_Groups/7242989
Solid-state
photochromic compounds can be used in molecular switch
and memory, smart window, and so forth. However, a new photochromic
mechanism was rarely reported. Photochromic Schiff bases without <i>ortho</i>-hydroxyl groups (thioamide hydrazones) have been prepared,
which are drastically different from the traditional photochromic
Schiff bases (e.g., salicylal anils and pyrazolone thiosemicarbazones).
Systematic experimental and theoretical studies of thioamide hydrazone
confirm the crystal-to-crystal photochromism and thermo-enhanced photochromism.
The original faint yellow form changes to yellow after UV irradiation
and can further be bleached by visible light irradiation. Besides,
the decolored form can automatically change to yellow in dark at room
temperature or by heating. The structures of the three forms (the
original form, the colored form, and the decolored form) show that
the intramolecular torsion and vibration lead to the increase/decrease
of the donor (nitrogen atom)–acceptor (sulfur atom) distance
of the intermolecular hydrogen bond (N–H···S).
It further results in the delocalization/localization of the highest
occupied molecular orbital, which is verified by the density functional
theory calculation. Thus, the absorption intensity increase/decrease
is attributed to the reversible switch between the π →
π* and n → π* transition. The conclusion was further
confirmed by an analogue compound without the thiocarbonyl group.
The switch of the transition is accompanied by intermolecular orbital
dehybridization/hybridization during the photochromism induced by
light because the primitive cell contains more than one molecule.