Theoretical investigation into the effect of atomic electronegativity related chalcogen on ESIPT behaviour for the novel biphenyl-modified 2-(2’-hydroxyphenyl)benzothiazole compounds

Inspired by the remarkable photochemical and photophysical properties of novel 2-(2’-hydroxyphenyl)benzothiazole (HBT) derivatives that could be potentially applied across various disciplines, in this work, effects of atomic electronegativity of chalcogen elements on excited state hydrogen bond effects and excited state intramolecular proton transfer (ESIPT) reaction of the biphenyl-modified HBT derivatives (i.e. HBT-HH-O, HBT-HH-S and HBT-HH-Se) are focused. By comparing the structural changes and infrared (IR) vibrational spectra of the HBT-HH fluorophores in toluene solvent, combined with the preliminary detection of hydrogen bond interaction by core-valence bifurcation (CVB) index, we can conclude that the hydrogen bond could be strengthened in S1 state, which is favourable for the occurrence of ESIPT reactions. The charge recombination behaviour of hydrogen bond induced by photoexcitation also further illustrates this point. Via constructing potential energy curves (PECs) based on restrictive optimisation and searching transition state (TS) form, we confirm the variations of atomic electronegativity of chalcogen have the regulatory effect on the ESIPT behaviour for HBT-HH derivatives, that is, the lower the atomic electronegativity is more conducive to the ESIPT reaction.</p

Prevalence of HIV, syphilis among drug users from the detoxification center and community.

<p><i>CI</i>: confidence interval.</p>*<p>Denotes significance at alpha value of 0.05.</p

Major behavioral and serologic variables by Hukou among drug users from the detoxification center and community.

<p>IDU: injection drug use.</p>*<p>Variable represents characteristic of injection drug users.</p

Hippocampus brain injury HE staining result (400×).

<p>A, control group; B, hypoxic 1d; C, hypoxic 3d; D, ischemia+hypoxic 1d; E, ischemia+hypoxic 3d. </p

The p-ERK levels in the brains tissues from the hypoxic group and the ischemic+hypoxic group were both lower than that in the brains from the controls by immunohistochemistry analysis.

<p> A, control group (400×); B, hypoxic 1d (400×); C, ischemia+hypoxic 1d (400×).</p

Social demographic characteristics among drug users from the detoxification center and community.

<p>IDU injection drug use. <i>CI</i> confidence interval.</p>*<p>Denotes significance at alpha value of 0.05.</p

The HE stains result of injury of hippocampus in 21d neonate rat (400×).

<p>A, control group; B, hypoxic group; C, ischemia+hypoxic group.</p

Drug use and sexual behaviors among drug users from the detoxification center and community.

<p>IDU: injection drug use. <i>CI:</i> confidence interval.</p>*<p>Denotes significance at alpha value of 0.05.</p>**<p>Variable represents characteristic of injection drug users.</p>#<p>Variable represents characteristic of those engaging in commercial sex.</p

HE staining result of brain injury around lateral ventricle (400×).

<p>A, control group; B, hypoxic 1d; C, hypoxic 3d; D, ischemia+hypoxic 1d; E, ischemia+hypoxic 3d.</p

Neural cell apoptosis testing by TUNEL, much more TUNEL positive cells were observed in hypoxic and ischemic+hypoxic group than the controls (400×).

<p>A, control group; B, hypoxic 1d; C, ischemia+hypoxic 1d.</p