Ultrasound and solvent-induced reversible chromism in a luminescent chalcogenidostannate

2014-04-30T11:36:36Z (GMT) by Hai-Yun Ren Zhi-Xue Ning Juan-Juan Hou
<p>Solvothermal treatment of a mixture of Se, SnC1<sub>2</sub>, CoC1<sub>2</sub>, and dien (dien = diethylenetriamine) generated yellow crystals of [Co(dien)<sub>2</sub>]<sub>2</sub>Sn<sub>2</sub>Se<sub>6</sub> (<b>1</b>), which could transform into black <b>2</b> with the same formula via rinsing with water. In the presence of water, ultrasound irradiation of black <b>2</b> went back to yellow <b>1</b>. The reversible ultrasound and solvent-induced chromism has never been observed before. Compared with yellow <b>1</b>, hyperchromism was apparent around 550 nm in the visible absorption spectrum of <b>2</b>. The fluorescent properties for <b>1</b> and <b>2</b> were investigated and the mechanisms were validated by density functional theory calculations on the experimental geometries. In addition, electron paramagnetic resonance spectra of yellow <b>1</b> are similar to chromic black <b>2</b> in the signal at <i>g</i> = 4.22 and <i>g</i> = 2.19; the signal at <i>g</i> = 2.19 of <b>2</b> shows a sharp increase.</p>