Banić Nemanja, Vraneš Milan, Abramović Biljana, Csanádi János, Gadžurić Slobodan
Faculty of Sciences, Department of Chemistry, Biochemistry and Environmental Protection, University of Novi Sad, Trg Dositeja Obradovića 3, 21000 Novi Sad, Serbia.
Dalton Trans. 2014 Nov 7;43(41):15515-25. doi: 10.1039/c4dt01836b.
In this work a 1-(2-hydroxyethyl)-3-methylimidazolium nitrate ionic liquid, [HO(CH2)2mim]NO3, has been synthesized in order to serve as a new thermochromic material upon addition of cobalt(II) ions. Spectrophotometric measurements of a series of cobalt(II) nitrate and cobalt(II) chloride solutions in [HO(CH2)2mim]NO3 at 298.15, 308.15, 318.15, 328.15, and 338.15 K, were performed. Based on the recorded spectra, the overall stability constants and thermodynamic parameters for the cobalt(II) associations with chloride and nitrate ions were calculated. The thermodynamic calculations suggest that thermochromism is not observed in the ionic medium due to a small entropy change during the replacement of nitrate with chloride ions in the co-ordination sphere of cobalt(II). The absence of the molecular solvent was also the reason for the lack of thermochromism. Thus, cobalt(II) solutions in [HO(CH2)2mim]NO3 and water mixtures were studied as a new and green medium that can be used for the auto-regulation of the light intensity and shade protection. The investigated system with water upon addition of cobalt(II) was found to be a far more efficient and responsive thermochromic medium for all of the studied systems up until now. The structure of [HO(CH2)2mim]NO3 was confirmed by both (1)H NMR and IR spectroscopy. Also, the efficiency of different advanced oxidation processes (UV-induced photolysis, UV/H2O2 photolysis, heterogeneous photocatalysis using TiO2 Degussa P25 and TiO2 with 7.24%, w/w Fe catalysts) for [HO(CH2)2mim]NO3 degradation were investigated. The reaction intermediates formed during the photo-oxidation process were identified using LC-ESI-MS/MS and (1)H NMR techniques.
在本研究中，合成了1-(2-羟乙基)-3-甲基咪唑鎓硝酸盐离子液体[HO(CH₂)₂mim]NO₃，以便在添加钴(II)离子后用作一种新型热致变色材料。对一系列硝酸钴(II)和氯化钴(II)溶液在[HO(CH₂)₂mim]NO₃中于298.15、308.15、318.15、328.15和338.15 K下进行了分光光度测量。基于记录的光谱，计算了钴(II)与氯离子和硝酸根离子缔合的总稳定常数和热力学参数。热力学计算表明，由于在钴(II)配位球中用氯离子取代硝酸根离子的过程中熵变较小，在离子介质中未观察到热致变色现象。分子溶剂的缺失也是缺乏热致变色的原因。因此，研究了[HO(CH₂)₂mim]NO₃与水的混合物中的钴(II)溶液，作为一种可用于光强度自动调节和遮光保护的新型绿色介质。发现添加钴(II)后的水体系在所研究的所有体系中是一种迄今为止效率更高、响应性更强的热致变色介质。通过¹H NMR和红外光谱证实了[HO(CH₂)₂mim]NO₃的结构。此外，还研究了不同高级氧化过程（紫外光诱导光解、UV/H₂O₂光解、使用Degussa P25二氧化钛和含7.24%（重量/重量）铁催化剂的二氧化钛的多相光催化）对[HO(CH₂)₂mim]NO₃降解的效率。使用LC-ESI-MS/MS和¹H NMR技术鉴定了光氧化过程中形成的反应中间体。
