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Structures and phase transitions in neat 4,4′-di-tert-butyl-2,2′-bipyridyl and in its molecular complexes with either bromanilic or iodanilic acid
CrystEngComm ( IF 3.1 ) Pub Date : 2017-10-31 00:00:00 , DOI: 10.1039/c7ce01481c
M. Rok 1, 2, 3, 4 , P. Szklarz 1, 2, 3, 4 , M. Moskwa 1, 2, 3, 4 , M. Kijewska 1, 2, 3, 4 , J. Baran 4, 5, 6, 7 , G. Bator 1, 2, 3, 4 , W. Medycki 4, 8, 9, 10 , M. Zamponi 11, 12, 13, 14
Affiliation  

Using the DSC method, structural phase transitions have been found at 165 and 219 K for 4,4′-di-tert-butyl-2,2′-bipyridyl (dtBBP), whereas for its complex with iodanilic acid (dtBBP·IA), its phase transition is at 331 K. For the other molecular complex described (with bromanilic acid, dtBBP·BRA), no phase transitions have been observed between the liquid nitrogen temperature and the temperature of crystal decomposition. The crystal structures of the neat dtBBP have been determined at 130, 190 and 250 K, whereas for its molecular complex with bromanilic acid (BRA) is determined at 150 K and for its complex with iodanilic acid (IA) determined at 293 and 345 K. The crystal structure of neat dtBBP is characterized by layers of molecules, which are grouped by their t-butyls. The structures of dtBBP·BRA and dtBBP·IA are analogous to one another and consist of infinite chains of alternating acid and base molecules linked by hydrogen bonds. On the basis of the structural, dielectric and spectroscopic results (infrared and Raman), the mechanisms of the phase transitions have been proposed for dtBBP and dtBBP·IA. The 1H NMR spin–lattice relaxation times for all compounds under study, as well as the second moment for the neat dtBBP in a wide temperature, have been measured. The anomalies in the temperature dependent infrared spectra together with the NMR results support the supposition that for dtBBP the dynamics of tert-butyl groups is responsible for the mechanism of the phase transitions found. The dynamics of the molecules in the crystals presented is related to the rotation both of the methyl and tert-butyl groups.

中文翻译:

纯净的4,4'-二叔丁基-2,2'-联吡啶及其与溴酸或碘酸的分子复合物中的结构和相变

使用DSC方法,发现在4,4'-二叔丁基-2,2'-联吡啶(dtBBP)在165和219 K处发生结构相变,而与碘酸(dtBBP·IA)形成络合物,其相变为331K。对于所述的其他分子配合物(使用溴酸,dtBBP·BRA),在液氮温度和晶体分解温度之间未观察到相变。dtBBP的晶体结构已在130、190和250 K下测定,而与溴酸(BRA)的分子络合物在150 K下测定,与碘酸(IA)的络合物在293和345 K下测定。 。纯净的dtBBP的晶体结构其特征在于分子的层,其由它们的丁基分组。的结构dtBBP·BRAdtBBP·IA类似于彼此,并且由通过氢键连接的交替的酸和碱分子的无限链。根据结构,介电和光谱结果(红外和拉曼光谱),提出了dtBBPdtBBP·IA的相变机理。在1已测量了所有正在研究的化合物的H NMR自旋-晶格弛豫时间,以及在宽温度下纯dtBBP的第二矩。温度相关的红外光谱的异常以及NMR结果支持以下假设:对于dtBBP丁基的动力学是所发现相变的机理。所呈现的晶体中分子的动力学与甲基和丁基的旋转有关。
更新日期:2017-11-20
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