Crystal structures and magnetic properties of acid–base molecular complexes, (p-pyridyl nitronylnitroxide)2X (X=hydroquinone, fumaric acid and squaric acid)
Crystal structures and magnetic properties of acid–base molecular complexes, (p-pyridyl nitronylnitroxide)2X (X=hydroquinone, fumaric acid and squaric acid)
复制标题
酸碱分子配合物（对吡啶硝基硝基氮氧化物）2X（X=氢醌、富马酸和方酸）的晶体结构和磁性
DOI：
10.1039/a708121i
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发表时间：
1998
影响因子：
--
通讯作者：
T. Inabe
中科院分区：
文献类型：
--
作者：
T. Otsuka;T. Okuno;K. Awaga;T. Inabe
2-（4-吡啶基）-4，4，5，5-四甲基-4，5-二氢-1H-咪唑-1-氧基-3-N-氧化物（或对吡啶基硝酰基氮氧化物，简称p-PYNN）与三种二元有机酸X [=富马酸（FA）、方酸（SA）和对苯二酚（HQ）]反应，生成（p-PYNN）2X型氢键配合物。在它们的晶体中，有机酸选择性地与p-PYNN中的两种氢键接受位点形成氢键：（a）NO基团中的氧原子和（B）吡啶环上的氮原子。p-PYNN 2 HQ晶体属于单斜晶系P21 /n空间群。HQ分子桥接两个p-PYNN，并选择p-PYNN中的位点（a）作为氢键受体[即（p-PYNN）NOHO（HQ）OHON（p-PYNN）]。p-PYNN 2 FA属于单斜晶系P21 /n空间群。FA分子通过分子间氢键将两个p-PYNN分子连接到位点（B）[（p-PYNN）NHO（FA）OHN（p-PYNN）]。p-PYNN和SA的2：1化合物与晶体溶剂1，4-二氧六环（缩写为diox）一起结晶，形成p-PYNN 2 SAdiox式。晶体属于三斜晶系P空间群。SA分子占据两个p-PYNN之间的空间，与位点（B）接触，就像FA在p-PYNN 2 FA晶体中所做的那样。然而，SA的结构表明它是一种二价阴离子，其中缺少两个质子，因此氢键是离子[（p-PYNN）NH+ O-（SA）O-H +N（p-PYNN）]。氢键的选择性和特征可以定性地理解为氢键能中静电和电荷转移项之间的竞争，这取决于有机酸的酸性和p-PYNN中两个位点的质子接受能力。这三种分子化合物表现出不同的反铁磁性质，这取决于p-PYNN在晶体中的相互排列。根据McConnell的自旋极化机制解释了分子间的相互作用。
The reactions of 2-(4-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl 3-N-oxide (or p-pyridyl nitronylnitroxide, abbreviated as p-PYNN) with the three dibasic organic acids, X [=fumaric acid (FA), squaric acid (SA) and hydroquinone (HQ)], result in the formation of hydrogen-bonding complexes of ( p-PYNN)2 X composition. In their crystals, the organic acids make selective hydrogen bonds to the two kinds of hydrogen-bond accepting sites in p-PYNN; (a) the oxygen atom in the NO group and (b) the nitrogen atom of the pyridyl ring. p-PYNN2HQ crystallizes in the monoclinic P21 /n space group. The HQ molecule bridges two p-PYNNs, and selects site (a) in p-PYNN as the hydrogen bond acceptor [i.e. ( p-PYNN)NOHO(HQ)OHON( p-PYNN)]. p-PYNN2 FA crystallizes in the monoclinic P21 /n space group. The FA molecule connects two p-PYNN molecules with an intermolecular hydrogen bond to site (b) [( p-PYNN)NHO(FA)OHN( p-PYNN)]. The 2:1 compound of p-PYNN and SA crystallizes with the crystal solvent, 1,4-dioxane (abbreviated as diox), in the formula for p-PYNN2 SAdiox. The crystal belongs to the triclinic P space group. The SA molecule occupies the space between two p-PYNNs, making contact with site (b), as FA does in the p-PYNN2 FA crystal. However the structure of SA indicates that it is a dianion in which the two protons are missing and, thus, the hydrogen bond is ionic [( p-PYNN)NH+ O–(SA)O– H+N( p-PYNN)]. The selectivity and features of the hydrogen bonds can be qualitatively understood in terms of competition between the electrostatic and charge-transfer terms in the hydrogen-bonding energy, which is governed by the acidity of the organic acids and the proton accepting abilities of the two sites in p-PYNN. The three molecular compounds exhibited different antiferromagnetic properties, which depend on the mutual arrangement of p-PYNN in the crystals. The intermolecular interactions were interpreted based on the McConnell’s spin polarization mechanism.