论文部分内容阅读
近年来,由于在诸如催化分离、光化学以及生物技术等领域具有潜在的应用前景,金属膦酸化合物得到了广泛的关注.在分子磁体研究领域,尽管膦酸基团只能传递很弱的磁相互作用,但是很多膦酸簇合物以及聚合物均表现出有趣的磁性质,如单分子磁体、自旋倾斜、亚铁磁体、铁磁体以及变磁体行为.最近,毛江高和Dunbar课题组报道了化合物[Co(H2L)(H2O)]∞[L=4-Me-C6H4-CH2N(CPO3H2)2]的磁性,该化合物中各向异性的钴离子通过μ-O(P)和O-P-O双桥连接成链,显示出单链磁体行为以及自旋倾斜现象.另外一个例子是由Sessoli课题组报道的[Mn(TPP)O2PHPh]-H2O(TPP=meso-tetraphenylporphyrin),其中三价锰离子由O-P-O单元连接也形成一维结构,该化合物同样表现出有意义的单链磁体行为.因此,从磁学观点上看,具有一维链结构的金属膦酸化合物是相当有趣的.为了进一步理解这类化合物的磁性与结构的关系,制备新的此类链状化合物是很有必要的.在本文中,我们报道了三个新的同构化合物M(pnaH)(H2O)3·H2O[M=Co(II)(1),Ni(II)(2),Zn(II)(3)](pnaH3=6-phosphonic nicotinic acid).化合物1是单斜晶系P21/n空间群,不对称单元含有一个钴离子,一个负二价6-膦酸烟酸离子,三个配位水分子,一个结晶水分子.钴离子具有扭曲八面体配位环境,其六个配位点分别被吡啶氮原子、膦酸氧原子以及三个水分子中的氧原子所占据,其中Co-O(N)键长为0.2053(3)-0.2203(3)nm.6-膦酸烟酸作为三齿配体与钴离子配位,其羧酸氧原子是质子化的不参与配位.结果,{CoO5N}八面体通过{PO3C}四面体以共角方式连接,从而在沿着b方向上形成21螺旋链,以O-P-O单元连接的两个钴离子的距离是0.4889nm.这些链结构再通过复杂的氢键作用形成超分子结构.热重分析显示,三个化合物具有相似的热稳定性,在200℃之前都失去了配位和结晶水分子并保持一定的晶形,然后在300℃以后伴随着有机配体分解结构发生了坍塌.研究了化合物1和2的磁性,发现金属中心之间都存在反铁磁性相互作用,在1.8K以上主要表现为顺磁性的行为,对化合物2的磁性数据进行拟合得到参数g=2.21,J=-0.54cm-1.对化合物1脱水后的产物也进行了磁性测试,发现它在低温下表现出变磁性质.
In recent years, metal phosphonic acid compounds have attracted a great deal of attention due to their potential applications in such fields as catalysis, photochemistry and biotechnology.In the field of molecular magnetics, although phosphonic acid groups can only transmit weak magnetic interactions However, many phosphonic acid clusters and polymers exhibit interesting magnetic properties such as single-molecule magnets, spin-tilt, ferrimagnetic, ferromagnetic, and demagnetizing magnets. Recently, Mao Jiangang and Dunbar The magnetic properties of the compound [Co (H2L) (H2O)] ∞ [L = 4-Me-C6H4-CH2N (CPO3H2) 2] Linked into a chain showing single-stranded magnet behavior and spin-tilt phenomena.Another example is the [Mn (TPP) O2PHPh] -H2O (TPP = meso-tetraphenylporphyrin) reported by the Sessoli Task Group, in which the trivalent manganese ions are represented by OPO The unit connections also form a one-dimensional structure that also exhibits a meaningful single-stranded magnet behavior Therefore, from the magnetic point of view, metal phosphonic acid compounds with one-dimensional chain structures are quite interesting.To further understand this type of The magnetic and chemical structure of the compound It is necessary to prepare a new class of these chain compounds.In this paper, we report three novel isomorphic compounds M (pnaH) (H2O) 3 · H2O [M = Co (II) (1), Ni (II) (2), Zn (II) (3)] (pnaH3 = 6-phosphonic nicotinic acid) .Compound 1 is a monoclinic P21 / n space group and the asymmetric unit contains one cobalt ion, 6-phosphonic acid nicotinic acid ion, three coordination water molecules and one crystal water molecule. The cobalt ion has a distorted octahedron coordination environment, and the six coordination points thereof are respectively substituted by a pyridine nitrogen atom, a phosphonic acid oxygen atom and three (3) -0.2203 (3) nm.6-phosphonic acid nicotinic acid as a tridentate ligand with the cobalt ion coordination, the carboxylic acid As a result, the {CoO5N} octahedra is connected by a {PO3C} tetrahedron in a diagonal manner to form two cobalt chains connected in the OPO unit with a 21-helical chain in the b direction The distance of the ions is 0.4889 nm.These chains then form supramolecular structures through complex hydrogen bonding.The thermogravimetric analysis shows that the three compounds have similar thermal stability and lose coordination and crystal water molecules before 200 ℃ and And then collapsed with the decomposition of the organic ligands after 300 ° C. The magnetic properties of the compounds 1 and 2 were studied and the antiferromagnetic interactions between the metal centers were found. Above 1.8 K, Paramagnetic behavior was fitted to the magnetic data of compound 2 to obtain the parameter g = 2.21, J = -0.54 cm-1. The dehydrated product of compound 1 was also magnetically tested and found to exhibit magnetism at low temperatures nature.