{[Ni_4(nic)_8(H_2O)_2]·3H_2O}_∞(Hnic=烟酸)配位聚合物的合成、晶体结构和磁性研究

Synthesis,crystal structure and magnetic properties of {[Ni_4(nic)_8(H_2O)_2]·3H_2O}_∞(Hnic=nicotinic acid)

将硝酸镍与烟酰胺混合,在EDTA存在和180℃温度下,水热反应,得到配合物{[N i4(nic)8(H2O)2].3H2O}∞(Hnic=烟酸).通过EA、IR和TG对其进行了表征,单晶X射线衍射对其结构进行了确证.晶体数据:monoclinic,space group P2(1)witha=10.7566(8),b=19.5438(15),c=13.7801(10),β=104.4860(3),Mr=1301.74,V=2804.8(4)3,Z=2,μ(MoKα)=1.405 mm-1,F(000)=1332,R=0.0625,wR=0.1541.结构分析表明:配合物是由四核[N i4(nic)8(H2O)2]单元,3个结晶水分子构成的三维网状{[N i4(nic)8(H2O)2].3H2O}∞配位聚合物.其中4个烟酸采用μ3-nic-N,O,O的三齿桥联配位方式,另外4个烟酸采用μ2-nic-N,O的双齿桥联配位方式,所有的N i原子都处在六配位的畸变八面体几何构型环境.TG结果表明:配合物具有很好的热稳定性.磁性研究表明:配合物中的N i2+与N i2+之间存在反铁磁性耦合,在2.0～300 K温度范围内,磁化率很好地遵循Curie-W eiss定律,拟合得C=5.24 cm3.K.mol-1,θ=-2.30 K.

A complex,{[Ni4（nic）8（H2O）2]·3H2O}∞,（Hnic=nicotinic acid）,has been synthesized through the Ni2＋ salt reacting with nicotinamide under hydrothermal conditions and characterized by EA,IR,TG and single crystal x-ray diffraction.Crystal data：monoclinic,space group P2（1） with a=10.7566（8）,b=19.5438（15）,c=13.7801（10）,β=104.4860（3）,Mr=1301.74,V=2804.8（4）3,Z=2,μ（MoKα）=1.405 mm-1,F（000）=1332,R=0.0625 and wR=0.1541.X-ray single-crystal diffraction shows that each Ni（Ⅱ） atom is coordinated by six oxygen or nitrogen atoms in a octahedral geometry.The nicotinic anion can function in two types（μ3-nic-N,O,O as tridentate mode and μ2-nic-N,O as bidentate mode） of coordination fashion to bridge nickel（Ⅱ） atoms.Spin-orbit coupling and weak antiferromagnetic interaction between the adjacent Ni atoms in the 3D solid state were observed from the magnetic experiments.The complexes obey the Curie-Weiss law with Weiss constant C=5.24 cm3·K·mo1-1,θ=-2.30 K in the high-temperature region.