(Pyrazolato)gold Complexes Showing Room-Temperature Columnar Mesophases. Synthesis, Properties, and Structural Characterization

Mesogenic (pyrazolato)gold complexes of formula
[Au(pz)]3 (pz =
3,5-bis(3‘,4‘-di-n-decyloxyphenyl)pyrazole
(1),
3-(3‘,4‘,5‘-tri-n-decyloxyphenyl)-5-(3‘‘,4‘‘-di-n-decyloxyphenyl)pyrazole
(2),
3-(2‘,3‘,4‘-tri-n-decyloxyphenyl)-5-(3‘‘,4‘‘,5‘‘-tri-n-decyloxyphenyl)pyrazole
(3),
3,5-bis(3‘,4‘,5‘-tri-n-decyloxyphenyl)pyrazole
(4)) have been prepared
by reaction of the potassium salts of the nonmesogenic pyrazolate
ligands with [AuCl(tht)] (tht = tetrahydrothiophene) in a 1:1 molar ratio. All these compounds show
columnar mesophases that remain stable, at room
temperature, for long periods of time. The formation of isomers
for the nonsymmetrical derivativesdetected by
spectroscopic studiesare suggested to be responsible for the subtle
changes observed in the transition temperatures.
Powder X-ray diffraction measurements show clearly that the
supramolecular columnar arrangement appears in
the crystalline solids as well as in the mesomorphic phase. An
analogue of the mesogenic trinuclear complexes
1−4, having a methoxy group at the
phenyl substituents of the pyrazolate ligands,
[Au{3,5-(MeOPh)2Pz}]3
(5),
has been synthesized and characterized by an X-ray single-crystal
diffraction experiment. The molecular structure
of 5 is based on a nine-membered metallacycle core. The
whole molecule exhibits a rough planarity that favors
a crystalline structure formed from columnar arrangements of trinuclear
complexes. A simple and clear relationship
could be established between the solid-state crystal structure of
5 and the X-ray-deduced structure of the
mesophases.

通式为[Au(pz)]₃的介晶（mesogenic）(吡唑基)金配合物，其中配体pz分别为：3,5-双(3',4'-二正癸氧基苯基)吡唑（1）、3-(3',4',5'-三正癸氧基苯基)-5-(3'',4''-二正癸氧基苯基)吡唑（2）、3-(2',3',4'-三正癸氧基苯基)-5-(3'',4'',5''-三正癸氧基苯基)吡唑（3）以及3,5-双(3',4',5'-三正癸氧基苯基)吡唑（4）。该类配合物通过非介晶吡唑基配体的钾盐与[AuCl(tht)]（tht=四氢噻吩(tetrahydrothiophene)）以1:1摩尔比反应制备得到。

所有上述配合物均呈现柱状介晶相，且该介晶相可在室温下长期保持稳定。经光谱研究检测发现，非对称衍生物存在异构体，研究者认为此类异构体的形成是造成转变温度出现细微变化的原因。

粉末X射线衍射测试结果清晰显示，超分子柱状排列不仅存在于晶体固体中，也存在于介晶相内。

研究者还合成了介晶三核配合物1~4的类似物——吡唑基配体的苯基取代基带有甲氧基的[Au{3,5-(MeOPh)₂Pz}]₃（5），并通过单晶X射线衍射对其进行了表征。配合物5的分子结构以九元金属环核心为骨架，整体分子呈现近似平面性，这有利于形成由三核配合物柱状排列构成的晶体结构。

我们可在配合物5的固态晶体结构与通过X射线解析得到的介晶相结构之间建立简洁清晰的对应关系。