Influence of the Anion on the Structure of Bis(methylthio)methane Supramolecular Coordination Complexes

A series of coordination networks has been synthesized by the self-assembly of the small bis(methylthio)methane
building block and AgX (X = NO3- (1), ClO4- (2, 3), p-TsO- (4), CF3COO- (5), CF3CF2CF2COO- (6), CF3SO3- (7), C6H5COO-
(8), CH3SO3- (9), and HOOCCF2CF2COO- (10)) in order to rationalize the effect of the size of the anions and the ligands upon the
structure adopted by the supramolecular coordination network. In complexes 1−7, each silver(I) is coordinated with sulfur atoms
from three different ligands. They form very similar two-dimensional solid-state organizations. The structures consist of layers,
made up of Ag and bis(methylthio)methane ligands only, in which the anions complete the tetrahedral coordination of the silver
atoms. Upon closer inspection, the neutral 2D networks may be sorted into two distinct classes. Group 1 incorporates the smallest
anions, NO3- and ClO4-, whereas the more elongated anions, p-TsO-, CF3COO-, CF3CF2CF2COO-, and CF3SO3-, are found in
group 2. The main difference between these groups is in the organization of the neutral layers. In group 1, the repeat unit consists
of a large 14-membered metallomacrocycle, whereas in group 2, the metallomacrocycle consists of 10-membered rings. The two
polymorphs of the perchlorate complexes are structurally comparable. Dimeric units are the basis for the other three complexes. In
benzoate 8, the dimers are formed with two anions. They are linked by ligand molecules to form a 1D polymeric chain that adopts
a distorted hexagonal packing. The silver atoms have a distorted triangular bipyramidal coordination and the Ag···Ag distance is
2.911 Å. In complex 9, two ligands each bridge a pair of silver atoms to form a dimer (Ag···Ag = 3.243 Å). A neutral 1D coordination
polymer is obtained when anions connect, in a dibridging mode, the silver atoms of adjacent dimers [Ag(CH3SCH2SCH3)]2. Weak
hydrogen interactions between chains result in a 3D network. The silver coordination is triangular bipyramidal. Complex 10 is also
a 1D coordination polymer with a centrosymmetric dimer. Two ligands and two anions are coordinated to the silver atoms. The
Ag···Ag contact is 3.067 Å. A 1D coordination polymer is obtained through H-bonding between carboxylate groups. The
stoichiometries of the complexes are independent of the initial metal-to-ligand ratios and are not influenced by the solvent of
recrystallization.

本研究通过双(甲硫基)甲烷（bis(methylthio)methane）小分子构筑基元与AgX（X = NO3⁻(1)、ClO4⁻(2, 3)、对甲苯磺酸根(p-TsO⁻)(4)、三氟乙酸根(CF3COO⁻)(5)、全氟丁酸根(CF3CF2CF2COO⁻)(6)、三氟甲磺酸根(CF3SO3⁻)(7)、苯甲酸根(C6H5COO⁻)(8)、甲磺酸根(CH3SO3⁻)(9)以及二氟丁二酸根(HOOCCF2CF2COO⁻)(10))进行自组装，合成了一系列配位网络，以阐明阴离子与配体的尺寸对超分子配位网络（supramolecular coordination network）所采用结构的影响。在配合物1~7中，每个银(I)原子均与来自三个不同配体的硫原子配位，形成结构极为相似的二维固态组装体。该类结构仅由Ag与双(甲硫基)甲烷配体构成层状骨架，阴离子则用以完成银原子的四面体配位。进一步研究表明，该类中性二维网络可分为两类不同组别。第1组包含尺寸最小的阴离子：NO3⁻与ClO4⁻；而第2组则包含更为伸长的阴离子，包括p-TsO⁻、CF3COO⁻、CF3CF2CF2COO⁻与CF3SO3⁻。两类组别的核心差异在于中性层的组装方式：第1组的重复单元为大型14元金属大环（metallomacrocycle），而第2组的金属大环则为10元环。高氯酸根配合物的两种多晶型物结构具有可比性。二聚体单元为其余三种配合物的结构基础。在苯甲酸根配合物8中，二聚体由两个阴离子构成，并通过配体分子连接形成一维聚合物链，该链呈现扭曲的六方堆积。银原子具有扭曲的三角双锥配位，Ag···Ag间距为2.911 Å。在配合物9中，两个配体各自桥联一对银原子以形成二聚体（Ag···Ag = 3.243 Å）。当阴离子以双桥联模式连接相邻二聚体[Ag(CH3SCH2SCH3)]₂中的银原子时，可得到中性一维配位聚合物。链之间存在弱氢键相互作用，最终形成三维网络。银原子的配位模式为三角双锥。配合物10同样为具有中心对称二聚体的一维配位聚合物，两个配体与两个阴离子配位至银原子，Ag···Ag接触距离为3.067 Å。通过羧酸根基团间的氢键作用可得到一维配位聚合物。该系列配合物的化学计量比与初始金属与配体的投料比无关，且不受重结晶溶剂的影响。