Exploring Cagelike Silsesquioxane Building Blocks for the Design of Heterometallic Cu₄/M₄Architectures

Abstract

Within the sweeping research on the design of new coordination polymers and related metal−organic architectures, the use of silsesquioxane derivatives as important organosilicon building blocks has been poorly explored, despite a number of unique structural and functional characteristics of the resulting products. The present study thus describes an extended series (eight examples) of heterometallic Cu 4 Cs 4 and Cu 4 Rb 4 coordination polymers with the common formula [(PhSiO 1.5 ) 12 (CuO) 4 -(AO 0.5 ) 4 (Solv) x ] n •nSolv (A is Cs or Rb; Solv refers to ligands and/ or solvate molecules including H 2 O, EtOH, BuOH, DMF, and DMSO in various combinations), which are based on cagelike coppersilsesquioxanes as nontrivial secondary building units. The concept of supramolecular design was implemented in a straightforward way by the assembly of coppersilsesquioxane cages using large and coordination-versatile cesium or rubidium cations. The structures of all products were established by single-crystal X-ray diffraction studies mainly using synchrotron radiation. The resulting Cu 4 Cs 4 -and Cu 4 Rb 4 -silsesquioxanes exhibit an extracage location of the alkali-metal cations, which enables the interconnectivity of neighboring cages into 1D, 2D, or 3D coordination polymer architectures. The unique feature of such architectures is a realization of metallocene Cs•••π (Rb•••π) joints, providing tightly connected nonporous coordination polymers. A topological classification of cages and coordination polymer networks was performed. Some of the obtained compounds also represent the first examples of Rb-containing silsesquioxanes. The selected products were also tested as homogeneous catalysts in the oxidation and hydrocarboxylation of C 5 −C 8 cycloalkanes. This study extends the structural types of heterometallic silsesquioxane cages that can be efficiently applied to the design of functional coordination polymers.

Cagelike Octacopper Methylsilsesquioxanes: Self-Assembly in the Focus of Alkaline Metal Ion Influence—Synthesis, Structure, and Catalytic Activity

“…It is known that variations of the nature of alkaline metal ions strongly influence the structural features of phenylsurrounded CLMSs, especially in the context of supramolecular aggregation observed for large-sized ions (K, Rb, Cs) [ 16 , 23 , 25 , 47 , 60 ]. For the method of synthesis of methylsurrounded Cu-CLMSs, a universal approach that included alkaline hydrolysis [ 61 , 62 , 63 ] of MeSi(OMe) 3 assisted by the action of corresponding hydroxide MOH (M = Na, K, Rb, or Cs), was chosen.…”

“…The same could be said regarding screening ethanol solvate and coordinating rubidium ions. This also prevents the formation of the coordination polymer structure despite the significant coordinative potential of rubidium centers towards siloxanes, which could be fruitful in supramolecular assembly [ 25 , 68 , 69 , 70 ].…”

“…The latter comprises approaches to molecular magnets (including behaviors of single-molecule magnets or spin glass types) [ 12 , 13 , 14 , 15 , 16 , 17 , 18 ] and objects with photophysical properties (including the first example of a lanthanide-based luminescent thermometer) [ 19 , 20 , 21 , 22 ]. In the context of material science, CLMSs were successfully applied for the versatile design of functional MOFs and coordination polymers [ 23 , 24 , 25 , 26 ], anodes [ 27 , 28 ], biomedical agents [ 29 ], and fire retardants [ 30 , 31 , 32 , 33 , 34 , 35 ]. Numerous reviews summarize the effectiveness of CLMS in various catalyzed reactions, including oxidative C–H bond activations [ 36 , 37 , 38 , 39 , 40 , 41 , 42 ].…”

A Novel Family of Cage-like (CuLi, CuNa, CuK)-phenylsilsesquioxane Complexes with 8-Hydroxyquinoline Ligands: Synthesis, Structure, and Catalytic Activity

“…The inter-cage connections are realized via the metallocene K·π-Ph joints between the potassium center of one cage and the phenyl group of the silicon atom, which belongs to a neighboring cage ( Figure 5 , top). Only two similar observations could be cited in this context:( i ) Na·π-Ph joints in discrete Mn,Na CLMS [ 95 ] and ( ii ) Cs(Rb)·π-Ph joints in CuCs(Rb) CLMS coordination polymers [ 96 ]. Interestingly, each cage complex in the supramolecular structure of 5 interacts with neighbors via both two potassium centers and two phenyl groups, thus forming an unusual 2D coordination polymer structure ( Figure 5 , bottom).…”

Hybrid Silsesquioxane/Benzoate Cu7-Complexes: Synthesis, Unique Cage Structure, and Catalytic Activity

“…The latter includes the design of molecular magnets (including single-molecule magnets and spin glasses) [ 12 , 13 , 14 , 15 , 16 , 17 , 18 ] and objects with photophysical properties (including the first example of a CLMS-based luminescent thermometer) [ 19 , 20 , 21 , 22 ]. For materials science, CLMSs were successfully applied for the production of functional coordination polymers [ 23 , 24 , 25 , 26 ], anode materials [ 27 , 28 ], biocompatible agents [ 29 ], and flame retardants [ 30 ]. Another important area of CLMSs investigations concerns their catalytic properties towards numerous important industrial processes [ 31 , 32 , 33 , 34 , 35 , 36 ].…”