3 research outputs found
Exploring Cagelike Silsesquioxane Building Blocks for the Design of Heterometallic Cu4/M4Architectures
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 Cu4Cs4and Cu4Rb4coordination polymers with the common formula [(PhSiO1.5)12(CuO)4(AO0.5)4(Solv)x]n路nSolv (A is Cs or Rb; Solv refers to ligands and/or solvate molecules including H2O, 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 Cu4Cs4- and Cu4Rb4-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路路路蟺(Rb路路路蟺) 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 C5-C8cycloalkanes. This study extends the structural types of heterometallic silsesquioxane cages that can be efficiently applied to the design of functional coordination polymers. 漏 2022 American Chemical Society. All rights reserved
Exploring Cagelike Silsesquioxane Building Blocks for the Design of Heterometallic Cu<sub>4</sub>/M<sub>4</sub>Architectures
GLONASS
The Global鈥檔aya Navigatsionnaya Sputnikova Sistema
(GLONASS) is a global navigation satellite
system developed by the Russian Federation.
Similar to its US counterpart, the NAVSTAR global
positioning system (GPS), GLONASS provides dualfrequency
L-band navigation signals for civil and
military navigation. Initiated in the 1980s, the
system first achieved its full operational capability
in 1995. Following a temporary degradation,
the nominal constellation of 24 satellites was ultimately
reestablished in 2011 and the system has
been in continued service since then. This chapter
describes the architecture and operations of
GLONASS and discusses its current performance. In
addition, the planned evolution of the space and
ground segment are outlined