Abstract
The urgent needs for photoactive materials in industry drive fast evolution of synthetic procedures in many branches of chemistry, including the chemistry of silsesquioxanes. Here, we disclose an effective protocol for the synthesis of novel double-decker silsesquioxanes decorated with two (styrylethynylphenyl)terpyridine moieties (DDSQ_Ta-b). The synthesis strategy involves a series of silylative and Sonogashira coupling reactions and is reported for the first time. DDSQ_Ta-b were employed as nanocage ligands to promote self-assembly in the presence of transition metals (TM), i.e., Zn2+, Fe2+, and Eu3+ ions, to form one-dimensional (1D) coordination polymeric nanofibers. Additionally, ultraviolet-promoted and reversible E–Z isomerization of the C=C bond within the ligand structures may be exploited to tune their emission properties. These findings render such complexes promising candidates for applications in materials chemistry. This is the first example of 1D coordination polymers bearing DDSQ-based nodes with TM ions.
Highlights
Oligomeric silsesquioxanes (SQs) constitute a broad family of organosilica compounds known for their various architectures from random, ladder, and incompletely condensed to welldefined cages.[1,2] Their uniqueness results from the presence of an inorganic siloxane Si−O−Si core and tunable functional organic coronae, which classify them as hybrid systems
The synthetic protocol applied to obtain DDSQs decorated with twoterpyridine moieties was based on a silylative coupling reaction followed by Sonogashira coupling
We found that the Td5% temperatures determined for DDSQa-b and DDSQ_Ta-b as well as residues after the measurements were higher for experiments performed in the inert atmosphere
Summary
Oligomeric silsesquioxanes (SQs) constitute a broad family of organosilica compounds known for their various architectures from random, ladder, and incompletely condensed to welldefined cages.[1,2] Their uniqueness results from the presence of an inorganic siloxane Si−O−Si core and tunable functional organic coronae, which classify them as hybrid systems. For the double-decker-based coordination systems, the number of reports concerning their synthesis, characterization, and application is quite limited.[42,43] Studies by Yam et al refer to the synthesis of “closed” DDSQ structures bearing two terpyridine (Tpy)-functionalized substituents with the consequent possible presence of stereoisomers and their further use in the formation of PtIIbased coordination systems.[43] The obtained molecular compounds exhibited interesting self-association via Pt···Pt interactions. 1H, 13C, and 29Si nuclear magnetic resonance (NMR) measurements for DDSQa-b were performed on Bruker 400 MHz or 300 MHz spectrometers using CDCl3 as a solvent. All nonhydrogen atoms were refined anisotropically, and all hydrogen atoms were placed in the calculated positions and refined as a “riding model” with the isotropic displacement parameters set at 1.2 times the Ueq value for appropriate nonhydrogen atoms
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