Polyhedral Oligomeric Silsesquioxane

Polyhedral oligomeric silsesquioxane (POSS) poly(1-haloacetylene) conjugated networks have been synthesized by Marta Cieplucha, Mateusz Janeta, and Sławomir Szafert at the Faculty of Chemistry, University of Wrocław, as reported in Materials Chemistry Frontiers in 2025. Three octa-functionalized monomers, POSS-C2Cl, POSS-C2Br, and POSS-C2I, were prepared by amide coupling of octa(3-aminopropyl)silsesquioxane with the corresponding 4-(haloethynyl)benzoyl chloride and were shown to undergo thermal polymerization in the solid state without any transition metal catalyst, yielding highly cross-linked poly(1-haloacetylene) networks. This work constitutes the first reported polymerization of a 1-iodoethyne derivative and the first example of 1-haloalkyne polymerization achieved entirely in the absence of metal-based initiators. Synthesis of Octa-Functionalized POSS Haloalkyne Monomers Scheme 1. Synthesis of 1-haloethynyl-functionalized POSS-based monome...

Four novel octa-imine-functionalized polyhedral oligomeric silsesquioxane (POSS) derivatives, designated POSS-6 through POSS-9 , have been reported by Mateusz Janeta and Sławomir Szafert in the Journal of Molecular Structure in 2025. These compounds were obtained by modular Schiff base condensation of octa(3-aminopropyl)silsesquioxane hydrochloride with the appropriate aromatic aldehyde in isolated yields ranging from 84 to 92 percent without chromatographic purification, and their structures were fully established by single-crystal X-ray diffraction. The identity of the peripheral substituent (hydroxyphenyl, bromophenyl, thiophene, or dibenzofuran) was found to govern both the non-covalent interaction topology in the solid state and the thermal behavior, with T 5% decomposition onset temperatures spanning from 305 to 326 °C across the four derivatives. Synthesis of Octa-Imine POSS Derivatives by Schiff Base Condensation All four compounds were obtained by modular Schiff base conde...

The publication titled “Polyhedral oligomeric silsesquioxane difluoroboron complexes as cooperative octo-site catalysts for the photooxidation of sulfides to sulfoxides” by Mateusz Janeta and Sławomir Szafert, published in Inorganic Chemistry Frontiers on April 17, 2025, presents a study on the development of novel metal-free photocatalysts. These catalysts are based on polyhedral oligomeric silsesquioxanes (POSS) functionalized with difluoroboron complexes. Scheme 1. Synthesis of POSS-sal-BF 2 , POSS- tert -BF 2 , and POSS-npht-BF 2 . Isolated yields in parentheses. Key Highlights Catalyst design. The researchers synthesized three new difluoroboron-functionalized POSS complexes, namely POSS- tert -BF 2 , POSS-sal-BF 2 , and POSS-npht-BF 2 , derived from imine-functionalized POSS s. Photocatalytic performance. These complexes demonstrated exceptional efficiency in the aerobic photooxidation of sulfides to sulfoxides, significantly outperforming their silsesquioxane-free counterpa...

Among the large and structurally diverse family of polyhedral oligomeric silsesquioxanes (POSS), octamethylsilsesquioxane — formally designated Si 8 O 12 (CH 3 ) 8 and commonly abbreviated as T8-Me or OMS — occupies a unique position as the structurally simplest and historically most studied member of the cubic T8 series. Its eight methyl groups, one attached to each silicon vertex of the Si 8 O 12 cage, make it the prototype for understanding the geometry, dynamics, spectroscopy, and reactivity of the entire POSS family. Despite its apparent simplicity, T8-Me continues to attract sustained scientific interest across disciplines as diverse as materials science, polymer chemistry, computational chemistry, and ceramic engineering. Structure and Symmetry The molecule consists of a rigid cubic inorganic core composed of eight silicon atoms interconnected by twelve bridging oxygen atoms, forming the Si 8 O 12 framework. Each silicon vertex bears one methyl group directed outward fro...

Bromination of the phenyl rings of octaphenyloctasilsesquioxane proceeds in the ortho position without any Lewis acid catalyst, in contradiction to the regiochemical rules that govern isolated aromatic substrates. The study titled “Why Do the [PhSiO 1.5 ] 8,10,12 Cages Self-Brominate Primarily in the Ortho Position? Modeling Reveals a Strong Cage Influence on the Mechanism” by M. Bahrami, H. Hashemi, X. Ma, J. Kieffer, and R. M. Laine, published in Physical Chemistry Chemical Physics in 2014, accounts for this outcome. The modeling places the bromine molecule 2.7 Å above a cage face, tilted by 30°, with a Br−Br separation of 2.32 Å and an induced dipole moment of 0.33 D, an arrangement that delivers Br δ+ to the ortho carbon. The premise of the present entry, namely that the Si 8 O 12 framework acts as an electron withdrawing center that stabilizes anionic guests and polarizes neutral molecules approaching its faces, is treated in full in the companion entry on the electronic p...

The publication titled “Zinc Imine Polyhedral Oligomeric Silsesquioxane as a Quattro-Site Catalyst for the Synthesis of Cyclic Carbonates from Epoxides and Low-Pressure CO 2 ” by Mateusz Janeta et al., published in Chemistry – A European Journal in 2020, describes the first structurally characterized polyhedral oligomeric silsesquioxane (POSS) that anchors more than one metal cation through its organic side arms. The tetranuclear zinc imine-POSS complex Zn 4 @POSS-1 converts styrene oxide into styrene carbonate with 96% conversion in four hours at only 1 atm of CO 2 , eliminating the high carbon dioxide pressures that normally accompany this transformation. The four zinc centers act cooperatively rather than independently, and the catalyst tolerates five consecutive runs with conversion falling only from 99% to 90%. Polyhedral oligomeric silsesquioxanes are cage-like organosilicon compounds of general formula (RSiO 3/2 ) n whose diameters of 1 to 3 nm make them the smallest exis...

The publication titled “Amphiphilic Azo-Functionalized Polyhedral Oligomeric Silsesquioxane: Synthesis and Photo-Switched Efficient Phase Transfer via Host-Guest Encapsulation” by Bagher Eftekhari-Sis, Nasrin Amirpour, Ali Naderahmadian, Maryam Zirak, Mateusz Janeta and Ghodrat Mahmoudi, published in ChemPlusChem in 2024, presents azo-POSS, a light-switchable amphiphilic polyhedral oligomeric silsesquioxane designed for the selective removal of cationic dyes from water. The compound transfers dyes from the aqueous phase into dichloromethane with encapsulation efficiencies above 94% for methylene blue, 99% for crystal violet and 95% for thymol blue, while remaining essentially inactive toward anionic dyes. Irradiation at 365 nm isomerizes the azobenzene linker and suppresses uptake by as much as 60%, which places the separation process under direct optical control. Synthetic dyes released from textile, paper and plastics manufacturing constitute a significant and expanding category...