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It is highly desirable to develop facile methods to improve the processability of porous materials for industrial applications. Herein, the preparation of a novel near‐infrared emitting hybrid aerogel (PCS‐CA) is reported by physically blending a porous material with chitosan. The applied porous material (PCS‐CZ‐O‐DCM) is obtained from a near‐infrared emission semiconductor compound (CZ‐O‐DCM) and octavinylsilsesquioxane (OVS). PCS‐CZ‐O‐DCM can detect tetracycline hydrochloride selectively and rapidly in various solution with an extremely low detection limit of 0.29 µm for fluorescence quenching. It also exhibits an outstanding sunlight‐driven photodegradation activity for antibiotics even in the absence of additional oxidation agents or pH control. PCS‐CA also performs better than PCS‐CZ‐O‐DCM powder. A PCS‐CA‐based glass device is further fabricated, which enables a larger amount of water purification of antibiotics by a continuous flow‐through system by light‐driven degradation. By blending with a soft polymer matrix, improved processability can be applied to insoluble porous materials. As a result, a novel functional devices can be realized which provides a new way to apply insoluble porous materials. [ABSTRACT FROM AUTHOR]

Keywords: antibiotics; near-infrared emission aerogels; photocatalysts; processability; sensors EN antibiotics near-infrared emission aerogels photocatalysts processability sensors 1 1 1 09/22/23 20230919 NES 230919 B Near-Infrared Emission Aerogels b In article number 2214875, Masafumi Unno, Hongzhi Liu, and Qingzheng Wang propose, a novel near-infrared emitting hybrid aerogel by physically blending silsesquioxane-based porous polymer with chitosan. Dual-Function Near-Infrared Emitting Aerogel-Based Device for Detection and Sunlight-Driven Photodegradation of Antibiotics: Realizing the Processability of Silsesquioxane-Based Fluorescent Porous Materials (Adv. Funct. The aerogel- based device demonstrates a M-level detection limit and desirable selectivity toward tetracycline hydrochloride, and sunlight-driven photodegradation activity for antibiotics. [Extracted from the article]

ABSTRACT The facile synthesis of all- cis-tetrasiloxycyclotetrasiloxanes (extended cyclic siloxanes) [ i-BuSi(OSiHMe2)O]4 1, [PhSi(OSiHMe2)O]4 2, and [CH2 = CHSi(OSiHMe2)O]4 3 was accomplished via sodium or potassium silanolates from respective trialkoxysilanes. The treatment of 1 or 2 with m-chloroperoxybenzoic acid afforded respective extended cyclic silanols [ i-BuSi(OSiMe2OH)O]4 4 and [PhSi(OSiMe2OH)O]4 5. The structures of 4 and 5 were unequivocally established by X-ray crystallography. Among these new compounds, compound 3 possesses both vinyl and hydrosilyl groups in the molecule, thus this could serve as a potential monomer of well-defined cage silsesquioxanes. Extended cyclic silanols 4 and 5 contain four silanol moieties in the same direction, and application of host molecules or building units of cage silsesquioxanes is expected. [ABSTRACT FROM AUTHOR]

Herein, we report synthetic strategies for the development of a bifunctional Janus T4 tetrapod (Janus ring), in which the orthogonal silsesquioxane and organic faces are independently functionalized. An all-cis T4 tetrasilanolate was functionalized to introduce thiol moieties on the silsesquioxane face and naphthyl groups on the organic face to introduce luminescent and self-organization properties. The stepwise synthesis conditions required to prepare such perfectly defined oligomers via a suite of well-defined intermediates and to avoid polymerization or reactions over all eight positions of the tetrapod are explored via 29Si, 13C and 1H NMR, FTIR and TOF-ESI mass spectroscopy. To the best of our knowledge, this is one of the few reports of Janus T4 tetrapods, with different functional groups located on both faces of the molecule, thus expanding the potential range of applications for these versatile precursors. [ABSTRACT FROM AUTHOR]

The thermal reaction of an octathexyloctasilacubane, R8Si8 (R = thexyl: 1,1,2-trimethypropyl), with sulfur in a sealed tube gave a sulfur-inserted novel compound, R8Si8S, together with an unexpected ring-opening compound. The reaction with selenium in a similar condition gave a ring-opening compound exclusively. With tellurium, the thermal reaction of the octasilacubane resulted in the formation of a tellurium-inserted compound (R8Si8Te), which was decomposed in solution to give the octasilacubane and tellurium. [ABSTRACT FROM AUTHOR]

Abstract: Three new pentacyclic laddersiloxanes were prepared by a new method utilizing single stereoisomer of disiloxanediol as a growing unit. Thus, one diastereomer of disiloxanediol, (RS)–[i-PrPhSi(OH)]2O was isolated and treated with tetrachlorocyclotetrasiloxane, resulting in the formation of tricyclic laddersiloxanes with cis-Ph groups at terminals. All of the obtained isomers could be transformed into pentacyclic laddersiloxanes by dephenylchlorination followed by the reaction with (RS)–[i-PrPhSi(OH)]2O. The structures of new tricyclic and pentacyclic laddersiloxanes were determined by X-ray crystallography. The thermogravity properties of laddersiloxanes depending on the molecular weight and structures were summarized. [Copyright &y& Elsevier]

Cocrystallization of all-cis-tetraisopropylcyclotetrasiloxanetetraol and diisopropylsilanediol gave single crystals, which were proved to have a nano-size tube-like aggregate structure. Six molecules of the cyclic tetraol and four molecules of the diol form an asymmetric unit by means of hydrogen bonding. The structure and properties of the aggregates are discussed in detail, and also the possibility of solid-state synthesis of siloxanes is described. [ABSTRACT FROM AUTHOR]

The first synthesis of all four stereoisomers of 1 ,3,5,7-tetrahydroxy-1,3,5,7-tetraisopropylcyclotetrasiloxane, [i-PrSiO(OH)]4 (all-trans-, cis-cis-trans-, cis-trans-cis-, and all-cis-1), is presented. The starting compounds, all-trans-, cis-cis-trans, cis-trans-cis-, and all-cis-1,3,5,7-tetraaryl-1,3,5,7-tetraisopropylcyclotetrasiloxanes, were prepared by the hydrolysis of the corresponding arylisopropyldichlorosilanes, i-PrArSiCl2 (Ar = Ph, p-tolyl), and subsequent separation of isomers. A combination of dephenylchlorination of tetraarylcyclotetrasiloxanes and the following hydrolysis proved to be an efficient method for the stereospecific transformation of aryl-substituted cyclotetrasiloxanes into (i-PrSiO(OH))4. For example, treatment of cis-trans-cis-1,3,5,7-tetraphenyl-1,3,5,7-tetraisopropylcyclotetrasilane with HCl and AlCl3, followed by hydrolysis in the presence of pyridine, resulted in the exclusive formation of cis-trans-cis-1 in 92% yield. The structures of cis-cis-trans-1, cis-trans-cis-1, and all-cis-1 were determined by X-ray crystallography. All isomers were found to construct unique packing structures by intermolecular hydrogen bonding; cis-trans-cis-1 composed an infinite antiladder structure, and cis-cis-trans-1 formed a sheetlike structure. [ABSTRACT FROM AUTHOR]

Synthesis of novel cage and cyclic silanols bearing Tip (2,4,6-triisopropylphenyl) groups was performed. Tip-substituted silanetriol, TipSi(OH)3 (1) was prepared from TipSiCl3, and can be handled without special care in the air. The versatility of this silanol is amply demonstrated as a starting material of various silanols with novel frameworks. Thus, the condensation of 1 using 2-chloro-1,3-dimethylimidazolinium chloride as a dehydrating agent afforded (TipSi)5O7OH (2) in 45% yield. When 1 was treated with (TipSiCl2)2O, cis,trans-cyclotrisiloxanetriol (3) as well as a novel incompletely condensed silsesquioxane, (TipSi)4O5(OH)2 (4) were obtained. In addition, the dehydrochlorinative condensation of (TipSiCl2)2O and (TipSi(OH)2)2O afforded 4 as single product. The structures of all these novel silanols were determined by X-ray crystallography, and their unique structures (hydrogen-bonded aggregates or intramolecular hydrogen bonding) were demonstrated. [Copyright &y& Elsevier]

The molecular structure of the silyl-substituted octasilacubane [(t-BuMe2Si)Si]8 (1) was analyzed by X-ray crystallography, and the structural parameters (bond length and angles) were compared with those of the alkyl- and aryl-substituted octasilacubanes. A thermogravimetric analysis revealed that 1 remained stable under argon up to 300 °C, indicating that 1 is much more thermally stable than alkyl-substituted (ThexSi)8 (Thex=1,1,2-trimethylpropyl) (2), which decomposed at 200 °C. Although compound 1 is stable in the air, 1 reacted with m-chloroperoxybenzoic acid (mCPBA). Thus, treatment of 1 with fourteen equivalents of mCPBA led to the formation of octakis(tert-butyldimethylsilylsilsesquioxane) (3) in 98% yield. The structure of 3 was also established by X-ray crystallography, indicating that all the oxygen atoms inserted into the Si&z.sbnd;Si bonds of the Si8 framework and the exocyclic Si&z.sbnd;Si bonds remained intact under the conditions employed. Compound 3 is the first example of silsesquioxane with bulky silyl substituents, and shows relatively intense absorptions in the UV region. [Copyright &y& Elsevier]

An X-ray crystallographic analysis of the bis-N[SUPδ]-Boc-tetra-N[SUPα]-methyl derivative of gramicidin S, cyclo(-VaI-MeOrn(Boc)-Leu-D-MePhe-Pro-)[SUB2], was undertaken successfully (R-factor = 0.088). As expected, the main chain adopts an antiparallel pleated β-sheet conformation, but the pleated sheet is slightly twisted, and the sense of twisting is opposite to that found in the reported crystal structures of the gramicidin S-urea complex and the bis-N[SUPδ]-(trichloroacetyl) and bis-Nδ-(m-bromobenzoyl) derivatives of gramicidin S. In agreement with the observed resistance toward N-methylation, the urethane NH groups of the protected Orn side chains are hydrogen bonded to the carbonyl groups of the D-Phe residues. However, the side-chain-main-chain hydrogen bonding is in the i → i - 3 mode, although hydrogen bonding in the i → i + 2 mode was deduced from a [SUP1]H NMR study of protected gramicidin S derivatives and was actually found in the crystal structures of the diacylated gramicidin S. [ABSTRACT FROM AUTHOR]

In order to enrich hybrid materials, a novel fluorescent silsesquioxane-based polymer (denoted as PCS-OTS) was synthesized by Friedel-Crafts reaction starting from octavinylsilsesquioxane (OVS) with triphenylamine-functionalized silsesquioxane monomer (denoted as OTS) with AlCl3 as catalyst. PCS-OTS possessed a high surface area of 816 m2/g and a unique bimodal pore structure. The triphenylamine unit endowed PCS-OTS with excellent luminescence, which made it act as a sensitive chemical sensor and detect p-nitrophenol with high sensitivity (KSV = 81,230 M−1). Moreover, PCS-OTS can significantly remove dyes, and the respective adsorption capacity for Rhodamine B (RB), Congo red (CR) and Methyl Orange (MO) is 1935, 1420 and 155 mg/g. Additionally, it could simultaneously remove multiple dyes from water by simple filtration and be easily regenerated. This hybrid porous polymer can be a good choice for water treatment. [ABSTRACT FROM AUTHOR]

We previously reported that phenyl- and vinyl-silsesquioxanes (SQs), [RSiO1.5]8,10,12 (R = Ph or vinyl) functionalized with three or more conjugated moieties show red-shifted absorption- and emission features suggesting 3-D conjugation via a cage centered LUMOs. Corner missing [PhSiO1.5]7(OSiMe3)3 and edge opened, end capped [PhSiO1.5]8(OSiMe2)2 (double decker, DD) analogs also offer red shifted spectra again indicating 3-D conjugation and a cage centered LUMO. Copolymerization of DD [PhSiO1.5]8(OSiMevinyl)2 with multiple R–Ar–Br gives copolymers with emission red-shifts that change with degree of polymerization (DP), exhibit charge transfer to F4TNCQ and terpolymer averaged red-shifts suggesting through chain conjugation even with two (O–Si–O) end caps possibly via a cage centered LUMO. Surprisingly, ladder (LL) SQ, (vinylMeSiO2)[PhSiO1.5]4(O2SiMevinyl) copolymers offer emission red-shifts even greater for analogous copolymers requiring a different explanation. Here we assess the photophysical behavior of copolymers of a more extreme SQ form: the half cage [PhSiO1.5]4(OSiMe2Vinyl)4, Vy4HC SQs. We again see small red-shifted absorptions coupled with significant red-shifted emissions, even with just a half cage, thus further supporting the existence of pπ–dπ and/or σ*–π* conjugation through Si–O–Si bonds and contrary to most traditional views of Si–O–Si linked polymers. These same copolymers donate an electron to F4TCNQ generating the radical anion, F4TCNQ−. as further proof of conjugation. Column chromatographic separation of short from longer chain oligomers reveals a direct correlation between DP and emission λmax red-shifts as another indication of conjugation. Further, one- and two-photon absorption and emission spectroscopy reveals multiple excited fluorescence-emitting states in a violation of Kasha's rule wherein emission occurs only from the lowest excited state. Traditional modeling studies again find HOMO LUMO energy levels residing only on the aromatic co-monomers rather than through Si–O–Si bonds as recently found in related polymers. [ABSTRACT FROM AUTHOR]

Tissue engineering scaffolds have been dedicated to regenerating damaged tissue by serving as host biomaterials for cell adhesion, growth, differentiation, and proliferation to develop new tissue. In this work, the design and fabrication of a biodegradable bilayer scaffold consisting of a ternary PLLA/PCL/CAB blend film layer and a PLGA/curcumin (CC) electrospun fiber layer were studied and discussed in terms of surface morphology, tensile mechanical properties, and molecular interactions. Three different compositions of PLLA/PCL/CAB—60/15/25 (TBF1), 75/10/15 (TBF2), and 85/5/10 (TBF3)—were fabricated using the solvent casting method. The electrospun fibers of PLGA/CC were fabricated using chloroform (CF) and dimethylformamide (DMF) co-solvents in 50:50 and 60:40 volume ratios. Spherical patterns of varying sizes were observed on the surfaces of all blend films—TBF1 (17–21 µm) > TBF2 (5–9 µm) > TBF3 (1–5 µm)—caused by heterogeneous surfaces inducing bubble nucleation. The TBF1, TBF2, and TBF3 films showed tensile elongation at break values of approximately 170%, 94%, and 43%, respectively. The PLGA/CC electrospun fibers fabricated using 50:50 CF:DMF had diameters ranging from 100 to 400 nm, which were larger than those of the PLGA fibers (50–200 nm). In contrast, the PLGA/CC electrospun fibers fabricated using 60:40 CF:DMF had diameters mostly ranging from 200 to 700 nm, which were larger than those of PLGA fibers (200–500 nm). Molecular interactions via hydrogen bonding were observed between PLGA and CC. The surface morphology of the bilayer scaffold demonstrated adhesion between these two solid surfaces resembling "thread stitches" promoted by hydrophobic interactions, hydrogen bonding, and surface roughness. [ABSTRACT FROM AUTHOR]

Tetrachloro- and tetraazide-substituted all-cis-tetraphenylcyclotetrasiloxanes (all-cis-T4) 2 and 3 were synthesized in high yields and were fully characterized. Then the precursor 3 underwent CuAAC click reaction with monopropargyl BINOL 4 and dipropargyl BINOL 6 to give the novel BINOL and triazole-containing all-cis-T4 cyclic siloxane 5 and the 29-8-29-membered-ring ladder-type hybrid siloxane 7. The sensing ability of compounds 5 and 7 towards anions was studied as well, and it was observed that 7 could selectively recognize iodides through synergistic C–H⋯I hydrogen bonding, resulting in an impressive fluorescence quenching with a Ksv of 8.10 × 104 M−1. [ABSTRACT FROM AUTHOR]

The synthesis of four novel syn-type tricyclic laddersiloxanes bearing eight or six alkenyl groups is presented. These compounds possess reactive alkenyl groups on both the bridged and side silicon atoms, and their structures were determined through characterization using multinuclear 1D and 2D NMR spectroscopy, mass spectrometry, and elemental analysis techniques. To investigate their reactivity, the compounds were subjected to hydrosilylation using two different silanes, and the resulting fully hydrosilylated compounds were thoroughly analyzed. Remarkably, all the synthesized laddersiloxanes displayed high thermal stability, suggesting their potential as promising precursors for the development of new hybrid materials. Additionally, preliminary findings indicate the possibility of exploiting the reactivity difference between the alkenyl groups attached to the D- and T-unit silicon atoms for the synthesis of Janus molecules. These findings highlight the potential of the reported compounds as valuable building blocks in the construction of innovative materials. [ABSTRACT FROM AUTHOR]

Molecular recognition of dicarboxylates by a dinuclear zinc(II) complex of 2,2ʹ-binaphthalene bearing di(2-pyridyl)aminomethyl groups at 8- and 8ʹ-positions ([Zn2L]4+) by UV-vis and fluorescence spectral titrations in an aqueous solvent was investigated. In a series of α,ω-dicarboxylate, receptor [Zn2L]4+ showed the highest binding affinity for succinate and UV-vis and fluorescence changes were also largest upon the addition of this guest. In a series of phthalate derivatives, phthalate was strongly bound by [Zn2L]4+. The characteristic UV-vis and fluorescence changes strongly depend on the dihedral angle of two naphthyl groups of the complex [Zn2L]4+· dicarboxylate estimated by spectral titrations and DFT calculations. [ABSTRACT FROM AUTHOR]

Innovative macrocyclic 14-membered molecule (5) and tricyclic 18-8-18-membered-ring ladder-type siloxane-based compound (7), with sulfide units inserted in the backbone were prepared through B(C6F5)3-catalyzed Piers–Rubinsztajn reaction. Further oxidation of 5 and 7 with m-CPBA enables the synthesis of the novel sulfonyl-containing cyclic and ladder-type compound (8 and 9) in high yields. Both tricyclic ladder-type products (7 and 9) show superior thermostability and their well-defined syn-type structures were determined by X-ray crystallographic analysis. The compounds 7 and 9 may become promising building blocks for various new materials. [ABSTRACT FROM AUTHOR]

Stereoisomerization of readily available all- cis-1,3,5,7-tetrahydroxy-1,3,5,7-tetraisobutylcyclotetrasiloxane ( 1 a) was carried out under acidic conditions to afford cis- trans- cis ( 1 b), all- trans ( 1 c), and cis- cis- trans ( 1 d) isomers. The compounds in the reaction mixture could be easily separated into 1 a and a mixture of 1 b, 1 c, and 1 d by the treatment with chloroform. Compounds 1 b, 1 c, and 1 d were further separated and isolated, and each structure was identified. The experimental results indicated that the most plausible mechanism is a substitution reaction at the silicon center via a pentacoordinate intermediate without a cyclic siloxane bond cleavage reaction. The obtained isomer 1 a or 1 b further reacted with dichlorodiphenylsilane in the presence of triethylamine to give syn-type laddersiloxane ( 2 a) or anti-type laddersiloxane ( 2 b), respectively. [ABSTRACT FROM AUTHOR]

Abstract: Influence of mixing organic silicon compounds into 1 M (M: mol L−1) LiPF6-ethylene carbonate (EC)/ethylmethyl carbonate (EMC) (mixing volume ratio = 3:7) mixed solvent electrolytes on charge–discharge cycling efficiencies of lithium metal negative electrodes is examined. As organic silicon compounds, polyether-modified siloxanes with polyethylene oxide chains, chlorotrimethylsilane, tetraethoxysilane, cis-tetra [isobutyl (dimethylsiloxy)] cyclotetrasiloxane and cage-type silsesquioxane are investigated. Charge–discharge cycling tests of lithium are galvanostatically carried out using stainless steel working electrodes. Charge–discharge cycling efficiencies of lithium tend to improve by mixing organic silicon compounds. A cage-type silsesquioxane, octaphenyloctasilsesquioxane (Ph8T8) exhibits the highest cycling efficiency of approximately 80% with small mixing amount of 0.02 M Ph8T8. Mechanism of enhancement of lithium cycling efficiencies by mixing organic silicon compounds is considered to be due to the suppression of excess reduction of LiPF6-EC/EMC by lithium and the growth of surface film on lithium. [Copyright &y& Elsevier]

ABSTRACT A phosphine bearing three 2-isopropoxyphenyl groups, P{C6H4[2-O( i-Pr)]}3 ( 1), was synthesized. Phosphine 1 readily reacted with CH2Cl2 and ClCH2CH2Cl at 25°C to give the corresponding phosphonium salts [RCH2P{C6H4[2-O( i-Pr)]}3]X ( 2: R=X=Cl, 3: R=CH2Cl, X=BF4). Platinum, palladium, and rhodium complexes with ligand 1, [PtCl2( 1)2] ( 4), [PdCl2( 1)2] ( 5), [{PdCl( 1)}2(μ-Cl)2] ( 6), and [RhCl(cod)( 1)] ( 7) were synthesized and their structures were determined by X-ray crystallography, which revealed that ligand 1 works as a monodentate ligand in these complexes. [ABSTRACT FROM AUTHOR]

A seriesof phenyl-substituted silsesquioxanes with ladder anddouble-decker structures were synthesized, and their structures weredetermined. Their spectral and physical properties were compared withthose of the previously reported cage, cyclic, and acyclic silsesquioxanes.Comparison of the thermal properties clearly showed that the structuresstrongly affect the thermal stability. [ABSTRACT FROM AUTHOR]

Cyclic silanol derivatives (CSDs), possessing siloxane rings consisting of T-unit silicon and oxygen atoms, are considered efficient precursors for the preparation of versatile well-defined building blocks of hybrid materials such as cyclic, cage- or ladder-type SQs. This review provides an outline of the main synthetic routes to numerous stereoregular CSDs with different sizes of siloxane rings since the first example of CSDs reported by Brown et al. in 1965. The typical reaction conditions and chemical shifts of 29Si NMR of all mentioned CSDs in this review are summarized in tables and schemes to recapitulate the state of the art. The synthesis of all-cis-cyclotetrasiloxanes (T4), the most investigated CSDs, and their functionalization by different organic reactions to access various all-cis-T4 with functional groups are methodically presented. Moreover, the potential of CSDs in multiple application fields is discussed to show the possible research directions of this family of compounds in the future. [ABSTRACT FROM AUTHOR]

Abstract: A ditopic receptor 1 bearing silanol groups as anion recognition sites and a 2,2′-bipyridine moiety as a metal-coordination site was synthesized. The X-ray crystallographic analysis revealed that the receptor 1 simultaneously associated Ag+ at the bipyridine site and at the anion recognition site surrounded by two silanol groups and one C–H proton of the bipyridine. The titration experiments suggested the large affinity of the receptor with AgNO3, caused by the cooperative cation and anion binding. The cooperative effect of metal cation could enhance anion recognition property of silanol-based receptor. [Copyright &y& Elsevier]

Multiple studies have explored using cage silsesquioxanes (SQs) as backbone elements in hybrid polymers motivated by their well‐defined structures and physical and mechanical properties. As part of this general exploration, we report unexpected photophysical properties of copolymers derived from divinyl double decker (DD) SQs, [vinyl(Me)Si(O0.5)2][PhSiO1.5]8[(O0.5)2Si(Me)vinyl] (vinylDDvinyl). These copolymers exhibit strong emission red‐shifts relative to model compounds, implying unconventional conjugation, despite vinyl(Me)Si(O‐)2 siloxane bridges. In an effort to identify minimum SQ structures that do/do not offer extended conjugation, we explored Heck catalyzed co‐polymerization of vinyl‐ladder(LL)‐vinyl compounds, vinyl(Me/Ph)Si(O0.5)2[PhSiO1.5]4(O0.5)2Si(Me/Ph)vinyl, with Br‐Ar‐Br. Most surprising, the resulting oligomers show 30–60 nm emission red‐shifts beyond those seen with vinylDDvinyl analogs despite lacking a true cage. Further evidence for unconventional conjugation includes apparent integer charge transfer (ICT) between LL‐co‐thiophene, bithiophene, and thienothiophene with 10 mol % F4TCNQ, suggesting potential as p‐type doped organic/inorganic semiconductors. [ABSTRACT FROM AUTHOR]

Multiple studies have explored using cage silsesquioxanes (SQs) as backbone elements in hybrid polymers motivated by their well‐defined structures and physical and mechanical properties. As part of this general exploration, we report unexpected photophysical properties of copolymers derived from divinyl double decker (DD) SQs, [vinyl(Me)Si(O0.5)2][PhSiO1.5]8[(O0.5)2Si(Me)vinyl] (vinylDDvinyl). These copolymers exhibit strong emission red‐shifts relative to model compounds, implying unconventional conjugation, despite vinyl(Me)Si(O‐)2 siloxane bridges. In an effort to identify minimum SQ structures that do/do not offer extended conjugation, we explored Heck catalyzed co‐polymerization of vinyl‐ladder(LL)‐vinyl compounds, vinyl(Me/Ph)Si(O0.5)2[PhSiO1.5]4(O0.5)2Si(Me/Ph)vinyl, with Br‐Ar‐Br. Most surprising, the resulting oligomers show 30–60 nm emission red‐shifts beyond those seen with vinylDDvinyl analogs despite lacking a true cage. Further evidence for unconventional conjugation includes apparent integer charge transfer (ICT) between LL‐co‐thiophene, bithiophene, and thienothiophene with 10 mol % F4TCNQ, suggesting potential as p‐type doped organic/inorganic semiconductors. [ABSTRACT FROM AUTHOR]

Tetra(3-mercaptopropyl)-silsesquioxanes with double-decker (DDSQ) or ladder nano-cores were easily prepared from the corresponding tetraallyl derivatives through fast and convenient thiol–ene reactions. An additional tetrathiol-DDSQ with more flexible arms was also synthesized in high yield from the corresponding tetrachloro-DDSQ derivative. The three novel tetrathiol silsesquioxanes described represent versatile building blocks for the preparation of hybrid organic–inorganic materials. [ABSTRACT FROM AUTHOR]

Previous studies have demonstrated that functionalised T8 polyhedral oligomeric silsesquioxanes with fluoride anions encapsulated within the T8 cage (T8-F) have very low reactivity, with no reports of successful modification of the organic moieties. Herein, we report the successful modification of a styryl functionalised T8-F compound with mercaptopropyltriethoxysilane using a thiol–ene click reaction. This strategy enables the vinyl moiety to be modified while maintaining the influence of the electron-withdrawing phenylene group, which stabilises the fluoride within the cage. The triethoxysilylated T8-F cages were subsequently converted into nanohybrids by sol–gel processing. Multinuclear NMR experiments (29Si, 19F, 13C) demonstrated that the POSS cage remained intact during both post functionalisation of T8-F and subsequent sol-gel processing. Furthermore, 29Si cross polarisation solid state NMR experiments using 19F as a cross polarisation agent demonstrated that the fluoride anions remain localised within the cages in the nanohybrids. The functionalisation of the styryl bearing T8-F POSS cage is the first example of both the successful modification of the poorly reactive T8-F family and the formation of a nanohybrid material incorporating fluoride ions immobilised within covalently bound T8 cages. [ABSTRACT FROM AUTHOR]

A new synthetic method for tricyclic laddersiloxanes, ladder‐type silsesquioxanes with defined structures, is developed based on intramolecular cyclization of hydrosilyl‐functionalized cyclic siloxanes. This method enables the construction of unprecedented laddersiloxanes with various ring sizes. Herein, the preparation of tricyclic laddersiloxanes containing 6‐8‐6‐, 8‐8‐8‐, or 12‐8‐12‐membered‐ring systems is reported. These products can be considered as bat‐shape siloxanes, owing to their rigid inorganic siloxane body with flexible oligosiloxane "wings" as side rings. The synthesized compounds are potential building blocks for well‐defined nanomaterials, porous materials, and host molecules. [ABSTRACT FROM AUTHOR]

The synthesis of organo‐functionalized polyhedral oligomeric silsesquioxanes (POSS, (R‐SiO1.5)n, Tn) is an area of significant activity. To date, T14 is the largest such cage synthesized and isolated as a single isomer. Herein, we report an unprecedented, single‐isomer styryl‐functionalized T18 POSS. Unambiguously identified among nine possible isomers by multinuclear solution NMR (1H, 13C, and 29Si), MALDI‐MS, FTIR, and computational studies, this is the largest single‐isomer functionalized Tn compound isolated to date. A ring‐strain model was developed to correlate the 29Si resonances with the number of 6‐, 5‐, and/or 4‐Si‐atom rings that each non‐equivalent Si atom is part of. The model successfully predicts the speciation of non‐equivalent Si atoms in other families of Tn compounds, demonstrating its general applicability for assigning 29Si resonances to Si atoms in cage silsesquioxanes and providing a useful tool for predicting Si‐atom environments. [ABSTRACT FROM AUTHOR]

The synthesis of organo‐functionalized polyhedral oligomeric silsesquioxanes (POSS, (R‐SiO1.5)n, Tn) is an area of significant activity. To date, T14 is the largest such cage synthesized and isolated as a single isomer. Herein, we report an unprecedented, single‐isomer styryl‐functionalized T18 POSS. Unambiguously identified among nine possible isomers by multinuclear solution NMR (1H, 13C, and 29Si), MALDI‐MS, FTIR, and computational studies, this is the largest single‐isomer functionalized Tn compound isolated to date. A ring‐strain model was developed to correlate the 29Si resonances with the number of 6‐, 5‐, and/or 4‐Si‐atom rings that each non‐equivalent Si atom is part of. The model successfully predicts the speciation of non‐equivalent Si atoms in other families of Tn compounds, demonstrating its general applicability for assigning 29Si resonances to Si atoms in cage silsesquioxanes and providing a useful tool for predicting Si‐atom environments. [ABSTRACT FROM AUTHOR]

The synthesis of a styryl functionalised POSS incorporating an encapsulated fluoride ion within a (SiO1.5)8 cage (T8-F) is reported. It was characterised by single crystal XRD, MALDI-MS, FTIR, solution (29Si, 19F, 13C, 1H) and solid state (29Si, 19F) NMR. In the absence of 1H decoupling, the 29Si solution NMR spectrum exhibited a triplet of doublets. In contrast, 1H, 19F and 1H/19F double-decoupling resulted in two, three and one signal, respectively, being consistent with a single Si site whose 29Si NMR signal is modulated by both the proximal aromatic-ring protons and fluoride. The associated Si⋯F coupling constant (2.5 Hz) is substantially lower than expected for a covalent Si–F bond and arises from a fluxional Si⋯F covalent effect in which the F− interacts equivalently with all eight Si atoms. Additional variable temperature NMR studies demonstrated a threshold at −5 °C below which no Si⋯F interactions are observed, and above which an increasing Si⋯F covalent character occurs. [ABSTRACT FROM AUTHOR]

All-cis-tetrasiloxycyclotetrasiloxanes (Janus ring siloxanes) were facilely prepared from all-cis-cyclotetrasiloxanetetraol or sodium cyclotetrasiloxane silanolates. Moreover, we demonstrated the synthesis of extended Janus rings, [RSi(OR')O]4, containing various functional groups, via the Piers–Rubinsztajn reaction using a Janus ring siloxane as a precursor. Remarkably, we discovered the formation of an unexpected all-cis tricyclic laddersiloxane as a by-product. These synthesized compounds can be potential monomers of well-defined cage silsesquioxanes, Janus-type nanomaterials, and porous materials. [ABSTRACT FROM AUTHOR]

We have synthesized and separated the enantiomer pair of chiral cyclotrisiloxanes for the first time. Three-blade propeller-like alignment of three phenyl groups in tri(2-butyl)triphenylcyclotrisiloxane induced a positive Cotton effect with (R)-2-butyl group, and a negative effect with (S)-2-butyl substituent. [ABSTRACT FROM AUTHOR]

Abstract: Anion recognition properties of d-ribose-based receptors α- and β-1 were measured by 1H NMR in CDCl3 and MeCN-d 3. Receptor β-1 showed effective binding with anions by cooperative hydrogen bonds of cis-diol. The anomeric isomer α-1 is a less effective anion receptor which has similar cis-diol as a recognition site, indicating that the stereo configuration of the anomeric position is of significant influence on the anion recognition ability. [Copyright &y& Elsevier]

Siloxane-based materials have a wide range of applications. Cage-type oligosiloxanes have attracted significant attention as molecular building blocks to construct novel siloxane-based nanoporous materials with promising applications such as in catalysis and adsorption. This paper reviews recent progress in the preparation of siloxane-based nanoporous materials using alkoxy- and silanol-functionalized cage siloxanes. The arrangement of cage siloxanes units is controlled by various methods, including amphiphilic self-assembly, hydrogen bonding of silanol groups, and regioselective functionalization, toward the preparation of ordered nanoporous siloxane-based materials. [ABSTRACT FROM AUTHOR]

Polyhedral oligomeric silsesquioxanes (POSSs), Am-POSS(x,y), prepared by hydrolytic condensation, contains two types of ammonium side-chain groups, where the numbering of x and y represents the type of ammonium ions in the POSS structure, corresponding to primary (1), secondary (2), tertiary (3), and quaternary (4) ammonium ions. Mixtures of the two starting materials selected from organotrialkoxysilanes containing primary, secondary, and tertiary amines and a quaternary ammonium salt [(RO)3Si(CH2)3R′, R = CH3 or CH2CH3, R′ = NH2, NHCH3, N(CH3)2, and N(CH3)3Cl] were dissolved in dimethyl sulfoxide (DMSO). The hydrolytic condensation was performed in the presence of bis(trifluoromethansulfonyl)imide (HNTf2) and water. All Am-POSS(x,y) structures consisted of a cage-type octamer (T8-POSS), as confirmed by 29Si NMR spectrometry and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses indicated that Am-POSS(1,3), Am-POSS(1,4), and Am-POSS(2,4) had amorphous structures. These POSSs have two or three differences in the number of methyl groups between the two types of ammonium side-chains. Conversely, Am-POSS(1,2), Am-POSS(2,3), and Am-POSS(3,4) had crystalline structures. The difference in the number of methyl groups between the two types of ammonium side-chains in these POSSs is only one. Therefore, the crystalline-amorphous structure of Am-POSS(x,y) is controlled by the side-chain group combinations. Furthermore, Am-POSS(1,3), Am-POSS(1,4), and Am-POSS(2,4) are protic ionic liquids with relatively low flow temperatures. [ABSTRACT FROM AUTHOR]

The one-pot synthesis of an unsymmetrical double-decker siloxane with a novel structure via the reaction of double-decker tetrasodiumsilanolate with 1 equiv. of dichlorotetraphenyldisiloxane in the presence of an acid is reported herein for the first time. The target compound bearing all phenyl substituents on the unsymmetrical siloxane structure was successfully obtained, as confirmed by 1H-NMR, 13C-NMR, 29Si-NMR, IR, MALDI-TOF, and X-ray crystallography analyses. Additionally, the thermal properties of the product were evaluated by TG/DTA and compared with those of other siloxane cage compounds. [ABSTRACT FROM AUTHOR]

The catalytic dehydrocoupling of amine–boranes has recently received a great deal of attention due to its potential in hydrogen storage applications. The use of aluminum catalysts for this transformation would provide an additional cost-effective and sustainable approach towards the hydrogen economy. Herein, we report the use of both N-heterocyclic imine (NHI)- and carbene (NHC)-supported Al(III) hydrides and their role in the catalytic dehydrocoupling of Me2NHBH3. Differences in the σ-donating ability of the ligand class resulted in a more stable catalyst for NHI-Al(III) hydrides, whereas a deactivation pathway was found in the case of NHC-Al(III) hydrides. [ABSTRACT FROM AUTHOR]

Novel polyhedral structures were prepared with a butterfly‐shape composed of oligosiloxane wings and a double‐decker silsesquioxane (DDSQ) body. The compounds were synthesized in two steps from commercially available alkoxysilanes, and their structures were confirmed using spectroscopic methods and X‐ray crystallography. Not like other phenyl‐substituted cage silsesquioxanes, these butterfly cages show very good solubility in common organic solvents. The crystal structures clearly showed their unique features: a larger space with longer siloxane chains and a very flexible framework. Moreover, these compounds are thermally stable with a Td5 (5 % weight loss temperature) over 320 °C. [ABSTRACT FROM AUTHOR]

Dimethylpalladium complex bearing PS 3 -type tripodal tetradentate ligand, [PdMe 2 {P(C 6 H 4 -2-S- i -Pr) 3 }], was synthesized by the reaction of [PdCl{P(C 6 H 4 -2-S- i -Pr) 3 }]X (X = Cl, BF 4) with methyllithium (Br free). The dimethylpalladium complex reacted with an equimolar amounts of HCl to give the corresponding chloromethylpalladium complex, [PdClMe{P(C 6 H 4 -2-S- i -Pr) 3 }], while the similar reaction using 2 M amounts of HCl afforded the dichloropalladium complex, [PdCl{P(C 6 H 4 -2-S- i -Pr) 3 }]Cl. The detailed structures of the complexes were revealed by X-ray crystallography and variable temperature 1H NMR studies. Image 1 • [PdMe 2 (L)] (L: PS 3 -type tripodal tetradentate ligand) was synthesized. • Reaction of [PdMe 2 (L)] with HCl afforded [PdClMe(L)] or [PdCl 2 (L)] selectively. • The detailed structure of [PdMe 2 (L)] and [PdClMe(L)] was studied by X-ray analysis. • The dynamic behavior of [PdMe 2 (L)] and [PdClMe(L)] was studied by VT NMR. [ABSTRACT FROM AUTHOR]

Symmetric and asymmetric (Janus‐type) new "lantern cage" siloxanes (PhSiO1.5)4(Me2SiO)4(RSiO1.5)4 (R=Ph or iBu) were synthesized through reaction of all‐cis‐[PhSi(OSiMe2Br)O]4 with all‐cis‐[RSi(OH)O]4 (R=Ph or iBu). These precursors were obtained by facile two or three‐step reactions from commercially available compounds. The spectroscopic properties of the resulting products were fully characterized and they showed high thermal stability and sublimation without decomposition. The crystal structures clearly indicated that the internal vacancy volumes of the lantern cages are considerably larger than that of octaphenylsilsesquioxane (PhSiO1.5)8. DFT calculations of the lantern cage showed a distinctly different electronic state from that of octasilsesquioxane. These results suggest that lantern cage siloxanes have a characteristic "field" in the molecule. Lantern cage silsesquioxane: Symmetric and novel asymmetric (Janus‐type) new "lantern cage" siloxanes that contains a large interior space were synthesized, and structure and electronic properties were investigated. [ABSTRACT FROM AUTHOR]

A perfect 'Janus-cube' octasilsesquioxane, a nanometer-scale Janus particle with two different types of substituents, was synthesized through the cross-coupling of a 'half-cube' cyclic sodium siloxanolate with another half-cube cyclic fluorosiloxane. The structure was confirmed by X-ray crystallography to be a Janus cube. The overall synthesis is simple and does not require drastic separation methods compared with previous methods. The synthesis of the Janus cube demonstrates a novel siloxane bond-forming reaction involving the coupling a silanol salt and fluorosilane. The reaction is mild, does not result in acid generation, and could be applied to the construction of other novel siloxane compounds. [ABSTRACT FROM AUTHOR]

A perfect 'Janus-cube' octasilsesquioxane, a nanometer-scale Janus particle with two different types of substituents, was synthesized through the cross-coupling of a 'half-cube' cyclic sodium siloxanolate with another half-cube cyclic fluorosiloxane. The structure was confirmed by X-ray crystallography to be a Janus cube. The overall synthesis is simple and does not require drastic separation methods compared with previous methods. The synthesis of the Janus cube demonstrates a novel siloxane bond-forming reaction involving the coupling a silanol salt and fluorosilane. The reaction is mild, does not result in acid generation, and could be applied to the construction of other novel siloxane compounds. [ABSTRACT FROM AUTHOR]

Two new all- cis pyrene-substituted cyclic tetrasiloxanes (JR-01 and JR-02) are synthesized and studied as selective metal ion sensors. Both compounds exhibit solvent- and concentration-dependent excimer fluorescence emission at 482 nm. They also show highly selective fluorescence quenching by Au(III) ion with detection limits of 0.9 and 0.8 μM for JR-01 and JR-02 , respectively. Data from the Stern-Volmer's plots at various temperatures, zetasizers, NMR, and UV–Vis spectroscopy indicate a plausible mechanism involving the formation of a non-emissive Au(III) complex. An application of JR-01 as Au(III) sensor in real water samples reveals a good sensing efficiency which is comparable to the analysis result from ICP-QMS. In addition, when an excess amount of l -cysteine is added to the JR-01 /Au(III) mixture, the fluorescence signal is restored and the 1H NMR data suggests that JR-01 remains intact. As an extension of this study, we successfully demonstrate the detection of l -cysteine by fluorescence turn-on process using the JR-01 /Au(III) mixture with a detection limit of 14.0 μM. • Two new cyclic tetrasiloxanes are synthesized as selective Au(III) sensors. • The sensing mechanism involves the formation of a non-emissive complex. • The Au(III) complex can be used as a turn-on sensor for l -cysteine. [ABSTRACT FROM AUTHOR]

[Display omitted] The first representative of the Janus cube with hydrogen substituents was obtained from all- cis -[BuiSiO(OH)] 4 by its capping with HSiCl 3 followed by gentle hydrolysis causing internal condensation. The compound has an extremely low maximum loss temperature, which is approximately halfway between H 8 Si 8 O 12 and (octaisobutyl)octasilsesquioxane. [ABSTRACT FROM AUTHOR]

• A functional laddersiloxane bearing four vinyl groups on the T 4 unit is prepared. • The vinyl groups undergo quantitative hydrosilylation thanks to very low Pt loadings. • Tetrachloro laddersiloxanes are prepared in very high yields. • The laddersiloxanes reported are promising precursors for hybrid materials. A straightforward, efficient and scalable (gram scale) route to an unprecedented 6–8–6 laddersiloxane 3 bearing four vinyl groups on the cyclotetrasiloxane T 4 unit is reported. Compound 3 was fully characterized by multinuclear NMRs, mass spectrometry, and its structure was determined by X-ray crystallography. The reactivity of the vinyl functions was next explored and hydrosilylations of 3 were successfully achieved with three different silanes in the presence of a small amount of Pt catalyst (0.025 mol% of Pt per vinyl function) in each case. The resulting laddersiloxanes were isolated in high yields (76 to 99%) after straightforward work-ups and fully characterized. With its high thermal stability (Td 5 = 372 °C) and chemical versatility, 3 thus appears as a promising precursor for building hybrid materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: To improve the solubility of 2,2′-binaphthalene derivatives bearing urea groups, a series of bisureas based on 2,2′-binaphthalene with various alkyl and aryl substituents at the terminal nitrogen atom of the ureas has been synthesized via a bisisocyanate intermediate. The solubility of the receptors was evaluated by means of UV–vis spectroscopy. Receptors 3 and 8 bearing sterically bulky tert-butyl and 2,6-dimethylphenyl groups as substituents at urea moieties showed good solubility in common organic solvents. UV–vis spectral titrations revealed that the receptor 3 maintained the binding ability for anions, however, 8 showed lowering of the binding ability for anions. The anion-binding ability of receptor 3 is in the order of F− >AcO− >Cl− >(EtO)2PO2 − >Br− >NO3 − >ClO4 − >I−. Receptor 3 showed strong emission at 440nm in MeCN and the emission was gradually quenched upon the addition of Cl− and AcO−, indicating that 3 can be useful as fluorescence sensor for anions. The receptor 3 can be applied to a chloride selective electrode and the selectivity of 3 is sufficient for analytical use. [Copyright &y& Elsevier]

Abstract: Synthesis and anion recognition properties of 2,2′-binaphthalene derivatives bearing two thiourea (1) and urea (2) groups at 8- and 8′-positions were studied. The structure of receptor 1 was determined by X-ray crystallography. UV–vis spectra of the receptors showed characteristic changes around 300–400nm through isosbestic points upon the addition of biologically relevant anions such as acetate, dihydrogenphosphate, and chloride in MeCN and DMSO due to restriction of the rotation around the single bond connecting two naphthyl moieties by cooperative guest binding of two recognition sites. Job’s plots showed 1:1 complexation for guest anions. The fluorescence quantum yields of free form of 1 and 2 in MeCN were determined to be 0.021 and 0.57, respectively. The fluorescence intensities of the receptors diminished upon the addition of anions in MeCN. The association constants of receptors 1 and 2 were one or two orders of magnitude greater than the corresponding monothiourea and urea receptors 3 and 4 indicating cooperative hydrogen bonding with guest anions. The selectivity trends of association of anions were F−>AcO−>H2PO4 −>Cl−>>HSO4 −≈NO3 −≈Br−≈I− for 1, and F−>AcO−≈Cl−>H2PO4 −>Br−>HSO4 −>I−≈NO3 − for 2. Receptor 2 showed remarkable Cl− selectivity presumably owing to suitable orientation for effective hydrogen bond formation with Cl−. [ABSTRACT FROM AUTHOR]

Abstract: As a novel chromofluorophore, 9,9′-dimethyl-2,2′-bianthracene 3 has been successfully synthesized by reductive coupling of 2-chloro-9-methylanthracene. Absorbance and fluorescence maxima of 3 can be shifted to visible-region comparing to the former 2,2′-binaphthyl-based receptors. Receptor 2 bearing aza-15-crown-5 moieties via methylene spacer provides selective UV–vis and fluorescence responses for Ba2+ due to the restriction of the conformational change through the formation of an intramolecular sandwich-complex by two azacrown ethers, resulting in the presence of Ba2+ that can be detected by naked eye in aqueous acetonitrile. [Copyright &y& Elsevier]