Blue Emitting Star-Shaped and Octasilsesquioxane-Based Polyanions Bearing Boron Clusters. Photophysical and Thermal Properties

High boron content systems were prepared by the peripheral functionalisation of 1,3,5-triphenylbenzene (TPB) and octavinylsilsesquioxane (OVS) with two different anionic boron clusters: closo-dodecaborate (B12) and cobaltabisdicarbollide (COSAN). TPB was successfully decorated with three cluster units by an oxonium ring-opening reaction, while OVS was bonded to eight clusters by catalysed metathesis cross-coupling. The resulting compounds were spectroscopically characterised, and their solution-state photophysical properties analysed. For TPB, the presence of COSAN dramatically quenches the fluorescence emission (λem = 369 nm; ΦF = 0.8%), while B12-substituted TPB shows an appreciable emission efficiency (λem = 394 nm; ΦF = 12.8%). For octasilsesquioxanes, the presence of either COSAN or B12 seems to be responsible for ∼80 nm bathochromic shift with respect to the core emission, but both cases show low emission fluorescence (ΦF = 1.4–1.8%). In addition, a remarkable improvement of the thermal stability of OVS was observed after its functionalisation with these boron clusters.

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Novel Thermally Stable Epoxy-polyurethane Composites: Preparation, Characterization

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.239-242.2742 ◽

2011 ◽

Vol 239-242 ◽

pp. 2742-2747

Author(s):

Jing Lin ◽

Qiu Zhuan Yang ◽

Xiu Fang Wen ◽

Zhi Qi Cai ◽

Pi Hui Pi ◽

...

Keyword(s):

Thermal Stability ◽

Ring Opening ◽

Thermal Characteristics ◽

Ring Opening Reaction ◽

Tetramethylammonium Bromide ◽

One Step ◽

Novolac Epoxy ◽

Polyurethane Composites ◽

Novolac Epoxy Resins ◽

Thermal Stability Of

A novel series of hydroxyl terminated bisphenol-A type novolac epoxy resins modified with propionic acid (MEP) were prepared by one-step ring-opening reaction process in the presence of tetramethylammonium bromide catalyst. The obtained MEP was characterized using FTIR,1HNMR analyses. In addition, Intercross-linked epoxy-polyurethane composites networks were also obtained by curing reaction among MEP, cross linker polyisocyanate IL1351 and phthalic anhydride. The thermal characteristics of the epoxy-polyurethane composites were determined by thermogravimetric analysis (TGA). The thermal stability of the cured MEP with different ring-opening rate and cured alkyd polyol A450 were compared. The results showed that the obtained epoxy-polyurethane composites had much better thermal stability than the conventional polyurethane system A450/IL1351, and the thermal stability of them was correlated to the content of MEP.

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Macromolecular Dyes by Chromophore-Initiated Ring Opening Polymerization of L-Lactide

Polymers ◽

10.3390/polym12091979 ◽

2020 ◽

Vol 12 (9) ◽

pp. 1979

Author(s):

Francesca Cicogna ◽

Guido Giachi ◽

Luca Rosi ◽

Elisa Passaglia ◽

Serena Coiai ◽

...

Keyword(s):

Ring Opening ◽

Solid Phase ◽

Photophysical Properties ◽

Fluorescence Emission ◽

Ring Opening Polymerization ◽

Polymerization Process ◽

Polymerization Reaction ◽

Poly Lactic Acid ◽

Electromagnetic Spectrum ◽

Visible Part

End functionalized polylactides are prepared by ring opening polymerization of L-lactide in the presence of stannous octoate (Sn(Oct)2). Three chromophores, 9H-carbazol-ethanol (CA), 9-fluorenyl-methanol (FM), and 2-(4-(2-chloro-4-nitrophenylazo)-N-ethylphenylamino)ethanol (Disperse Red 13, DR), are for the first time used as co-initiators in the polymerization process. The polymerization reaction is initiated by conventional thermal treatment, but in the case of FM, microwave-assisted polymerization is also carried out. CA and FM absorb and emit in the UV portion of the electromagnetic spectrum, whereas DR absorbs in the visible part. The obtained end-capped polylactides derivatives show the same photophysical properties as the initiator, so they are “macromolecular dyes” (MDs) that can be used “as synthesized” or can be blended with commercial poly(lactic acid) (PLA). The blends of PLA with MDs have ultraviolet-visible (UV-Vis) absorption and fluorescence emission features similar to that of MDs and thermal properties typical of PLA. Finally, migration tests, carried out onto the blends of PLA with MDs and PLA with free chromophores, show that MDs are less released than free chromophores both in solution and in the solid phase.

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Ethyne Functionalized Meso-Phenothiazinyl-Phenyl-Porphyrins: Synthesis and Optical Properties of Free Base Versus Protonated Species

Molecules ◽

10.3390/molecules25194546 ◽

2020 ◽

Vol 25 (19) ◽

pp. 4546

Author(s):

Eva Molnar ◽

Emese Gál ◽

Luiza Găină ◽

Castelia Cristea ◽

Luminița Silaghi-Dumitrescu

Keyword(s):

Absorption Spectra ◽

Density Functional ◽

Photophysical Properties ◽

Bathochromic Shift ◽

Fluorescence Emission ◽

Soret Band ◽

Quantum Yields ◽

Free Base ◽

Wave Absorption ◽

Long Wave

Synthesis, structural characterization and photophysical properties for a series of new trans-A2B2- and A3B-type ethynyl functionalized meso-phenothiazinyl-phenyl porphyrin derivatives are described. The new compounds displayed the characteristic porphyrin absorption spectra slightly modified by weak auxochromic effects of the substituents and fluorescence emission in the range of 651–659 nm with 11–25% quantum yields. The changes recorded in the UV-vis absorption spectra in the presence of trifluoroacetic acid (TFA) are consistent with the protonation of the two internal nitrogen atoms of the free-base porphyrin (19 nm bathochromic shift of the strong Soret band and one long wave absorption maxima situated in the range of 665–695 nm). Protonation of the phenothiazine substituents required increased amounts of TFA and produced a distinct hypsochromic shift of the long wave absorption maxima. The density functional theory (DFT) calculations of a porphyrin dication pointed out a saddle-distorted porphyrin ring as the ground-state geometry.

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Mechanical Behavior of High Boron Content Al-B4C Metal Matrix Composites at Elevated Temperatures

Materials Science Forum ◽

10.4028/www.scientific.net/msf.706-709.631 ◽

2012 ◽

Vol 706-709 ◽

pp. 631-637 ◽

Cited By ~ 15

Author(s):

X. Grant Chen ◽

Lyne St-Georges ◽

M. Roux

Keyword(s):

Mechanical Properties ◽

Thermal Stability ◽

Metal Matrix Composites ◽

Metal Matrix ◽

Boron Content ◽

Elevated Temperatures ◽

Matrix Composites ◽

Neutron Absorber ◽

High Boron ◽

Thermal Stability Of

High boron content Al-B4C metal matrix composites are highly attractive as an excellent neutron absorber material for the storage of spent nuclear fuels. In the present paper, the mechanical properties of two composites with AA1100 matrix reinforced with 25 and 30 vol.% B4C at ambient and elevated temperatures have been investigated. The thermal stability of two composites at 300°C is experimentally determined. The microstructural features and the tensile fracture at different conditions are examined. It is found that the mechanical properties of both composites remain unchanged at 300°C after a long holding period up to 1000 h. The thermal stability of the mechanical properties of the composites is directly related to the stability of all microstructural compounds of the material. Finally, the effect of the tensile temperatures on the fracture mechanism is assessed.

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High-Boron-Content Porphyrin-Cored Aryl Ether Dendrimers: Controlled Synthesis, Characterization, and Photophysical Properties

Inorganic Chemistry ◽

10.1021/acs.inorgchem.5b00618 ◽

2015 ◽

Vol 54 (10) ◽

pp. 5021-5031 ◽

Cited By ~ 18

Author(s):

Justo Cabrera-González ◽

Elba Xochitiotzi-Flores ◽

Clara Viñas ◽

Francesc Teixidor ◽

Héctor García-Ortega ◽

...

Keyword(s):

Boron Content ◽

Photophysical Properties ◽

Controlled Synthesis ◽

Aryl Ether ◽

High Boron

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Solvatochromic Study of Supramolecular Amphiphile Based on Calix[4]arene Connected to a Fluorescent Benzofurazan Moiety at Lower Rim: Evaluation of Ground and Excited State Dipole Moments-=SUP=-*-=/SUP=-

Журнал технической физики ◽

10.21883/os.2020.12.50322.1028-20 ◽

2020 ◽

Vol 128 (12) ◽

pp. 1864

Author(s):

S. Joshi

Keyword(s):

Dipole Moment ◽

Excited State ◽

Ground State ◽

Fluorescence Spectra ◽

Dipole Moments ◽

Photophysical Properties ◽

Bathochromic Shift ◽

Fluorescence Emission ◽

Wide Range ◽

Excited State Dipole Moment

Photophysical properties of a supramolecular amphiphile of calix[4]arene having benzofurazan moiety at the lower rim, L has been studied. Electronic absorption and fluorescence spectra of L have been recorded in wide range of solvents of different polarities and data were used to study solvatochromic properties. The ground state and the excited state dipole moment of L were estimated from the Bakhshiev's and Bilot-Kawaski's equations. High value of dipole moment is observed for excited state as compared to ground state value and this is attributed to more polar excited state of molecule. Also, fluorescence emission peak undergoes a bathochromic shift with increase in the polarity of the solvent, confirming π-> π* transition. Scanning electron microscopy reveals that the aggregation of L is increased on going from the polar to non polar solvents. Keywords: solvatochromism, benzofurazan, dipole moment, quantum yield, absorption, fluoresence.

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Host-guest complexes of anionic porphyrin sensitizers with cyclodextrins

Journal of Porphyrins and Phthalocyanines ◽

10.1142/s1088424602000646 ◽

2002 ◽

Vol 06 (08) ◽

pp. 514-526 ◽

Cited By ~ 20

Author(s):

Jiří Mosinger ◽

Viktor Kliment ◽

Jan Sejbal ◽

Pavel Kubát ◽

Kamil Lang

Keyword(s):

Singlet Oxygen ◽

Specific Binding ◽

Photophysical Properties ◽

Bathochromic Shift ◽

Fluorescence Emission ◽

Binding Constants ◽

Quantum Yields ◽

Hydroxyl Groups ◽

Triplet States ◽

Binding Modes

The photodynamic sensitizers zinc(II)- and palladium(II)-5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrins and 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin form 1:1 and/or 1:2 supramolecular complexes with native cyclodextrins (CD) and 2-hydroxypropyl cyclodextrins (hpCD) in aqueous neutral solutions. The formation of these assemblies causes a bathochromic shift of the porphyrin Soret band in the UV-vis spectra and a red shift of the fluorescence emission bands. The binding constants span over three orders of magnitude, from 8.1 × 102 M −1 to 5.4 × 105 M −1 (or 1.1 × 106 M −2) depending on the size of the CD cavity and on the functionalization by adding 2-hydroxypropyl groups. The highest binding constants were obtained for hpβCD and hpγCD. The Nuclear Overhauser spectroscopy signals (ROESY) revealed three binding modes: i) inclusion of the porphyrin 4-sulfonatophenyl or 4-carboxyphenyl groups via the secondary face of βCD and hpβCD with sulfonic or carboxylic groups oriented towards the primary hydroxyl groups. ii) inclusion of the porphyrin groups via the primary face of γCD and hpγCD. iii) non-specific binding of the porphyrin monomers or aggregates on the cyclodextrin exterior. The inclusion host-guest complexation via i) or ii) does not influence the inherent photophysical properties of the monomeric porphyrins such as the quantum yields of fluorescence, the triplet states, and the singlet oxygen formation. Due to the deaggregation effect of cyclodextrins, the inclusion complexes remain efficient supramolecular sensitizers of singlet oxygen even under conditions of extensive aggregation in aqueous solutions.

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Recent Advances in the Synthesis of High Boron-Loaded Nucleic Acids for BNCT

Frontiers in Chemistry ◽

10.3389/fchem.2021.619052 ◽

2021 ◽

Vol 9 ◽

Author(s):

Darya Sergeevna Novopashina ◽

Mariya Alexandrovna Vorobyeva ◽

Alya Venyaminova

Keyword(s):

Nucleic Acids ◽

Boron Content ◽

Neutron Capture Therapy ◽

Boron Clusters ◽

Boron Neutron Capture ◽

High Boron ◽

Low Toxicity ◽

Therapeutic Tools ◽

Phosphate Diesters ◽

Oligonucleotide Conjugates

Boron clusters attract considerable attention as promising therapeutic tools for boron neutron capture therapy (BNCT). They combine high boron content with high chemical and biological stability, biorthogonality, and low toxicity. The development of oligonucleotide-based constructs and nucleic acid-like molecules, such as oligomeric phosphate diesters, bearing one or multiple boron clusters permits to create potential high boron-loaded agents for BNCT with good bioavailability, specifically interacting with nucleic acids inside the cell. Here, we shortly review the strategies and solutions in the design of oligonucleotide conjugates with boron clusters in light of the requirements for effective BNCT and future prospects of their practical use.

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Reversing the Thermal Stability of a Molecular Switch on a Gold Surface: Ring-Opening Reaction of Nitrospiropyran

Journal of the American Chemical Society ◽

10.1021/ja901238p ◽

2009 ◽

Vol 131 (35) ◽

pp. 12729-12735 ◽

Cited By ~ 52

Author(s):

Marten Piantek ◽

Gunnar Schulze ◽

Matthias Koch ◽

Katharina J. Franke ◽

Felix Leyssner ◽

...

Keyword(s):

Thermal Stability ◽

Ring Opening ◽

Gold Surface ◽

Molecular Switch ◽

Ring Opening Reaction ◽

Thermal Stability Of

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On the Conrotatory Ring Opening of 3-Carbomethoxycyclobutene Vis-À-Vis 3-Carbomethoxy-1,2-Benzocyclobutene and the Predominant Inward Opening of 3-Dimethylaminocarbonyl-1,2-Benzocyclobutene

10.26434/chemrxiv.7094003.v1 ◽

2018 ◽

Author(s):

Veejendra Yadav ◽

Dasari L V K Prasad ◽

Arpita Yadav ◽

Maddali L N Rao

Keyword(s):

Transition State ◽

Ring Opening ◽

Electron Process ◽

Ring Opening Reaction ◽

Stable Species ◽

Electron Event

The torquoselectivity of conrotatory ring opening of 3-carbomethoxycyclobutene is controlled by pC1C2→s*C3C4 and sC3C4→p*CO interactions in the transition state in a 4-electron process as opposed to only sC3C4→p*CO interaction in an apparently 8-electron event in 3-carbomethoxy-1,2-benzocyclobutene. The ring opening of 3-carbomethoxy-1,2-benzocyclobutene is sufficiently endothermic. We therefore argue that the reverse ring closing reaction is faster than the forward ring opening reaction and, thus, it establishes an equilibrium between the two and subsequently allows formation of the more stable species via outward ring opening reaction. Application of this argument to 3-dimethylaminocarbonyl-1,2-benzocyclobutene explains the predominantly observed inward opening.

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