Chloroform Solution Research Articles

Microwave Synthesis and Luminescence Efficiencies in Mixed-Ligand Europium Complexes.

The microwave-assisted methodology is now extended and fine-tuned for the synthesis of mixed-ligand europium complexes with an average reaction time of 12 min. Overall, 14 different complexes were synthesized to improve luminescence using our previously proposed strategy to boost luminescence through ligand diversification, specifically by applying it to quaternary europium complexes with at least one DBM (1,3-diphenylpropane-1,3-dionate) ligand. DBM is a strong absorbant of UV radiation that can dissipate energy through nonradiative channels; thus, it is a useful molecular scaffold for sunblockers and cosmetics. Accordingly, the following luminescent tetrakis and quaternary complexes were prepared: K[Eu(DBM)4], K[Eu(β)4], K[Eu(DBM)3(β)], K[Eu(DBM)2(β)2], K[Eu(DBM)2(β)(β')], and the fully mixed complex K[Eu(DBM)(BTFA)(TTA)(HFAC)], where β can be either BTFA (4,4,4-trifluoro-1-phenylbutane-1,3-dionate), TTA (4,4,4-trifluoro-1-(2-thienyl)butane-1,3-dionate), or HFAC (1,1,1,5,5,5-hexafluoropentane-2,4-dionate). For all the complexes, luminescence experiments were performed in chloroform and acetone solutions. Our findings confirm that mixed-ligand complexes exhibit superior quantum efficiencies compared to the average of their homoleptic counterparts. The presence of DBM in the complexes tends to dramatically increase the nonradiative decay rates of the solutions. Finally, we present formulae that provide a detailed understanding of the distinctive roles of each ligand and their relevant interactions in luminescence.

Hydrophobic ion pairing as a novel approach to co-axial electrospraying of peptide-PLGA particles

Electrospraying is a processing technique that has gained much interest to prepare polymeric particles. The technique operates at ambient temperature, thereby avoiding heat induced degradation of labile therapeutics (e.g. peptides and proteins). Exposure to organic solvents can be minimised by co-axial electrospraying through separation of core (aqueous) and shell (organic) solvents. However, aqueous solutions are often difficult to electrospray due to high surface tension. Immiscibility between the core–shell solvents creates a further process challenge. Herein, we describe for the first time the use of hydrophobic ion pairing (HIP) to encapsulate a polypeptide into polymeric particles prepared by co-axial electrospraying. Peptide ion pairs were prepared to incorporate a model peptide – teriparatide – into an organic solvent, permitting facile electrospraying while also protecting the peptide from denaturation. Teriparatide loaded PLGA particles were generated by electrospraying from aqueous or ethanolic peptide solutions (core). A PLGA solution in chloroform (with and without co-solvents) was employed as the shell solution. The aqueous core solution led to a teriparatide encapsulation efficiency of 79.2 ± 19.8 %, which was not significantly different from the ethanolic core (57.1 ± 14.5 %). When aqueous solutions were used the process lacked reproducibility, resulting in low process yields (61.3 ± 4.0 %). In contrast, when an organic core was used a dry powder bed was achieved with a yield of 102.2 ± 8.8 %. The peptide’s integrity and biological functionality were retained after electrospraying as ion pairs, as evidenced in a cell-based PTH1R receptor binding assay.

The unexpected and important role of alcohol stabilizer in thermal cis-trans isomerization of push-pull dyes in chloroform solution

The study demonstrates the influence of ethanol as a stabilizer in chloroform on the thermal cis-trans isomerization kinetics of photochromic compounds based on azobenzene and azopyridine derivatives. The significance of the addition of ethanol as a stabilizer in chloroform-based solutions on the isomerization reaction of the hydroxy- and the 6-hydroxylalkoxy-substituted azo compounds was investigated. The results have revealed that the presence of a polar stabilizer in a solvent can significantly reduce the reaction rate constant of the dark cis-trans isomerization due to the formation of hydrogen bonds at both ends of the azo-chromophore, thereby inhibiting the isomerization. Furthermore, a stabilizer can facilitate the reversion of azo-hydrazone tautomers of azophenols to their azobenzene form, resulting in a decrease in the reaction rate constant. The research presented in this paper can be essential for scientists who study the kinetics of the trans-cis and the cis-trans isomerization reactions of azo-chromophores. The results show that the use of solvents with polar stabilizers should be rather avoided, as their usage without information about stabilizers can lead to different experimental data. The authors should ensure that detailed information about stabilizers used in unstable solvents is included in the experimental section of their works (a detail currently often omitted in the literature).

Probing the Closed Association of Oligoquinoline Foldamers by Time-Resolved Fluorescence Anisotropy.

The metal-mediated dimerization of oligoquinoline foldamers terminated at one end with an oligo(phenylenevinylene) and at the other with a carboxylic acid (OPV-QnA, where n = 4, 8, 17, and 33), and the complexation of OPV-Q8A and Q16A was promoted in chloroform by the addition of a concentrated 16 M aqueous sodium hydroxide solution. UV-vis absorption and time-resolved fluorescence anisotropy (TRFA) experiments were conducted to determine, respectively, the concentration and the average rotational time ⟨ϕ⟩ of the mixture of unassociated and associated foldamers across a range of foldamer concentrations spanning 5 orders of magnitude. Plots of ⟨ϕ⟩ as a function of acid group concentration revealed that ⟨ϕ⟩ increased with increasing foldamer concentration only when the foldamer solution in chloroform was vigorously mixed with the 16 M sodium hydroxide aqueous solution. Furthermore, all plots showed that ⟨ϕ⟩ reached a plateau at high foldamer concentration. The increase in ⟨ϕ⟩ reflected the association of foldamers into larger objects through metal ion coordination with the carboxylate anions generated by deprotonation of the carboxylic acid of OPV-QnA with NaOH, while the plateau obtained at high foldamer concentration indicated that these interactions led to the dimerization of the foldamers via a closed association mechanism. Analysis of the ⟨ϕ⟩ trends yielded the equilibrium constants (K) describing the foldamer dimerization, whose value equaled 1.0 (±0.2) × 106 M-1 for the three longer OPV-QnA foldamers, but was about 10 times smaller for the shortest one (n = 4). Association of OPV-Q8A and Q16A yielded a complex with a ⟨ϕ⟩ matching that of OPV-Q24A, and K for this complexation was similar to that for dimerization. These experiments illustrate the robust nature of TRFA as an experimental method to probe the size of rigid, self-assembled foldamers in solution.

N-Morpholine-N'-benzoylthiourea as an extractant for Pb(II) and Cu(II) in aqueous media: Crystal structure of bis(N-morpholine-N′-4-benzoylthioureato)lead(II)

The reaction of N-morpholine-N′-benzoylthiourea (L: HBMOR) and lead(II) acetate gave a neutral, stable metal(II) complex of type ML2. The Pb(II) complex crystallized in a monoclinic crystal system with P21/n space group. The complex was further characterized by spectroscopic and microanalytic analyses. The solvent extraction behaviors of Pb(II) and Cu(II) ions were investigated in aqueous media containing HBMOR/CHCl3 as extracting reagents. The solvent extraction of Pb(II) and Cu(II) ions from solutions of varying pH, varying concentrations of mineral acids (HCl, HNO3 and H2SO4), varying concentrations of masking agents (EDTA, KCN and KH[C8H6O4]) and varying concentrations of salting-out agents (NaCl, Na2SO4, KNO3) in chloroform solutions of HBMOR were studied. Pb(II) and Cu(II) ions were quantitatively extracted at pH = 7 in 10 min (HCl = 0.01 M) and pH = 8 in 5 min (H2SO4 = 0.01 M), respectively. The Pb(II) ions were quantitatively extracted with minimal interference from EDTA (0.01 M), KCN (0.50 M), and potassium hydrogen phthalate (1.0 M), while the Cu (II) ions were extracted with EDTA (1.0 M), KCN (1.0 M) and potassium hydrogen phthalate (0.01 M). The order of increasing interference for the extraction of Pb(II) and Cu(II) ions was KCN > potassium hydrogen phthalate > EDTA. Sodium sulfate (0.01 M) in HCl enhanced the extraction of Pb(II) ions, while sodium chloride (0.50 M) in HCl enhanced the extraction of Cu(II) ions. pH0.5 values of 0.67 and 2.70 were obtained for Pb(II) and Cu(II) ions, respectively, indicating that the separation of the two metal ions is favorable with HBMOR.

Aromatic (co)polycarbonates bearing pendant 2,3-dimethylmaleimido group based upon a new phthalimidine-containing “cardo” bisphenol

A new “cardo” bisphenol viz., 1-(2-(1,1-bis(4-hydroxyphenyl)-3-oxoisoindolin-2-yl)ethyl)-3,4-dimethyl-1H-pyrrole-2,5-dione (PPH-MA) was synthesized in a two-step reaction sequence starting from phenolphthalein. PPH-MA was utilized as a step-growth monomer for the synthesis of a homo- and fourco-polycarbonates bearing pendant 2,3-dimethylmaleimido groups (PC-MAs) via solution polycondensation of PPH-MA or various mol % compositions of PPH-MA and bisphenol-A, respectively, with triphosgene.1H NMR spectroscopy confirmed the chemical structure and composition of PC-MAs. Inherent viscosity and number average molecular weight values of PC-MAs were in the range 0.45–0.64 dL g−1 and 18,300 − 36,200 g mol−1, respectively, indicating the formation of polymers of medium to reasonably high molecular weights. Tough, transparent and flexible films of PC-MAs could be cast from chloroform solution. X-ray diffraction studies indicated the amorphous nature of PC-MAs. The 10% weight loss temperature (T10) values of PC-MAs were in the range 373–443 °C indicating their good thermal stability.

Electrochemical behavior of mild steel coated with long alkyl-chain benzothiazole derivatives in acid solution: Effect of aliphatic chain length

Mild steel surfaces were coated with four different benzothiazole derivatives with long alkyl chain, namely 2-(heptyl)-benzothiazole (HEBT), 2-(tridecyl)-benzothiazole (TDBT), 2- (pentadecyl)-benzothiazole (PDBT), and 2-(heptadec-8-en-1-yl)benzothiazole (HDBT) from their respective chloroform solutions. Electrochemical experiments were conducted with coated and uncoated mild steel samples exposed to 1 M aqueous HCl at temperatures between 20°C to 50°C and at different immersion times from 6 h to 48 h. TDBT behaves as the best corrosion inhibitor among the four (more than 99 % efficiency at 40°C) and the order of inhibition efficiency follows the trend: TDBT>HDBT>PDBT>HEBT. This reflects the inhibition efficiency to increase with chain length initially, but decreases after a threshold. HDBT, in-spite of having longest aliphatic chain, exhibits better inhibitory performance over PDBT. This is attributed to the presence of unsaturation in HDBT. TDBT coating maintains high corrosion inhibition efficiency even after the 24 h of exposure (above 98 %). Occurrence of spatial hindrance during adsorption of BT derivatives with long aliphatic chain has been manifested by MD simulation.

Aromatic (Co)polycarbonates bearing pendant norbornenyl groups: Synthesis, characterization and post-polymerization modification

A homo- and three co-polycarbonates (PC-NBs) bearing pendant norbornenyl groups were synthesized via solution polycondensation of triphosgene with 4, 4'-(bicyclo (2.2.1) hept-5-en-2 yl methylene) bis (2-methoxyphenol) (BPA-NB) or various mol % compositions of BPA-NB and bisphenol-A, respectively. 1H-NMR spectroscopy confirmed the chemical structure and composition of PC-NBs. Inherent viscosity and number-average molecular weight (Mn) values of PC-NBs were in the range 0.44 – 0.64 dL g−1 and 21,800 – 34,100 g mol−1, respectively, indicating the formation of polymers of medium to reasonably high molecular weights. Tough, transparent, and flexible films of PC-NBs could be cast from chloroform solution. X-Ray diffraction studies indicated the amorphous nature of PC-NBs. Glass transition temperature (Tg) values, determined by DSC analysis, of PC-NBs were in the range 154 – 175°C and Tg values increased with the increase in mol % of BPA-NB. The post-polymerization modification of a representative PC-NB was demonstrated using 3,6-diphenyl-1,2,4,5-tetrazine via tetrazine-ene reaction.

Development of a Molecularly Imprinted Polymer for Determination of Atenolol Based on Selective Solid Phase Extraction and Application in Pharmaceutical Samples

This paper demonstrates the synthesis and storage of molecular-imprinted polymers (MIP) at room temperature using bulk polymerization of atenolol (Ate), which is characterized by high sensitivity, low costs, and high stability. The research used 0.99:6:20 mmol ratios of template, monomer, and cross-linking agents for the polymerization in order to ensure an appropriate adsorption capacity. By making MIP for atenolol as Ate-MIP, which could be looked at with a UV-VIS spectrophotometer at 276 nm, Fourier- transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM), a functional monomer of allyl chloride with cross-linking ethylene glycol dimethyl acrylate was made. Mass spectrometric (MS) detection may use allyl chloride to determine atenolol levels in pharmaceutical preparations. The GC/MS methods developed in this study are accurate, sensitive, and precise and can be easily applied to (NOVATEN/India and ATENOIOI/U.K.) tablets in pharmaceutical preparation. The elution process was applied to the template (Ate) from the Ate-MIP, which developed cavities, caused by using porogenic solutions of methanol, chloroform, and acetic acid (70:20:10, respectively). The maximum adsorption capacity of Ate-MIP was 2.9957 µmol/g, and the ratio of template to monomer was 1:1 in adherence to the Langmuir isotherm model. A solid-phase extraction (SPE) syringe packed with molecular imprinted polymers (MIPs) was used to selectively separate and pre-concentrate Ate from aqueous solutions and estimations of atenolol.

Influence of subphase temperature on Langmuir layers and thin films of A3B-type porphyrine derivative

The influence of aqueous subphase temperature on the formation and stability of floating layers of 5-(4-hydroxyphenyl)-10,15,20-tris(4-hexadecyloxyphenyl)porphyrin (P-OH) was investigated using the Langmuir technology. It was found that the increase in the subphase temperature from 1 to 40 °C leads to a loosening of floating layers (an increase in the area per molecule in the floating layer by ∼15% and a decrease in the surface compression modulus by more than two times). The stability of floating layers (i.e., the ability of a floating layer to maintain its area under the action of a constant compressive force) decreases with increasing subphase temperature. It has been shown that the most stable floating layers are formed at subphase temperatures lower than 30 °C. Monolayer films on solid substrates were obtained using the Langmuir-Schafer technique at subphase temperatures of 1, 10, 20, 30, and 40 °C. The surface relief of these films was studied by atomic force microscopy (AFM). The AFM analysis revealed that the films transferred from the aqueous subphase at a temperature of 20 °C had the highest continuity and the lowest roughness. The absorption spectra of the floating layers were obtained, in which a bathochromic shift of the Soret band and Q-bands were registered (by 19 nm at 20 °C) in comparison with chloroform solution spectrum. This shift is a consequence of the strong intermolecular π–π* interaction, resulting in the formation of J-type aggregates. The Soret band in the spectra of the floating layers shifted from 436 to 441 nm with an increase in subphase temperature from 1 to 40 °C. In the absorption spectra of thin films (8 transfers), the indicated shifts of absorption bands as well as a broadening of the Soret band are preserved. The results of this work can be used in the targeted creation of film samples with specific structure and properties.

Light-Assisted Fabrication of Hierarchical Azopolymer Structures Using the Breath Figure Method and AAO Templates.

Hierarchical polymer structures have garnered widespread application across various fields owing to their distinct surface properties and expansive surface areas. Conventional hierarchical polymer structures, however, often lack postfabrication scalability and spatial selectivity. In this study, we propose a novel strategy to prepare light-assisted hierarchical polymer structures using azopolymers (PAzo), the breath figure method, and anodic aluminum oxide (AAO) templates. Initially, the breath figure PAzo films are prepared by dripping a PAzo chloroform solution onto glass substrates in a high-humidity environment. The AAO templates are then placed on the breath figure PAzo film. Upon ultraviolet (UV) light exposure, the azobenzene groups in the azopolymers undergo trans-cis photoisomerization. This process causes the glass transition temperature (Tg) of the PAzo to become lower than room temperature, allowing the azopolymer to enter the nanopores of the AAO templates. The hierarchical azopolymer structures are then formed by using a sodium hydroxide solution to remove the templates. Furthermore, exploring the effects of PAzo concentration and UV light exposure duration on the film morphology reveals optimized conditions for hierarchical structure formation. Additionally, the water contact angles of these polymer structures are measured. The hierarchical PAzo structures exhibit higher hydrophobicity compared with the flat PAzo films and the PAzo breath figure films. Finally, patterned breath figure films can be prepared using designed photomasks, demonstrating the method's capability for spatial selectivity.

Ultrafast measurement of photoacoustic parameters with mid-infrared frequency comb transients.

The photoacoustic (PA) effect has been widely used in various applications, including highly sensitive spectroscopy and label-free, non-invasive imaging. In this work, we demonstrate a fast and precise measurement of PA parameters for light-absorbing liquids using mid-infrared asynchronous sampling pump-probe measurements. To simulate the observed PA oscillation signals and extract various PA parameters as a function of pump power, we derived analytical solutions of the PA wave equation driven by a train of ultrashort Gaussian pump pulses. By fitting the analytical solution to the measured PA signals using a nonlinear curve fitting method, we could measure the PA parameters, including damping rate, viscosity, and natural frequency. Furthermore, the dynamic response of thermophysical properties of the chloroform solution is also investigated by measuring the variation of the Grüneisen parameter with pump power. We anticipate that this work will open new possibilities for precise in situ measurements of the thermal properties of light-absorbing liquids.

An improved Trizol method for extracting total RNA from Eleutherococcus senticosus (Rupr. & Maxim.) Maxim leaves.

High-quality nucleic acids are the basis for molecular biology experiments. Traditional RNA extraction methods are not suitable for Eleutherococcus senticosus Maxim. To find a suitable method to improve the quality of RNA extracted, we modified the RNA extraction methods of Trizol. Based on the conventional Trizol method, the modified Trizol method 1 and modified Trizol method 2 were used as the control for extraction of RNA from E. senticosus Maxim leaves. The modified Trizol method 1 added β-mercaptoethanol on the conventional Trizol method. After RNA was dissolved, a mixed solution of phenol, chloroform, and isoamyl alcohol was added to denature protein and inhibit the degradation of RNA. The modified Trizol method 2 adds PVPP to grind on the basis of modified Trizol method 1, so as to better remove phenols from leaves, and eliminates the step of incubation at -20°C to reduce extraction time and RNA degradation. Chloroform, CTAB, and CH3COONa were used instead of a phenol, chloroform, and isoamyl alcohol mixed solution to ensure complete separation of nucleic acid from plant tissues and to obtain high-purity RNA. The research results showed that the quality of RNA extracted by conventional Trizol method, modified Trizol method 1, was incomplete, accompanied with different degrees of contamination of polysaccharides, polyphenols, and DNA. The modified Trizol method 2 could better extract RNA from E. senticosus Maxim leaves. The ratio of A260/A280 was in the range of 1.8-2.0, and the yield of RNA was the highest, which was 1.68 and 1.15 times compared with that by conventional Trizol method and modified Trizol method 1 extraction, respectively. The reverse transcription cDNA was further tested through PCR with the specific primers. The amplified fragments are displayed in clear and bright bands in accordance with the expected size. The modified Trizol method 2 could better extract RNA from E.senticosus Maxim leaves. High-quality RNA has more advantages in molecular biology study of E.senticosus Maxim.

Computational insights into solvent polarity associated excited state behaviour for 2-(1H-benzoimidazol-2-yl)−5-diethylamino-phenyl fluorophore

Inspired by the mesmerising charm emanating from the precisely controlled attributes displayed by 2-(1H-benzoimidazol-2-yl)−5-diethylamino-phenyl (HDP) and its derivatives in the domains of photochemistry and photobiology, our present undertaking predominantly focuses on exploring the complexities of light-triggered excited state reactions for HDP fluorophore dissolved in solvents with diverse levels of polarity. Initially, we performed molecular structure optimisation at various stages of the proton transfer process and collected data on bond length, bond angle, and core-valence bifurcation (CVB) index for the molecular framework. Subsequently, infrared (IR) vibrational spectra were analysed to evaluate the reinforcement of hydrogen bonds in different solutions. Furthermore, the investigation of orbital transitions and potential energy curves has led to the conclusion that the ESIPT process of HDP molecules is most likely to occur in nonpolar ccl4 solution, followed by chloroform solution; acetonitrile ranks last. In essence, the nonpolar aprotic solvents are more conducive to facilitating the ESIPT process. This research aims to contribute towards advancements in new luminescent materials and prove valuable in display technology and medical imaging fields while also promoting related technological development.

Electronic Control of Polyproline II Helix Stability via the Identity of Acyl Capping Groups: the Pivaloyl Group Particularly Promotes PPII.

The type II polyproline helix (PPII) is a fundamental secondary structure of proteins, important in globular proteins, in intrinsically disordered proteins, and at protein-protein interfaces. PPII is stabilized in part by n→π* interactions between consecutive carbonyls, via electron delocalization between an electron-donor carbonyl lone pair (n) and an electron-acceptor carbonyl (π*) on the subsequent residue. We previously demonstrated that changes to the electronic properties of the acyl donor can predictably modulate the strength of n→π* interactions, with data from model compounds, in solution in chloroform, in the solid state, and computationally. Herein, we examined whether the electronic properties of acyl capping groups could modulate the stability of PPII in peptides in water. In X-PPGY-NH2 peptides (X=10 acyl capping groups), the effect of acyl group identity on PPII was quantified by circular dichroism and NMR spectroscopy. Electron-rich acyl groups promoted PPII relative to the standard acetyl (Ac-) group, with the pivaloyl and iso-butyryl groups most significantly increasing PPII. In contrast, acyl derivatives with electron-withdrawing substituents and the formyl group relatively disfavored PPII. Similar results, though lesser in magnitude, were also observed in X-APPGY-NH2 peptides, indicating that the capping group can impact PPII conformation at both proline and non-proline residues. The pivaloyl group was particularly favorable in promoting PPII. The effects of acyl capping groups were further analyzed in X-DfpPGY-NH2 and X-ADfpPGY-NH2 peptides, Dfp=4,4-difluoroproline. Data on these peptides indicated that acyl groups induced order Piv- > Ac- > For-. These results suggest that greater consideration should be given to the identity of acyl capping groups in inducing structure in peptides.

Theoretical investigation on diastereoselective [2+2] cycloaddition and Pd-catalyzed enantioselective [3+2] cycloaddition for synthesis of cis-β-lactam and exo-furobenzopyranone

The mechanism is investigated for Wolff rearrangement/Staudinger [2+2] cycloaddition cascade and Pd-catalyzed, decarboxylative, formal [3+2] cycloaddition. Wolff rearrangement of 3-diazotetramic acid is determined to be rate-limiting step generates cyclic acyl ketene. The interaction of ketene with imine firstly results in zwitterion followed by conrotatory cyclization giving major cis-β-lactam. For synthesis of s-VECs, the epoxidation−cyclization cascade and hydrolysis give precursor of better performing exocyclic derivative. The reaction with 3-cyanochromone includes decarboxylation, nucleophilic attack and subsequent ring closure yielding 5-exo-trig furobenzopyranone. Based on the comparison between possible paths, the diastereoselectivity of cis over trans and regio-divergence of 5-exo-trig over 7-endo-trig are both kinetically controlled for [2+2] and [3+2] cycloaddition in common. The positive solvation effect is suggested by decreased absolute and activation energies in chlorobenzene and chloroform solution compared with in gas. These results are supported by Multiwfn analysis on FMO composition of specific TSs, and MBO value of vital bonding, breaking.

A Squaramide-Based Organocatalyst as a Novel Versatile Chiral Solvating Agent for Carboxylic Acids.

A squaramide-based organocatalyst for asymmetric Michael reactions has been tested as a chiral solvating agent (CSA) for 26 carboxylic acids and camphorsulfonic acid, encompassing amino acid derivatives, mandelic acid, as well as some of its analogs, propionic acids like profens (ketoprofen and ibuprofen), butanoic acids and others. In many cases remarkably high enantiodifferentiations at 1H, 13C and 19F nuclei were observed. The interaction likely involves a proton transfer from the acidic substrates to the tertiary amine sites of the organocatalyst, thus allowing for pre-solubilization of the organocatalyst (when a chloroform solution of the substrate is employed) or the simultaneous solubilization of both the catalyst and the substrate. DOSY experiments were employed to evaluate whether the catalyst-substrate ionic adduct was a tight one or not. ROESY experiments were employed to investigate the role of the squaramide unit in the adduct formation. A mechanism of interaction was proposed in accordance with the literature data.

Phenyl-Substituted Cage Silsesquioxane-Based Star-Shaped Giant Molecular Clusters: Synthesis, Properties, and Surface Segregation Behavior.

The crystallinity, solubility, and physical properties of polyhedral oligomeric silsesquioxane (POSS) compounds are highly dependent on their organic substituents. We previously synthesized a series of isobutyl-substituted star-shaped POSS derivatives with aliphatic chain linkers of different length. In this study, we prepared C3- and C6-linked phenyl-substituted star-shaped POSS derivatives (3Ph-C3 and 3Ph-C6) by the hydrosilylation of heptaphenylallyl- and hexenyl-POSS (1a and 1b) and octadimethylsiloxy-Q8-silsesquioxane (Q8M8H) (2), respectively, and their properties were compared with those of the corresponding isobutyl-substituted derivatives (5iBu-C3 and 5iBu-C6). Although 3Ph-C6 was only soluble in chloroform and insoluble in tetrahydrofuran (THF) and toluene, 3Ph-C3 was soluble even in THF and toluene, suggesting that the shorter linkers of the derivative afford a wider range of solvents for dissolution. Differential scanning calorimetry analysis showed that 3Ph-C3 exhibited a baseline shift at 190 °C and an endothermic peak at 316 °C. However, no clear baseline shift was observed for 3Ph-C6. Thermogravimetric analysis showed that the shorter linker in the phenyl-substituted star-shaped POSS derivative significantly increased the decomposition temperature compared with the longer linker. The annealed cast film of 3Ph-C3 at 340 °C above its melting temperature formed a transparent film even after cooling to room temperature. However, an opaque whitish film was formed in the case of 3Ph-C6. Poly(methyl methacrylate) (PMMA) films containing 2 wt % 3Ph-C3 and 3Ph-C6 were prepared by casting their chloroform solutions onto glass substrates overnight at room temperature. The static water contact angle measurements and XPS analysis for the castings film containing 3Ph-C3 and 3Ph-C6 suggested that degree of the segregation amount of 3Ph-C3 was larger than that of 3Ph-C6. The shorter linker length in the phenyl-substituted star-shaped POSS derivative, 3Ph-C3, with its greater predicted solubility in PMMA, exhibited entropy-driven surface segregation.

Systematic Investigation of Optical and Chiroptical Properties of Chiral π‐Conjugated Oligomers in Solution and Thin Films

AbstractFour families of structurally related chiral π‐conjugated oligomers bearing a hydroquinone (HQ), 1,5‐dihydroxynaphthalene (Naph), benzo[1,2‐b:4,5‐b’]dithiophene‐4,8‐diol (BDT) or 9H‐carbazole (CBZ) central core, for a total of 11 new compounds, have been synthesized by simple and versatile synthetic strategies involving Pd‐catalyzed cross‐coupling protocols: a Suzuki‐Miyaura reaction, a Sonogashira/desilylation/Sonogashira sequence or a Sonogashira/desilylation/acyl Sonogashira sequence. A systematic investigation of the optical and chiroptical features of the final chiral dyes was performed in chloroform solution and on spin‐coated thin films. The ECD investigation was crucial in revealing that, even within the same family of organic dyes, minor variations in the nature and length of the π‐conjugated backbone can result in very different solid‐state arrangements at different hierarchical scales.

Photophysics of Benzoxazole and Dicyano Functionalised Diketopyrrolopyrrole Derivatives: Insights into Ultrafast Processes and the Triplet State.

Diketopyrrolopyrrole (DPP) functionalised with an electron donating unit acts as a donor-acceptor molecules that have shown potential for application in dyes and photovoltaics. These molecules offer broad absorption/emission properties and structure-dependent dynamics. In this study, we used femtosecond pump-probe spectroscopy to investigate the photo-initiated dynamics of thiophene linked DPP derivatives. The thio-DPPs are further functionalised by different electrons withdrawing terminal groups, namely benzoxazole and thiophene dicyanide. The benzoxazole derivative is strongly emissive and directly relaxes directly to the ground state chloroform solution. Thiophene dicyanide derivative exhibits distinct spectral evolution in the first 10 ps, associated with structural and vibronic process. Later, it crosses over to the triplet state with a yield of 20 %. In the solid-state (thin film), we observed a signal that resembles singlet fission. However, upon careful analysis of temperature-dependent steady state absorbance spectra, we conclude that these features are due to laser-induced thermal artifacts. We describe a simplified excited state evolution in the thin film that does not include any additional excited states. These findings have significant implications for the analysis of triplet formation, which plays a major role in the photophysics of many organic materials.