Theoretical studies on Ru(fppz)2(CO)L (L = N -heterocyclic ligand): Electronic structure, absorption, phosphorescence, and solvatochromism

A series of ruthenium(II) complexes Ru(fppz)₂(CO)L [fppz = 3-trifluoromethyl-5(2-pyridyl)pyrazole; L = pyridine (1), 4-dimethylaminopyridine (2), 4-cyanopyridine (3)] were designed and investigated theoretically to explore their electronic structures, absorption, and emissions as well as the solvatochromism. The singlet ground state and triplet excited state geometries were fully optimized at the B3LYP/LANL2DZ and CIS/LANL2DZ level, respectively. The HOMO of 1–3 is composed of d_yz(Ru) atom and π(fppz). The LUMO of 1 and 2 is dominantly contributed by π*(fppz) orbital, but that of 3 is contribute by π*(L). Absorption and phosphorescence in vacuo, C₆H₁₂, and CH₃CN media were calculated using the TD-DFT level of theory with the PCM model based on the optimized ground and excited state geometries, respectively. The lowest-lying absorption of 1 and 2 at 387 and 391 nm is attributed to {[d_yz(Ru) + π(fppz)] → [π*(fppz)]} transition, but that of 3 at 479 nm is assigned to {[d_yz(Ru) + π(fppz)] → [π*(L)]} transition. The phosphorescence of 1 and 2 at 436 and 438 nm originates from ³{[d_yz(Ru) + π(fppz)] [π*(fppz)]} excited state, while that of 3 at 606 nm is from ³{[d_yz(Ru) + π(fppz)] [π*(L)]} excited state. The calculation results showed that the absorption and emission transition character can be changed from MLCT/ILCT to MLCT/LLCT transition by altering the substituent on the L ligand. The phosphorescence of 1 and 2 does not have solvatochromism, but that of 3 at 606 nm (vacuo), 584 nm (C₆H₁₂), and 541 nm (CH₃CN) is strongly dependent on the solvent polarity, so introducing electron-withdrawing group on ligand L will induce remarkable solvatochromism. Supported by the National Natural Science Foundation of China (Grant Nos. 20573042, 20703015, and 20333050)     

Precipitation polymerization in acetic acid: synthesis of monodisperse cross-linked poly(divinylbenzene) microspheres

This paper reports two important results with cross-linked precipitation polymerization. (1) Acetonitrile, a substance harmful to human health, is the most commonly used solvent for the synthesis of cross-linked polymeric microspheres by precipitation polymerization. Here, the much safer acetic acid replaced acetonitrile as a solvent in the precipitation polymerization of monodisperse cross-linked poly(divinylbenzene) (PDVB-55) microspheres. Pumpkin-like particles and microspheres were obtained. XPS results displayed a significant amount of double bonds on the surface of the particles. The effect of monomer content, temperature, and initiator amount on the formed particles were studied. For a DVB loading below 1 vol % at 70 degrees C, monodisperse microspheres with smooth surfaces and narrow diameters were successfully obtained. With a DVB loading of 2 vol % and by observing the shapes of particles obtained with three different temperature(60, 70, and 80 degrees C), we found that more spherical particles were obtained at higher temperatures and pumpkin-like particles were obtained at lower temperatures. No significant differences in morphology or the coefficient of variation (CV) of the particles were obtained for different initiator loadings, whereas the particle diameters could be increased with increased initiator concentrations. (2) In order to obtain a better understanding of the formation mechanism of these particles, time-dependent experiments, for the first time, were conducted in a hydrophobic monomer system. By tracing the whole polymerization process, some important results were found. First, with the polymerization time at 70 degrees C, the particle diameters were found to increase from 800 nm to 3.0 microm, the CV displayed a decrease, and the amount of spheres and the spherical evenness of the particle surfaces improved. Second, by quantitatively calculating the particle number from the yields and diameters data, it is found that starting from 3.1% yield or two hours reaction time the total amount of particles in the system is almost a constant (about 9.6 x 10 (8)/L), which means that no homocoagulation occurred and no new particles were generated after nucleation, and there is a linear relation between cubic diameters and yields. These two results give us a distinct impression that particle growth almost comes from capturing of newly formed oligomers. Based on the above results, a scheme for the particle formation is proposed, which shows that that pumpkin-like particles are caused by a prolonged nucleation including the homocoagulation of primary nuclei. The growth of the particles includes two modes, an in situ surface polymerization of monomer and the adsorption of PDVB-55 oligomers. The differences between results in acetonitrile and in acetic acid (higher yields, smaller size, not spherical but pumpkin-like particles in acetic acid) were due to the lower solubilizability of acetic acid which is the so-called proton-containing solvent with the hydrogen bonding structure.     

Highly Efficient Circularly Polarized Luminescence from Chiral Au13 Clusters Stabilized by Enantiopure Monodentate NHC Ligands

Chiral Au nanoclusters have promising application prospects in chiral sensing, asymmetric catalysis, and chiroptics. However, enantiopure superatomic homogold clusters with crystallographic structures emitting bright circularly polarized luminescence (CPL) remain challenging. In this study, we designed chiral N-heterocyclic carbenes (NHCs), and for the first time enantioselectively synthesized a pair of monovalent cationic superatomic Au₁₃ clusters. This new enantiomeric pair of clusters has a quasi-C₂ symmetric core and exhibited CPL with an unprecedent solution-state quantum yield (QY) of 61 % among those of the atomically precise Au nanoclusters. DFT calculations provided insights into the circular dichroism behavior, and revealed the origin of CPL from superatomic Au clusters. This work opens a new avenue for developing novel homochiral nanoclusters using chiral NHC ligands and provides fundamental understanding of the origin of the chiroptics of metal clusters.     

Interaction between cetyltrimethylammonium bromide and β-cyclodextrin: surface tension and interfacial dilational viscoelasticity studies

The interaction between cetyltrimethylammonium bromide (CTAB) and β-cyclodextrin (β-CD) was studied via surface tension and dilational viscoelasticity methods. The effect of sodium bromide and sodium chloride on the interaction between CTAB and β-CD were studied as well. The surface tension isotherms provided a series of parameters, including apparent critical micelle concentration (cmc*), surface tension at the cmc* (γ_cmc), stoichiometry of the complex (R), and the efficiency of adsorption (pC ₂₀ ). The addition of NaBr and NaCl decreases the cmc* of CTAB/β-CD solution. CTAB molecules enter the cavities of β-CD molecules thus formed both 1:1 and 1:2 inclusion complexes. From the change of γ_cmc, it can be seen that the CTAB/β-CD complexes (1:1) act as short-chain alcohol, which decrease γ_cmc, but the depression of cmc* is too small to be detected. R first decreases then increases as a function of NaBr and NaCl. Compared to NaCl, NaBr increases R more efficiently. The presence of NaBr and NaCl increases pC ₂₀ of CTAB/β-CD solution. The results obtained from the dilational viscoelasticity measurements at low dilational frequencies (0.005–0.1 Hz) reveal that the dilational modulus passes through a maxium value with increasing concentration of β-CD at a given concentration of CTAB. The addition of both NaBr and NaCl decreases the dilational modulus of a given concentration CTAB/β-CD solution. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Biphasic drug release: permeability and swelling of pectin/ethylcellulose films, and in vitro and in vivo correlation of film-coated pellets in dogs

The major objectives of this study were i) to evaluate the permeability and swelling characteristics of isolated films prepared by mixing of pectin with ethylcellulose; and ii) to assess the absorption and in vitro/in vivo correlation (IVIVC) of 5-FU film-coated colon-targeted pellets in dogs. Free films were prepared by casting and solvent evaporation method. These free films were evaluated by swelling experiment and permeability to 5-FU in different media. Pectin/ethylcellulose films had suitable characteristics for colonic delivery; and when the addition of pectin was up to the ratio of 30%, the swelling and permeability of the mixed films was significantly increased in the simulated colonic fluid (SCF). Pharmacokinetic study in dogs gave Tmax/Cmax of 14 h/1.6 microg/ml and 16 h/1.7 microg/ml for total weight gain (TWG)-22% and 18% coated pellets, respectively. The plasma 5-FU levels of the TWG-22% and 18% coated pellets were maintained at a much lower level with a mean residence time (MRT) of 18-20 h, longer than 2.1 h for 5-FU uncoated pellets, confirming delayed absorption. There was no statistically significant difference in the area under the plasma concentration vs. times curve (AUC) values between the uncoated pellets and the coated pellets. Moreover, a good linear regression relationship was observed between the percent in vitro dissolution in SCF and the percent absorption or percent AUC. It was concluded that i) pectin within the mixed films were susceptible to colonic enzymes, and the film-coated pellets are potentially useful for colonic drug delivery; and ii) in vitro dissolution testing in SCF could be used to establish certain IVIVC for the colon-specific drug delivery systems activated by microflora.     

Light-Activated Assembly of DNA Origami into Dissipative Fibrils

Hierarchical DNA nanostructures offer programmable functions at scale, but making these structures dynamic, while keeping individual components intact, is challenging. Here we show that the DNA A-motif—protonated, self-complementary poly(adenine) sequences—can propagate DNA origami into one-dimensional, micron-length fibrils. When coupled to a small molecule pH regulator, visible light can activate the hierarchical assembly of our DNA origami into dissipative fibrils. This system is recyclable and does not require DNA modification. By employing a modular and waste-free strategy to assemble and disassemble hierarchical structures built from DNA origami, we offer a facile and accessible route to developing well-defined, dynamic, and large DNA assemblies with temporal control. As a general tool, we envision that coupling the A-motif to cycles of dissipative protonation will allow the transient construction of diverse DNA nanostructures, finding broad applications in dynamic and non-equilibrium nanotechnology.     

Constructing Intrapenetrated Hierarchical Zeolites with Highly Complete Framework via Protozeolite Seeding

Creation of intrapenetrated mesopores with open highway from external surface into the interior of zeolite crystals are highly desirable that can significantly improve the molecular transport and active sites accessibility of microporous zeolites to afford enhanced catalytic properties. Here, different from traditional zeolite-seeded methods that generally produced isolated mesopores in zeolites, nanosized amorphous protozeolites with embryo structure of zeolites were used as seeds for the construction of single-crystalline hierarchical ZSM-5 zeolites with intrapenetrated mesopores (mesopore volume of 0.51 cm³ g⁻¹) and highly complete framework. In this strategy, in contrast to the conventional synthesis, only a small amount of organic structure directing agents and a low crystallization temperature were adopted to promise the protozeolites as the dominant growth directing sites to induce crystallization. The protozeolite nanoseeds provided abundant nucleation sites for surrounding precursors to be crystallized, followed by oriented coalescence of crystallites resulting in the formation of intrapenetrated mesopores. The as-prepared hierarchical ZSM-5 zeolites exhibited ultra-long lifetime of 443.9 hours and a high propylene selectivity of 47.92 % at a WHSV of 2 h⁻¹ in the methanol-to-propylene reaction. This work provides a facile protozeolite-seeded strategy for the synthesis of intrapenetrated hierarchical zeolites that are highly effective for catalytic applications.     

pH Responsive Poly(Amino Acid) Nanoparticles as Potent Carrier Adjuvants for Enhancing Cellular Immunity

Adjuvants are widely used in vaccine to improve the protection or treatment efficacy. However, so far they inevitably produce side effects and are hard to induce cellular immunity in practical application. Herein, two kinds of amphiphilic poly(glutamic acid) nanoparticles (α-PGA-F and γ-PGA-F NPs) as nanocarrier adjuvants are fabricated to induce an effective cellular immune response. Amphiphilic PGA are synthesized by grafting phenylalanine ethyl ester to form biodegradable self-assembly nanoadjuvants in a water solution. The model antigen, chicken ovalbumin (OVA), can be loaded into PGA-F NPs (OVA@PGA-F NPs) with the high loading ratio >12%. Moreover, compared with γ-PGA-F NPs, the acidic environment can induce the α-helical secondary structure of α-PGA NPs, promoting membrane fusion and more fast antigen lysosomal escape. Hence, the antigen presenting cells treated with OVA@α-PGA-F NPs show higher secretion of inflammatory cytokines, and higher expression of major biological histocompatibility complex class I and CD80 than those of OVA@γ-PGA-F NPs. Overall, this work indicates that pH responsive α-PGA-F NPs as a carrier adjuvant can effectively improve the ability of cellular immune responses, leading to it being a potent candidate for vaccine applications.     

Linking routines to the evolution of IT capability on agent-based modeling and simulation: a dynamic perspective

IT capability as an important source of competitive advantage has been strongly emphasized in the strategic management literature, yet the formation and evolution of IT capability in the ever-changing business environment are not well explained. To fill this gap, this paper takes routine as the unit of analysis, depicts a micro-interpretation of the formation and evolution of IT capabilities from the routine-based and dynamic perspective, and uses the agent-based simulation methodology to simulate the evolutionary process of IT capability as well as to identify the underlying principles. In order to provide a better presentation of the evolutionary process, a routine-based view of the enterprise explicitly recognizes relationships of IT resources and capabilities. The simulation results show that the evolution of IT capability is a dynamic adaption and learning process. From the routine-based view, the evolution of IT capability is indeed the process of variation, selection, and retention for IT routines.