Synthesis of Zeolitic Imidazolate Framework-8 Using Glycerol Carbonate.

In this study, we show that glycerol carbonate (GlyC), a bio-based derivative of glycerol, can be used as a suitable green solvent for the synthesis of metal-organic frameworks (MOFs). In particular, a zinc-based zeolitic imidazolate framework-8 (ZIF-8) was synthesized by exploring several different experimental conditions (in terms of temperature, reaction time, and reactants' concentrations) to find that the yield of the reaction and the quality of the products, measured in terms of crystallinity, surface area, and porosity, were in line with those obtained in the most commonly (non-green) used solvents. GlyC was also found to be reusable for several cycles, maintaining the same original quality as a solvent for the synthesis. Finally, some indicators for the assessment of the greenness of a process (E-factor and PMI) revealed a milder environmental impact of GlyC with respect to other solvents.

Non-autonomous zinc-methylimidazole oscillator and the formation of layered precipitation structures in a hydrogel.

Oscillations are one of the intrinsic features of many animate and inanimate systems. The oscillations manifest in the temporal periodic change of one or several physical quantities describing the systems. In chemistry and biology, this physical quantity is the concentration of the chemical species. In most chemical oscillatory systems operating in batch or open reactors, the oscillations persist because of the sophisticated chemical reaction networks incorporating autocatalysis and negative feedback. However, similar oscillations can be generated by periodically changing the environment providing non-autonomous oscillatory systems. Here we present a new strategy for designing a non-autonomous chemical oscillatory system for the zinc-methylimidazole. The oscillations manifested in the periodic change of the turbidity utilizing the precipitation reaction between the zinc ions and 2-methylimidazole (2-met) followed by a partial dissolution of the formed precipitate due to a synergetic effect governed by the ratio of the 2-met in the system. Extending our idea spatiotemporally, we also show that these precipitation and dissolution phenomena can be utilized to create layered precipitation structures in a solid agarose hydrogel.

Application of a chemical clock in material design: chemically programmed synthesis of zeolitic imidazole framework-8.

Here we show a time-programmed and autonomous synthesis of zeolitic imidazole framework-8 (ZIF-8) using a methylene glycol-sulfite clock reaction. The induction period of the driving clock reaction, thus, the appearance of the ZIF-8 can be adjusted by the initial concentration of one reagent of the chemical clock. The autonomously synthesized ZIF-8 showed excellent morphology and crystallinity.

Design of non-autonomous pH oscillators and the existence of chemical beat phenomenon in a neutralization reaction.

The beat in physical systems is a transparent and well-understood phenomenon. It may occur in forced oscillatory systems and as a result of the interference of two waves of slightly different frequencies. However, in chemical systems, the realization of the latter type of the beat phenomenon has been lacking. Here we show that a periodic titration of acid and alkaline solutions with each other using programmable syringe pumps in a continuous stirred-tank reactor exhibits the beat phenomenon in the temporal pH oscillation pattern if the time periods of sinusoidal inflow rates of the reagents are slightly different. Interestingly, the frequency of the chemical beat pattern follows the well-known relationship from physics, namely the frequency of the beat is equal to the absolute value of the difference of the two wave frequencies. Based on our strategy, we can design and engineer non-autonomous pH oscillatory systems, in which the characteristics of the temporal oscillations (amplitude, time period) can easily and precisely be controlled by the experimental conditions such as the inflow rates and feed concentrations. The demonstrated phenomena can be exploited in practical applications, we use the non-autonomous pH oscillators to drive the reversible assembly and disassembly of pH-sensitive building blocks (oleic acid and gold nanoparticles), both highly relevant in nanotechnology and biomedical applications.

Carbon Dioxide-Driven Coupling in a Two-Compartment System: Methyl Red Oscillator.

Strategies for designing autonomous oscillatory systems have gained much attention in the past few decades. A broadly accepted and used strategy for the generation of forced oscillations in the originally non-oscillatory subsystems is to couple a pH (driving) oscillator to a pH-sensitive substance (forced oscillatory subsystem) in a one-compartment system. The forced oscillatory subsystem comprises pH-sensitive components, which inevitably generate negative feedback and affect the characteristics of the driving oscillatory system. Here, we present a different approach by separating the driving and forced oscillatory systems into a two-compartment system using a silicone membrane, and the forced oscillations of the absorbance of a pH-sensitive chemical species (methyl red dye) were realized by the transport of carbon dioxide through the membrane generated periodically by the driving pH oscillator. The transported carbon dioxide produced the pH change in the separated compartment by carbon dioxide-hydrogen carbonate-carbonate equilibria and created forced oscillations of a pH-sensitive chemical species manifested in the oscillation of its absorbance at a fixed wavelength. This approach avoids any feedback from the forced oscillatory system to the driving system via the cross-membrane transport of the chemical species from the forced to the driving oscillatory system. Additionally, we present that this carbon dioxide coupling to the methyl red dye can be used to estimate the carbon dioxide content in both liquid and gas phases.

Copper-Catalyzed Trifluoromethylation of Alkoxypyridine Derivatives.

The trifluoromethylation of aromatic and heteroaromatic cores has attracted considerable interest in recent years due to its pharmacological relevance. We studied the extension of a simple copper-catalyzed trifluoromethylation protocol to alkoxy-substituted iodopyridines and their benzologs. The trifluoromethylation proceeded smoothly in all cases, and the desired compounds were isolated and characterized. In the trifluoromethylation of 3-iodo-4-methoxyquinoline, we observed a concomitant O-N methyl migration, resulting in the trifluoromethylated quinolone as a product. Overall, the described procedure should facilitate the broader use of copper-catalyzed trifluoromethylation in medicinal chemistry.