In situ Formation of Thermally Stable, Room-Temperature Ionic Liquids from CS₂ and Amidine/Amine Mixtures.

Amidinium dithiocarbamates salts with diverse structures are prepared in situ by adding one equivalent of CS2 to an equimolar mixture of two nonionic molecules, an amidine and an amine. Many of the salts made in this way are room temperature ionic liquids (RTILs) and the others (ILs) melt well below the decomposition temperature of the salts, ca. 80 °C. Unlike the analogous amidinium carbamate RTILs, which are made by adding CO2 to amidine/amine mixtures and decompose near 50 °C, the amidinium dithiocarbamates do not revert to their amidine/amine mixtures when they are heated. The thermal, rheological, conductance, and spectroscopic properties of representative examples from a total of 50 of these ILs and RTILs are reported, comparisons between them and their nonionic phases (as well as with their amidinium carbamates analogues) are made, and the thermolysis pathways of the ammonium dithiocarbamates are investigated

Self-Assembled Fibrillar Networks through Highly Oriented Aggregates of Porphyrin and Pyrene Substituted by Dialkyl l-Glutamine in Organic Media^†

Microfibrous self-aggregation of chromophoric groups of porphyrin and/or pyrene substituted by didodecyl l-glutamic acid in organic media is confirmed by transmission electron microscopic (TEM) observation. Chromophoric probes of porphyrin and pyrene moieties enable evaluation of their assembling behavior photophysically through UV−vis, circular dichroism (CD), and fluorescence spectroscopic characterization. This spectroscopic characterization was able to compensate the lack of TEM observation for the aggregation even at a low concentration below the critical gel concentration. The temperature affects the salient features of the photophysics of porphyrin or pyrene in the microfibrous assemblies. Highly oriented network structures were formed at low temperature since the CD intensities of the porphyrin and pyrene systems increased with lowering the temperature. Fluorescence spectroscopic characterization confirmed the monomer excitation of porphyrin itself, and efficient excimer formation for the pyrene−pyrene charge transfer was detected at low temperature. In particular, we also obtained the preliminary results of fluorescence spectroscopic measurement on singlet−singlet energy migration from pyrene to porphyrin in the mixed assemblies for mimicry of the efficient energy transfer process of the photosynthetic antenna complex

Carbon Dioxide and Molecular Nitrogen as Switches between Ionic and Uncharged Room-Temperature Liquids Comprised of Amidines and Chiral Amino Alcohols

The properties of reversible, room-temperature, chiral, ionic liquids (L-A-C) are reported. They are easily prepared by passing CO2 gas through equimolar mixtures of a simple amidine (L) and a chiral amino alcohol (A), L/A, derived from a naturally occurring amino acid, and they can be returned to their L/A states by passing a displacing gas, N2, through the ionic liquid; the process of passing from uncharged to charged states can be repeated several times without discernible degradation of each phase. All of the 40 L/A combinations examined form room-temperature ionic liquids (most to ca. 50 °C under 1 atm of CO2) and they remain liquids to at least −20 °C. The L-A-C phases are more viscous than their corresponding L/A phases, the conductivities are much higher in the L-A-C phases than in the L/A phases, and the solubility characteristics of the liquids can be modulated significantly by exposing them to either CO2 or N2 gas. The spectroscopic characteristics of the L/A and L-A-C phases have been compared also. Their reversibility, chirality, broad temperature ranges, tolerance to water, and ease of preparation should make the combination of L/A and L-A-C phases useful as solvents for several “green” applications

Reversible, Room-Temperature Ionic Liquids. Amidinium Carbamates Derived from Amidines and Aliphatic Primary Amines with Carbon Dioxide

Reversible, Room-Temperature Ionic Liquids. Amidinium Carbamates Derived from Amidines and Aliphatic Primary Amines with Carbon Dioxid

Reversible, Room-Temperature, Chiral Ionic Liquids. Amidinium Carbamates Derived from Amidines and Amino-Acid Esters with Carbon Dioxide^†

The properties of a new class of chiral, room-temperature, ionic liquids (RTILs) are described. They are made from easily synthesized, readily available materials and can be transformed reversibly to their nonionic liquid states. The nonionic liquids consist of neat equimolar mixtures of a N‘-alkyl-N,N-dimethylacetamidine (L) and an alkyl ester of a naturally occurring amino acid (n). When exposed to 1 atm of CO2 gas, the L/n solutions become cationic−anionic pairs, amidinium carbamates. Of the 50 L/n combinations examined, all except those involving the methyl ester of tyrosine (which was immiscible with the amidines) form RTIL states under CO2 atmospheres, and several remain liquids to at least −18 °C. Heating the ionic liquids in air at ca. 50 °C or bubbling N2 gas through them at ambient temperatures for protracted periods displaces the CO2 and re-establishes the nonionic L/n states. As an example of the changes effected by cycling between the two liquid states, a spectroscopic probe, 1-(p-dimethylaminophenyl)-2-nitroethylene, senses a polarity like that of toluene before a mixture of N‘-octyl-N,N-dimethylacetamidine/isoleucine methyl ester is exposed to CO2 and a polarity like that of N,N-dimethylformamide afterward; whereas a low-polarity solvent, decane, is solublized readily by the nonionic L/n mixture, it is immiscible with the RTIL. Thermal and spectroscopic properties of both the nonionic and ionic phases are reported and compared. Several possible applications for these RTILs can be envisioned because, unlike many other ionic liquids, these need not be prepared and handled under scrupulously dry conditions and they can be cycled repeatedly between high- and low-polarity states