We
demonstrate the potential use of 1,1′-bis(2-(cyclohexyloxy)-2-oxoethyl)-[4,4′-bipyridin]-1,1′-diium
bromide (BP) and 1-ethyl-3-methylimidazolium chloride (EMI)
ionic liquids (ILs) in in situ synthesis of gold nanoparticles (Au
NPs) without using any external reducing or stabilizing agents. Both
ILs produced nearly monodisperse NPs of 4–8 nm which were present
in the form of self-assembled states. BP coated NPs formed self-assembled
sheets and easily transferred to the organic phase by employing the
water insoluble IL as a phase transfer agent. The efficiency of the
phase transfer process was related to the extent of aggregation as
well as functional groups. Both IL coated NPs were further used to
extract the proteins from the complex biological mixtures. EMI coated
NPs extracted proteins of large molar masses whereas BP coated NPs
were good for the extraction of low molecular mass proteins. This
disparity was controlled by the substituted functional groups of ILs.
Bulky cyclohexyloxy functional groups of BP did not allow extraction
of large molar mass proteins. Such a wide applicability of ILs in
nanomaterials synthesis opens several new applications in the field
of nanomedicine and nanobiotechnology where IL coated NPs can be used
for diverse protein complexation.
Cyclohexyloxyoxoethylbipyridinium gemini amphiphiles have been synthesized in a two-step methodology. In the first step, cyclohexanol was esterified with chloroacetic acid or bromoacetic acid to get cyclohexyl-2-chloro (or bromo) ethanoates (3a/3b). These esters in the second step were reacted with either 4,4′-bipyridine or 2,2′-bipyridine to get the respective bipyridinium salts. The structure of these amphiphiles has been established by infrared (IR) spectroscopy, nuclear magnetic resonance (NMR), and mass spectroscopy. The interfacial parameters like counterion binding (β), maximum surface excess concentration (Γ max ), minimum area per molecule (A min ) of gemini amphiphiles have been evaluated and compared with single-tailed amphiphiles. A comparison of the critical micelle concentration (CMC) value of these gemini amphiphiles with corresponding single-tailed amphiphiles indicates that the geminis have CMC values 10-fold less than that of the single-tailed amphiphiles. The corresponding hexafluorophosphate and tetrafluoroborate gemini amphiphiles were also prepared. The melting points of monomeric and gemini amphiphiles has also been compared.■ EXPERIMENTAL SECTION Materials. Cyclohexanol, chloroacetic acid, bromoacetic acid, 4,4′-bipyridine and 2,2′-bipyridine were purchased from Central Drug House (New Delhi, India) and used as received.
TABLE OF CONTENT Graphs of specific conductivity vs concentration NMR, Mass and IR spectra of ionic liquids Graph of thermal stability and X-Ray crystallographic data of ionic liquids 1 H spectra of N-(cyclohexanoxycarbonylmethyl)pyridinium bromide (9a) 13 C spectra of N-(cyclohexanoxycarbonylmethyl)pyridinium bromide (9a)6 13 C spectra of 3-methyl-N-(cyclohexanoxycarbonylmethyl)imidazolium bromide (13a) 13 C DEPT spectra of 3-methyl-N-(cyclohexanoxycarbonylmethyl)imidazolium bromide (13a)
In this work, 1-halo-3-(cyclohexyloxy)propan-2-ol (3a/3b) were reacted with N-methylimidazole (4) or pyridine (5) to yield the respective 3-(3-(cyclohexyloxy)-2hydroxypropyl)-1-methyl-1H-imidazol-3-ium (6a/6b) or pyridinium (7a/7b) surface-active ionic liquids (SAIL). The self-aggregation behavior of these ionic liquids (IL) was evaluated by conductometric and tensiometric methods. The thermal stability and size of the micelles were determined by thermogravimetric analysis and dynamic light scattering studies, respectively. The investigated IL were found to exhibit very low cytotoxicity as evaluated by MTT (3-(4, 5dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) assay on the C6 glioma cell line, indicating that the investigated SAIL can be considered for biological applications like drug and gene delivery. The conventional IL 3-methyl-1-octyl imidazolium bromide (C 8 mimBr) was used for comparison in property evaluations.
A library of imidazolium‐based gemini cationic bola amphiphiles was synthesized using a regioselective ring‐opening reaction of glycidyl phenyl ether with imidazole under solvent‐free conditions. The corresponding hexafluorophosphate (PF6−) and tetrafluoroborate (BF4−) counterion‐containing amphiphiles were also synthesized and characterized using nuclear magnetic resonance (NMR) and mass spectroscopy. The micellar and interfacial parameters like the critical micelle concentration (CMC), surface pressure at the CMC (Пcmc), surface tension at CMC (
γcmc), counterion binding (β), maximum surface excess concentration (
Γmax), minimum area per molecule (
Amin), standard free energy of micellization (normalΔGmic0) and adsorption (normalΔGads0), and Kraft temperature were evaluated using surface tension and conductometry methods in aqueous solution as well as in buffer solution. Dynamic light scattering (DLS) was used to determine the size of the micelles formed in the aqueous solution. Cytotoxicity tests were carried out on the C6 glioma cancerous brain cell line using the MTT assay (3‐(4, 5‐dimethylthiazole‐2‐yl)‐2, 5‐diphenyltetrazolium bromide) to evaluate the IC50 value of all the synthesized amphiphiles. Thermal stability of these amphiphiles was also evaluated using a thermal gravimetric analyzer (TGA). Economic way of synthesis, moderate thermal stability, a low value of CMC, and cytotoxicity of these amphiphiles will inspire new research in the field of nanobiotechnology and pharmaceutical industries.
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