Naslov
Complexation of Alkali-Metal Cations by Lower-Rim Calix[4]arene Phenanthridine Derivatives

Autori
Tranfić Bakić, Marina ; Hrenar, Tomica ; Horvat, Gordan ; Požar, Josip ; Frkanec, Leo ; Tomišić, Vladislav

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
International MacroTrend Conference on Medicine, Science and Technology : Program and Conference Proceedings / - Austin (TX) : Macrojournals, 2015

Skup
International MacroTrend Conference on Medicine, Science, and Technology

Mjesto i datum
Sjedinjene Američke Države, 28.12.2015. - 29.12.2015

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Calixarenes ; Alkali-metal cations ; Complexation ; Thermodynamics ; Fluorescence

Sažetak
Calixarenes are macrocyclic oligomers which consist of four or more phenolic residues linked by methylene groups in the ortho position. Many calixarene derivatives are known to be very efficient and, in some cases, selective binders of ions and neutral molecules.1 In the present work the comprehensive thermodynamic and computational studies of the alkali-metal cations binding with fluorescent phenanthridine-based calix[4]arene derivatives 1 and 21 (Figure 1) were carried out in order to get as detailed as possible insight into the corresponding complexation reactions. The solvent effect on these processes was particularly addressed by using acetonitrile/dichloromethane and methanol/dichloromethane mixtures (φ = 0.5) as solvents. The fluorescence of the studied compounds was shown to be considerably influenced by metal-ion binding which makes them candidates for highly sensitive cation sensors. The stability constants of the M1+ and M2+ (M denotes alkali metal) complexes were determined at 25 °C by means of fluorimetric, spectrophotometric, potentiometric, and microcalorimetric titrations. The latter technique also provided information on reaction enthalpies and entropies. The ligands structural changes taking place upon complexation were followed by NMR spectroscopy. Tetra-phenanthridine derivative 1 was found to be a quite good binder of all investigated cations (except of the largest Cs+) in both investigated solvents, whereas the affinity of compound 2 towards alkali-metal ions was significantly lower. The complex stabilities were much higher in MeCN/CH2Cl2 mixture as compared to MeOH/CH2Cl2. These findings could be explained by taking into account the determined thermodynamic complexation data, structural properties of the ligand and free and complexed cations, as well as the solvation abilities of the solvents examined. The conclusions made on the basis of the experimental results were supported by the molecular dynamics simulations of the systems studied. In addition, an attempt to get an insight into the possible structures of the alkali-metal cation complexes with ligand 1 was made by carrying out the detailed search of the conformational space on the semiempirical level, followed by the DFT optimization of the local-minima-corresponding structures.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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