Thermodynamic and structural studies on the complexation of alkali-metal cations with secondary and tertiary calix[4]arene amide derivate in several organic solvents

U okviru ovog rada sustavno je istražen utjecaj otapala na ravnoteže reakcija kompleksiranja sekundarnog i tercijarnog amidnog derivata kaliks[4]arena s kationima alkalijskih metala. Kompleksiranje je proučavano UV-Vis spektrometrijskim i izotermnim mikrokalorimetrijskim titracijama u više organskih otapala, N-metilformamidu (NMF), N,N-dimetilformamidu (DMF) i etanolu (EtOH). Određene su konstante stabilnosti odgovarajućih kompleksa, kao i pripadajuće termodinamičke reakcijske veličine. Na temelju određenih termodinamičkih funkcija otapanja liganda, i literaturnih termodinamičkih podataka solvatacije alkalijskih kationa, izračunane su Gibbsove energije transfera svih sudionika reakcije. Da bi se stekao detaljniji uvid u procese vezanja kationa i molekula otapala s istraživanim spojevima provedene su odgovarajuće računalne simulacije primjenom metode klasične molekulske dinamike. Kaliksaren specifično veže Na+ u svim proučavanim otapalima. Kaliksaren u N-metilformamidu i N,N-dimetilformamidu veže sve katione alkalijskih metala, osim Cs+, dok u etanolu veže samo ione Li+ i Na+. Veća stabilnost kompleksa Na+ u odnosu na komplekse Na+, u svim proučavanim otapalima, objašnjena je preko entalpijskog doprinosa Gibbsovoj energiji kompleksiranja koji je povoljniji kod kaliksarena . U simulacijama molekulske dinamike uočen je proces inkluzije molekula otapala kod svih nastalih kompleksa kaliksarena i 2. (80The effect of the solvent on the complexation reactions of a lower-rim calix[4]arene secondary and tertiary amide derivatives (, ) with alkali-metal cations was systematically investigated. Cation complexation was explored by means of UV-Vis spectrophotometric and isothermal microcalorimetric titrations in N-methylformamide (NMF), N,N-dimethylformamide (DMF), and ethanol (EtOH). The stability constants of the complexes, as well as the corresponding thermodynamic reaction quantities, were determined from the obtained experimental data. Using the experimentally determined ligand solubilities and literature data of cation solvation thermodynamics, transfer Gibbs energies of all reaction participants were calculated. To get more detailed insight into the binding of cations and solvent molecules by the investigated calix[4]arenes, molecular dynamics simulations were carried out. Calixarene specifically binds Na+ in all solvents examined. In N-methylformamide and N,N-dimethylformamide calixarene binds all examined alkali metals, apart from Cs+, while in ethanol it only binds Li+ and Na+. Larger stability of calixarene Na+ complex then that of Na+ complex in all solvents studied, was explained by enthalpic contribution to the Gibbs energy of complexation, which is more favorable in case of complexes of ligand . In molecular dynamics simulations the inclusion of solvent molecules was observed for all complexes of ligands and 2