Thermodynamics of Alkali-Metal Cation Complexation with Calix[4]arene amide derivative

U okviru rada istražena je termodinamika kompleksiranja alkalijskih kationa s amidnim derivatima kaliks[4]arena koji na donjem obodu sadrže triazolne (L) i triazolno-glukozne (l1) podjedinice. Ravnoteže reakcija kompleksiranja proučavane su u acetonitrilu (MeCN), metanolu (MeOH) (spoj L) te N,N-dimetilformamidu (DMF) (oba spoja). Inkluzija molekula otapala u kompleks NaL+ ispitana je u kloroformu. Receptori vrlo dobro vežu alkalijske katione u svim otapalima, a najveći afinitet pokazuju za ion natrija. Reakcije kompleksiranja entalpijski su kontrolirane, a standardna reakcijska entropija pozitivna je samo za kompleksiranje Li+ u acetonitrilu. Vezanje kationa s kaliksarenom L najpovoljnije je u MeCN, a najmanje povoljno u DMF. Termodinamički parametri kompleksiranja u dva otapala upućuju na slab utjecaj glukoznih podjedinica na ravnoteže istraživanih reakcija. Opaženi utjecaj otapala na istražene reakcije može se djelomično protumačiti solvatacijom kationa i inkluzijom otapala u šupljinu kompleksa.The complexation of alkali-metal cations with tertiary-amide lower rim calix[4]arene derivatives containing triazole (L) and triazole-glucose (l1) moities was explored in acetonitrile, methanol (compund L), and N,N-dimethylformamide (both receptors). The solvent inclusion into the cavity of NaL+ was examined in chloroform. The calix[4]arenes bound the cations efficiently with peak affinity for sodium. All reactions were enthalpy controlled, whereas the standard complexation entropy was favourable solely for Li+ complexation in acetonitrile. The affinity of L reduced as follows: MeCN > MeOH > DMF. The thermodynamic complexation parameters with both receptors were highly similar in MeOH and DMF indicating rather weak involvent of glucose subunits into hosting process. The solvent effect on the complexation equilibria could be, partly, rationalized by considering the cation solvation and the affinity of NaL+ for solvent inclusion