Title Termodinamika inkluzijskih reakcija amfifilnih spojeva s ciklodekstrinima i kukurbiturilima Title (english) Thermodynamics of inclusion reactions of amphiphilic compounds with cyclodextrins and cucurbiturils Author Andrea Usenik Mentor Josip Požar (mentor)Committee member Ivana Biljan (predsjednik povjerenstva)Committee member Gordan Horvat (član povjerenstva)Committee member Ana Budimir (član povjerenstva)Granter University of Zagreb Defense date and country 2023-12-20, Croatia Scientific / art field, NATURAL SCIENCES Universal decimal classificationUDC ) 54 - Chemistry. Crystallography. Mineralogy Abstract Razumijevanje termodinamike inkluzije nepolarnih funkcionalnih skupina u ciklodekstrine i kukurbiturile
otvara put za dizajn novih makrocikličkih receptora, omogućuje njihovu širu industrijsku primjenu te pruža
uvid u hidrataciju lipofilnih gostiju i šupljina navedenih receptora. S ciljem rasvjetljavanja utjecaja strukture
gosta, temperature i otapala na kompleksiranje amfifilnih alifatskih i aromatskih spojeva te njihovih
hidrofobnih analoga s ciklodekstrinima i kukurbiturilima, pripadne su reakcije karakterizirane
mikrokalorimetrijski u širokom temperaturnom rasponu (278 ≤ T / K ≤ 338), a struktura nastalih kompleksa
u otopini istražena je spektroskopijom NMR.
Afinitet kukurbiturila prema svim gostima, s iznimkom 1‑naftola u vodi, zamjetno je veći u
usporedbi s ciklodekstrinima s jednakim brojem monomernih podjedinica. To je u svim slučajevima
posljedica izrazito egzotermnog kompleksiranja s glikolurilnim receptorima, a sustavna kalorimetrijska
istraživanja inkluzije također su ukazala na entropijski nepovoljniju dehidrataciju šupljine kukurbiturila.
Reakcijski toplinski kapaciteti su za veliku većinu reakcija kompleksiranja u vodi negativni, što dovodi do
izražene temperaturne entalpijsko-entropijske kompenzacije. Opažene ovisnosti ΔrH°(T) i ΔrS°(T) u najvećoj
su mjeri uzrokovane promjenama u organizaciji vode oko nepolarnih funkcionalnih skupina gostiju i mogu
se protumačiti njihovim kozmotropnim utjecajem na otapalo pri nižim, odnosno kaotropnim pri višim
temperaturama. Navedena činjenica znatno utječe na termodinamiku inkluzije u ciklodekstrine koja je u
većini slučajeva pri 278 K entropijski kontrolirana. Inkluzija alifatskih derivata u β-ciklodekstrin entropijski
je favorizirana, a u kukurbit[7]uril entalpijski, pri čemu je afinitet oba receptora prema tim gostima veći u
usporedbi s aromatskim analozima. Za razliku od vode, reakcije kompleksiranja u formamidu i etilen‑glikolu
su entalpijski kontrolirane, a ΔrH° gotovo neovisna o temperaturi. Posljedično, iako solvofobna inkluzija nije
ograničena na vodu, temperaturna ovisnost pripadnih termodinamičkih parametara kompleksiranja
posljedica je njezinih specifičnih solvatacijskih svojstava.
Abstract (english) Understanding the thermodynamics of non‑polar functionalities’ inclusion within cyclodextrins and cucurbiturils paves the way for the design of new macrocyclic receptors, enables their wider industrial application, and provides insights into the hydration of lipophilic guests and cavities of these receptors. To shed light on the influence of guest structure, temperature, and solvent on the complexation of amphiphilic aliphatic and aromatic compounds and their hydrophobic analogs with cyclodextrins and cucurbiturils, the corresponding reactions were characterized microcalorimetrically in a wide temperature range (278 ≤ T / K ≤ 338), and the structure of the resulting complexes was investigated by NMR spectroscopy.
The affinity of cucurbiturils towards all guests, with the exception of 1‑naphthol in water, is noticeably higher compared to cyclodextrins with an equal number of monomeric subunits. This is in all cases due to extremely exothermic complexation with glycoluryl receptors, whereby systematic calorimetric studies of inclusion also indicate the entropically less favorable dehydration of the cucurbituril cavity. Reaction heat capacities are negative for most complexation reactions in water, which leads to pronounced temperature enthalpy-entropy compensation. The observed ΔrH°(T) and ΔrS°(T) dependencies are largely due to changes in the organization of water around nonpolar guest functionalities and can be interpreted by their cosmotropic effect on the solvent at lower, and kaotropic at higher temperatures. This significantly affects the thermodynamics of inclusion within cyclodextrins, which is in most cases entropically controlled at 278 K. The inclusion of aliphatic derivatives is entropically favored compared to their aromatic analogues in the case of β-cyclodextrin, and enthalpically favored in the case of cucurbit[7]uril. This results in higher affinity for aliphatic guests in both cases. Unlike in water, the complexation reactions in formamide and ethylene glycol are enthalpically controlled, and ΔrH° almost independent of temperature. Consequently, although solvophobic inclusion is not a water-limited phenomenon, the temperature dependence of the corresponding thermodynamic complexation parameters is due to its specific solvation properties.
Keywords
amfifilni spojevi
ciklodekstrini
kalorimetrija
kukurbiturili
termodinamika
Keywords (english)
amphiphilic compounds
cyclodextrins
cucurbiturils
hydrophobic effect
thermodynamics
Language croatian URN:NBN urn:nbn:hr:217:563516 Promotion 2024 Project Number: IP-2019-04-9560 Study programme Title: Doctoral study Type of resource Text Extent 120, XCIX str. ; 30 cm File origin Born digital Access conditions Embargoed access Terms of use Created on 2024-01-09 13:51:59
