A Combined Thermodynamic and Computational Study of Alkaline Earth Metal Cations Complexation by a Fluorescent Calix[4]arene Receptor

Usenik, Andrea; Modrušan, Matija; Leko, Katarina; Borovec, Jakov; Marinac, Sven; Hok, Lucija; Cindro, Nikola; Vianello, Robert; Horvat, Gordan; Požar, Josip; Hrenar, Tomica; Tomišić, Vladislav (2025) A Combined Thermodynamic and Computational Study of Alkaline Earth Metal Cations Complexation by a Fluorescent Calix[4]arene Receptor. International Journal of Molecular Sciences, 26 (3). ISSN 1422-0067

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Abstract

Complexation of alkaline earth metal cations with fluorescent tertiary-amide lower-rim calix[4]arene derivative bearing two phenanthridine moieties was studied experimentally (UV spectrophotometry, fluorimetry, isothermal microcalorimetry, NMR spectroscopy) and computationally (classical molecular dynamics and DFT calculations) at 25 °C. The complexation reactions were studied in acetonitrile, methanol, and ethanol, whereby the solvent effect on cation-binding processes was particularly addressed. The complex stability constants and standard reaction thermodynamic quantities (Gibbs energies, enthalpies, and entropies) were determined. The receptor exhibited particularly high affinity towards alkaline earth metal cations in acetonitrile, with peak affinity for Ca2+. The stability of all complexes was significantly lower in ethanol and methanol, where the most stable complex was formed with Sr2+. The decrease in cation-binding abilities was a consequence of the differences in solvation of the reactants and products of the complexation reactions (involving inclusion of the solvent molecule in the calixarene cone), cation charge density, as well as the cation–ligand binding site compatibility. The reactions were enthalpically controlled in acetonitrile, whereas in methanol and ethanol, the binding processes were endothermic and thus entropy driven. The results of 1H NMR measurements, MD simulations, and DFT calculations provided an insight into the structure of the complexes and the corresponding adducts with solvent molecules, as well as the structural aspects behind the differences in complexation thermodynamics. Due to the significant increase in its fluorescence upon cation binding, the studied calixarene derivative was proven to be a promising luminescent sensor for alkaline earth metal cations.

Item Type:	Article
Uncontrolled Keywords:	calixarenes; alkaline earth metal cations; solvent effect; inclusion; fluorescence; thermodynamics
Subjects:	NATURAL SCIENCES > Chemistry
Divisions:	Division of Organic Chemistry and Biochemistry
Projects:	Project title Project leader Project code Project type Centar izvrsnosti u kemiji - CIuK-CIuK Josip Požar; Mirta Rubčić; Ivana Biljan KK.01.1.1.02.0016 EK Metom usmjerena sinteza inhibitora kolinesteraza podržana strojnim učenjem Ines Primožič IP-2022-10-9525 HRZZ Koordinacijske reakcije makrocikličkih liganada u otopini-MacroSol Vladislav Tomišić IP-2019-04-9560 HRZZ Termodinamički, spektroskopski i strukturni aspekti koordinacijskih reakcija kaliksarena Vladislav Tomišić IP-2024-05-3012 HRZZ
Depositing User:	Lorena Palameta
Date Deposited:	25 Feb 2025 08:21
URI:	http://fulir.irb.hr/id/eprint/9587
DOI:	10.3390/ijms26031264

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