20.500.12556/DKUM-94524 VPLIV METODE IN BAZNEGA SETA NA IZRAČUN SPEKTRA UV/VIS IN ECD diplomsko delo univerzitetnega študijskega programa I. stopnje THE INFLUENCE OF METHOD AND BASIS SET ON THE CALCULATION OF UV/VIS AND ECD SPECTRA V diplomskem delu sem preučevala spektroskopske lastnosti kohumulona, ene od glavnih grenkih komponent v hmelju (Humulus lupulus). Namen raziskave je bil ugotoviti, kako izbira kvantno-kemijske metode in baznega seta vpliva na natančnost simuliranih spektrov ter njihovo ujemanje z eksperimentalnimi podatki. Študija se osredotoča na vpliv štirih gostotnih funkcionalov (B3LYP, CAM-B3LYP, M06-2X in ωB97XD) in dveh baznih setov (6 311++G(d,p) ter def2TZVP) na kakovost napovedanih spektrov. Najprej sem pomerila spektra UV/VIS in CD vodne raztopine kohumulona pri nizki vrednosti pH, s čimer sem zagotovila, da je kohumulon v raztopini v obliki polno protonirane zvrsti. Nato sem izvedla konformacijsko analizo kohumulona, identificirala 13 energetskih minimumov ter jih optimizirala z metodami DFT. Na podlagi Gibbsovih prostih energij in Boltzmannove porazdelitve sem izbrala šest najverjetnejših konformer, ki so skupaj predstavljali več kot 99 % populacije. S pomočjo metode TD-DFT sem za te konformere izračunala elektronske prehode ter ustvarila simulirane spektre UV/VIS in ECD z uporabo programa GaussSum. Nato sem izračunane spektre primerjala z eksperimentalnimi. Rezultati kažejo, da izbira metode pomembno vpliva tako na geometrijo kot tudi na porazdelitev konformacij in intenziteto spektralnih pasov. Raziskava potrjuje, da premišljena izbira računske nastavitve bistveno izboljša interpretacijo eksperimentalnih spektrov in omogoča zanesljiv opis spektralnih lastnosti kompleksnih naravnih spojin, kakršna je kohumulon. In my Bachelor thesis, I investigated the spectroscopic properties of cohumulone, one of the main bitter compounds in hops (Humulus lupulus). The aim of the study was to determine how the choice of quantum chemical method and basis set affects the accuracy of simulated spectra and their agreement with experimental data. The study focuses on the impact of four functionals (B3LYP, CAM-B3LYP, M06-2X, and ωB97X-D) and two basis sets (6 311++G(d,p) and def2-TZVP) on the quality of the predicted spectra. Initially, I recorded the UV/VIS and CD spectra of an aqueous solution of cohumulone at low pH to ensure that the compound was present in its fully protonated form. Subsequently, I performed a conformational analysis of cohumulone, identifying 13 energy minima, which were then optimized using DFT methods. Based on Gibbs free energies and Boltzmann population analysis, I selected the six most probable conformers representing more than 99% of the population. Using the TD-DFT approach, I calculated the electronic transitions for these conformers and generated simulated UV/VIS and ECD spectra with the GaussSum program. These calculated spectra were then compared with the experimental data. The results show that the choice of method significantly affects both the geometry and conformational distribution as well as the intensity of spectral bands. The study confirms that a careful selection of computational parameters substantially improves the interpretation of experimental spectra and enables a reliable description of the spectroscopic properties of complex natural compounds such as cohumulone. hmelj kohumulon konformacije spektroskopija UV/VIS CD gostotni funkcional bazni set hops cohumulone conformations spectroscopy UV/VIS CD density functional basis set true true false [L. Novak] Slovenski jezik Angleški jezik Diplomsko delo/naloga 2025-08-20 12:00:17 2025-09-18 15:21:34 2025-10-01 03:14:53 0000-00-00 00:00:00 2025 0 Maribor 0 Maribor 1 spletni vir (1 datoteka PDF (VIII, 39 f.)) 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 543.42:633.791(043.2) 251000323 VS_Novak_Lucija_2025.pdf VS_Novak_Lucija_2025.pdf 1 06670B44CC39D1BE23DE285F80A1A7E4 e8646007ac84192bd08dd82e3016028ad26e0ce09750e1c5ce722e31dfbcca4d f9d4a2c3-8317-11f0-8e8c-00155d000105 https://dk.um.si/Dokument.php?lang=slv&id=196545 Fakulteta za kemijo in kemijsko tehnologijo 0 0 0