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Obravnava vodikovih vezi med kovinskimi hidroksidi in organskimi molekulami z molekulskim modeliranjem
Gašparič, Lea (Author), Jamnik, Andrej (Mentor) More about this mentor... This link opens in a new window, Kokalj, Anton (Co-mentor)

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Abstract
Z izračuni na osnovi teorije gostotnega funkcionala (DFT, angl. denisty functional theory) smo analizirali lastnosti vodikovih vezi med kovinskimi hidroksidi in molekulami s tipičnimi organskimi funkcionalnimi skupinami. Kot modelna sistema kovinskih hidroksidov smo uporabili bakrov in aluminijev hidroksid, za organske molekule pa smo izbrali metilamin, metanimin, imidazol, metanol, etanal, metantiol in dimetilfosfinsko kislino. Najprej smo izvedli izračune za komplekse med izbranimi molekulami in molekulo vode. S tem smo pridobili primerjalne vrednosti za jakosti vodikovih vezi in določili akceptorske in donorske sposobnosti molekul. Nato smo izvedli izračune s preprostim modelom diskretne gruče bakrovega in aluminijevega hidroksida. Ugotovili smo, da je bakrov hidroksid boljši donor in akceptor kot molekula vode, aluminijev hidroksid pa ima podobne sposobnosti tvorbe vodikove vezi kot molekula vode. Izmed organskih molekul sta se kot močna donorja in akceptorja izkazali molekuli dimetilfosfinske kisline in imidazola. Zaradi nastanka šibkih vodikovih vezi, kjer CH skupina nastopa kot donor, smo analizirali tudi odvisnost energije teh vezi od razdalje med donorjem in akceptorjem ter kota med atomi. Da bi preverili ustreznost preprostega modela diskretnih gruč, smo izvedli tudi izračune na površinah bakrovega hidroksida in boehmita (AlOOH), ki smo ju opisali z modelom periodične plošče. Na površino smo adsorbirali samo molekuli imidazola in dimetilfosfinske kisline, ki sta bila na podlagi izračunov z diskretnimi gručami najboljša kandidata za močno adsorpcijo na površino. Primerjava rezultatov obeh modelov je pokazala, da lahko s preprostimi izračuni z diskretnimi gručami ocenimo energijo adsorpcije ob predpostavki, da lahko predvidimo geometrijo vezave na površino in število vodikovih vezi, ki se pri tej vezavi tvorijo.

Language:Slovenian
Keywords:vodikova vez, kovinski hidroksidi, adsorpcija, DFT
Work type:Master's thesis/paper (mb22)
Tipology:2.09 - Master's Thesis
Organization:FKKT - Faculty of Chemistry and Chemical Technology
Year:2020
COBISS.SI-ID:35569667 Link is opened in a new window
Views:100
Downloads:48
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Secondary language

Language:English
Title:Study of hydrogen bonds between metal hydroxides and organic molecules with molecular modeling
Abstract:
Hydrogen bonding between metal hydroxides and common organic functional groups was investigated using density functional theory (DFT) calculations. Copper and aluminum hydroxides were used to represent metal hydroxides. Methylamine, methanimine, imidazole, methanole, ethanal, methanethiol and dimehylphosphinic acid were selected as common organic molecules. We performed calculations on the complexes between selected molecules and a water molecule to obtain benchmark hydrogen bond strengths and determine their donor and acceptor abilities. Then we carried out calculations with a simple model of a discrete cluster for copper and aluminum hydroxides. Our results showed that copper hydroxide has better donor and acceptor abilities than a water molecule but aluminum hydroxide form hydrogen bonds with similar properties as a water molecule. Among all organic molecules usen in this study, imidazole and dimethylphosphinic acid formed the strongest hydrogen bonds both as donor and acceptor. Many complexes showed the formation of bonds where a CH group acted as a donor, therefore we also analyzed the dependence of the energy on bond lengths and their angles. To assess whether simple discrete cluster model gives reasonable results for metal hydroxide systems, we also performed calculations on the metal hydroxide surfaces, which were represented by a periodic slab model. Only imidazole and dimethylphosphinic acid molecules were adsorbed on the surface because they formed the strongest hydrogen bonds with discrete clusters. A comparison of both models showed that the energies of adsorption could be estimated with discrete cluster calculations, but only under provision that one can predict the geometry of bonding and the number of formed hydrogen bonds.

Keywords:hydrogen bond, metalic hydroxides, adsorption, DFT

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