NCU analysis in quantum-chemical microsolvation modelling

Za opis strukture i reaktivnosti u otapalu posebno su bitne molekule otapala koje neposredno stupaju u interakcije sa solutom, a koje se poglavito nalaze u blizini funkcionalnih skupina. Ovaj rad bavi se upotrebom NCU (Natural Cluster Unit) analize u svrhu modeliranja mikrosolvatacije. U radu se koristi nova, dvostupanjska klaster-kontinuum metoda. Prvi korak se temelji na upotrebi solvatacijskih bazena funkcionalnih skupina za pronalaženje svih molekula otapala koje su potencijalno bitne za mikrosolvataciju. U drugom koraku, NCU analizom molekule otapala rangiraju se po energiji interakcije sa solutom. Najbolje rangirane modeliraju se eksplicitno, a ostale se zamjenjuju kontinuumom. U radu su proučavane molekule anilina, fenilhidroksilanilina i octene kiseline, te njihove konjugirane kiseline odnosno baze. Početni klasteri dobiveni su upotrebom Monte Carlo basin hopping metode, a nakon primjene SBFS metode i NCU analize konačne konfiguracije reoptimizirane su na ωB97X-D/6-311+G(2df,2p)/SMD razini teorije.Solvent molecules which are involved in significant interactions with solute, making them important for proper description of solute structure and reactivity, are usually located in proximity of functional groups. The focus of this thesis is the appropriate selection of those solvent molecules and microsolvation modelling using a new approach based on NCU (Natural Cluster Unit) analysis. A new two-step cluster-continuum method is presented. In the first step, functional group solvation basins are used for identifying solvent molecules potentially important for microsolvation. In the second step, solvent molecules are ranked in terms of the solute energy interaction using NCU analysis. The best ranked ones are then modelled explicitly and others replaced with continuum solvent. Aniline, phenylhydroxylamine and acetic acid, along with their conjugated acids and bases are studied. Initial clusters are generated using Monte Carlo basin hopping method, and the final configurations reoptimized on ωB97X-D/6-311+G(2df,2p)/SMD level of theory