Naslov
Na granici između inter‐ i intramolekulskoga: dvoelektronske multicentrične kovalentne veze
(On the border between inter‐ and intramolecular: two‐electron multicentric covalent bonding)

Autori
Molčanov, Krešimir ; Kojić-Prodić, Biserka ; Stilinović, Vladimir ; Mou, Zhongyu ; Kertesz, Miklos ; Landeros-Rivera, Bruno ; Hernandez-Trujillo, Jesus

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
26. Hrvatski skup kemičara i kemijskih inženjera, Knjiga sažetaka / Galić, Nives ; Rogošić, Marko - Zagreb : Hrvatsko društvo kemijskih inženjera i tehnologa (HDKI), 2019, 39-39

ISBN
978-953-6894-67-3

Skup
26. hrvatski skup kemičara i kemijskih inženjera (26HSKIKI) ; 4. simpozij Vladimir Prelog

Mjesto i datum
Šibenik, Hrvatska, 09.04.2019. - 12.04.2019

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Domaća recenzija

Ključne riječi
kemijska veza ; međumolekulske interakcije ; vodikova veza ; halogenska veza ; gustoća naboja
(chemical bonding ; intermolecular interactions ; hydrogen bonding ; halogen bonding ; charge density)

Sažetak
Three model systems with strong interactions bordering intra- and intermolecular were studied by experimental X-ray charge density analysis: hydrogen bonding, halogen interactions and π-stacking. The studies revealed that in all three cases the interaction involves multicentric two-electron covalent bonding. Nature of the strong hydrogen bond was studied on the well-known protonated dimer of water molecules, the Zundel cation. Our study shows that both O-H bonds in the central O-H-O fragment have a maximum electron density of about 1 e Å-3, and the negative value of the Laplacian, consistent with 2-electron/3-centre bonding ; O-H bonds have an order of 0.5. Recent studies showed that nature and strength of hydrogen and halogen bonds are similar. We studied two systems with very short and strong halogen bond N-Br···N. Pure N-bromosuccinimide was used as a standard, to evaluate charge density of an single N-Br bond. In its co-crystal with 3, 5-dimethylpyridine, the Br atom is displaced toward the acceptor by almost 0.4 Å and the maximum electron density in the contact Br···N is 0.4 e Å-3, indicating a significant covalent contribution. The strongest halogen bond, a symmetrical N-Br-N fragment, was studied in crystals of bromonium salt, bis(3-methylpyridine)bromonium perchlorate and it involves a two-electron/three-centre covalent bond N-Br-N. Our studies of π-interactions of semiquinone radicals involved three types of stacks: closely interacting radical dimers ('pancake bonding') [3], trimers of partially charged radicals and stacks of equidistant radicals. X-ray charge density supported by quantum chemical modelling revealed considerable covalent contribution (i.e. spin coupling and mixing of SOMO orbitals) in all of them. Therefore, π-interactions between the radicals can be regarded two-electron multicentric covalent bonding.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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