Naslov
The structure of gel grown crystals of 2-bis[(2- hydroxyphenylmethylene)amino]methylphenol

Autori
Friščić, Tomislav ; Meštrović, Ernest ; Kaitner, Branko

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

Izvornik
Sixth Croatian-Slovenian Crystallographic Meeting / Popović, Stanko - Zagreb : Hrvatska akademija znanosti i umjetnosti (HAZU) ; Hrvatska kristalografska zajednica HAZU, 1997, 9-9

Skup
Sixth Croatian-Slovenian Crystallographic Meeting

Mjesto i datum
Umag, Hrvatska, 19.06.1997. - 21.06.1997

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
gel crystallization ; intramolecular hydrogen bond ; polymorphism

Sažetak
Gel crystallization is a suitable method for growing the single crystals but, because of time consuming and uncertain results, it is rarely used. One of the advantages of the method is that the flow of material to the growing crystal is controlled by the diffusion rate only, since the convection of the solution around the crystal is almost totally excluded. Besides, the grown crystals are very likely the single ones, since the gel network prevents collisions with other crystal nuclei existing in the solution. One of the significant differences between Schiff bases derived from salicylaldehyde and those prepared from 2-hydroxy-1-naphthaldehyde is the position of the hydrogen atom in chelate ring intramolecular hydrogen bond. This hydrogen atom in naphthaldimines is usually positioned to the nitrogen atom (keto-amine tautomer), while in the most salicylaldimines it is bonded to the oxygen (enol-imine tautomer). The difference in the melting points between the purified powder material and the gel grown crystals prompted us to determine the crystal structure. The gel grown crystals were indeed a third polymorph of the compound. The molecules contain two intramolecular hydrogen bonds ; one of the hydrogen bridges exists in two tautomeric forms (1:1 ratio) with hydrogen atom linked either to the oxygen or to the nitrogen atom. The second intramolecular hydrogen bond is entirely of the O-H N type [(I) keto- amine/enol-imine tautomer ; (II) enol-imine/enol- imine tautomer]. The appeareance of an N-H O type of hydrogen bond, not common in salicylaldimines, is probably caused by the intermolecular O-H O hydrogen bond between the oxygen atom already included in intramolecular hydrogen bonding and the phenol ring oxygen of the neighboring molecule.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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