Naslov
Tautomerism in two novel internally H-bonded N-3-methoxysalycilaldimine Schiff bases

Autori
Pavlović, Gordana ; Kaitner, Branko

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

Izvornik
Seventh Slovenian-Croatian Crystallographic Meeting, Book of Abstracts and Programme / Leban, Ivan ; Petrovčič, Nina - Ljubljana : Univerza v Ljubljani, 1998

Skup
Seventh Slovenian-Croatian Crystallographic Meeting

Mjesto i datum
Radenci, Slovenija, 18.06.1998. - 20.06.1998

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Tautomerism; Schiff base; intramolecular hydrogen bond; salycilaldimine

Sažetak
The Schiff base compounds can be classified by their photochromic and thermochromic behaviour. Photochromism as well as thermochromism is produced by the intramolecular proton transfer associated with a change in the pi-electron configuration induced by a proton transfer. N-Salicylaldimines exhibit such interesting conformation-dependent properties. Due to an earlier proposed classification, planar geometry is associated with thermochromism, non-planar with photochromism. The hydrogen atom position in the six membered pseudoaromatic chelate ring formed by the intramolecular hydrogen bond and the orientation of N-substituted aromatic ring with respect to the plane of salicylaldimine moiety are responsible for chromo behaviour. Two novel N-R-3-metoxysalicylaldimines [R stands for 4-methyl-2-aminopyridyl in (I) and 2-aminomethylpyridyl in (II)] have been prepared by standard synthetic procedure and characterized by DSC, FT IR spectroscopy and the X-ray structure analysis in order to establish the molecular conformation in the solid state due to the presence of substituted pyridine ring as N-substituent. Crystal data: (I): C14H14N2O2, Mr = 242.28, Monoclinic, P 21/c, a = 9.9944(8), b = 4.8923(3), c = 24.719(2) A, b = 94.21(1)o, V = 1205.40(16) A3, Z = 4, Dcalc = 1.335 Mgm-3, mi = 0.8 cm-1, lambda = 0.7107 A, R = 0.048 for 1197 reflections with Inet gt 2sigma(Inet). (II): C14H14N2O2, Mr = 242.28, Monoclinic, P 21/c, a = 9.090(2), b = 5.661(1), c = 24.268(5) A, b = 92.63(2)o, V = 1247.5(4) A3, Z = 4, Dcalc = 1.290 Mgm-3, mi = 0.8 cm-1, lambda = 0.7107 A, R = 0.057 for 627 reflections with Inet gt 2sigma(Inet). The molecule (I) is almost planar excluding C26 methyl group while in the molecule (II) the planarity is probably inhibited by the presence of C2 methylene group [dihedral angles between phenyl and pyridine ring are 5.3(1)o in (I) and 74.1(3)o in (II)]. Except crystal packing, the driving force for planarity of compound (I) is the presence of the pyridine moiety nitrogen atom which does not interact repulsively with hydrogen at the C=N imino group carbon atom as in the salicylideneanilines. The basic stereochemical feature in both molecules is the enolimine tautomeric form confirmed by the presence of the hydrogen atom bonded to oxygen [O-H...N type of the intramolecular hydrogen bond with O...N separation 2.580(4) (I) and 2.591(8) A (II), respectively]. Such tautomeric form, as a particular characteristic of salicylaldimines in the crystalline state, is additionally confirmed by the Csp2-O bond length 1.350(5) A in (I) and 1.352(11) A in (II) that should be considered as single bonds.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA