Naslov
FT-IR spectroscopic studies of the phytohormone auxin (indol-3-ylacetic acid, IAA) and its n-alkylated and monohalogenated derivatives

Autori
Lutz, Bert T.G. ; Van der Windt, Erik ; Kanters, Jan ; Klaembt, Dieter ; Kojić-Prodić, Biserka ; Ramek, Michael

Izvornik
Journal of molecular structure (0022-2860) 382 (1996), 3; 177-185

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
FT-IR study ; auxin ; indole-3-acetic acid ; hydrogen bonding

Sažetak
In the framework of structure/activity correlation studies the plant growth hormone auxin and its natural analogue 4-CI-IAA, as well as their synthetic congeners, were studied by FT-IR spectroscopy. The analysis was focused on the N-H and C=O stretching vibrations which can be the most sensitive probes of intra- and intermolecular interactions, particularly to hydrogen bonds. However, it emerged that nu(C = O) vibrations of both monomer and dimer are not affected by substitution. The aliphatic -CH2 group acts as an insulator between the conjugated pi-system of indole and the carboxylic group, thus prohibiting a direct effect on the vibration C=O. On the contrary, the stretching vibrations N-H are influenced by halogenation and hydrogen bonding. The experimental data are in good agreement with the results of quantum chemical ab initio calculations of N-H vibrations for IAA and several chlorine substituted IAAs. However, a simple correlation between substitution and spectral properties of indole NH cannot be found. The measurements were performed in the solid state O(Br pellets) and in polar (diethylether) and nonpolar (CDCl3) solutions. From the measurements in diethylether, it follows that in dilute solution IAA and derivatives are predominantly present as monomer, whereas in CDCl3 the equilibrium is in favour of the dimer form. In aqueous solution at the concentrations used in growth experiments solvated monomer will be the active component. Bioactivity of auxin and analogues with their N-H stretching frequency shifts cannot be correlated in a simple way.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA