Synthesis, spectral, DFT calculations and antibacterial
studies of Fe(III) complexes of new fluorescent Schiff bases
derived from imidazo[4',5':3,4]benzo[1,2‐c]isoxazole
Shirin Ramezani | Mehdi Pordel | Abolghasem Davoodnia
Department of Chemistry, Mashhad
Branch, Islamic Azad University,
Mehdi Pordel, Department of Chemistry,
Mashhad Branch, Islamic Azad
University, Mashhad, Iran.
New fluorescent heterocyclic ligands were synthesized by the reaction of 8‐(4‐
chlorophenyl)‐3‐alkyl‐3H‐imidazo[4',5':3,4]benzo [1,2‐c]isoxazol‐5‐amine with
p‐hydroxybenzaldehyde and p‐chlorobenzaldehyde in good yields. The coordi-
nation ability of the ligands with Fe
ion was examined in an aqueous metanolic
solution. Schiff base ligands and their metal complexes were characterized by
elemental analyses, IR, UV–vis, mass, and NMR spectra. The optical properties
of the compounds were investigated and the results showed that the fluorescence
of all compounds is intense and their obtained emission quantum yields are
around 0.15 – 0.53. Optimized geometries and assignment of the IR bands and
NMR chemical shifts of the new complexes were also computed by using density
functional theory (DFT) methods. The DFT‐calculated vibrational wavenumbers
and NMR chemical shifts are in good agreement with the experimental values,
confirming suitability of the optimized geometries for Fe(III) complexes. Also,
the 3D‐distribution map for HOMO and LUMO of the compounds were
obtained. The new compounds showed potent antibacterial activity and their
antibacterial activity (MIC) against Gram‐positive and Gram‐negative bacterial
species were also determined. Results of antibacterial test revealed that coordina-
tion of ligands to Fe(III) leads to improvement in the antibacterial activity.
antibacterial activity, bidentate ligand, density functional theory, Fe(III) complex, Schiff base
1 | INTRODUCTION
One of the most interesting areas of coordination chemis-
try is the interaction of transition metal ions with biolog-
ical molecules. There are many metal complexes that can
use as drugs and chemotherapeutic agents.
Iron is one of the essential mineral that can function as
regulators, activators, transmitters, and controllers of vari-
ous enzymatic reactions.
In hence, the iron complexes
have received considerable attention owing to their
effective biological importance such as antibacterial
The stabilities and coordination chemistry of
Fe(III) with bidentate ligands
have also resulted from
their efficacy as oral iron chelating agents
agents for the treatment of iron overload conditions.
Benzo[1,2‐c]isoxazoles are an important class of hetero-
cyclic pharmaceuticals and bioactive compounds which
are prescribed as antipsychotic risperidone
and play a key role in many organic reac-
Isoxazole‐metal complexes are often postulated
as intermediates in reactions of considerable synthetic util-
ity, for example the reductive ring opening of isoxazoles.
Several isoxazole‐metal complexes have been reported
Received: 29 June 2017 Revised: 19 October 2017 Accepted: 19 October 2017
Appl Organometal Chem. 2018;32:e4178.
Copyright © 2017 John Wiley & Sons, Ltd.wileyonlinelibrary.com/journal/aoc 1of11