Transition metal complexes of a novel quinoxaline‐based tridentate ONO donor ligand: synthesis, spectral characterization, thermal, in vitro pharmacological and molecular modeling studies

Abstract

Co(II), Ni(II), Cu(II) and Zn(II) complexes of a novel tridentate heterocyclic ligand, 3‐{[(2‐benzoyl‐4‐chlorophenyl)imino]methyl}quinoxalin‐2(1H)‐one, have been synthesized. The ligand and the metal complexes were characterized using elemental analysis, molar conductance and magnetic susceptibility measurements, and UV–visible, Fourier transform infrared, 1H NMR, 13C NMR, electron spin resonance and DART mass spectral data. The ligand behaves as a tridentate one, coordinating through two oxygen atoms from two keto groups and through the azomethine nitrogen atom. The thermal properties of the newly synthesized compounds were determined using thermogravimetric analysis. The ligand and its metal complexes were subjected to powder X‐ray diffraction analysis by which average crystallite size and unit cell parameters were calculated. The electrochemical behaviour of the compounds was studied using cyclic voltammetry. The ligand and the metal complexes were screened for their in vitro antimicrobial activities against the bacterial strains E. coli, K. pneumoniae, S. pneumoniae and S. aureus and the fungal species A. niger, A. flavus, P. chrysogenum and R. stolonifer. DNA binding, DNA cleavage and antioxidant activities of the compounds were also evaluated. The compounds bind with DNA through groove binding. The Cu(II) and Zn(II) complexes exhibit higher superoxide anion and hydrogen peroxide scavenging activities, respectively. The Cu(II) complex exhibits better anticancer activity against the MCF7 cell line. The compounds were subjected to molecular docking study against B‐DNA dodecamer d(CGCGAATTCGCG)2 and vascular endothelial growth factor receptor kinase to justify the experimental DNA binding and MTT assay. Density functional theory studies were used to optimize the geometry of the compounds and to calculate the nonlinear optical properties. Copyright © 2016 John Wiley & Sons, Ltd.

Synthesis and Spectroscopic Study of Some Transition Metal Complexes with New Pyrazolinone Ligand Derived from 2-Hydrazino Quinoxaline-3-one

“…The nuclear resonance of aromatic protons Ar-H and pyrazine H were recorded about (6.90-7.11) and (7.90-8.22) ppm, respectively. Furthermore, 13 C NMR showed distinct absorptions of -C=N-at 190 and 220 ppm indicating the ring closure of pyrazolinone ring [12,13]. However, the other peaks belonged to aromatic -C=C-of pyrazine and phenyl rings were measured around (88.2-137) ppm.…”

“…Electronic spectra and magnetic properties: The electronic absorptions of the ligand and its metal complexes solutions in DMF and ethanol are shown in Table-3. The solution of ligand in ethanol displays two spin-allowed transitions in the regions 260 and 360 nm which is characteristic of -C=N-, -C=C-and -C=O functional groups incorporated in pyrazole and pyrazine rings, respectively [12,15]. The pale coloured solution of Mn(II) complex showed weak peak at 455 nm and other of high intensity at 340 nm, these may be assigned to d-d and MLCT, respectively [13,20].…”

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

“…mp > 300°C (decomp). 1 In order to the synthesis of new heterocyclic Schiff-base ligands, the commercially available 5-nitro-1H-benzimidazole was alkylated with 1-bromopropane and 1bromobutane in KOH and DMF to give 1-alkyl-5-nitro-1H-benzimidazole (1a,b). [27] 3-Alkyl-8-(4-chlorophenyl)-3H-imidazo [4',5':3,4]benzo[1,2-c]isoxazoles (3a,b) were prepared from the reaction of 1-alkyl-5-nitro-1H-benzimidazole 1a,b with (4-chlorophenyl)acetonitrile (2) in basic MeOH solution.…”

“…One of the most interesting areas of coordination chemistry is the interaction of transition metal ions with biological molecules. There are many metal complexes that can use as drugs and chemotherapeutic agents …”

“…There are many metal complexes that can use as drugs and chemotherapeutic agents. [1] Iron is one of the essential mineral that can function as regulators, activators, transmitters, and controllers of various enzymatic reactions. [2,3] In hence, the iron complexes have received considerable attention owing to their effective biological importance such as antibacterial [4,5] antifungal [6] antivirus [7] antiproliferative [8] and anticancer activity.…”