Synthesis, Characterization and Biological Evaluation of Mononuclear Co(II), Ni(II), Cu(II) and Pd(II) Complexes with New N2O2 Schiff Base Ligands

Abstract

Schiff bases have a variety of applications in biological, clinical, and pharmacological areas. The synthesis and application of Schiff bases and their coordination compounds have been highly considered in inorganic, organic and biological fields, since their structural properties similar to some of the biological systems.1-6) Additionally, tetradentate Schiff bases composed of N 2 O 2 donor atoms set have been recognized as a kind of important chelating ligands for designing medicinally and catalytically useful metal complexes. [7][8][9] The flexible coordination behavior of these types of chelating ligands could also be useful to generate interesting dimeric and polymeric structures as synthones for supramolecular chemistry. 10,11) Usually, the N, O donor heterodentate Schiff bases can be derived by condensing the aldehydes/ketones with various amines or amino acids. 12,13) N 2 O 2 Schiff base ligands derived from salicylald ehyde and diamine have been known. 14,15) Dialdehydes and diketones with amines and amino acids have also been utilized to obtain a variety of N 2 O 2 Schiff base ligands. 16)Amino acids plays an important role in many physiological activities of the human body and also helpful in understanding biological functions of macromolecules such as proteins. 17) In particular, tryptophan (Trp)/histidine (His) analogues as promising candidates for novel antimicrobial therapeutics. In the recent years, a series of synthetic peptide analogues based on Trp-His and His-Arg (antimicrobial peptides) structural frameworks have been prepared and found to be active against several Gram-positive and Gram-negative bacterial strains as well as against fungal strains.18) Furthermore, it is well known that the human body contains essential metaloelements which play important roles and interact with many biological molecules to fully understand the physiological functions by studying their chemistry coordination and behavior. 17,18) In the present studies we have introduced an azomethine (Schiff base) linkage to tryptophan/histidine, which may permit a variety in their coordination behaviour and complexation role.In previous studies, we have described the synthesis, catalytic and biological applications of Schiff bases and their metal complexes derived from o-phthalaldehyde (OPA) with various amines. [19][20][21][22][23][24][25][26][27] In this respect, we have also developed some useful macrocyclic Schiff bases and their metal complexes. Results from these studies have also shown that complexation of metals with Schiff base ligands serves to improve their antimicrobial activity. There are few other research groups also reported the importance of Schiff base chemistry of the combination of o-phthalaldehyde with amines.28,29) However, a careful literature survey reveals that Schiff bases from the combination of amino acids and o-phthalaldehyde and their coordination behavior towards the transition elements have yet not been studied. The combination of dialdehyde i.e. o-phthalaldehyde and aminoacids is expected to ...

Synthesis, Characterization and Catalytic Applications of 2,2-Dimethylpropane-1,3-Diaminopalladium(II) Complex in Mizoroki-Heck Reaction

“…The absence of sharp singlet resonance of the phenolic proton (δ 14.11 ppm) further approved that (-OH) group had participated in chelation through deprotonation. Meanwhile, 13 C NMR showed the displacement of (C=N) carbon to the lower field in PdLSB supported the coordination of azomethine nitrogen and phenolic oxygen to Pd metal [13]. Table-2 shows the summary data for 1 H and 13 C NMR for LSB and PdLSB.…”

“…Meanwhile, 13 C NMR showed the displacement of (C=N) carbon to the lower field in PdLSB supported the coordination of azomethine nitrogen and phenolic oxygen to Pd metal [13]. Table-2 shows the summary data for 1 H and 13 C NMR for LSB and PdLSB. The elemental analysis of LSB and PdLSB was analyzed to determine the agreement between the theoretical and experimental values with molecular formula suggested in Table-3. The square planar of PdLSB was confirmed by single X-ray crystallography analysis and found to be in agreement with the literature [14].…”

“…CHN elemental analyses were recorded using a Thermo Finnigan CE 125 CHN analyzer. 1 H and 13 C NMR were recorded on a Bruker Avance 400 MHz spectrometer with CDCl3 as a solvent. A single X-ray Crystallography was performed by using a Bruker APEX DUO CCD area detector diffractometer.…”

Synthesis, Spectral and Antibacterial Studies of Copper(II) Tetraaza Macrocyclic Complexes

“…Cu(II) is the most studied metal ion among all the transition metal ions [16,17]. Cu(II) complexes are known to play a significant role either in naturally occurring biological systems or as pharmacological agents [18,19]. In connection with previous investigations [1,2,20], on the coordinating properties of tetraaza macrocycles, and in order to isolate new transition metal complexes with potential antimicrobial properties, we have studied the synthesis, spectroscopic and biochemical aspects of tetraaza macrocyclic complexes of copper(II) derived from o -phthalaldehyde with various diamines.…”

Antibacterial Activity of Pd(II) Complexes with Salicylaldehyde-Amino Acids Schiff Bases Ligands

“…Therefore, there is an urgent demand for the development of new antimicrobial agents with improved properties such as enhanced activity, reduced toxicity and shortened duration of therapy. 1) Schiff bases have a variety of applications in chemical, biological and pharmacological fields. 2,3) The bi-, tri-or tetra-dentate Schiff bases with N, O as donor atoms, can be obtained by condensation of aldehydes or ketones with various amines, diamines or aminoacids.…”