Macrocyclic Schiff Base Complexes Research Articles

Novel tetraaza macrocyclic Schiff base complexes of bivalent zinc: microwave-assisted green synthesis, spectroscopic characterization, density functional theory calculations, molecular docking studies, in vitro antimicrobial and anticancer activities.

In the present manuscript, novel macrocyclic Schiff base complexes [Zn(N4MacL1)Cl2-Zn(N4MacL3)Cl2] were synthesized by the reaction of ZnCl2 and macrocyclic ligands (N4MacL1-N4MacL3) derived from diketone and diamines under microwave irradiation method and conventional method. The structures of the obtained complexes were identified by various spectrometric methods such as Fourier transformation infra-red (FT-IR), nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HR-MS), powder X-ray diffraction, molar conductivity, and UV-vis. The structures of the synthesized compounds were optimized by using the def2-TZV/J and def2-SVP/J Coulomb fitting basis sets at B3LYP level in density functional theory (DFT) calculations. The macrocyclic Schiff base complexes exhibited higher activities against Gram-positive bacteria (Staphylococcus aureus and Bacillus cereus), Gram-negative bacteria (Escherichia coli and Xanthomonas campestris), and fungal strains (Fusarium oxysporum and Candida albicans) in comparison to macrocyclic Schiff base ligands. Furthermore, the newly synthesized macrocyclic compounds were assessed for their anticancer activity against three cell lines: A549 (human alveolar adenocarcinoma epithelial cell line), HT-29 (human colorectal adenocarcinoma cell line), and MCF-7 (human breast adenocarcinoma cell line) using the MTT assay. The obtained results showed that the macrocyclic complex [Zn(N4MacL3)Cl2] displayed the highest cytotoxic activity (2.23 ± 0.25µM, 6.53 ± 0.28µM, and 7.40 ± 0.45µM for A549, HT-29, and MCF-7 cancer cell lines, respectively). Additionally, molecular docking investigations were conducted to elucidate potential molecular interactions between the synthesized macrocyclic compounds and target proteins. The results revealed a consistent agreement between the docking calculations and the experimental data.

Pharmacologically important tetraaza macrocyclic Schiff base complexes of Zn(II), Cu(II) and Co(II): Synthesis, characterization, DFT studies, molecular docking and in vitro anti-bacterial and anti-cancer studies

A novel tetraaza macrocyclic Schiff base ligand and its metal complexes [Zn(II), Cu(II), and Co(II)] were successfully synthesized and characterized using various analytical techniques including FT-IR, NMR, ESI-MS, UV-Vis, PXRD, ESR, and TGA. The chemical reactivity and molecular geometry of the compounds were further elucidated through DFT calculations. The synthesized compounds were evaluated for their anti-bacterial activity against both Gram +ve and Gram -ve bacteria. Remarkably, the metal complexes exhibited enhanced anti-bacterial activity compared to the ligand. All compounds displayed moderate antibacterial activity against various strains, with complexes 4a and 4b demonstrating the highest inhibition against Gram +ve bacteria at 0.1 µM concentration. Furthermore, the cytotoxicity of these compounds against a human liver cancer cell line (HepG2) was assessed, revealing substantial anti-proliferative activity. Notably, the Zn(II) complex demonstrated an IC50 value comparable to the standard drug Doxorubicin. Importantly, the ligand and Zn(II) and Co(II) complexes exhibited minimal (< 5%) hemolysis at their IC50 values, suggesting their non-toxic nature. Molecular docking studies were conducted to investigate the binding interactions of the synthesized compounds with the active site of the topoisomerase IIβ enzyme (PDB ID: 4G0V), a crucial target for anti-bacterial and anti-cancer medications. Complex 4a displayed the strongest binding affinity (-8.2 kcal/mol) and the most favourable docked conformation, with multiple hydrogen bonds to the protein's active site. These results suggest its potential for further development as a therapeutic agent.

Synthesis, spectroscopic characterization, density functional theory, molecular docking studies, antioxidant and antimicrobial potential of novel Schiff base macrocyclic complexes of bivalent manganese

The threat of antibiotic resistance to public health is becoming a major cause of mortality on a worldwide scale. It has stimulated the interest of researchers in the development of novel antibiotics. Therefore, a new series of Schiff base macrocyclic ligands (N8MacL1‐N8MacL3) and their bivalent manganese complexes were synthesized and analyzed for biological activities. Characterization of the synthesized macrocyclic compounds was done by various spectroscopic techniques like elemental analysis, infrared (IR), proton nuclear magnetic resonance (NMR), 13C NMR, ultraviolet–visible, mass, electron paramagnetic resonance (EPR), and powder X‐ray diffraction (PXRD). Based on spectral studies, an octahedral environment has been proposed around the manganese metal center in the synthesized macrocyclic complexes. Density functional theory (DFT) calculations were used to evaluate the stability and the electronic properties of the synthesized macrocyclic ligands and their Mn (II) complexes. The structures of the synthesized compounds were optimized by using the def2‐SVP basis set at B3LYP level. The synthesized compounds were evaluated against gram‐positive bacterial strains (Staphylococcus aureus and Bacillus cereus), gram‐negative bacterial strains (Escherichia coli and Xanthomonas campestris), and fungal strains (Candida albicans and Fusarium oxysporum) for their antimicrobial activity by agar well diffusion method. Among all of the newly synthesized compounds, the macrocyclic complex [Mn(N8MacL3)Cl2] exhibited high antimicrobial activity against all bacterial and fungal strains except S. aureus. The virtual screening of synthesized Schiff base ligand [L], macrocyclic ligands (N8MacL1‐N8MacL3), and their Mn (II) complex [Mn(N8MacL1)Cl2‐Mn(N8MacL3)Cl2] are performed against the receptors, which were used for in vitro antimicrobial testing, to identify the most plausible drug–ligand interactions. The scavenging activity of DPPH radicals was utilized to study the antioxidant activity of the synthesized compounds. The macrocyclic metal complex [Mn(N8MacL3)Cl2] exhibited excellent antioxidant activity.

Nanomagnetic tetraaza (N4 donor) macrocyclic Schiff base complex of copper(ii): synthesis, characterizations, and its catalytic application in Click reactions.

In this research, a novel nanomagnetic tetra-azamacrocyclic Schiff base complex of copper(ii) was produced via a post-synthetic surface modification of an Fe3O4 surface by a silane-coupling agent that contains acetylacetone functionalities at the end of its chain. Moreover, the target Cu complex that involves a tetradentate Schiff base ligand was obtained from a template reaction with o-phenylenediamine and Cu(NO3)2·3H2O. Furthermore, the prepared complex was nominated as [Fe3O4@TAM-Schiff-base-Cu(II)]. The Fourier-transform infrared (FT-IR) analysis indicates the presence of a Schiff-base-Cu complex in the catalyst. X-ray spectroscopy (EDS) and TGA analysis reveal that approximately 6-7% of the target catalyst comprises hydrocarbon moieties. The scanning electron microscope (SEM) and transmission electron microscopy (TEM) images demonstrate the presence of uniformly shaped particles, nearly spherical in nature, with sizes ranging from 9 to 18 nm. [Fe3O4@TAM-Schiff-base-Cu(II)] was applied as a catalyst for the click synthesis of a diverse range of 5-substituted-1H-tetrazoles in PEG-400 as a green medium. Regarding the electrical properties of the Cu(ii) complex, the presence of a tetra-aza (N4 donor) macrocyclic Schiff base as an N-rich ligand was reasonable - leading to its excellent capacity to catalyze these organic transformations. Finally, the high magnetization value (44.92 emu g-1) of [Fe3O4@TAM-Schiff-base-Cu(II)] enables its recycling at least four times without compromising the catalytic efficiency.

New Homo and Heterobinuclear Macrocyclic Complexes Bearing Isatine Structural Characterization, Thermal Study and DFT Calculations

A new metal-free macrocyclic Schiff base ligand bearing two metal cavities incorporated with two sets of N3O2 donor atoms derived from 2, 6-diaminopyridine and isatine was synthesized. The new ligand was used to prepare homo and hetero binuclear macrocyclic Schiff base complexes with Ni (II), Cu (II), ZrO (II) and Ba (II) metal ions. The ligand and metal complexes were characterized using Fourier transform infrared (FT-IR), UV–vis, mass spectroscopy, elemental analysis (CHN), thermo gravimetric analysis (TGA), magnetic susceptibility, and molar conductivity measurements. The DFT calculations using the B3LYP functional method have been applied to obtain the geometry and electronic properties of the ligand and its metal complexes to support the experimental data. To describe the reactivity of the title molecules, the HOMO and LUMO levels and Mulliken atomic charges were determined.

Metal Complexes of Bis (2,6-diamine pyridine 2,5-hexanedione) Macrocyclic Schiff-Base Ligand: Preparation, Characterization and thermal study

New series of Schiff base macrocyclic complexes have been prepared through a new chemical approach. Firstly, ligand Bis (2,6-diamine pyridine 2,5-hexanedione (DP-HD) prepared via reacting of 2,6-diamine pyridine (DP) with 2,5-hexanedione(HD) in molar ration (1DP:1HD). The complexes of this ligand include Mn (II), Fe (II), Co (II), Ni (II) and Cu (II) as central metal ions also prepared with a molar ratio of (1 ligand:1 metal ion). Metals chloride was used as raw materials for this preparation. A variety of spectral and physical techniques were applied to characterize the macrocyclic complexes such as 1H-NMR, FT-IR, UV-Vis, CHN analysis, conductivity, Atomic absorption and magnetic susceptibility. Depending on spectral and magnetic measurements, the suggested geometrical shapes of these complexes were reported. FT-IR spectroscopy recorded the coordination sites based on the ligand's main group bands that could shift to a lower frequency. Finally, thermal stability has been investigated for ligands and their complexes. While the thermal gravimetric analyses (TGA) and differential thermal analyses (DTA) approved the stability of these compounds if compared to their ligands only.

Synthesis, biological evaluation of substituted indol-2,3-dione and 2,2-dimethylpropane-1,3-diamine Cu(II), NI(II) and Fe(II) metal complexes

A series Schiff base macrocyclic complexes of the type [HLMX2] where M = Cu(II), Ni(II), Co(II) and X = Cl, OAc have been synthesized by condensation of 5-methylindoline- 2,3-dione and 2,2-dimethylpropane-1,3-diamine in the presence of divalent metal salt in methanolic medium. The complexes have been characterized with the help of elemental analysis, conductance measurements, magnetic measurements and their structural configuration have been determined by various spectroscopic (electronic, IR, 1H NMR, 13C NMR, GCMS) techniques. Electronic and magnetic moments of the complexes indicate that the geometries of the metal centers are octahedral. These metal complexes were also tested for their antimicrobial activities to assess their inhibiting potential.

Nanomagnetic macrocyclic Schiff-base-Mn(ii) complex: an efficient heterogeneous catalyst for click approach synthesis of novel β-substitued-1,2,3-triazoles.

In the present work, a novel symmetrical 15-membered macrocyclic Schiff base complex of manganese was prepared using the reaction of the synthetic 2,6-diacetylpyridine functionalized Fe3O4 MNPs with 2,2-(piperazine-1,4-diyl)dianiline and Mn(ii) bromide salt via a template approach. The resulting [Fe3O4@PAM–Schiff-base–Mn][ClO4] heterogenized complex was characterized using FT-IR, XRD, BET, TGA, EDX, Xray-mapping, SEM, TEM and VSM analysis. To demonstrate proof of concept, Huisgen 1,3-dipolar cycloaddition synthesis of 1,2,3-triazoles was selected to evaluate the activity and reusability of the catalyst. The ethanol as a green solvent proved to be an excellent reaction medium for this synthesis. Yields of up to 100% were obtained in some cases. Significantly, as demonstrated, [Fe3O4@PAM–Schiff-base–Mn][ClO4] catalyst was recycled for 8 cycles without losing catalytic activity under the optimized reaction conditions. The hot filtration and ICP-OES tests ratified that there was no leaching of metal during the catalytic reaction, indicating the heterogeneous manner of the catalyst.

New 15-membered macrocyclic Schiff base ligand; synthesis some Cd(II), Mn(II) and Zn(II) complexes, crystal structure, cytotoxicity, antibacterial and antioxidant activity

Herein, we aim at preparing 15-membered-ring symmetrical pentaaza macrocyclic Schiff base complexes using a template approach, based on the condensation reaction of an amine containing piperazine moiety, 2,2-(piperazine1,4-diyl)dianiline, and 2,6-diacetylpyridine in 1:1 mol ratio while Cd(II), Mn(II) and Zn(II) metal ions are present. Moreover, FT-IR, mass spectrometry, magnetic susceptibility measurements, UV–Vis and, 1H and 13C NMR spectroscopy were used to characterize these Schiff base complexes. Besides, the structure of [C25H25N5CdBr][ClO4] was determined using a single crystal X-ray structural analysis. Being in a pentagonal planar coordination environment, the Cd atom is surrounded by a Br atom in the apical position and 5 nitrogen atoms in the pentagonal plane. We also aimed at screening the synthesized complexes to investigate their antioxidant activities applying the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging assay. also, their bactericidal activity was evaluated using a paper disk diffusion method against both Gram-negative and Gram-positive bacteria, revealing a strong antioxidant activity and moderate effectiveness against all the tested bacteria. Finally, it is worth mentioning that the complex cytotoxicity was evaluated against MCF-7 (breast) and A549 (lung) adenocarcinoma cells. Generally, as compared to [ZnLBr]ClO4 possessed a greater cytotoxic effect against the tested cells.

Synthesis and Characterization of Cr (III) Macrocyclic Schiff Base Complexes

Ninety Cr(III) macrocyclic Schiff base complexes of the type [CrL_n^(1-10) X_2 ]X(Where X = Cl- or NO-3 or CH3COO- and = macrocyclic Schiff base ligands derived from condensation of trimesic acid or p-phthalic acid or squaric acid with different aliphatic diamines) have been synthesised and characterised by elemental analysis; molar conductance; electronic spectra; IR; magnetic moment and XPS i.e. X-ray Photoelectron spectra data. An octahedral geometry was established for them.

The non-templating synthesis of macro-cyclic Schiff base ligands containing pyrrole and homopiperazine and their binuclear nickel(II), cobalt(II) and mononuclear platinum(II) complexes: X-ray single crystal and anticancer studies

A new dialdehyde N, N'-bis(5-formylpyrrol-2-ylmethyl) homopiperazine (A) was synthesized by the Mannich reaction of pyrrole 2-carbaldehyde, formaldehyde and homopiperazine in the presence of hydrochloric acid. From the direct reaction of A with 1,3-diaminopropane or 1,4- diaminobutane two new macrocyclic Schiff base ligands were obtained, L1 and L2, respectively. The reaction of these ligands with Ni(II), Co(II) and Pt(II) metal ions results in formation of the relevant macrocyclic Schiff base complexes. Compounds were characterized by FT-IR, elemental analysis, mass spectrometry, UV-Vis and, in the case of the ligands, by 1H and 13C-NMR. The crystal structure of the complex [Ni2L2(CH3O)]ClO4 (4) showed a binuclear macro-cyclic structure, with each Ni coordinated by three nitrogen atoms from the ligand and by a methoxide bridging the two metal centers. The cytotoxic activities of these compounds indicated that the ligands, and some of the complexes, have high anti-proliferative effect towards A549 and HeLa cells, but not HT29 cells. Pt complex with L1 and L2 displayed stronger anti-proliferative activity toward HeLa (IC50 = 11 µM for both of them and A549 IC50 = 7 µM and 8 µM, respectively) relative to L1 and L2. In addition, the cytotoxic effects of the compounds were assayed in rat fibroblast cells as a model of the normal cell, however none of them showed any significant cytotoxic effects. Thereby upholding the potential of these compounds for further development as chemotherapeutic agents.

Synthesis, spectroscopic characterization and biological studies of trivalent transition metal ion prompted macrocyclic Schiff base complex

AbstractTwo new macrocyclic Schiff base complexes of trivalent transition metal ion of Cr(III) and Fe(III) in their nitrates form have been synthesized and fully characterized by elemental analysis and spectroscopic techniques, namely, IR, UV, ESI‐MS and ESR. The route of template methodology was adopted for the synthesis of the complexes. The electrolytic nature of the complexes is elucidated with the help of molar conductance measurements. The magnetic moments values give a prediction regarding the presence of unpaired electron. Antimicrobial studies of the synthesized complexes have been carried out for the evaluation of their biological efficacies as potential antimicrobial agents.

1+1] Copper(II) macrocyclic Schiff base complex on rGO as a photocatalyst for reduction of nitroaromatics compounds under visible-light irradiation

In this work, [1 + 1] macrocyclic Copper(II) Schiff base complex ([CuL](NO3)2.H2O) was synthesized and grafted on reduced graphene oxide successfully. The novel prepared sample was characterized by physico-chemical techniques and used as a photocatalyst for the reduction of nitroaromatic compounds to their amine derivatives at room temperature under visible-light irradiation with hydrazine mono hydrate. From the prepared samples, reduced graphene oxide loaded with 30% [CuL](NO3)2.H2O catalyst (rGO/CuM30) shows the best efficiency for converting different nitroaromatic compounds to the corresponding amino compounds using visible light. As-prepared catalyst illustrated excellent activity for the reduction of 2-nitrophenol to 2-aminophenol (100% conversion) in only 90 min. Finally, the catalyst could be recovered for five times and reused without decreasing of its efficiency.

Synthesis, cytotoxicity, and antioxidant activity by in vitro and molecular docking studies of an asymmetrical diamine containing piperazine moiety and related Zn(II), Cd(II) and Mn(II) macrocyclic schif base complexes

Three new Zn(II), Cd(II) and Mn(II) macrocyclic Schiff base complexes have been prepared via the Mn(II), Cd(II), and Zn(II) templated [1 + 1] cyclo condensation of phtalaldehyde with an asymmetrical diamine, 2-((4-(2-((2-amino benzyl)amino)ethyl)piperazine-1-yl)methyl)aniline. The complexes have been characterized by elemental analysis, IR, ESI-MS, and NMR spectroscopy. The cytotoxicity of the compounds was evaluated against three different cancer cell lines, including MCF-7 (breast), A549 (lung), and AGS (gastric) adenocarcinoma cells. In general, Cd-complex possesses a higher cytotoxic effect against the tested cells than the Zn, and Mn-complexes. Besides, antioxidant activity assays displayed that Cd, and Zn complexes had significant antioxidant potencies compared to ascorbic acid and quercetin, due to the standards. In addition, the biological assessment of synthesized complexes was examined via molecular docking. Findings showed that the Cd-complexes have the highest inhibition effect against cytotoxic and antioxidant receptors.

Spectroscopic, SOD, anticancer, antimicrobial, molecular docking and DNA binding properties of bioactive VO(IV), Cu(II), Zn(II), Co(II), Mn(II) and Ni(II) complexes obtained from 3-(2-hydroxy-3-methoxybenzylidene)pentane-2,4-dione

Novel macrocyclic Schiff base complexes [[ML]X; where M = Cu(II), Co(II), Ni(II), Zn(II), Mn(II) and VO(IV); L = macrocyclic ligand; X = Cl2 and SO4 2−] have been synthesized and characterized by microanalytical, 1H, 13C NMR, IR, Mass, UV–Vis, EPR spectral studies, as well as conductivity data. All the complexes exhibit square-planar geometry except vanadium complex. Magnetic susceptibility measurements and high conductance data reveal the monomeric and electrolytic nature of the complexes. Electronic absorption, cyclic voltammetry, viscosity measurements have been carried out on the interaction of the complexes with DNA. The results suggest that the complexes bind to DNA by intercalation via the aromatic ring of the macrocycle into the base pairs of DNA. Using gel electrophoresis experiment in the presence and absence of oxidant (H2O2) the nuclease cleavage activity of the complexes has been performed on plasmid DNA. The results demonstrate that most of the complexes have promising superoxide dismutase (SOD)-mimetic activity. The in vitro cytotoxicity of ligand and its complexes has also been evaluated against human breast and colon carcinoma cells. Binding interactions and energies of ligand and its metal complexes [ML]2+ (M = VO(IV), Mn(II), Co(II), Ni(II), Cu(II), Zn(II)) against the receptors EGFR and HER2 are performed using the Auto dock module. Consequently, it is found that the ligand is strong inhibitor for EGFR and HER2 while [VOL]SO4 is good inhibitor for EGFR and [ZnL]Cl2 is moderate inhibitor for HER2. The antimicrobial activity of the ligand and its complexes against bacteria Salmonella typhi, Staphylococcus aureus, Escherichia coli and Bacillus subtilis and fungi Aspergillus niger, Aspergillus flavus, Candida Albicans and Rhizoctonia bataicola. The complexes have higher activities than the macrocyclic free Schiff base. Communicated by Ramaswamy H. Sarma

Transmetalation and Demetallization for Open-Oyster-like Non-Ionic Cd(II) Macrocycles.

This work designed a nonionic extended dialdehyde 6,6'-(phenylazanediyl)dipicolinaldehyde (PDPA) for constructing Schiff-base macrocyclic complexes with weaker metal-ligand interactions, so as to solve the long-standing challenges of transmetalation and demetallization in macrocyclic complexes. An enantiomeric pair of open-oyster-like 26-membered [2 + 2] Schiff-base macrocyclic dinuclear Cd(II) complexes (S,S-1a, R,R-1b) could be obtained, having S,S/R,R-1,2-diaminocyclohexane (S,S/R,R-DACH) precursors, while Cu(II) ion template only resulted in a mononuclear Schiff-base Cu(II) acyclic complex (S,S-2) accompanied by the half-oxidation of PDPA instead of expected [2 + 2] Cu(II) macrocyclic complexes. It is suggested that the weak oxidization capability of Cu(II) ion is responsible for the formation of S,S-2 because X-ray photoelectron spectroscopy (XPS) for the solid powder of reaction mixture of direct Cu(II) ion template synthesis implies that both Cu(I) and Cu(II) species are present. In fact, corresponding [2 + 2] dinuclear Cu(II) macrocycles and even metal-free macrocycles unsuitable for direct synthesis can be obtained via Cd(II) → Cu(II) transmetalation and Na2S demetalation verified by ESI-MS and UV-vis spectra. In addition, control experiments indicate that the synthesis of metal-free macrocycles via the direct nontemplate method merely results in the mixture of multiple components of [1 + 1], [2 + 2], and [3 + 3] Schiff-base macrocycles, and they are difficult to isolate.

Interlocking a synthesized polymer and bifunctional filler containing the same polymer's monomer for conformable hybrid membrane systems

Extra high-performance MMMs were fabricated by embedding a bifunctional host/guest complex (Schiff base macrocyclic copper complex in the FAU super-cages of zeolite 13X) into the 6FDA-durene matrix and examined for CO2/light gas separation.

Macrocyclic Schiff base complexes as potent antimicrobial agents: Synthesis, characterization and biological studies.

A series of CuII, CoII, ZnII and NiII, complexes of 34,74-dimethyl-12,15,52,55-tetrahydro-2,4,6,8-tetraaza-1,5(2,5)-difurana-3,7(1,2)-dibenzenacyclooctaphane based ligand have been synthesized by template methodology. Characterization of the synthesized complexes has been carried out with the help of various physicochemical and spectroscopic techniques like Infra-Red, ESI-MS, ESR, UV-visible, CHN (elemental analyses), molar conductance, magnetic moment and NMR. Antimicrobial efficacy of the newly designed macrocyclic complexes has performed by the assistance of agar well diffusion method. In-vitro hemolytic and DNA binding studies were also performed in order to analyze or interpret the mode and binding efficiencies as well as the % hemolysis exhibited by the complexes. DFT/TD-DFT studies were carried out in order to elucidate the better insight into the structural parameters. Energy minimization and quantum chemical parameters were calculated using Gaussian09W program.

Designing of a magnetically separable Fe3O4@dopa@ML nano-catalyst for multiple organic transformations (epoxidation, reduction, and coupling) in aqueous medium

A copper(II) macrocyclic Schiff base complex (ML) was synthesized by condensation between 2,2-dimethylpropane-1,3-diammine and 2,6-diformyl-4-butylphenol with the aim to modify the surface of widely used magnetically separable nanocatalyst Fe3O4@dopa. ML was characterized by physicochemical techniques and single crystal X-ray diffraction. The newly synthesized heterogeneous catalyst Fe3O4@dopa@ML was characterized by SEM, TEM, PXRD, EDX, TGA, etc. ML showed stability in aqueous medium and utilizing this unique property, the heterogeneous catalyst Fe3O4@dopa@ML was used for catalyzing epoxidation, nitroarene reduction and C–C coupling (Henry reaction) in aqueous medium. The separation method of the prepared nano-catalyst is very easy and can be done with an external magnetic field. The experimental findings suggest that Fe3O4@dopa@ML is a versatile “green catalyst.”

Coordination chemistry of some new Mn(II), Cd(II) and Zn(II) macrocyclic Schiff base complexes containing a homopiperazine head unit. Spectral, X-ray crystal structural, theoretical studies and anticancer activity

Here we report a number of novel macrocyclic Schiff base complexes with a homopiperazine skeleton. These symmetrical pentaaza macrocyclic Schiff base complexes were prepared via a template approach, based on the condensation reaction of an amine containing homopiperazine moiety and 2,6-diacetylpyridine or 2,6-pyridine dicarboxaldehyde in 1:1 mol ratio in the presence of Cd(II), Mn(II) and Zn(II) metal ions. These Schiff base complexes were characterized by elemental analyses, FT-IR, mass spectrometry and, in the cases of diamagnetic Zn(II) and Cd(II) complexes, 1H and 13C NMR spectroscopy. As well, the structures of [Mn(L1)(CH3OH)(ClO4)]ClO4 and [Cd(L2)(H2O)2](ClO4)2 have been determined by X-ray structural analyses, where the L1 and L2 are the products of the reaction of the new amine with 2,6–Pyridinedicarboxaldehyde or 2,6–diacetalpyridine, respectively. The coordination environment of the metal atoms in both of these complexes is best described as a distorted pentagonal bipyramid. The cytotoxic activities of these new complexes were also examined. The potency of complexes to induce cell death was screened on A2780, U37 MG, and H1299 cell lines, compared to doxorubicin which was used as a control. The results reveal that in some cases, the cytotoxic activity of complexes was stronger than that of doxorubicin as standard. Also, the bonding situation in the complexes, were analyzed by NBO and energy-decomposition analysis (EDA) and EDA-NOCV analysis.