Neutral Bidentate Research Articles

Design, synthesis, characterization, DFT, molecular docking, and in vitro screening of metal chelates incorporating Schiff base

Hydrazones, with an azomethine -NHN=CH group, are extensively researched due to their easy preparation and numerous pharmaceutical benefits. A hydrazone derivative was formed by combining N,N-dimethyl amino benzaldehyde (1) and hydrazine hydrate (2), producing-4-(methanehydrazonoyl)-N,N-dimethylaniline (3). The final product (H1L) ligand was produced by reacting with ethyl acetate. The new complexes were formed by reacting Co(II), Ni(II), Cu(II), and Zn(II) with the ligand in a 1M:2L molar ratio. Complexes were synthesized with high yields. Metal chelate structures were identified through elemental analyses, FT-IR, magnetic moment, XRD, and molar conductivity tests. According to FT-IR findings, the Schiff base ligand displayed neutral bidentate properties by binding with metal ions via the azomethine N and carbonyl O. Magnetic moment research indicated an octahedral structure and high electrolytic properties, with the exception of Co(II) and Zn(II) complexes, which were observed to be non-electrolytes. Theoretical calculations were performed using DFT. The synthesized complexes were tested for antibacterial activity against two types of Gram-positive bacteria: S. aureus and B. subtilis. Molecular docking analysis revealed information about the ligand's binding energy and interaction with the S. aureus receptor. KEY WORDS: Hydrazinylidene, DFT, Antibacterial activity, Molecular docking Bull. Chem. Soc. Ethiop. 2024, 38(6), 1625-1638. DOI: https://dx.doi.org/10.4314/bcse.v38i6.10

1,4-diaminophthalazine complexes of Re(CO)3

1,3-Diiminoisoindolines and substituted variants react with hydrazine to produce 1,4-diaminophthalazines. In this paper, we present the chemistry of 1,4-diaminophthalazine and two modified versions with the Re(CO)3 unit. The 1,4-diaminophthalazine ligand forms a bimetallic complex similar to that seen with unmodified phthalazine. In contrast, the semihemiporphyrazine-derived chelating ligands bind Re(CO)3 as neutral bidentate compounds; the freebase pyrazole and indazole modified 1,4-diaminophthalazines exhibit multiple tautomerization states with ionizable protons. Notably, protonation of the meso bridging nitrogen atom reduces the degree of conjugation between the two halves of the chelate, resulting in a diimine-like complex that lacks significant absorption in the visible spectrum due to the abrogation of the low energy metal to ligand charge transfer (MLCT) transition.

Coordination Chemistry of Calix[3]Pyrrole-Related Macrocycles

Calix[3]pyrrole is a ring-contracted porphyrinogen-like macrocycle in which three pyrrole units are linked by three sp3-carbon atoms at the a-positions. While synthetic routes to calix[3]pyrrole and its furan and thiophene derivatives have been established using oligoketone precursors,[1–3] their coordination chemistry remains fully unexplored. Here, the author reports the direct macrocyclization synthesis and metal complexation properties of novel thiazole-containing calix[3]pyrrole analogues that exhibit better metal chelation than that of calix[3]pyrrole.Treatment of calix[3]pyrrole (1) with n-butyl lithium (4 eq.) resulted in the deprotonation of all the NH protons to generate a tridentate trianionic ligand. Successive reaction with BBr3 furnished a boron(III)-complex 2 in 25% isolated yield. However, attempts to synthesize stable complexes with other metal ions were unsuccessful. The obtained boron complex 2 were unusually stable towards acids; even in pure trifluoroacetic acid (TFA) or methanesulfonic acid, no deboronation was observed, instead, protonation at a pyrrole carbon atom was detected by NMR spectroscopy.In order to generate isolable metal complexes with calix[3]pyrrole-related macrocycles, we have designed calix[1]pyrrole[2]thiazole (4). Calix[1]furan[2]thiazole (3), a precursor of 4, was synthesized by direct macrocyclization between bis(a-bromoketone) and 2,2-dimethylpropanebis(thioamide) in 60% yield. While calix[3]pyrrole (1)undergoes a strain-induced ring expansion reaction to give calix[6]pyrrole under acidic conditions, less strained 3 was stable in TFA, thus its furan moiety was hydrolyzed to a diketone moiety. Further Paal–Knorr pyrrole formation reaction led to the formation of 4 in 78% yield.When macrocycle 4 was mixed with Et2Zn, monoethyl zinc complex 5 was formed in 72% yield. Single crystal X-ray analysis revealed that 4 adopted a C s-symmetric cone conformation to behave as a monoanionic tridentate ligand. Due to the steric protection of the ethyl zinc center by meso-methyl groups, organozinc complex 5 was stable in the presence of excess water or alcohol at room temperature.Complexation of 4 with Pd(MeCN)4(BF4)2 afforded cationic palladium complex 6 in which macrocycle 4 adopted a partial cone conformation to chelate a Pd2+ ion as a neutral bidentate ligand. Similar complexation behavior was also observed with AgBF4, demonstrating conformational flexibility of macrocycle 4 upon metal complexation. Furthermore, coordination-driven self-assembly was confirmed for Ag+ complex of 4.In this presentation, the detailed synthesis and electronic properties of the metal complexes of calix[3]pyrrole-related macrocycles will be discussed.

Investigation of structural, spectral, theoretical, and antimicrobial properties of Iron(III) complexes with thiosemicarbazide ligands

Different thiosemicarbazide ligands, (H2PAPS), (H2PAPT), (H2PABT), have been utilized to synthesize a series of Fe(III) complexes. These complexes were characterized using conventional techniques, and their chemical formulas were determined as [Fe(H2PAPS)Cl3], [Fe(H2PAPT)Cl3(H2O)], and [Fe(HPABT)Cl2(H2O)], respectively. The spectral analysis of the Fe(III) complexes showed that H2PAPS coordinate as a neutral tridentate, while H2PAPT suggests its coordination as a neutral bidentate but in the case of H2PABT, it acts as a mononegative tridentate. The proposed structures of all complexes were found to be octahedral. Confirmation of the geometries of the ligands and their Fe(III) complexes, various parameters were calculated using DFT (density functional theory) with the Materials Studio program. Thermal degradation studies of the complexes were conducted. Additionally, the antibacterial activities of the ligands and their Fe(III) complexes were evaluated. The results showed that Fe(III) complexes exhibited greater antibacterial effects compared to their the free ligands, except for [Fe(H2PAPT)Cl3(H2O)], which demonstrated lower activity than its corresponding ligand. Interestingly, the ligands demonstrated higher cytotoxicity compared to fluorouracil (5-FU), a known anticancer drug. However, the Fe(III) complexes showed lower activity compared to their corresponding ligands in the tested cell lines.

Bidentate bromhexine drug coordination modes with various transition metal ions: Synthesis, characterization, and in vitro antibacterial and anti-breast cancer activity tests

BackgroundBromhexine (BHX) is a mucolytic drug used in treatment the respiratory disorders which are associated with excessive or viscid mucus. Transition metal complexes have made tremendous progress in the treatment of a variety of human ailments, according to reported articles. Transition metal complexes are being developed as medications with a lot of effort. Metal complexes can form a variety of coordination geometries, giving them distinct forms. So, binary metal complexes of bromhexine drug have been prepared to enhance the biological activity and stability of the free drug. MethodsA new series of binary complexes with bromhexine drug (BHX) has been prepared with some transition metal ions namely Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II). Elemental analyses, FT-IR, mass spectrometry, thermal studies and UV-Vis spectra have been used to characterize and structurally elucidate the produced metal complexes. Antibacterial activity has been tested for the ligand and metal complexes against a variety of pathogenic bacterial species (Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus). In addition, the ligand has been tested for anticancer efficacy against the MCF-7 breast cancer cell line, as opposed to binary metal complexes. The binding orientation or conformation of the free BHX ligand and Co(II) complex in the active region of the protein of crystal structure of Escherichia coli (PDB ID: 3T88) and Pseudomonas aeruginosa (PDB ID: 6NE0) has been performed using molecular docking studies. ResultsThe BHX ligand coupled in neutral bidentate mode to the metal ions, according to FT-IR and 1H-NMR spectral results. The molar conductivity measurements of the complexes in DMF proved the electrolytic nature of all binary complexes. Co(II) complex showed the highest inhibition zone diameter against S. aureus, E. coli and P. aeruginosa. Zn(II) complex had the greatest inhibitory effect against P. aeruginosa and B. subtilis. Also, Cd(II) chelate appeared high efficacy as antibacterial agent against Pseudomonas aeruginosa and Staphylococcus aureus. ConclusionAll the output data conjugated to confirm the octahedral geometry of the metal complexes. The biological findings revealed that metal complexes can be more active than the free BHX ligand. Against MCF-7 cell line, Cd(II)-L complex is highly active complex (4.95 µg/mL) but BHX free drug is the most active compound (3.96 µg/mL).

Synthesis, structure and effects of an azoimine functionalized iridium complex on cancer cells

A novel ligand L having azoimine bond with quinoline moiety reacts with [(2-ppy)2Ir(μ-Cl)]2 in dichloromethane medium to produce an iridium(III) complex of composition [Ir(2-ppy)2(L)]. Here, the iridium centre is bound to neutral bidentate N, N donating sites of the ligand (L), where the azo part of L is not involved in chelation. The ligand and complex are characterized by elemental analysis, NMR spectroscopy, ESI-MS mass spectrometry, FTIR, UV–Vis and luminescence spectroscopic techniques. The ligand structure and the geometry around iridium centre of complex [Ir(2-ppy)2(L)] is confirmed by the single-crystal X-ray diffraction (XRD) method. DFT studies were also performed to support the experimental aspects of the complex as well as electronic distribution in molecular orbitals of various energy states. The complex exhibits blue emission band at 428 nm with quantum yield (Φ) 0.136. Further, in vitro analysis of the anticancer activity of the complex was studied mainly with the MCF - 7 cell line. The results showed that the complex have good IC50 values when compared to the standard drug cisplatin.

Mixed ligand 4‑hydroxy acetanilide-febuxostat complexes of Co(II),- Ni(II), Cu(II) and Zr(IV): Synthesis, structural characterization, DFT calculations, antibacterial, antioxidant and molecular docking studies

The synthesized mixed ligand metal complexes were achieved by a combination of febuxostat (2-(3-cyano-4-isobutyloxyphenyl)-4-methyl-5-thiazolecarboxylic acid) (FEB) and paracetamol (4‑hydroxy acetanilide) (Para) together with crucial biologically relevant elements. These elements, including Co(II), Cu(II), Zr(IV), and Ni(II) chlorides, play important roles in various biological systems and mechanisms, such as antioxidant, antimicrobial systems, and contribute to diverse functions and structures. To identify chemical formulae and structures of synthesized complexes, physical-analytical, spectroscopic (XRD, FT-IR, ESR, 13C NMR, 1H NMR, and UV-visible), mass spectrometry (MS), TG-DTG studies were used and supported by computational approaches. FT-IR and 1H NMR data revealed that FEB chelated through sulfur of thiazole ring as a mono-negative bidentate type and deprotonated oxygen of carboxylate group, according to lack of characteristic band at 1677 cm−1 and signal at δ = 13.37 ppm (-OHCOOH), whereas Para chelated through nitrogen and oxygen of amide group as a neutral bidentate ligand. Magnetic moment and electronic spectra data revealed that complexes have an octahedral structure. The optical band gap (Eg) for our compounds was calculated and according to Eg values, all complexes were semi-conductors and fell into the class of solar materials compared with FEB and Para. XRD pattern showed the monoclinic polycrystalline structure for all compounds except the Zr(IV) complex was amorphous. Kinetic parameters of the thermal decomposition stages were calculated. DFT was utilized to confirm bonding mode for FEB and Para with metal ions and according to calculations of energy band gap (ΔE) of complexes, Cu(II) complex with smaller ΔE is more reactive but, Zr(IV) complex with higher ΔE is less reactive than FEB and Para. The antibacterial activity of FEB, Para, and their complexes were tested against two G-ve and three G+ve bacteria. Co(II) complex displayed remarkable effectiveness and high significance against all strains of bacteria, compared with other compounds tested. All compounds demonstrated antioxidant effects, Cu(II) and Zr(IV) show greater antioxidants than parent ligands with IC50 values 0.040 and 0.057 mg/mL. The binding pattern and active site of all compounds were put through molecular docking studies and compared with empirical biological data.

Green approach to synthesize novel thiosemicarbazide complexes, characterization; DNA-methyl green assay and in-silico studies against DNA polymerase

A thiosemicarbazide derivative as (E)-4-ethyl-1-(1-(naphthalen-1-yl) ethylidene) thiosemicarbazide (HAN) was synthesized then characterized to prepare [Co(HAN)Cl2·(H2O)2], [Ni(HAN)Cl2·(H2O)2]. H2O, and [Cd(HAN)Cl2] complexes. According to spectral and analytical data we could confirm the neutral bidentate mode of bonding via (C]S) and (C]N) groups to form 1:1 M ratio within the three complexes. The octahedral geometry was suggested for Co(II) and Ni(II) complexes according to electronic transitions assigned to 4T1g → 4T1g(P)(ʋ2) and 4T1g → 4A2g(F)(ʋ3) and 3A2g → 3T1g(P,υ3) and 3A2g → 3T1g(F,υ2), respectively. The values of nephelauetic ratio (β) in the ligand field parameters detect the ionic nature of new M-L bonds. The molecular ion peaks appeared in the mass spectra of two selected complexes confirming their molecular formulae. The conductometric study was performed for Cd(II) ion solution during variable additions of HAN to calculate association and formation constant of Cd(II)-HAN complex. DFT/B3LYP method was used to optimize the structures of the compounds and confirm the binding mode of the ligand. The distribution of C(5) = N(17) and C(13) = S(19) groups asserts their priority in coordination. Hirshfeld crystal properties were obtained via normalized contact distance (dnorm) and shape index in which the nitrogen atoms act as the best contact points in crystal packing. The biological screening was carried out against microbial strains as well as methyl green/DNA test. In vitro, the superiority of the ligand was clearly recorded in its biological effectiveness. In silico methods were implemented to confirm the activity of the ligand and to recognize the interaction features. The bioavailability, pharmacokinetics and drug-likeness were evaluated via Swiss-link. The data detect the ability of the ligand to penetrate barrier of brain (BBB) but not absorbed in gastrointestinal tract. Pharmit link and molecular docking were utilized to investigate the interaction of HAN with 1bna, 425d and 2k4l proteins. The best intercalation with protein pockets was observed with 2k4l protein, and searching the MolPort library detects a drug analog of MolPort-002-894-701. Finally, the results suggest the biological efficiency of the ligand, which may be asserted by specialists through intensive in-vivo studies.

Synthesis, Spectroscopy and Biological Activities of Some Trivalent Lanthanide Complexes of Octadecyl N-salicylaldimine (ONsal)

A series of Ln(III) complexes of octadecyl N-salicylaldimine (ONsal) were synthesized and characterized by CHN analysis, magnetic moment, conductivity, thermoanalytical and spectroscopic methods. Elemental and thermal analysis data confirmed the formation of heptacoordinated [Ln(ONsal)2Cl2(H2O)]Cl complexes where Ln = Ce3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, which is further supported by the respective mass spectra. The ligand acts as a neutral bidentate species coordinating through azomethine nitrogen and phenolic O-atom. The linkage of one H2O molecule in all the complexes has been inferred from the thermal analysis. All the Ln(III) complexes are paramagnetic in nature and act as 2:1 electrolyte in 0.002 M DMF at 25 ºC. The complexes of Sm(III), Eu(III) and Tb(III) display luminescent properties. The powder XRD patterns of Nd(III) and Dy(III) complexes could be successfully indexed for monoclinic crystal systems, while the diffraction lines of Eu(III) complex are indexed for a triclinic crystal system. Methanolic solutions of the ligand and complexes were checked for α-glucosidase and α-amylase inhibitory properties where some of the Ln(III) complexes show significant α-glucosidase inhibitory potency while only Tb(III) complex shows inhibition against α-amylase.

Palladium(ii), platinum(ii), and silver(i) complexes with 3-acetylcoumarin benzoylhydrazone Schiff base: Synthesis, characterization, biomolecular interactions, cytotoxic activity, and computational studies.

New Pd(ii) (C1), Pt(ii) (C2), and Ag(i) (C3) complexes derived from 3-acetylcoumarin benzoylhydrazone (HL) Schiff base were synthesized and characterized by FTIR, 1H NMR, UV-visible spectroscopies along with elemental analysis (C, H, N), magnetic, molar conductivity measurements, and DFT calculations. The obtained results suggested that the ligand had different behaviors in the complexes: mono-negative tridentate (C1) and neutral tridentate (C2) as an ONO-donor and neutral bidentate (C3) as an ON-donor. Quantum chemistry calculations were performed to validate the stability of the suggested geometries and indicated that all the complexes possess tetra-coordinated metal ions. The binding affinity of all the compounds toward calf thymus (ctDNA), yeast (tRNA), and bovine serum albumin (BSA) was evaluated by absorption/emission spectral titration studies, which revealed the intercalative binding to ctDNA and tRNA and static binding upon complex formation with BSA. Molecular insights into the binding affinity of the characterized complexes were provided through conducting molecular docking analysis. Moreover, the cytotoxic activity (in vitro) of the compounds was screened against human cancerous cell lines and a non-cancerous lung fibroblast (WI38) one using cis-platin as a reference drug. The IC50 and selective index (SI) values indicated the higher cytotoxic activity of all the metal complexes compared to their parent ligand. Among all the compounds, the complex C2 showed the highest activity. These results confirmed the improvement of the anticancer activity of the ligand by incorporating the metal ions. In addition, flow cytometry results showed that complexes C1 and C2 induced cell cycle arrest at S and G1/S, respectively.

Synthesis, structural, spectroscopic and electric/dielectric studies of a nanocrystalline Ni(ii) complex based on [(1,3-diphenyl-1H-pyrazol-4-yl)methylene]thiocarbonohydrazide.

A Ni2+ nanocomplex based on a heterocyclic ligand containing a pyrazole moiety was developed in this work, and its electric conductivity and dielectric characteristics were studied. The Ni2+ nanocomplex with the general formula [Ni(PyT)2(H2O)2]Cl2·½H2O, where PyT = [(1,3-diphenyl-1H-pyrazol-4-yl)methylene]thiocarbonohydrazide, was characterized using various techniques, including elemental and thermal analyses, as well as conductivity, magnetism, TEM, and spectroscopic (FT-IR, UV-Vis and XRD) studies. The results showed that PyT was bonded to the Ni(ii) centers via a neutral bidentate ligand, resulting in an octahedral-shaped, thermally stable mononuclear complex. The frequency response of the dielectric properties and ac conductivity was studied in the range from 200 Hz to 6 kHz. Both dielectric constant and dielectric loss decreased with increasing frequency. In addition, the effect of temperature was investigated in the range of 294.1-363.4 K. The ac conductivity increased with increasing temperature in the range of 294.1-333.5 K. The ac conduction is described as correlated barrier hopping between non-intimate valence alternation pairs. Furthermore, the PyT and Ni(PyT) nanocomplex structures were optimized using theoretical calculations and DFT computations.

Comparison on biological inspection, optimization, cyclic voltammetry, and molecular docking evaluation of novel bivalent transition metal chelates of Schiff Base pincer ligand

The presented work introduces a comprehensive study of the ligation behavior of the Schiff base ligand N-3-phenylallylidene nicotinohydrazide HNP toward transition metal cations, VO(II), Cu(II), and Cd(II), to synthesize novel solid chelates and examine their biological potencies. The ligand and its chelates were structurally elucidated using a diverse array of spectroscopic techniques, including FT-IR, UV–visible, 1H/13C NMR, ESR, PXRD, SEM, EDX, and LC/GCMS, besides thermal analysis TG/DTA, magnetic measurements, conductivity measurements, and elemental analysis. The comparison between the FT-IR spectra of both the ligand and its chelates revealed that HNP coordinated as a neutral bidentate with VO(II) and Cd(II) ions, while it coordinated as a mono-negative bidentate with the Cu(II) ion. The electronic absorption spectra depicted absorption bands at 19342 and 14925 cm−1 for the VO(II) and Cu(II) complexes, respectively, predicting square pyramidal and square planner arrangements. The cyclic voltammetry technique was used to study the electrochemical behavior of the Cu(II) ion in the absence/presence of HNP, whereas the chelation process in solution occurred spontaneously. Computational studies were applied using the Gaussian 09 program on the molecular structure of the isolated compounds based on the DFT/LAN2DZ/RB3LYP method to assess some chemical quantum parameters and perform correlation analyses between the theoretical and experimental FT-IR spectra. The values of R2 ranged from 0.99 to one, revealing a strong correlation between the theoretical and experimental data. Furthermore, molecular docking studies of the prepared compounds with the target proteins were performed using the MOE program. The docking results suggested that the VO(II) complex tended to be a biologically effective compound, wherein the VO(II) complex recorded inhibition grades of -6.16, -6.95, and -6.38 kcal/mol toward the target proteins and RMSD values of 0.92, 0.85, and 0.88 Å. Finally, the ligand and its complexes were screened for various biological assays, which highlighted the biological activity of the VO(II) complex. The VO(II) complex ranked as the highest antimicrobial with activity index values of 37.5, 59.1, and 26.9% against E. coli, Bacillus subtilis, and C. albicans, respectively. In addition, the VO(II) complex ranked as the highest antioxidant with an IC50 value of 63.09 μM and the highest capacity for DNA binding with an IC50 value of 43.8 μM. Furthermore, the VO(II) complex exhibited the highest cytotoxicity with IC50 values of 26.8, 21.8, and 32.4 μM against HePG-2, MCf-7, and Hela cell lines, respectively. Accordingly, this comprehensive study provides insight into the possible uses of these innovative chelates as potential therapeutics and enhances our comprehension of their molecular interactions and biological effectiveness.

Synergistic anti-fungal action of azole compounds with mixed ligand complexes and their applications

Selenium (Se (II)) and Zinc (Zn (II)) mixed ligand complexes containing glycine (gly) and pyroglutamic acid (l-PCA) as primary ligands, and salicylic acid (HL1) and glycolic acid (HL2) as secondary ligands have been prepared. These novel complexes were characterized using elemental analysis, 1H NMR, 13CNMR, UV–Vis., FTIR, X-ray diffraction, mass spectra and thermal analysis. The elemental analysis revealed the formation of [1:1:1] zinc or selenium amino acid-hydroxy acid complexes.The bonds interactions between Se (II), Zn (II), and ligands had been investigated using IR spectrophotometry revealing that the ligands exhibited neutral bidentate behavior; the amino acid (primary ligand) coordinates through the nitrogen atom and the carbonyl group's oxygen atom, whereas the hydroxy acids HL1 and HL2 (secondary ligands) coordinate through the OH group and the carbonyl group's oxygen atom.Electronic absorption spectra of the mixed-ligand complexes indicate a square planar shape. The prepared mixed ligand complexes were encapsulated with another powerful antifungal agent, climbazole, in nanostructured lipid carriers (NLCs) for topical application to improve the therapeutic activity. The NLCs were prepared by a hot homogenization method and characterized by particle size, drug entrapment, in vitro drug release, and zeta potential to guarantee the stability of the desired nanostructured lipid carriers (NLCs). The microbiological activity of climbazole-mixed ligand complexes and their encapsulated forms were assessed against Malassezia furfur, Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans and Escherichia coli. In comparison to Se (II) and Zn (II) mixed ligand complexes alone, the study revealed that the combination of Se (II) and Zn (II) mixed ligand complexes with climbazole in NLCs considerably increased antibacterial activity against the tested microbial strains. P ≤ 0.05 indicates statistical significance for the difference.

SYNTHESIS, CHARACTERIZATION AND XRD ANALYSIS OF COPPER (II) AND IRON (II) COMPLEXES OF BENZOIC ACID HYDRAZIDE.

Schiff bases are an important class of organic compounds, which play an important role in medicinal and pharmaceutical applications. Metal complexes formed by the reactions of keto forms of Benzoic acid hydrazide (BAH) with Cu(II) and Fe(II) sulphate ions were prepared and characterized by X-ray Diffraction analysis (XRD), Fourier Transform Infrared (FTIR) and electronic absorption spectra studies. The results showed that the hydrazides reacted with the metal salts in 1:2 molar ratio in all the complexes and acts as neutral bidentate ligands. The X-ray diffraction (XRD) pattern of the metal complexes provides a detailed comparative account of the behavior of the metal complexes of hydrazide ligand metal complexes. The pattern of BAH complexes shows the main characteristics peak and broad shoulder. In view of the relative half value width (FWHM), it may be concluded that the BAH-Cu is partially crystalline and while the BAH-Fe shows an amorphous nature. The broad characteristic peak indicates the amorphous nature of the polymers. The solubility test on the ligands and its metal (II) complexes revealed their solubility in ethanol and dimethylsulphoxide (DMSO). The infrared spectra of the hydrazide showed that ?(C=O), the carbonyl stretching mode, the coupling between the in-plane bending ?(N-H) and ?(C-N) and the stretching frequency for the amino group ?(NH2) all experienced shifts to lower wave numbers in the complexes suggesting the coordination of the moieties to the metal ions. The electronic absorption spectra of Cu(II) complexes showed absorption band located at 36,496 cm-1 showing a tetrahedral geometry while Fe(II) BAH and BAH ligand show absorption band at a shoulder around 16051 cm-1 with 4A2 ? 4T1 (P) respectively consistent with a four coordinate tetrahedral geometry.

Syntheses, structures, Hirshfeld surface analyses, BSA interactions and molecular docking studies of two leucine Schiff base complexes of oxovanadium(IV)

Two mixed-ligand oxovanadium(IV) complexes with a Schiff base derived from o-vanillin and leucine and 1,10-phenanthroline or 2,2´-bipyridine as a co-ligand, [VO(o-van-Leu)phen] (1) and [VO(o-van-Leu)bipy]·H2O (2), were prepared and structurally characterized by IR spectra, elemental analyses and single-crystal X-ray diffraction. The crystal structures reveal that each oxovanadium(IV) atom in complexes 1 and 2 is surrounded by a N3O3 coordination sphere to form a distorted octahedron with a Schiff base and neutral bidentate ligand phen or bipy. Hirshfeld surface analyses and 2D fingerprint plots indicated that the molecular packings in crystals were dominated by H···H, O···H/H···O, C···H/H···C and π-π interactions. The interactions of both complexes with bovine serum albumin (BSA) were studied by using various spectroscopic and molecular docking methods. BSA binding constants (K), estimated by UV–Vis spectroscopy, were 2.53 × 104M−1 for 1 and 3.18 × 104M−1 for 2, respectively. Together with results of fluorescence and CD spectral studies, it showed that complex 2 has a better affinity for BSA than complex 1. Molecular docking investigation indicated that the two complexes had the similar mode of binding and located within subdomain IIA of BSA. Complex 2 had greater binding activity with the binding free energy (∆Gbinding) of –6.5 kcal/mol than Complex 1 with ∆Gbinding of–5.42 kcal/mol, consisting with the analyses of spectroscopic experimental results.

3-acetyl-coumarin-substituted thiosemicarbazones and their ruthenium, rhodium and iridium metal complexes: An investigation of the antibacterial, antioxidant and cytotoxicity activities

A series of ruthenium, iridium and rhodium half-sandwich complexes containing 3-acetyl chromen-2-one-4(N)-substituted thiosemicarbazone derivatives have been prepared for use as antibacterial and anticancer agents. These complexes have been isolated as cationic bidentate (N, S) and neutral bidentate (N, S) complexes. The complexes have been characterized by spectral techniques (FT-IR, UV-Vis, NMR and HRMS) and single-crystal X-ray crystallography methods. The structure of complex 6 has been determined by a single-crystal X-ray diffraction study, which shows that coordination of the 3-acetyl chromen-2-one-4(N)-substituted thiosemicarbazone ligand to the metal occurs via azomethine nitrogen and thiolate sulfur atoms. Vitro antibacterial activity against gram-positive Staphylococcus aureus and gram-negative Escherichia coli, Klebsiella pneumonia strains and antioxidant activity have been evaluated. Also, the said complexes were tested for anticancer efficacy (in vitro for 48h) in Dalton's lymphoma (DL) cancer cell lines using cell cytotoxicity (MTT) and apoptosis tests. The results were compared with cisplatin (standard drug) under identical experimental conditions. The cell cytotoxicity results showed that complex 5 induced higher cytotoxicity in DL cells, followed by complex 4, 1, and 2.

Crystal Field Splitting Energy (Δo) and Racah Parameters (B) of Some Metal-Saccharine and Metal-Saccharine-Ethylenediamine Complexes

[M(sac)2(H2O)4].2H2O [sac = saccharinato anion, M = Fe(II), Co(II), Ni(II), and Cu(II)], and [M(sac)2(en)2].2H2O [sac = saccharinato anion, en = ethylenediamine, M = Fe(II), Co(II), Ni(II) and Cu(II)] were prepared in an aqueous medium. The compounds are crystalline of different colors and are ambiently stable. By examining their physico-chemical properties and relevant literature, the metal(II) ions in both [M(sac)2(H2O)4].2H2O and [M(sac)2(en)2].2H2O complexes are octahedrally coordinated. In the former by four neutral H2O molecules and two monoanionic sac ligands while in later, the octahedral sites fulfilled by two neutral bidentate ethylenediamine molecules and two monoanionic sac ligands. Splitting of the crystal field (Δo) and Racah parameter (B) of two sets of complexes [M(sac)2(H2O)4].2H2O and [M(sac)2(en)2].2H2O are estimated from their electronic spectra using Tanabe-Sugano diagram of Co(II) and Ni(II) complexes while Δo values of Fe(II) and Cu(II) derivatives are calculated directly from their absorption maxima. Our experimental results show that for the studied ligands and the divalent transition metal ions, the Δo values vary according to the following order: Cu(II) > Fe(II) > Co(II) > Ni(II). Dhaka Univ. J. Sci. 71(1): 6-12, 2023 (Jan)

New Fe(III) Trichlorido Complex of a Bidentate N'-(thiophen-2-ylmethylene)isonicotinohydrazide Ligand: Synthesis, X-ray Structure, Spectral Characterization, and Electrochemistry Study

Fe(III) complex of the hydrazone from (E)-N'-(thiophen-2-ylmethylene)isonicotinohydrazide (HL) has been synthesized and characterized by elemental analysis, electrical conductance in non-aqueous solvents, FT-IR and electronic spectroscopies, room temperature magnetic measurement, electrochemistry study as well as by X-ray diffraction structure determination. In the complex, the ligand acts in its neutral bidentate form, coordinating through the carbonyl oxygen and azomethine nitrogen. A high spin octahedral geometry assigned to the Fe(III) complex were further confirmed by room temperature magnetic moment data. Elemental analysis showed that Fe(III) complex is composed of metal and ligands in a molar ratio of 1:1. This complex of Fe(III) is a neutral electrolyte in DMF solution. The electrochemistry study shows that a one electron process determined the electrochemical reaction is governed by an electron transfer with an irreversible process. The structure of the complex has also been determined by X-ray diffraction revealing an octahedral environment around the Fe(III) ion.

Synthesis, Spectroscopic Characterization and Thermal Studies of Polymer-Metal Complexes Derived from Modified Poly Styrene-Alt-(Maleic Anhydride) as a Prospects for Biomedical Applications

Eight polymer-metal complexes were synthesized from complexation of divalent Mn(II), Ni(II), Co(II), and Cu(II) metal ions with modified polystyrene-alt-(maleic anhydride) (PSMAP and PSMAM) ligands. The structures of these new complexes were characterized using a variety of techniques, including magnetic moment susceptibility, conductance measurements, FT-IR spectroscopy, ultraviolet-visible (UV-VIS), thermogravimetric analysis (TGA), as well as scanning electron microscopy (SEM). All metal-polymer complexes have a non-electrolytic nature based on conductance measurements. The polymer molecule behaves as neutral bidentate NO ligand through O atoms of carbonyl (C=O) and N atoms of amide (O=C-NH). Divalent Mn2+, Ni2+, Co2+ and Cu2+ complexes have an octahedral geometry based on their electronic spectra and magnetic values. Based on thermal analysis data, those new complexes are more thermally stable than the ligands. SEM and TEM are manipulated to give the surface structure and the particle size measurements where they give different shapes and sizes of the synthesized complexes.

Biological Studies and Spectroscopic investigation of 4-Methyl Benzylimine Schiff Base Metal Complexes

Primary benzyl amines are highly important building blocks in the pharmaceutical and polymer industry. A new Schiff base ligand named (4-Methyl benzyl 2-Hydroxy 5-NitroAceto) imine was prepared through condensation reaction of 4-Methyl Benzyl amine and 2-hydroxy 5-Nitro Acetophenone in 1:2 molar ratios. The new ligand was characterized by spectral techniques. The coordination behaviour of a series of transition metal ions named Mn(II), Co(II), Zn(II) and Cd(II) with the newly prepared Schiff base ligand is reported. From IR spectra, it was observed that the ligand is a neutral bidentate ligand which coordinates to the metal ions through protonated phenolic oxygen, azomethine nitrogen and nitrogen atom of NH2 group. The molecular structures of the Schiff base ligand and its metal complexes were optimized theoretically. The synthesized ligand and its complexes were screened for antimicrobial activities against bacterial species. It was found that the compounds have shown activity against the organisms like Candida albicans, Bacillus subtilis and Salmonella typhi.