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AbstractA Schiff base (imine) ligand, (E)-4-((2-hydroxy-3,5-diiodobenzylidene)amino)-N-(4,6-dimethylpyrimidin-2-yl)benzenesulfonamide (HL), was synthesized by condensation of 3,5-diiodosalicylaldehyde with sulfamethazine. The ligand was then complexed with Zn(II), Cu(II), Ni(II), Co(II) and Fe(II) employing a metal to ligand ratio of 1:2 to form chelates (1-5), [M(L)2(H2O)2]. Characterization was done by UV-visible, FTIR, 1H and 13C NMR spectroscopy, elemental analysis, magnetic moments, thermogravimetric analyses (TGA) and conductance studies. The Schiff base behaved as a bidentate ligand and metal chelates assumed octahedral geometry. MOE-docking was employed to assess binding of the Schiff base (HL) and its chelates (1-5) with 1T2P, 1VVQ, 2W61, 3U2D, 4H8E and 5K18 proteins. Results indicated that Zn(II) chelate (1) and Fe(II) chelate (5) are the most potent compounds. Antibacterial and antibiofilm activities were executed against Enterococcus faecalis, Staphylococcus aureus, Proteus mirabilis and Klebsiella pneumoniae. Antifungal activities were performed against Candida albicans and Aspergillus niger. The Schiff base exhibited moderate antibacterial/antifungal activities that were enhanced on chelation with metal ions. Zinc(II) chelate (1) and Fe(II) chelate (5) show excellent antibacterial/antifungal activities. Complex 2 exhibited good antibiofilm activity. [ABSTRACT FROM AUTHOR]

Mononuclear copper(II) complex [Cu(DBDACH)2](ClO4)2 (1) was synthesized with a cyclohexane-1,2-diamine-based bidentate ligand, N,N'-dibenzyl 1,2-diaminocyclohexane (DBDACH) and characterized by various spectroscopic techniques. The structure of the complex was determined by single-crystal X-ray analysis and shows a distorted square planar geometry around the copper center. DNA binding interactions were interrogated by UV-Vis spectroscopic titration, circular dichroism, and docking studies. These studies confirmed that the copper complex binds with CT-DNA through minor groove interactions and showed a good binding constant of Kb = 2.15 × 104 M−1. The catecholase-like activity of 1 was investigated with model substrate 3,5-di-tert-butylcatechol (3,5-DTBC) to corresponding 3,5-di-tert-butylquinone (3,5-DTBQ) using UV-Vis spectroscopy. The rate of this reaction is 0.89 × 10−3 s−1. The kinetic characteristics of 1 were determined through the Michaelis–Menten equation and a Lineweaver-Burk analysis, yielding Vmax (3.4 × 10−3 M s−1), kM (0.49 × 10−3 M), and kcat (1.45 × 10−2 s−1). [ABSTRACT FROM AUTHOR]

The incidence of multi-resistant infections has sharply increased. One of the best strategies for developing new drugs is re-engineering existing drugs to enhance their bioavailability and antimicrobial activities. The latest systems focus on designing bioinorganic platforms to develop antimicrobial agents to target drug-resistant microbial strains. Various literature reports highlight metal-based antimicrobial agents unveiling an innovative strategy to tackle microbial agents. One of the significant mechanisms of antibiotic resistance in bacteria is the impermeability of its cell membrane towards antibiotics. Antibiotic-based Schiff base complexes are prime candidates for drug design with minor side effects in this scenario. The enhanced activity of antibiotic Schiff base complexes over their parent compound plays a key role in the emergence of innovative antimicrobials. In this review, we highlight the biological potential aspects of some selected antibiotic-based Schiff base complexes of penicillin, cephalosporins, quinolones, and sulfonamides. Some of the bacteria, especially P. aeruginosa, remain resistant to most of the commercially available antibiotics. Here, the review highlights that Schiff base complexes mediated by antibiotics demonstrate bactericidal activity against these resistant strains. Additionally, their mode of action on the bacterial cell is highlighted. The increased activity of copper, zinc, and silver complexes of different Schiff bases is attributed to their inherent redox chemistry. [ABSTRACT FROM AUTHOR]

Three new trinuclear complexes containing either nickel(II), copper(II) or zinc(II), [Ni3L2(NO3)2(CH3OH)2]·2CH3OH (1), [Cu3Br2L2] (2), [Zn3L2(NCS)2(CH3OH)2]·0.5CH3OH·0.5H2O (3), and a new dioxidomolybdenum(VI) complex, [MoO2L] (4), have been prepared from the bis-Schiff base N,N'-bis(4-bromosalicylidene)-1,3-propanediamine (H2L) with various metal salts in methanol. The complexes were characterized by elemental analysis, IR and UV–Vis spectra. Molecular structures were confirmed by single crystal X-ray diffraction experiments. The Ni ions in 1 adopt an octahedral coordination environment, bridged by phenolate oxygen and nitrate ligands. The Cu ions in 2 are square pyramidal and square planar, and the Zn ions in 3 are square pyramidal and octahedral. The metal atoms in 2 and 3 are bridged by phenolate oxygen donors. The Mo ion in 4 is octahedral. The Schiff base ligand coordinates to the metal atoms through two phenolate O and two imino N donors. Biological assays revealed that the nickel and copper complexes have effective urease inhibition. [ABSTRACT FROM AUTHOR]

In the present study the behavior of Cu(II) and Zn(II) complexes with ethylenediamine and 2,2′:6′,2′′ terpyridine in an aqueous environment was studied by classical MD simulations. Special attention was paid to the effect of Cu2+ for Zn2+ substitution on complex water surroundings and mobility. The replacement of a metal ion affects the structure of the complex water environment only in the vicinity of its location. However, it changes such a characteristic as the lifetime of a water molecule in the first coordination shell of a metal which can significantly affect the mobility of the complex. Moreover, the degree of influence on translational and rotational mobility can be different. [ABSTRACT FROM AUTHOR]

A new copper(II) complex with 2-amino-6-methylpyrimidin-4-(1H)-one, [Cu(C5H7N3O)4](NO3)2·H2O (Cupyrim), has been synthesized and studied by X-ray diffraction, elemental analysis and FT-IR spectroscopy. The Cu(II) is four-coordinate in a square planar geometry by four nitrogen atoms of the four organic ligands. Hirshfeld Surface Analysis was conducted to understand crystalline packing. Overall, the structure is maintained by metal coordination as well as strong and weak (C,N)–H···O hydrogen bonds and C–H...π interactions. The IR spectrum primary peaks have been assigned to the vibration modes of the ligand functional groups. An investigation of the inhibitory properties of Cupyrim toward "Cyclin-dependent Kinase 2" (CdK2) and "inducible nitric oxide synthase" (iNOS) proteins was aided by molecular docking research. According to molecular docking, Cupyrim exhibits promising inhibitory efficacy against Parkinson's, schizophrenia, and Alzheimer's disorders. The temperature dependence of the real and imaginary part of the dielectric permittivity was analyzed with the Cole-Cole formalism as well as DSC diagrams from 45-147 °C. [ABSTRACT FROM AUTHOR]

Two sulfoxide-containing Schiff bases, (E)-(((2-(methylsulfinyl phenyl) imino)methyl)-4-nitrophenol (HL1) and (E)-3,5-dibromo-2-(((2-(methylsulfinyl phenyl)imino)methyl)phenol (HL2), were prepared by condensation and subsequent oxidation reactions. In the presence of triethylamine, reactions of HL1 with 0.5 equivalent of copper acetate, cobalt acetate, nickel acetate and zinc acetate in ethanol afforded four metal complexes: (η2-N,O-L1)Cu(η3-O,N,O-L1) (1) and (η3-O,N,O-L1)2M (M = Co, 2; Ni, 3; Zn, 4), respectively. Similarly, treatment of HL2 with 0.5 equivalent of cobalt acetate and nickel acetate obtained two cobalt/nickel complexes: (η3-O,N,O-L2)2M (M = Co, 5; Ni, 6). Reactions of HL1 and one equivalent of Ru(PPh3)3Cl2 in tetrahydrofuran in the presence of triethylamine afforded a ruthenium(II) complex, (η3-O,N,S-L1)Ru(PPh3)2Cl (7). The molecular structures of HL1 and 1-7 have been confirmed by single-crystal X-ray diffraction. In addition, the UV–Vis, infrared, and fluorescence spectroscopies of 1–7 along with their electrochemical properties were also investigated. [ABSTRACT FROM AUTHOR]

In this investigation, six new metal complexes with 2-(pyridin-2-yl)benzo[d]imidazole (bpm) were synthesized and analyzed by single-crystal X-ray diffraction (XRD), including catena-bis[(µ-2,2-bis(4-carobxyphenyl)hexafluoropropane)-(2-(pyidin-2-yl)-1H-benzimidazole)-aqua-zinc] (1), catena-[(µ-2,2-bis(4-carobxyphenyl)hexafluoropropane)-(2-(pyidin-2-yl)-1H-benzimidazole)-aqua-cadmium] (2), aqua-[2,2-bis(4-carobxyphenyl)hexafluoropropane]-bis[2-(pyridin-2-yl)-1H-benzimidazole]-manganese (3), μ-[2-nitrobenzene-1,4-dicarboxylato]-μ-[2-nitrobenzene-1,4-dicarboxylato]-bis[2-(pyridin-2-yl)-1H-benzimidazole]-di-zinc (4), catena-[bis(µ-2-nitrobenzene-1,4-dicarboxylato)-diaqua-bis(2-(pyridin-2-yl)-1H-benzimidazole)-di-cadmium] (5), aqua-[pyridine-2,6-dicarboxylato]-[2-(pyridin-2-yl)-1H-benzimidazole]-copper hydrate (6) (H2hfipbb = 2,2-bis(4-carboxyphenyl)hexafluoropropane, H2nbdc acid = Nitroterephthalic acid, and H2pda = 2,6-pyridinedicarboxylic acid). Complex 1 crystallized in a monoclinic system with space group P21/n; 2 crystallized in a monoclinic system with space group C2/c; 3 crystallized in an orthorhombic system with space group Pna21; 5 crystallized in a monoclinic system with space group P21/c; 4 and 6 crystallized in triclinic systems with space group P-1. The DNA-binding modes of the complexes were investigated by several analysis methods (e.g. viscosity analysis, circular dichroism spectroscopy, fluorescent spectroscopic analysis, as well as UV spectroscopic analysis). Complexes 1-6 bind to calf thymus DNA via an intercalative mode. The results of this study provide insights into the mechanism of DNA binding and provide a basis for rationally designing new powerful reagents for DNA detection and targeting. [ABSTRACT FROM AUTHOR]

Centrosymmetric homopolynuclear Cu(II) and Co(II) chelated complexes, [Cu2(L)(H2O)2] (1) and [Co4(L)(μ-OAc)2(CH3OH)4(OAC)2]⋅2CH2Cl2 (2), were synthesized using a new symmetrical methoxy-disubstituted bis(salamo)-type ligand, H4L, with Cu(II) and Co(II) salts in organic solvents. Complexes 1 and 2 were structurally characterized by single-crystal X-ray crystallography. The results indicated that 1 is a five-coordinate dinuclear structure containing Cu(II) and 2 is a tetranuclear Co(II) complex with two distinct six-coordinate environments. Furthermore, 1 and 2 pack into three-dimensional and two-dimensional extended networks, respectively. The UV–Vis spectra, IR spectra, and Hirshfeld surface analyses of the complexes were carried out to further characterize the coordination between H4L and the metal(II) ions. Fluorescence methods were used to interrogate the coordination, where changes in emission with varied amounts of ligand supported solution-phase coordination ratios of H4L with Cu(II) ion of 1:2 and with Co(II) ion of 1:4, respectively. [ABSTRACT FROM AUTHOR]

The reactions of copper chloride and 4′-(4′-substituted-phenyl)-2,2′:6′,2′′-terpyridine ligands bearing nitro (L1), methyl (L2), phenyl (L3), tolyl (L4) and carboxyl (L5) gave five copper compounds (1–5) which have mononuclear structures with their Cu(II) ions five-coordinate in the irregular square pyramidal geometries. Their in vitro biological properties were evaluated by CCK-8 assay, which show remarkable proliferation inhibitive properties on the cancer cell lines including A549, Eca-109, and Bel-7402, and two human normal cell lines (HL-7702 and HLF). The values of IC50 indicate better anticancer activities of these compounds than that of cisplatin. Compound 2 with methyl group exhibits the best anticancer activity, with IC50 value < 2.5 µM on all the tested cancer cells. The interactions of the compounds with DNA were evaluated using UV–Vis absorption titrations, circular dichroism spectroscopy, and DNA viscosity. The complexes show significant insertion binding with DNA sequences and strong intercalator binding mode with DNA sequences. Compounds 1–5 interact with the functional groups of DNA through π···π stacking, van der Waals interactions, hydrophobic interactions, and hydrogen bonds as determined by molecular docking. In addition, strong binding interactions between the five copper(II) complexes and bovine serum albumin (BSA) were studied by fluorescence titration and circular dichroism spectroscopy. [ABSTRACT FROM AUTHOR]

Template condensation between pentane-1,5-dial and triethylenetetramine in the presence of divalent metal salts in methanolic solution resulted in mononuclear 15-membered tetraazamacrocyclic Schiff base metal complexes, [M(C11H22N4)X2], where M = Co(II), Ni(II) and Cu(II), X = Cl− and C11H22N4 is the tetradentate macrocyclic ligand. The bonding and overall geometry of the complexes are inferred through elemental analysis, FT-IR, UV–vis, 1H/13C NMR, ESI-mass, molar conductance, magnetic susceptibility and TG measurements. On the basis of the absorption bands in UV–vis spectra and magnetic moment analyses, a six-coordinate octahedral geometry is proposed for all the metal complexes. The formulation of the metal chelates is compatible with the thermal decomposition profiles. Photocatalytic efficiency of the macrocyclic Ni(II) complex was studied using solar water-splitting. The in vitro antimicrobial activity of metal complexes has been tested against certain bacterial and fungal species. The scavenging ability of DPPH free radicals was used to test the antioxidant activity of the complexes. In addition, MTT assay was used to assess the cytotoxicity of Cu(II) chloro complex against L929 mouse fibroblast cell lines. [ABSTRACT FROM AUTHOR]

Two new one-dimensional (1-D) end-to-end azido and thiocyanato bridged Cu(II) coordination polymers, [Cu(L)(µ-1,3-N3)]n(ClO4)n (1) and [Cu(L)(µ-1,3-NCS)]n(ClO4)n (2) with a morpholine-based tridentate N,N,N-donor Schiff base ligand (1-methyl-1H-imidazol-2-yl)-N-[2-(morpholin-4-yl)ethyl]methanimine, L) have been synthesized. Compounds 1 and 2 have been characterized by elemental analyses and spectroscopic techniques. The X-ray single crystal structures of 1 and 2 show the formation of regular zigzag chains with µ-1,3-azido and µ-1,3-thiocyanate bridges, respectively. Variable temperature (2–300 K) magnetic studies indicate that 1 shows a ferromagnetic intrachain exchange interaction with g = 2.135(2) and J = 2.13(2) cm−1, while in 2 this interaction is antiferromagnetic with g = 2.1412(3) and J = –0.277(2) cm−1. X-band EPR spectra of 1 and 2 in frozen (143 K) DMF solution corroborate our magnetic studies. [ABSTRACT FROM AUTHOR]

Three new copper(II) 5,5-diethylbarbiturate (barb) complexes of nicotinamide (nia), 2,2′-bipyridine (bpy) and triethanolamine (tea), trans-[Cu(barb)2(nia)2]⋅2H2O (1), cis-[Cu(barb)2(bpy)]⋅3H2O (2) and [Cu2(barb)2(tea)2]⋅2H2O (3), were synthesized and characterized by elemental analysis, spectroscopic (UV-Vis and FTIR) and magnetic moment measurements. Single crystal X-ray crystallographic measurements showed that 1 and 2 are mononuclear, while 3 is binuclear, in which two copper centers were bridged by deprotonated ethanol groups of two tea ligands. The barb ligand in these complexes is a bidentate N, O-donor. Thermal analysis (TG/DTA) studies in air indicated that the complexes first dehydrated and then the decomposition of nia, bpy or tea ligands occurred. The last exothermic stage was associated with degradation of the barb moiety to yield CuO as the end product. [ABSTRACT FROM AUTHOR]

By single-crystal X-ray diffraction (XRD) analysis, five complexes, catena-[(µ-2,2-bis(4-carboxyphenyl)hexafluoropropane)-(2-(pyidin-2-yl)-1,3-benzothiazole)-aqua-zinc(II)] (1), catena-[(µ-2,2-bis(4-carboxyphenyl)hexafluoropropane)-(2-(pyidin-2-yl)1,3-benzothiazole)-aqua-cadmium(II)] (2), catena-[hepta(µ-2,2-bis(4carboxyphenyl)hexafluoropropane)-diaqua-bis(2-(pyidin-2-yl)-1,3-benzothiazole)-tri-manganes(II)] (3), catena-[(µ-benzene-1,2,4,5-tetracarboxylato)-(2-(pyidin-2-yl)-1,3benzothiazole)copper(II)] (4) and catena-[(µ-3-nitrobenzene-1,2-dicarboxylato)-(2-(pyidin-2-yl)1,3-benzothiazole)-aqua-zinc(II)] (5), were characterized in this research. In these five complexes, H2hfipbb = 2,2-bis(4-carboxyphenyl)hexafluoropropane, H4btec = 1,2,4,5-benzenetetracarboxylic acid, H2NPTA = 3-nitrophthalic acid and bpt = 2-(pyridin-2-yl)benzo[d]thiazole). Complexes 1 and 2 occur in the monoclinic system with space group C2/c, 4 and 5 occur in the monoclinic system with space group P21/c, and 3 occurs in the triclinic system with space group P-1. The interaction between CT-DNA (calf thymus DNA) and those complexes was examined using UV spectroscopic analysis, fluorescent spectroscopic analysis, circular dichroism spectroscopy (CD) and viscosity analysis. This research reveals that those complexes have strong ability to interact with DNA, and they all bind to DNA in an intercalation mode, thus affecting the structure of DNA. This binding mode can arise from the interaction between the benzothiazole metal complexes and DNA. Hence, we hope to provide some scientific research bases for studying benzothiazole complexes and designing new thiazole anticancer drugs. [ABSTRACT FROM AUTHOR]

A centipede like thiocyanate-bridged multi-nuclear copper(I/II) complex, [Cu2L(CH3OH)(NCS)3]n, derived from 2-(((2-(dimethylamino)ethyl)imino)methyl)-5-fluorophenol (HL), was prepared and characterized by elemental analysis, IR and UV–vis spectra, as well as single crystal X-ray diffraction. The Cu1 ion in the +2 oxidation state is coordinated by the tridentate Schiff base ligand in a square pyramidal geometry, with the other two sites occupied by one N atom of the thiocyanate ligand and one methanol O atom. The Cu2 ion in the +1 oxidation state is coordinated by one N and three S atoms from four thiocyanate ligands, forming a tetrahedral geometry. The CuI ions are linked by thiocyanate ligands to form a one-dimensional chain with [CuI2(μ1,3,3-NCS)2] as the repeat unit. The [CuIIL(CH3OH)] moieties are linked to the chain through thiocyanate ligands. The complex has remarkable inhibitory activity on Jack bean urease with an IC50 value of 1.3 μmol L–1. [ABSTRACT FROM AUTHOR]