Synthesis and characterization of the first zinc(II) complexes involving kinetin and its derivatives: X-ray structures of 2-chloro-N6-furfuryl-9-isopropyladenine and [Zn(kinetin)2Cl2]·CH3OH

A series of the first zinc(II) complexes of the general composition [Zn(Lⁿ)₂Cl₂]·xSolv (1-5) involving kinetin [N6-furfuryladenine, L¹, xSolv = CH₃OH, complex 1] and its derivatives, i.e. N6-(5-methylfurfuryl)adenine (L², xSolv = 2H₂O, 2), 2-chloro-N6-furfuryladenine (L³, 3), 2-chloro-N6-(5-methylfurfuryl)adenine (L⁴, 4) and 2-chloro-N6-furfuryl-9-isopropyladenine (L⁵, 5), as N-donor ligands has been synthesized. The complexes have been fully characterized by elemental analyses (C, H, N), FTIR, Raman, ¹H and ¹³C NMR spectroscopy, conductivity measurements, thermogravimetric (TG) and differential thermal (DTA) analyses. Single crystal X-ray analysis determined the molecular structures of 2-chloro-N6-furfuryl-9-isopropyladenine (L⁵) and the complex [Zn(L¹)₂Cl₂]·CH₃OH. The Zn(II) ion is tetrahedrally coordinated by two chlorido ligands and two molecules of the L¹ organic compound. The two ligands L¹ are coordinated to the central Zn(II) ion via the N7 atoms. This conclusion can also be drawn from multinuclear NMR spectroscopic experiments.     

Synthesis and characterisation of palladium(II) and platinum(II) compounds containing pyrazole-derived ligands: crystal structure of [PdCl2(HL)] (HL = 3-phenyl-5-(2-pyridyl)pyrazole)

Reaction of the ligands 3-phenyl-5-(2-pyridyl)pyrazole (HL¹), 3,5-bis(2-pyridyl)pyrazole (HL²), 3-methyl-5-(2-pyridyl)pyrazole (HL³) and 3-methyl-5-phenylpyrazole (HL⁴) with [MCl₂(CH₃CN)₂] (M = Pd(II), Pt(II)) or [PdCl₂(cod)] gives complexes with stoichiometry [PdCl₂(HL)₂] (HL = HL¹, HL², HL³), [Pt(L)₂] (L = L¹, L², L³) and [MCl₂(HL⁴)₂] (M = Pd(II), Pt(II)). The new complexes were characterised by elemental analyses, conductivity measurements, infrared and ¹H NMR spectroscopies. The crystal and molecular structure of [PdCl₂(HL¹)] was resolved by X-ray diffraction, and consists of monomeric cis-[PdCl₂(HL¹)] molecules. The palladium centre has a typical square planar geometry, with a slight tetrahedral distortion. The tetra-coordinated metal atom is bonded to one pyridine nitrogen, one pyrazolic nitrogen and two chloro ligands in a cis disposition. The ligand HL¹ is not completely planar.     

Synthesis and crystal structure of a salicylatooxovanadium(V) complex of an aminebis(phenolate) ligand: Kinetic studies on its formation from corresponding alkoxo complexes

Synthesis and single crystal X-ray structures of H₂L¹ and VO(L¹)(HL) [H₂L¹ = N,N-bis(2-hydroxy-3,5-ditertiarybutyl)-N′,N′-dimethylethylendiamine) or simply aminebis(phenol) and H₂L = salicylic acid) are reported here. The complex [VO(L¹)(HL)] is in distorted octahedral geometry under O₄N₂ donor environment where the basal core is defined by O(1), O(3), O(2) and N(5) atoms and two axial coordinates are occupied by O(4), an alkoxo-group and N(1), an imino-nitrogen atom. The electron spray mass spectrometric study on [VO(L¹)(HL)] in MeCN clearly points out the existence of single species in solution. Again, the ⁵¹V NMR of the bulk polycrystalline sample reveals that the complex [VO(L¹)(HL)] mainly exists in three out of four possible isomers. The formation of [VO(L¹)(HL)] from both [VO(L¹)(OMe)] and [VO(L¹)(OEt)] was followed kinetically by reacting with salicylic acid in MeCN. The presence of isosbestic point indicates a clean conversion of the reactants to product.     

Mononuclear iron(III) complexes supported by tripodal N3O ligands: Synthesis, structure and reactivity towards DNA cleavage

A new synthetic route to the known tripodal tetradentate N₃O ligand L¹ (HL¹ = [N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-di-(2-pyridylmethyl)]amine) is reported. The related compounds HLⁿ (n = 2, 3) were prepared by a similar procedure. Treatment of HLⁿ (n = 1-3) with FeCl₃·6H₂O in hot methanol led to the mononuclear iron(III) complexes [Fe(Lⁿ)Cl₂] (1: n = 1, 2: n = 2, 3: n = 3). The solid-state structures of complexes 1 and 2 were determined by X-ray crystallography. [Fe(L¹)Cl₂] (1) showed effective nuclease activity in the presence of hydrogen peroxide, converting supercoiled plasmid DNA to its linear form.     

Synthesis, structure, and properties of monomeric Fe(II), Co(II), and Ni(II) complexes of neutral N-(aryl)-2-pyridinecarboxamides

We have prepared and structurally characterized six-coordinate Fe(II), Co(II), and Ni(II) complexes of types [M^II(HL¹)₂(H₂O)₂][ClO₄]₂ (M = Fe, 1; Co, 3; and Ni, 5) and [M^II(HL²)₃][ClO₄]₂ · MeCN (M = Fe, 2 and Co, 4) of bidentate pyridine amide ligands, N-(phenyl)-2-pyridinecarboxamide (HL¹) and N-(4-methylphenyl)-2-pyridinecarboxamide (HL²). The metal centers in bis(ligand)-diaqua complexes 1, 3 and 5 are coordinated by two pyridyl N and two amide O atoms from two HL¹ ligands and six-coordination is completed by coordination of two water molecules. The complexes are isomorphous and possess trans-octahedral geometry. The metal centers in isomorphous tris(ligand) complexes 2 and 4 are coordinated by three pyridyl N and three amide O atoms from three HL² ligands. The relative dispositions of the pyridine N and amide O atoms reveal that the pseudo-octahedral geometry have the meridional stereochemistry. To the best of our knowledge, this work provides the first examples of structurally characterized six-coordinate iron(II) complexes in which the coordination is solely by neutral pyridine amide ligands providing pyridine N and amide O donor atoms, with or without water coordination. Careful analyses of structural parameters of 1-5 along with that reported in the literature [M^II(HL¹)₂(H₂O)₂][ClO₄]₂ (M = Cu and Zn) and [Co^III(L²)₃] have allowed us to arrive at a number of structural correlations/generalizations. The complexes are uniformly high-spin. Spectroscopic (IR and UV/Vis) and redox properties of the complexes have also been investigated.     

Dinuclear copper(II) complexes containing 6-(benzylamino)purines as bridging ligands: Synthesis, characterization, and in vitro and in vivo antioxidant activities

A series of dinuclear copper(II) complexes involving 6-(benzylamino)purine derivatives, (HL_n), as bridging ligands were synthesized, characterized and tested for both their in vitro and in vivo antioxidant activities. Based on results of elemental analyses, temperature dependence of magnetic susceptibility measurements, UV-vis, FTIR, EPR, NMR and MALDI-TOF mass spectroscopy, conductivity measurements and thermal analyses, the complexes with general compositions of [Cu₂(μ-HL_n)₄Cl₂]Cl₂ · 2H₂O (1-4) and [Cu₂(μ-HL_n)₂(μ-Cl)₂Cl₂] (5-7) were prepared {where n = 1-4; HL₁ = 6-[(2-methoxybenzyl)amino]purine, HL₂ = 6-[(4-methoxybenzyl)amino]purine, HL₃ = 6-[(2,3-dimethoxybenzyl)amino]purine and HL₄ = 6-[(3,4-dimethoxybenzyl)amino]purine}. In the case of complexes 2, 3, 5 and 7, the antioxidant activities were studied by both in vitro {superoxide dismutase-mimic (SOD-mimic) activity} and in vivo {cytoprotective effect against the alloxan-induced diabetes (antidiabetic activity)} methods. The obtained IC₅₀ value of the SOD-mimic activity for the complex 5 (IC₅₀ = 0.253 μM) was shown to be even better than that of the native bovine Cu,Zn-SOD enzyme (IC₅₀ = 0.480 μM), used as a standard. As for the antidiabetic activity, the pretreatment of mice with complexes 3 and 7 led to the complete elimination of cytotoxic attack of alloxan and its free radical metabolites, used as a diabetogenic agent. The cytoprotective effect of these compounds was proved by the preservation of the initial blood glucose levels of the pretreated animals, as against the untreated control group.     

Structure, magnetic properties and nuclease activity of pyridine-2-carbaldehyde thiosemicarbazonecopper(II) complexes

New complexes of formulae [Cu(HL²)(H₂O)(NO₃)](NO₃) (1), [{Cu(L¹)(tfa)}₂] (2), [{Cu(L¹)}₂(pz)](ClO₄)₂ (3) and {[{Cu(L¹)}₂(dca)](ClO₄)}_n (4), where HL¹ = pyridine-2-carbaldehyde thiosemicarbazone, HL² = pyridine-2-carbaldehyde 4N-methylthiosemicarbazone, Htfa = trifluoroacetic acid (CF₃COOH), pz = pyrazine (C₄H₄N₂) and dca = dicyanamide [N(CN)₂]⁻, have been synthesized and characterized. The crystal structures of these compounds are built up of monomers (1), dinuclear entities with the metal centers bridged through the non-thiosemicarbazone coligand (2 and 3) and 1D chains of dimers (4). In all the cases, square-pyramidal copper(II) ions are present, except for the square-planar ones in 3. Magnetic measurements show antiferromagnetic couplings in 2, 3 and 4. The susceptibility data were fitted by the Bleaney-Bowers’ equation for copper(II) dimers derived from H = -2JS₁S₂ being the obtained J/k values −4.8, −4.3 and −5.1 K for compounds 2-4, respectively. The magnetic susceptibility of the already known [{Cu(HL¹)(tfa)}₂](tfa)₂ compound has been also measured for the first time. The J/k value is -0.3 K, lower than that in 2. The nuclease activity of 3 and 4 has been analyzed.     

The first iron(III) complexes with cyclin-dependent kinase inhibitors: Magnetic, spectroscopic (IR, ES+ MS, NMR, Fe Mössbauer), theoretical, and biological activity studies

The first Fe^III complexes 1-6 with cyclin-dependent kinase (CDK) inhibitors of the type [Fe(L_n)Cl₃]·nH₂O (n = 0 for 1, 1 for 2, 2 for 3-6; L₁-L₆ = C2- and phenyl-substituted CDK inhibitors derived from 6-benzylamino-9-isopropylpurine), have been synthesized and characterized by elemental analysis, IR, ⁵⁷Fe Mössbauer, ¹H and ¹³C NMR, and ES+ mass spectroscopies, conductivity and magnetic susceptibility measurements, and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The study revealed that the compounds are mononuclear, tetrahedral high-spin (S = 5/2) Fe^III complexes with an admixture of an S = 3/2 spin state originating probably from five-coordinated Fe^III ions either connecting with a bidentate coordination mode of the CDK inhibitor ligand or relating to the possibility that one crystal water molecule enters the coordination sphere of the central atom in a portion of molecules of the appropriate complex. Nearly spin-only value of the effective magnetic moment (5.82 μ_eff/μ_B) was determined for compound 1 due to absence of crystal water molecule(s) in the structure of the complex. Based on NMR data and DFT calculations, we assume that the appropriate organic ligand is coordinated to the Fe^III ion through the N7 atom of a purine moiety. The cytotoxicity of the complexes was tested in vitro against selected human cancer cell lines (G-361, HOS, K-562 and MCF-7) along with the ability to inhibit the CDK2/cyclinE kinase. The best cytotoxicity (IC₅₀: 4-23 μM) and inhibition activity (IC₅₀: 0.02-0.09 μM) results have been achieved in the case of complexes 2-4, and complexes 3, 4 and 6, respectively. In addition, the X-ray structure of 2-chloro-6-benzylamino-9-isopropylpurine, i.e. a precursor for the preparation of L₁, L₄ and L₅, is also described.     

Functional model for intradiol-cleaving catechol 1,2-dioxygenase: Synthesis, structure, spectra, and catalytic activity of iron(III) complexes with substituted salicylaldimine ligands

A series of mononuclear iron(III) complexes with containing phenolate donor of substituted-salicylaldimine based ligands [Fe(L¹)(TCC)] · CH₃OH (1), [Fe(L²)(TCC)] · CH₃OH (2), [Fe(L³)(TCC)] (3), and [Fe(L⁴)(TCC)] (4) have been prepared and studied as functional models for catechol dioxygenases (H₂TCC = tetrachlorocatechol, or HL¹ = N′-(salicylaldimine)-N,N-diethyldiethylenetriamine, HL² = N′-(5-Br-salicylaldimine)-N,N-diethyldiethylenetriamine, HL³ = N′-(4,6-dimethoxy-salycyl-aldimine)-N,N-diethyl-diethylenetriamine, HL⁴ = N′-(4-methoxy-salicylaldimine)-N,N-diethyl-diethylenetriamine). They are structural models for inhibitors of enzyme-substrate adducts from the reactions of catechol 1,2-dioxygenases. Complexes 1-4 were characterized by spectroscopic methods and X-ray crystal structural analysis. The coordination sphere of Fe(III) atom of 1-4 is distorted octahedral with N₃O₃ donor set from the ligand and the substrate TCC occupying cis position, and Fe(III) is in high-spin (S = 5/2) electronic ground state. The in situ prepared iron(III) complexes without TCC, [Fe(L¹)Cl₂], [Fe(L²)Cl₂], [Fe(L³)Cl₂], and [Fe(L⁴)Cl₂] are reactive towards intradiol cleavage of the 3,5-di-tert-butylcatechol (H₂DBC) in the presence of O₂ or air. The reaction rate of catechol 1,2-dioxygenase depends on the redox potential and acidity of iron(III) ions in complexes as well as the substituent effect of the ligands. We have identified the reaction products and proposed the mechanism of the reactions of these iron(III) complexes with H₂DBC with O₂.     

Substituted pyridylmethylamide ligands and their zinc complexes

Mononuclear zinc complexes of a family of pyridylmethylamide ligands abbreviated as HL, HL^Ph, HL^Me3, HL^Ph3, and MeL^SMe [HL = N-(2-pyridylmethyl)acetamide; HL^Ph = 2-phenyl-N-(2-pyridylmethyl)acetamide; HL^Me3 = 2,2-dimethyl-N-(2-pyridylmethyl)propionamide; HL^Ph3 = 2,2,2-triphenyl-N-(2-pyridylmethyl)acetamide; MeL^SMe = N-methyl-2-methylsulfanyl-N-pyridin-2-ylmethyl-acetamide] were synthesized and characterized spectroscopically and by single crystal X-ray structural analysis. The reaction of zinc(II) salts with the HL ligands yielded complexes [Zn(HL)₂(OTf)₂] (1), [Zn(HL)₂(H₂O)](ClO₄)₂ (2), [Zn(HL^Ph3)₂(H₂O)](ClO₄)₂ (3), [Zn(HL^Ph)Cl₂] (4), [Zn(HL^Me3)Cl₂] (5), and [Zn(MeL^SMe)Cl₂] (6). The complexes are either four-, five- or six-coordinate, encompassing a variety of geometries including tetrahedral, square-pyramidal, trigonal-bipyramidal, and octahedral.     

Two new end-to-end single dicyanamide bridged Cu(II) complexes with Schiff base ligands: Structural, electrochemical and magnetic properties

The synthesis, crystal structures and magnetic properties of two different copper(II) complexes of formula [Cu(L¹)(dca)]_n · nClO₄ (1) and [Cu(L²)]₂(dca)(ClO₄) (2) [L¹ = N,N-dimethylethylene-N′-(pyridine-2-carbaldiiminato), HL² = N,N-dimethylethylene-N′-salicylaldiiminato, dca = dicyanamide anion] are described. Spectroscopic and electrochemical properties have also been discussed. A one-dimensional chain structure with single, symmetrical, μ_1,5-dca bridges is found in compound 1. The copper atom in 1 has a square pyramidal geometry. A tridentate Schiff base ligand, having NNN donor sites, and one nitrogen atom from dca occupy the basal plane. N(18) of a neighbouring unit occupies the apical site. The Schiff base used in compound 2 is a tridentate anion with NNO donor sites, which changes the structure in a dinuclear unit of copper atoms bridged by single end-to-end dicyanamide ion. The environment around copper in 2 is square planar. Magnetic susceptibility measurements for 1 and 2 reveal the occurrence of weak antiferromagnetic interaction through the dca ligand.     

Rhenium(III) and technetium(III) complexes with 2-mercapto-1,3-azole ligands and X-ray crystal structures

Reactions of labile [MCl₃(PPh₃)₂(NCMe)] (M = Tc, Re) precursors with 1H-benzoimidazole-2-thiol (H₂L¹), 5-methyl-1H-benzoimidazole-2-thiol (H₂L²) and 1H-imidazole-2-thiol (H₂L³), in the presence of PPh₃ and [AsPh₄]Cl gave a new series of trigonal bipyramidal M(III) complexes [AsPh₄]{[M(PPh₃)Cl(H₂L^1-3)₃]Cl₃} (M = Re, 1-3; M = Tc, 4-6). The molecular structures of 1 and 3 were determined by X-ray diffraction. When the reactions were carried out with benzothiazole-2-thiol (HL⁴) and benzoxazole-2-thiol (HL⁵), neutral paramagnetic monosubstituted M(III) complexes [M(PPh₃)₂Cl₂(L^4,5)] (M = Re, 8, 9; M = Tc, 10, 11) were obtained. In these compounds, the central metal ions adopt an octahedral coordination geometry as authenticated by single crystal X-ray diffraction analysis of 8 and 11. Rhenium and technetium complexes 1, 4 and rhenium chelate compounds 8, 9 have been also synthesized by reduction of [MO₄]⁻ with PPh₃ and HCl in the presence of the appropriate ligand. All the complexes were characterized by elemental analyses, FTIR and NMR spectroscopy.     

One-pot syntheses of alkenyl-phosphonio complexes of ruthenium(II), rhodium(III) and iridium(III) bearing p-cymene or pentamethylcyclopentadienyl groups

Reaction of [(p-cymene)RuCl₂(PPh₃)] (1) or [Cp^∗MCl₂(PPh₃)] (Cp^∗ = C₅Me₅) (3a: M = Rh; 4a: M = Ir) with 1-alkynes and PPh₃ were carried out in the presence of KPF₆, generating the corresponding alkenyl-phosphonio complexes, [(p-cymene)RuCl(PPh₃){CHCR(PPh₃)}](PF₆) (2a: R = Ph; 2b: R = p-tolyl) or [Cp^∗MCl(PPh₃){CHCPh(PPh₃)}](PF₆) (5: M = Rh; 6: M = Ir). Similar reactions of complexes [Cp^∗RhCl₂(L¹)] (3a: L¹ = PPh₃; 3c: L¹ = P(OMe)₃) with L² (L² = PPh₃, PMePh₂, P(OMe)₃) gave [Cp^∗RhCl(L¹)(L²)](PF₆) (7bb: L¹ = L² = PMePh₂; 7ca: L¹ = P(OMe)₃, L² = PPh₃; 7cc: L¹ = L² = P(OMe)₃). Alkenyl-phosphonio complex 5 was treated with P(OMe)₃ or 2,6-xylyl isocyanide, affording [Cp^∗RhCl(L){CHCPh(PPh₃)}](PF₆) (8a: L = P(OMe)₃; 8b: L = 2,6-xylNC). X-ray structural analyses of 2a, 6 and 8a revealed that the phosphonium moiety bonded to the C_β atom of the alkenyl group are E configuration.     

Functional model for catecholase-like activity: Synthesis, structure, spectra, and catalytic activity of iron(III) complexes with substituted-salicylaldimine ligands

Four new mononuclear iron(III) complexes with the substituted-salicylaldimine ligands, [Fe(L¹)(TCC)] (1), [Fe(L²)(TBC)] (2), [Fe(L³)(TBC)] (3) and [Fe(L⁴)(TCC)](CH₃CN) (4) (HL¹ = N′-(5-OH-salicylaldimine)-diethylenetriamine, HL² = (N′-(5-Cl-salicylaldimine)-diethylenetriamine, HL³ N′-(5-Br-salicyl-aldimine)-dipropylenetriamine, HL⁴ = (N′-3,5-Br-salicylaldimine)-dipropylenetriamine, H₂TCC = tetrachlorocatechol, and H₂TBC = tetrabromocatechol), were prepared and characterized by XRD, EPR, and Mössbauer spectroscopy. The coordination sphere of the Fe(III) in complexes 1-4 is a distorted octahedral with N₃O₃ donors set which constructed by the Schiff-base ligands and the catecholate substrates of TBC or TCC. The in situ prepared Fe(III) complexes [Fe(L¹)Cl₂], [Fe(L²)Cl₂], [Fe(L³)(Cl₂)], and [Fe(L⁴)Cl₂] in absence of TBC or TCC show a high catecholase-like activity for the oxidation of 3,5-DTBC to the corresponding quinone 3,5-DTBQ.     

First microwave-assisted synthesis of an electron-rich phosphane and its coordination chemistry with platinum(II) and palladium(II)

The P-O ligand 3-(di(2-methoxyphenyl)phosphanyl)propionic acid (HL) was synthesized by a microwave-assisted reaction of a secondary phosphane. The coordination of HL to Pt^II yielded the neutral mononuclear complex trans-[PtCl(κ²-P,O-L)(κ-P-HL)] (1), while the reaction of PdClMe(η⁴-COD) (COD = 1,4-cyclooctadiene) with HL in the presence of NEt₃ gave the anionic Pd^II compound of the formula (HNEt₃)[PdClMe(κ²-P,O-L)] (2). Upon crystallization of the latter compound the neutral chloride-bridged dimetallic compound cis-[Pd(μ-Cl)Me(HL)]₂ (3) was obtained. HL, 1 and 3·CH₂Cl₂ have been characterized by single crystal X-ray structure analyses.     

Transition metal complexes (M = Cu, Ni and Mn) of Schiff-base ligands: Syntheses, crystal structures, and inhibitory bioactivities against urease and xanthine oxidase

Six new transition metal complexes (M = Cu(II), Ni(II) and Mn(III)) of tridentate (H₂L¹, HL²) and/or bidentate (HL³, HL⁴) Schiff-base ligands, obtained from the condensation of salicylaldehyde with glycine, N-(2-aminoethyl)morpholine, 4-(2-aminoethyl)phenylic acid and 4-(2-aminoethyl)benzsulfamide, respectively, were synthesized and structurally determined by single-crystal X-ray analysis. Complexes 1-6 were evaluated for their effect on the jack bean urease and xanthine oxidase (XO). Copper(II) complexes 1-3 (IC₅₀ = 0.43-2.25 μM) showed potent inhibitory activity against jack bean urease, comparable with acetohydroxamicacid (IC₅₀ = 42.12 μM), which is a positive reference. And these copper(II) complexes (IC₅₀ = 10.26-15.82 μM) also exhibited strong ability to inhibit activity of XO, comparable to allopurinol (IC₅₀ = 10.37 μM), which was used as a positive reference. Nickel(II) and manganese(III) complexes 4-6 showed weak inhibitory activity to jack bean urease (IC₅₀ = 4.36-8.25 μM) and no ability to inhibit XO (IC₅₀ > 100 μM).     

Synthesis, crystal structures and characterization of three novel complexes with N-[2-(2-hydroxybenzylideneamino)ethyl]-4-methyl-benzene-sulfonamide as ligand

Reaction of the N-tosyl-ethylenediamine and salicylaldehyde forms a new sulfonamide Schiff base N-[2-(2-hydroxybenzylideneamino)ethyl]-4-methyl-benzene-sulfonamide (H₂L). Three novel complexes constructed from H₂L, namely, [M(HL)₂] · xH₂O (M = Cu, x = 0 for 1, M = Ni, x = 0 for 2 and M = Zn, x = 1 for 3) have been prepared and characterized via X-ray single-crystal diffraction, elemental analysis, X-ray powder diffraction (XRPD), FT-IR, UV-Vis, TGA and photoluminescence measurements. Complex hydrogen bonds, C-H···π and π-π stacking interactions lead 1-3 to present 1-D, 2-D and 3-D supramolecular architectures, respectively.     

Synthesis, structures and magnetic properties of 1D to 3D coordinated polymers based on series of flexible sulfide ligands

Five complexes [Mn₂O(L₁)₄]_n (1), [Co(L₂)(H₂O)₂]_n (2), [Co(L₃)₂(H₂O)₂]_n (3) and [Co(L₄)₂(4,4′-bpy)(H₂O)]_n (4) were obtained by using flexible organic ligands HL₁, HL₂, HL₃, and HL₄ in hydrothermal systems with cobalt, copper and manganese salts respectively (HL₁ = 2-(4-pyridylmethylthio)benzoic acid, HL₂ = 4-(4-pyridylmethylthio)benzoic acid, HL₃ = 2-(3-pyridylmethylthio)benzoic acid, HL₄ = 4-(2-pyridylmethylthio)benzoic acid). The five complexes have been characterized by X-ray single crystal diffraction, FT-IR spectrum and elemental analysis. Complex 1 is assembled to a 3D porous framework with Mn₂O units as nodes. Complex 2 shows 2D layer networks comprised of six-coordinated Co²⁺ centers and L₂⁻ anionic ions. Complexes 3 and 4 have different 1D double or single chain structures. Various non-covalent bonds such as hydrogen bonds, π?π interactions, H-bond grids and S?S weak interactions lead to interesting supramolecular frameworks. DC (direct current) temperature dependent magnetic susceptibilities suggest weak antiferromagnetic behaviors exist in 1, and single ion paramagnetic along with spin-orbit coupling behavior dominate in 3 and 4.     

Molecular interactions of zinc(II) cyclams with polycarboxylato ligands

Four new zinc(II) cyclams of the composition {Zn(L)(tp²⁻) · H₂O}_n (1), {Zn(L)(H₂bta²⁻) · 2H₂O}_n (2), [Zn₂(L)₂(ox²⁻)] 2ClO₄ · 2DMF (3), and Zn(L)(H₂btc⁻)₂ · 2DMF (4), where L = cyclam, tp²⁻ = 1,4-benzenedicarboxylate ion, H₂bta²⁻ = 1,2,4,5-benzenetetracarboxylate ion, ox²⁻ = oxalate ion, DMF = N,N-dimethylformamide, and H₂btc⁻ = 1,3,5-benzenetricarboxylate ion, have been synthesized and structurally characterized by a combination of analytical, spectroscopic and crystallographic methods. The carboxylato ligands in the complexes 1-4 show strong coordination tendencies toward zinc(II) cyclams with hydrogen bonding interactions between the pre-organized N-H groups of the macrocycle and oxygen atoms of the carboxylato ligands. The macrocycles in 1, 2, and 4 adopt trans-III configurations with the appropriate R,R,S,S arrangement of the four chiral nitrogen centers, respectively. However, the complex 3 shows an unusual cis V conformation with the R,R,R,R nitrogen configuration. The finding of strong interactions between the carboxylato ligands and the zinc(II) ions may provide additional knowledge for the improved design of receptor-targeted zinc(II) cyclams in anti-HIV agents.     

Diorganotin(IV) complexes of dipeptides containing the alpha-aminoisobutyryl residue (Aib): preparation, structural characterization, antibacterial and antiproliferative activities of [(n-Bu)2 Sn(H(-1)L)] (LH=H-Aib-L-Leu-OH, H-Aib-L-Ala-OH)

Two new organotin(IV) complexes with dianionic dipeptides containing the α-aminoisobutyryl residue (Aib) as ligands are described. The solid complexes [(n-Bu)₂Sn(H₋₁L_A)] · 2MeOH (1 · 2MeOH) (L_AH = H-Aib-L-Leu-OH) and [(n-Bu)₂Sn(H₋₁L_B)] · MeOH (2 · MeOH) (L_BH = H-Aib-L-Ala-OH) have been isolated and characterized by single-crystal X-ray crystallography and spectroscopic techniques (H₋₁L²⁻ is the dianionic form of the corresponding dipeptide). Complexes 1 · 2MeOH and 2 · MeOH are monomeric with similar molecular structures. The doubly deprotonated dipeptide behaves as a N(amino), N(peptide), O(carboxylate) ligand and binds to the Sn^IV atom. The five-coordinate metal ion has a distorted trigonal bipyramidal geometry. A different network of intermolecular hydrogen bonds in each compound results in very dissimilar supramolecular features. The IR, far-IR, Raman and ¹¹⁹Sn NMR data are discussed in terms of the nature of bonding and known structures. The antibacterial and antiproliferative activities as well as the effect of the new compounds on pDNA were examined. Complexes 1 and 2 are active against the gram-positive bacteria Bacillus subtilis and Bacillus cereus. The IC₅₀ values reveal that the two compounds express promising cytotoxic activity in vitro against a series of cell lines.