Steric effects on the electronic and molecular structures of nickel(II) and cobalt(II) 2,6-dipyrazol-1-ylpyridine complexes

The complexes [M(L¹R)₂](BF₄)₂ (M=Ni, Co; L¹R=2,6-dipyrazol-1-ylpyridine [L¹H], 2,6-bis-{3-iso-propylpyrazol-1-yl}pyridine [L¹Prⁱ], 2,6-bis-{3-phenylpyrazol-1-yl}pyridine [L¹Ph], 2,6-bis-{3-[2,4,6-trimethylphenyl]pyrazol-1-yl}pyridine [L¹Mes]) and [M(L²)₂](BF₄)₂ (M=Ni, Co; L²=2-{3-[2,4,6-trimethylphenyl]pyrazol-1-yl}-6-{5-[2,4,6-trimethylphenyl]pyrazol-1-yl}pyridine) have been prepared. Single crystal structure determinations of [M(L¹H)₂](BF₄)₂ (M=Ni, Co) and solvates of [Ni(L¹Mes)₂](BF₄)₂, [Co(L¹Mes)₂](ClO₄)₂ and [Co(L²)₂](BF₄)₂ all show six-coordinate metal centres with local near-D_2d symmetry. The L¹Mes and L² mesityl substituents have only a small effect on the MN{pyrazole} (M=Ni, Co) bond lengths in these compounds. The d–d spectra of the complexes show that L¹Mes is a significantly better donor ligand than L¹H, L¹Prⁱ or L¹Ph, and that L¹Prⁱ is a weaker ligand than might be expected purely on inductive grounds. A combination of UV–Vis/NIR, EPR, NMR and magnetic measurements have demonstrated that all the Co(II) compounds are high-spin in the solid state and in solution at 290 K.     

Ruthenium(II) and palladium(II) complexes with 2,6-(bispyrazol-1-yl)pyridines

Ruthenium(II) and palladium(II) complexes [Ru(DMSO)(L)Cl₂] and [Pd(L)Cl]Cl, where L = 2,6-bis(pyrazol-1-yl)pyridine (bpp) or 2,6-bis(3,5-dimethylpyrazol-1-yl)pyridine (bdmpp) have been synthesized. All complexes were characterized by elemental analysis, IR, ¹H NMR, UV-Vis, and cyclic voltammetry measurements.     

Synthesis,crystal structure and catalytic performance of bis (imino)pyridyl nickel complexes

Two new Ni(II) complexes of 2,6-bis[1-(2,6-diethylphenylimino)ethyl]pyridine (L¹), 2,6-bis[1-(4-methylphenylimino)ethyl]pyridine (L² ) have been synthesized and structurally characterized. Complex Ni(L¹)Cl₂?·?CH₃CN (1), exhibits a distorted trigonal bipyramidal geometry, whereas complex Ni(L¹)(CH₃CN)Cl₂ (2), is six-coordinate with a geometry that can best be described as distorted octahedral. The catalytic activities of complexes 1, 2, Ni{2,6-bis[1-(2,6-diisopropyl-phenylimino)ethyl]pyridine} Cl₂?·?CH₃CN (3), and Ni{2,6-bis[1-(2,6-dimethylphenylimino) ethyl]pyridine}Cl₂?·?CH₃CN (4), for ethylene polymerization were studied under activation with MAO.     

Models for Copper-Dioxygen Complexes: The chemistry of copper(II) with some planar tridentate nitrogen ligands

The solution chemistry of Cu(II) with a series of five planar tridentate nitrogen ligands, 2,6-bis(benzimidazol-2-yl)pyridine (bzimpy, 1 ), 2,6-bis(l-methylbenzimidazol-2-yl)pyridine (mbzimpy, 2 ) 2,6-bis(benzothiazol-2-yl) pyridine (bzthpy, 3 ), 2,6-bis(benzoxazol-2-yl)pyridine (bzoxpy, 4 ), and 2,2′, 6′, 2″-terpyridyl (terpy, 5 ) is reported. Electronic and EPR spectra are consistent with the complexes [CuL]²⁺ having essentially tetragonal structure in solution, with the fourth coordination site in the plane of the ligand occupied by solvent. bzthpy and bzoxpy show smaller ligand-field splittings than bzimpy, mbzimpy, and terpy, and are easily decomplexed from the copper. Substitution of the coordinated solvent molecule in the plane of the ligand is observed with Cl^? and OH^? (provided that the ligand has no acidic protons) for all ligands except terpy. The reaction between [Cu(mbzimpy)]²⁺ and imidazole has been studied by potentiometric titration in MeCN/H₂O 1:1 and shows strong binding of the imidazole in the plane (log K = 4.5 at 25°), and also the formation of an imidazolate-bridged dinuclear species.     

STRUCTURAL STUDIES ON PYRAZOLYLPYRIDINE LIGANDS AND COMPLEXES. 2. COMPARISONS BETWEEN BISPYRAZOLYLPYRIDINE LINKAGE ISOMERS AND WITH 2,2′,6′,2″-TERPYRIDINE JERZY ZADYKOWICZ

Abstract

Crystal structures were obtained for the 3(C),2′;6′,3″(C)-linked bispyrazolylpyridines 2,6-di(2H-4,5,6,7-tetrahydroindazol-3-yl)pyridine (1), 2,6-di(l-methyl-4,5,6,7-tetrahydroindazol-3-yl)pyridine (2), 2,6-di(1 -(4-ethoxycarbonylphenyl)-4,5,6,7-tetrahydroindazol-3-yl)pyridine (3) and for the homoleptic Ru^II complex of 2, [Ru(2)₂]Cl₂, which crystallized with 7 molecules of CHCl₃. Ligand 1 adopts the inter-and intramolecularly hydrogen-bonded syn,syn rotameric conformation, while 2 and 3 were in the anti,anti forms. Relative to the latter, iigand distortions were assessed in 1 (considered as a H⁺ complex) and [Ru(2)₂]Cl₂. Comparisons were drawn with other tridentate ligands containing a pyridine nucleus, specifically the 1(N),2′;6′,1″(N″) linkage isomers and 2,2′;6′,2″-terpyridine, in both free and Ru^II complexed forms, as well as with their bidentate analogues. Unlike with bidentate ligands, the bonds to the pyridine moiety are shortest, the outer heterocyclic rings are drawn inward and, overall, the ligands remain fairly planar. Flanking substituents remain well splayed out in the 1,2′;6′,1″-linked bispyrazolylpyridines, are more parallel in the 3,2′;6′,3″ linkage isomers and are unfavorably compressed in terpyridines.     

Manganese,cobalt and nickel complexes with a novel 17-membered macrocycle containing an N5 donor set

Summary The synthesis of a new macrocycle containing phenanthroline and pyridine subunits is described. The reaction of 2,9-bis(hydrazone)-1,10-phenanthroline with 2,6-bis-(bromomethyl) pyridine in the presence of Mn^II, Co^II or Ni^II ion templates leads to the isolation, in high yield, of the seven-coordinate complexes [M(L³)Br₂] (L³ = 4,5, 6,7,8,9-phenanthrolino-14,15,16-pyridino-1,2,5,8,11,12,15 heptaazacycloheptadecane,2,10-diene). The compounds were characterized by physical measurements, which indicated that in all the complexes the ligand is acting as a pentadentate N₅ chelating agent.     

Electrochemical Determination of the KRAS Genetic Marker for Colon Cancer with Modified Graphete and Graphene Paste Electrodes

The determination of KRAS was performed using electrochemical sensing devices based on graphite and graphene pastes, modified with a phthalocyanine-boron dipyrromethene (BODIPY) and azulenes dyes. The limits of quantification for KRAS were 1.54?×?10^?4?µg/mL using the sensor based on the phthalocyanine-BODIPY dye and graphite, 2.64?×?10^?7?µg/mL using the sensor based on 2,6-bis((E)-2-(furan-2-yl)vinyl)-4-(4,6,8-trimethylazulen-1-yl)pyridine/TiO₂Pt/reduced graphene oxide, and 3.84?×?10^?3?µg/mL using the sensor based on 2,6-bis((E)-2-(thiophen-3-yl)vinyl)-4-(4,6,8-trimethylazulen-1-yl)pyridine/TiO₂Pt/reduced graphene oxide. Recovery measurements demonstrated the suitable analytical performance of these sensors for the early detection of colon cancer by the analysis of whole blood samples.     

Synthesis,characterization and comparative studies of mono- and dimeric copper(II) complexes containing tripodal ligands

Mono and dimeric bromo-bridged copper(II) complexes of the type [CuBr₂(L)] and [Cu₂Br₂(L)₂](ClO₄)₂ containing nitrogen donor tripodal ligands L = 2,6-bis(pyrazol-1-yl)pyridine (bppy) or 2,6-bis(3,5-dimethylpyrazol-1-yl)pyridine (dmbppy) have been synthesized. All complexes have been characterized by elemental analysis, IR, ESR and electronic spectra and magnetic susceptibility and cyclic voltammetry measurements.     

Synthesis,structure, ADME and biological activity of three 2,6-disubstituted thiosemicarbazone derivatives

Three new 2,6-disubstituted thiosemicarbazone derivatives of pyridine, namely, 2-{amino[6-(pyrrolidin-1-yl)pyridin-2-yl]methylidene}-N,N-dimethylhydrazine-1-carbothioamide, C₁₃H₂₀N₆S, 2-{amino[6-(piperidin-1-yl)pyridin-2-yl]methylidene}-N,N-dimethylhydrazine-1-carbothioamide, C₁₄H₂₂N₆S, and 2-[amino(6-phenoxypyridin-2-yl)methylidene]-N,N-dimethylhydrazine-1-carbothioamide monohydrate, C₁₅H₁₇N₅OS·H₂O, have been synthesized and characterized by NMR spectroscopy and low-temperature single-crystal X-ray diffraction. In addition, their antibacterial and anti-yeast activities have been determined. The ability of the tested compounds to inhibit bacterial growth was comparable to vancomycin as a reference drug. Compared to isoniazid (MIC 0.125 and 8 µg ml⁻¹), the compounds showed the ability to inhibit the growth of Mycobacterium tuberculosis to a moderate degree for the standard strain and at the same level or higher (MIC 4–8 µg ml⁻¹) for the resistant strain. All three compounds adopt the zwitterionic form in the crystal structure regardless of the presence or absence of solvent molecules.     

Cyclometalated rhodium complexes of phenyl- and diphenyl-substituted oxazole and thiazole luminophores

Cyclometaleted rhodium complexes of oxazole and thiazole luminophores [Rh(C??N)₂En]Cl [(C??N)^?, deprotonated forms of 2,5-diphenyloxazole, 2-phenylbenzothiazole, 2-(biphenyl-4-yl)-6-phenylbenzoxazole, and 2-(biphenyl-4-yl)-5-phenyloxazole; En ?? ethylenediamine] were obtained and characterized by the methods of ¹H NMR, IR, and electron absorption and emission spectroscopy. Two cyclometallated ligands in the inner sphere of the complexes are in the cis-C,C positions. Cyclometallating of the luminophores results both in a red shift of intraligand ??-??*-optical transitions (???? ??1.2 kK) as compared to free luminophores and in the appearance of a long-wave band (??_max 376?C392 nm) of a mixed nature: metal-ligand charge transfer/intraligand transition. Alongside with the internal conversion to a low-energy state of the metal-ligand charge transfer/ intraligand transition, the emission degradation of photoexcitation energy results in the intraligand ??-??*-fluorescence of the complexes (??_max 390?C423 nm) at room temperature.     

Synthesis, structural characterization, and luminescence properties of multinuclear silver complexes of pyrazole-functionalized NHC ligands containing Ag-Ag and Ag-π interactions

A few pyrazole-functionalized imidazolium salts have been prepared via the reactions of N-alkylimidazole and 3,5-bis(chloromethyl)pyrazole or 2-(1-(2-chloroethyl)-5-methyl-1H-pyrazol-3-yl)-6-(5-methyl-1-vinyl-1H-pyrazol-3-yl) pyridine. Reactions of these imidazolium salts with Ag₂O led to the successful isolation of tetranuclear [Ag₄(L)₂](X)₂ (X = PF₆⁻ or BF₄⁻; H₃L1 = 3,5-bis(N-benzylimidazoliumyl)pyrazole, H₃L2 = 3,5-bis(N-(2,4,6-trimethylphenyl)imidazoliumyl)pyrazole, H₃L3 = imidazolium cyclophane from the condensation of 3,5-bis(chloromethyl)pyrazole and 1,4-bis(imidazolyl)butane) and trinuclear silver clusters supported by N-heterocyclic carbene ligands in high yields. The molecular structures of these silver complexes have been confirmed by ¹H, ¹³C NMR, ESI-MS spectroscopy, and X-ray diffraction analyses. The tetranuclear complexes [Ag₄(L1)₂](PF₆)₂ (1) and [Ag₄(L2)₂](BF₄)₂ (2) consist of a pair of Ag-Ag contacts (ca. 3.11 Å) showing weak silver-silver interaction. [Ag₄(L3)₂](PF₆)₂ (3) has a square planar Ag₄ core sandwiched by two NHC cyclophanes with Ag-Ag distances of 3.22 Å. All the silver atoms in 1-3 are located in the same linear C-Ag-N coordination environment. [Ag₃(L4)₂] (PF₆)₃ (HL4 = 2-(1-(2-methylimidazoliumylethyl)-5-methyl-1H-pyrazol-3-yl)-6-(5-methyl-1-vinyl-1H-pyrazol-3-yl) pyridine) (4) is a trinuclear complex in which the three silver are bridged by two L4 molecules, and the Ag₃ units form one-dimensional chain via Ag-π interaction. The luminescence properties of the imidazolium salts and their silver complexes were also studied.     

Syntheses,crystal structures and luminescence of 2,6- bis - (5-phenyl-1H-pyrazol-3-yl)pyridine and its d10 metal complexes

A new bis-pyrazole derivative, 2,6-bis-(5-phenyl-1H-pyrazol-3-yl) pyridine (H₂BPPP), and two d¹⁰ metal complexes [Zn(H₂BPPP)Cl₂](DMF)₂ (1), [Cd(H₂BPPP)Cl₂](DMF)₂ (2) have been synthesized and characterized. There is a tautomeric equilibrium of the bis-pyrazole compound in solution and the H atom of pyrazolyl NH can transfer to the adjacent N atoms. X-ray structure analyses reveal the H atom is on the 2-position of pyrazolyl ring in donor solvents, while the H atom is on the 1-position of pyrazolyl ring in metal complexes. The luminescence of the ligand and complexes have been investigated.     

Synthesis, luminescence properties of a novel aromatic carboxylic acid (L) and corresponding Eu(III) and Tb(III) compounds as well as the binding characteristics of L with bovine serum albumin (BSA)

A novel polyamino polycarboxylic pyridine derivative ligand, N,N,N¹,N¹-(2,6-bis((3-(aminoethyl)-5-methyl-1H-pyrazol-1-yl)methyl)pyridine)hexakis(acetic acid) (L), was designed and synthesized with the motive that it is able to sensitize the emission of lanthanides. Its corresponding Eu(III) and Tb(III) complexes Na₄EuLCl₃·3H₂O and Na₄TbLCl₃·5H₂O were successfully prepared. The ligand and the complexes were characterized by elemental analysis, IR, MS, NMR and TG-DTA. The luminescence properties of the compounds in solid state were investigated; each complex had very narrow emission bands and strong luminescence intensity up to about 10,000. The TG-DTA studies showed that the initial decomposition temperature of both complexes was over 250 °C, elucidating the complexes had a high thermal stability. Meanwhile, the comparison with similar complexes suggested that the ligand with more coordination sites possessed more efficient antenna effect. To explore the potential medicinal value of L, the binding interaction of L and bovine serum albumin (BSA) was carried out by fluorescence spectrum. The studies indicated that the reaction between L and BSA was a static quenching procedure. The binding site number n and binding constant Ka were calculated according to the double logarithm regression equation. The thermodynamic parameters showed the Van der Waals and hydrogen bond interactions were the mainly impulse to the reaction.     

Tetranuclear Zn(II) complexes with compartmental and dicyanamido ligands: synthesis,structure, and luminescent properties

New tetranuclear compounds have been obtained by reacting binuclear complexes, [Zn₂L ⁿ (μ-OH)(H₂O)₂](ClO₄)₂, with sodium dicyanamide (HL ⁿ are end-off bicompartmental ligands resulting from condensation between 2,6-diformyl-p-cresol with N,N-dimethyl-ethylenediamine or 2-aminomethyl-pyridine). The complexes, [{L¹(μ-OH)Zn₂}(μ _1,5-dca)₂{Zn₂(μ-OH)L¹}](ClO₄)₂ (1) and [{Zn₂L²(μ ₃-OH)(dca)}₂](ClO₄)₂?·?2H₂O (2), have been characterized by single-crystal X-ray diffraction. The angular nature of the bridging dicyanamido induces the “M” shape of the tetranuclear cationic unit in 1. The tetranuclear cation, because of its particular shape, acts as a receptor toward one perchlorate ion, which is hydrogen bonded to the hydroxo groups. This tetranuclear unit in 2 has a defective heterocubane structure. The luminescence properties of the new tetranuclear complexes have been investigated.     

Cyclooctenyl complexes of palladium(II) with multidentate N-heterocycles

[Pd(cod)(cotl)]ClO₄ (cod = 1,5-cyclooctadiene, cotl = cyclooctenyl, C₈H₁₃ ^–) undergoes substitutions with multidentate N-heterocycles: 1,3-bis(benzimidazolyl)benzene (L¹), 1,3-bis(1-methylbenzimidazol-2-yl)benzene (L²), 2,6-bis(benzimidazolyl)pyridine (L³) and 2,6-bis(1-methylbenzimidazol-2-yl)pyridine (L⁴) to yield mono/binuclear complexes: [Pd(cotl)(L¹)(OClO₃)], [Pd(cotl)(L)]ClO₄ (L = L² or L³) and [Pd(cotl)₂(L⁴)](ClO₄)₂. Dihalobridged binuclear complexes [PdX(cotl)]₂ (X = Cl or Br) undergo halogen bridge cleavages with the multidentate N-heterocycles to form binuclear complexes of the type [PdX(cotl)₂L] (X = Cl or Br; L = L¹, L², L³ or L⁴). The complexes were characterized by elemental analyses, ¹H-, ¹³C-n.m.r., i.r., far-i.r. and FAB-mass spectral studies.     

Iron(II) Complexes of Chiral Tridentate Nitrogen Donors and their Application in Catalytic Hydrosilylation Reactions

Enantiomerically pure, C₂-symmetric 2,6-bis(pyrazol-3-yl) pyridine ligands were obtained by treatment of diethyl-2,6-pyridinedicarbonate with (1R,4R)-(+)-camphor in the presence of NaH followed by ring closure with hydrazine. After twofold N-alkylation at the pyrazole rings, the addition of iron(II) chloride led to the according pentacoordinate dichloridoiron(II) complexes. All intermediates of the ligand synthesis, the ligands bearing NCH₃ and NCH₂C₆H₅ groups and the derived iron(II) complexes were structurally characterized by means of X-ray structure analysis. In-situ reaction with iron(II) carboxylates resulted in the formation of iron(II) carboxylate complexes, which turned out to be highly active in the hydrosilylation of acetophenone. However, even at room temperature, the enantiomeric excess of the product 1-phenylethanol is poor. ⁵⁷Fe Mössbauer spectroscopy gave an insight into the species formed during catalysis.     

The chloro-substituent enhances performance of 2,4-bis (imino)pyridylchromium catalysts yielding highly linear polyethylene

The five unsymmetrical 2-[1-(2,4-dibenzhydryl-6-chlorophenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridine compounds (aryl: 2,6-Me₂Ph L1 , 2,6-Et₂Ph L2 , 2,6-ⁱPr₂Ph L3 , 2,4,6-Me₃Ph L4 and 2,6-Et₂–4-MePh L5 ) were prepared and characterized with FT-IR and ¹H/¹³C NMR spectroscopy as well as elemental analysis. The treatment of L1 – L5 with CrCl₃·3THF affords the corresponding chromium chloride complexes ( Cr1 – Cr5 ) in excellent yields. The molecular structures of Cr2 and Cr3 characterized by X-ray diffraction show a distorted octahedral geometry with three nitrogen atoms and three chlorine atoms around the metal center. On activation with either MAO or MMAO, Cr1 – Cr5 collectively display high activity (up to 14.96 × 10⁶ g (PE) mol⁻¹ (Cr) h⁻¹ at 60 °C) affording highly linear polyethylene with low molecular weight distribution (M_w/M_n) ranging from 1.06 to 2.81. An in-depth catalytic evaluation of Cr1 was conducted in order to investigate how the cocatalyst type and its amount, reaction temperature and polymerization time affect the catalytic activities and polymer properties.     

Enhancement of luminescence lifetimes of mononuclear ruthenium(II)-terpyridine complexes by manipulation of the sigma-donor strength of ligands

The synthesis and characterization of mixed ligand 2,2';6',2' '-terpyridine (tpy) ruthenium complexes with 2,6-bis([1,2,4]triazol-3-yl)pyridine, 2,6-bis(5-phenyl-[1,2,4]triazol-3-yl)pyridine, and 2,6-bis([1,2,3,4]tetrazol-5-yl)pyridine are reported. The species are characterized by HPLC, 1H NMR, UV/vis, and emission spectroscopy. The photophysical properties of the complexes are investigated as a function of temperature over the range 80-320 K. The emission lifetime observed for the fully deprotonated compounds at room temperature is about 80 ns. This increase by 2 orders of magnitude with respect to the parent "[Ru(tpy)2](2+)" complex is rationalized by an increase in the energy of the metal based dsigma orbital, rather than by manipulation of the pi* orbitals on the ligands. The acid-base and electrochemical properties of the compounds are reported also.     

Discovery of New Pyrazolopyridine,Furopyridine, and Pyridine Derivatives as CDK2 Inhibitors: Design,Synthesis, Docking Studies,and Anti-Proliferative Activity

New pyridine, pyrazoloyridine, and furopyridine derivatives substituted with naphthyl and thienyl moieties were designed and synthesized starting from 6-(naphthalen-2-yl)-2-oxo-4-(thiophen-2-yl)-1,2-dihydropyridine-3-carbonitrile (1). The chloro, methoxy, cholroacetoxy, imidazolyl, azide, and arylamino derivatives were prepared to obtain the pyridine-⁻C² functionalized derivatives. The derived pyrazolpyridine-N-glycosides were synthesized via heterocyclization of the C²-thioxopyridine derivative followed by glycosylation using glucose and galactose. The furopyridine derivative 14 and the tricyclic pyrido[3′,2′:4,5]furo[3,2-d]pyrimidine 15 were prepared via heterocyclization of the ester derivative followed by a reaction with formamide. The newly synthesized compounds were evaluated for their ability to in vitro inhibit the CDK2 enzyme. In addition, the cytotoxicity of the compounds was tested against four different human cancer cell lines (HCT-116, MCF-7, HepG2, and A549). The CDK2/cyclin A2 enzyme inhibitory results revealed that pyridone 1, 2-chloro-6-(naphthalen-2-yl)-4-(thiophen-2-yl)nicotinonitrile (4), 6-(naphthalen-2-yl)-4-(thiophen-2-yl)-1H-pyrazolo[3,4-b]pyridin-3-amine (8), S-(3-cyano-6-(naphthaen-2-yl)-4-(thiophen-2-yl)pyridin-2-yl) 2-chloroethanethioate (11), and ethyl 3-amino-6-(naphthalen-2-yl)-4-(thiophen-2-yl)furo[2,3-b]pyridine-2-carboxylate (14) are among the most active inhibitors with IC₅₀ values of 0.57, 0.24, 0.65, 0.50, and 0.93 µM, respectively, compared to roscovitine (IC₅₀ 0.394 μM). Most compounds showed significant inhibition on different human cancer cell lines (HCT-116, MCF-7, HepG2, and A549) with IC₅₀ ranges of 31.3–49.0, 19.3–55.5, 22.7–44.8, and 36.8–70.7 μM, respectively compared to doxorubicin (IC₅₀ 40.0, 64.8, 24.7 and 58.1 µM, respectively). Furthermore, a molecular docking study suggests that most of the target compounds have a similar binding mode as a reference compound in the active site of the CDK2 enzyme. The structural requirements controlling the CDK2 inhibitory activity were determined through the generation of a statistically significant 2D-QSAR model.     

Synthesis,spectral, thermal,solid state d.c. electrical conductivity,fluorescence and biological studies of lanthanum(III) and thorium(IV) complexes of 24-membered macrocyclic triazoles

A series of La(III) and Th(IV) complexes have been synthesized by template condensation of 2,6-diformyl-4-methylphenol, bis-(4-amino-5-mercapto-1,2,4-triazol-3-yl)alkanes and La(NO₃)₃ ·?6H₂O/Th(NO₃)₄ ·?5H₂O in 2 : 2 : 1 molar ratio in ethanol. These complexes were characterized by elemental analyses, magnetic susceptibility, molar conductance, spectral (IR, UV–Vis, ¹H-NMR, FAB-mass), thermal, fluorescence and solid state d.c. electrical conductivity studies. The complexes are insoluble in water but soluble in DMF and DMSO. The observed molar conductance values indicate non electrolytes. Elemental analyses suggest 1 : 1 stoichiometry, [La(L^I–IV)(NO₃)(H₂O)₂] ·?3H₂O and [Th(L^I–IV)(NO₃)₂(H₂O)₂] ·?3H₂O. Spectroscopic studies indicate that coordination occurs through phenolic oxygen after deprotonation, nitrogen of azomethine group and bridging bidentate nitrates. The solid state d.c. electrical conductivity indicates semiconducting nature. All the Schiff bases and their La(III) and Th(IV) complexes were evaluated for biological properties; some compounds show promising results.