The Effect of Fused 12-Membered Nickel Metallacrowns on DNA and their Antibacterial Activity

The synthesis, characterization and the biological study of a series of Ni(ll)₂(carboxylato)₂ [12- MC_{Ni(II)N(shi)2(pko)2}-4][12-MC_{Ni(ii)N(sh03(pko)}-4] (CH₃OH)₃(H₃O) fused 12-membered metallacrowns with 10 metal ions and commercial available herbicides or anti-inflammatory drugs as carboxylato ligands are reported. All the compounds have a mixed ligand composition with salicylhydroxamic acid and di-2-pyridylketonoxime as chelate agents. The compounds construct metallacrown cores {[12-MC_{Ni(n)N(sj02(pko)2}-4][12-MC_{Ni(ll)N(shO3(pko)}-4]}²⁺ following the pattern [-Ni-O-N-]₄. The neutral decanuclear [Ni(II)(A)]₂[12-MC_{Ni(II)N(shi)2(pko)2}-4][12-MC_{Ni(II)N(pko)3(pko)}-4] fused metallacrown, consists of two [12-MC_{M(ox)N(ligand)}-4] units the {Ni(ll)(A)[12-MC_{Ni(II)N(shi)2(pko)2}-4]} and {Ni(II)(A)[12-MC_{Ni(II)N(shi)3(pko)}-4]} with 1⁺ and 1^- charge, respectively. Each metallacrown unit has four ring Ni(II) ions and one additional encapsulated Ni(II) ion in planar arrangement. The anionic unit is bonded with cationic one creating binuclear moieties. The herbicide or antiiflammatory carboxylato ligands are bridging the central octahedral nickel atom with a ring metal ion in a bindetate fashion. The effect on DNA and their antibacterial activity was examined. The changes in the mobility can be attributed to the altered structures of the pDNA treated with Ni(II) complexes. Evaluating the data of the antibacterial activity of the compounds tested, we can conclude that nickel complexes present strong antibacterial activity.     

Nucleophilic addition and various species formed in the Cu(II)NCO−3(5)-methylpyrazole system

From the Cu(II)NCO⁻3(5)-methylpyrazole (mpz) system two compounds Cu(NCO)₂(mpz)₂ and four compounds Cu(mpz·NCO)₂ were isolated. The latter compounds contain carbamoylmethylpyrazolate anions as chelate ligands and are coligand isomers of the cyanate compounds. According to the results of indirect structural methods, the Cu(NCO)₂(mpz)₂ complexes have pseudooctahedral structures and differ in their polyhedron distortions. The Cu(mpz·NCO)₂ complexes show tetragonally distorted six or five coordinate structures, possibly differing also by the methyl group position on the pyrazole ring.     

Synthesis,structure and a fourier transform infrared study of Pt(II), Cu(II), and Mg(II) Complexes with xanthosine-5′-monophosphate

The reaction of xanthosine-5′'-monophosphate disodium salt (5′-XMPNa₂) with Pt(II), Cu(II) and Mg(II) ions produced compounds of the type cis- and trans-Pt(NH₃)₂(XMPNa₂)_nCl₂·xH₂O, where n = 1 or 2; Pt(XMPNa₂)_nCl₂·xH₂O, where n = 1-4, x = 1,4 & 6; Cu(XMP)·6H₂O and Mg(XMP)·xH₂O, where x = 9 or 4. In the complexes synthesized here at neutral pH values, the nucleotide binds through the N_7-atom of the purine ring system, whereas for Cu(II) and Mg(II) compounds obtained at pH = 4 a direct metal-phosphate interaction as well as N_τ bonding is proposed.     

Synthesis,antioxidant and carbonic anhydrase I and II inhibitory activities of novel sulphonamide-substituted coumarylthiazole derivatives

New secondary benzenesulphonamide-substituted coumarylthiazole derivatives were synthesized and their inhibitory effects on purified carbonic anhydrase I and II were evaluated using CO₂ as a substrate. The result showed that all the synthesized compounds exhibited inhibitory activity on both hCA I and hCA II with N-(4-(2-oxo-2H-chromen-3-yl)thiazol-2-yl)naphthalene-2-sulphonamide (5f, IC₅₀ value of 5.63 and 8.48?µM, against hCA I and hCA II, respectively) as the strongest inhibitor revealed from this study. Structure–activity relationship revealed that the inhibitory activity of the synthesized compounds is related to the type of the halogen and bulky substituent on the phenyl ring. In addition, the cupric reducing antioxidant capacities (CUPRAC) and ABTS cation radical scavenging abilities of the synthesized compounds were assayed. 4-methoxy-N-(4-(2-oxo-2H-chromen-3-yl)thiazol-2-yl)benzenesulphonamide (5e) exhibited the strongest ABTS and CUPRAC activity with IC₅₀ value of 48.83?µM and A_0.50 value of 23.29?µM, respectively.     

Synthesis 4-[2-(2-mercapto-4-oxo-4H-quinazolin-3-yl)-ethyl]-benzenesulfonamides with subnanomolar carbonic anhydrase II and XII inhibitory properties

Condensation of substituted anthranilic acids with 4-isothiocyanatoethyl-benzenesulfonamide led to series of heterocyclic benzenesulfonamides incorporating 2-mercapto-quinazolin-4-one tails. These sulfonamides were investigated as inhibitors of the human carbonic anhydrase (hCA, EC 4.2.1.1) isoforms hCA I and II (cytosolic isozymes), as well as hCA XII (a transmembrane, tumor-associated enzyme also involved in glaucoma-genesis). The new sulfonamides acted as medium potency inhibitors of hCA I (K_Is of 28.5–2954 nM), being highly effective as hCA II (K_Is in the range of 0.62–12.4 nM) and XII (K_Is of 0.54–7.11 nM) inhibitors. All substitution patterns present in these compounds (e.g., halogens, methyl and methoxy moieties, in positions 6, 7 and/or 8 of the 2-mercapto-quinazolin-4-one ring) led to highly effective hCA II/XII inhibitors. These compounds should thus be of interest as preclinical candidates in pathologies in which the activity of these enzymes should be inhibited, such as glaucoma (CA II and XII as targets) or some tumors in which the activity of isoforms CA II and XII is dysregulated.     

In-vitro antibacterial and cytotoxic activity of cobalt (ii), copper (ii), nickel (ii) and zinc (ii) complexes of the antibiotic drug cephalothin (Keflin)

Keflin (kefl) interacts with Co(II), Cu(II), Ni(II) and Zn(II) metal ions leading to complexes of the type M(kefl)₂Cl₂ and M(kefl)Cl₂, which have been characterized by physicochemical and spectroscopic methods. Magnetic moment, IR, electronic spectral and elemental analyses data suggest that keflin behaves tridentately forming octahedral or trigonal bipyramidal complexes with the metal ions mentioned above. The new compounds have been screened in-vitro for antibacterial and cytotoxic activity against Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella typhi, Shigella dysentriae, Bacillus cereus, Corynebacterium diphtheriae, Staphylococcus aureus and Streptococcus pyogenes bacterial strains. Compounds, 4 and 8 showed promising activity (90%) against seven, compound 6 showed significant activity (52%) against four and, compounds 1 and 5 showed activity (40%) against three test bacterial strains at concentration of 10 μM.     

7-Substituted-sulfocoumarins are isoform-selective,potent carbonic anhydrase II inhibitors

A series of 7-substituted sulfocoumarins and 3,4-dihydrosulfocoumarins was obtained by cyclization of the methanesulfonate of 2,4-dihydroxy- or 2-hydroxy-4-methoxybenzaldehyde, followed by derivatization reactions. The new compounds incorporate a range of substituents in position 7 of the heterocyclic ring (hydroxyl, methoxy, carboxylic and alkylsulfonate ester). The compounds were tested for the inhibition of the zinc enzyme human (h) carbonic anhydrase (hCA, EC 4.2.1.1). Unlike the 6-substituted sulfocoumarins which were potent hCA IX and XII inhibitors and ineffective hCA I and II inhibitors, compounds from this series showed low nanomolar hCA II inhibitory properties, and inhibited the mitochondrial isoform hCA VA with K_Is in the range of 91–9960 nM, but were ineffective as hCA I, IX and XII inhibitors. The structure activity relationship for this class of inhibitors was rather clear, with the nature of the 7-substituent strongly influencing hCA VA inhibition, whereas the nature of these groups were less relevant for hCA II inhibition (all reported compounds were highly effective hCA II inhibitors, with K_Is in the range of 1.5–8.4 nM). Since both hCA II and hCA VA are important drug targets (hCA II for antiglaucoma agents; hCA VA for antiobesity drugs), these isoform-selective inhibitors reported here may be considered of interest for various biomedical applications.     

Some new derivatives of Ni(II) with uracil,uridine and nucleotides

This paper describes the synthesis of compounds of Ni(II) with uracil, uridine and the nucleotides 5′UMP, 5′CMP, 5′GMP and 5′IMP, and their characterization, carried out by elemental analysis, by studying the infrared spectra, diffuse reflectance and conductivity measurement.In the complexes of NiURA (and NiURD) with acetate, direct coordination of the metal ion to the C₄O group of the pyrimidine ring is inferred from the changes observed on the infrared spectrum of the corresponding bands at vCO. The variations in frequency of the vCOO symmetric and asymmetric bands of the acetate group together with the conductivity and reflectance results seem to indicate the dimer structure of the compounds.In the compounds of NiURA (and NiURD) with ethylenediamine indirect bonding of Ni(II)to the pyrimidine ring is inferred, probably established through hydrogen bonds involving the C₄O groups in the base or nucleoside and the −NH₂ groups in the ethylenediamine.In the complexes of Ni-nucleotide, bonding seems to occur through the heterocyclic ring (C₄O for 5′UMP, N(3) for 5′CMP, N(7) for 5′GMP and 5′IMP) together with additional interactions through the phosphate group.     

Insight into shock-induced chemical reaction from the perspective of ring strain and rotation of chemical bonds

Density functional theory BLYP/DNP and hyperhomodesmotic equations were employed to calculate ring strain energy, the bond dissociation energy of X–NO₂ (X=C, N) and the charges on the nitro groups of several four-membered and six-membered heterocycle compounds. BLYP/DNP and LST/QST + CG method were also applied to calculate bond rotational energy of X–NO₂ (X=C, N) of above mentioned compounds. It indicated that ring strain energy of four-membered heterocycle nitro compounds is apparently higher than that of six-membered heterocycle nitro compounds. Predictably, ring-opening reactions may preferentially occur for those compounds containing higher ring strain energy under shock. In addition, C–NO₂ bonds in these compounds may rotate easier than N–NO₂ bonds in response to the external shock. As for N–NO₂ bonds in these compounds, they also respond to the external shock by the rotation of N–NO₂ bonds, once to the saddle point of the rotational energy barrier, the whole molecule will become relaxed, N–NO₂ bond becomes weaker and eventually leads to the breakage. When one ?C=O, ?C=NH or ?NH₂ group is introduced to the six-membered heterocycle, the charges on the nitro groups of the new compound decrease drastically, and ring strains increase remarkably. It can be predicted that the new compounds will be more sensitive to shock, and the viewpoint is confirmed by the experimental results of shock sensitivity (small scale gap test) of several explosives.     

Design,synthesis and biological evaluation of novel perimidine o-quinone derivatives as non-intercalative topoisomerase II catalytic inhibitors

For the development of novel anticancer agents, we designed and synthesized a total of 37 perimidine o-quinone derivatives containing the o-quinone group at the A or B ring and different substituents (alkyl groups, aryl groups or heterocycles) at the C ring of the compounds. The structure-activity relationships (SARs) were established based on the cytotoxicity data of compounds from the HL-60, Huh7, Hct116, and Hela cell lines. The cytotoxicity results showed that most compounds exhibited potent cytotoxicity. In particular, compound b-12 showed the best anti-proliferative activity (IC₅₀ ≤ 1 μM) against four cancer cell lines and strong potency against the HL-60/MX2 (0.47 μM) cell line, which is resistant to Topo II poisons. Further studies showed that b-12 exhibited potent Topo IIα inhibitory activity (IC₅₀ = 7.54 μM) compared with Topo I, which acted as a class of non-intercalative Topo IIα catalytic inhibitor by inhibiting the ATP binding site of Topo II. Cell apoptosis and cell cycle assays confirmed that b-12 could induce the apoptosis of Huh7 cells in a dose-dependent manner.     

New macrocyclic Cu(II)-bischelates with paddle wheel Cu2-acetate cage

Two novel bolaamphiphile based dicarboxylic ligands L1H₂ and L2H₂ are synthesized by desymmetrizing aromatic anhydrides. The corresponding Cu(II) complexes [Cu(L1) · EtOH]₂ (1), [Cu(L2) · (CH₃CN)]₂ (2) are synthesized and characterized. The crystal structure obtained for (1) and (2) indicates that they are new class of tetralactone type macrocyclic Cu(II) chelate complexes with paddle wheel Cu₂-acetate cage structure. The 1:1, Cu(II) and ligand ratio leads into formation of a novel binuclear Cu(II) tetracarboxylate complexes. The macrocyclic chelate ring size in compounds 1 and 2 was altered from [15] membered to [19] membered by introducing phthalyl and diphenyl head groups as discussed in detail. The single crystal X-ray structure shows the Cu(II)?Cu(II) distance 2.613(13) Å for 1 and 2.626(13) Å for 2, the corresponding room temperature EPR spectra recorded for powdered polycrystalline samples indicate the existence of Cu(II)?Cu(II) dimeric system.     

β-Diketiminato 3d-metal compounds: Synthesis, characterization and catalytic behavior towards ethylene

The lithium β-diketiminate (1c, [Li{N(2,6-ⁱPr₂C₆H₃)C(Ph)CHC(^tBu)NH}]₂ represented as (LiL)₂) reacted with 3d-metal (II) chlorides to afford the corresponding compounds (2-7). All metal compounds were fully characterized by elemental, spectroscopic analyses and the single-crystal X-ray diffraction. The coordination geometries around the metals are shown to be tetrahedral within the trinuclear Co₂Li compound (2), planar in ML₂ (M = Co, 3), pseudo-tetrahedral conformation in the ML₂ with M as Mn (4), Fe (5) or Zn (6), and square planar in the dinickel compound (7). Indicated by the trimetallic Co₂Li compound 2, a six-membered ring is constructed of three metal atoms and three bridged chlorides as a twisted conformation. An inversion center is present in the centroid of the Ni₂Cl₂ four-membered ring within compound 7. The plausible mechanism of forming ML₂ was proposed through the chloro-bridged multinuclear compounds on the basis of isolated intermediates of trinuclear (2) and dinuclearic (7) compounds. Upon treatment with methylaluminoxane (MAO), the nickel compound 7 possessed good activity towards ethylene oligomerization, whereas the other metal compounds showed moderate activities towards ethylene polymerization.     

Synthesis, spectroscopy and magnetism of novel metal complexes of 3-aminoflavone (3-af). X-ray crystal structure of 3-af and [Cu(3-af)2(NO3)2]

The synthesis and characterization of four new complexes with the bioactive ligand 3-aminoflavone (3-af) are reported. The complexes of general formula [M(3-af)₂(H₂O)₂](NO₃)₂ · nH₂O], where M = Co(II), Ni(II), and Zn(II), and n = 0, 2, 0, respectively, and [Cu(3-af)₂(NO₃)₂] compound were prepared and studied. In particular, to investigate the binding in detail, the crystal structures of the free ligand (3-af) and [Cu(3-af)₂(NO₃)₂] (1) were determined. The new coordination compounds were identified and characterized by elemental analysis, magnetic measurements, and infrared and ligand-field spectra. The crystal structure of the Cu(II) complex reveals that the ligand acts as a N,O-bidentate chelate ligand forming a five-membered ring with the copper(II) ion. The copper(II) ion is octahedrally surrounded by the two amino nitrogens and two carbonyl oxygens from two chelating organic ligands in trans arrangement. Two molecules of coordinated nitrate anions occupy axial positions. The spectral and magnetic properties are in accordance with the structural data of the copper(II) compound. From X-ray powder-diffraction patterns and IR spectra, the complexes of nickel(II) (2) and cobalt(II) (3) were found to be mutually isomorphous. The results of the spectroscopic studies suggest a mononuclear structure of 2 and 3 complexes. The variable-temperature (1.8-300 K) magnetic susceptibility data of 2 indicate a weak ferromagnetic interaction. The magnetic behavior of complex 3 is characteristic of cobalt(II) systems with an important orbital contribution via spin-orbit-coupling and also suggests a weak ferromagnetic interaction.     

Synthesis and characterization of novel unsymmetrical macrobicyclic tricompartmental mono and binuclear nickel(II) complexes: Electrochemical and kinetic studies of phosphate hydrolysis

A series of macrobicyclic mono and binuclear nickel(II) complexes of type [NiL](ClO₄) and [Ni₂L](ClO₄)₂, where L is macroyclic ligand derived from the precursor compound 3,4:10,11-dibenzo-1,13[N,N′-bis{(3-formyl-2-hydroxy-5-methyl)benzyl}diaza]-5,9-dioxocyclopentadecane, have been synthesized in order to examine electrochemical and catalytic studies on the basis of macrocyclic ring size. The macrocycle consists of three dissimilar compartments arising from ether oxygen, tertiary nitrogen and imine nitrogen atoms. Electrochemical studies have shown that the mononuclear nickel(II) complexes undergo quasireversible single step one electron reduction and oxidation and binuclear nickel(II) complexes undergo two quasireversible one electron reduction and oxidation. The EPR silent nature is ascribed to Ni(II) state and all the nickel(II) complexes have square planar geometry and are diamagnetic in nature. The complexes were subjected to hydrolysis of 4-nitrophenyl phosphate and the catalytic activities of the complexes are found to increase with macrocyclic ring size of the complexes. As the macrocyclic ring size of the complexes increases, the spectral, electrochemical and catalytic studies of the complexes show remarkable variation due to distortion in the geometry around the nickel(II) centre.     

Synthesis and characterization of selective dopamine D2 receptor antagonists. 2. Azaindole,benzofuran, and benzothiophene analogs of L-741,626

A series of indole, 7-azaindole, benzofuran, and benzothiophene compounds have been prepared and evaluated for affinity at D_2-like dopamine receptors. These compounds share structural elements with the classical D_2-like dopamine receptor antagonists haloperidol, N-methylspiperone and benperidol. Two new compounds, 4-(4-iodophenyl)-1-((4-methoxy-1H-indol-3-yl)methyl)piperidin-4-ol (6) and 4-(4-iodophenyl)-1-((5-methoxy-1H-indol-3-yl)methyl)piperidin-4-ol (7), were found to have high affinity to and selectivity for D₂ versus D₃ receptors. Changing the aromatic ring system from an indole to other heteroaromatic ring systems reduced the D₂ binding affinity and the D₂ versus D₃ selectivity.     

Synthesis of novel benzenesulfonamide bearing 1,2,3-triazole linked hydroxy-trifluoromethylpyrazolines and hydrazones as selective carbonic anhydrase isoforms IX and XII inhibitors

A series of twenty four hydroxy-trifluoromethylpyrazoline-carbonyl-1,2,3-triazoles and four hydrazones bearing benzenesulfonamide moieties was obtained by condensation of carboxyhydrazides with substituted 1,3-diketones. All the newly synthesized compounds were investigated as inhibitors of physiologically and pharmacologically relevant human (h) carbonic anhydrsae (CA, EC 4.2.1.1) cytosolic isoforms hCA I and II, as well as transmembrane tumor-assosciated isoforms hCA IX and XII. These compounds exhibited excellent CA inhibitory potency against the four CA isoenzymes as compared to clinically used reference drug acetazolamide (AAZ). Some compounds bearing bulkier group at C-5′ position of 1,2,3-triazoles ring were weaker inhibitors of hCA I. Inhibition assay against hCA II indicates, that several derivatives exhibited upto 27-fold more effective inhibitory activity compared to AAZ. Five of the assayed compounds displayed low nanomolar potency (K_i ≤ 10 nM) against hCA IX, whereas five compounds were found to be endowed with excellent inhibitory potencies (K_i ≤ 5 nM) against hCA XII. The biological activity profile presented herein will be useful for designing new leads and provide candidates for preclinical investigations.     

Synthesis,DNA and protein interactions and human topoisomerase inhibition of novel Spiroacridine derivatives

Nine new spiroacridine derivatives were synthetized by introducing cyano-N-acylhydrazone group between the acridine and phenyl-substituted rings followed by spontaneous cyclization. The new compounds were assayed for their DNA binding properties, human topoisomerase IIα inhibition and bovine serum albumin (BSA) interaction. Besides, docking analysis were performed in order to better understanding the biomolecule-compounds interactions. All compounds interacted with BSA which was demonstrated by the fluorescence suppression constant of 10⁴?M^?1. Compounds with chloro and NO₂ substituents at that para-position on phenyl ring demonstrated the best results for BSA interaction. DNA binding constant determined by UV–vis data demonstrated high values for AMTAC-11 and AMTAC-14, 1.1?×?10⁸?M^?1 and 4.8?×?10⁶?M^?1, respectively, and all others presented constant values of 10⁵?M^?1. AMTAC-06 with chloro at para-position on phenyl ring presented a topoisomerase II inhibition of 84.34% in comparison to the positive controls used. Docking studies indicated that AMTAC-06 is able to intercalate the DNA base pairs at topoisomerase IIα active site, preventing DNA connection after break, in a process known as poisoning. Topoisomerase enzyme inhibition result was correlated to BSA interaction profile, since AMTAC-06 showed the best results in both analysis. The findings obtained here proved that methoxy or chloro substitution on phenyl ring at para-position is fundamental for in vitro activity of new spiroacridine derivatives, and indicates that AMTAC-06 is a promising entity and should serve as a lead compound in the development of new DNA and protein binders, as well as human topoisomerase II inhibitors.     

Circular dichroic studies on Cu(II) interactions with a protamine,scylliorhinine Z3

The interaction of Cu(II) with the protamine scylliorhinine Z₃ was studied by means of CD measurements. At a 1:1 molar ratio, three complexes are formed. (1) In the pH range 5–6.5, the results suggest the formation of a five-membered chelate ring through the coordination of two nitrogen atoms, the N-terminal and the contiguous peptide nitrogen. (2) At pH ≥ 6.4, there is involvement of the lateral NH₂ group of Arg; at pH 6.5–8, the formation of a 3N cupric complex is strongly suggested. (3) At pH ≥ 8, results indicate the formation of a 4N complex as a major species in Cu(II)-Z₃ solution. The transformation from a 2N to a 3N complex, and from a 3N to a 4N complex was followed with the help of the σ(αNH₂) → Cu(II) charge-transfer dichroic band transitions. At Cu(II):Z₃ molar ratios ≥ 2 and at pH > 8, a new dichroic band appears, indicating the involvement of the tyrosine residue side chain in metal-ion complexation.     

Fe(II)/α-Ketoglutarate-Dependent Hydroxylases and Related Enzymes

Fe(II)/α-ketoglutarate (αKG)-dependent hydroxylases catalyze an amazing diversity of reactions that result in protein side-chain modifications, repair of alkylated DNA/RNA, biosynthesis of antibiotics and plant products, metabolism related to lipids, and biodegradation of a variety of compounds. These enzymes possess a β-strand “jellyroll” structural fold that contains three metal-binding ligands found in a His¹-X-Asp/Glu-X_n-His² motif. The cosubstrate, αKG, chelates Fe(II) using its C-2 keto group (binding opposite the Asp/Glu residue) and C-1 carboxylate (coordinating opposite either His¹ or His²). Oxidative decomposition of αKG forms CO₂ plus succinate and leads to the generation of an Fe(IV)-oxo or other activated oxygen species that hydroxylate the primary substrate. The reactive oxygen species displays alternate reactivity in related enzymes that catalyze desaturations, ring expansions, or ring closures. Other enzymes resemble the Fe(II)/αKG-dependent hydroxylases in terms of protein structure or chemical mechanism but do not utilize αKG as a substrate. This review describes the reactions catalyzed by this superfamily of enzymes, highlights key active site features revealed by structural studies, and summarizes results from spectroscopic and other approaches that provide insights into the chemical mechanisms.     

Synthesis, crystal structure, hydrogen bonding and spectroscopy of Co, Mn and Ni oxalate complexes with the ligand (N,N′-bis(2-pyridylmethyl)-1,3-propanediamine)

Three new compounds are reported with the tetradentate ligand (N,N′-bis(2-Pyridylmethyl)-1,3-propanediamine) (abbreviated as pypn), two mononuclear compounds i.e. [Co(pypn)(C₂O₄)](ClO₄) (1), [Mn(pypn)(C₂O₄)](ClO₄) (2) and one dinuclear compound [Ni₂(pypn)₂(C₂O₄)](ClO₄)₂(C₂H₆O)_1/4(H₂O) (3). In the Co(III) and Mn(II) complexes the oxalate behaves as bidentate ligand, chelating the metal in the O,O′ mode, whereas in the Ni(II) compound the oxalate behaves as tetradentate ligand binding each Ni(II) ion by two oxygen atoms and bridging the two metallic centers.The synthesis, X-ray crystal structure of all three compounds and their spectroscopic properties are presented in detail. The geometry around the Co³⁺, Mn³⁺, Ni²⁺ ions is essentially octahedrally based, while the stabilization of the crystal lattice in all cases is maintained by interesting hydrogen bond systems.