Sofija P. Sovilj

SYNTHESIS, CHARACTERIZATION, STRUCTURE AND POSSIBLE CATALYTIC PROPERTIES OF CIS-OXALATO(1,4,8,11-TETRAAZACYCLOTETRADECANE)COBALT(III) NITRATE

Abstract A new complex of cobalt(III) with 1,4,8,11-tetraazacyclotetradecane (cyclam) and oxalato ion as a bidentate ligand was prepared and characterized by elemental analysis, IR, electronic and 1H NMR spectroscopy and cyclic voltammetry. X-Ray analysis has shown that this compound crystallizes in the orthorhombic system, space group Pccn, with a = 8.583(1), b = 12.854(2), c = 14.944(1)A, V = 1649.3(4) A3, Z = 4, R = 0.512, Rw = 0.545, and has a crystallographic two-fold rotation axis. The complex was identified as cis-oxalato(1,4,8,11-tetraazacyclotetradecane)cobalt(III) nitrate, [Co(ox)cyclam]NO3 (oxH2 = oxalic acid), and it can be described in terms of a cis octahedral geometry with a folded cyclam configuration around the cobalt atom with the oxalato ion occupying the remaining two sites. Cyclic voltammetric data suggest a large stability for this compound, as well as its possible catalytic effect on electrochemical CO2 reduction.

MIXED-LIGAND COMPLEXES OF COBALT(III) WITH DITHIOCARBAMATES AND A CYCLIC TETRADENTATE SECONDARY AMINE

Abstract 4-Morpholine-, piperidine-, 4-piperazine- and N-methyl- piperazine-dithiocarbamate complexes of Cobalt (III) with 1, 4, 8, 11-tetraazacyclotetradecane, of general formula [Co(Rdtc)cyclam] (C104)2, have been prepared and have been characterized. The complexes adopt cis-octahedral geometry with folded macrocyclic ligand and with the dithiocarbamate bound as a bidentate. trans-influence of the dithiocarbamate ligands was studied by NMR spectroscopy and established the order piperidine-dtc > 4-morpholine-dtc > N-methyl-piperazine-dtc.

Synthesis, Crystal Structure, Magnetic Properties and Cyclic Voltammetry of the Unsymmetric (μt-Oxalato)-[N, N′, N″, N″′-Tetrakis-(2-Pyrii)Ylmethyl)-1, 4, 8, 11-Tetraazacyclotetfw-Decane]Dicobalt(II) Pekchlokate Trihydkate

Abstract A new dinuclear cobalt(II) complex, [Co2(ox)tpmc](ClO4)2 3H2O, (tpmc = N, N′, N″, N″′-tetrakis(2-pyridylmethyl)-1, 4, 8, 11-tetraazacyclotetradecane, ox2 -oxalate ion), has been synthesized and its crystal structure solved by single crystal X-ray diffraction studies. It crystallizes in the monoclinic system, space group P21, with a = 97558(8) A, b = 21.455(2) A, c - 21.241(2) A, β=100.069(8)°, V=4391.0(8) A3, Z =4,R = 0.083, Rw = 0.086. Its structure consists of two dinuclear, crystallographically unique molecules in which the oxalate ion bridges two cobalt(II) ions unsymmetrically. E:ach cobalt is hexa-coordinated with four macrocyclic nitrogens and two oxygens in an octahedral arrangement of an “em” coordination of a macrocyclic ligand. The third oxygen is simultaneously bonded to both cobalt ions and the last one remains uncoordinated, which is the unique way of oxalato ion coordination. Intramolecular antiferromagnetic coupling between the two cobalt(II) ions is observed and yielded J = -9.3 ...

Preparation, characterization and redox properties of o,o′‐geometrical isomers of μ‐α and μ‐β‐aminoisobuty‐rato co(ii) complexes with n,n′,n′,n‴‐tetrakis(2‐pyridylmethyl)‐1,4,8,11‐tetraazacyclotetradecane

Abstract Two new dinuclear cobalt(II) complexes which, besides macrocyclic ligand N′,N′,N″,N‴-tetrakis (2-pyridylmethyl)-l,4,8,11-tetraazacyclotetradecane (tpmc) contain α- or β-aminoisobutyrato ions (α-aibu − and β-aibu −, respectively) were synthesized. The complexes having general formula [Co2(aibu)tpmc](CIO4)3 were characterized by elemental analysis, electronic and 1R spectroscopy, magnetic measurements and cyclic voltammetry. It was assumed that in both complexes an exo coordination of the macrocyclic ligand is achieved. Cobalt(II) ions are bridged with O,O′-aminoisobutyrato ligand. Both complexes are stable against air oxidation, whereas the oxidation of the complex containing the α-aibu− ion by hydrogen-peroxide gave the coresponding mixed-valence Co11/Co111 complex. The complexes are also electrochemically stable in the potential range from-0,6V to 0,4V vs SCE.

Dinuclear copper(II) octaazamacrocyclic complex in a PVC coated GCE and graphite as a voltammetric sensor for determination of gallic acid and antioxidant capacity of wine samples

A novel efficient differential pulse voltammetric (DPV) method for determination gallic acid (GA) was developed by using an electrochemical sensor based on [Cu2tpmc](ClO4)4 immobilized in PVC matrix and coated on graphite (CGE) or classy carbon rod (CGCE). The proposed method is based on the gallic acid oxidation process at formed [Cu2tpmcGA](3+) complex at the electrode surface. The complexation was explored by molecular modeling and DFT calculations. Voltammograms for both sensors, recorded in a HNO3 as a supporting electrolyte at pH 2 and measured in 2.5×10(-7) to 1.0×10(-4) M of GA, resulted with two linear calibration curves (for higher and lower GA concentration range). The detection limit at CGE was 1.48×10(-7) M, while at CGCE was 4.6×10(-6) M. CGE was successfully applied for the determination of the antioxidant capacity based on GA equivalents for white, rosé and red wine samples.

Cobalt(Iii) Complexes with a Tetraaza Macrocyclic Ligand and Some Heterocyclic Dithiocarbamates

Abstract Four new cobalt(III) complexes of the general formula [Co(Rdtc)cyclam](ClO4)2, where cyclam and Rdtc refer to 1, 4, 8, 11-tetraazacyclotetradecane and 2-, 3-, 4-methylpiperidine (2-, 3-, 4-Mepipdtc−) or 4-thiomorpholine (Timdtc) dithiocarbamates, respectively, have been prepared. Elemental and thermal analyses, VIS, IR and 1H and 13C NMR spectroscopy have been used to characterized them. In the complexes, cobalt is hexa-coordinated in an octahedral geometry of a folded macrocyclic ligand and dithiocarbamates are bound as bidentates. As regards to the influence of the position of the methyl group on the piperidine ring, the v(C[dbnd]N) and v(C[dbnd]S) values increase in the order 2-Mepipdtc < 3-Mepipdtc < 4-Mepipdtc. Furthermore, the position of the methyl substituent also influences the thermal stability of the complexes and the order of stability decreases in the opposite order.

MIXED DINUCLEAR CO(II) COMPLEXES WITH N, N', N , N '-TETRAKIS-(2-PYRIDYLMETHYL)-1,4,8,11-TETRAAZACYCLOTETRADECANE AND ALPHA - AND BETA -AMINOCARBOXYLA TO LIGANDS

Abstract Four new mixed complexes of Co(II) with N,N′ N″,N′″-tetrakis(2-pyridylmethyl)-1, 4, 8, 11-tetraazacyclotetradecane (tpmc) and bridged α- or β-aminocarboxylato ligands of general formula [Co2(Y)tpmc](C1O4)3 zH2O where Y = glycinato, S-alaninato, S-aminobutyrato, β-aminobutyrato ion, and z = 0, 0.5 or 1 were isolated. The complexes were characterised by elemental analysis, electronic and IR spectroscopy, magnetic measurements and cyclic voltam-metry. A structure with μ-O, O′-coordination of the aminocarboxylato ligand, and exo coordination of Co(II) ions and tpmc is proposed. The complexes exhibit different electrochemical activities; glycinato and S-alaninato complexes are electrochemically active, whereas S-aminobutyrato and β-aminobutyrato complexes are electrochemically inactive under the given conditions.

New ruthenium(II) complexes with N-alkylphenothiazines: Synthesis, structure, in vivo activity as free radical scavengers and in vitro cytotoxicity

Three new complexes of the general formula L[RuCl(3)(DMSO)(3)] (1-3), where L = chlorpromazine hydrochloride, trifluoroperazine dihydrochloride or thioridazine hydrochloride, were prepared and characterized by elemental analysis and spectroscopic methods (FT-IR, UV-Vis, (1)H NMR and (13)C NMR). In addition, the crystal structure of the complex 2 containing trifluoroperazine dihydrochloride was solved by single crystal X-ray diffraction. The complex crystallizes in the monoclinic system, space group P2(1)/n, with a = 10.4935(7) A, b = 18.6836(12) A, c = 19.9250(13) A, beta = 98.448(2) degrees, V = 3864.0(4) A(3). The structure was refined to the agreement factors of R = 4.79%, R(w) = 11.23%. The effect of three different doses (0.4, 4.5 and 90.4 microM/kg bw) of complex 2 on superoxide dismutase (SOD) and catalase (CAT) activity was investigated under physiological conditions. Influence on nitrite production (NO(2)(-)) and the level of erythrocytes malondialdehyde (MDA) in rats blood was also evaluated. Complex 2 did not affect the CAT enzyme activity in vivo and did not cause the hydroxyl radicals production. In the 0.4 and 4.5 microM/kg bw doses it showed almost the same or lower SOD activity and nitrite levels, while the dose of 90.4 microM/kg bw significantly increased these parameters. Finally, the cytotoxicity of complexes were assayed in four human carcinoma cell lines MCF-7, MDA-MB-453 (breast carcinoma), SW-480 (colon adenocarcinoma) and IM9 (myeloma multiple cells). Antiproliferative activity in vitro with low IC(50) during 48 h of treatment was observed.

Biological Activity of Some Cobalt(II) andMolybdenum(VI) Complexes: in vitro Cytotoxicity

Cytotoxicity and cell growth inhibition studies were performed for five distinct cobalt(ll) [Co2(acac)tpmc](ClO4)3, [Co2(dibzac)tpmc](ClO4)3, [Co2(hfac)tpmc](CIO4)2, [Co2(tmhd)tpmc](CIO4)3 and [Co2(ox)tpmc](CIO4)2.3H20 and five molybdenum(Vl) complexes, [MoO2(pipdtc)2], [MoO2(morphdtc)], [MoO2(timdtc)2], [MoO2(pzdtc)2] and [MoO2(N-Mepzdtc)2]. The former were tested in two leukemia cell lines: chronic myelogenic leukemia (K562) and human promyelocytic cell line (U937). They showed to have relatively high toxicity in K562 cells and a relatively low cytotoxicity in U937 cells, as assessed by both MTT and Trypan Blue assays. The five molybdenum complexes were tested in human promyelotic U937 cell line and they showed to have high toxicity.

Electrochemical Examination of Mixed-Ligand Cobalt(III) Complexes with Tetraazamacrocyclic Ligand and Heterocyclic Dithiocarbamates

Electrochemical stability of eight complexes of the general formula [CoIIIRdtc(1–8)cyclam](ClO4)2, where cyclam=1,4,8,11-tetraazacyclotetradecane and Rdtc− (1–8)=4-morpholine (Morphdtc), 4-thiomorpholine (Timdtc), 4-piperazine (Pzdtc), N-methyl piperazine (N-Mepzdtc), piperidine (Pipdtc), 2-, 3- or 4-methylpiperidine (2-, 3- or 4-Mepipdtc) dithiocarbamates, respectively, were studied. The substances were examined in aqueous NaClO4 solution and nonaqueous LiClO4 in CH3CN solution by cyclic voltammetry. In aqueous solution, macrocyclic ligand cyclam is characterized by the anodic peak at 0.95 V. The Rdtc− ligands have two anodic peaks, one in the region 0.25–0.30 V and the other in the 0.78–0.95 V region. Absence of these anodic peaks in the case of the complexes indicates that coordination to cobalt(III) stabilizes both cyclam and Rdtc− ligands, but reversible peaks in the range −0.68 to −0.78 V support the Co(III) redox reaction. In nonaqueous solutions cyclam has one anodic peak at 1.75 V. The ligands with heteroatom in the ring (Morphdtc, Timdtc, Pzdtc, N-Mepzdtc) have two anodic peaks, while the other four ligands (Pipdtc, 2-, 3- and 4-Mepipdtc) have only one anodic peak. In nonaqueous solution again, coordination to Co(III) ion stabilizes the Rdtc− ligands and contrary to aqueous solution no Co(III) redox reaction occurs, indicating a greater stability of the complexes in this media. Finally, the electrochemical results are compared with spectroscopic data obtained previously.