Volume 70, Issue 1

1,10-Phenanthroline-5,6-dione (Phd) complexes of group 3 and lanthanide elements having formulae Ln(hfac) 3 (Phd) (Ln = Y, Eu, Yb; hfac = hexafluoroacetylacetonate) were synthesised and characterised. Complexes of d -block elements of the type [MCl(Phd)( p -cymene)] + (M = Ru, Os) were also prepared. In all these species, coordination of the polydentate ligand occurs by the N -donor moieties, as indicated by DFT calculations. The novel compounds were tested, together with fac -ReBr(Phd)(CO) 3 , as precursors for the preparation of heterobimetallic d / f derivatives. The reaction of the rhenium complex with yttrium or lanthanide anhydrous triflate salts led to the formation of the complexes ReBr(CO) 3 ( N , N′ -Phd- O , O′ )Ln(OTf) 3 (THF) (Ln = Y, Eu, Yb), where the trivalent ions interacted with the quinonoid moiety. The redox properties of the rhenium centre were strongly affected by the coordination of Ln(OTf) 3 , as observed by comparing the cyclic voltammetry measurements carried out on fac -ReBr(Phd)(CO) 3 and on ReBr(CO) 3 ( N , N′ -Phd- O , O′ )Y(OTf) 3 .

Yttrium and lanthanum amido-complexes with bis(pyrazol-1-yl)acetates in their coordination spheres were studied as the catalysts in ɛ -caprolactone and lactide ring-opening polymerisation. A high molecular mass poly( ɛ -caprolactone) (PCL) was obtained in almost quantitative yield under mild conditions. rac -Lactide polymerisations were less efficient and required quite harsh experimental conditions to obtain atactic PLA samples with moderate yields. The average chain-length of PCL was dependent upon the choice of the metal centre and the presence of substituents on the pyrazole rings of the ancillary ligand. The ground-state geometries of the complexes and the first stages of ɛ -caprolactone polymerisation were computationally modelled by means of DFT calculations.

EPR spectroscopy is a well suited analytical tool to monitor the electronic situation around paramagnetic metal centres as copper(II) and therefore the structural influences on the paramagnetic ion. 1,2-Dithiosquaratometalates are available by direct synthesis from metal salts with dipotassium-1,2-dithiosquarate and the appropriate counter cations. Synthesis and characterisation of bis(benzyltributylammonium)1,2-dithiosquaratonickelate(II), (BzlBu 3 N) 2 [Ni(dtsq) 2 ], and bis(benzyltributylammonium)1,2-dithiosquaratocuprate(II), (BzlBu 3 N) 2 [Cu(dtsq) 2 ], with benzyltributylammonium as the counter ion is reported and the X-ray structures of two complexes, (BzlBu 3 N) 2 [Ni(dtsq) 2 ] and (BzlBu 3 N) 2 [Cu(dtsq) 2 ], are presented. Both complexes, crystallising in the monoclinic space group P 2 1 /c, are isostructural with only small differences in the coordination sphere due to the different metal ions. The diamagnetic nickel complex is therefore well suited as a host lattice for the paramagnetic Cu(II) complex to measure EPR for additional structural information.

A critical review of zeolites and their use in practical applications is presented. Specifically-considered are their role as media for selective light-induced oxidations using molecular O 2 , and the relationship between this phenomenon and the surface electric fields that exist in zeolites. Methods for the determination of the strength of zeolite surface fields are discussed using sorbed molecules such as CO (with IR detection), spin-probes, di- tert -butyl nitroxide, and NO (measured using EPR spectroscopy). Relationship between the surface fields and molecular reorientation energetics for free radicals sorbed in zeolites, obtained using muonium as a spin-label, is explored. Finally, results obtained from exposing the naturally occurring zeolite, clinoptilolite, to high energy electrons as a means for activating materials toward selective removal of radioactive caesium and strontium cations from wastewaters of nuclear power plants are presented.

Cobalt(III) complexes with N -salicylidene-2-hydroxy-5-bromobenzylamine (H 2 sbba) and N -salicylidene-2-hydroxy-5-chlorobenzylamine (H 2 scba), [ n -(C 4 H 9 ) 4 N][Co(sbba) 2 ] ( I ) and [ n -(C 4 H 9 ) 4 N][Co(scba) 2 ] ( II ), were synthesized. The crystal structure of II was determined by the single-crystal X-ray diffraction method at 90 K confirming its crystallization in the monoclinic space group P 2 1 / n with a = 11.729(2) Å, b = 16.901(3) Å, c = 21.483(4) Å, β = 98.840(4) ˚ , V = 4208.2(14) Å 3 , D x = 1.295 g cm −3 , and Z = 4. The R 1 [ I > 2 σ ( I )] and wR 2 (all data) values of 0.0664 and 0.1920, respectively, for all 9521 independent reflections. The compound is composed of a tetra( n -butyl)ammonium cation and an octahedral cobalt(III) complex anion with two scba 2− ligands in a meridional fashion. The electronic spectral features of I and II are consistent with the octahedral cobalt(III) ion with an N 2 O 4 donor set.

A nickel(II) complex, [Ni(taetacn)](ClO 4 ) 2 · H 2 O, where taetacn = 1,4,7-tris(2-aminoethyl)-1,4,7-triazacyclononane was synthesized. The crystal structure was determined by the single-crystal X-ray diffraction method at 293 K. The complex crystallizes in the orthorhombic space group Pna 2 1 with a = 16.004(2) Å, b = 10.186(1) Å, c = 13.937(2) Å, V = 2271.9(5) Å 3 , D x = 1.56 g cm −3 , D m = 1.59 g cm −3 (floatation method), and Z = 4. The R 1 [ I > 2 σ ( I )] and wR 2 (all data) values are 0.0636 and 0.1672, respectively, for all 4845 independent reflections. The compound is composed of octahedral nickel(II) cation with three 2-aminoethyl pendant groups of taetacn, tetrahedral ClO4−${\rm{ClO}}_4^ - $ anion, and a water molecule of crystallization. Electronic spectra are consistent with the octahedral geometry. Temperature dependence of the magnetic susceptibility (4.5–300 K) can be interpreted considering the zero-field splitting of the nickel(II) ion ( g = 2.14, D = 3.72 cm −1 , and Nα = 300 × 10 −6 cm 3 mol −1 ). Cyclic voltammetry in DMF showed quasi-reversible and irreversible oxidation waves ( E pa = 0.54 V, E pc = 0.45 V; E pa = 1.16 V, E pc = 0.71 V vs. Ag/Ag + ).

Investigation of salicylatocopper complexes in the presence of a nitrogen donor ligand is a growing research area due to the interesting mimetic activities of such complexes. Here, three X-salicylatocopper (where X = 3-methyl, or 4-methoxy) complexes with three different N -donor ligands, [Cu( μ -menia)(3-Mesal) 2 (menia)(H 2 O)] 2 ( I ), Cu(3-Mesal) 2 (denia) 2 (H 2 O) 2 ( II ), Cu(4-MeOsal) 2 (2-pyme) 2 ( III ), are presented (where 3-Mesal = 3-methysalicylate, 4-MeOsal = 4-methoxysalicylate, menia = N -methylnicotinamide, 2-pyme = 2-pyridylmethanol). The complexes were characterized by elemental analysis, IR and UV-VIS spectrophotometry. Cyclic voltammetry and the superoxide dismutase activity of the prepared complexes in solution were measured and the complexes were characterized by means of the inhibition concentration IC 50 . In addition, the superoxide dismutase (SOD) activity of these complexes was compared with those of the parent ligand copper acetate, native SOD enzyme, and the related copper complexes containing non-steroidal anti-inflammatory drugs. The resulting SOD activity was correlated to the composition, structure and redox stability of the prepared complexes. The best value of the inhibition concentration was found for complex I (IC 50 = 2.24 μM), which classifies this complex into a group of good superoxide scavengers.

Six copper(II) oxalate complexes, namely {K 2 [Cu(ox) 2 ]} n ( 1 ), {(Hiz) 2 [Cu(ox) 2 ]} n ( 2 ), {[Cu(ox) (N-Bzliz) 2 ]} n ( 3 ), (HMeiz) 2 [Cu(ox) 2 ] ( 4 ), {[Cu(ox)(Meiz) 2 ]} n ( 5 ), and [Cu(Hox) 2 (H 2 O) 2 ](N-Bzliz) ( 6 ) where ox = oxalate ion, iz = imidazole, N-Bzliz = N -benzylimidazole, Meiz = 2-methylimidazole, were synthesised and characterised by single crystal X-ray diffraction (complexes 1 – 5 ) or powder X-ray diffraction (compound 6 ). The three-dimensional crystal packing structures of 2 , 4 , and 5 are consolidated by intermolecular hydrogen bonds linking the oxygen atom of the oxalate group and the amine or imine group of the imidazole-based part into chains. The molecules of complex 6 are held together by intermolecular hydrogen bonds between the oxygen atoms of the oxalate group and coordinated water molecules.

Fundamentals of copper catalyzed atom transfer radical addition (ATRA) and mechanistically similar polymerization (ATRP) were discussed. Special emphasis was placed on structural characterization and electrochemical properties of copper complexes. Recent advances in the development of highly active copper complexes for both processes were also reviewed. It was found that electron-donating groups (methoxy and methyl in the 4 and 3,5 positions, respectively) of the pyridine rings in tris(2-pyridylmethyl)amine (TPMA) ligand, significantly increase the catalytic activity in copper mediated ATRA/ATRP.

Cisplatin is an anticancer drug widely used in the treatment of a wide range of solid tumours (head and neck, lung, bladder etc.), testicular and ovarian cancers. Because of its severe toxicity profile and spontaneous development of drug resistance in tumours, a number of Pt(II) complexes have been synthesised and tested for anti-tumour activity. Some of the investigations have focused on using ligands bearing donor atoms other than N (e.g., S, P, O). Two new mixed Pt(II)complexes of the general formula cis -[Pt(NH3)LCl2 ] where L is 3-thiolanespiro-5′ -hydantoin and 4-thio-1 H -tetrahydropyranspiro-5′-hydantoin were synthesised. The complexes were studied by elemental analysis, melting points, IR and 1 H NMR spectra. The hybrid DFT calculations were used for optimisation of the structure geometries of the ligands III , IV and their Pt(II) complexes V and VI . The structural parameters so calculated, such as bond lengths and angles, are in good agreement with the experimental data for similar hydantoins and their platinum complexes. The results showed that the geometries of complexes V and VI are plane square and the bounding of ligands III and IV with platinum ions is effected by the sulphur atom from the cyclic ring. The complexes thus obtained were chemically examined in comparison with previously synthesised and published complexes of the general formula cis -[PtL2 Cl2] ( VII and VIII ) with the same ligands. The new compounds V and VI , as well as the previously investigated complexes ( VII and VIII ), were analysed for cytotoxicity in vitro on SKW-3 and HL-60 human tumour cell lines. The results showed that all the complexes exerted concentration-dependent anti-proliferative activity. Q c 2015 Institute of Chemistry, Slovak Academy of Sciences

The influence of Ca 2+ -, Cu 2+ - and Fe 3+ -exchanged montmorillonite (MMT) on the type of interaction with aniline in the interlayer space of MMT has been studied by means of X-ray powder diffraction and infrared spectra. Results of X-ray diffraction showed that aniline was successfully intercalated into the interlayer space of MMT. Based on IR spectra evaluation, aniline was indirectly coordinated through a water-bridge in Ca 2+ - and Fe 3+ -MMT and it was indirectly coordinated through a water-bridge as well as protonated in Cu 2+ -MMT (the spectrum of protonated aniline showed deformation and changes in the NH3+${\rm{NH}}_3^ + $ absorption at approximately 1521 cm −1 ). It is important to point out that Cu 2+ -MMT indirect coordination and protonation occur simultaneously.

Nicotinamide was employed as a supramolecular reagent in the synthesis of six new copper(II) bromo-, iodo-, fluoro- and dibromobenzoate complexes. Structures of [Cu(2-Brbz) 2 (nia) 2 (H 2 O) 2 ] ( I ), [Cu(2-Ibz) 2 (nia) 2 (H 2 O) 2 ] ( II ), [Cu(2-Fbz) 2 (nia) 2 (H 2O ) 2 ] ( III ), [Cu(4-Brbz) 2 (nia) 2 (H 2 O) 2 ]( IV ), [Cu(3,5-Br2 bz) 2 (nia) 2 (H 2 O) 2 ] ( V ), [Cu(F-Fbz) 2 (nia) 2 (H 2 O)] · H 2 O ( VI ) (nia = nicotinamide, 2-Brbz = 2-bromobenzoate, 4-Brbz = 4-bromobenzoate, 3,5-Br 2 bz = 3,5-dibromobenzoate, 2-Ibz = 2-iodobenzoate, 2-Fbz = 2-fluorobenzoate, 4-Fbz = 4-fluorobenzoate) were determined using X-ray analysis. Compound [Cu(2-Brbz) 2 (nia) 2 ] · 2H 2 O ( VII ) was prepared by a new method and also characterized by X-ray powder diffraction and EPR spectroscopy. Compounds I – V are monomeric complexes with a square-bipyramidal coordination sphere around the Cu 2+ ion. Complex VI is monomeric with coordination environment around the Cu2+ ion of a tetragonal-pyramid. Complexes I and VII present examples of coordination isomerism. Molecules of all compounds are connected by N—H· · ·O and O—H·· ·O hydrogen bonds from the NH2 groups of nicotinamide and water molecules which create supramolecular hydrogen-bonding-coordination chains and networks. · c 2015 Institute of Chemistry, Slovak Academy of Sciences

Synthesis and characterization of eight new complexes of various structural types are reported. With 5-nitro-2-furancarboxylic acid (5-NO 2 -2-fucH), two monomeric complexes, [Cu(5-NO 2 -2-fuc) 2 (H 2 O) 2 ] ( II ) and [Cu(5-NO 2 -2-fuc) 2 (H 2 O) 4 ] ( III ), as well as a dimeric complex with ethylnicotinate (Etnic), [Cu(5-NO 2 -2-fuc) 2 (Etnic) 2 ] 2 ( V ), were prepared. With other acids: 2,5-dimethyl-3-furancarboxylic acid (2,5-Me 2 -3-fucH), 2-thiophencarboxylic acid (2-tpcH), 3-methyl-2-thiophencarboxylic acid (3-Me-2-tpcH) or 5-methyl-2-thiophencarboxylic acid (5-Me-2-tpcH), only dimeric complexes [Cu(2,5-Me 2 -3-fuc) 2 (H 2 O)] 2 ( I ), [Cu(2,5-Me 2 -3-fuc) 2 (Etnic)] 2 ( IV ), [Cu(2-tpc) 2 (Etnic)] 2 ( VI ), [Cu(3-Me-2-tpc)2(Etnic)] 2 ( VII ) and Cu(5-Me-2-tpc) 2 (Etnic)] 2 ( VIII ) have been synthesised. Characterizations of the complexes were based on elemental analysis and infrared, electronic, EPR and magnetic measurements. Moreover, complexes III , V , VII and VIII were also studied by X-ray structural analysis. Two structural types of dimeric complexes were observed differing in the number of carboxylate bridges. Most of the dinuclear complexes exhibit the common “paddle-wheel” structural motif while the molecular structure of V contains two pentacoordinated copper(II) ions bridged by two carboxylate groups of two 5-nitro-2-furancarboxylate ligands resulting in the intramolecular copper-copper distance of 4.4960(8) Å. Magnetic properties (monomeric EPR signal and isotropic exhchange constant ( J of approximately 0 cm −1 ) of V confirmed a very weak magnetic interaction between copper centres.