cis-[Ru(2,2':6',2' '-terpyridine)(DMSO)Cl(2)]: useful precursor for the synthesis of heteroleptic terpyridine complexes under mild conditions

[Ru(II)(terpy)(DMSO)Cl(2)] complexes were synthesized as a 5/1 mixture of cis and trans isomers, and their reactivities with CO and with substituted 2,2':6',2' '-terpyridine (terpy) moieties have been investigated. The structure of a trans isomer and its CO adduct have been unambiguously assigned by spectroscopy and X-ray diffraction. The [Ru(terpy)(terpy-Br)](2+) complex prepared either from the cis-[Ru(II)(terpy)(DMSO)Cl(2)] or from the cis-[Ru(II)(terpy-Br)(DMSO)Cl(2)] precursor appeared to be reactive in cross-coupling reactions promoted by low-valent palladium(0) and is an attractive target for the stepwise synthesis of polynuclear complexes bearing vacant coordination sites (terpy-Br for 4'-bromo-2,2':6',2' '-terpyridine). Several bipyridine, phenanthroline, and bipyrimidine complexes were prepared this way and their optical and redox properties determined and discussed.     

Synthesis and properties of the elusive ruthenium(II) complexes of 4'-cyano-2,2':6',2' '-terpyridine

The heteroleptic and homoleptic ruthenium(II) complexes of 4'-cyano-2,2':6',2' '-terpyridine are synthesized by palladium catalyzed cyanation of the corresponding Ru(II) complexes of 4'-chloro-2,2':6',2' '-terpyridine. The introduction of the strongly electron-withdrawing cyano group into the Ru(tpy)(2)(2+) moiety dramatically changes its photophysical and redox properties as well as prolongs its room temperature excited-state lifetime.     

Synthesis, characterization and electrochemistry of 4'-functionalized 2,2':6',2'-terpyridine ruthenium(II) complexes and their biological activity

The synthesis and characterization of Ru(II) terpyridine complexes derived from 4'-functionalized 2,2':6',2'-terpyridine ligands by a multi step procedure have been described. The complexes are redox-active, showing both metal-centred (oxidation) and ligand-centred (reduction) processes. The antibacterial and antifungal activity of the synthesized ruthenium(II) complexes [Ru(attpy)2](PF6)2 (attpy = 4'-(4-acryloyloxymethylphenyl)-2,2':6',2'-terpyridine); [Ru(mttpy)2](PF6)2 (mttpy = 4'-(4-methacryloyloxymethylphenyl)-2,2':6',2'- terpyridine); [Ru(mttpy)(MeOPhttpy)](PF6)2 (MeOPhttpy = 4'-(4-methoxyphenyl)-2,2':6',2'-terpyridine); and [Ru(mttpy)(ttpy)](PF6)2 (ttpy = 4'-(4-methylphenyl)-2,2':6',2'-terpyridine) were tested against four human pathogens (Proteus vulgaris, Proteus mirabilis, Pseudomonas aeruginosa and Escherichia coli) and five plant pathogens (Curvularia lunata, Fusarium oxysporum, Fusarium udum, Macrophomina phaseolina and Rhizoctonia solani) by the well diffusion method and MIC values of the complexes are reported. A biological study of the complexes indicated that the complexes [Ru(mttpy)2](PF6)2 and [Ru(mttpy)(MeOPhttpy)](PF6)2 exhibit very good activity against most of the test pathogens and their activity is better than those of some of the commercially available antibiotics like tetracycline and the fungicide carbendazim.     

Structural development of free or coordinated 4'-(4-pyridyl)-2,2':6',2'-terpyridine ligands through N-alkylation: new strategies for metallamacrocycle formation

A series of N-alkylated derivatives of [Ru(pytpy)(2)]2+ (pytpy=4'-(4-pyridyl)-2,2':6',2'-terpyridine) has been synthesised and characterised. These include both model and functionalised complexes that complement previously reported iron(II) analogues. Reaction of [Ru(pytpy)(2)]2+ with bis[4-(bromomethyl)phenyl]methane leads to the formation of a [2+2] ruthenamacrocycle. Related ferramacrocycles could not be accessed by this route, and instead were prepared in two steps by first reacting bis[4-(bromomethyl)phenyl]methane or 4,4'-bis(bromomethyl)biphenyl with two equivalents of pytpy, and then treating the resulting bis(N-alkylated) product with iron(II) salts.     

Synthesis and computational studies of Mg complexes supported by 2,2':6,2'-terpyridine ligands

The reactions of the substituted 2,2':6,2'-terpyridine ligands, 4'-mesityl-2,2':6',2'-terpyridine (mesitylterpy) (1a), 4,4',4'-tri-tert-butyl-2,2':6',2'-terpyridine (tri-(t)Buterpy) (1b) and 4'-phenyl-2,2':6',2'-terpyridine (phenylterpy) (1c) with Grignard reagents were investigated. When half an equivalent of mesitylterpy or tri-(t)Buterpy were treated with MeMgBr in diethyl ether, the only products were (R-terpy)MgBr(2) (R = mesityl (5a), or tri-(t)Bu (5b)) and Me(2)Mg and a similar reaction was observed in THF. Compounds 5a and 5b were characterized by X-ray crystallography. Changing the Grignard reagent to PhMgBr also generated 5a and 5b along with Ph(2)Mg, while the reaction between MeMgCl or PhMgCl and 1a or 1b generated (R-terpy)MgCl(2) (R = mesityl (6a), or tri-(t)Bu (6b)) and either Me(2)Mg or Ph(2)Mg, respectively. The products from reactions between phenylterpy (1c) and Grignard reagents were highly insoluble and could not be fully characterized but appeared to be the same as those from reactions with 1a and 1b. In contrast to other studies using tridentate nitrogen ligands, which formed either mixed halide alkyl species or dihalide and bis(alkyl) species depending on whether the Grignard reagent was reacted with the ligand in diethyl ether or THF, the formation of mixed halide, alkyl complexes of the type (R-terpy)MgR'X (R' = Me or Ph; X = Cl or Br) or dialkyl species such as (R-terpy)MgR'(2) (R' = Me or Ph) was not observed here, regardless of the reaction conditions. DFT studies were performed to complement the experimental studies. The experimental results could not be accurately reproduced unless π-stacking effects associated with free terpyridine were included in the model. When these effects were included, the calculations were consistent with the experimental results which indicated that the formation of the terpy Mg dihalide species and R'(2)Mg (R' = Me or Ph) is thermodynamically preferred over the formation of mixed alkyl halide Mg species. This is proposed to be due to the increased steric bulk of the terpy ligand in the coordination plane, compared with other tridentate nitrogen donors.     

Expanded ligands: bis(2,2':6',2'-terpyridine carboxylic acid)ruthenium(ii) complexes as metallosupramolecular analogues of dicarboxylic acids

Ligands in which multiple metal-binding domains are linked by a metal-containing moiety rather than a conventional organic group are described as "expanded ligands". The use of 4,4'-difunctionalised {Ru(tpy)(2)} units provides a linear spacer between metal-binding domains and we have extended this motif to expanded ligands containing two carboxylic acid metal-binding domains. In this paper, we describe the synthesis and structural characterisation of ruthenium(ii) complexes of 2,2':6',2'-terpyridine-4'-carboxylic acid and 4'-carboxyphenyl-2,2':6',2'-terpyridine. The ability of the ruthenium(ii) centre to charge compensate deprotonation of the carboxylic acid leads to Zwitterionic complexes and three representative compounds have been structurally characterised.     

Ruthenium(II) complexes with improved photophysical properties based on planar 4'-(2-pyrimidinyl)-2,2':6',2' '-terpyridine ligands

A series of new tridentate polypyridine ligands, made of terpyridine chelating subunits connected to various substituted 2-pyrimidinyl groups, and their homoleptic and heteroleptic Ru(II) complexes have been prepared and characterized. The new metal complexes have general formulas [(R-pm-tpy)Ru(tpy)]2+ and [Ru(tpy-pm-R)2]2+ (tpy = 2,2':6',2' '-terpyridine; R-pm-tpy = 4'-(2-pyrimidinyl)-2,2':6',2' '-terpyridine with R = H, methyl, phenyl, perfluorophenyl, chloride, and cyanide). Two of the new metal complexes have also been characterized by X-ray analysis. In all the R-pm-tpy ligands, the pyrimidinyl and terpyridyl groups are coplanar, allowing an extended delocalization of acceptor orbital of the metal-to-ligand charge-transfer (MLCT) excited state. The absorption spectra, redox behavior, and luminescence properties of the new Ru(II) complexes have been investigated. In particular, the photophysical properties of these species are significantly better compared to those of [Ru(tpy)2]2+ and well comparable with those of the best emitters of Ru(II) polypyridine family containing tridentate ligands. Reasons for the improved photophysical properties lie at the same time in an enhanced MLCT-MC (MC = metal centered) energy gap and in a reduced difference between the minima of the excited and ground states potential energy surfaces. The enhanced MLCT-MC energy gap leads to diminished efficiency of the thermally activated pathway for the radiationless process, whereas the similarity in ground and excited-state geometries causes reduced Franck Condon factors for the direct radiationless decay from the MLCT state to the ground state of the new complexes in comparison with [Ru(tpy)2]2+ and similar species.     

Reversible luminescence switching in a ruthenium(II) bis(2,2':6',2'-terpyridine)-benzoquinone dyad

An electroactive luminescent switch has been synthesized that comprises a hydroquinone-functionalized 2,2':6',2'-terpyridine ligand coordinated to a ruthenium(II) (4'-phenylethynyl-2,2':6',2'-terpyridine) fragment. The assembly is sufficiently rigid that the hydroquinone-chromophore distance is fixed. Excitation of the complex via the characteristic metal-to-ligand charge-transfer (MLCT) absorption band produces an excited triplet state in which the promoted electron is localized on the terpyridine ligand bearing the acetylenic group. The triplet lifetime in butyronitrile solution at room temperature is 46 +/- 3 ns but increases markedly at lower temperature. Oxidation of the hydroquinone to the corresponding benzoquinone switches on an electron-transfer process whereby the MLCT triplet donates an electron to the quinone. This reaction reduces the triplet lifetime to 190 +/- 12 ps and essentially extinguishes emission. The rate of electron transfer depends on temperature in line with classical Marcus theory, allowing calculation of the electronic coupling matrix element and the reorganization energy as being 22 cm(-1) and 0.84 eV, respectively. The switching behavior can be monitored using luminescence spectroelectrochemistry. The on/off level is set by temperature and increases as the temperature is lowered.     

Voltammetry and in situ scanning tunnelling spectroscopy of osmium, iron, and ruthenium complexes of 2,2':6',2'-terpyridine covalently linked to Au(111)-electrodes

We have studied self-assembled molecular monolayers (SAMs) of complexes between Os(II)/(III), Fe(II)/(III), and Ru(II)/(III) and a 2,2',6',2'-terpyridine (terpy) derivative linked to Au(111)-electrode surfaces via a 6-acetylthiohexyloxy substituent at the 4'-position of terpy. The complexes were prepared in situ by first linking the terpy ligand to the surface via the S-atom, followed by addition of suitable metal compounds. The metal-terpy SAMs were studied by cyclic voltammetry (CV), and in situ scanning tunnelling microscopy with full electrochemical potential control of substrate and tip (in situ STM). Sharp CV peaks were observed for the Os- and Fe complexes, with interfacial electrochemical electron transfer rate constants of 6-50 s(-1). Well-defined but significantly broader peaks (up to 300 mV) were observed for the Ru-complex. Addition of 2,2'-bipyridine (bipy) towards completion of the metal coordination spheres induced voltammetric sharpening. In situ STM images of single molecular scale strong structural features were observed for the osmium and iron complexes. As expected from the voltammetric patterns, the surface coverage was by far the highest for the Ru-complex which was therefore selected for scanning tunnelling spectroscopy. These correlations displayed a strong peak around the equilibrium potential with systematic shifts with increasing bias voltage, as expected for a sequential two-step in situ ET mechanism.     

Ligand substituent effect observed for ytterbocene 4'-cyano-2,2':6',2' '-terpyridine

A new N-heterocyclic complex of ytterbocene (Cp(2)Yb(II), Cp = C(5)Me(5)) has been prepared by the addition of 4'-cyano-2,2':6',2' '-terpyridine (tpyCN) to Cp(2)Yb(II)(OEt(2)) in toluene to give a dark blue species designated as Cp(2)Yb(tpyCN). The effect of the electron-withdrawing group (-CN) on the redox potentials of the charge-transfer form of this complex [in which an electron is transferred from the f(14) metal center to the lowest unoccupied (pi) molecular orbital of the tpyCN ligand to give a 4f(13)-pi(1) electronic configuration] has been quantified by cyclic voltammetry. The tpyCN ligand stabilizes this configuration by 60 mV more than that in the unsubstituted tpy ligand complex and by 110 mV more than that in the unsubstituted bpy ligand complex. Magnetic susceptibility measurements corroborate the enhanced stabilization of the 4f(13)-pi(1) configuration by the substituted terpyridyl ligand complex. Furthermore, the temperature dependence of the magnetic data is most consistent with a thermally induced valence tautomeric equilibrium between this paramagnetic 4f(13)-pi(1) form that dominates near room temperature and the diamagnetic 4f(14)-pi(0) form that dominates at low temperature. Differing coordination modes for the tpyCN ligand to the ytterbocene center have also been confirmed by isolation and X-ray crystallographic characterization of complexes binding through either the cyano nitrogen of tpyCN or the three terpyridyl nitrogen atoms of tpyCN.     

A strategy for the synthesis of metal bis(2,2':6',2' '-terpyridine)-terminated molecular dyads having controlled torsion angles at the central biphenyl linker

The synthesis of a series of binuclear complexes comprising bis(2,2':6',2' '-terpyridine)ruthenium(II) and -osmium(II) centers connected via a geometrically constrained 4,4'-biphenyl bridge is described. These compounds have been prepared by a "synthesis-at-metal" approach as well as by the conventional method of synthesizing the ligand and subsequently attaching the metal center. A computational investigation into the behavior of the biphenyl-based bridges has been used to provide lowest-energy conformations and to estimate the degree of internal fluctuation about the mean torsion angle. It is shown that the length of the constraining strap determines both the torsion angle and the internal flexibility, with longer straps twisting the biphenyl group so as to relax stereochemical interactions between the linking oxygen atoms. Longer straps can be formed from poly(ethylene glycol) residues that provide an additional binding site for small cations. Electrospray mass spectrometry carried out on solutions of these crown ether-like bridges confirmed that Li+, Na+, and K+ ions bind in the form of 1:1 complexes. This range of compounds should permit rational examination of how the torsion angle affects the rate of through-bond electron transfer, electron exchange, and charge shift.     

Temperature-induced switching of the mechanism for intramolecular energy transfer in a 2,2':6',2' '-Terpyridine-based Ru(II)-Os(II) trinuclear array

The synthesis and photophysical properties of a linear 2,2':6',2' '-terpyridine-based trinuclear Ru(II)-Os(II) nanometer-sized array are described. This array comprises two bis(2,2':6',2' '-terpyridine) ruthenium(II) terminals connected via alkoxy-strapped 4,4'-diethynylated biphenylene units to a central bis(2,2':6',2' '-terpyridine) osmium(II) core. The mixed-metal linear array was prepared using the "synthesis at metal" approach, and the Ru(II)-Ru(II) separation is ca. 50 A. Energy transfer occurs with high efficiency from the Ru(II) units to the Os(II) center at all temperatures. Forster-type energy transfer prevails in a glassy matrix at very low temperature, but this is augmented by Dexter-type electron exchange at higher temperatures. This latter process, which is weakly activated, involves long-range superexchange interactions between the metal centers. In fluid solution, a strongly activated process provides for fast energy transfer. Here, a charge-transfer (CT) state localized on the bridge is populated as an intermediate species. The CT triplet does not undergo direct charge recombination to form the ground state but transfers energy, possibly via a second CT state, to the Os(II)-based acceptor. The short tethering strap constrains the geometry of the linker, especially in a glassy matrix, such that low-temperature electron exchange occurs across a particular torsion angle of 37 degrees . The probability of triplet energy transfer depends on temperature but always exceeds 75%.     

Electronic structures and absorption spectra of linkage isomers of trithiocyanato (4,4',4' '-tricarboxy-2,2':6,2' '-terpyridine) ruthenium(II) complexes: a DFT study

Black dye (BD), isomer 1 ([Ru(II)(H3-tctpy)(NCS)3](-1), where H3-tctpy = 4,4',4' '-tricarboxy-2,2':6,2' '-terpyridine) is known to be an excellent sensitizer for dye-sensitized solar cells and exhibits a very good near-IR photo response, compared to other ruthenium dyes. Because isothiocyanate is a linear ambidentate ligand, BD has three other linkage isomers, [Ru(H3-tctpy)(NCS)2(SCN)](-1), isomer 2 and 2', and [Ru(H3-tctpy))(SCN)3](-1), isomer 3. In this study, we have calculated the geometry of BD and its isomers by DFT. Further, we have analyzed the bonding in these isomers using NBO methods. TDDFT calculations combined with scalar relativistic zero-order regular approximations (SR-ZORA) have been carried out to simulate the absorption spectra. Calculations have been performed for the isomers both in vacuo and in solvent (ethanol). The inclusion of the solvent is found to be important to obtain spectra in good agreement with the experiment. The first absorption bands are dominated by the metal-to-ligand charge transfer (MLCT) and ligand-to-ligand charge transfer (LLCT).     

Synthesis, luminescence, and electrochemical studies of tris(homoleptic) ruthenium(II) and osmium(II) complexes of 6'-tolyl-2,2':4',2'-terpyridine

The synthesis and photophysical and electrochemical properties of tris(homoleptic) complexes [Ru(tpbpy)3](PF6)2 (1) and [Os(tpbpy)3](PF6)2 (2) (tpbpy = 6'-tolyl-2,2':4',2' '-terpyridine) are reported. The ligand tpbpy is formed as the side product during the synthesis of 4'-tolyl-2,2':6',2' '-terpyridine (ttpy) and characterized by single-crystal X-ray diffraction: monoclinic, P21/c. The tridentate tpbpy coordinates as a bidentate ligand. The complexes 1 and 2 exhibit two intense absorption bands in the UV region (200-350 nm) assignable to the ligand-centered (1LC) pi-pi* transitions. The ruthenium(II) complex exhibits a broad absorption band at 470 nm while the osmium(II) complex exhibits an intense absorption band at 485 nm and a weak band at 659 nm assignable to the MLCT (dpi-pi*) transitions. A red shifting of the dpi-pi* MLCT transition is observed on going from the Ru(II) to the Os(II) complex as expected from the high-lying dpi Os orbitals. These complexes exhibit ligand-sensitized emission at 732 and 736 nm, respectively, upon light excitation onto their MLCT band through excitation of higher energy LC bands at room temperature. The MLCT transitions and the emission maxima of 1 and 2 are substantially red-shifted compared to that of [Ru(bpy)3](PF6)2 and [Os(bpy)3](PF6)2. The emission of both the complexes in the presence of acid is completely quenched indicating that the emission is not due to the protonation of the coordinated ligands. Our results indicate the occurrence of intramolecular energy transfer from the ligand to the metal center. Both the complexes undergo quasi-reversible metal-centered oxidation, and the E1/2 values for the M(II)/M(III) redox couples (0.94 and 0.50 V versus Ag/Ag+ for 1 and 2, respectively) are cathodically shifted with respect to that of [Ru(bpy)3](PF6)2 and [Os(bpy)3](PF6)2 (E1/2 = 1.28 and 1.09 V versus Ag/Ag+, respectively). The tris(homoleptic) Ru(II) and Os(II) complexes 1 and 2 could be used to construct polynuclear complexes by using the modular synthetic approach in coordination compounds by exploiting the coordinating ability of the pyridine substituent. Furthermore, these complexes offer the possibility of studying the influence of electron-withdrawing and electron-donating substituents on the photophysical properties of Ru(II) and Os(II) polypyridine complexes.     

Synthesis and single-crystal X-ray characterization of 4,4"-functionalized 4'-(4-bromophenyl)-2,2':6',2"-terpyridines

To expand the utility of bis(terpyridine) metal connectivity, the selective symmetrical and unsymmetrical 4,4"-functionalization (-CN, -Me, -CO2Me) of 4'-(4-bromophenyl)-2,2':6',2"-terpyridines was achieved using the Kr?hnke synthesis. The final substituted 2,2':6',2"-terpyridines along with their corresponding intermediates, 4a-c, were recrystallized and characterized by 1H NMR and 13C NMR as well as X-ray crystallography; COSY correlations were also conducted to permit definitive proton assignment.     

Synthesis and DNA-binding properties of cationic 2,2':6',2' '-terpyridineplatinum(II) complexes containing 1,2- and 1,7-dicarba-closo-dodecaborane(12)

The first examples of DNA metallointercalators containing a dicarba-closo-dodecaborane(12) (carborane) moiety are presented. Treatment of the labile platinum(II) complex [Pt(OTf)(terpy)](+) (terpy = 2,2':6',2' '-terpyridine) with the 1,2-carborane monothiol derivatives 1-HS(CH(2))(n)-1,2-C(2)B(10)H(11) (n = 0, 1) or the novel 1,7-carborane ligand, 1-HSCH(2)-1,7-C(2)B(10)H(11), affords the stable, brightly colored species [Pt(1-S(CH(2))(n)-1,Z-C(2)B(10)H(11))(terpy)](+) (Z = 2, n = 0, 1; Z = 7, n = 1) in good yield and purity. Preliminary DNA-binding experiments with calf-thymus DNA indicate an intercalative interaction by the platinum(II) complexes at high r(f) values.     

Experimental and theoretical evaluation of the charge distribution over the ruthenium and dioxolene framework of [Ru(OAc)(dioxolene)(terpy)] (terpy = 2,2':6',2' '-terpyridine) depending on the substituents

A series of ruthenium complexes [Ru(OAc)(dioxolene)(terpy)] having various substituents on the dioxolene ligand (dioxolene = 3,5-t-Bu2C6H2O2 (1), 4-t-BuC6H3O2 (2), 4-ClC6H3O2 (3), 3,5-Cl2C6H2O2 (4), Cl4C6O2 (5); terpy = 2,2':6'2' '-terpyridine) were prepared. EPR spectra of these complexes in glassy frozen solutions (CH2Cl2:MeOH = 95:5, v/v) at 20 K showed anisotropic signals with g tensor components 2.242 > g1 > 2.104, 2.097 > g2 > 2.042, and 1.951 > g3 > 1.846. An anisotropic value, Deltag = g1 - g3, and an isotropic g value, g = [(g1(2) + g2(2) + g3(2))/3]1/2, increase in the order 1 < 2 < 3 < 4 < 5. The resonance between the Ru(II)(sq) (sq = semiquinone) and Ru(III)(cat) (cat = catecholato) frameworks shifts to the latter with an increase of the number of electron-withdrawing substituents on the dioxolene ligand. DFT calculations of 1, 2, 3, and 5 also support the increase of the Ru spin density (Ru(III) character) with an increase of the number of Cl atoms on the dioxolene ligand. The singly occupied molecular orbitals (SOMOs) of 1 and 5 are very similar to each other and stretch out the Ru-dioxolene frameworks, whereas the lowest unoccupied molecular orbital (LUMO) of 5 is localized on Ru and two oxygen atoms of dioxolene in comparison with that of 1. Electron-withdrawing groups decrease the energy levels of both the SOMO and LUMO. In other words, an increase in the number of Cl atoms in the dioxolene ligand results in an increase of the positive charge on Ru. Successive shifts in the electronic structure between the Ru(II)(sq) and Ru(III)(cat) frameworks caused by the variation of the substituents are compatible with the experimental data.     

Electrocatalytic properties of guanine, adenine, guanosine-5'-monophosphate, and ssDNA by Fe(II) bis(2,2':6',2'-terpyridine), Fe(II) tris(1,10-phenanthroline), and poly-Fe(II) tris(5-amino-1,10-phenanthroline)

The electrocatalytic oxidations of guanine, adenine, guanosine-5'-monophosphate(GMP) and ssDNA were performed in the presence of Fe(II) bis(2,2':6',2'-terpyridine) and Fe(II) tris(1,10-phenanthroline) complexes as homogeneous catalysts by cyclic voltammetric methods. The Fe(II/III) redox couple of these compounds is responsible for their catalytic properties. The electrocatalytic oxidation current of above substrates were developed from the anodic peak currents of Fe(II) bis(2,2':6',2'-terpyridine) and Fe(II) tris(1,10-phenanthroline) complexes at about +0.93 V and 0.97 V, respectively. The electrocatalytic oxidative properties of guanine by Fe(II) bis(2,2':6',2'-terpyridine) complex was measured by amperometry method using the rotating disk electrodes. Electropolymerization of Fe(II) tris(5-amino-1,10-phenanthroline) complex produced thin polymer films on gold and glassy carbon electrodes. The electrochemical quartz crystal microbalance (EQCM) and cyclic voltammetry were used to study the in situ growth of the polymer. The poly(FeII(5-NH(2)-1,10-phen)(3)) exhibited a good electrocatalytic oxidation towards guanine and also for the mixture of guanine and adenine too.     

Module-based assembly of copper(II) chloranilate compounds: syntheses, crystal structures, and magnetic properties of [[Cu(2)(CA)(terpy)(2)][Cu(CA)(2)]](n)() and [[Cu(2)(CA)(terpy)(2)(dmso)(2)][Cu(CA)(2)(dmso)(2)](EtOH)](n)(H(2)CA = chloranilic acid, terpy = 2,2':6',2' '-terpyridine, dmso = dimethyl sulfoxide)

Two new copper(II) compounds of chloranilate and 2,2':6',2' '-terpyridine have been synthesized, and the structures have been solved by the single-crystal X-ray diffraction method. The crystal structure of [[Cu(2)(CA)(terpy)(2)][Cu(CA)(2)]](n)(1), where H(2)CA = chloranilic acid and terpy = 2,2':6',2' '-terpyridine, consists of two modules, the dimer unit [Cu(2)(CA)(terpy)(2)](2+) and the anionic mononuclear unit [Cu(CA)(2)](2)(-), forming an alternated chain. The chain is stabilized by semicoordinating and additional but efficient secondary bonding interactions. The crystal structure of [[Cu(2)(CA)(terpy)(2)(dmso)(2)][Cu(CA)(2)(dmso)(2)](EtOH)](n)(2), where dmso = dimethyl sulfoxide, consists of solvent molecules and two discrete modules, the dimer unit [Cu(2)(CA)(terpy)(2)(dmso)(2)](2+) and the anionic mononuclear unit [Cu(CA)(2)(dmso)(2)](2)(-). The dimer units form a layer by secondary bonding interactions, and the monomer units and ethanol molecules are introduced between the layers. The magnetic properties of 1 and 2 have been investigated in the temperature range 2.0-300 K. A weak ferromagnetic interaction was observed in 1, J(a) = 2.36 cm(-)(1) and zJ(b) = -0.68 cm(-)(1) while no exchange coupling was observed in 2.     

Chain-like and dinuclear coordination polymers in lanthanide (Nd, Eu) oxochloride complexes with 2,2':6',2'-terpyridine: synthesis, XRD structure and magnetic properties

The solvothermal reactions (at 180 °C for 48 h) of a mixture of lanthanide chlorides (Nd, Eu) with the tridendate heterocyclic nitrogen ligand, 2,2':6',2'-terpyridine (terpy), in ethanol medium give rise to the formation of crystalline mixed chloro-hydroxo-aquo complex Ln(2)Cl(5)(OH)(H(2)O)(terpy). Its crystal structure consists of the connection of eight- and nine-fold coordinated lanthanide centers linked to each other via μ(2,3)-chloro and μ(3)-hydroxo species to form a tetranuclear unit, which are then further connected through chloro edges to generate infinite ribbons. Only one lanthanide cation in every two is chelated by terpy. Similar molar composition of the starting reactants led to the crystallization at room temperature of a second type of complex LnCl(3)(H(2)O)(terpy) (Ln = Nd, Eu). It is built up from the molecular assembly of dinuclear species containing two eight-fold coordinated lanthanide centers chelated by terpy and linked through a μ(2)-Cl edge. Luminescence spectra have been collected for the europium-based compound and indicates a strong red signal with the expected bands from the F-D transitions. The magnetic properties of the four compounds were investigated. Their behaviors correspond to that of the rare-earth ions present in the structure. The magnetic susceptibility of the neodymium-based compounds agrees with that of the Nd(III) ion with an (4)I(9/2) ground state split by crystal field. Concerning the Eu(III) derivatives, the term (7)F is split by spin-orbit coupling, the first excited states being thermally populated. Accordingly, the thermal dependence of the magnetic susceptibility was nicely reproduced by using appropriate analytical relations. The refined values of the spin-orbit coupling are consistent with the energies of the electronic levels deduced from the photoluminescence spectra. Unexpectedly, the magnetic susceptibility exhibits a hysteretic behavior in the range 45-75 K.