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In this work, the structural and spectroscopic characterization of trans-[Ni{(OPPh2)(EPPh2)N)}2(dmso)2], E = S, Se, complexes is described. These Ni(II) complexes contain two chelating (O,E) = [(OPPh2)(EPPh2)N)]− ligands, as well as two dimethyl sulfoxide (dmso) molecules coordinated via their O atoms. X-ray crystallography studies revealed a highly anisotropic pseudo-octahedral trans-NiO4E2 coordination environment, extending the literature dataset of their trans-[Ni(O,E)2(sol)2], sol = dmf, thf, counterparts. Collectively considered, these six complexes contain similar coordination spheres, exhibiting, however, subtle structural differences due to the nature of the donor atom (E) and solvent molecule (sol) coordinated to Ni(II). The spin Hamiltonian parameters of S = 1 trans-[Ni(O,Se)2(dmso)2], E = S, Se, were accurately determined by high-frequency and -field EPR spectroscopy, applying a methodology already used for trans-[Ni(O,E)2(sol)2], sol = dmf, thf. Magnetostructural correlations are explored between all members of this sub-family of Ni(II) complexes.

Efforts to comprehend the structural–spectrochemical correlations of crystalline metal–organic framework materials of Pb(II) with (a)cyclic and aromatic chelators linked to photoluminescent applications led to the hydrothermal pH-specific synthesis of crystalline materials [Pb{H2BTC}(phen)(H2O)]n·2nH2O(1), [Pb2{CBTC}]n(2), [Pb4(phen)8{CBTC}2(H2O)4]3·70.3H2O(3), and [Pb{HCTA}(H2O)2]n·nH2O(4). X-ray studies showed that 1–4 exhibit unique architectures linked to 2D–3D coordination polymers formulated by Z-type units composed of Pb2O2 cores, unusually high number of lattice–water molecules, and π–π and H-bond interactions. The contribution of the nature–structure properties of the aliphatic-(a)cyclic organic (poly)carboxylic/aromatic chelators-ligands to binary-ternary Pb(II) reactivity weaves into the assembly of supramolecular networks, thereby providing clear structural–spectroscopic inter-relationships exemplifying the observed photoluminescent activity in a distinct MOF-linked fashion.

Efforts to probe and delineate intricate structure–property relationships key to the development of crystalline Pb(II)-containing metal–organic framework materials led to the design and pH-specific hydrothermal synthetic investigation of binary/ternary Pb(II)-(di)tricarboxylate ligand (succinic, glutaric, tricarballylic acids) systems in the presence of variable-nature aromatic N,N′-chelators bipyridine (bpy)/phenanthroline (phen). The arisen crystalline materials [Pb(phen)(suc)]n (1), [Pb3(phen)3(glu)3]n·7nH2O (2), [Pb3(tca)2]n (3), and [Pb2(phen)2(tcaH)2]n·nH2O (4) provide evidence for structural correlations linking the nature of ligands with Pb(II) chemistry and the emerging crystalline-polymeric assemblies. Detailed physicochemical characterization (Fourier transform infrared spectroscopy, 13C-,207Pb-cross polarization magic angle spinning NMR, thermogravimetric analysis, luminescence) reveals distinct architecture, lattice dimensionality (2D-3D), and luminescence property correlations and identifies...

The reactions of Co(II) sources with N-salicylidene-o-aminophenol (H2saph), N-salicylidene-o-amino-4-methylphenol (H2saph-4Me) and N-salicylidene-o-amino-4-chlorophenol (H2saph-4Cl) were studied in MeOH. The new solid complexes (Bu4(n)N)[Co(III)(saph)2] (1), (Et3NH)[Co(III)(saph-4Me)2]⋅MeOH⋅MeCO2H (2⋅MeOH⋅MeCO2H) and (Et3NH)[Co(III)(saph-4Cl)2]⋅MeOH⋅MeCO2H (3⋅MeOH⋅MeCO2H) have been isolated and their structures determined by single-crystal, X-ray crystallography. The three compounds contain the mononuclear, low- spin octahedral anion [Co(III)L2](-) (H2L=H2saph, H2saph-4Me, H2saph-4Cl), in which both L(2)(-) ligands act as tridentate chelating, meridional ONO donors. The crystal structures of 2⋅MeOH⋅MeCO2H and 3⋅MeOH⋅MeCO2H are built through H-bonding and π-π stacking interactions. The new complexes were characterized by elemental analyses and spectroscopic (IR, Raman, UV/VIS, (1)H NMR) data. All data are discussed in terms of the nature of bonding and known structures.

The reactions of N-(2-carboxyphenyl)salicylideneimine and hydrated praseodymium(III) or neodymium(III) chlorides give 1D complexes with interesting structural and spectroscopic features; the chains possess the singly deprotonated ligand which is in its zwitterionic form.

The present paper investigates experimentally the impact dynamics of crown-type splashing for miscible two- and one-component droplet wall–film interactions over a range of Weber numbers and dimensionless film thicknesses. The splashing outcome is parametrised in terms of a set of quantifiable parameters, such as crown height, top and base diameter, wall inclination, number of fingers, and secondary droplet properties. The results show that the outcome of a splashing event is not affected by the choice of similar or dissimilar fluids, provided the dimensionless film thickness is larger than 0.1. Below this threshold, distinctive features of two-component interactions appear, such as hole formation and crown bottom breakdown. The observation of different crown shapes (e.g. V-shaped, cylindrical, and truncated-cone) confirms that vorticity production induces changes in the crown wall inclination, thus affecting the evolution of the crown height and top diameter. The evolution of the crown base diameter, instead, is mainly dependent on the relative importance of liquid inertia and viscous losses in the wall-film. The maximum number of liquid fingers decreases with increasing wall, film thickness, due to the enhanced attenuation of the effect of surface properties on the fingering process. The formation of secondary droplets is also affected by changes in the crown wall inclination. In particular, for truncated-cone shapes the occurrence of crown rim contraction induces a large scatter in the secondary droplet properties. Consequently, empirical models for the maximum number and mean diameter of the secondary droplets are derived for V-shaped crowns, as observed for the hexadecane-Hyspin interactions.

This work focuses on the development of “2 + 1” technetium and rhenium carbonyl complexes of the formula fac-[99mTc/Re(CO)3(L)(Spy)], where HSpy is 2-mercaptopyridine and acts as (NS) bidentate ligand and L is either triphenylphosphine (PPh3) or benzyl isocyanide (BnNC). Reaction of 2-mercaptopyridine with the precursors fac-(NEt4)2[Re(CO)3Br3] or [Re(CO)5Br] yields the dimeric complex fac-[Re(CO)3(Spy)]2, Re1. Re1 readily reacts with the monodentate ligand to yield the respective “2 + 1” fac-[Re(CO)3(PPh3/BnNC)(Spy)] complexes Re2/Re4. Re2 was also obtained in a single step reaction of the precursor fac-(NEt4)2[Re(CO)3Br3] with the mixture of ligands in equimolar amounts. Furthermore, the rhenium dicarbonyl complex cis, trans-[Re(CO)2(PPh3)2(Spy)] complex Re3 was synthesized by reaction of HSpy with the precursor mer, trans-[Re(CO)3(PPh3)2Cl]. All rhenium complexes were characterized by IR, NMR, elemental analysis and furthermore the structure of Re1, Re2, Re3 was solved by X-ray crystallography. At the 99mTc tracer level, the “2 + 1” complex fac-[99mTc(CO)3(PPh3)(Spy)], 99mTc2, was obtained in high radiochemical yield and low ligand concentrations and the complex was very stable in histidine and cysteine in challenge experiments.

The study of the general reaction system Co(NO3)2·6H2O/Ln(NO3)3·6H2O (Ln = Tb, Dy, Ho, Er)/2-pyridinealdoxime (paoH)/Bun4NOH in MeCN under aerobic conditions provided access to fac-[CoIII(pao)3] (4). Starting from Co(II) sources, i.e. in the absence of LnIII ions, the known [Polyhedron 28 (2009) 1638] mer diastereoisomer, mer-[CoIII(pao)3] (3), could only be isolated. The crystallization of 4 is probably due to the formation of a mixed CoIII/LnIII species in solution, which already possesses the fac-{CoIII(pao)3} unit. The fac isomer 4 is converted readily to the mer-isomer 3, while the opposite transformation was not achieved under the reaction conditions employed. Complex [CoIII(pao)2(paoH)](ClO4) (5) was prepared in good yield from the aerobic reaction of Co(ClO4)2·6H2O and excess of paoH in MeOH. Treatment of 5 in MeCN/MeOH with one equivalent of base gives 3. The structures of the new complexes 4·MeCN and 5 have been determined by single-crystal X-ray crystallography. The distorted octahedral CoIII ion in 4 is coordinated by three N,N′-bidentate chelating ligands; the molecule is the facial diastereoisomer. The distorted octahedral CoIII center in the cation of 5 is coordinated by four nitrogen atoms of two pao− ligands and two nitrogen atoms of one neutral paoH molecule; the disposition of the donor atoms around the metal center is meridional. The cations [CoIII(pao)2(paoH)]+ form centrosymmetric dimers in the crystal lattice as a consequence of O(oxime)–H⋯O− (oximate) H bonds; the dimers form tetramers through weak C(oxime)–H⋯O(oxime) H-bonding interactions. Metric parameters show that the deprotonated oximato group of the pao− ligands in 4·MeCN and 5 is better described as . Solid-state UV–Vis and IR data are discussed in terms of the low-spin octahedral stereochemistry of CoIII and the nature of bonding, respectively. The 1NMR spectrum of 4·MeCN in CDCl3 provides strong evidence of the fac → mer transformation in solution.

In this work, we focused on the development of mixed ligand technetium and rhenium complexes of the general formula fac-[99mTc/Re(CO)3(PPh3)(ox/tq)] and cis, trans-[99mTc/Re(CO)2(PPh3)2(ox/tq)] where 8-hydroxyquinoline (oxH) and 8-mercaptoquinoline (tqH) act as [NO] and [NS] bidentate ligands. The synthesis of rhenium complexes fac-[Re(CO)3(PPh3)(ox/tq)] Re3/Re4 was conducted by reacting oxH or tqH and triphenylphosphine with fac-(NEt4)2[Re(CO)3Br3] (1) or by reacting triphenylphosphine with the dimer complexes fac-[Re(CO)3(ox/tq)]2 Re1/Re2. The synthesis of the rhenium complexes cis, trans-[Re(CO)2(PPh3)2(ox/tq)] Re5/Re6 was conducted either by reacting 1 with oxH/tqH in equimolar amounts and triphenylphosphine in excess or by reacting oxH/tqH with the precursor mer, trans-[Re(CO)3(PPh3)2Cl]. All the complexes were characterized by IR, NMR and X-ray crystallography. The analogous 99mTc complexes were prepared by reacting oxH/tqH and PPh3 with the precursor fac-[99mTc(CO)3(OH2)3]+ (2). When the reaction mixture was left at rt for 2 h the monophosphino complexes fac-[99mTc(CO)3(PPh3)(ox/tq)] 99mTc3/99mTc4 were formed, while by applying heating at 75 °C for 30 min the dicarbonyl complexes cis, trans-[99mTc(CO)2(PPh3)2(ox/tq)] 99mTc5/99mTc6 were formed quantitatively. The 99mTc complexes were identified by HPLC chromatographic comparison with the analogous rhenium complexes and their stability was studied.

Poised to investigate the association of vanadium with physiological substrates in materials capable of exerting anticancer biological activity, pH-specific synthetic chemical reactivity between vanadium and triethyl ammonium acetate/trigonelline in aqueous and mixed organic-aqueous media led to the isolation of three new binary composite materials, namely K2[(MeN(+)C5H4COOH)2][V10O28H2]·2H2O (1), [(H2N(+)Me2)4][V10O28H2][Me3N(+)CH2COO(–)]2 (2), and [(Me3N(+)CH2COOH)4][V10O28H2][Me3N(+)CH2COO(–)]2·2H2O (3). 1–3 were characterized by elemental analysis, FT-IR and UV/Vis spectroscopy, Cyclic voltammetry, TGA-DTG, and X-ray crystallography. In all three compounds, the [V10O28H2]4– core unit is a common cluster assembly, with the vanadium in the +5 oxidation state. The counteracting cationic assembly in each composite material originates in the betaine starting reagent or the solvent out of which the materials crystallized. Biological activity studies of 1 and 3 in vitro in MCF-7 breast epithelial and A549 lung adenocarcinoma cell cultures show that both materials inhibit the viability of both cell lines in a dose-dependent fashion, in juxtaposition to the behavior of the betaine components present in these materials. Collectively, the herein studies a) reveal the uniquely defined synthetic methodologies and physicochemical properties of the variably assembled [V10O28H2]4– core units crystallized into the composite binary polyoxovanadate-betaine lattice structures, b) unravel the distinct cytotoxicity profile of the composite materials toward MCF-7 and A549 cells, and c) attest to their future potential as metallodrugs of pharmacological significance in anticancer activity.

The synthesis and characterization of the new NSN tridentate bifunctional chelating agent 3-[2-(2′-pyridin-2-yl-ethylsulfanyl)ethylamino] propionic acid (as its hydrochloric salt, 1 ) and of its corresponding rhenium complex fac -[Re(NSN)(CO) 3 ] + , 2 , is described. Both compounds were characterized by elemental analysis, IR and NMR spectroscopies and X-ray crystallography. In complex 2 the coordination geometry around rhenium is distorted octahedral with the NSN atoms participating in the coordination sphere while the carboxylate group remains free. At tracer level, the analogous complex fac -[ 99m Tc(NSN)(CO) 3 ] + , 3 , was obtained in high yield by reacting ligand 1 with the fac -[ 99m Tc(H 2 O) 3 (CO) 3 ] + precursor at pH 6.5. The structure of 3 was established by HPLC comparison to the prototype rhenium complex 2. Complex 3 is stable in solution as well as in the presence of strongly coordinating agents like histidine or cysteine. Our data indicate that ligand 1 can be used as a bifunctional NSN chelating agent in the design of potential 99m Tc-radiopharmaceuticals.

The reactivity pattern of [V(Cp) 2 Cl 2 ] towards the weakly coordinating CF 3 SO 3 − anion in the absence of chelating or bridging organic ligands has been investigated, where Cp − is the η 5 -C 5 H 5 − ligand. The synthesis, single-crystal X-ray structure and physical/spectroscopic characterization are reported for the product [V(Cp) 2 (H 2 O) 2 ](CF 3 SO 3 ) 2 ·THF ( 1 ·THF). The coordination about the V IV atom, formed by the two H 2 O molecules and the centroids of the cyclopentadienyl rings, is distorted tetrahedral. The [V(Cp) 2 (H 2 O) 2 ] 2+ cation is connected to the triflate anions via hydrogen bonds. Magnetic susceptibility, EPR and IR data are discussed in terms of the nature of bonding and the structure of the complex.

The [Ni{(Ph2P)2N-S-CHMePh-P,P′}Br2] complex was prepared by a ligand-exchange reaction between [Ni(dme)Br2] (dme is 1,2-dimethoxyethane) and the P–N–P ligand (Ph2P)2N(S-CHMePh). X-ray crystallography revealed a square planar NiP2Br2 coordination sphere, i.e., the presence of a four-membered Ni–P–N–P ring. The same structural features with nearly equal values of the X–Ni–X, P–Ni–P and P–N–P angles have been earlier revealed for the isomorphous [M{(Ph2P)2N-S-CHMePh-P,P′}Cl2], M = Ni, Pd, complexes. The structure of the above complexes significantly differs from that of [Ni(dppp)Cl2] (dppp is 1,3-bis{diphenylphosphine}propane). This NiP2Cl2-type complex comprises a six-membered Ni–P–C–C–C–P ring, with significantly larger P–Ni–P and much smaller Cl–Ni–Cl angles. The 1H and 31P NMR properties of [Ni{(Ph2P)2N-S-CHMePh-P,P′}Br2] are consistent with its crystal structure. The [Ni{(Ph2P)2N-S-CHMePh-P,P′}X2] complexes were tested as catalysts in Kumada and Suzuki–Miyaura coupling reactions, and their reactivity was compared with that of [Ni(dppp)Cl2]. The differences observed in their catalytic efficiency are discussed with regards to their structural characteristics.

The reaction of the C-functionalized cyclam chelating agent 1,4,8,11-tetraazacyclotetradecane-6-carboxylic acid (1) with CuCl2 generated a stable and neutral complex 2, which was characterized by elemental analysis, UV/Vis and IR spectroscopy, electrospray ionization mass spectrometry (ESI-MS), EPR spectroscopy and X-ray crystallography. The secondary amine groups of 1 were protected to generate 3, which was further conjugated with the bombesin (BN) derivative H2N-(Ornithine)3-BN(2–14) by a solid phase peptide synthesis method. After cleavage from the resin and deprotection, the resulting product 5 was obtained and characterized with ESI-MS and NMR spectroscopy, and was subsequently complexed under mild conditions with CuCl2 to generate complex 6 in high yield. Complex 6 was characterized with UV/Vis spectroscopy, ESI-MS and EPR spectroscopy. The stability of complexes 2 and 6 was tested against cysteine, histidine and glutathione, and both complexes were found to be stable. The cyclam BN conjugate 5 and its CuII complex 6 were suitable for targeting the gastrin releasing peptide receptors (GRPrs) that are over expressed on PC-3 cells. Both 5 and 6 showed high binding affinity to GRPrs during in vitro cell assays with human PC-3 prostate cancer cells. The half maximal inhibitory concentration (IC50) values observed for 5 and 6 (0.30 ± 0.03 and 0.33 ± 0.03 nM, respectively) were similar to that of the [Tyr]4-BN peptide (0.45 ± 0.04 nM), which was used as standard.

The reactions of the NSO ligands 2-[2-(pyridin-2-yl)ethylthio]acetic acid (HL1), 3-[2-(pyridin-2-yl)ethylthio]propanoic acid (HL2), 2-(carboxymethylthio)-3-(1H-imidazol-4-yl)propanoic acid (H2L3), and 2-(carboxyethylthio)-3-(1H-imidazol-4-yl)propanoic acid (H2L4) with [NEt4]2[ReBr3(CO)3] are presented. Ligands HL1, H2L3, and H2L4 act as tridentate NSO chelators and readily generate the fac-[Re(NSO)(CO)3]complexes Re-L1, Re-HL3, and Re-HL4. Ligand HL2 acts as NSO tridentate chelator only in the presence of base to give complex Re-L2, while without base it coordinates as a NS bidentate chelator to generate complex fac-[ReBr(NS)(CO)3], Re-HL2. All complexes were isolated and characterized by elemental analysis, IR and 1H, 13C NMR spectroscopy. Complex Re-L1, Re-HL2, and Re-HL3 were characterized also by X-ray crystallography. Furthermore, the analogous technetium complexes fac-[99mTc(NSO)(CO)3]+, 99mTc-L1, 99mTc-L2, 99mTc-HL3, and 99mTc-HL4 were synthesized by reacting ligands HL1–H2L4 with the fac-[99mTc(OH2)3(CO)3]+ precursor for 30 min at 75 °C. The tracer complexes 99mTc-L1–99mTc-HL4 were found to be stable in L-cysteine and L-histidine challenge experiments. The bifunctional chelating agents that bear a second carboxylate group are promising for the development of targeted 99mTc radiopharmaceuticals.

Reactions of Ca(NO3)2·4H2O and diethylmalonic acid (Et2malH2, its anions represent functional side-chain analogs of γ-carboxyglutamic acid residues which are implicated as essential Ca2+-binding ligands in a variety of proteins) in aqueous media have afforded compounds [Ca(Et2malH)2(H2O)3]n (1) and [Ca(Et2mal)(H2O)]n (2) at pH 4 and 8, respectively. The structure of 1 was determined by single-crystal, X-ray crystallography, which revealed an 1D coordination polymer. The diethylmalonate ligands exist in their monoanionic form and present two different coordination modes. The CaII ion is 7-coordinate with a pentagonal bipyramidal geometry. IR data are discussed in terms of the known (1) and proposed (2) structures of the complexes. The role of the carboxylate binding modes in determining the affinity of Ca2+ for the various metal binding sites in proteins containing the γ-carboxyglutamate residue is discussed in the light of our and previous results.

Reaction of Cd(NO3)2∙ 4H2O and di-2-pyridyl ketone [(py)2CO] in dry MeCN led to complex [Cd2(NO3)4{(py)2CO}2] (1) in which the ketonic grouping of each organic ligand bridges the two CdII atoms. Complex 1 is extremely reactive towards nucleophiles; it reacts with H2O giving the cubane cluster [Cd4(NO3)4{(py)2C(OH)(O)}4] (2) possessing the 3.3011 (Harris notation) gem-diolate(− 1) form of the ligand. Upon excitation at 380 nm, solid 1 displays blue green photoluminescence at room temperature.

Aiming at the development of 99mTc-based infection-specific imaging agents, the synthesis and characterization of rhenium and technetium-99m tricarbonyl complexes with derivatized ciprofloxacin and norfloxacin is hereby reported. The ligands were prepared by coupling the tridentate chelator picolylamino-N,N-diacetic acid (PADA) with the piperazinyl (NH) nitrogen of ciprofloxacin or norfloxacin, through the employment of the PADA anhydride. The corresponding rhenium complexes were synthesized using the fac-[NEt4]2[ReBr3(CO)3] precursor and were fully characterized by elemental analysis and NMR spectroscopy. X-ray crystallography of the ciprofloxacin complex showed that the geometry about rhenium is distorted octahedral defined by the NNO donor atom set of the tridentate chelator and the three carbonyl groups. The analogous technetium-99m complexes were prepared quantitatively through the use of the fac-[99mTc(H2O)3(CO)3]+ precursor and their structure was established by comparative HPLC studies using the well-characterized rhenium complexes as reference. Preliminary studies with the technetium-99m complexes showed high bacterial uptake in vitro.

Reactions of copper(II) sources with 1,2-bis(4-pyridyl)ethane (bpe) yielded metal–organic networks with diverse topologies and dimensionalities. Compounds [Cu(bpe)2(dmf)2]n(ClO4)2n·2ndmf (1·2ndmf), [Cu(bpe)2(dmf)2]n(ClO4)2n·3.5ndmf (2·3.5ndmf), [Cu(bpe)2(NO3)2]n·2nH2O (4·2nH2O) and [Cu2(bpe)(O2CMe)4]n·0.7nH2O (5·0.7nH2O) have been isolated by altering the copper(II) source, the reaction solvent and the crystallization process. Compounds 1·2ndmf and 2·3.5ndmf consist of cationic [Cu(bpe)2(dmf)2]2+ repeating units assembled to 1D and 2D (4,4) networks, respectively, and represent supramolecular isomers due to the conformational isomerism of the bridging bpe molecules. Compound 4·2nH2O consists of neutral mononuclear [Cu(dpe)2(NO3)2] repeating units assembled to inclined interpenetrating (4,4) sheets describing an overall entanglement that is 3D in nature, and compound 5·0.7nH2O consists of neutral dinuclear repeating units assembled to cross-linked 1D chains.

The initial employment of N,N-bis(2-hydroxyethyl)glycine (bicine; bicH3) in CdCl2 chemistry is reported, and the syntheses, IR spectra and crystal structures of the 1D coordination polymers [CdCl(bicH2)]n·nH2O (1·H2O) and [CdNaCl2(bicH2)(MeOH)]n (2) are described. The identity of the products depends on the solvent, the reaction temperature and the alkali metal ion of the base used. The structure of 1·H2O consists of zig-zag chains. The 7-coordinate CdII atoms are bridged by η1:η1:μ2 carboxylate groups of the 2.21111 (Harris notation) bicH2− ligand. The coordination geometry of the metal center can be either described as a very distorted pentagonal bipyramidal or as a distorted capped octahedral. In the structure of 2 the CdII atoms form an almost linear chain with neighboring NaI atoms on opposite sites of the chain. Every pair of CdII atoms is linked by two chloro ligands and the two oxygen atoms of the bicinate carboxylate group. The CdII and NaI atoms are bridged by one μ2 carboxylate bicinate oxygen and one μ3 chloro ligand. The 3.21,211121212 coordination mode of bicH2− is unprecedented. The CdCl4(Ocarboxylate)2 and Na(Ohydroxyl)2(Ocarboxylate)(OMeOH)NCl coordination spheres are octahedral and trigonal prismatic, respectively. IR data of the complexes are discussed in terms of the coordination modes of bicH2− and the known structures.

The synthesis of the M[(OPPh(2))(SePPh(2))N](2), M = Co (1), Ni (2) complexes was accomplished by metathetical reactions between the corresponding M(II) salts and the deprotonated form of the dichalcogenated imidodiphosphinato ligand [(OPPh(2))(SePPh(2))N](-). X-Ray crystallography revealed a pseudo-tetrahedral MO(2)Se(2) coordination sphere, owing to the asymmetric (O,Se) nature of the chelating ligand. Slow diffusion of the coordinating solvent dimethylformamide into dichloromethane solutions of Ni[(OPPh(2))(SPPh(2))N](2) or 2, afforded the pseudo-octahedral trans-[Ni{(OPPh(2))(EPPh(2))N}(2)(dmf)(2)], E = S (3), Se (4) complexes, respectively. UV-vis spectra provided evidence that, in solution, complexes 3 and 4 revert to the corresponding pseudo-tetrahedral complexes, most likely due to the removal of the dmf molecules from the coordination sphere. The IR spectra of all complexes reflect the structural features observed by X-ray crystallography. The magnetic properties of the S = 3/2 complex 1, as well as the S = 1 complexes 2, 3 and 4, were extensively studied, and the magnitude of their g and zero-field splitting D parameters was estimated. The reported structures establish a structural transformation of tetrahedral to octahedral geometry of Ni(II) complexes bearing asymmetric imidodiphosphinate ligands, upon recrystallization from coordinating solvents. The structural correlations between the Ni(II) coordination spheres are aided by DFT and ab initio multi-configuration MCSCF calculations, which investigate the corresponding interconversion pathways. In addition, the calculations provide descriptions of the bonding interactions in the octahedral Ni(II) complexes, as well as predictions of their D values.

Reactions of malonic acid (H2mal) with PrCl3·6H2O afforded the known complex [Pr2(mal)3(H2O)6]n (1), and compounds [Pr2(mal)3(H2O)6]n·2nH2O (2·2nH2O), [PrCl(mal)(H2O)3]n·0.5nH2O (3·0.5nH2O) and [Pr(mal)(Hmal)(H2O)3]n·nH2O (4·nH2O) using various reaction ratios, reaction media (H2O, MeOH) and pH values. Analogous reactions with CeCl3·7H2O afforded compounds [Ce2(mal)3(H2O)6]n (5), [CeCl(mal)(H2O)3]n·nH2O (6·nH2O) and [Ce(mal)(Hmal)(H2O)3]n·nH2O (7·nH2O). Compounds 2·2nH2O and 3·0.5nH2O were characterized by X-ray crystallography, and 4–7 by microanalytical and spectroscopic data. The malonate(-2) ligand adopts three different coordination modes in the structures of 1–3, i.e., the μ2-κO:κO′:κO″ and the μ4-κ2O:κO′:κ2O″:κO‴ in 1 and 2 leading to a 3D network structure, and the μ3-κ2O:κO′:κ2O″:κO‴ in 3 promoting an 1D structure. The thermal decomposition of 1 and 3·0.5nH2O was monitored by TG/DTA and TG/DTG measurements. The structural features of 1–3 are discussed in terms of known malonato(-2) LnIII and CaII complexes. The bioinorganic chemistry relevance of our results is discussed.

A bioinorganic approach into the problem of the isomorphous substitution of calcium(II) by lanthanide(III) ions in biological systems is discussed. Reactions of malonamic acid (H2malm) with CaII and NdIII sources under similar conditions yielded the compounds [Ca(Hmalm)2]n (1), [Nd(Hmalm)2(H2O)2]n(NO3)n (2) and [Nd(Hmalm)2(H2O)2]nCln·2nH2O (3·2nH2O). Their X-ray crystal structure data show that the malonamate(-1) ligand presents two different ligation modes and coordinates through the two carboxylate and the amide-O atoms, thus bridging three CaII ions in 1 and two NdIII ions in 2 and 3·2nH2O. Complex 1 is a 3D coordination polymer based on neutral repeating units, whereas 2 and 3·2nH2O are 1D coordination polymers based on the same cationic repeating unit. Hydrogen bonding interactions further stabilize the 3D framework structure of 1 and assemble the 1D chains of 2 and 3·2nH2O into 3D networks. The three complexes were characterized spectroscopically (IR, far-IR, and Raman) and the thermal decomposition of 2 and 3·2nH2O was monitored by TG/DTA and TG/DTG measurements. Variable-temperature magnetic susceptibility data for 2 are also reported. The bioinorganic chemistry relevance of our results is discussed.

The reaction of succinamic acid (H2sucm) with Ca(NO3)2·4H2O yielded compounds [Ca(Hsucm)(NO3)(H2O)]n (1) and [Ca(Hsucm)2]n (2). The succinamate(-1) ligand presents two new ligation modes and coordinates through the two carboxylato and the amide O-atoms, thus bridging three CaII ions which assemble into zig-zag 1D chains in 1 and 2D networks in 2. Intermolecular hydrogen bonding interactions in the crystal structures of 1 and 2 result in overall 3D framework structures. Both compounds have been characterized by IR and 1H NMR spectroscopy, and their thermal decomposition was monitored by TG/DTG and DSC measurements. The structural comparison of 1 and 2 with known lanthanide(III) succinamate(-1) complexes reveals differences in the coordination mode of the ligand and in the coordination number of the metal ions; the biological relevance of these differences is discussed.

The synthesis and characterization of the neutral 2+1 mixed ligand complex fac- Re(CO) 3 (acac)(isc) ( 4 ) with acetylacetonate (acac) as the bidentate ligand and an isocyanide (the isocyanocyclohexane, isc) as the monodentate ligand is described. The synthesis of 4 proceeds through the intermediate formation of the fac- Re(acac)(H 2 O)(CO) 3 precursor complex 2 . Complex 4 was characterized by elemental analysis, spectroscopic methods, and X-ray crystallography showing a distorted octahedral arrangement of the ligands around Re. At technetium-99m level, the corresponding fac - 99m Tc(acac)(isc)(CO) 3 complex 5 was obtained in high yield by reacting the fac - 99m Tc(acac)(H 2 O)(CO) 3 precursor complex 3 with isocyanocyclohexane and its structure was established by chromatographic comparison with the prototypic rhenium complex using high performance liquid chromatography.

The use of succinamic acid (H2sucm) in CuII/N,N′,N″-donor [2,2′:6′,2″-terpyridine (terpy), 2,6-bis(3,5-dimethylpyrazol-1-yl)pyridine (dmbppy)] reaction mixtures yielded compounds [Cu(Hsucm)(terpy)]n(ClO4)n (1), [Cu(Hsucm)(terpy)(MeOH)](ClO4) (2), [Cu2(Hsucm)2(terpy)2](ClO4)2 (3), [Cu(ClO4)2(terpy)(MeOH)] (4), [Cu(Hsucm)(dmbppy)]n(NO3)n·3nH2O (5.3nH2O), and [CuCl2(dmbppy)]·H2O (6·H2O). The succinamate(−1) ligand exists in four different coordination modes in the structures of 1–3 and 5, i.e., the μ2-κO:κO′:κO″ in 1 and 5 which involves asymmetric chelating coordination of the carboxylato group and ligation of the amide O-atom leading to 1D coordination polymers, the μ2-κ2O:κO′ in 3 which involves asymmetric chelating and bridging coordination of the carboxylato group, and the asymmetric chelating mode in 2. The primary amide group, either coordinated in 1 and 5, or uncoordinated in 2 and 3, participate in hydrogen bonding interactions, leading to interesting crystal structures. Characteristic IR bands of the complexes are discussed in terms of the known structures and the coordination modes of the Hsucm− ligands. The thermal decomposition of complex 5·3nH2O was monitored by TG/DTG and DTA measurements.

Zinc mononuclear complexes with the second-generation quinolone antibacterial drug enrofloxacin in the absence or presence of a nitrogen donor heterocyclic ligand 1,10-phenanthroline or 2,2'-bipyridine have been synthesized and characterized. Enrofloxacin is on deprotonated mode acting as a bidentate ligand coordinated to zinc ion through the ketone and a carboxylato oxygen atoms. The crystal structure of bis(enrofloxacinato)(1,10-phenanthroline)zinc(II), 2, has been determined by X-ray crystallography. The biological activity of the complexes has been evaluated by examining their ability to bind to calf-thymus DNA (CT DNA) with UV and fluorescence spectroscopies. UV studies of the interaction of the complexes with DNA have shown that they can bind to CT DNA and the DNA binding constants have been calculated. Competitive studies with ethidium bromide (EB) have shown that the complexes exhibit the ability to displace the DNA-bound EB indicating that they bind to DNA in strong competition with EB for the intercalative binding site. The complexes exhibit good binding propensity to human and bovine serum albumin proteins having relatively high binding constant values.

The unsymmetrical nickel 1,2-dithiolene complex based on diphenylethylenedithiolate (dpedt) and 6,7-dihydro-5H-1,4-dithiepin-2,3-dithiolate (pddt) was prepared and characterized. Depending on the conditions of crystallization, it is possible to obtain the complex in two different crystalline forms. X-ray structure studies recognize these forms as Ni(dpedt)(pddt) and Ni(dpedt)(pddt)·CS2. The experimental optical and electrochemical parameters are in a good agreement with the calculated ones, using the corresponding parameters of the symmetrical complexes, Ni(dpedt)2 and Ni(pddt)2. The HOMO and LUMO energy levels, obtained from optical and electrochemical measurements, are very close to the Fermi energy of (metallic) Au. The chemical and electrochemical properties of both forms showed that they are stable in air and could be candidate materials for optics and electronics.

The synthesis and structural characterization of the neutral rhenium complex fac-[Re(NSO)(CO)3], Re-1, where (NSO) is a tridentate bifunctional chelating agent, 3-(carboxymethylthio)-3-(1H-imidazol-4-yl)propanoic acid (1), is presented. The complex crystallized from methanol–water and its structure was assigned by IR and 1H, 13C NMR spectroscopies and X-ray crystallography. Furthermore, the analogous technetium complex fac-[99mTc(NSO)(CO)3], 99mTc-1, was synthesized in high yield by reacting ligand 1 with the fac-[99mTc(OH2)3(CO)3]+ precursor for 30 min at 85 °C. The tracer complex was found to be more than 95% stable in the L-histidine challenge experiment. Our data indicate that the bifunctional NSO chelating agent 1 can be successfully applied for the development of potential 99mTc-radiopharmaceuticals.

The use of succinamic acid (H 2 sucm)/N,N′-chelate (2,2′-bipyridine, bpy; 4,4′-dimethyl-2,2′-bipyridine, dmbpy; 1,10-phenanthroline, phen) ‘ligand blends’ in CuX 2 · y H 2 O (X = NO 3 , y = 3; X = Cl, y = 0) chemistry has yielded the new complexes [Cu 2 (Hsucm) 3 (bpy) 2 ](NO 3 )·0.5MeOH ( 1 ·0.5MeOH), [Cu 2 (Hsucm)(OH)Cl(bpy) 2 ](OH)·3.6H 2 O ( 5 ·3.6H 2 O) and [Cu 2 (Hsucm) 2 Cl 2 (phen) 2 ] ( 6 ). The succinamate(−1) ion behaves as a carboxylate ligand and exists in two different coordination modes in the structures of the above complexes, i.e., the common syn , syn μ 2 -κ O :κ O ′ in 1 , 5 and 6 , and the μ 2 -κ 2 O :κ O ′ in 1 . The primary amide group of Hsucm − remains uncoordinated and participates in intermolecular hydrogen bonding interactions leading to 1D, 2D and 3D networks. Characteristic IR bands of the complexes are discussed in terms of the known structures and the coordination modes of the Hsucm − ligands.

The synthetic investigation of the Cu(ClO4)2·6H2O/fumaric acid (H2fum)/N,N’-chelates (1,10-phen, 2,2′-bpy) tertiary reaction systems has yielded mononuclear, dinuclear and tetranuclear complexes, and three coordination polymers. The chemical and structural identity of the products depends on the solvent, the absence or presence of external hydroxides in the reaction mixtures and the N,N’-donor. Three fumarato(−2) complexes, i.e. compounds [Cu2(fum)(phen)4](ClO4)2·2H2O (1·2H2O), [Cu(fum)(phen)(H2O)]n (3) and [Cu2(fum)(bpy)2(H2O)2]n(ClO4)2n (6), were isolated and structurally characterized, and four non-fumarato complexes, i.e. compounds [Cu4(μ3-ΟΗ)2(μ2-ΟΗ)2(phen)4(H2O)2](ClO4)4·2H2O (2·2H2O), [Cu(ClO4)(phen) (MeCN)2(H2O)](ClO4) (4), [Cu(ClO4)(phen)(MeCN)2]n(ClO4)n (5) and [Cu(ClO4)2(bpy)(MeCN)2] (7), were simultaneously obtained from the reaction systems investigated. The coordination versatility of the fumarato(−2) ligand is reflected to the three different coordination modes observed in 1·2H2O, 3 and 6; the monodentate bridging μ2-κO:κO′ mode in 3, the asymmetric chelating bridging μ2-κO:κO′:κO′′:κO′′′ mode in 1·2H2O and 3, and the syn,syn bridging μ4-κO:κO′:κO′′:κO′′′ mode in 6. The crystal structures of the complexes are stabilized by intra- and inter-molecular hydrogen bonding and π–π stacking interactions leading to interesting supramolecular architectures. Characteristic IR bands of the complexes are discussed in terms of the known structures, and the coordination modes of the fum2− ligands.

Interaction of phenyl 2-pyridyl ketoxime (PhPyCNO)/X(-)"blends" (X(-) = OH(-), Cl(-), ClO(4)(-), 2,4-D) (2,4-DH = 2,4-dichlorophenoxyacetic acid) with copper perchlorate has yielded trinuclear clusters that have been characterized as inverse-9-metallacrown-3, accommodating one or two anions. The structure of the complex [Cu(3)(PhPyCNO)(3)(mu(3)-OH)(2,4-D)(2)] x 1.25CH(3)OH.0.25CH(3)CN (1) has been determined by single-crystal X-ray crystallography. Spectroscopic studies of the interaction of copper inverse {(OH)[9-MC(CuN(PhPyCNO))-3]} metallacrowns with DNA showed that these compounds bind to dsDNA by intercalative mode with an additional covalent {(OH)[9-MC(Cu(PhPyCNO))-3]}-DNA interaction leading to hydrolytic cleavage of DNA that may be assigned to the presence of the hydroxyl group in the inverse metallacrown ring. The binding strength of [Cu(3)(PhPyCNO)(3)(mu(3)-OH)(2,4-D)(2)] (1) complex for CT-DNA was determined to be 0.56 x 10(5) M(-1). All the complexes exhibited the ability to displace the DNA-bound EthBr. DNA electrophoretic mobility experiments showed that all complexes, at low cluster concentration, are capable of binding to pDNA and linear DNA. At higher cluster concentration and in the absence of any reducing agent they showed marked chemical nuclease activity.

The reactions of representative 2-pyridyl oximes with NiII salts in the presence of a base have been investigated. The synthetic study has led to the new triangular complexes [Νi3(ppko)6]·2H2O·0.5EtOH·MeOH (1·2H2O·0.5EtOH·MeOH), [Νi3(mpko)3(HCO2)2(mpkoH)2](ClO4) (2) and [Νi3(ppko)3(HCO2)2(ppkoH)2](ClO4) (3), where ppko− is the anion of phenyl(2-pyridyl)ketone oxime and mpko− is the anion of methyl(2-pyridyl)ketone oxime. The structures of compounds 1 and 2 have been determined by single crystal X-ray diffraction. The ppko− ligand in 1 adopts four different coordination modes including the unique NpyridylOoximate chelating one which gives rise to a 6-membered chelating ring, while the neutral and the deprotonated oxime ligands in 2 adopt three different coordination modes. The magnetic properties of 1 and 2 have been studied by variable-temperature dc magnetic susceptibility techniques which indicate antiferromagnetic interactions.

A novel nickel-based complex coordinated with an asymmetric diphosphinoamine ligand was synthesized and fully characterized. Single crystals of good quality were also obtained, and the solid-state structure of the complex was studied via X-rays diffraction. The catalytic activity of this Ni(II) complex in the vinyl-type polymerization of norbornene was studied with methylaluminoxane (MAO) as the cocatalyst/activator. The influence of the reaction time, the equivalents of MAO used, and the concentration of the monomer on: (i) the activity of the catalytic system; (ii) the isolated yield of the polymer; and (iii) the molecular weight and molecular weight distribution of the polymer were investigated. The isolated polynorbornene (PNB) yields are significantly higher compared with those reported for other similar nickel-based systems. The as-obtained PNBs are characterized by high molecular weights and relatively narrow and monomodal molecular weight distributions (amongst the narrowest reported in the literature). The linear dependence of the molecular weight of the obtained PNB on the concentration of norbornene points toward a controlled polymerization reaction. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5241–5250, 2009

A systematic investigation of the 1:2:1:2 Cu(NO 3 )·2.5H 2 O/ H 2 L/bpy/LiOH·H 2 O (H 2 L = maleamic acid) reaction system in MeCN/H 2 Owas carried out. The compounds [Cu 2 (HL) 2 -(bpy) 2 (H,O) 2 ](NO 3 ) 2 (1), [Cu 2 (HL) 2 (bpy) 2 (H 2 O) 2 ](NO 3 ) 2 · 2H 2 O (1.2H 2 O), [Cu 2 Li 2 (L') 2 (bpy) 2 (H 2 O) 6 ][Cu 2 (HL) 2 (bpy) 2 -(H 2 O) 2 ](NO 3 ) 4 (2), [Cu 4 (L') 2 (NO 3 ) 2 (bpy) 4 (H 2 O) 2 ](NO 3 ) 2 ·2H 2 O (3·2H 2 O) and [Cu(L')(bpy)] n ·2nH 2 O (4·2nH 2 O) were isolated, depending on the crystallization method employed. Complexes 2, 3·2H 2 O and 4·2nH 2 O contain the maleate(-2) anion (L' 2- ), which was formed in situ through metal-ion-assisted hydrolysis of the primary amide group of H 2 L. Efforts to prepare complex 3 from the direct use of maleic acid (H 2 L') afforded compounds 4·2nH 2 O, [Cu 4 (L') 2 (NO 3 ) 2 (bpy) 4 (H 2 O) 2 ]-(NO 3 ) 2· 2[Li(NO 3 )(H 2 O) 3 ]·4H 2 O (5·4H 2 O) and [Cu(NO 3 )(bpy)-(H 2 O) 3 ](NO 3 ) (6) from the 1:1:1:2 Cu(NO 3 )·2.5H 2 O/H 2 L'/ bpy/LiOH·H 2 O reaction system in MeCN/H 2 O. The maleamate(-1) ligand presents the less common η 1 :μ 2 coordination mode in the cations of 1, 1·2H 2 O and 2. The maleate(-2) ligand exhibits the η 1 :η 1 :η 1 :η 1 :η 1 :μ 3 coordination mode in the [Cu II 4 ] cations of 3·2H 2 O and 5·4H 2 O and in the [Cu II 2Li I 2 ] heterometallic cation of 2. The crystal structures of the complexes are stabilized by various H-bonding patterns. Characteristic IR bands of the complexes are discussed in terms of the known structures and the coordination modes of the ligands. Magnetic susceptibility measurements for 3·2H 2 O reveal weak ferromagnetic interactions along the periphery of the Cu 4 rhombus (J = 3.3 cm -1 , -2J ij S i S j Hamiltonian formalism), which stabilizes an S = 2 ground state.

Employing the mononuclear complex [Ni{(py)C(Me)NO}2{(py)C(Me)NOH}] (1) as ‘ligand’ [(py)C(Me)NOH = methyl 2-pyridyl ketone oxime], the use of the ‘metal complexes as ligands’ approach has led to the synthesis of the mixed NiII/LnIII complexes [NiTb{(py)C(Me)NO}2(NO3)3{(py)C(Me)NOH}] (2), [Ni2Ln2{(py)C(Me)NO}6(NO3)4] (Ln = Dy, 3; Ln = Tb, 4) and [Ni2Tb{(py)C(Me)NO}6](NO3) (5). The structures of 2, 3, and 5, and the magnetic properties of 2 and 5 are briefly discussed.

The use of the 2-pyridyl oxime ligands (LH) 2-pyridinealdoxime, methyl 2-pyridyl ketone oxime and phenyl 2-pyridyl ketone oxime in Co chemistry has been investigated and led to two families of compounds. The first family includes the mononuclear octahedral, low-spin complexes [CoIII(L)3], while the second family consists of the trinuclear, mixed-valent linear clusters [ Co III 2 CoII(L)6]X2 (X = ClO 4 - , PF 6 - ). The latter are prepared by the reactions of the former with an appropriate CoII source. The structural, physical and spectroscopic properties of the complexes are described.

The reaction of 1-hydroxybenzotriazole, btaOH, with nickel(II) acetate tetrahydrate, in the absence of an external base, has been investigated. The reaction of Ni(O2CMe)2 · 4H2O with one equivalent of btaOH in nPrOH leads to the the first structurally characterized tridecanuclear nickel(II) cluster and the biggest metal/btaOH or btaO− cluster discovered to date, [Ni13(OH)6(O2CMe)8(btaO)12(H2O)6(nPrOH)4] · 6.6H2O · 4(nPrOH) (1 · 6.6H2O · 4(nPrOH)). The centrosymmetric molecule contains the {Ni13(μ3-ΟΗ)6(μ3-ONNNR)12}8+ core (R– = C6H4–) and is characterized by competitive antiferromagnetic exchange interactions within its pentanuclear subunits containing the μ3-ΟΗ− bridges. The reaction of 1 with an excess of N 3 - ions in refluxing MeOH has led to the azido-bridged product [Ni13(N3)6(O2CMe)8(btaO)12(MeOH)10] (2), in which the spin frustration observed in 1 seems to disappear.

The employment of di-2-pyridyl ketone, (py)2CO, in manganese(II) benzoate chemistry is reported. The syntheses, crystal structures and spectroscopic (IR, EPR) characterization are described for [ Mn 3 II (O2CPh)6{(py)2CO}2] (1), [ Mn 3 II (O2CPh)6{(py)2CO}2] · 2MeCN (2 · 2MeCN) and [ Mn 4 II (O2CPh)4{(py)2C(OH)O}4] (3), where (py)2C(OH)O− is the monoanion of the gem-diol form of (py)2CO. Variable-temperature, magnetic susceptibility studies on 3 have also been performed. Complexes 1 and 2 · 2MeCN are linkage isomers. The trinuclear molecules of both complexes have a linear structure, with one η1:η2:μ2 and two syn, syn- η1:η1:μ2 PhCO 2 - groups spanning each pair of MnII atoms. The terminal MnII atoms are each capped by one κ2N,N′ (py)2CO ligand in orange 1 and one κ2N,Ο (py)2CO molecule in the yellow isomer 2 · 2MeCN. The molecule of 3 has a cubane topology with the MnII centers and the deprotonated oxygen atoms from the η1:η3:η1:μ3 ligands occupying alternate vertices of the cube. A terminal monodentate PhCO 2 - group completes a distorted octahedral coordination at each MnII atom. The IR data are discussed in terms of the coordination modes of the ligands that are present in the complexes. The X-band EPR spectra of powdered 1 and 2 at 4 K indicate that the populated spin states exhibit a zero-field splitting, while the spectrum of 3 at 18 K is consistent with the presence of magnetically interacting MnII atoms in the solid state. The magnetic properties of 3 in the 300–5 K range have been modelled with two J values, which reveal weak antiferromagnetic interactions within the molecule. Some suggestions have been made concerning the great stability of complex 3.

The employment of the di-2-pyridyl ketone [ ( py ) 2 CO ] / PhCO 2 - / N 3 - ligand combination in copper(II) chemistry has provided access to the hexanuclear cluster [Cu6(O2CPh)4(N3)2{(py)2CO2}2{(py)2C(OH)O}2] (1), and the coordination polymers [Cu4(O2CPh)2(N3)4{(py)2C(OMe)O}2]n (2) and [Cu2(O2CPh)(N3)2{(py)2C(OMe)O}]n (3). The structural type (cluster versus polymer) depends on the reaction solvent. Complex 1 has a [CuII6(μ3-OR′′)2(μ-OR′′)4]6+ core based on a central defective cubane unit and two additional CuII atoms across the missing edges. Complex 2 consists of zig-zag chains and complex 3 consists of extended 2D networks that adopt the herringbone architecture which is not based on T-shaped nodes. Cluster 1 is antiferromagnetically coupled with an S = 0 ground state.

The reactions of methyl 2-pyridyl ketone oxime, (py)C(Me)NOH, with MSO 4 · x H 2 O (M = Zn, x = 7; M = Cd, x = 8/3), in the absence of an external base, have been investigated. The synthetic study has led to the two new complexes [Zn(SO 4 ){(py)C(Me)NOH}(H 2 O) 3 ] · H 2 O ( 1 · H 2 O) and [Zn 2 (SO 4 ) 2 {(py)C(Me)NOH} 4 ] · (py)C(Me)NOH [ 2 · (py)C(Me)NOH], and the coordination polymer [Cd(SO 4 ){(py)C(Me)NOH}(H 2 O)] n · [Cd(SO 4 ){(py)C(Me)NOH}(H 2 O) 2 ] n ( 3 ). In the three complexes the organic ligand chelates through its nitrogen atoms. The sulfate anion in 1 · H 2 O is monodentate; the complex molecule is the mer isomer considering the positions of the aqua ligands. The Zn II centers in 2 · (py)C(Me)NOH are bridged by two syn, anti η 1 :η 1 :μ 2 cis – cis – trans disposition of the coordinated sulfate oxygen, pyridyl nitrogen and oxime nitrogens, respectively. The molecular structure of 3 is unique consisting of two different linear and ladder – type chains. π–π stacking interactions and/or hydrogen bonds lead to the formation of interesting supramolecular architectures in the three complexes. The thermal decomposition of complex 3 has been studied. Characteristic vibrational (IR, Raman) bands are discussed in terms of the nature of bonding and the structures of the three complexes.

Two new mononuclear peroxo complexes of tungsten of the formula (gu) 2 [WO 2 (O 2 ) 2 ] ( 1 ) and (gu)[WO(O 2 ) 2 (quin-2-c)] ( 2a ) (where gu + = guanidinium ion, CN 3 H 6 + and quin-2-c = quinoline-2-carboxylate ion) have been synthesized and characterized by elemental analysis, infrared, Raman, UV–visible and 1 H NMR spectroscopies. The crystal structure of (gu)[WO(O 2 ) 2 (quin-2-c)] · H 2 O ( 2b) determined by X-ray diffraction indicates that the side-on peroxo groups and the bidentate quinaldate ligand bind the W(VI) centre leading to an hepta coordination mode. The guanidinium ion occurring as a counterion and the hydrogen-bound interactions stabilize the complexes. The in vitro insulin-mimetic effect of the complexes has been evaluated by the inhibitory effect on free fatty acid release in isolated fat adipocytes treated with epinephrine. Moreover the niobate analogues, synthesized and characterized previously, (gu) 3 [Nb(O 2 ) 4 ] and (gu) 2 [Nb(O 2 ) 3 (quin-2-c)] · H 2 O have been tested for the insulin-like activity.

The chemistry of 1-hydroxybenzotriazole (btaOH) with the group 12 metal ions Zn(II) and Cd(II) resulted in the 1D coordination polymer [Zn(btaO)2]n (1) and the mononuclear complex [Cd(btaO)2(H2O)4] · 3H2O (2 · 3H2O), respectively. Polymer 1 forms double-stranded chains which are further supported by weak C–H⋯O hydrogen bonds resulting in a pcu (primitive cubic) rod packing. The mononuclear complexes of 2 form undulating hydrogen bonded layers while the lattice water molecules form 1D hydrogen bonded tapes, comprising 4- and 6-membered rings, within the layers and bridge them to the third dimension. The thermal and optical properties of both compounds are presented. IR data are discussed in terms of the chemical composition of the compounds and the coordination mode of btaO−.

The unsymmetrical complexes Pd(dpedt)(dddt), Pt(dpedt)(dddt), Pd(dpedt)(dmit), and Au(dpedt)- (dddt) (where dpedt is diphenyl-ethylenedithiolate, dddt is 5,6-dihydro-1,4-dithin-2,3-dithiolate and dmit is 1,3-dithiol-2-thione-4,5-dithiolate) were prepared and characterized. The study of their chemical and electrochemical behavior showed that they are stable in air and could be candidate materials for fabrication of field-effect transistors and other devices.

The unsymmetrical complexes Ni(tmedt)(dddt), Ni(dpedt)(dddt), Ni(tmedt)(dmit), and Ni(dpedt)(dmio) (where tmedt is trimethylene-ethylenedithiolate, dddt is 5,6-dihydro-1,4-dithin-2,3-dithiolate, dmit is 1,3-dithiol-2-thione-4,5-dithiolate, dpedt is diphenyl-ethylenedithiolate, and dmio is 1,3-dithiol-2-one-4,5-dithiolate) were prepared and their structural and physical properties investigated. The results were compared with those obtained from similar unsymmetrical and the corresponding symmetrical complexes. The new complexes were found to be stable in air and exhibit the necessary structural and physical properties in order to be candidate materials for optical and electronic devices.

The novel heteroleptic complex (gu)2[Nb(O2)3(quin-2-c)] · H2O (1) has been prepared by substituting a peroxo group by quinoline-2-carboxylate ion in the homoleptic complex (gu)3[Nb(O2)4] (2) in the presence of an excess of hydrogen peroxide in aqueous medium (gu+ = CN 3 H 6 + ; quin-2-c = quinoline-2-carboxylate ion). The complexes contain the highly symmetric and planar guanidinium ion as a counter-ion, which exhibits high stability and an extended hydrogen bonding pattern. The crystal structure and the spectral characterization of (gu)2[Nb(O2)3(quin-2-c)] · H2O have been determined. The ground electronic structure of the complex has been calculated with the density functional theory (DFT) method, and TD-DFT calculations have been employed to interpret the UV–Vis transitions. Compilation of the experimental and theoretical results may permit us to produce additional information about binding and catalytic reactivity.