Reactivity of Thiolate and Hydrosulfide with a Mononuclear {FeNO}7 Complex Featuring a Very High N-O Stretching Frequency.

Synthesis, characterization, electronic structure, and redox reactions of a mononuclear {FeNO}7 complex with a very high N-O stretching frequency in solution are presented. Nitrosylation of [(LKP)Fe(DMF)]2+ (1) (LKP = tris((1-methyl-4,5-diphenyl-1H-imidazol-2-yl)methyl)amine) produced a five-coordinate {FeNO}7 complex, [(LKP)Fe(NO)]2+ (2). While complex 2 could accommodate an additional water molecule to generate a six-coordinate {FeNO}7 complex, [(LKP)Fe(NO)(H2O)]2+ (3), the coordinated H2O in 3 dissociates to generate 2 in solution. The molecular structure of 2 features a nearly linear Fe-N-O unit with an Fe-N distance of 1.744(4) Å, N-O distance of 1.162(5) Å, and

Role of Labile Methanol on the Bio-inspired Catalytic Activity of a Zn(II)-based Compound: An Experimental and Theoretical Investigation.

Two Zn(II)-based compounds, [Zn2 L1 (OAc)3 (MeOH)] (1) and [Zn2 L2 (OAc)3 ]n (2), have been reported where HL1 is (E)-4-bromo-2-methoxy-6-(((2-morpholino ethyl)imino) methyl)phenol and HL2 is (E)-4-bromo-2-methoxy-6-(((2-(piperazine-1-yle)ethyl)imino)methyl) phenol. Single-crystal X-ray diffraction (SCXRD) analysis unveils vivid change in structural arrangements and dimensionality from 1 to 2 due to change in coordinated atom from oxygen to nitrogen of the ligands. SCXRD study shows that compound 1 is dinuclear but compound 2 has a 1-dimensional polymeric structure having helical chain. Structural diversity greatly influences the catalytic activity. Compound 1 acts as excellent catalyst for conversion of 3, 5-di-tert-butyl catechol (3, 5-DTBC) to 3, 5-di-tert-butylbenzoquinone (3, 5-DTBQ) with the turnover number (kcat ) value of 34.94 sec-1 . Further, compound 1 reveals phosphatase like activity for conversion of disodium salt of (4-nitrophenyl)-phosphate hexahydrate to p-nitrophenolate with the kcat value of 24.64 sec-1 . Interestingly, compound 2 does not show any catalytic activity. To correlate this distinctly different catalytic behavior of two compounds, DFT calculation was carried out. The calculation reveals that detachment of coordinated methanol from coordination sphere of zinc in compound 1 is energetically favourable which creates room for substrate binding, resulting in high catalytic activity. By contrast, in compound 2, detachment of piperazine or Zn-O of -COOH group is energetically unfavourable, resulting in no catalytic activity.

Synergistic Experimental and Theoretical Studies of Luminescent-Magnetic Ln2Zn6 Clusters.

The present work is part of our ongoing quest for developing functional inorganic complexes using unorthodox pyridyl-pyrazolyl-based ligands. Accordingly, we report herein the synthesis, characterization, and luminescence and magnetic properties of four 3d-4f mixed-metal complexes with a general core of Ln2Zn6 (Ln = Dy, Gd, Tb, and Eu). In stark contrast to the popular wisdom of using a compartmental ligand with separate islands of hard and soft coordinating sites for selective coordination, we have vindicated our approach of using a ligand with overcrowded N-coordinating sites that show equal efficiency with both 4f and 3d metals toward multinuclear cage-cluster formation. The encouraging red and green photolumiscent features of noncytotoxic Eu2Zn6 and Tb2Zn6 complexes along with their existence in nanoscale dimension have been exploited with live-cell confocal microscopy imaging of human breast adenocarcinoma (MCF7) cells. The magnetic features of the Dy2Zn6 complex confirm the single-molecule-magnet behavior with befitting frequency- and temperature-dependent out-of-phase signals along with an Ueff value of ∼5 K and a relaxation time of 8.52 × 10-6 s. The Gd2Zn6 complex, on the other hand, shows cryogenic magnetic refrigeration with an entropy change of 11.25 J kg-1 K-1 at a magnetic field of 7 T and at 2 K. Another important aspect of this work reflects the excellent agreement between the experimental results and theoretical calculations. The theoretical studies carried out using the broken-symmetry density functional theory, ORCA suite of programs, and MOLCAS calculations using the complete-active-space self-consistent-field method show an excellent synergism with the experimentally measured magnetic and spectroscopic data.

A Nd6 molecular butterfly: a unique all-in-one material for SMM, MCE and maiden photosensitized opto-electronic device fabrication.

Besides iron, ironically neodymium (Nd) is the most ubiquitously used metal for magnetic purposes, even among the lanthanides, when it comes to the field of molecular magnetism, yet it ranks among the least studied metals. However, strong apathy towards this magnetic lanthanide means that vital information will be missed, which is required for the advancement of the subject. Herein, we have successfully demonstrated the usefulness of a hexanuclear neodymium complex as a magnetic material, and also in electronic device fabrication. A {NdIII6} cage with an aesthetically pleasing butterfly topology was synthesized using a rather non-conventional N-rich pyridyl-pyrazolyl based ligand. The cage shows single molecule magnet (SMM) properties, with an effective energy barrier, Ueff, value of 3.4 K and relaxation time, τ0, of 3.1 × 10-4 s, originating from an unusual occurrence of metal centres with different coordination environments. Furthermore, magnetic studies reveal significant cyrogenic magnetic cooling, with a magnetic entropy change of 8.28 J kg-1 K-1 at 5 T and 3 K. To the best of our knowledge, the titular compound is the only example of a Nd-complex that exhibits concomitant magnetocaloric effect (MCE) and SMM properties. Complete active space self-consistent field (CASSCF) calculations were carried out to shed light on the origin of the magnetic anisotropy and magnetic relaxation of the compound. The same uniqueness is also true for the first electronic investigation carried out on the Nd complex. The maiden electronic device fabricated using the Nd complex shows an interesting intertwining of electronic and optical features, which contribute towards its improved photosensitized optoelectronic data.

Sodium-Stuffed Open-Framework Quaternary Chalcogenide Built with (Cu2Ga6S18)16- Ribbons Cross-Linked by Unusual Linear Cu(I) Pillars.

A quaternary compound, Na15Cu3Ga6S18, the first member in the A-Cu-Ga-S (A = alkali metal) series, has been synthesized from a solid-state metathesis reaction between Na6Ga2S6 and CuCl as well as from a combination of Na2S, Ga, Cu, and S. The compound crystallizes in a monoclinic crystal system, space group C2/c, and represents a unique open-framework structure with channels filled with eight crystallographically distinct Na ions. The anionic framework is built up of infinite chains of corner-shared GaS4 tetrahedra fused together by an edge-shared dimer of CuS4 tetrahedra forming one-dimensional ribbons of (Cu2Ga6S18)16-, which are cross-linked by linearly coordinated S-Cu-S linkages resulting in a three-dimensional network with tunnels filled with Na atoms. Optical band gap measurements show that the compound has a direct band gap of 3.00 eV that is in good agreement with the theoretical band gap derived from density functional theory calculations. Band structure calculations further indicate that the states near the Fermi level are dominated by tetrahedral Cu+(d) and S(p) states resulting from the antibonding interactions, while s-d hybridization is prevalent in linear Cu+ coordination. Ionic conductivity measurements show that the compound has a room-temperature Na ion conductivity of 2.72 × 10-5 mS/cm with an activation energy of 0.68 eV, which corroborates well the nudged elastic band calculations.

Ternary alkali ion thiogallates, A5GaS4 (A = Li and Na), with isolated tetrahedral building units and their ionic conductivities.

Two new ternary thiogallates in the A5GaS4 (A = Li (i) and Na (ii)) series have been synthesized for the first time employing a gas passing route using oxide precursors and a high temperature solid state route using stoichiometric combinations of elements, respectively. Li5GaS4 crystallizes in the P21/m space group and the structure is built up of layers of corner sharing tetrahedra of LiS4 and GaS4 stacked along the a-axis and the octahedrally coordinated Li ions residing in the interlayer space. Na5GaS4 crystallizes in the Pbca space group and the structure consists of isolated (GaS4)5- tetrahedra held together by charge balancing sodium ions in distorted tetrahedral and octahedral coordination geometries. Measurements of ionic conductivity of the compounds showed room temperature ionic conductivities of 1.8 × 10-7 and 4.0 × 10-7 S cm-1 with activation energies of 0.54 and 0.28 eV, respectively, for I and II. Density functional theory calculations show close agreement in structural parameters with the measured data and predict band gaps of 2.75 eV (I) and 2.70 eV (II). Single point hybrid functional calculations result in band gaps of 3.95 and 3.65 eV correspondingly, in better agreement with the experimental value of ∼4.1 eV for both. Bond valence energy landscape maps suggest the absence of any suitable diffusion path for Li in Li5GaS4. On the other hand, BVEL maps of Na5GaS4 confirm that the tetrahedrally coordinated Na ions are responsible for ionic conduction, whereas the involvement of octahedrally coordinated Na ions in the conduction process could not be discerned.

Lanthanide clusters of phenanthroline containing a pyridine-pyrazole based ligand: magnetism and cell imaging.

In this contribution, we report the synthesis, characterization and luminescence-magnetic properties of Ln-clusters (Ln = Gd3+, Eu3+ and Tb3+) using a new pyridine-pyrazole functionalized ligand fitted with a chromophoric phenanthroline backbone. The unorthodox N-rich ligand forms isostructural trinuclear lanthanide complexes with a topology that closely resembles two interdigitating hairpins. The clusters crystallize in chiral space groups and also exhibit chirality for bulk samples, which were further confirmed using solid state CD spectra. Magnetic studies on the complexes reveal their interesting features while the Gd cluster shows a significant cryogenic magnetic cooling behaviour with a moderately high magnetic entropy change of -23.42 J kg-1 K-1 at 7 T and 2 K. On the other hand, Eu and Tb complexes exhibit interesting fluorescence properties. The compounds were subsequently used as fluorescent probes for the imaging of human breast adenocarcinoma (MCF7) cells. Live cell confocal microscopy images show that the complexes penetrate beyond the usual cytoplasm region and can be useful in imaging the nucleus region of MCF7 cells.

Naked Eye Cd2+ Ion Detection and Reversible Iodine Uptake by a Three-Dimensional Pillared-Layered Zn-MOF.

A novel metal-organic framework (MOF), [Zn2(tdca)2(bppd)2]·2DMF, has been synthesized solvothermally using the ligand thiophene-2,5-dicarboxylic acid (H2tdca), coligand N,N'-bis(4-pyridylmethylene)-1,4-benzenediamine (bppd), and Zn(NO3)2. Single crystal X-ray crystallography reveals that the titled MOF is a three-dimensional pillared-layered MOF. A layer is constituted by a Zn(tdca) unit, and the layers are stabilized by the long hydrocarbon coligand, bppd, which acts as a pillar. A rectangular pore size of 11.42 × 8.12 Å2 is found in the framework. The porous framework is found to be an excellent fluorescence sensor for the detection of toxic Cd2+ ion. The sensor shows high selectivity and sensitivity and a quick response toward Cd2+. The synthesized MOF is able to not only detect cadmium ions but also adsorb iodine in the gas phase. The MOF can adsorb ∼66% iodine, verified by thiosulfate-iodine titration and TG analysis. Adsorbed iodine can also be removed easily in acetonitrile as well as in n-hexane, which shows that iodine can be reversibly loaded as well as unloaded into the framework.

Structure and synthesis of copper-based Schiff base and reduced Schiff base complexes: a combined experimental and theoretical investigation of biomimetic catalytic activity.

Three copper(ii) complexes, [Cu(L1)(NCS)]n (1), [Cu(L1)(N3)]n (2) and [Cu(L2)(N3)] (3) were synthesized from one Schiff base ligand and one reduced Schiff base ligand, (E)-4-chloro-2-[(2-propylaminoethylimino)methyl]phenol (HL1) and 4-chloro-2-[(2-(propylaminoethylamino) methyl]phenol (HL2), respectively. All complexes were characterized by various physicochemical studies, such as FT-IR, UV-Vis, ESI-MS, EPR and single crystal X-ray diffraction. Complexes 1 and 2 have 1D polymeric chain-like structures bridging through thiocyanate and azide anions, whereas complex 3 has a mononuclear structure in the solid state. All the complexes are active towards mimicking two well-known proteins, phosphatase and phenoxazinone synthase, using the disodium salt of 4-nitrophenylphosphate (4-NPP) and 2-aminophenol (OAP) as the substrate in DMF medium. Complexes 2 and 3 show the highest activity towards phosphatase and phenoxazinone synthase activity with kcat values of 22.6 s-1 and 134.4 h-1, respectively. EPR studies confirmed that for complex 1, the OAP oxidation goes through the generation of an organic radical at g = 1.99, which is due to an imine radical formation, whereas the metal center redox pathway is followed for complex 3. Extensive DFT calculations have been performed for both catalytic studies to put forward the most probable mechanistic pathways.

Paradoxical design of a serendipitous pyrazolate bridging mode: a pragmatic strategy for inducing ineluctable ferromagnetic coupling.

In this contribution we have carried out a systematic magnetostructural investigation to establish a robust one-to-one correlation between the quasi-orthogonal bridging mode of a pyrazolate ring and ferromagnetic coupling. Generating a complex with an elusive quasi-orthogonal pyrazolate bridging is a challenging task but would ineluctably result in a ferromagnetic exchange pathway. Notwithstanding the rarity, we report herein a series of bis-pyrazolato copper complexes. We have successfully exploited a so-called hypothetical-deductive model on a particular set of ligand systems that forced the pyrazolate moiety to adopt an unusual bridging mode with the M-Npz-Npz-M torsion angles in the range from 49.7° to 72.8°. The corroborating variable temperature direct current (DC) magnetic susceptibility data unequivocally confirm the ferromagnetic coupling for the complexes with the torsion angles greater than 71.37°. Furthermore, the experimental results are in excellent agreement with theoretical calculations. Based on density functional theory (DFT) calculations, again a one-to-one correspondence is made between the ligand structure and magnetic behaviour. The diradical character (y0) of the complexes is correlated with the extent of bonding interactions between the Cu centers and hence, their ferromagnetic or antiferromagnetic nature. The broken symmetry (BS) calculations on the magnetically active molecular orbitals indicate the essential magnetic behaviour of the complexes, while the EPR g-tensor calculations confirm that dx2-y2 is the magnetic orbital.

A free-standing, self-healing multi-stimuli responsive gel showing cryogenic magnetic cooling.

A novel Fe(iii)-based gel was synthesized via the self-assembly of Fe(iii) and pyridine 2,6 dicarboxylic acid. The synthesized gel has remarkable mechanical strength as well as self-sustainability. The metallogel also has thixotropic as well as self-healing properties. The metallogel shows amazing colourimetric NH3 sensing with unique gel-to-gel transformation. Magnetic studies on the as-synthesized gel reveal significant cryogenic magnetic cooling behavior. Last but not least, to the best of our knowledge, this would be the first case where MCE is investigated for any reported metallogel.

Synthesis of Mn3O4 nanozymes from structurally characterized phenoxazinone synthase models based on manganese(iii) Schiff base complexes.

Three mononuclear and one hexanuclear manganese(iii) complexes, [Mn(L)(H2O)2]·Cl (1), [Mn(L)(H2O)2]·Br (2), [Mn(L)(H2O)2]·NO3 (3), and [Mn6(L)6(NCS)6] (4), have been synthesized using a Schiff-base ligand, namely (E)-2-((3-(2-hydroxyethylamino)propylimino)methyl)phenol (H2L), and structurally characterized by the usual physicochemical techniques such as UV-Vis, FT-IR, ESI-MS, EPR and single crystal XRD. The structure of complex 4 is unique among all four complexes as the sixth coordination position of manganese is fulfilled by the oxygen atom of a neighbouring unit by covalent interaction. The phenoxazinone synthase like activity of all four complexes has been thoroughly investigated using three different substrates, o-aminophenol (OAP), 2-amino-4-methylphenol (MAP) and 3-amino-4-hydroxybenzoic acid (CAP). All complexes were found to be active towards catalysis and complex 4 showed the highest activity. The EPR study reveals that the oxidative dimerization of the substrates occurred through metal centered redox participation rather than a radical formation pathway. The experimental observations have been supported by DFT calculations to put forward the most probable mechanistic pathways operating in the catalytic cycle. Moreover, Mn3O4 nanoparticles (NPs) having two different morphologies have been synthesized using complexes 1 and complex 4 simply by calcination, respectively, with the aim to prepare nanozymes. These two synthesized NPs were also able to show phenoxazinone synthase like activity and thus complexes 1 and 4 can be claimed as precursors of nanozymes.

Correction to "Temperature-Induced Single-Crystal-to-Single-Crystal Transformations with Consequential Changes in the Magnetic Properties of Fe(III) Complexes".

[This corrects the article DOI: 10.1021/acsomega.8b03400.].

Exploration of catecholase-like activity of a series of magnetically coupled transition metal complexes of Mn, Co and Ni: new insights into the solution state behavior of Mn complexes.

A series of tri-nuclear complexes of general formula [M3L2(OAc)4], where M = Mn (1), Co (2) and Ni (3), (HL = (E)-4-bromo-2-(((2-morpholinoethyl)imino)methyl)phenol), have been synthesized. Single crystal X-ray crystallography reveals that each molecule contains three metal ions which are bridged by four acetate moieties. In the solution phase, the complexes are present as mononuclear species. Amongst them, the manganese atom of complex 1 switches its oxidation state from +ii to +iii with time, as confirmed by time dependent UV-Vis and EPR spectroscopic techniques. Furthermore, complex 1 with Mn in both oxidation states can oxidise 3,5-DTBC to 3,5-DTBQ through the ligand centred radical formation pathway. It is remarkable that complex 1 in the MnII oxidation state shows an abnormally high rate constant value in the oxidation of 3,5-DTBC to 3,5-DTBQ. This difference in rate constant values for catechol oxidation reaction by complex 1 can be explained by considering the binding constant value of catechol with MnII and MnIII respectively from experimental and theoretical aspects. Similar to complex 1, complexes 2 and 3 also catalyse catechol oxidation following ligand centred imine radical formation pathways. Furthermore, magnetic properties of all the complexes were explored. DC magnetic susceptibility studies of complexes 1 and 2 revealed that in both the complexes the metal centres are antiferromagnetically coupled with adjacent metal centres, whereas in the case of complex 3, weak ferromagnetic interaction occurs between the neighbouring NiII centres at low temperature.

Temperature-Induced Single-Crystal-to-Single-Crystal Transformations with Consequential Changes in the Magnetic Properties of Fe(III) Complexes.

The present article deals with an one-to-one structure-property correspondence of a dinuclear iron complex, [Dipic(H2O)FeOH]2·H2O (1) (Dipic = pyridine-2,6-dicarboxylic acid). Variable-temperature X-ray single-crystal structural analysis confirms a phase transition of complex 1 to complex 2 ([Dipic(H2O)FeOH]2) at 120 °C. Further, single-crystal-to-single-crystal (SCSC) transformation was monitored by temperature-dependent single crystal X-ray diffraction, powder X-ray diffraction, time-dependent Fourier-transform infrared spectroscopy, and differential scanning calorimetry. SCSC transformation brings the change in space group of single crystal. Complex 1 crystallizes in the C2/c space group, whereas complex 2 crystallizes in the Pi̅ space group. SCSC transformation brings the change in packing diagram as well. Complex 1 shows two-dimensional network through H-bonding, whereas the packing diagram of complex 2 shows a zigzag-like arrangement. Phase transformation not only fetches structural changes but also in the magnetic properties. Difference in Fe-O-Fe bond angles of two complexes creates notable variation in their antiferromagnetic interactions with adjacent metal centers.

Multifunctional Properties of a 1D Helical Co(II) Coordination Polymer: Toward Single-Ion Magnetic Behavior and Efficient Dye Degradation.

This contribution deals with the synthesis and utilization of a new pyrazole-based unsymmetrical ligand, 3-(3-carboxyphenyl)-1H-pyrazole-5-carboxylic acid (H2CPCA), for generating multifunctional materials. The reaction with the Co(II) salt in the presence of a co-ligand 2,9-dimethyl phenanthroline (dmphen) results in the formation of the helical compound {[Co2(dmphen)2(CPCA)2]DMF} n (1). However, two isostructural monomeric complexes are formed {[M(HCPCA)2(H2O)2], M = Co(II), (2) and Mn(II) (3)} when reactions were carried out in the absence of dmphen. Compound 1 shows some highly encouraging single-ion magnetic (SIM) properties. Detailed magnetic studies unveil slow relaxation of magnetization of compound 1, driven by the higher magnetic anisotropy of the cobalt ion, with the energy barrier of ∼9.2 K and relaxation time of 9.1 × 10-5 s, suggesting a SIM behavior. Moreover, UV-vis and fluorescence studies confirm the selective dye degradation of compound 1 with methylene blue both in the presence and absence of H2O2, with the remarkable degradation efficiency of ∼98 and ∼82%, respectively.

Magnetically Frustrated Quaternary Chalcogenides with Interpenetrating Diamond Lattices.

A series of quaternary sulfides of the composition Na3MGaS4 (M = Mn (1), Fe (2), and Co (3)) have been synthesized in sealed quartz ampules. In these compounds, divalent transition metal and Ga occupy the same crystallographic site in the Ga-S network, forming a supertetrahedral, T2 (adamantane) unit, through the corner-sharing of four M/GaS4 tetrahedra. The corner sulfur atoms of the T2 clusters are further connected to similar T2 units to form an open continuous three-dimensional (3D) anionic framework of composition {[Ga2M2S8]n}6-. The framework resembles a zinc blende structure type if each T2 cluster is considered as a single tetrahedron and two such frameworks are intertwined to generate channels wherein reside the extra-framework Na+ ions. Placement of transition metals (Mn or Fe or Co) in the corner of a perfect supertetrahedron, adamantane building unit, generates an ideal lattice for geometrical magnetic frustration, which, on dilution with nonmagnetic metal (Ga), creates an ideal case for random frustration. Preliminary magnetic measurements indicate high negative values of the Weiss constant (-200 to -400 K) and the absence of any magnetic ordering, reinforcing the presence of magnetic frustration in all of these compounds.

Crystal structure of a chloride-bridged copper(II) dimer: piperazine-1,4-dium bis-(di-µ-chlorido-bis[(4-carboxypyridine-2-carboxyl-ato-κ2N,O2)chlorido-cuprate(II)].

Crystals of a new dimeric chloride-bridged cuprate(II) derived from pyridine-2,4-di-carb-oxy-lic acid were obtained solvothermally in the presence of piperazine and hydro-chloric acid. The crystal structure determination of the title salt, (C4H12N2)[Cu2(C7H4NO4)2Cl4], revealed one of the carboxyl groups of the original pyridine-2,4-di-carb-oxy-lic acid ligand to be protonated, whereas the other is deprotonated and binds together with the pyridine N atom to the CuII atom. The coordination environment of the CuII atom is distorted square-pyramidal. One of the chloride ligands bridges two metal cations to form a centrosymmetric dimer with two different Cu-Cl distances of 2.2632 (8) and 2.7853 (8) Å, whereby the longer distance is associated with the apical ligand. The remaining chloride ligand is terminal at one of the basal positions, with a distance of 2.2272 (9) Å. In the crystal, the dimers are linked by inter-molecular O-H⋯O hydrogen bonds, together with N-H⋯O and N-H⋯Cl inter-actions involving the centrosymmetric organic cation, into a three-dimensional supra-molecular network. Further but weaker C-H⋯O and C-H⋯Cl inter-actions consolidate the packing.

Synthesis, structure, magnetic and biological activity studies of bis-hydrazone derived Cu(ii) and Co(ii) coordination compounds.

Four coordination compounds of formulae [Cu(II)2(H2L(1))(HL(1))](ClO4)3·H2O (1), [Cu(II)2(H2L(2))(CH3OH)2](ClO4)2·2CH3OH (2), [Co(II)2(H2L(1))2](ClO4)4 (3) and [Co(II)2(H2L(2))2]·2H2O (4) were synthesized via self-assembly of succinohydrazone derived ligands (H2L(1) = N',N'-4-bis(2-pyridyl)succinohydrazide, H4L(2) = N',N'-4-bis(2-hydroxybenzylidene)succinohydrazide) and Cu(2+) and Co(2+) ions, respectively. The compounds were characterized by crystal structure determination, magnetic measurements and biological activities. Compounds 1, 3 and 4 have discrete double helicate structures, whereas compound 2 is a one-dimensional chain. Magnetic studies show antiferromagnetic exchange interactions in 2 with a J value of -67.1 cm(-1) and antiferromagnetic spin-canting in compound 3 originates through supramolecular H-bonding. For compound 3, a clear bifurcation was observed in zero field cooled (ZFC) and field cooled (FC) measurement at a temperature of 3.5 K and field of 0.1 T, implying long range magnetic ordering below this temperature. Interestingly, all of compounds 1-4 show significant changes in their absorption (hypo- and hyperchromism) in the presence of SS-DNA, inferring interaction between the compounds and DNA. In addition, compounds 1-4 significantly exhibited nuclease activities on both RNA and pUC19 plasmid DNA. Moreover, the nuclease activity was further enhanced in the presence of oxidant (H2O2) and suggests the possible role of reactive oxygen species in DNA nicking ability of compounds 1-4. Furthermore, compounds 1, 2 and 4 exhibited significant cytotoxicity against mammalian cancer cell lines (HeLa, A549 and MDAMB-231). In addition, our results from Annexin/PI staining and DNA fragmentation assays revealed that these compounds are capable of inducing apoptosis and have potential to act as anticancer drugs.

Metallic Ternary Telluride with Sphalerite Superstructure.

A new ternary compound with composition Cu5Sn2Te7 has been synthesized using the stoichiometric reaction of Cu, Sn, and Te. The compound crystallizes in C2 space group with unit cell parameters of a = 13.549(2) Å, b = 6.0521(11) Å, c = 9.568(2) Å, and ß = 98.121(2)°. Cu5Sn2Te7 is a superstructure of sphalerite and exhibits tetrahedral coordination of Cu, Sn, and Te atoms, containing a unique adamantane-like arrangement. The compound is formally mixed valent with a high electrical conductivity of 9.8 × 10(5) S m(-1) at 300 K and exhibits metallic behavior having p-type charge carriers as indicated from the positive Seebeck coefficient. Hall effect measurements further confirm holes as charge carriers with a carrier density of 1.39 × 10(21) cm(-3) and Hall mobility of 4.5 cm(2) V(-1) s(-1) at 300 K. The electronic band structure calculations indicate the presence of a finite density of states around the Fermi level and agree well with the p-type metallic conductivity. Band structure analysis suggests that the effective mass of the hole state is small and could be responsible for high electronic conductivity and Hall mobility. The high thermal conductivity of 15.1 W m(-1) K(-1) at 300 K coupled with the low Seebeck coefficient results in a poor thermoelectric figure of merit (ZT) for this compound. Theoretical calculations indicate that if Cu5Sn2Te7 is turned into a valence precise compound by substituting one Cu by a Zn, a semiconducting material, Cu4ZnSn2Te7, with a direct band gap of ∼ 0.5 eV can be obtained.