Quantum tunneling in a three dimensional network of exchange coupled single-molecule magnets

A Mn4 single-molecule magnet (SMM) is used to show that quantum tunneling of magnetization (QTM) is not suppressed by moderate three dimensional exchange coupling between molecules. Instead, it leads to an exchange bias of the quantum resonances which allows precise measurements of the effective exchange coupling that is mainly due to weak intermolecular hydrogen bounds. The magnetization versus applied field was recorded on single crystals of [Mn4]2 using an array of micro-SQUIDs. The step fine structure was studied via minor hysteresis loops.Comment: 4 pages, 4 figure

Amalan Etika Kerja Dalam Perkhidmatan Awam Malaysia : Satu Kajian di Kementerian Pembangunan Usahawan dan Koperasi Malaysia

The objectives of this study is to determine the level of work ethic among the employees of the Ministry of Entrepreneur and Cooperative Development (MECD) and also to determine whether there are significant difference in work ethic characteristics among the MECD employees based on demographic variables namely gender, age, marital status and educational level as well as work variables namely job category, income and tenure of service. This study was conducted on a sample of 187 MECD employees using a 73-item questionnaire to measure all 12 pillars of The Twelve Pillars Work Ethic. T-test, one-way ANOVA test and Post HOC Tukey HSD test were used in the analysis to test whether there are significant difference in work ethic characteristics based on demographic and work variables among the MECD employees. The empirical results indicate that the level of work ethic among the MECD employees are good with a mean score of 3.89. Results further reveal that MECD work ethic characteristics differs significantly across gender, age, educational level, job category, income and tenure of service whereas there is no difference based on marital status. The findings have theoritical implications towards a better understanding of the relationship between demographic variables as well as work variables and work ethic. It is also hope that the findings of this study could assist the MECD management formulate sound strategies to improve the present programs and to implement new programs towards enhancing the work ethic of MECD employees

On Predicting Mössbauer Parameters of Iron-Containing Molecules with Density-Functional Theory

The performance of six frequently used density functional theory (DFT) methods (RPBE, OLYP, TPSS, B3LYP, B3LYP*, and TPSSh) in the prediction of Mössbauer isomer shifts(δ) and quadrupole splittings (ΔEQ) is studied for an extended and diverse set of Fe complexes. In addition to the influence of the applied density functional and the type of the basis set, the effect of the environment of the molecule, approximated with the conducting-like screening solvation model (COSMO) on the computed Mössbauer parameters, is also investigated. For the isomer shifts the COSMO-B3LYP method is found to provide accurate δ values for all 66 investigated complexes, with a mean absolute error (MAE) of 0.05 mm s–1 and a maximum deviation of 0.12 mm s–1. Obtaining accurate ΔEQ values presents a bigger challenge; however, with the selection of an appropriate DFT method, a reasonable agreement can be achieved between experiment and theory. Identifying the various chemical classes of compounds that need different treatment allowed us to construct a recipe for ΔEQ calculations; the application of this approach yields a MAE of 0.12 mm s–1 (7% error) and a maximum deviation of 0.55 mm s–1 (17% error). This accuracy should be sufficient for most chemical problems that concern Fe complexes. Furthermore, the reliability of the DFT approach is verified by extending the investigation to chemically relevant case studies which include geometric isomerism, phase transitions induced by variations of the electronic structure (e.g., spin crossover and inversion of the orbital ground state), and the description of electronically degenerate triplet and quintet states. Finally, the immense and often unexploited potential of utilizing the sign of the ΔEQ in characterizing distortions or in identifying the appropriate electronic state at the assignment of the spectral lines is also shown

DyIII- and YbIII -curcuminoid compounds: Original fluorescent single-ion magnet and magnetic near-IR luminescent species

The multifunctional behavior of two mononuclear lanthanide compounds attached to a curcuminoid called 9 Accm has been investigated. The results show that [Dy(9 Accm) 2(NO 3)(dmf) 2] Yb(9 Accm) 3(py)] behaves as a single-ion magnet and that both compounds display luminescent responses and exhibit affinity for graphite surfaces. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.We thank the MICINN (CTQ2009–06959/BQU and CTQ2009–08795) for financial support.Peer Reviewe

Fragmentation of the (Cyclam‐acetato)iron Azide Cation in the Gas Phase

Mass spectrometry is used to investigate the fragmentation of the ligated azidoiron cation [(cyclam‐acetato)Fe(N3)]+, which is accessible in the gas phase by electrospray ionization of a solution of its hexafluorophosphate salt in methanol/water. Upon collisional activation, mass‐selected [(cyclam‐acetato)Fe(N3)]+ undergoes competing loss of dinitrogen or HN3 as the prevailing fragmentations. The former dissociation pathway is investigated in detail in order to determine whether or not the free, high‐valent iron nitride [(cyclam‐acetato)FeN]+ is formed. The evidence obtained indeed supports the formation of the iron nitride species as an intermediate, although the long‐lived ion sampled after mass selection may also have undergone further rearrangements

Imidazole-imidazole stacking in some inorganic complexes

Reaction of CuCl2 center dot 2H(2)O with the 1:1 condensate (L) of 2-(2-aminoethyl) pyridine and 1-methyl-2-imidazolecarboxaldehyde in methanol yields monomeric CuLCl2 center dot H2O (1). Recrystallisation of 1 from aqueous methanol medium containing excess of PF6- affords the 1D coordination polymer [CuLCl](n)(PF6)(n) (2). A chloride bridge results in the coordination polymer. A face-to-face interaction is observed between the imidazole rings in 2. The interaction influences the structure and magnetic properties of 2 markedly. The complex 2 is ferromagnetic with a J value of 1.79 +/- 0.01 cm (1). The imidazole fragments in 2 are coordinated to the metal. In mononuclear [HgL2 ''](ClO4)(2), where L '' is the 1:2 condensate of ethylenediamine and 1-methyl-2-imidazolecarboxaldehyde, the imidazolyl moieties are not under the direct influence of the metal. Here the imidazole-imidazole interaction is angular and more distant. (C) 2009 Elsevier B.V. All rights reserved

Copper Curcuminoids Containing Anthracene Groups: Fluorescent Molecules with Cytotoxic Activity

The coordination chemistry of the new curcuminoid ligand, 1,7-(di-9-anthracene-1,6-heptadiene-3,5-dione), abbreviated 9Accm has been studied, resulting in two new copper-9Accm compounds. Compound 1, [Cu(phen)Cl(9Accm)], was synthesized by reacting 9Accm with [Cu(phen)Cl2] in a 1:1 ratio (M:L) and compound 2, [Cu(9Accm)2], was prepared from Cu(OAc)2 and 9Accm (1:2). UV−vis, electron paramagnetic resonance (EPR), and superconducting quantum interference device (SQUID) measurements were some of the techniques employed to portray these species; studies on single crystals of free 9Accm, [Cu(phen)Cl(9Accm)] and [Cu(9Accm)2(py)] provided detailed structural information about compounds 1 and 2·py, being the first two copper-curcuminoids crystallographically described. In addition the antitumor activity of the new compounds was studied and compared with free 9Accm for a number of human tumor cells. To provide more insight on the mode of action of these compounds under biological conditions, additional experiments were accomplished, including studies on the nature of their interactions with calf thymus DNA by UV−vis titration and Circular Dichroism. These experiments together with DNA-binding studies indicate electrostatic interactions between some of these species and the double helix, pointing out the weak nature of the interaction of the compounds with CT-DNA. The intrinsic fluorescence of the free ligand and both copper compounds provided valuable information over the cellular process and therefore, fluorescence microscopy studies were performed using a human osteosarcoma cell line. Studies in vitro using this technique suggest that the action of these molecules seems to occur outside the nuclei.The authors thank the Ministerio de Educación y Ciencia (CTQ2009-06959/BQU) and ICREA (Institut Català de Recerca i Estudis Avancats) for the financial support.Peer Reviewe