2 research outputs found
New Series of Triply Bridged Dinuclear Cu(II) Compounds: Synthesis, Crystal Structure, Magnetic Properties, and Theoretical Study
Five new triply bridged dinuclear Cu(II) compounds have been synthesized, and their magnetic properties have been measured and characterized. The magnetic coupling constants (<i>J</i>) of these compounds plus a previously structurally characterized compound of the same type have been derived by appropriate fitting of the experimentally measured molar susceptibility variation with the temperature. Two of the compounds are ferromagnetically coupled, and three are antiferromagnetically coupled with <i>J</i> values in the [+150, â40] cm<sup>â1</sup> range. The validity of the structural aggregate Addisonâs parameter as a qualitative magneto-structural correlation is confirmed. The origin of the magnetic interactions and the magnitude of the magnetic coupling have been analyzed by means of density functional theory-based calculations using a variety of state of the art exchange-correlation potentials. It is shown that the long-range separated LC-ÏPBE provides the overall best agreement with experiment for this family as well as for a set of previously reported hetero triply bridged dinuclear Cu(II) compounds, especially for ferromagnetic systems
Conformationally Gated Charge Transfer in DNA Three-Way Junctions
Molecular structures that direct
charge transport in two or three
dimensions possess some of the essential functionality of electrical
switches and gates. We use theory, modeling, and simulation to explore
the conformational dynamics of DNA three-way junctions (TWJs) that
may control the flow of charge through these structures. Molecular
dynamics simulations and quantum calculations indicate that DNA TWJs
undergo dynamic interconversion among âwell stackedâ
conformations on the time scale of nanoseconds, a feature that makes
the junctions very different from linear DNA duplexes. The studies
further indicate that this conformational gating would control charge
flow through these TWJs, distinguishing them from conventional (larger
size scale) gated devices. Simulations also find that structures with
polyethylene glycol linking groups (âextendersâ) lock
conformations that favor CT for 25 ns or more. The simulations explain
the kinetics observed experimentally in TWJs and rationalize their
transport properties compared with double-stranded DNA