Spin crossover in a vacuum-deposited submonolayer of a molecular iron(II) complex

Spin-state switching of transition-metal complexes (spin crossover) is sensitive to a variety of tiny perturbations. It is often found to be suppressed for molecules directly adsorbed on solid surfaces. We present X-ray absorption spectroscopy measurements of a submonolayer of [FeII(NCS)2L] (L: 1-{6-[1,1-di(pyridin-2-yl)ethyl]-pyridin-2-yl}-N,N-dimethylmethanamine) deposited on a highly oriented pyrolytic graphite substrate in ultrahigh vacuum. These molecules undergo a thermally induced, fully reversible, gradual spin crossover with a transition temperature of T1/2 = 235(6) K and a transition width of ΔT80 = 115(8) K. Our results show that by using a carbon- based substrate the pin-crossover behavior can be preserved even for molecules that are in direct contact with a solid surface

Electrical Actuation of a DNA Origami Nanolever on an Electrode

Development of electrically powered DNA origami nanomachines requires effective means to actuate moving origami parts by externally applied electric fields. We demonstrate how origami nanolevers on an electrode can be manipulated (switched) at high frequency by alternating voltages. Orientation switching is long-time stable and can be induced by applying low voltages of 200 mV. The mechanical response time of a 100 nm long origami lever to an applied voltage step is less than 100 μs, allowing dynamic control of the induced motion. Moreover, through voltage assisted capture, origamis can be immobilized from folding solution without purification, even in the presence of excess staple strands. The results establish a way for interfacing and controlling DNA origamis with standard electronics, and enable their use as moving parts in electro-mechanical nanodevices

Pentanuclear Heterometallic {Ni₂Ln₃} (Ln = Gd, Dy, Tb, Ho) Assemblies. Single-Molecule Magnet Behavior and Multistep Relaxation in the Dysprosium Derivative

The reaction between Ln­(III) chloride and NiCl₂·4H₂O salts in presence of a multidentate sterically unencumbered ligand, (<i>E</i>)-2,2′-(2-hydroxy-3-((2-hydroxy­phenyl­imino)­methyl)-5-methyl­benzyl­azanediyl)­diethanol (<b>LH</b>_<b>4</b>) leads to the synthesis of four isostructural pentanuclear hetereometallic complexes [Ni₂Dy₃(LH)₄]Cl (<b>1</b>), [Ni₂Gd₃(LH)₄]Cl (<b>2</b>), [Ni₂Tb₃(LH)₃(LH₂)]­Cl₂ (<b>3</b>), [Ni₂ Ho₃ (LH)₃ (LH₂)]­Cl₂ (<b>4</b>) with unprecedented topology. Here the two compounds <b>1</b> are <b>2</b> are monocationic and crystallize in chiral space group, <i>P</i>2₁2₁2₁ whereas compounds <b>3</b> and <b>4</b> are dicationic and crystallize in achiral space group <i>P</i>2₁/<i>n</i>. The total metal framework, {Ni₂Ln₃} unit is held by four triply deprotonated ligands [LH]^3– in <b>1</b> and <b>2</b> whereas in case of <b>3</b> and <b>4</b> three triply deprotonated [LH]^3– and one doubly deprotonated [LH₂]^2– ligands are involved. In these complexes both the lanthanide ions and the nickel­(II) ions are doubly bridged and the bridging is composed of oxygen atoms derived from either phenolate or ethoxide groups. The analysis of SQUID measurements reveal a high magnetic ground state and a slow relaxation of the magnetization with two relaxation regimes for <b>1</b>. For the thermally activated regime we found an effective energy barrier of <i>U</i>_eff = 85 K. Micro Hall probe loop measurements directly proof the single-molecule magnet (SMM) nature of <b>1</b> with a blocking temperature of <i>T</i>_B = 3 K and an open hysteresis for sweep rates faster than 50 mT/s

Pentanuclear Heterometallic {Ni₂Ln₃} (Ln = Gd, Dy, Tb, Ho) Assemblies. Single-Molecule Magnet Behavior and Multistep Relaxation in the Dysprosium Derivative

The reaction between Ln­(III) chloride and NiCl₂·4H₂O salts in presence of a multidentate sterically unencumbered ligand, (<i>E</i>)-2,2′-(2-hydroxy-3-((2-hydroxy­phenyl­imino)­methyl)-5-methyl­benzyl­azanediyl)­diethanol (<b>LH</b>_<b>4</b>) leads to the synthesis of four isostructural pentanuclear hetereometallic complexes [Ni₂Dy₃(LH)₄]Cl (<b>1</b>), [Ni₂Gd₃(LH)₄]Cl (<b>2</b>), [Ni₂Tb₃(LH)₃(LH₂)]­Cl₂ (<b>3</b>), [Ni₂ Ho₃ (LH)₃ (LH₂)]­Cl₂ (<b>4</b>) with unprecedented topology. Here the two compounds <b>1</b> are <b>2</b> are monocationic and crystallize in chiral space group, <i>P</i>2₁2₁2₁ whereas compounds <b>3</b> and <b>4</b> are dicationic and crystallize in achiral space group <i>P</i>2₁/<i>n</i>. The total metal framework, {Ni₂Ln₃} unit is held by four triply deprotonated ligands [LH]^3– in <b>1</b> and <b>2</b> whereas in case of <b>3</b> and <b>4</b> three triply deprotonated [LH]^3– and one doubly deprotonated [LH₂]^2– ligands are involved. In these complexes both the lanthanide ions and the nickel­(II) ions are doubly bridged and the bridging is composed of oxygen atoms derived from either phenolate or ethoxide groups. The analysis of SQUID measurements reveal a high magnetic ground state and a slow relaxation of the magnetization with two relaxation regimes for <b>1</b>. For the thermally activated regime we found an effective energy barrier of <i>U</i>_eff = 85 K. Micro Hall probe loop measurements directly proof the single-molecule magnet (SMM) nature of <b>1</b> with a blocking temperature of <i>T</i>_B = 3 K and an open hysteresis for sweep rates faster than 50 mT/s

Spin Crossover in a Vacuum-Deposited Submonolayer of a Molecular Iron(II) Complex

Spin-state switching of transition-metal complexes (spin crossover) is sensitive to a variety of tiny perturbations. It is often found to be suppressed for molecules directly adsorbed on solid surfaces. We present X-ray absorption spectroscopy measurements of a submonolayer of [Fe^II(NCS)₂L] (L: 1-{6-[1,1-di­(pyridin-2-yl)­ethyl]-pyridin-2-yl}-<i>N</i>,<i>N</i>-dimethylmethanamine) deposited on a highly oriented pyrolytic graphite substrate in ultrahigh vacuum. These molecules undergo a thermally induced, fully reversible, gradual spin crossover with a transition temperature of <i>T</i>_1/2 = 235(6) K and a transition width of Δ<i>T</i>₈₀ = 115(8) K. Our results show that by using a carbon-based substrate the spin-crossover behavior can be preserved even for molecules that are in direct contact with a solid surface