Author: Ko Yoneda

Precise Control and Consecutive Modulation of Spin Transition Temperature Using Chemical Migration in Porous Coordination Polymers

Precise control of spin transition temperature (T(c)) is one of the most important challenges in molecular magnetism. A Hofmann-type porous coordination polymer {Fe(pz)[Pt(II)(CN)(4)]} (1; pz = pyrazine) exhibited cooperative spin transition near room temperature (T(c)(up) = 304 K and T(c)(down) = 284 K) and its iodine adduct {Fe(pz)[Pt(II/IV)(CN)(4)(I)]} (1-I), prepared by oxidative addition of iodine to the open metal sites of Pt(II), raised the T(c) by 100 K. DSC and microscopic Raman spectra of a solid mixture of 1-I and 1 revealed that iodine migrated from 1-I to 1 through the grain boundary after heating above 398 K. We have succeeded in precisely controlling the iodine content of {Fe…

research product

Oxidative Addition of Halogens on Open Metal Sites in a Microporous Spin-Crossover Coordination Polymer

research product

Innentitelbild: Bidirectional Chemo&hyphen;Switching of Spin State in a Microporous Framework &lpar;Angew. Chem. 26&sol;2009&rpar;

Das chemische Schalten des Magnetismus in zwei Richtungen wurde in einem mikroporosen Koordinationspolymer mit Spin-Crossover-Einheiten beobachtet. M. Ohba, J. A. Real, S. Kitagawa und Mitarbeiter stellten in ihrer Zuschrift auf S. 4861 ff. magnetische Messungen vor, die belegen, dass die meisten Gastmolekule einen Ubergang des Netzwerks vom diamagnetischen Low-Spin- (rot) in den paramagnetischen High-Spin-Zustand (gelb) bewirken. Allein CS2 stabilisiert den Low-Spin-Zustand. Die induzierten Spinzustande werden auch nach Freisetzung der Gastspezies beibehalten.

research product

A Switchable Molecular Rotator: Neutron Spectroscopy Study on a Polymeric Spin-Crossover Compound

A quasielastic neutron scattering and solid-state 2H NMR spectroscopy study of the polymeric spin-crossover compound {Fe(pyrazine)[Pt(CN) 4]} shows that the switching of the rotation of a molecular fragment-the pyrazine ligand-occurs in association with the change of spin state. The rotation switching was examined on a wide time scale (10 -13-10 -3 s) by both techniques, which clearly demonstrated the combination between molecular rotation and spin-crossover transition under external stimuli (temperature and chemical). The pyrazine rings are seen to perform a 4-fold jump motion about the coordinating nitrogen axis in the high-spin state. In the low-spin state, however, the motion is suppres…

research product

Bidirectional Chemo-Switching of Spin State in a Microporous Framework

The ins and outs of spin: Using the microporous coordination polymer {Fe(pz)[Pt(CN)(4)]} (1, pz=pyrazine), incorporating spin-crossover subunits, two-directional magnetic chemo-switching is achieved at room temperature. In situ magnetic measurements following guest vapor injection show that most guest molecules transform 1 from the low-spin (LS) state to the high-spin (HS) state, whereas CS(2) uniquely causes the reverse HS-to-LS transition.

research product

Guest Modulation of Spin-Crossover Transition Temperature in a Porous Iron(II) Metal Organic Framework: Experimental and Periodic DFT Studies

The synthesis, structure, and magnetic properties of three clathrate derivatives of the spin-crossover porous coordination polymer {Fe(pyrazine)[Pt(CN)(4)]} (1) with five-membered aromatic molecules furan, pyrrole, and thiophene is reported. The three derivatives have a cooperative spin-crossover transition with hysteresis loops 14-29 K wide and average critical temperatures T-c=201 K (1.fur), 167 K (1.pyr), and 114.6 K (1.thio) well below that of the parent compound 1 (T-c=295 K), confirming stabilization of the HS state. The transition is complete and takes place in two steps for 1.fur, while 1.pyr and 1.thio show 50% spin transition. For 1.fur the transformation between the HS and IS (mi…

research product

Inside Cover: Bidirectional Chemo-Switching of Spin State in a Microporous Framework (Angew. Chem. Int. Ed. 26/2009)

Bidirectional chemo-switching of magnetism occurs in a microporous coordination polymer containing spin-crossover subunits, as described by M. Ohba, J. A. Real, S. Kitagawa, and co-workers in their Communication on page 4767 ff. In situ magnetic measurements reveal that most guest molecules transform the framework spin state from diamagnetic low spin (red) to paramagnetic high spin (yellow), whereas the guest CS2 stabilizes the low-spin state. These induced spin states are retained as a memory effect after the release of the guest.

research product