Search results for " STATES"

Spin-State-Dependent Redox-Catalytic Activity of a Switchable Iron(II) Complex

2017

The spin state of catalytically active 3d metal centers plays a significant role for their activity in enzymatic processes and organometallic catalysis. Here we report on the catalytic activity of a Fe(II) coordination compound that can undergo a cooperative switch between low-spin (LS) and high-spin (HS) states. Catalytic measurements within 291 - 318 K temperature region reveal a drastic drop of the catalytic activity upon conversion of metallic centers from the LS to the HS form. For a thermoswitchable [Fe(NH2trz)3]Br2 complex (Tup = 305 K), an activation energy is found to be considerably lower for the LS state (158 kJ mol-1) comparing to the HS state (305 kJ mol-1). Mossbauer analysis …

Anisotropic Effect after Stretching of the Spin-Crossover Compound [Fe(II)(2,6-bis-(benzimidazol-2′-yl)pyridine)2] (C1O4)2 in Polyvinylalcohol Polyme…

1999

Abstract [Fe(II)(2,6-bis-(benzimidazol-2′-yl)-pyridine)2](C1O4)2 diffused into a poly(vinyl)alcohol polymer matrix, exhibits an thermally induced spin-crossover. After stretching the matrix, the compound orients itself in the matrix. Polarised UV/VIS spectra measured parallel and perpendicular to the stretching direction allowed to calculate the distortion of the molecule in the matrix by means of semi-empirical PPP SCF-CI calculations.

Strong Field Iron(II) Complex Converted by Light into a Long-Lived High-Spin State

2000

Spin Switching with Triazolate-Strapped Ferrous Porphyrins

2019

Fe(III) porphyrins bridged with 1,2,3-triazole ligands were synthesized. Upon deprotonation, the triazolate ion coordinates to the Fe(III) ion, forming an overall neutral high-spin Fe(III) porphyrin in which the triazolate serves both as an axial ligand and as the counterion. The second axial coordination site is activated for coordination and binds p-methoxypyridine, forming a six-coordinate low-spin complex. Upon addition of a phenylazopyridine as a photodissociable ligand, the spin state of the complex can be reversibly switched with ultraviolet and visible light. The system provides the basis for the development of switchable catalase- and peroxidase-type catalysts and molecular spin sw…

Spin-Transition in [Fe(II)(2,6-Bis-(Benzimidazol-2′-yl)pyridine)2] (CIO4)2: Hysteresis Effect Dependent on the Matrix

1999

Abstract Far-Infrared spectroscopical investigation of the spin-crossover in [Fe(II)(2,6-bis-(benzimidazol-2′-yl)-pyridine)2] (CIO4)2 exhibits a hysteresis in both CsI and polyethylene matrices within temperature cycles between 100K and 520K. The hysteresis broadening is dependent on the matrix and bigger in CsI. This can be explained due to polarity and hydrogen bonding. Two low spin vibrations, LS1 at 437 cm−1 and LS2 at 424cm−1, are observed. On heating from 100K to 520K: during LS1 decreases, the LS2 raises temporarily, until both LS1 and LS2 disappear; for the HS only one raising species was observed. This gives raise to assume two different sub-lattices.

Bidirectional Chemo-Switching of Spin State in a Microporous Framework

2009

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.

Coherent states: a contemporary panorama

2012

Iron (II) isothiocyanate complexes with substituted pyrazines: Experimental and theoretical views on their electronic structure

2015

Abstract Synthesis, structural, magnetic, Mossbauer and thermal studies of isothiocyanate iron (II) complexes with substituted pyrazines (iodo-, bromo- and amino-derivatives) are discussed here. Complexes with iodo- and bromo-derivatives were found to have the composition [Fe(Ipz)2(SCN)2(H2O)2]·2Ipz (1) and [Fe(Brpz)2(SCN)2(H2O)2]·2Brpz (2), whereas in the case of amino-functionalized pyrazine the formation of [Fe(NH2pz)4(SCN)2] (3) was observed. 3D organization of the molecular complexes is stabilized within different hydrogen, halogen and lone pair–π interactions. Spin state of iron (II) ions in 1–3 was determined as high spin by Mossbauer and magnetic measurements. DFT calculations for t…

Markku Ruotsila, Vaalit ja konservatismin aaltoliike yhdysvaltalaisessa politiikassa

2019

Markku Ruotsila, Sydänmaiden kapina. Donald Trump, amerikkalainen konservatismi ja äärioikeiston nousu. Helsinki: Gaudeamus, 2018, 391 s.

Uzņēmējdarbības un vadības dažādi aspekti / Different Aspects of Entrepreneurship and Management: Report of Abstracts

2022

LU Biznesa, vadības un ekonomikas fakultāte