Search results for "STATES"
showing 10 items of 1532 documents
Binding Sites, Vibrations and Spin-Lattice Relaxation Times in Europium(II)-Based Metallofullerene Spin Qubits.
2021
Abstract To design molecular spin qubits with enhanced quantum coherence, a control of the coupling between the local vibrations and the spin states is crucial, which could be realized in principle by engineering molecular structures via coordination chemistry. To this end, understanding the underlying structural factors that govern the spin relaxation is a central topic. Here, we report the investigation of the spin dynamics in a series of chemically designed europium(II)‐based endohedral metallofullerenes (EMFs). By introducing a unique structural difference, i. e. metal‐cage binding site, while keeping other molecular parameters constant between different complexes, these manifest the ke…
A new eight-coordinate complex of manganese(II): synthesis, crystal structure, spectroscopy and magnetic properties of [Mn(Hoxam)2(H2O)4] (H2oxam=oxa…
2001
Abstract The crystal structure of an eight-coordinate manganese(II) compound containing oxamato and water molecules as ligands [Mn(Hoxam)2(H2O)4], were H2oxam=oxamic acid, has been determined by X-ray diffraction on single-crystals. The coordinated oxygen atoms are located at the vertices (corners) of a distorted bicapped trigonal antiprism. Hydrogen bonding is responsible for an extended 3D-network. The magnetic susceptibility data of the compound have been investigated. χMT follows the Curie law, at very low temperatures χMT decreases smoothly due to weak intermolecular interactions and/or due to a small zero field splitting of the sextuplet spin state of the Mn(II).
Substituent effects on the spin equilibrium in iron(II) pyrazolylborate complexes
1995
Abstract Two new complexes of the iron(II) pyrazolylborate system, [Fe(HB(pz)(dmpz) 2 ) 2 ] and [Fe(HB(pz) 2 (dmpz)) 2 ] (pz = pyrazole, dmpz = 3,5-dimethylpyrazole), have been prepared and found to exhibit thermal spin crossover in toluene solutions by means of optical spectroscopy and magnetic susceptibility measurements. Comparison with the published magnetic behaviour of the complexes [Fe(HB(dmpz) 3 ) 2 ] and [Fe(HB(pz) 3 ) 2 ] shows that the high spin state is stabilized with an increasing number of methyl substituents.
Electronic Structure Modulation in an Exceptionally Stable Non-Heme Nitrosyl Iron(II) Spin-Crossover Complex
2016
The highly stable nitrosyl iron(II) mononuclear complex [Fe(bztpen)(NO)](PF6)(2) (bztpen=N-benzyl-N,N',N'-tris(2-pyridylmethyl)ethylenediamine) displays an S=1/2 S=3/2 spin crossover (SCO) behavior (T-1/2=370 K, Delta H= 12.48 kJmol(-1), Delta S=33 JK(-1) mol(-1)) stemming from strong magnetic coupling between the NO radical (S=1/2) and thermally interconverted (S=0 S=2) ferrous spin states. The crystal structure of this robust complex has been investigated in the temperature range 120-420 K affording a detailed picture of how the electronic distribution of the t(2g)-e(g) orbitals modulates the structure of the {FeNO}(7) bond, providing valuable magneto-structural and spectroscopic correlat…
Kinetic and Thermodynamic Studies of Iron(III) and Iron(IV) σ-Bonded Porphyrins. Formation and Reactivity of [(OEP)Fe(R)]n+, Where OEP Is the Dianion…
1998
A series of high- and low-spin iron(III) phenyl and fluorophenyl octaethylporphyrin complexes are characterized by their electrochemical and spectroscopic properties in nonaqueous media. The investigated compounds are represented as (OEP)Fe(R), where R = C6H5, 3,4,5-C6F3H2, 2,4,6-C6F3H2, C6F4H, or C6F5 and OEP is the dianion of 2,3,7,8,12,13,17,18-octaethylporphyrin. The two C6F3H2 complexes are of special interest in that these isomers differ in the spin state of the iron(III). Electrochemical studies indicate that three one-electron oxidations are seen for all of the (OEP)Fe(R) derivatives which were investigated both at room and low temperature under conditions where migration of the σ-b…
Synthesis, crystal structures and magnetic properties of mononuclear tris(croconate)ferrate(III) complexes
2006
Abstract A straightforward synthetic method to prepare mononuclear croconato-containing iron (III) complexes, (A)3[Fe(C5O5)3] [A = tetrabutylammonium = n-Bu4N+ (1) and tetraphenylphosphonium = PPh 4 + ( 2 ) ; C 5 O 5 2 - = croconate = dianion of 4 , 5 - dihydroxycyclopent - 4 - ene - 1 , 2 , 3 - trione ] along with their crystal structures and magnetic properties, are reported. The Fe(III) atom adopts a pseudo-octahedral geometry while magnetic susceptibility measurements, in the 2–300 K temperature range, show the occurrence of a high spin state (S = 5/2) in both complexes.
Synthesis, structure and magnetic characterization of [Fe(bpp)2][Cu(pds)2]2·solv (solv=CH3CN and CH3OH)
2008
A novel salt of the Fe(II) cation [Fe(bpp)2]2+ (bpp = 2,6-bis(pyrazol-3-yl)pyridine) with the [CuIII(pds)2]- anion (pds = pirazine-2,3-diselenolate) formulated as [Fe(bpp)2][Cu(pds)2]2·3CH3CN has been prepared and characterized by single crystal X-ray diffraction and magnetic measurements. The salt presents a layered structure where cations and anions alternate along the b direction with many intermolecular short contacts between the cations and anions. The magnetic properties show that the Fe(II) cations [Fe(bpp)2]2+ present a high-spin S = 2 ground spin state with g = 2.073(1) and a zero field splitting (ZFS) of 7.7(1) cm-1 but no the expected spin transition at low temperatures. © 2008 E…
Effect of metal dilution on the light-induced spin transition in [FexZn1-x(phen)2(NCS)2] (phen = 1,10-phenanthroline)
2008
International audience; The thermal and light-induced spin transitions in [FexZn1-x(phen)2(NCS)2] (phen = 1,10-phenantholine) have been investigated by magnetic susceptibility, photomagnetism and diffuse reflectivity measurements. These complexes display a thermal spin transition and undergo the light-induced excited spin state trapping (LIESST) effect at low temperatures. For each compound, the thermal spin transition temperature, T1/2, and the relaxation temperature of the photo-induced high-spin state, T(LIESST), have been systematically determined. It appears that T1/2 decreases with the metal dilution while T(LIESST) remains unchanged. This behaviour is discussed on the basis of the ki…
Modulation of Nuclearity in Cu II −Mn II Complexes of a N 2 O 2 Donor Ligand Depending upon Carboxylate Anions: Structures, Magnetic Properties and C…
2020
Three new hetero-metallic copper(II)-manganese(II) complexes, [(CuL)2 Mn3 (C6 H5 CO2 )6 ] (1), [(CuL)2 Mn(CH3 CO2 )2 ] (2), and {[(CuL)2 Mn(C6 H5 CH2 CO2 )2 ] ⋅ 2CH3 CN} (3), have been synthesized using [CuL] as ''metalloligand'' (where H2 L=N,N'-bis(2-hydroxynaphthyl-methylidene)-1,3-propanediamine). Single-crystal structural analyses show an almost linear penta-nuclear structure for complex 1 where a square planar [CuL] unit is connected to each of the two terminal MnII ions of a linear, centrosymmetric [Mn3 (benzoate)6 ] unit through the double phenoxido bridges. Both complexes 2 and 3 possess a linear tri-nuclear structure where two terminal square-pyramidal [CuL] units are bonded to th…
A Switchable Molecular Rotator: Neutron Spectroscopy Study on a Polymeric Spin-Crossover Compound
2012
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…