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Spin Transitions in Iron(II) Complexes
1996
Iron(II) has the 3d6 outer electronic configuration and hence its octahedral complexes may be either high-spin or low-spin. The high-spin configuration, t 2g 4 e g 2 , is adopted when relatively weak-field ligands are coordinated while the low-spin, t 2g 6 e g 0 , is obtained when strong-field ligands are involved. In Oh symmetry the ground states are 5T2g and lA1g, for the high-spin and low-spin configurations, respectively. While in most iron(II) six-coordinate complexes the symmetry is lower than Oh, these designations are generally adopted in the following sections for convenience. [Fe(H2O)6]2+ and [Fe(en)3]2+ (en = ethylenediamine) are typical examples of high-spin complexes, while [Fe…
Mixed-Valence, Mixed-Spin-State, and Heterometallic [2×2] Grid-type Arrays Based on Heteroditopic Hydrazone Ligands: Synthesis and Electrochemical Fe…
2005
Une famille de complexes heterometalliques [M 1 2 M 2 2 (L - ) 4 ] n + du type grille [2×2] 1-9 a ete preparee. Les trois approches synthetiques multietapes des ligands hydrazone heteroditopiques A-C possedent chacune des caracteristiques regio-, redox-, enantio-selectives. Ces ligands possedent un groupement NH ionisable et un groupement hydrazone non-ionisable NMe, qui permettent un controle des proprietes redox du metal complexe en fonction de la charge de la cavite coordinante. Les substituants 2-pyrimidine (R) et 6-pyridine (R') influencent de maniere significative la geometrie des complexes formes ainsi que leurs proprietes electrochimiques et magnetiques. Les etudes par spectroscopie…
New polynuclear 4,4ˈ-bis-1,2,4-triazole Fe(II) spin crossover compounds
2001
L'interet porte aux materiaux moleculaires du Fe(II) presentant une transition entre un etat haut-spin (HS, S = 2) et un etat bas-spin (LS, S = 0), sous l'effet d'une variation de temperature, de pression ou d'une irradiation lumineuse, n'a cesse de croitre au cours de ces dix dernieres annees [1-4]. La famille des composes du Fe(II) a base de derives du 1,2,4-triazole substitues par un groupe R sur l'azote 4 a ete tres etudiee pour ses proprietes de transition de spin (TS), qui pourraient permettre des applications en electronique moleculaire [5-15, 29, 32, 36, 37]. Nous avons recemment presente le premier compose a TS possedant une structure tridimensionnelle (figure 2). Ce compose de for…
Spin-Crossover and Liquid Crystal Properties in 2D Cyanide-Bridged FeII−MI/II Metalorganic Frameworks
2010
Novel two-dimensional heterometallic Fe(II)-M(Ni(II), Pd(II), Pt(II), Ag(I), and Au(I)) cyanide-bridged metalorganic frameworks exhibiting spin-crossover and liquid crystal properties, formulated as {FeL(2)[M(I/II)(CN)(x)](y)}·sH(2)O, where L are the ligands 4-(4-alkoxyphenyl)pyridine, 4-(3,4-dialkoxyphenyl)pyridine, and 4-(3,4,5-trisalkoxyphenyl)pyridine, have been synthesized and characterized. The physical characterization has been carried out by means of EXAFS, X-ray powder diffraction, magnetic susceptibility, differential scanning measurements, and Mössbauer spectroscopy. The 2D Fe(II) metallomesogens undergo incomplete and continuous thermally induced spin transition at T(1/2) ≈ 170 …
Thermal-,Pressure-, and Light-Induced Spin Transition in Novel Cyanide-Bridged FeII-AgI Bimetallic Compounds with Three-Dimensional Interpenetrating …
2002
[EN] Low-spin, high-spin and spin-transition behaviours have been observed for the doubly interpenetrating three-dimensional bimetallic compounds {Fe-II(pz)[Ag(CN)(2)](2)}.pz (pz= pyrazine), {Fe-II(4,4'-bipy)(2)[Ag(CN)(2)](2)} (4,4'-bipy-4,4'-bipyridine), and {Fe-II-(bpe)(2)[Ag(CN)(2)](2)} (bpe = bispyridylethylene), respectively. The single crystals of the bpe derivative undergo a spin transition with a large hysteresis loop at about 95 K. After several warming and cooling cycles, the single crystals become a microcrystalline powder with 50% spin transition. Influence of pressure- as well as light-induced excited spin-state trapping (LIESST) on the thermal 50% spin transition of the microc…
Photoinduced HS state in the first spin-crossover chain containing a cyanocarbanion as bridging ligand
2009
A new polymeric approach, based on cyanocarbanion ligands, for the design of spin crossover (SCO) compounds led us to the compound [Fe(abpt)2(tcpd)] (1) (tcpd^2 = (C[C(CN)2|3)^2 , abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) which has been characterised as the first SCO molecular chain involving a cyanocarbanion as bridging ligand. Gomez Garcia, Carlos Jose, Carlos.Gomez@uv.es
Iron(II) metallomesogens based on symmetrical tripod ligands
2012
Abstract Novel mononuclear tripodand-based iron(II) complexes showing liquid crystal properties have been synthesized and characterized. These are based on ligands tris[3-aza-4-((5-Cn)(6-R-2-pyridyl))but-3-enyl]amine, where R = hydrogen or methyl, 1,3,5-cis,cis-tris[1-aza-2-((5-alkyloxy)(2-pyridyl))vinyl]cyclohexane and 2,2,2-tris(2-aza-3-((5-alkyloxy)(2-pyridyl))prop-2-enyl)ethane. The physical characterization has been carried out by means of single-crystal X-ray diffraction measurements, magnetic susceptibility, differential scanning calorimetry, X-ray powder diffraction and Mossbauer spectroscopy.
Traumatic bone cyst: a retrospective study of 21 cases
2009
Objective: To describe the clinical and radiological characteristics, and surgical findings of traumatic bone cysts. Study Design: A retrospective observational study was made of 21 traumatic bone cysts. The diagnosis was based on the anamnesis, clinical examination, and complementary tests. Panoramic and periapical X-rays were obtained in all cases, together with computed tomography as decided by the surgeon. A descriptive statistical analysis was made of the study variables using the SPSS v12.0 for Windows. Results: There was a clear female predominance (14:7). The mean age was 26.5 years (range 8-45 years). The cysts in all cases constituted casual findings during routine radiological ex…
Homoleptic iron(II) complexes with the ionogenic ligand 6,6′-Bis(1H-tetrazol-5-yl)-2,2′-bipyridine: spin crossover behavior in a singular 2D spin cro…
2015
Deprotonation of the ionogenic tetradentate ligand 6,6′-bis(1H-tetrazol-5-yl)-2,2′-bipyridine [H2bipy(ttr)2] in the presence of FeII in solution has afforded an anionic mononuclear complex and a neutral two-dimensional coordination polymer formulated as, respectively, NEt3H{Fe[bipy(ttr)2][Hbipy(ttr)2]}·3MeOH (1) and {Fe[bipy(ttr)2]}n (2). The anions [Hbipy(ttr)2]− and [bipy(ttr)2]2– embrace the FeII centers defining discrete molecular units 1 with the FeII ion lying in a distorted bisdisphenoid dodecahedron, a rare example of octacoordination in the coordination environment of this cation. The magnetic behavior of 1 shows that the FeII is high-spin, and its Mössbauer spectrum is characteriz…
A knowledge-based decision support system in bioinformatics: An application to protein complex extraction
2013
Abstract Background We introduce a Knowledge-based Decision Support System (KDSS) in order to face the Protein Complex Extraction issue. Using a Knowledge Base (KB) coding the expertise about the proposed scenario, our KDSS is able to suggest both strategies and tools, according to the features of input dataset. Our system provides a navigable workflow for the current experiment and furthermore it offers support in the configuration and running of every processing component of that workflow. This last feature makes our system a crossover between classical DSS and Workflow Management Systems. Results We briefly present the KDSS' architecture and basic concepts used in the design of the knowl…