Does the Solid—Liquid Crystal Phase Transition Provoke the Spin-State Change in Spin-Crossover Metallomesogens?
Three types of interplay/synergy between spin-crossover (SCO) and liquid crystalline (LC) phase transitions can be predicted: (i) systems with coupled phase transitions, where the structural changes associated to the Cr↔LC phase transition drives the spin-state transition, (ii) systems where both tr...
| Publicado en: | Journal of the American Chemical Society Vol. 130; no. 4; pp. 1431 - 1440 |
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| Autores principales: | , , , , , |
| Formato: | Artículo |
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American Chemical Society
1/30/2008
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| Materias: | |
| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=29436600&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 29436600 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 1/30/2008 vid: 130 iid: 4 pid: 997 pub: American Chemical Society artinfo: ui: 29436600 10.1021/ja077265z ppf: 1431 ppct: 9 formats: tig: atl: Does the Solid—Liquid Crystal Phase Transition Provoke the Spin-State Change in Spin-Crossover Metallomesogens? aug: au: Seredyuk, M. Gaspar, A. B. Ksenofontov, V. Gaiyametdinov, Y. Kusz, J. GÜtlich, P. affil: Johannes-Gutenberg-Universität Universitat de Valëncia Russian Academy of Science University of Silesia su: Phase transitions Liquid crystals Metallomesogens Metal ions Phase partition Phase equilibrium sug: subj: Phase transitions Liquid crystals Metallomesogens Metal ions Phase partition Phase equilibrium ab: Three types of interplay/synergy between spin-crossover (SCO) and liquid crystalline (LC) phase transitions can be predicted: (i) systems with coupled phase transitions, where the structural changes associated to the Cr↔LC phase transition drives the spin-state transition, (ii) systems where both transitions coexist in the same temperature region but are not coupled, and (iii) systems with uncoupled phase transitions. Here we present a new family of Fe(ll) metallomesogens based on the ligand tris[3-aza-4-((5-C)(6-R)(2-pyridyl))but-3-enyl]amine, with C = hexyloxy, dodecyloxy, hexadecyloxy, octadecyloxy, eicosyloxy, R = hydrogen or methyl (C-trenH or C-trenMe), which affords examples of systems of types i, ii, and iii. Self-assembly of the ligands C-trenH and C-trenMe with Fe(A)·xHO salts have afforded a family of complexes with general formula [Fe(C-trenR)](A)·HO (S ⩾ O), with A = CIO, F, Cl, Br and I. Single-crystal X-ray diffraction measurements have been performed on two derivatives of this family, named as [Fe(C-trenH)](CIO) (C-1) and [Fe(C-trenMe)](CIO) (C-2), at 150 K for C-1 and at 90 and 298 K for C-2. At 150 K, C-1 displays the triclinic space group P1, whereas at 90 and at 298 K C-2 adopts the monoclinic P2/c space group. In both compounds the iron atoms adopt a pseudo-octahedral symmetry and are surrounded by six nitrogen atoms belonging to imino groups and pyridines of the ligands C-trenH and C-trenMe. The average Fe(ll)—N bonds (1.963(2) Å) at 150 K denote that C-1 is in the low-spin (LS) state. For C-2 the average Fe(ll)-N bonds (2.007(1) Å) at 90K are characteristic of the LS state, while at 298 K they are typical for the high-spin (HS) state (2.234(3) Å). Compound C-1 and [Fe-(C-trenH)](CIO) (C-1) adopts the LS state in the temperature region between 10 and 400K, while compound C-2 and [Fe(C-trenMe)](ClO) (n = 12 (C-2), 18 (C-2)) exhibit spin crossover behavior at T centered around 140 K. The thermal spin transition is accompanied by a pronounced change of color from dark red (LS) to orange (HS). The light-induced excited spin state trapping (LIESST) effect has been investigated in compounds C-2, C-2 and C-2. The T is 56 K (C-2), 48 K (C-2), and 56 K (C-2). On the basis of differential scanning calorimetry, optical polarizing microscopy, and X-ray diffraction findings for C-1, C-2, and C-2 at high temperature a smectic mesophase S has been identified with layered structures similar to C-1 and C-2.… pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2008 holdings: @attributes: islocal: N |
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