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  • Heinemann, Frank W.  (4)
  • Chemistry/Pharmacy  (4)
  • VA 4072.5  (4)
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  • Chemistry/Pharmacy  (4)
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  • VA 4072.5  (4)
  • 1
    Online Resource
    Online Resource
    Wiley ; 2010
    In:  European Journal of Inorganic Chemistry Vol. 2010, No. 26 ( 2010-09), p. 4100-4109
    In: European Journal of Inorganic Chemistry, Wiley, Vol. 2010, No. 26 ( 2010-09), p. 4100-4109
    Abstract: The reaction of 2 H ‐benzotriazole ( 1 ) with dichloroacetic acid leads to the symmetric bis(2 H ‐benzotriazol‐2‐yl)methane ( 2c ) in 40 % yield. Deprotonation of 2c at the bridging methylene group and subsequent carboxylation with CO 2 yielded the new tripodal N , N , O ligand bis(2 H ‐benzotriazol‐2‐yl)acetic acid Hbbta ( 3 ). The sterically less demanding sodium 3,3‐bis(1 H ‐1,2,4‐triazol‐1‐yl)propionate Na[btp] ( 5 ) was obtained by saponification of methyl 3,3‐bis(1 H ‐1,2,4‐triazol‐1‐yl)propionate ( 4 ). The heteroscorpionate ligand 3 was treated with [MnBr(CO) 5 ] and [RuCl 2 (PPh 3 ) 3 ] to form the manganese tricarbonyl complex [Mn(bbta)(CO) 3 ] ( 6 ) and the air stable ruthenium complex [Ru(bbta)Cl(PPh 3 ) 2 ] ( 7 ). DFT calculations and the IR spectra of the carbonyl complex 6 reveal ligand 3 to be a less electron‐donating ligand compared to the bis(1 H ‐pyrazol‐1‐yl)acetic acid Hbpza. In case of the 1 H ‐1,2,4‐triazole‐based ligand 5 formation of coordination polymers were observed as proven by the synthesis of [Zn(btp) 2 ] ∞ ( 8 ) and [Mn(btp) 2 ] ∞ ( 9 ). Polymer 8 crystallises in linear chains of zinc atoms bridged by two molecules of ligand 5 each. These polymer chains show an interesting π‐stacking interaction between uncoordinated triazole residues of the ligands. Deposition of the coordination polymer on highly ordered pyrolytic graphite (HOPG) was successful and was analysed by scanning tunnelling microscopy (STM). Reaction of Na[btp] ( 5 ) with MnSO 4 · H 2 O resulted in a metal organic framework (MOF) [Mn(btp) 2 ] ∞ ( 9 ).
    Type of Medium: Online Resource
    ISSN: 1434-1948 , 1099-0682
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2010
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  • 2
    In: European Journal of Inorganic Chemistry, Wiley, Vol. 2009, No. 14 ( 2009-05), p. 2136-2143
    Abstract: The ligand 2,6‐bis(1 H ‐pyrazol‐1‐yl)‐4‐(thiocyanatomethyl)pyridine (L) has been prepared from the hydroxymethyl precursor by OH/Br exchange and subsequent thiocyanate substitution. Two polymorphs of the unsolvated iron(II) complex [Fe(L) 2 ](BF 4 ) 2 crystallize at room temperature from the same solution (MeOH), and side by side. One (yellow) is high spin between 4 and 350 K, whereas the other (red‐brown) shows spin crossover, with a thermal spin‐transition centred at 272 K (width ca. 50 K). Both forms have been fully characterized by variable‐temperature structure determination and magnetic susceptibility measurements. At a given temperature, the solid‐state structures differ strongly with respect to the coordination geometry at iron(II), the orientation of the thiocyanatomethyl substituents, and cation‐anion contacts. The implications of these structural differences for the observed spin behaviour are discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
    Type of Medium: Online Resource
    ISSN: 1434-1948 , 1099-0682
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2009
    detail.hit.zdb_id: 1475009-0
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  • 3
    In: European Journal of Inorganic Chemistry, Wiley, Vol. 2010, No. 2 ( 2010-01), p. 187-187
    Abstract: The cover picture shows the crystal structure of an iron(II) complex with a tridentate triazine‐based ligand, one of three complexes whose thermal and photonic spin‐dynamics are discussed in the article by G. Hörner, A. Grohmann et al. on p. 221 ff. While there is a competition between spin crossover and ligand exchange upon thermal excitation in solution, the complexes switch cleanly between their stable low‐spin and metastable high‐spin forms upon photoexcitation. Artwork: Holger Neumann, Gentura.
    Type of Medium: Online Resource
    ISSN: 1434-1948 , 1099-0682
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2010
    detail.hit.zdb_id: 1475009-0
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  • 4
    In: European Journal of Inorganic Chemistry, Wiley, Vol. 2010, No. 2 ( 2010-01), p. 221-232
    Abstract: The temperature‐dependent and photodynamic spin behaviour of three iron(II) complexes with different 2,6‐dipyridyl‐4‐phenyltriazine ligands L1 – L3 was investigated in the solid state and in solution (DMSO). The ligands differ in the substituent R in the 4‐position of the phenyl ring ( L1 : R = H; L2 : R = OCH 3 ; L3 : R = SAc), which allows the electronic properties of the ligands to be finetuned. The magnetic data for the complex [Fe( L3 ) 2 ](BF 4 ) 2 in the solid state indicate an incomplete spin transition to the high‐spin form upon warming from liquid helium temperature, reaching about 30 % at 400 K. There is circumstantial evidence for paramagnetic contributions compatible with spin transitions, namely, temperature‐dependent NMR spectroscopic line shifts and line broadening in solution (DMSO). However, an efficient thermally induced spin crossover in solution is hindered by the substitution lability of the complexes, as has been detected and analyzed in an extended temperature‐dependent UV/Vis spectroscopic study. Essentially unaffected by thermally induced substitution lability, the transient dynamics of the iron(II) complexes after nanosecond laser flash excitation of their metal‐to‐ligand charge‐transfer bands provide good evidence for efficient photoinduced spin transitions in solution in all cases. The range of measured lifetimes of the high‐spin quintet states is in accord with previously published data. Importantly, in our series of iron(II) complexes, the lifetimes of the high‐spin state reflect the electron‐donating character of the ligands.
    Type of Medium: Online Resource
    ISSN: 1434-1948 , 1099-0682
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2010
    detail.hit.zdb_id: 1475009-0
    Location Call Number Limitation Availability
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