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Kristian H. Sugiyarto
Department of Chemistry Education, Faculty of Mathematics and Science, State University of Yogyakarta, Yogyakarta 55281
Mathematics

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Transisi Spin dalam Spesies Turunan Tris[2-(Pirazol-3-il)piridina]besi(II) Djulia Onggo; Kristian H. Sugiyarto
Jurnal Matematika & Sains Vol 4, No 2 (1999)
Publisher : Institut Teknologi Bandung

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Abstract

Complexes [Fe(3-pp)3][X]2.2H2O, where 3-pp = (2-(pyrazol-3-yl)pyridine, and X = I, Br, NO3, and CF3SO3, and X2 = [Fe(CN)5(NO)], have been isolated and characterized in terms of magnetic, Mössbauer, and electronic spectral properties. All the dihydrate salts which were isolated from aqueous solution are red brown, and heating up to 110 - 1600C results in decomposition for all salts except for the triflate which gives complete dehydration to the anhydrous yellow salt. At room temperature, the magnetic moment of the dihidrate salts are slightly higher than the purely low-spin value (2,0-2,5 BM). The magnetic moments change gradually parallel to the change in temperature within 90 - 363K, and this is associated with the continuous spin state - singlet (1A1)quintet (5T2) - transition in iron(II). For the yellow anhydrous triflate salt, the spin state transition occurs dramatically, being discontinuous and associated with hysteresis (Tc↓ = 229K, Tc↑= 241K ; ∆Tc = 12K ). The triflate salt also shows a termochromic nature, being yellow at room temperature and dark red-brown at low temperature.
Structural Study of Bis(2,6-bis(pyrazol-3-yl)pyridine)nickel(II) by Calorimetry and EXAFS Spectrometry Kristian H. Sugiyarto
Jurnal Matematika & Sains Vol 9, No 1 (2004)
Publisher : Institut Teknologi Bandung

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Abstract

The stepwise complex formation of 2,6-bis(pyrazol-3-yl)pyridine, bpp, with nickel(II) perchlorate in DMF has beendetermined by calorimetric method and then followed by EXAFS spectrometry. It was found that the complexformation follows two stepwise pathways namely the formation of mono pyrazolyl-pyridine, [Ni(DMF)3 bpp]2+, andbis pyrazolyl-pyridine, [Ni(bpp)2]2+; the formation constants being log β1 = 6.57, and log β2 = 5.02, respectively,with the total value of log β = 11.58. The final formation of six-coordinated compound was confirmed by EXAFSanalysis with coordination number of 5.87(2) and the average of Ni–Nbpp bond length of 2.065(1) Å.
Co-Authors Djulia Onggo