Acta Phys. -Chim. Sin. ›› 1996, Vol. 12 ›› Issue (04): 372-376.doi: 10.3866/PKU.WHXB19960418

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Thermodynamics and Kinetics of Coordination Reaction of Imidazolates with Cobalt(II) Porphyrin

Zhu Zhi-Ang, Yan Xi, Zhang Zhi-Hui, Ma Gang, Lin Hua-Kuan, Chen Rong-Ti   

  1. Department of Chemistry,Nankai University,Tianjin 300071
  • Received:1995-06-29 Revised:1995-10-18 Published:1996-04-15
  • Contact: Zhu Zhi-Ang

Abstract:

The thermodyntamics of axial coordination reaction of Cobalt(Ⅱ)(p-OCH3)TPP with various ligands [L=Im(imidazole), MeIm (2-methydrimidazole), EMIm (2-ethyl-4-methylimidazole)] at different temperatures in dichloromethane solvent have been studied.
Cobalt(Ⅱ)(p-OCH3)TPP+nL↔ Cobalt(Ⅱ)(p-OCH3)TPP﹒Ln
The equilibrium constant (β) and stoichiometric number (n) of reaction (1) were measured by means of Shimadzu UV-240 spectrophotometer. The changes of standard molar enthalpy △ rHm? and molar entropy △rSm? of reaction (1) were calculated. The steric and electronic effects of the three axial ligands on the reaction were compared.
The kinetic study for the axial coordination faster reaction of Cobalt(Ⅱ) (p-OCH3)TPP with Im in dichloromethane at different temperatures by means of a Union Giken RA-401 stopped-flow spectrophotometer was reported. The mechanism of reaction (1) was postulated as follows:
Co(Ⅱ)(p-OCH3) TPP+ Im↔ Co(Ⅱ)(p-OCH3) TPP﹒Im
Co(Ⅱ)(p-OCH3) TPP﹒Im+Im→Co(Ⅱ)(p-OCH3) TPP﹒(Im)2
    The parameters K and k were evaluated. The △ rHm?, △rSm? of a pre-equilibrium step (2) and △r≠Hm, △r≠Sm of a rate-determining step (3) were also calculated.

By using an LKB2277 Bioactivity Monitor, we have determined the thermogenesis power curves of four kinds of Brucellas S2(55007), M5 (55009),83-202,83-980. And established the thermokinetic equation for the process of cell growth inhibited by the products of metabolism, as:
Ln[1/(β﹒Pt)-1]=ln[1/(β﹒P0)-1]-k0﹒t
From this equation, the rate constants of cell growth k [= k0(1 - β﹒P0)] were obtained. This thermokinetic equation is very suitable for cell growth of separated culture and is very important for the study of bacterial limited growth and their characteristics.

Key words: α,β,γ,δ-tetra(ρ-methoxypheny)porphinatocobalt(II), Imidazolate ligands, UV-Vis spectrophotometer, Stopped-flow spectrophotometer, Equilibrium constant, Mechanism of reaction