2011 Volume 131 Issue 8 Pages 1233-1240
The chelate forming reaction between 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(4-methylpyridyl)porphine (OBTMPyP) and various metal ions, which belong mainly to 4th period and 7th-12th groups in the periodic table, was examined by the observing the absorption spectra. Because one chemical spicy, H-OBTMPyP, which is one protonated compound at an N atom of pyroll ring among 4 pyroll rings, was observed at pH 9.0, this pH was used to measure the changes of absorption spectra with metal ions. From these changes of absorption spectra of OBTMPyP with metal ions, OBTMPyP were seen to react easily with Cu2+, Zn2+, Mn2+, or Co2+ ion without other additional reagent or heating within 1 min at over 25°C. On the other hand, OBTMPyP reacted little with Ni2+, and was not all with Fe3+ (or Fe2+ reduced by ascorbic acid from Fe3+) under the same conditions. 5,10,15,20-tetrakis(4-methylpyridyl)porphine (TMPyP) also did not reacted metal ions above these conditions. The λmax of each Soret band differed. The stability constants (Ka value) of Cu-, Zn-, Mn- and Co-OBTMPyP was calculated by the change in absorbance of each band, and was 2.6×105, 3.6×105, 2.7×105 and 2.9×105 (dm3/mol), respectively. It was revealed that OBTMPyP and metal ions reacted at molar ratio of 1:1, and octabromination of porphine rings improved the reactivity with these ions.
