Robert F. Pasternack, Bruce S. Gillies, Julia P. Stromsted
{"title":"Substitution reactions of a water-soluble metalloporphyrin with azide and 1,1,3,3-tetramethyl-2-thiourea","authors":"Robert F. Pasternack, Bruce S. Gillies, Julia P. Stromsted","doi":"10.1016/S0006-3061(00)80003-4","DOIUrl":null,"url":null,"abstract":"<div><p>The substitution reactions of tetrakis-(4-N-methylpyridyl)porphinecobalt (III) (Co<sup>III</sup>TMpyP) with azide and with 1,1,3,3-tetramethyl-2-thiourea (TMTU) have been studied as a function of pH at 25° and an ionic strength of 0.5 M. The mechanistic pathway proposed for thiocyanate [1] and pyridine [2] is applicable to these ligands as well once allowance is made for two attacking forms of azide, N<sub>3</sub><sup>—</sup> and HN<sub>3</sub>. A TMTU axial substituent has about the same influence on the rate of further ligand substitution as does SCN<sup>—</sup> and a much larger influence than does azide. Similar behavior between bound SCN<sup>—</sup> and bound TMTU is also shown in electron-transfer reactions with Ru(NH<sub>3</sub>)<sub>6</sub><sup>2+</sup> - Whereas both sulfur-containing ligands enhance the rate relative to the diaquo complex, the azide complex undergoes reduction an order of magnitude more slowly than does the diaquo complex.</p></div>","PeriodicalId":9177,"journal":{"name":"Bioinorganic chemistry","volume":"8 1","pages":"Pages 33-44"},"PeriodicalIF":0.0000,"publicationDate":"1978-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0006-3061(00)80003-4","citationCount":"8","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Bioinorganic chemistry","FirstCategoryId":"1085","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0006306100800034","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 8
Abstract
The substitution reactions of tetrakis-(4-N-methylpyridyl)porphinecobalt (III) (CoIIITMpyP) with azide and with 1,1,3,3-tetramethyl-2-thiourea (TMTU) have been studied as a function of pH at 25° and an ionic strength of 0.5 M. The mechanistic pathway proposed for thiocyanate [1] and pyridine [2] is applicable to these ligands as well once allowance is made for two attacking forms of azide, N3— and HN3. A TMTU axial substituent has about the same influence on the rate of further ligand substitution as does SCN— and a much larger influence than does azide. Similar behavior between bound SCN— and bound TMTU is also shown in electron-transfer reactions with Ru(NH3)62+ - Whereas both sulfur-containing ligands enhance the rate relative to the diaquo complex, the azide complex undergoes reduction an order of magnitude more slowly than does the diaquo complex.