Picosecond measurements on the binding and release of basic ligands by excited states of Ni(II) porphyrins
✍ Scribed by Dongho Kim; Dewey Holten
- Publisher
- Elsevier Science
- Year
- 1983
- Tongue
- English
- Weight
- 743 KB
- Volume
- 98
- Category
- Article
- ISSN
- 0009-2614
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✦ Synopsis
Ewitntion with 35 ps flas!~cs of tmcomplcxd Ni(II) porphyrins in ZI complc\in~ (basic) solvent results in the bindins of lignds m the excited state. Exitation of complcxed molecules leads to the relexc of ligsnds in the exited state. These processus appcti to occur mainly from the lowest (d.d) ewitcd state of the species being pumped.
t . Introduction Metalloporphyrins and relllted molecules are active p.micipdnts in a number of biological systems [ I] _ The ability of these molecutts to function in rcdos reactions and to reversibly bind Iimnds is undoubtedly influenced strongly by the electronic distribution in the porphyrin macrocycle. and the changes that can occur in this distribution during the course of a reaction. As model systems for hemes we are particularly interested in compleses with predicted [3] low-lying exited states containitir: significant "n~.2tal" character, i.e. (d-d>. (z.d), fd.2). through which the normally eniisshe porphyrin (n.x*) exited singlets and triplets can dcrlctivatc rlidiatiorllessly very rapidly. Recent picosecond investigations ofNi(II)-porphyrin photophpsics have been undertaken to help clarify the exited-state deactiwtion routes in these non-lumninescent (ds) conlpleses [Z--6]. The question has been c_xanGned as to whether the radiationless decay in noncomple.\ing solvents proceeds mainly through the low-* Abbreviations for Ni(ll) porphyrin macrocycles are as folloos: TPP = tetraphcnylporphyrin, TPyP = tetraqz-pyridylporphyrin, TcPP = tctraczubo~ylphenylporphyrti,