Semiempirical computational assessment of porphyrins as building blocks for molecule-based magnets: spin–spin coupling in radical-substituted metalloporphyrins
✍ Scribed by David A. Shultz; Kay A. Sandberg
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 137 KB
- Volume
- 12
- Category
- Article
- ISSN
- 0894-3230
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✦ Synopsis
Semiempirical PM3-RHF-CI calculations were used to probe structure-exchange coupling relationships in radical-substituted Zn(II) porphyrins. The results support a number of important design elements for creating high-spin molecules from metalloporphyrins and the corresponding pi-cation radicals. The calculations showed that inactive porphyrin-active phenoxy union mode provides stronger exchange coupling than active porphyrin-inactive phenoxy union mode. Connecting radicals to the metalloporphyrin core via an ethynyl linkage eliminates severe torsion, permitting a coplanar alignment of the two pi systems. Metalloporphyrins could be excellent redox-activated exchange couplers: porphyrin radical cation exchange couples attached radicals more effectively than the neutral porphyrin. Finally, the magnitude of exchange coupling between a metalloporphyrin pi-cation radical depends on the nature of the attached radical. The results of the calculations were explained using a coupler spin analysis.