Ferromagnetic intermolecular interaction of the cation radical ofm-N-methylpyridinium nitronyl nitroxide. A CASSCF study

✍ Scribed by M. Okumura; K. Yamaguchi; K. Awaga

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 488 KB
• Volume: 228
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(94)00992-9

✦ Synopsis

Semi-empirical APUHF and ab initio UNO CASSCF/4-31G calculations have been carded out for the dimer of m-N-methylpyridinium nitronyl nitroxide cation (m-MPYNN + ) extracted from its experimental crystal structure in order to elucidate the origin of the large ferromagnetic effective exchange integral I J~b I. It is found that the sign of the calculated Jab is positive, and its magnitudes are 6.51 and 3.96 era-~ by these methods, which correspond to about 80 and 50% of the experimental value, respectively. The dynamic spin polarization plays an important role in determining the sign of Jab, whereas the short intermolecular contact induced by the Coulombic attraction is responsible for the large Jab. Implications of the calculated results are discussed in relation to the possibilities of high-To organic ferromagnets and organic helimagnets.