Intramolecular ferromagnetic coupling in bis-oxoverdazyl and bis-thioxoverdazyl diradicals with polyacene spacers

• Published in: Theoretical chemistry accounts Vol. 127; no. 1-2; pp. 57 - 67
• Main Authors: Bhattacharya, Debojit, Shil, Suranjan, Misra, Anirban, Klein, D. J.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.09.2010
• Subjects: Atomic/Molecular Structure and Spectra; Chemistry; Chemistry and Materials Science; Inorganic Chemistry; Organic Chemistry; Physical Chemistry; Regular Article; Theoretical and Computational Chemistry; Nuclear independent chemical shift; Polyacene couplers; High spin; Ferromagnet; Verdazyl
• ISSN: 1432-881X; 1432-2234
• DOI: 10.1007/s00214-009-0705-y

We predict the intramolecular exchange coupling constant ( J ) for 10 different oxo- and thioxo-verdazyl-based hi-spin ground-state diradicals with linear polyacene couplers of varying length using the broken symmetry approach in an unrestricted DFT framework. The magnetic characteristics of these systems are explained using the spin-density distribution, and an analysis is made by “magnetic” orbitals. The nuclear independent chemical shift (NICS) values have been calculated for the diradicals. The average NICS(1) (1 Å above the ring surface) value per benzenoid ring increases as the size of the coupler increases. So-called ΔNICS(1) values [the difference among average NICS(1) per benzenoid ring in the coupler and the NICS(1) of the linear polyacene molecule] are correlated with J values. Bond orders and hyperfine coupling constants have also been evaluated and analyzed for the diradicals.