Role of pi-conjugation in influencing the magnetic interactions in dinitrenes: a broken-symmetry approach.

In the present study, we investigated the magnetic interactions of some dinitrenes by employing the broken symmetry-unrestricted density functional theoretical (BS-UDFT) approach along with the use of three basis sets. The magnetic coupling parameter (J) has been calculated, and thereby the magnetic character of the molecule and the strength of magnetic interaction are explored for these molecules. The exchange coupling parameters for the corresponding unconjugated systems are also calculated to see the role of pi-conjugation. Our results suggest that a strong antiferromagnetic interaction exists in conjugated dinitrenes, and the strength of magnetic interaction decreases with increase in spacer length. For the unconjugated dinitrenes, the nature of magnetic interaction reduced appreciably and becomes weakly antiferromagnetic. The singlet-triplet energy gap for each system is also calculated. For the conjugated systems, it is observed that the singlet states are more stable than the triplet states, whereas for the unconjugated systems, the relative stability of the singlet state reduces to a considerable extent. This discrepancy of results for the conjugated and unconjugated dinitrenes can be attributed to the effect of pi-conjugation, and the results can be well explained by this effect.