Novel stable high spin molecules possessing three different arranged fashions are designed with -·N-N＜ as a spin-containing (SC) fragment, various aromatic, such as benzene (1), pyridine (2), pyridazine (3), pyrimidine (4),pyrazine (5), triazine (6) as end groups (EG) and phenyl as a ferromagnetic coupling (FC) unit. The effects of a different end groups on the spin multiplicities of the ground states and their stabilities were investigated by means of AM1-CI approach. It has been found that the spin densities on the two atoms of the SC fragment are different from delocalization resulting in the specific stability of -·N-N＜. In these molecules, the stabilities of the triplet states decrease when the distance between the atoms of central SC (-N-) increases. The orders of the stability of triplet states for 1an, 1bn, 1cn [They are isomers in which SC is connected with FC in different way (1an, NiNNN1; 1bn,N1N NiN; 1cn, NN1N1N) and six heterocycles are EG] show that the tability of triplet states with heterocycles as end groups is higher than that with phenyl as end groups, and in the order: triazine (EG)＞pyrimidine, pyrazine＞pyridine, pyridazine.
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