Organic biradical compounds having a biphenyl or naphthalene core and long alkyl groups with TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) radicals at their ends were found to show moderately strong antiferromagnetic interactions, being based on the singlet-triplet model. The behavior Could be understood by considering the structures as being assembled in a "hand-in-hand" fashion.