HYDROGEN-BONDED ACID-BASE MOLECULAR-COMPLEXES OF NITRONYLNITROXIDES

Intermolecular hydrogen-bonded complexes of p-nitronylnitroxide benzoi c acid (p-NNBA-H) with m- and p-pyridylnitronylnitroxides (m-and p-PYN N, respectively) were prepared. The m-PYNN . p-NNBA-H complex crystall izes into the monoclinic P2(1)/c space group [a = 6.685(3) Angstrom, b = 17.657(2) Angstrom, c = 22.169(1) Angstrom, beta = 92.90(1)degrees, V = 261.3(1) Angstrom(3), Z = 4], while the crystal of p-PYNN. p-NNBA H belongs to the monoclinic P2(1)/n space group [a=12.199(3) Angstrom , b = 23.265(4) Angstrom, c = 9.522(2) Angstrom, beta = 101.84(2)degre es, V = 2644.9(9) Angstrom(3), Z = 4]. In their crystals, there is an intermolecular hydrogen bond between the nitrogen atom on the pyridyl ring of PYNN and one of the oxygen atoms of the carboxyl group of p-NN BA-H. The intermolecular N ... O distances are 2.642(5) Angstrom in m- PYNN . p-NNBA-H and 2.613(6) Angstrom in p-PYNN . p-NNBA-H, indicating rather intense hydrogen bonds. The magnetic properties of m-PYNN . p- NNBA-H and p-PYNN . p-NNBA-H are well interpreted in terms of the sing let-triplet model with 2J(AF)/k(B) = -16.0 K and the Curie-Weiss law w ith theta = -0.68 K, respectively.