Hydrogen-Bonded Acid-Base Molecular Complexes of Nitronylnitroxides

Abstract

Intermolecular hydrogen-bonded complexes of P-nitronylnitroxide benzoic acid (p-NNBA-H) with m- andp-pyridylnitronylnitroxides (m- and p-PYNN, respectively) were prepared. The m-PYNN·p-NNBA-H complex crystallizes into the monoclinic P21 /c space group [a=6.685(3) Å, b=17.657(2) Å, c=22.169(l) Å, β=92.90(1)°, V=2613(1) Å3, Z=4], while the crystal of p-PYNN·p-NNBA-H belongs to the monoclinic P21 In space group[a=12.199(3) Å, b=23.265(4) Å, c=9.522(2) Å, β=101.84(2)° V=2644.9(9) Å3, 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-NNBA-H. The intermolecular N…O distances are 2.642(5) Å in m-PYNN·p-NNBA-H and 2.613(6) Å 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 singlet-triplet model with 2J AF /k B =-16.0 K and the Curie-Weiss law with θ =-0.68 K, respectively.