X-ray studies of the intra- and intermolecular H-bonding in two phenolic Mannich bases

Abstract

The crystal structures of two phenolic Mannich bases, 1-[(2,3,4,5-tetrachloro-6-hydroxy)phenyl]- N,N-dimethylmethanamine ( 1) and 1-[(3-nitro-6-hydroxy)phenyl]- N,N-diisobutylmethanamine ( 2), were determined by using the single crystal X-ray diffraction method. The results and conditions for molecule 1, C 9H 9NOCl 4 are: M r = 288.99, monoclinic, C2/c, a = 21.88(2)Å, b = 8.419(7)Å, c = 14.63(1)Å, β = 119.62(4)°, V = 2344(3)Å 3, Z = 8, D cacl = 1.638 g cm −3, λ(MoKα) = 0.71069 Å,μ = 9.87 cm −1, F(000) = 1168, T = 296 K, R = 0.043 for 1559 observed reflections. For molecule 2, C 15H 24N 2O 3, results and conditions are: M r = 280.37, orthorhombic, P2 12 12 1, a = 8.850(7)Å, b = 29.399(6)Å, c = 6.22(1)Å, V = 1620(4)Å 3, D calc = 1.150 g cm −3, λ(Mokα) = 0.71069 Å, μ = 0.75 cm −1, F(000) = 608, T = 296 K, R = 0.062 for 755 observed reflections. Compounds 1 was determined to have intermolecular hydrogen bonding involving the zwitterionic form N +H⋯O −1. For compound 2 intramolecular H-bonding was observed with the N⋯HO form retained. Complementary IR measurements in the solid state were in good agreement with the X-ray results. The geometry of the hydrogen bond present depends on the substituents at the amine nitrogen atom.