A doubly mononuclear cobalt(II) complex constructed with azide anions and a new coordination mode of the 2-(2-pyridylmethylamino) ethanesulfonic acid ligands: structure, conformation comparison and Hirshfeld surface analysis

Abstract A doubly mononuclear cobalt(II) complex [Co(Hpmt) 2 (N 3 ) 2 ] 2 ( 1 ) (Hpmt = 2-(2-pyridylmethylamino)ethanesulfonic acid; N 3 = azide anion) has been synthesized and structurally characterized. Single-crystal X-ray diffraction analysis showed that 1 has crystallized in orthorhombic crystal system, Cmc 2 1 space group. In the two independent and identical complexes, the cobalt(II) centers are both hexa-coordinated in distorted CoN 6 octahedrons. The reduced Schiff base ligand Hpmt displayed a new coordination mode of bidentate chelate ( κ 2 - N , N ′). The careful comparisons between Hpmt upon coordination and as free acid form demonstrated that the conformation flexibility might be responsible for its multiple coordination modes. The N–H⋯O and C–H⋯N hydrogen bonds constructed the 3D network, and this mainly agreed with the Hirshfeld surface analysis results.