Cadmium(II) iodide and thiocyanate complexes adopted by polycyclic 1,4-bis(pyridazin-4-yl)benzene: interplay of coordination and π–π stacking interactions

Abstract

New complexes containing the 1,4-bis(pyridazin-4-yl)benzene ligand, namely diaquatetrakis[1,4-bis(pyridazin-4-yl)benzene-κN(2)]cadmium(II) hexaiodidodicadmate(II), [Cd(C14H10N4)4(H2O)2][Cd2I6], (I), and poly[[μ-1,4-bis(pyridazin-4-yl)benzene-κ(2)N(2):N(2')]bis(μ-thiocyanato-κ(2)N:S)cadmium(II)], [Cd(NCS)2(C14H10N4)]n, (II), demonstrate the adaptability of the coordination geometries towards the demands of slipped π-π stacking interactions between the extended organic ligands. In (I), the discrete cationic [Cd-N = 2.408 (3) and 2.413 (3) Å] and anionic [Cd-I = 2.709 (2)-3.1201 (14) Å] entities are situated across centres of inversion. The cations associate via complementary O-H...N(2') hydrogen bonding [O...N = 2.748 (4) and 2.765 (4) Å] and extensive triple π-π stacking interactions between pairs of pyridazine and phenylene rings [centroid-centroid distances (CCD) = 3.782 (4)-4.286 (3) Å] to yield two-dimensional square nets. The [Cd2I6](2-) anions reside in channels generated by packing of successive nets. In (II), the Cd(II) cation lies on a centre of inversion and the ligand is situated across a centre of inversion. A two-dimensional coordination array is formed by crosslinking of linear [Cd(μ-NCS)2]n chains [Cd-N = 2.3004 (14) Å and Cd-S = 2.7804 (5) Å] with N(2):N(2')-bidentate organic bridges [Cd-N = 2.3893 (12) Å], which generate π-π stacks by double-slipped interactions between phenylene and pyridazine rings [CCD = 3.721 (2) Å].