Ni(ii) dipyrrin complexes bearing peripheral pyridyl or imidazolyl groups self-assemble into 2- and 3-D coordination polymers

Abstract

While the numerous reported Ni(II) dipyrrin complexes are discrete species, derivatives bearing peripheral pyridyl or imidazolyl groups self-assemble into coordination networks. As reported with Cd(II) salts, reaction of the dipyrrin ligand functionalized with a 4-pyridyl moiety with Ni(OAc)2 affords a 2D coordination polymer in which the Ni(II) cation, in an octahedral environment, is bound to two dipyrrinato chelates and two pyridyl groups, in cis arrangement, belonging to neighbouring complexes. In the crystal, the layers are homochiral with a consecutive ΔΛΔΛ stacking. Interestingly, analogous reaction with the derivative bearing a peripheral phenyl-4-pyridyl unit forms a similar 2D organization, yet expanded owing to the presence of the phenyl spacer. In this case, the formation of homochiral sheets is also observed, however with a single enantiomer of the complex in the crystal. Furthermore, whereas a distorted 2D coordination polymer is obtained with the novel dipyrrin ligand appended with a phenyl-3-pyridyl group, a 3D coordination polymer is formed with the slightly more flexible derivative bearing an imidazolyl moiety.