One- and two-dimensional polymerisation of homoleptic M(II)-complexes of 4′-(3-pyridyl)-2,2′;6′,2-terpyridine in the solid state: A combined study by XRD, cyclic voltammetry, NMR and UV-Vis spectroscopies

Homoleptic Fe(II), Co(II), Ni(II), Cu(II) and Ru(II) complexes based on the tridentate ligand 4 '-(3-pyridyl)2,2': 6',2 ''-tpy (tpy = terpyridine) have been synthesized in good yields and characterized with different techniques. Although the Fe(II) and Ru(II)-complexes exhibit diamagnetic behaviour in their solution H-1 NMR spectra, the Co(II), Ni(II) and Cu(II) centres displaced the H-1 resonances between 0 and 100 ppm. The electrochemical and spectroscopic properties of the complexes indicated that the pyridyl group exhibits electron-withdrawing character. Furthermore, a deep insight into the solid state packing of Co(II)-and Cu(II)-complexes, as their hexafluorophosphate (PF6) salts, reveals a two-dimensional terpyridine embrace, formed by face-to-face intermolecular pi-pi interactions that give rise to extended sheets in two dimensions. Modification of the PF6 anions by bulky tetraphenylborate [BPh4] anions totally eliminates the intermolecular interactions between cations in one dimension and an extended one-dimensional polymer is formed in the other dimension. (C) 2014 Elsevier B. V. All rights reserved.