Nickel(II) and zinc(II) complexes of N-substituted di(2-picolyl)amine derivatives: Synthetic and structural studies Linda Götzke a , Kerstin Gloe a , Katrina A. Jolliffe b , Leonard F. Lindoy b , Axel Heine a , Thomas Doert a , Anne Jäger a , Karsten Gloe a,⇑ a Department of Chemistry and Food Chemistry, TU Dresden, 01062 Dresden, Germany b School of Chemistry, University of Sydney, NSW 2006, Australia article info Article history: Received 16 November 2010 Accepted 2 December 2010 Available online 16 December 2010 Keywords: Nickel(II) Zinc(II) Polypyridyl X-ray structure Di(2-picolyl)amine abstract The interaction of di(2-picolyl)amine (1) and its secondary N-substituted derivatives, N-(4-pyridylmethyl)- di(2-picolyl)amine (2), N-(4-carboxymethyl-benzyl)-di(2-picolyl)amine (3), N-(4-carboxybenzyl)-di(2- picolyl)amine (4), N-(1-naphthylmethyl)-di(2-picolyl)amine (5), N-(9-anthracenylmethyl)-di(2-picol- yl)amine (6), 1,4-bis[di(2-picolyl)aminomethyl]benzene (7), 1,3-bis[di(2-picolyl)aminomethyl]benzene (8) and 2,4,6-tris[di(2-picolyl)amino]triazine (9) with Ni(II) and/or Zn(II) nitrate has resulted in the isola- tion of [Ni(1)(NO 3 ) 2 ], [Ni(2)(NO 3 ) 2 ], [Ni(3)(NO 3 ) 2 ], [Ni(4)(NO 3 ) 2 ]ÁCH 3 CN, [Ni(5)(NO 3 ) 2 ], [Ni(6)(NO 3 ) 2 ], [Ni 2 (7)(NO 3 ) 4 ], [Ni 2 (8)(NO 3 ) 4 ], [Ni 3 (9)(NO 3 ) 6 ]Á3H 2 O, [Zn(3)(NO 3 ) 2 ]Á0.5CH 3 OH, [Zn(5)(NO 3 ) 2 ], [Zn(6) (NO 3 ) 2 ], [Zn(8)(NO 3 ) 2 ] and [Zn 2 (9)(NO 3 ) 4 ]Á0.5H 2 O. X-ray structures of [Ni(4)(NO 3 ) 2 ]ÁCH 3 CN, [Ni(6)(NO 3 ) 2 ] and [Zn(5)(NO 3 ) 2 ] have been obtained. Both nickel complexes exhibit related distorted octahedral coordi- nation geometries in which 4 and 6 are tridentate and bound meridionally via their respective N 3 -donor sets, with the remaining coordination positions in each complex occupied by a monodentate and a bidentate nitrato ligand. For [Ni(4)(NO 3 ) 2 ]ÁCH 3 CN, intramolecular hydrogen bond interactions are present between the carboxylic OH group on one complex and the oxygen of a monodentate nitrate on an adjacent complex such that the complexes are linked in chains which are in turn crosslinked by intermolecular offset p–p stacking between pyridyl rings in adjacent chains. In the case of [Ni(6)(NO 3 ) 2 ], two weak CHÁÁÁO hydrogen bonds are present between the axial methylene hydrogen atoms on one complex and the oxygen of a mono- dentate nitrate ligand on a second unit such that four hydrogen bonds link pairs of complexes; in addition, an extensive series of p–p stacking interactions link individual complex units throughout the crystal lattice. The X-ray structure of [Zn(5)(NO 3 ) 2 ] shows that the metal centre once again has a distorted six-coordinated geometry, with the N 3 -donor set of N-(1-naphthylmethyl)-di(2-picolyl)amine (5) coordinating in a merid- ional fashion and the remaining coordination positions occupied by a monodentate and a bidentate nitrato ligand. The crystal lattice is stabilized by weak intermolecular interactions between oxygens on the bound nitrato ligands and aromatic CH hydrogens on adjacent complexes; intermolecular p–p stacking between aromatic rings is also present. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction The interaction of transition and post-transition metal ions with di- and polypyridyl ligands continues to receive much attention, in part reflecting the coordination versatility of such ligands and their importance in a number of biological, catalytic, photoactive and sen- sor applications [1,2]. For example, the ‘classical’ di(2-picolyl)amine ligand (dipic, 1), as well as its secondary nitrogen substituted deriv- atives, yield strong complexes with a wide range of metal ions. In particular, reports of the interaction of the parent dipic moiety and its (uncharged) N-substituted derivatives with Ni(II) [3–7] and Zn(II) [8–18] have appeared, although the N-substituted derivatives have received less attention than those of dipic itself. Even so, individual N-substituted ligand complexes of both metals have been employed in a number of applied investigations – including for carbon dioxide fixation [19] as well as for a range of studies focused on biological and/or sensor applications [10,20–31,17,32–40]. In a recent paper we presented the results of an investigation of the interaction of Cu(II) with both di(2-picolyl)amine (dipic, 1) and a range of its N-substituted derivatives (including 2, 3 and 6–9 shown in Scheme 1) [41]. In parallel studies, we have also investi- gated aspects of the metal ion chemistry of a number of related N-substituted derivatives of 2,2-dipyridylamine with Cu(II) [42], Pd(II) [42] and Ag(I) [43,44]. We now report the results of an exten- sion of these studies that involve the interaction of the N-substituted 0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2010.12.005 ⇑ Corresponding author. Tel.: +49 351 463 34357; fax: +49 351 463 31478. E-mail address: karsten.gloe@chemie.tu-dresden.de (K. Gloe). Polyhedron 30 (2011) 708–714 Contents lists available at ScienceDirect Polyhedron journal homepage: www.elsevier.com/locate/poly