Coordination networks generated from transition metal chlorides and a flexible double betaine

The new flexible double betaine 1,4-bis(2-picolyloxyl)benzene-N,N'-diacetate (L) has been synthesized and used to generate five complexes with divalent metal chlorides: [M(H2O)(6)]Cl-2-L-2H(2)O (M = Mn (1), Co (2)), [Cu(mu-L)Cl-2](infinity) (3), {[Zn(mu-L)Cl-2]-2H(2)O)(infinity) (4), and {[Cd-2(mu-Cl)(2)(mu-L)Cl-2(H2O)2].2H(2)O](infinity) (5). Isomorphous compounds 1 and 2 have a hydrogen-bonded three-dimensional network in which adjacent L ligands overlap through pi-pi stacking of the pyridine and benzene rings. Compounds 3, 4, and 5 display three different types of one-dimensional polymeric structures. Bridged by L acting in the anti mode, compound 3 exhibits an infinite zigzag chain in which consecutive, approximately planar L ligands are arranged in a crossed manner when viewed along the chain direction, the distance between adjacent copper(II) ions being about 13 Angstrom. In contrast, compound 4 features a spring-like infinite helical chain with zinc ions lying on the axis and bridged by L acting in the syn fashion, and the Zn(II)...Zn(II) separation is approximately 9 Angstrom. In compound 5, the building unit is a centrosymmetric Cd2Cl2 moiety, and adjacent dimeric units are linked by the centrosymmetric L ligand acting in the anti mode to give an infinite zigzag chain running along the c axis; such chains are further connected through hydrogen bonds to form a three-dimensional network. (C) 2002 Elsevier Science Ltd. All rights reserved.