Formation of Molecular Ladder Elements with Macrocyclic Platforms via Linear Bifunctional Ligands

Abstract

Reaction between 4-aminopyridine and a dinuclear zinc(II) component of a Robson macrocyclic ligand has resulted in the formation of a molecular ladder element motif. X-ray single crystal structural analysis indicates that two pyridine rings are assembled at the same direction of the macrocycle, which are placed in a nearly parallel way via pi-pi interactions, forming a concavity structure with a macrocyclic base. It is significantly noted that one hydrogen-bond cycle generated from hydrogen atoms of two amino groups with two perchlorate anions has sustained such an assembly of two 4-aminopyridine species to stand in a face to face pattern through a weak molecular interaction on the macrocyclic platform by one-end coordination bonding. The self-assembly of 4-carboxylic pyridine acid and the same macrocyclic component in the presence of sodium hydroxide has yielded an interesting wheel-like complex. Two macrocyclic dinuclear zinc(II) components have been linked through coordination bonding with two pyridine derivatives situated on the same direction of a macrocycle. X-ray structural results suggest that the compound has a unique sandwich-like structure consisting of two macrocyclic covers with two inversely positioned bridging pyridine carboxylic groups in the middle.

Formation of polymeric chain assemblies of transition metal complexes with a multidentate Schiff-base

“…These complexes are diamagnetic as expected. The Cd(II) and Hg(II) complexes adopt octahedral geometries [31], while a five-coordinate structure is suggested for the Zn(II) centre [32,33].…”

Synthesis and structures of pyridinecarboxylate-containing zinc(II) complexes in dien and tren system

“…In this case the uncoordinated pyridine nitrogen atoms or carboxylate oxygen atoms can act as hydrogen acceptor to construct 2D sheets [6,7] and 3D supramolecular networks [8]. The bidentate coordination modes are reported in zinc complexes through O,O-bis-monodentate (c and c 0 ) and N,O-bis-monodentate (d and d 0 ) as bridges, in which nicotinic and isonicotinic acids link the zinc atoms to yield 1D zigzag chain polymers [9][10][11][12], 2D bilayer [13], sandwich like structure [14], interpenetrating [15,16] and 3D open framework [17]. In the tridentate coordination mode, all of the two oxygen and one nitrogen atoms coordinate to zinc atoms via l-O,O,N-tridentate (e and e 0 ) or N-monodentate and O,O 0 -chelate modes (f and f 0 ) as seen in these polymers, displaying 2D bilayer structures [13], interpenetrating frameworks [15,16,18], 3D sandwich polymeric network [19,20] and open-framework coordination polymer [21].…”

“…Little attention has been devoted to zinc-pyridinecarboxylate complexes in mixed ligand system. Only a few of zinc(II) complexes containing ancillary ligand such as tetrazolate [22], 1,4,7,10-tetraazacyclododecane (cyclen) [23], Schiff base macrocycle [14] and C 2 O 4 2À [24] have been reported. We are interested in the preparation of zinc(II) nicotinate/isonicotinate complexes containing dien and tren as main ligand for the following reasons.…”

Macrocyclic, Dinuclear Zinc(II)‐Directed Self‐Assembly with Pyridine, 2,2′‐Bipyridine and 2‐Methylquinoline: μ2‐OH Bridging Bi‐Macrocyclic Complexes and Hydrogen‐Bond‐Supported Donor‐Acceptor Complexes

“…Such a repulsion could be overcome, however, to permit coordination if extra forces are introduced such as hydrogen bonding or πϪπ interactions to support the system. [5,6] While in compound 3a 2-methylquinoline cannot be coordinated directly to the zinc() atoms because of its further steric repulsion, it instead adopts a parallel way of interacting with its neighboring macrocyclic plane via πϪπ forces while, at the same time, forming a hydrogen bond with one macrocyclic unit. The electron transfer from the conjugated system of the macrocycle to the central zinc() atom upon coordination assists in forming this kind of arrangement.…”

“…When 4-aminopyridine or pyridine-4-carboxylic acid is allowed to react with 1, molecular ladder elements are obtained (Scheme 2, b and c). [6] We report here two kinds of new complexes obtained by the reaction of macrocyclic component 1 with pyridine, 2,2Ј-pyridine and quinoline derivatives. Unlike the reaction with 4,4Ј-bipyrid-ine (1-D molecular ladder polymers bridged by MϪN coordinating bonds), sandwich-like structures (2) are formed where 1 moieties are connected by two µ 2 -OH groups via bridging zinc atoms in the presence of pyridine or 2,2Ј-bipyridine ligands (Scheme 2, c).…”