Dinuclear Complexes as Building Blocks for Tetra-Nuclear Macrocyclic Complexes with Dithiolate Macrocyclic Ligand

Abstract

A series of novel tri-, tetra-and pentanuclear complexes composed of dinuclear LM 2 units (M=Co, Ni, Zn; L=24-membered macrocyclic hexaaza-dithiophenolate ligand) and ferrocene-carboxylate ([CpFeC 5 H 4 CO 2 ]ˉ), 1,1'-ferro-cenedicarboxylate ([Fe(C 5 Keywords: coordination chemistry, amino-thiophenolate ligands, di-and tetranuclear complexes, ferrocene and naphthalene diimide derivatives, polynuclear complexes IntroductionThe chemistry of container molecules has developed extensively over the past two decades. Many container molecules such as calixarenes, resorcarenes, cyclodextrins, carcerands and glycourils have been invaluable in studying the fundamental principles of inclusion phenomena and consequently their use in separation science or drug delivery, as two examples of application. Importantly, the area has attracted interest in the field of supramolecular chemistry because the properties of such host-guest compounds are often different from those of their constituent components. By adjusting the size and form of the binding cavity it is often possible to complex co-ligands in unusual coordination modes, to activate and transform small molecules, or to stabilize reactive intermediates [1,2]. One subclass are the metallated container molecules, in which metal ions and clusters are used as both a point of recognition and to give the container a well-defined structure. Such compounds also allow for an interplay of molecular recognition and transition-metal catalysis, and for the construction of more effective enzyme mimics. Of interest to the present work is the ability of metallocavitands to recognize and encapsulate difunctionalised molecules towards stabilising or enhancing the optical and electronic properties of redox-and photo-active compounds within a confined environment set up by two hemispheres.The carboxylate group, RCO 2-, can bind to transition metals in a variety of coordination modes giving rise to complexes of great structural diversity [3]. Current activities focus on the coordination chemistry of polycarboxylate ligands, as these offer great potential in the construction of polynuclear aggregates [4] and extended coordination polymers with micro-and mesoporous structures [5][6][7][8] or catalytic properties [9]. In addition, polycarboxylate ligands are of importance as spin-coupling bridging ligands [10][11][12][13][14][15][16][17] in the rapidly expanding fi eld of molecular magnetism [18, 19]. In this context, an enormous amount of literature has been generated concerning the distance dependence of magnetic exchange interactions between metal atoms linked by extended dicarboxylate ligands. Dinuclear copper complexes bridged by oxalate [20, 21] and terephthalate [22][23][24] dianions form, by far, the largest group of such systems, and it appears that the exchange interactions depend on the M···M distance [25], the relative orientation of the magnetic orbitals [26], and the degree of conjugation of the organic spacer unit [27, 28].