Macrocyclic Multicenter Complexes of Nickel and Copper of Increasing Complexity

Abstract

Multicenter (bi-, tri-, and tetranuclear) tetraazamacrocyclic complexes were self-assembled from Ni and Cu tetraazamacrocyclic mononuclear units and α,ω-diamines as building blocks. The structures of all compounds studied were proved by spectroscopic methods (ESI MS and NMR spectroscopy). Electrochemical experiments revealed reversible one-electron electrode processes at each of the Ni(2+) and Cu(2+) centers with formation of metal cations in oxidation state +3. Long linkers allow bi- and trinuclear complexes with noninteracting metal centers to be obtained. In the case of the short linkers (e.g. ethylenediamine) higher, trinuclear species are formed as major product. The structures of the bis- and tris-macrocyclic systems were confirmed by single-crystal X-ray diffraction. The tris-macrocyclic systems form cations in the shape of triangles partially filled with counterions and solvent molecules. The cations form positively charged layers, which interact in the crystal lattice with the neighboring negatively charged layers of anions. In solution, the trinuclear complexes exhibit strong host-guest interactions with 9,10-dimethyltriptycene due to complementarity of shape and size of this guest molecule. The association constants were determined by NMR spectroscopy and voltammetry, and very good agreement was obtained. The structural flexibility of the tetranuclear complex with long linkers allows for attractive interactions between the metal-complexing macrocycles that result in folding of the molecule. On the contrary, no folding is possible in the case of short linkers consisting of two CH(2) groups.

Tetraaza[14]macrocyclic Transition Metal Complexes as DNA Intercalators

“…It has been reported earlier [15,20,36] that the coordination of various metal ions together with the presence of methyl substituent at the exocyclic nitrogen atom [20] can visibly change the π-accepting properties of a cyclidene system. Furthermore, introducing the hydroxyl group at the terminal position of each aliphatic chain should modify both the complex solubility in water and the affinity to π-donors, including DNA.…”

“…The synthesis was carried out in an analogous way to the methods used for the synthesis of other cyclidene systems that were obtained previously by the group of KorybutDaszkiewicz. [14][15][16][17]31] The complexes were separated using reversed-phase silica gel and crystallised from water/acetonitrile mixture with an excess of ammonium hexafluorophosphate upon slow evaporation of solvents. The corresponding chlorides were precipitated from acetonitrile solutions of hexafluorophosphate salts by adding a large excess of anhydrous tetrabutylammonium chloride.…”

“…They are waterstable π-electron rich tetraazamacrocyclic systems (also called Jäger complexes), that during the last decade they have been used by the group of Korybut-Daszkiewicz as building blocks for the synthesis of a range of macrocycles, including linear compounds, oligomacrocycles, [14,15] catenanes, [16,17] pseudorotaxanes [18] and rotaxanes. [19] It has been demonstrated Six tetraazamacrocyclic copper(II) and nickel(II) complexes have been synthesised and their interactions with doublestranded DNA (calf-thymus DNA) have been studied using circular and linear dichroism, as well as other spectroscopic methods.…”

“…The dissociation to metal cation and free tetraaza [14]macrocyclic ligand was never observed in nickel(II) and copper(II) cyclidenes, as confirmed many times using NMR and mass spectrometry. [14][15][16][17][18][19][20][21][22] The removal of the metal ion can only occur in the presence of strong acids in dry solvents. Moreover, a large number of heterodinuclear bismacrocyclic complexes, containing both copper and nickel ion in one molecule have been previously obtained and neither the presence of free ligand in solution nor metal scrambling was observed.…”

Synthesis of Carbonyl‐substituted Tetracyanodihydrotetraaza[14]annulenes

“…These particular metals were chosen in view of previously studied coordination abilities of cyclidenes, which nickel(II), copper(II) and palladium(II) complexes are most common and show very rich electrochemical properties. [12,[26][27][28] This may be an important feature for future applications of DH-TAA systems within areas where cyclidenes have already been used. The coordination can be carried out in acetonitrile where both the substrate and product are only slightly soluble.…”