From Homoleptic to Heteroleptic Double Stranded Copper(I) Helicates:  The Role of Self-Recognition in Self-Assembly Processes

Abstract

The ligands 2,9-bis[(6-methyl-2, 2'-bipyridin-6'-yl)methyleneoxymethylenyl]-1,10-phenanthroline (6), 6' ',6' "-bis[(6-methyl-2, 2'-bipyridin-6'-yl)methyleneoxymethylenyl)]-2' ',2' "-bipyridine (2), 5,5'-bis[(6-methyl-2,2'-bipyridin-6'yl)methyleneoxymethylenyl]-2, 2'-bithiophene (7), and 6,6'-bis[(6-methyl-2, 2'-bipyridin-6'-yl)methyleneoxymethylenyl]-2,2'-biphenyl (8) and their respective homo- and heteroleptic double-stranded copper(I) complexes were prepared and characterized in order to estimate the importance of self-recognition in the self-assembly processes of double-stranded copper complexes. The homoleptic double-stranded copper complexes of 2, 6, 7, and 8 were characterized by NMR, FAB-MS, and electrochemistry. It was found that 6 and 2 each form a single double-stranded helicate having the structure of [(L)(2)Cu(3)](3+) (L = 2 or 6), 7 forms two double-stranded [(7)(2)Cu(3)](3+) complexes, and 8 results in a mixture of at least two [(8)(2)Cu(2)](2+) complexes. The potential shift, DeltaE degrees (,) of the Cu(+)/Cu(2+) redox process of these complexes reflects the binding affinity of the different binding sites to the copper cation. The electrochemical data show that the central units have a higher affinity to Cu(+) as compared to the off-center binding sites. NMR was used to determine the actual complex composition obtained from different mixtures of 2, 6, or 7 with Cu(+). Interestingly, we have found that, although 6, 2, and 7 each form homoleptic double-stranded complexes, no heteroleptic double-stranded copper complexes were formed from the mixtures of 7 with either 6 or 2. However, when mixtures of 6 and 2 are used, helicate distributions seem to follow simple statistics. These results are discussed in terms of the relative importance of self-recognition in the self-assembly of double-stranded helicates.

An Attempt to Programme the Orientation of Bis(heterocyclic) Azine Heterotopic Sequences around AgI, CuI and ZnII Metal Centres

“…In such a situation, a rapid decomplexation-recomplexation of only one helicate extremity would be sufficient. The first proposal is supported by Harding [17] and later by Greenwald [18] who made similar observations. Despite this, 63 Cu NMR spectra of the [Cu 2 (9) (16) and the homotopic Cu I complex were investigated in order to confirm one of the two proposals (see ref.…”

A novel heterostranded double-helical coordination polymer with chiral channels emitting blue fluorescence

“…As a result, two different kinds of helical chains form the heterostranded double-helical structures. Even if lots of double-, triple-and higher-order stranded helical structures have been reported so far, to the best of our knowledge, the example of heterostranded double-helical structure is really rare [21,2,22]. For each infinite single-helical chain, the screw pitch contains two units of Zn 2+ -ligands, and the adjacent heterostranded double-helical chains share Zn 2+ ions to develop into the homochiral helical two-dimensional sheets (Fig.…”

“…Lately, Wang and co-workers have reported the 17-fold interwoven helices [20]. However, most of the above-mentioned helical coordination polymers are interwinded with the same strands which are comprised of the same ligands and metal ions (so-called homostranded helix), and the report about the heterostranded helix coordination polymer is very rare [21,2,22] even though the judicious choices of suitable flexible ligands and metal ions. This situation could be asserted to two typical reasons (1) it is difficult that different ligands construct the heterostranded helix with the same screwpitch in the process of molecular self-assembly; (2) it cannot be predicted that the products is from the self-assembly of flexible ligands with metal ions.…”

Crystals versus Electrochromic Films: Pathway-Dependent Coordination Networks

“…[4][5][6] In the following years, highly complex helicates were introduced and are composed of oligobipyridine strands coordinated to copper cations. [7][8][9][10] The coordination chemistry of carboxylic acids and late transition metals has been extensively used for the formation of metal-organic frameworks (MOFs). [11][12][13][14][15] This strong metal-ligand interaction resulted in highly robust and porous materials.…”