Blue-Colored, Linear Rigid-Axle [2]Pseudorotaxanes: Metal-Binding Properties, Crystal Structures, and Blue/Red Dichroism

Abstract

Rare blue-colored [2]pseudorotaxanes based on the previously unexplored [N,N'-bis(4-pyridyl)-4,4'-bipyridinium](2+) axle and bis(1,5-naphtho)-32-crown-8 (BN32C8) or bis(1,5-naphtho)-38-crown-10 (BN38C10) wheels have been synthesized and characterized by UV-vis, (1)H NMR spectroscopy, and electrochemistry, and their metal-binding properties toward CdI(2) and HgCl(2) have been studied by optical absorption in solution and X-ray crystallography in the solid state. We report contrasting structures of the same metal and different wheels or the same wheel and different metals. We also show for the first time that a simple metal complex, such as Hg(2)Cl(6)(2-), can induce a blue/red linear dichroism by organizing the [2]pseudorotaxane units into a columnar arrangement in the crystal.

Rotaxanes and pseudorotaxanes with threads containing viologen units

“…It was possible to selectively reduce V 1 (without the reduction of V 2 ), since V 1 and V 2 have sufficiently different reduction potentials. The reduction of V 1 in 10 and 11 may be performed by applying an appropriate negative potential or by using Zn metal, under these conditions the stations V 2 do not undergo reduction; as a result 10•3PF 6 and 11•3PF 6 in singly reduced radical cation states are formed.…”

“…The shuttling occurs after the first reduction (i.e. for 11•3PF 6 ), in this time the ring encircles V 2 , which is a weaker recognition site than V 1 , and also after the second reduction (i.e. for 11•2PF 6 ) and after the third reduction (i.e.…”

“…In the packing structure of B, however, four pseudorotaxanes B are linked by a PF 6 ‾ anion, each pair of pseudorotaxanes B being connected by hydrogen bonds of hydroxyethyl groups between two molecules of viologen 36, each included in the cavity of 37. It was observed that lariat ether 37 can include the K + ions.…”

“…Rotaxanes 1-5 and pseudorotaxanes [6][7][8][9] are examples of mechanically interlocked species, 10,11 besides them, to interlocked architectures belong also catenanes, [12][13][14][15] as well as more complex structures such as trefoil knots, 16 Solomon knots, 17 Borromean rings, 18 daisy chains 19 or ravels.…”

Novel fully screen printed flexible electrochemical sensor for the investigation of electron transfer between thiol functionalized viologen and gold clusters

“…), electrochemical or light input [24,25]. The focus has been on building functional metal-organic architectures based on pseudorotaxanes, and we have recently reported intriguing new properties associated with pseudorotaxanes built from 4,4 -bipyridinium (viologen) based axle and aromatic crown ether wheel components, such as colorimetric temperature sensing and dichroism [26,27].…”