Synthesis of [5]Rotaxanes Containing Bi‐ and Tridentate Coordination Sites in the Axis

Abstract

A new example of a linear [5]rotaxane has been synthesized by using the traditional "gathering-and-threading" approach but based on an unusual axle incorporating a symmetrical bis(bidentate) chelating fragment built on a 4,7-phenanthroline core. The stoppering reaction is particularly noteworthy since, instead of using a trivial bulky stopper as precursor to the blocking group, two semistoppered copper-complexed [2]pseudorotaxanes (namely [2]semirotaxanes) are used, which leads to the desired [5]rotaxane in good yield. The efficiency of the method relies on the use of "click" chemistry, with its very mild conditions, and on the protection by a transition-metal (copper(I)) of the various coordinating groups present in the fragments to be interconnected (terpy and bidentate chelating groups), thus inhibiting potential detrimental side reactions during the copper-catalyzed stoppering reaction. Since the external fragments and the central core of the system contain tri- and bidentate chelating units, respectively, the axle of the final [5]rotaxane incorporates two types of coordinating units: two external terpy groups (terpy: 2,2':6',2''-terpyridine) and two central bidentate ligands. Such a situation enables the system to tidy two different metals centers, and to localize them in a priori well-defined positions. This is what was observed when mixing the free ligand with a mixture of Zn(2+) and Li(+) : the zinc(II) ions were unambiguously shown to occupy the external sites, whereas the Li(+) cations were found in the central part of the [5]rotaxane. An X-ray diffraction study carried out on a [3]pseudorotaxane, the axis of which is similar to the central part of the [5]rotaxane axle, demonstrates that Zn(2+) is clearly five-coordinate, the fifth ligand being a counterion, even when the coordination site of the pseudorotaxane is designed for four-coordinate metals, which is in marked contrast with copper(I) or Li(+) .

Transition metal-templated synthesis of catenanes and rotaxanes

“…Other coordination geometries were demonstrated to work equally well ( Figure 2), providing that the adequate metal/ligand combination is chosen, for example linear (two-coordinate) Au(I)/pyridyl (py) [11] and octahedral (six-coordinate) Ru(II)/2,2′;6′, 2″-terpyridyl (terpy) [12]. The use of less straightforward four-coordinate square planar (sp) Pd(II), and five-coordinate square-based pyramidal (sqp) and trigonal bipyramidal (tbp) Zn(II) and Cu(II) involved heteroleptic ligand pairs, such as 2,6-pyridyldicarboxamide/py in the former case [13][14][15] and dpp/terpy in the latter [16,17]. As an illustration, a [5]rotaxane incorporating at the same time Cu(I) and Zn(II) templates is shown in Figure 3.…”

Strategien und Taktiken für die metallgesteuerte Synthese von Rotaxanen, Knoten, Catenanen und Verschlingungen höherer Ordnung

“…[343] Unter Verwendung des klassischen dpp-Makrocyclus 19 (Schema 5) und einer Achse mit sowohl zwei-als auch dreizähnigen Domänen gelang die Herstellung eines linearen [5]Rotaxans durch eine modulare Strategie. [156] Ebenfalls berichtet wurde über die verwandten [2]-, [3]-und [4]Rotaxane, die die gleiche Achse, aber unterschiedliche Zahlen aufgefädelter Makrocyclen enthalten, und die das Potenzial haben, als Multiring-Shuttles zu agieren. [344] Beer und Mitarbeiter verwendeten ein Pyridyl-N-oxid-Motiv zur Koordination von Alkalimetallen (M = Ba II oder Na I ) zur Templatbildung von [2]Rotaxanen.…”

“…Die CuAAC-Klickreaktion ist weiterhin von grçßtem Interesse als eine Methode zum kovalenten Einfang, [88] und viele der obigen Beispiele nutzen diese vielseitige Reaktion aus. [344,345,348,353,372] Inspiriert durch Sauvages Strategie zum Aufbau komplexer molekularer Topologien durch Verschlingung der Endgruppen verflochtener Metallkomplexe (Abbildung 5), [115] die richtungsweisenden Arbeiten Lehns zur Entwicklung zirkulärer Helicate (Schema 4) [59] sowie durch viele der Strategien und Taktiken, die in diesem Aufsatz diskutiert wurden (Abschnitte 1.1, 1.2 und 1.3), wurde der erste synthetische molekulare Fünffachknoten mittels metall-und anionengelenkter Selbstorganisation in Kombination mit reversibler Imin-Bildung hergestellt. [373] Mehr als sechs Milliarden Primknoten sind in der Mathematik bekannt.…”

CuII‐Templated Threading of a Bis‐amide‐tris‐amine Macrocycle by Substituted 2,2′‐Bipyridyl Derivatives Assisted by Strong π–π Stacking and Second‐Sphere H‐Bonding Interactions

“…[1][2][3][4][5][6][7][8][9][10][11] Thus, template methods have provided opportunities to develop different complicated threaded structures with many interesting properties. [1][2][3][4][5][6][7][8][9][10][11] Thus, template methods have provided opportunities to develop different complicated threaded structures with many interesting properties.…”