Chemistry - Do molecules with bridges through rings exist?

Solution 1:

I'm not sure about the existence of molecules with bridges through rings. However, there are several publications of synthesis of molecules mimicking wheels and axles ([2]rotaxanes; The “[2]” refers to the number of interlocked components) as one shown below (Ref. 1):

Wheel & Axle in OC (The diagram is from Reference 1)

This specific molecule (8; an “impossible” [2]rotaxane) represents a macro-cycle with a straight-chain molecule with bulky end groups going through its center. The inclusion of two bulky end groups prevents the straight-chain molecule leaving the macro-cycle (mechanically interlocked) as depicted in the diagram (See Ref. 2 for the total synthesis of the molecule).

Note that Ref. 1 also cited articles for the synthesis of [2]catenanes, which contain two interlocked rings (instead of one axle and one macrocycle). Keep in mind that there are some advanced catenanes and rotaxanes that exist (e.g., [3]catenanes and [3]rotaxanes).

catenanes (The structures are from Reference 1)


  1. Edward A. Neal, Stephen M. Goldup, "Chemical consequences of mechanical bonding in catenanes and rotaxanes: isomerism, modification, catalysis and molecular machines for synthesis," Chem. Commun. 2014, 50(40), 5128-5142 (
  2. Jeffrey S. Hannam, Stephen M. Lacy, David A. Leigh, Carlos G. Saiz, Alexandra M. Z. Slawin, Sheila G. Stitchell, "Controlled Submolecular Translational Motion in Synthesis: A Mechanically Interlocking Auxiliary," Angew. Chem., Intl. Fd. 2004, 43(25), 3260-3264 (

Solution 2:

A variation on this theme is Ice VII, in which two cubic ice structures are intertwined with hydrogen bonds from each component structure passing through the hydrogen-bonded rings formed by the other component. Known to occur naturally on Earth as a high-pressure phase trapped in diamonds, Ice VII is a stepping-stone to the macromolecular and superionic ices believed to exist in some giant planets.

enter image description here


Solution 3:

Ring-opening polymerization, in particular using olefin metathesis which keeps growing closed rings in the absence of linear olefins, will produce macrocycles that are intertwined to form a pseudo cross-linked network, globally insoluble polymer. This can be later "un-crosslinked" by resuming the metathesis reaction with linear olefins.