Analysis of 2D+2D→2D borromean entanglement in GUWXIF, [Ni(μ3-cyc)]3L2·6G·4H2O (cyc = cyclam, L = (1,3,5-tris(2-(4-carboxyphenyl)-1-ethynyl)benzene), G = pyridine)
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1. Go to the GUWXIF record and do the same procedures as in Example 2, but also delete 0,1,2-coordinated nodes. You should get an output like follows.
You notice that “Polycatenation” is no more detected, we only see that nets have the topology hcb (honeycomb), BUT pay attention that there are no Hopf links in the array, so any pair of the nets do not catenate each other. The nets has the same orientation (102) and, hence, are parallel. This is a sign of a possible borromean entanglement. You should check carefully with IsoCryst to confirm the borromean nature of the entanglement. Read more about borromean entanglements in “Borromean links and other non-conventional links in ‘polycatenated’coordination polymers: re-examination of some puzzling networks” L. Carlucci, G. Ciani, D. M. Proserpio CrystEngComm, 2003, 5(47), 269–279.
2. Run IsoCryst and specify all Translations parameters equal to 1 since not all nets have atoms in the initial unit cell. Grow the structure several times to see layers.
Rotate structure to orient the layers vertically, toggle to Select atoms in a rectangle region mode and select a set of parallel layers.
Perform Show selection only command and orient the layers along the (102) direction. For this purpose, click the button and enter 1,0,2. Then grow the structure if required and paint the three entangled nets with different colors.
We have so-called borromean entanglement when any pair of the three nets do not catenate each other (have no Hopf links), but they are interlinked by a third net. 0D examples of the Hopf link and the borromean link are shown below.
Exercise: Study the entanglement in the crystal structure of AJOSUN, ZnLaLb(H2O); (μ2-terephthalato-O,O')-(μ2-1,4-diazabicyclo(2.2.2)octane-N,N')-aqua-Zn. Is it polycatenation or interpenetration?
Answer: Net topology is sql; 2-fold interpenetration, layers are parallel in orientation 0,1,0; Hopf links is for 4-rings.