Editing Polycatenane (section)

=== Synthesis ===
The synthesis of polycatenanes is considered a challenging task with most of the reported examples being in the solution state and very few in the solid state.<ref>{{Cite journal |last=Marti-Rujas, J.; Elli, S.; Sacchetti, A.; Castiglione, F. |date=2022 |title=Mechanochemical synthesis of mechanical bonds in M12L8 poly-[n]-catenanes |url=https://pubs.rsc.org/en/content/articlelanding/2022/dt/d1dt03158a |journal=Dalton Transactions |volume=51 |issue=1 |pages=53–58|doi= 10.1039/D1DT03158A|pmid= 34889335|url-access=subscription }}</ref> The formation of poly-[''2'']-catenanes can be achieved by polymerisation of functionalised [''2'']-catenanes.<ref name=":9">{{Cite journal |last1=Li |first1=Ziyong |last2=Liu |first2=Wenju |last3=Wu |first3=Jishan |last4=Liu |first4=Sheng Hua |last5=Yin |first5=Jun |date=2012-08-17 |title=Synthesis of [2]Catenanes by Template-Directed Clipping Approach |url=https://pubs.acs.org/doi/10.1021/jo3012804 |journal=The Journal of Organic Chemistry |language=en |volume=77 |issue=16 |pages=7129–7135 |doi=10.1021/jo3012804 |issn=0022-3263 |pmid=22839768|url-access=subscription }}</ref> Also the synthesis of [''3'']-catenanes, [''5'']-catenanes, [''6'']-catenanes and [''7'']-catenanes is reported in many articles.<ref>{{Cite journal |last1=Fujita |first1=Makoto |last2=Ogura |first2=Katsuyuki |date=March 1996 |title=Self-assembling [2]catenanes: molecular magic rings |journal=Supramolecular Science |volume=3 |issue=1–3 |pages=37–44 |doi=10.1016/0968-5677(96)00004-1 |issn=0968-5677|doi-access=free }}</ref><ref>{{Cite journal |last1=Amabilino |first1=David B. |last2=Ashton |first2=Peter R. |last3=Balzani |first3=Vincenzo |last4=Boyd |first4=Sue E. |last5=Credi |first5=Alberto |last6=Lee |first6=Ju Young |last7=Menzer |first7=Stephan |last8=Stoddart |first8=J. Fraser |last9=Venturi |first9=Margherita |last10=Williams |first10=David J. |date=1998-04-28 |title=Oligocatenanes Made to Order<sup>1</sup> |url=http://dx.doi.org/10.1021/ja9720873 |journal=Journal of the American Chemical Society |volume=120 |issue=18 |pages=4295–4307 |doi=10.1021/ja9720873 |bibcode=1998JAChS.120.4295A |issn=0002-7863|url-access=subscription }}</ref> The synthesis of poly-[''n'']-catenanes has instead some practical issues.<ref>{{Cite journal |last1=Clarkson |first1=Guy J |last2=Leigh |first2=David A |last3=Smith |first3=Richard A |date=1998-12-01 |title=From catenanes to mechanically-linked polymers |url=https://www.sciencedirect.com/science/article/pii/S1359028698800296 |journal=Current Opinion in Solid State and Materials Science |language=en |volume=3 |issue=6 |pages=579–584 |doi=10.1016/S1359-0286(98)80029-6 |bibcode=1998COSSM...3..579C |issn=1359-0286|url-access=subscription }}</ref><ref>{{Cite journal |last1=Liu |first1=Guancen |last2=Rauscher |first2=Phillip M. |last3=Rawe |first3=Benjamin W. |last4=Tranquilli |first4=Marissa M. |last5=Rowan |first5=Stuart J. |date=2022 |title=Polycatenanes: synthesis, characterization, and physical understanding |url=http://xlink.rsc.org/?DOI=D2CS00256F |journal=Chemical Society Reviews |language=en |volume=51 |issue=12 |pages=4928–4948 |doi=10.1039/D2CS00256F |pmid=35611843 |s2cid=249045606 |issn=0306-0012|url-access=subscription }}</ref> To this purpose, [[Molecular dynamics|molecular dynamic simulation]] is very used as a tool for the design of the optimal synthetic path toward the desired product by predicting the final topology.<ref>{{Cite journal |last1=Lei |first1=Huanqing |last2=Zhang |first2=Jianguo |last3=Wang |first3=Liming |last4=Zhang |first4=Guojie |date=2021-01-06 |title=Dimensional and shape properties of a single linear polycatenane: Effect of catenation topology |url=https://www.sciencedirect.com/science/article/pii/S003238612030985X |journal=Polymer |language=en |volume=212 |pages=123160 |doi=10.1016/j.polymer.2020.123160 |issn=0032-3861 |s2cid=228825803|url-access=subscription }}</ref><ref name=":6" />

There are two main synthetic routes: the statistical approach and the template-directed approach.<ref name=":3">{{Cite journal |last1=Raymo |first1=Françisco M. |last2=Stoddart |first2=J. Fraser |date=1999-06-11 |title=Interlocked Macromolecules |url=http://dx.doi.org/10.1021/cr970081q |journal=Chemical Reviews |volume=99 |issue=7 |pages=1643–1664 |doi=10.1021/cr970081q |issn=0009-2665 |pmid=11849006|url-access=subscription }}</ref>

The statistical approach is based on a stochastic methodology.<ref name=":7">{{Cite journal |last1=Agam |first1=Giora |last2=Zilkha |first2=Albert |date=August 1976 |title=Synthesis of a catenane by a statistical double-stage method |url=https://pubs.acs.org/doi/abs/10.1021/ja00433a027 |journal=Journal of the American Chemical Society |language=en |volume=98 |issue=17 |pages=5214–5216 |doi=10.1021/ja00433a027 |bibcode=1976JAChS..98.5214A |issn=0002-7863|url-access=subscription }}</ref><ref name=":8">{{Cite journal |last=Harrison |first=I. T. |date=1972 |title=The effect of ring size on threading reactions of macrocycles |url=http://xlink.rsc.org/?DOI=c39720000231 |journal=Journal of the Chemical Society, Chemical Communications |language=en |issue=4 |pages=231–232 |doi=10.1039/c39720000231 |issn=0022-4936|url-access=subscription }}</ref> When the reactants are together, there is a probability that they will fit together first and then close on top of each other in a process of cyclisation. The catenation of two rings into a catenane is already complex, thus, as expected, the interlocking of multiple cycles into a polycatenane is statistically improbable. Being an unfavored entropically process the product is obtained in very small amounts. Also, the cyclisation process requires high dilutions, but the elongation of the chain is favored at high concentrations, making the synthesis even more difficult.<ref name=":7" /><ref name=":8" />
[[File:Template-Directed Clipping Approach for the Synthesis of Catenanes.gif|thumb|upright=1.5|Example of template-directed clipping approach for the synthesis of catenanes.<ref name=":9"/>]]
The template-directed approach is based on the host-guest interactions that can direct the cyclisation of pre-organised linear unit upon the existing macrocycle.<ref name=":3" /><ref name=":9"/> These interactions can be hydrogen bonds, π-π interactions, hydrophobic interactions or metal ions coordinations. In this way the synthesis can be enthalpy-driven, obtaining quantitative results.<ref name=":3" /><ref name=":9" />

The yield and selectivity are restrained by the kinetic or thermodynamic control of the reaction.<ref>{{Cite journal |last1=Dichtel |first1=William R. |last2=Miljanić |first2=Ognjen Š. |last3=Zhang |first3=Wenyu |last4=Spruell |first4=Jason M. |last5=Patel |first5=Kaushik |last6=Aprahamian |first6=Ivan |last7=Heath |first7=James R. |last8=Stoddart |first8=J. Fraser |date=2008-12-16 |title=Kinetic and Thermodynamic Approaches for the Efficient Formation of Mechanical Bonds |url=https://pubs.acs.org/doi/10.1021/ar800067h |journal=Accounts of Chemical Research |language=en |volume=41 |issue=12 |pages=1750–1761 |doi=10.1021/ar800067h |issn=0001-4842 |pmid=18837521}}</ref>

Generally the kinetic control induces the formation of a product after short reaction times because it is favoued by irreversible reactions (or equilibrium reaction moved very much toward the formation of the products).<ref name="ReferenceA"/> The thermodynamic product is obtained for longer reaction times for reversible processes.<ref>{{Cite journal |last1=Olson |first1=Mark A. |last2=Coskun |first2=Ali |last3=Fang |first3=Lei |last4=Basuray |first4=Ashish N. |last5=Stoddart |first5=J. Fraser |date=2010-04-19 |title=Polycatenation under Thermodynamic Control |url=http://dx.doi.org/10.1002/ange.201000421 |journal=Angewandte Chemie |volume=122 |issue=18 |pages=3219–3224 |bibcode=2010AngCh.122.3219O |doi=10.1002/ange.201000421 |issn=0044-8249|url-access=subscription }}</ref> In this case the units have the time to rearrange themselves toward the most stable state, in a sort of error-checking process. This is obtained by breaking covalent and coordination bonds and forming the most stable ones.<ref>{{Cite journal |last1=Sartori |first1=Pablo |last2=Pigolotti |first2=Simone |date=2015-12-10 |title=Thermodynamics of Error Correction |url=https://link.aps.org/doi/10.1103/PhysRevX.5.041039 |journal=Physical Review X |volume=5 |issue=4 |pages=041039 |arxiv=1504.06407 |bibcode=2015PhRvX...5d1039S |doi=10.1103/PhysRevX.5.041039 |s2cid=14086928}}</ref>