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<title>Pi-interaction</title>

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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Pi-interaction</span></span>

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<p>In chemistry, <b>π-effects</b> or <b>π-interactions</b> are a type of non-covalent interaction that involves <a href="Pi_bond" title="Pi bond">π systems</a>. Just like in an electrostatic interaction where a region of negative charge interacts with a positive charge, the electron-rich π system can interact with a metal (cationic or neutral), an anion, another molecule and even another π system.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> Non-covalent interactions involving π systems are pivotal to biological events such as protein-ligand recognition.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading2"><h2 id="Types">Types</h2></div>

<p>The most common types of π-interactions involve:

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<ul><li>Metal–π interactions: involves interaction of a metal and the face of a π system, the metal can be a cation (known as <a href="Cation%E2%80%93pi_interaction" class="mw-redirect" title="Cation–pi interaction">cation–π interactions</a>) or neutral</li>

<li>Polar–π interactions: involves interaction of a polar molecule and quadrupole moment a π system.</li></ul>

<ul><li><a href="Pi_stacking" class="mw-redirect" title="Pi stacking">Aromatic–aromatic interactions</a> (π stacking): involves interactions of aromatic molecules with each other.

<ul><li>Arene–perfluoroarene interaction: electron-rich benzene ring interacts with electron-poor <a href="Hexafluorobenzene" title="Hexafluorobenzene">hexafluorobenzene</a>.</li></ul></li></ul>

<ul><li>π donor–acceptor interactions: interaction between low energy empty orbital (acceptor) and a high-energy filled orbital (donor).</li></ul>

<ul><li>Anion–π interactions: interaction of anion with π system</li>

<li><a href="Cation%E2%80%93pi_interaction" class="mw-redirect" title="Cation–pi interaction">Cation–π</a> interactions: interaction of a cation with a π system</li>

<li>C–H–π interactions: interaction of C-H with π system: These interactions are well studied using experimental as well as computational techniques.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup></li></ul>

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<div class="mw-heading mw-heading2"><h2 id="Examples">Examples</h2></div>

<li class="gallerycaption">Pi-stacking Examples</li>

<div class="gallerytext">A <a href="Fullerene" title="Fullerene">fullerene</a> bound in a <a href="Molecular_tweezers" title="Molecular tweezers">buckycatcher</a> through aromatic stacking interactions.<sup id="cite_ref-sygula_8-0" class="reference"><a href="#cite_note-sygula-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup></div>

</li>

<div class="gallerytext">The Stoddart synthesis of [2] catenane...</div>

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<div class="gallerytext"><a href="Tacrine" title="Tacrine">Tacrine</a> bound to acetylcholinesterase (PDB 1ACJ). A pi stacking interaction between tacrine (blue) and Trp84 (red) is proposed</div>

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<div class="gallerytext">Polar π interaction between water molecule and benzene</div>

</li>

<div class="gallerytext">Arene perfluoroarene stacking</div>

</li>

<div class="gallerytext">Edge-on view of portion of crystal structure of hexamethylene<a href="Tetrathiafulvene" class="mw-redirect" title="Tetrathiafulvene">TTF</a>/TCNQ charge transfer salt, highlighting the segregated stacking.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup></div>

</li>

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<div class="mw-heading mw-heading2"><h2 id="Graphite">Graphite</h2></div>

<p><a href="Graphite" title="Graphite">Graphite</a> consists of stacked sheets of covalently bonded carbon.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> The individual layers are called <a href="Graphene" title="Graphene">graphene</a>. In each layer, each carbon atom is bonded to three other atoms forming a continuous layer of sp<sup>2</sup> bonded carbon hexagons, like a <a href="Honeycomb_lattice" class="mw-redirect" title="Honeycomb lattice">honeycomb lattice</a> with a bond length of 0.142 nm, and the distance between planes is 0.335 nm.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading3"><h3 id="π-effects_in_biological_systems">π-effects in biological systems</h3></div>

<p>Cation-π interactions are important for the <a href="Acetylcholine" title="Acetylcholine">acetylcholine</a> (Ach) neurotransmitter.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> The structure of <a href="Cholinesterase" title="Cholinesterase">acetylcholine esterase</a> includes 14 highly conserved aromatic residues. The trimethyl ammonium group of Ach binds to the aromatic residue of <a href="Tryptophan" title="Tryptophan">tryptophan</a> (Trp). The indole site provides a much more intense region of negative electrostatic potential than benzene and phenol residue of Phe and Tyr.

</p><p>Pi–pi and cation–pi interactions are important in rational drug design.<sup id="cite_ref-DrugDesign_15-0" class="reference"><a href="#cite_note-DrugDesign-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> One example is the FDA-approved <a href="Acetylcholinesterase" title="Acetylcholinesterase">acetylcholinesterase</a> (AChE) inhibitor <a href="Tacrine" title="Tacrine">tacrine</a> which is used in the treatment of <a href="Alzheimer's_disease" title="Alzheimer's disease">Alzheimer's disease</a>. Tacrine is proposed to have a pi stacking interaction with the indolic ring of Trp84, and this interaction has been exploited in the rational design of novel AChE inhibitors.<sup id="cite_ref-tacrine_16-0" class="reference"><a href="#cite_note-tacrine-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading3"><h3 id="Supramolecular_assembly">Supramolecular assembly</h3></div>

</mrow>

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<annotation encoding="application/x-tex">{\displaystyle {\ce {\pi - \pi}}}</annotation>

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</math></span><img src="./62f7b528b3aa06ddb8d2397aa46953b82563d526.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:4.472ex; height:2.176ex;" alt="{\displaystyle {\ce {\pi - \pi}}}" loading="lazy"></span>, <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {CH-\pi}}}">

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<annotation encoding="application/x-tex">{\displaystyle {\ce {CH-\pi}}}</annotation>

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</math></span><img src="./4eb1d3add415e728d2f7b97e8a04541d6018f606.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:6.561ex; height:2.343ex;" alt="{\displaystyle {\ce {CH-\pi}}}" loading="lazy"></span> and <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {\pi -cation}}}">

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<mtext>cation</mtext>

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<annotation encoding="application/x-tex">{\displaystyle {\ce {\pi -cation}}}</annotation>

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</math></span><img src="./d180c06a87423e07a066bfc10acb6a02adfb6b5c.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:9.341ex; height:2.343ex;" alt="{\displaystyle {\ce {\pi -cation}}}" loading="lazy"></span> interactions are widely observed motifs in supramolecular assembly and <a href="Molecular_recognition" class="mw-redirect" title="Molecular recognition">recognition</a>.

</p><p><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {\pi-\pi}}}">

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<annotation encoding="application/x-tex">{\displaystyle {\ce {\pi-\pi}}}</annotation>

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</math></span><img src="./9756468878dc0292cdf5b62bb4e329c3be8f42c2.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:4.472ex; height:2.176ex;" alt="{\displaystyle {\ce {\pi-\pi}}}" loading="lazy"></span> concerns the direct interactions between two <span class="texhtml mvar" style="font-style:italic;">π</span>-systems; and <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {cation-\pi}}}">

<mtext>cation</mtext>

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<annotation encoding="application/x-tex">{\displaystyle {\ce {cation-\pi}}}</annotation>

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</math></span><img src="./1938c3ca4c048c9200f4702829b17012ec88dbe1.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:9.341ex; height:2.343ex;" alt="{\displaystyle {\ce {cation-\pi}}}" loading="lazy"></span> interaction arises from the electrostatic interaction of a cation with the face of the <span class="texhtml mvar" style="font-style:italic;">π</span>-system. Unlike these two interactions, the <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {CH-\pi}}}">

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<annotation encoding="application/x-tex">{\displaystyle {\ce {CH-\pi}}}</annotation>

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</math></span><img src="./4eb1d3add415e728d2f7b97e8a04541d6018f606.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:6.561ex; height:2.343ex;" alt="{\displaystyle {\ce {CH-\pi}}}" loading="lazy"></span> interaction arises mainly from charge transfer between the C–H orbital and the <span class="texhtml mvar" style="font-style:italic;">π</span>-system.

</p><p>π systems contribute to <a href="Supramolecular_assembly" class="mw-redirect" title="Supramolecular assembly">supramolecular assembly</a>. Some <a href="Catenane" title="Catenane">catenanes</a> feature π–π interactions. The major challenge for the synthesis of catenane is to interlock molecules in a controlled fashion. Stoddart and co-workers developed a series of systems utilizing the strong π–π interactions between electron-rich benzene derivatives and electron-poor pyridinium rings.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> [2]Catanene was synthesized by reacting bis(pyridinium) (<b>A</b>), bisparaphenylene-34-crown-10 (<b>B</b>), and 1, 4-bis(bromomethyl)benzene (<b>C</b>) (Fig. 2). The π–π interaction between <b>A</b> and <b>B</b> directed the formation of an interlocked template intermediate that was further cyclized by substitution reaction with compound <b>C</b> to generate the [2]catenane product.

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<div class="mw-heading mw-heading3"><h3 id="Charge_transfer_salts">Charge transfer salts</h3></div>

<p>

A combination of <a href="TCNQ" class="mw-redirect" title="TCNQ">tetracyanoquinodimethane</a> (TCNQ) and <a href="Tetrathiafulvalene" title="Tetrathiafulvalene">tetrathiafulvalene</a> (TTF) forms a strong charge-transfer complex referred to as <i>TTF-TCNQ</i>.<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> The solid shows almost metallic electrical conductance. In a TTF-TCNQ crystal, TTF and TCNQ molecules are arranged independently in separate parallel-aligned stacks, and an electron transfer occurs from donor (TTF) to acceptor (TCNQ) stacks.<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup>

</p>

<div class="mw-heading mw-heading2"><h2 id="Anion–π_interactions">Anion–π interactions</h2></div>

<p>Anion and π–aromatic systems (typically electron-deficient) create an interaction that is associated with the repulsive forces of the structures. These repulsive forces involve electrostatic and anion-induced polarized interactions.<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> This force allows for the systems to be used as receptors and channels in supramolecular chemistry for applications in the medical (synthetic membranes, ion channels) and environmental fields (e.g. sensing, removal of ions from water).<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup>

</p><p>The first X-ray crystal structure that depicted anion–π interactions was reported in 2004.<sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> In addition to this being depicted in the solid state, there is also evidence that the interaction is present in solution.<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup>

</p>

<div class="mw-heading mw-heading2"><h2 id="π-effects_in_biological_systems_2">π-effects in biological systems</h2></div>

<p>π-effects have an important contribution to biological systems since they provide a significant amount of binding enthalpy. Neurotransmitters produce most of their biological effect by binding to the active site of a protein receptor. Xation-π interactions are important for the <a href="Acetylcholine" title="Acetylcholine">acetylcholine</a> (Ach) neurotransmitter.<sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> The structure of <a href="Cholinesterase" title="Cholinesterase">cholinesterase</a> includes 14 highly conserved aromatic residues. The trimethyl ammonium group of Ach binds to the aromatic residue of <a href="Tryptophan" title="Tryptophan">tryptophan</a> (Trp). The indole site provides a much more intense region of negative electrostatic potential than benzene and phenol residue of Phe and Tyr.

</p>

<div class="mw-heading mw-heading2"><h2 id="In_supramolecular_assembly">In supramolecular assembly</h2></div>

<p><span class="texhtml mvar" style="font-style:italic;">π</span> systems are important building blocks in <a href="Supramolecular_assembly" class="mw-redirect" title="Supramolecular assembly">supramolecular assembly</a> because of their versatile noncovalent interactions with various functional groups. Particularly, <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {\pi - \pi}}}">

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<annotation encoding="application/x-tex">{\displaystyle {\ce {\pi - \pi}}}</annotation>

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</math></span><img src="./62f7b528b3aa06ddb8d2397aa46953b82563d526.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:4.472ex; height:2.176ex;" alt="{\displaystyle {\ce {\pi - \pi}}}" loading="lazy"></span> , <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {CH-\pi}}}">

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<annotation encoding="application/x-tex">{\displaystyle {\ce {CH-\pi}}}</annotation>

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<mtext>cation</mtext>

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<annotation encoding="application/x-tex">{\displaystyle {\ce {\pi -cation}}}</annotation>

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</math></span><img src="./d180c06a87423e07a066bfc10acb6a02adfb6b5c.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:9.341ex; height:2.343ex;" alt="{\displaystyle {\ce {\pi -cation}}}" loading="lazy"></span> interactions are widely used in supramolecular assembly and <a href="Molecular_recognition" class="mw-redirect" title="Molecular recognition">recognition</a>.

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<annotation encoding="application/x-tex">{\displaystyle {\ce {\pi-\pi}}}</annotation>

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<mtext>cation</mtext>

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<annotation encoding="application/x-tex">{\displaystyle {\ce {cation-\pi}}}</annotation>

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<annotation encoding="application/x-tex">{\displaystyle {\ce {CH-\pi}}}</annotation>

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</math></span><img src="./4eb1d3add415e728d2f7b97e8a04541d6018f606.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:6.561ex; height:2.343ex;" alt="{\displaystyle {\ce {CH-\pi}}}" loading="lazy"></span> interaction arises mainly from charge transfer between the C–H orbital and the <span class="texhtml mvar" style="font-style:italic;">π</span>-system.

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<ul><li><a href="Noncovalent_interaction" class="mw-redirect" title="Noncovalent interaction">Noncovalent interaction</a></li>

<li><a href="Dispersion_(chemistry)" title="Dispersion (chemistry)">Dispersion (chemistry)</a></li>

<li><a href="Cation%E2%80%93pi_interaction" class="mw-redirect" title="Cation–pi interaction">Cation–pi interaction</a></li>

<li><a href="Intercalation_(biochemistry)" title="Intercalation (biochemistry)">Intercalation (biochemistry)</a></li>

<li><a href="Intercalation_(chemistry)" title="Intercalation (chemistry)">Intercalation (chemistry)</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>

/* start https://en.wikipedia.org/ */

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</style><cite id="CITEREFLuoGilsonPotterGilson2001" class="citation journal cs1">Luo R, Gilson HS, Potter MJ, Gilson MK (January 2001). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1301220">"The physical basis of nucleic acid base stacking in water"</a>. <i>Biophysical Journal</i>. <b>80</b> (1): <span class="nowrap">140–</span>148. <a href="Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2001BpJ....80..140L">2001BpJ....80..140L</a>. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2FS0006-3495%2801%2976001-8">10.1016/S0006-3495(01)76001-8</a>. <a href="PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1301220">1301220</a></span>. <a href="PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/11159389">11159389</a>.</cite></li>

<li><a rel="nofollow" class="external text" href="http://www.scs.illinois.edu/denmark/wp-content/uploads/gp/2011/gm-2011-1_18.pdf">Larry Wolf (2011): π-π (π-Stacking) interactions: origin and modulation</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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</li>

</ol></div></div>

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</style><div id="Chemical_bonds164" style="font-size:114%;margin:0 4em"><a href="Chemical_bond" title="Chemical bond">Chemical bonds</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Intramolecular_force" title="Intramolecular force">Intramolecular</a><br>(strong)</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Covalent_bond" title="Covalent bond">Covalent</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Electron_deficiency" title="Electron deficiency">Electron deficiency</a>

<li><a href="Hypervalent_molecule" title="Hypervalent molecule">Hypervalence</a>

<li><a href="Agostic_interaction" title="Agostic interaction">Agostic</a></li>

<li><a href="Coordinate_covalent_bond" title="Coordinate covalent bond">Coordinate (dipolar)</a></li>

<li><a href="Pi_backbonding" title="Pi backbonding">Pi backbond</a></li>

<li><a href="Metal%E2%80%93ligand_multiple_bond" title="Metal–ligand multiple bond">Metal–ligand multiple bond</a></li>

<li><a href="Charge-shift_bond" title="Charge-shift bond">Charge-shift</a></li>

<li><a href="Hapticity" title="Hapticity">Hapticity</a></li>

<li><a href="Conjugated_system" title="Conjugated system">Conjugation</a></li>

<li><a href="Hyperconjugation" title="Hyperconjugation">Hyperconjugation</a></li>

<li><a href="Aromaticity" title="Aromaticity">Aromaticity</a>

<li><a href="Bicycloaromaticity" title="Bicycloaromaticity">bicyclo</a></li></ul></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Metallic_bonding" title="Metallic bonding">Metallic</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Metal_aromaticity" title="Metal aromaticity">Metal aromaticity</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Ionic_bonding" title="Ionic bonding">Ionic</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

</div></td></tr></tbody></table><div></div></td><td class="noviewer navbox-image" rowspan="4" style="width:1px;padding:0 0 0 2px"><div><span typeof="mw:File"></span></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Intermolecular_force" title="Intermolecular force">Intermolecular</a><br>(weak)</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Van_der_Waals_force" title="Van der Waals force">Van der Waals<br>forces</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="London_dispersion_force" title="London dispersion force">London dispersion</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Hydrogen_bond" title="Hydrogen bond">Hydrogen</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Low-barrier_hydrogen_bond" title="Low-barrier hydrogen bond">Low-barrier</a></li>

<li><a href="Resonance-assisted_hydrogen_bond" class="mw-redirect" title="Resonance-assisted hydrogen bond">Resonance-assisted</a></li>

<li><a href="Symmetric_hydrogen_bond" title="Symmetric hydrogen bond">Symmetric</a></li>

<li><a href="Dihydrogen_bond" title="Dihydrogen bond">Dihydrogen bonds</a></li>

<li><a href="C%E2%80%93H%C2%B7%C2%B7%C2%B7O_interaction" title="C–H···O interaction">C–H···O interaction</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Non-covalent_interactions" class="mw-redirect" title="Non-covalent interactions">Noncovalent</a><br>other</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Mechanically_interlocked_molecular_architectures" title="Mechanically interlocked molecular architectures">Mechanical</a></li>

<li><a href="Halogen_bond" title="Halogen bond">Halogen</a></li>

<li><a href="Chalcogen_bond" title="Chalcogen bond">Chalcogen</a></li>

<li><a href="Metallophilic_interaction" title="Metallophilic interaction">Metallophilic</a> (<a href="Aurophilicity" title="Aurophilicity">aurophilic</a>)</li>

<li><a href="Intercalation_(chemistry)" title="Intercalation (chemistry)">Intercalation</a></li>

<li><a href="Stacking_(chemistry)" title="Stacking (chemistry)">Stacking</a></li>

<li><a href="Cation%E2%80%93pi_interaction" class="mw-redirect" title="Cation–pi interaction">Cation–pi</a></li>

<li><a href="Cation%E2%80%93pi_interaction" class="mw-redirect" title="Cation–pi interaction">Anion–pi</a></li>

<li><a href="Salt_bridge_(protein_and_supramolecular)" title="Salt bridge (protein and supramolecular)">Salt bridge</a></li></ul>

</div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Bond_cleavage" title="Bond cleavage">Bond cleavage</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Heterolysis_(chemistry)" title="Heterolysis (chemistry)">Heterolysis</a></li>

<li><a href="Homolysis_(chemistry)" title="Homolysis (chemistry)">Homolysis</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Electron_counting" title="Electron counting">Electron counting</a> rules</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Aromaticity" title="Aromaticity">Aromaticity</a>

<ul><li><a href="H%C3%BCckel's_rule" title="Hückel's rule">Hückel's rule</a></li>

<li><a href="Baird's_rule" title="Baird's rule">Baird's rule</a></li>

<li><a href="M%C3%B6bius_aromaticity" title="Möbius aromaticity">Möbius</a></li>

<li><a href="Spherical_aromaticity" title="Spherical aromaticity">spherical</a></li></ul></li>

<li><a href="Polyhedral_skeletal_electron_pair_theory" title="Polyhedral skeletal electron pair theory">Polyhedral skeletal electron pair theory</a></li>

<li><a href="Jemmis_mno_rules" title="Jemmis mno rules">Jemmis mno rules</a></li></ul>

</div></td></tr></tbody></table></div></div><div><div class="zim-footer">

This article is issued from <a class="external text" title="Last edited on 2025-06-25" href="https://en.wikipedia.org/wiki/?title=Pi-interaction&oldid=1297247972">Wikipedia</a>. The text is available under <a class="external text" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en">Creative Commons Attribution-Share Alike 4.0</a> unless otherwise noted. Additional terms may apply for the media files.

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