View source for Superatom

{{short description|Atom cluster that exhibits properties of elemental atoms}}

In [[chemistry]], a '''superatom''' is any [[cluster chemistry|cluster]] of [[atom]]s that seem to exhibit some of the properties of elemental atoms.<ref>{{cite journal |last1=Ariyarathna |first1=Isuru R. |title=Superatomic Chelates: The Cases of Metal Aza-Crown Ethers and Cryptands |journal=Inorganic Chemistry |date=21 December 2021 |volume=61 |issue=1 |pages=579–585 |doi=10.1021/acs.inorgchem.1c03261|pmid=34932345 }}</ref> One example of a superatom is the cluster {{chem|Al|13|4=−}}.<ref>{{Cite web |title=Developing Superatom Science |url=https://cen.acs.org/articles/91/i15/Developing-Superatom-Science.html |access-date=2024-12-21 |website=Chemical & Engineering News |language=en}}</ref>

[[Sodium]] atoms, when cooled from [[vapor]], naturally condense into clusters, preferentially containing a [[magic number (chemistry)|magic number]] of atoms (2, 8, 20, 40, 58, etc.), with the outermost [[electron]] of each atom entering an [[Atomic orbital|orbital]] encompassing all the atoms in the cluster. Superatoms tend to behave chemically in a way that will allow them to have a [[closed shell]] of electrons, in this new counting scheme.{{cn|date=March 2021}}

==Aluminium clusters==
Certain [[aluminium]] [[cluster chemistry|clusters]] have superatom properties. These aluminium clusters are generated as [[anions]] ({{chem|Al|''n''|−}} with ''n'' = 1, 2, 3, … ) in [[helium]] gas and reacted with a gas containing iodine. When analyzed by [[mass spectrometry]] one main reaction product turns out to be {{chem|Al|13|I|−}}.<ref name="bergeron/2004">{{cite journal | last=Bergeron | first=D. E. | title=Formation of {{chem|Al|13|I|−}}: Evidence for the Superhalogen Character of Al13 | journal=[[Science (journal)|Science]] | publisher=American Association for the Advancement of Science (AAAS) | volume=304 | issue=5667 | date=2 April 2004 | issn=0036-8075 | doi=10.1126/science.1093902 | pmid=15066775 | pages=84–87| s2cid=26728239 }}</ref> These clusters of 13 aluminium atoms with an extra electron added do not appear to react with [[oxygen]] when it is introduced in the same gas stream, indicating a halide-like character and a magic number of 40 free electrons. Such a cluster is known as a '''superhalogen'''.<ref>{{Cite journal|last1=Reddy|first1=G. Naaresh|last2=Parida|first2=Rakesh|last3=Giri|first3=Santanab|date=2017-12-12|title=Functionalized deltahedral Zintl complexes Ge9R3 (R = CF<sub>3</sub>, CN, and NO<sub>2</sub>): a new class of superhalogens|journal=Chemical Communications|language=en|volume=53|issue=99|pages=13229–13232|doi=10.1039/C7CC08120K|pmid=29182179|issn=1364-548X}}</ref><ref>{{Cite journal|last1=Giri|first1=Santanab|last2=Child|first2=Brandon Z.|last3=Jena|first3=Puru|date=2014|title=Organic Superhalogens|journal=ChemPhysChem|language=en|volume=15|issue=14|pages=2903–2908|doi=10.1002/cphc.201402472|pmid=25056518|issn=1439-7641}}</ref><ref>{{Cite journal|last1=Reddy|first1=Gorre Naaresh|last2=Giri|first2=Santanab|date=2016-05-10|title=Super/hyperhalogen aromatic heterocyclic compounds|journal=RSC Advances|language=en|volume=6|issue=52|pages=47145–47150|doi=10.1039/C6RA08625J|bibcode=2016RSCAd...647145R|issn=2046-2069}}</ref><ref>{{Cite journal |last1=Sinha |first1=Swapan |last2=Jena |first2=Puru |last3=Giri |first3=Santanab |date=2022-08-12 |title=Functionalized nona-silicide [Si9R3] Zintl clusters: a new class of superhalogens |journal=Physical Chemistry Chemical Physics |volume=24 |issue=35 |pages=21105–21111 |language=en |doi=10.1039/D2CP02619H |pmid=36018293 |bibcode=2022PCCP...2421105S |osti=1978872 |s2cid=251551751 |issn=1463-9084}}</ref> The cluster component in {{chem|Al|13|I|−}} ion is similar to an [[iodide]] ion or better still a [[bromide]] ion. The related {{chem|Al|13|I|2|−}} cluster is expected to behave chemically like the [[triiodide]] ion.<ref name="bergeron/2004"/>

Similarly it has been noted that {{chem|Al|14}} clusters with 42 electrons (2 more than the magic numbers) appear to exhibit the properties of an [[alkaline earth metal]] which typically adopt +2 [[Valence (chemistry)|valence]] states. This is only known to occur when there are at least 3 iodine atoms attached to an {{chem|Al|14|−}} cluster, {{chem|Al|14|I|3|−}}. The [[anionic]] cluster has a total of 43 itinerant electrons, but the three iodine atoms each remove one of the itinerant electrons to leave 40 electrons in the [[jellium]] shell.<ref name="ball">Philip Ball, "A New Kind of Alchemy", ''[[New Scientist]]'' Issue dated 2005-04-16.</ref><ref name="bergeron/2005">{{cite journal | last=Bergeron | first=D. E. | title=Al Cluster Superatoms as Halogens in Polyhalides and as Alkaline Earths in Iodide Salts | journal=[[Science (journal)|Science]] | publisher=American Association for the Advancement of Science (AAAS) | volume=307 | issue=5707 | date=14 January 2005 | issn=0036-8075 | doi=10.1126/science.1105820 | pages=231–235| pmid=15653497 | bibcode=2005Sci...307..231B | s2cid=8003390 }}</ref>

It is particularly easy and reliable to study atomic clusters of inert gas atoms by computer simulation because interaction between two atoms can be approximated very well by the [[Lennard-Jones potential]]. Other methods are readily available and it has been established that the [[magic number (chemistry)|magic number]]s are 13, 19, 23, 26, 29, 32, 34, 43, 46, 49, 55, etc.<ref>{{cite journal | last1=Harris | first1=I. A. | last2=Kidwell | first2=R. S. | last3=Northby | first3=J. A. | title=Structure of Charged Argon Clusters Formed in a Free Jet Expansion | journal=Physical Review Letters | publisher=American Physical Society (APS) | volume=53 | issue=25 | date=17 December 1984 | issn=0031-9007 | doi=10.1103/physrevlett.53.2390 | pages=2390–2393| bibcode=1984PhRvL..53.2390H | s2cid=13793440 | url=https://digitalcommons.uri.edu/cgi/viewcontent.cgi?article=1209&context=phys_facpubs | url-access=subscription }}</ref>

* {{chem|Al|7}} = the property is similar to [[germanium]] atoms.
* {{chem|Al|13}} = the property is similar to [[halogen]] atoms, more specifically, [[chlorine]].
** {{chem|Al|13|I|''x''|−}}, where {{chem|1=''x'' = 1–13}}.<ref name="N.O.Jones">[http://etd.vcu.edu/theses/available/etd-01102007-131059/unrestricted/jonesno_phd.pdf Naiche Owen Jones, 2006.]{{Dead link|date=June 2018 |bot=InternetArchiveBot |fix-attempted=no }}</ref>{{unreliable source|date=January 2025}}
* {{chem|Al|14}} = the property is similar to [[alkaline earth metal]]s.
** {{chem|Al|14|I|''x''|−}}, where {{chem|1=''x'' = 1–14}}.<ref name="N.O.Jones"/>
* {{chem|Al|23}}
* {{chem|Al|37}}
* {{chem|Al|5|O|4|-}}<ref> {{cite journal | title=Al5O4 Superatom with Potential for New Materials Design | year = 2008| doi = 10.1021/ct800232b| last1 = Das| first1 = Ujjal| last2 = Raghavachari| first2 = Krishnan| journal = Journal of Chemical Theory and Computation| volume = 4| issue = 12| pages = 2011–2019| pmid = 26620474}} </ref>

==Other clusters==
* {{chem2|Li(HF)3Li}} = the {{chem2|(HF)3}} interior causes 2 valence electrons from the Li to orbit the entire molecule as if it were an atom's nucleus.<ref>{{cite journal | last1=Sun | first1=Xiao-Ying | last2=Li | first2=Zhi-Ru | last3=Wu | first3=Di | last4=Sun | first4=Chia-Chung | title=Extraordinary superatom containing double shell nucleus: Li(HF)<sub>3</sub>Li connected mainly by intermolecular interactions | journal=International Journal of Quantum Chemistry | publisher=Wiley | volume=107 | issue=5 | year=2007 | issn=0020-7608 | doi=10.1002/qua.21246 | pages=1215–1222| bibcode=2007IJQC..107.1215S }}</ref>
* {{chem2|Li(NH3)4}} = has one diffuse electron orbiting around {{chem2|Li(NH3)4+}} core, i.e., mimics an alkali-metal atom.<ref>{{Cite journal|last1=Ariyarathna|first1=Isuru R.|last2=Pawłowski|first2=Filip|last3=Ortiz|first3=Joseph Vincent|last4=Miliordos|first4=Evangelos|date=2018|title=Molecules mimicking atoms: monomers and dimers of alkali metal solvated electron precursors|journal=Physical Chemistry Chemical Physics|language=en|volume=20|issue=37|pages=24186–24191|doi=10.1039/C8CP05497E|pmid=30209476|bibcode=2018PCCP...2024186A|issn=1463-9076}}</ref><ref name="thesis">{{Cite thesis|last=Ariyarathna|first=Isuru|date=2021-03-01|title=First Principle Studies on Ground and Excited Electronic States: Chemical Bonding in Main-Group Molecules, Molecular Systems with Diffuse Electrons, and Water Activation using Transition Metal Monoxides|degree=PhD|url=https://etd.auburn.edu//handle/10415/7601|language=en}}</ref>{{unreliable source|date=January 2025}}
* {{chem2|Be(NH3)4}} = has two diffuse electrons orbiting around {{chem2|Be(NH3)4(2+)}} core, i.e., mimics He-atom.<ref>{{Cite journal|last1=Ariyarathna|first1=Isuru R.|last2=Khan|first2=Shahriar N.|last3=Pawłowski|first3=Filip|last4=Ortiz|first4=Joseph Vincent|last5=Miliordos|first5=Evangelos|date=2018-01-04|title=Aufbau Rules for Solvated Electron Precursors: Be(NH<sub>3</sub>)<sub>4</sub><sup>2+</sup> Complexes and Beyond|journal=The Journal of Physical Chemistry Letters|language=en|volume=9|issue=1|pages=84–88|doi=10.1021/acs.jpclett.7b03000|pmid=29232138|issn=1948-7185|doi-access=free}}</ref><ref name="thesis"/>

* {{chem2|VSi16F}} = has ionic bonding.<ref>{{cite journal | last1=Koyasu | first1=Kiichirou | last2=Atobe | first2=Junko | last3=Akutsu | first3=Minoru | last4=Mitsui | first4=Masaaki | last5=Nakajima | first5=Atsushi | title=Electronic and Geometric Stabilities of Clusters with Transition Metal Encapsulated by Silicon | journal=The Journal of Physical Chemistry A | publisher=American Chemical Society (ACS) | volume=111 | issue=1 | year=2007 | issn=1089-5639 | doi=10.1021/jp066757f | pages=42–49|pmid=17201386| bibcode=2007JPCA..111...42K}}</ref>
* A cluster of 13 [[platinum]] atoms becomes highly [[paramagnetic]], much more so than platinum itself.<ref>[http://nanotechweb.org/cws/article/tech/26782 Platinum nanoclusters go magnetic] {{Webarchive|url=https://web.archive.org/web/20071015064232/http://nanotechweb.org/cws/article/tech/26782 |date=2007-10-15}}, nanotechweb.org, 2007</ref>

==Superatom complexes==
Superatom complexes are a special group of superatoms that incorporate a metal core which is stabilized by organic ligands. In [[thiolate-protected gold cluster]] complexes, a simple electron counting rule can be used to determine the total number of electrons ({{mvar|n<sub>e</sub>}}) which correspond to a [[magic number (chemistry)|magic number]]:

:<math>n_e = N\nu_A - M -z</math>

where {{mvar|N}} is the number of metal atoms (A) in the core, {{mvar|v}} is the atomic valence, {{mvar|M}} is the number of electron withdrawing ligands, and {{mvar|z}} is the overall charge on the complex.<ref>{{cite journal | last1=Walter | first1=M. | last2=Akola | first2=J. | last3=Lopez-Acevedo | first3=O. | last4=Jadzinsky | first4=P. D. | last5=Calero | first5=G. | last6=Ackerson | first6=C. J. | last7=Whetten | first7=R. L. | last8=Gronbeck | first8=H. | last9=Hakkinen | first9=H. | title=A unified view of ligand-protected gold clusters as superatom complexes | journal=Proceedings of the National Academy of Sciences | volume=105 | issue=27 | date=1 June 2008 | issn=0027-8424 | doi=10.1073/pnas.0801001105 | pages=9157–9162| pmid=18599443 | pmc=2442568 | bibcode=2008PNAS..105.9157W |doi-access=free}}</ref> For example the Au<sub>102</sub>(p-MBA)<sub>44</sub> has 58 electrons and corresponds to a closed shell magic number.<ref>{{cite journal | last1=Jadzinsky | first1=P. D. | last2=Calero | first2=G. | last3=Ackerson | first3=C. J. | last4=Bushnell | first4=D. A. | last5=Kornberg | first5=R. D. | title=Structure of a Thiol Monolayer-Protected Gold Nanoparticle at 1.1 Å Resolution | journal=Science | publisher=American Association for the Advancement of Science (AAAS) | volume=318 | issue=5849 | date=19 October 2007 | issn=0036-8075 | doi=10.1126/science.1148624 | pmid=17947577 | pages=430–433| bibcode=2007Sci...318..430J | s2cid=1566019 }}</ref>

===Gold superatom complexes===
* {{chem2|Au25(SMe)18-}}<ref>{{cite journal | last1=Akola | first1=Jaakko | last2=Walter | first2=Michael | last3=Whetten | first3=Robert L. | last4=Häkkinen | first4=Hannu | last5=Grönbeck | first5=Henrik | title=On the Structure of Thiolate-Protected Au<sub>25</sub> | journal=[[Journal of the American Chemical Society]] | volume=130 | issue=12 | year=2008 | issn=0002-7863 | doi=10.1021/ja800594p | pmid=18321117 | pages=3756–3757| bibcode=2008JAChS.130.3756A }}</ref>
* {{chem2|Au102([[4-Mercaptobenzoic acid|''p''\-MBA]])44}}<ref>{{cite journal |last1=Levi-Kalisman |first1=Yael |last2=Jadzinsky |first2=Pablo D. |last3=Kalisman |first3=Nir |last4=Tsunoyama |first4=Hironori |last5=Tsukuda |first5=Tatsuya |last6=Bushnell |first6=David A. |last7=Kornberg |first7=Roger D. |author-link7=Roger D. Kornberg |title=Synthesis and Characterization of Au<sub>102</sub>(''p''-MBA)<sub>44</sub> Nanoparticles |journal=[[Journal of the American Chemical Society]] |date=9 March 2011 |volume=133 |issue=9 |pages=2976–2982 |doi=10.1021/ja109131w|pmid=21319754 |bibcode=2011JAChS.133.2976L }}</ref>
* {{chem2|Au144(SR)60}}<ref>{{cite journal | last1=Lopez-Acevedo | first1=Olga | last2=Akola | first2=Jaakko | last3=Whetten | first3=Robert L. | last4=Grönbeck | first4=Henrik | last5=Häkkinen | first5=Hannu |author-link5=Hannu Häkkinen | title=Structure and Bonding in the Ubiquitous Icosahedral Metallic Gold Cluster Au<sub>144</sub>(SR)<sub>60</sub> | journal=[[The Journal of Physical Chemistry C]] | publisher=[[American Chemical Society]] | volume=113 | issue=13 | date=16 January 2009 | issn=1932-7447 | doi=10.1021/jp8115098 | pages=5035–5038 }}</ref>

===Other superatom complexes===
* {{chem2|Ga23(N(Si(CH3)3)2)11}}<ref>{{cite journal | last1=Hartig | first1=Jens | last2=Stößer | first2=Anna | last3=Hauser | first3=Petra | last4=Schnöckel | first4=Hansgeorg | title=A Metalloid Ga<sub>23</sub>{N(SiMe<sub>3</sub>)<sub>2</sub>}<sub>11</sub> Cluster: The Jellium Model Put to Test | journal=Angewandte Chemie International Edition | publisher=Wiley | volume=46 | issue=10 | date=26 February 2007 | issn=1433-7851 | doi=10.1002/anie.200604311 | pmid=17230594 | pages=1658–1662}}</ref>
* {{chem2|Al50(C5(CH3)5)12}}<ref>{{cite journal | last1=Clayborne | first1=Peneé A. | last2=Lopez-Acevedo | first2=Olga | last3=Whetten | first3=Robert L. | last4=Grönbeck | first4=Henrik | last5=Häkkinen | first5=Hannu | title=The Al<sub>50</sub>Cp*<sub>12</sub> Cluster – A 138-Electron Closed Shell (L = 6) Superatom | journal=European Journal of Inorganic Chemistry | publisher=Wiley | volume=2011 | issue=17 | date=13 May 2011 | issn=1434-1948 | doi=10.1002/ejic.201100374 | pages=2649–2652}}</ref>
* {{chem2|Re6Se8Cl2}} – In 2018 researchers produced 15-nm-thick flakes of this superatomic material. They anticipate that a monolayer will be a superatomic 2-D semiconductor and offer  new  2-D materials with unusual, tunable properties.<ref>{{Cite news|url=https://phys.org/news/2018-02-superatomic-d-semiconductor.html#jCp|title=Researchers create first superatomic 2-D semiconductor|last=Zyga|first=Lisa|work=Phys.org|access-date=2018-02-18}}</ref>
*Organo− Zintl-based superatoms: [{{chem2|Ge9(CHO)3}}] and [{{chem2|Ge9(CHO)}}]<ref>{{Cite journal|date=2017-10-16|title=Organo−Zintl-based superatoms: [Ge<sub>9</sub>(CHO)<sub>3</sub>] and [Ge<sub>9</sub>(CHO)]|journal=Chemical Physics Letters|language=en|volume=686|pages=195–202|doi=10.1016/j.cplett.2017.08.056|issn=0009-2614|last1=Reddy|first1=G. Naaresh|last2=Jena|first2=Puru|last3=Giri|first3=Santanab|bibcode=2017CPL...686..195R|doi-access=free}}</ref>
* {{chem2|[Cu43Al12](Cp\*)12|link=Heterometallic copper-aluminum superatom}}<ref>{{cite journal |doi=10.1002/anie.201806039 |pmid=29981271 |title=The Mackay-Type Cluster &#91;Cu<sub>43</sub> Al<sub>12</sub> &#93;(Cp*)<sub>12</sub> : Open-Shell 67-Electron Superatom with Emerging Metal-Like Electronic Structure |journal=Angewandte Chemie International Edition |volume=57 |issue=44 |pages=14630–14634 |year=2018 |last1=Weßing |first1=Jana |last2=Ganesamoorthy |first2=Chelladurai |last3=Kahlal |first3=Samia |last4=Marchal |first4=Rémi |last5=Gemel |first5=Christian |last6=Cador |first6=Olivier |last7=Da Silva |first7=Augusto C. H. |last8=Da Silva |first8=Juarez L. F. |last9=Saillard |first9=Jean-Yves |last10=Fischer |first10=Roland A. |s2cid=49714793 |url=https://hal-univ-rennes1.archives-ouvertes.fr/hal-01834003/file/We%C3%9Fing%20et%20al_The%20Mackay-type%20cluster%20%5BCu43Al12%5D%28Cp%2912.pdf }}</ref>

==See also==
{{Portal|Physics}}
* [[Bose–Einstein condensate]]
* [[Catenation]]
* [[Metal aromaticity]]
* [[Quantum dot]]

==References==
{{Reflist}}

* "Designer Magnetic Superatoms", J.U. Reveles, et al. 2009 {{doi|10.1038/nchem.249}}
* "A unified view of ligand-protected gold clusters as superatom complexes", M. Walter et al. 2008 {{doi|10.1073/pnas.0801001105}}
* "Gold Superatom Complexes", P.D. Jadzinsky et al. 2007 {{doi|10.1126/science.1148624}}
* "Multiple Valence Superatoms", J.U. Reveles, S.N. Khanna, P.J. Roach, and A.W. Castleman Jr., 2006 {{doi|10.1073/pnas.060878110}}

{{Particles}}

[[Category:Cluster chemistry]]
[[Category:Quantum chemistry]]
[[Category:Atoms]]