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Multiple Aromaticity and Antiaromaticity in Silicon Clusters
Author(s) -
Zhai HuaJin,
Kuznetsov Aleksey E.,
Boldyrev Alexander I.,
Wang LaiSheng
Publication year - 2004
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200400077
Subject(s) - antiaromaticity , aromaticity , chemistry , crystallography , x ray photoelectron spectroscopy , silicon , atom (system on chip) , electronic structure , ab initio , chemical shift , chemical physics , computational chemistry , molecule , nuclear magnetic resonance , physics , organic chemistry , embedded system , computer science
A series of silicon clusters containing four atoms but with different charge states (Si 4 2+ , Si 4 , Si 4 2− , and NaSi 4 − ) were studied by photoelectron spectroscopy and ab initio calculations. Structure evolution and chemical bonding in this series were interpreted in terms of aromaticity and antiaromaticity, which allowed the prediction of how structures of the four‐atom silicon clusters change upon addition or removal of two electrons. It is shown that Si 4 2+ is square‐planar, analogous to the recently discovered aromatic Al 4 2− cluster. Upon addition of two electrons, neutral Si 4 becomes σ ‐antiaromatic and exhibits a rhombus distortion. Adding two more electrons to Si 4 leads to two energetically close structures of Si 4 2− : either a double antiaromatic parallelogram structure or an aromatic system with a butterfly distortion. Because of the electronic instability of doubly charged Si 4 2− , a stabilizing cation (Na + ) was used to produce Si 4 2− in the gas phase in the form of Na + [Si 4 2− ], which was characterized experimentally by photoelectron spectroscopy. Multiple antiaromaticity in the parallelogram Na + [Si 4 2− ] species is highly unusual.