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Theoretical studies of O 2 − :(H 2 O) n clusters
Author(s) -
Curtiss Larry A.,
Melendres Carlos A.,
Reed Alan E.,
Weinhold Frank
Publication year - 1986
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.540070307
Subject(s) - chemistry , binding energy , molecule , crystallography , hydrogen bond , cluster (spacecraft) , molecular orbital , ab initio , bond length , natural bond orbital , ab initio quantum chemistry methods , ion , computational chemistry , atomic physics , density functional theory , crystal structure , physics , organic chemistry , computer science , programming language
The interaction of superoxide ion O 2 − with up to four water molecules [O 2 − : (H 2 O) n , n = 1, 2, 4] has been investigated using ab initio molecular orbital theory. The binding energy of O 2 − : H 2 O is calculated to be −20.6 kcal/mol in good agreement with gas phase experimental data. At the MP3/6‐31G * level the O 2 − :H 2 O complex has a C 2 v structure with a double (cyclic) hydrogen bond between O 2 − and H 2 O. A C s structure with a single hydrogen bond is only 0.7 kcal/mol less stable. Interaction of H 2 O with the doubly occupied π * orbital of O 2 − is preferred slightly over interaction with the singly occupied π * orbital. Natural bond orbital analysis suggests that both electrostatic and charge transfer interactions are important in anionic complexes. The charge transfer occurs predominantly in the O 2 − → H 2 O direction and is important in determining the relative stabilities of the different structures and states. Singly and doubly hydrogen‐bonded structures for the O 2 − : (H 2 O) 2 and O 2 − : (H 2 O) 4 clusters were found to be similar in stability and the increase in binding of the cluster becomes smaller as each additional water molecule is added to the cluster.