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Structures and electron affinities of the di‐arsenic fluorides As 2 F n /As 2 F n − ( n = 1–8)
Author(s) -
Kasalová Veronika,
Schaefer Henry F.
Publication year - 2005
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.20171
Subject(s) - electron affinity (data page) , chemistry , molecule , ion , basis set , symmetry (geometry) , crystallography , density functional theory , hypervalent molecule , affinities , atomic physics , computational chemistry , stereochemistry , physics , reagent , geometry , mathematics , organic chemistry
Developments in the preparation of new materials for microelectronics are focusing new attention on molecular systems incorporating several arsenic atoms. A systematic investigation of the As 2 F n /As 2 F n −systems was carried out using Density Functional Theory methods and a DZP++ quality basis set. Global and low‐lying local geometric minima and relative energies are discussed and compared. The three types of neutral‐anion separations reported in this work are: the adiabatic electron affinity ( EA ad ), the vertical electron affinity ( EA vert ), and the vertical detachment energy ( VDE ). Harmonic vibrational frequencies pertaining to the global minimum for each compound are reported. From the first four studied species (As 2 F n , n = 1–4), all neutral molecules and their anions are shown to be stable with respect to AsAs bond breaking. The neutral As 2 F molecule and its anion are predicted to have C s symmetry. We find the trans FAsAsF isomer of C 2h symmetry and a pyramidalized vinylidene‐like AsAsF 2 −isomer of C s symmetry to be the global minima for the As 2 F 2 and As 2 F 2 −species, respectively. The lowest lying minima of As 2 F 3 and As 2 F 3 −are vinyl radical‐like structures FAsAsF 2 of C s symmetry. The neutral As 2 F 4 global minimum is a trans ‐bent (like Si 2 H 4 ) F 2 AsAsF 2 isomer of C 2 symmetry, while its anion is predicted to have an unusual fluorine‐bridged (C 1 ) structure. The global minima of the neutral As 2 F n species, n = 5–8, are weakly bound complexes, held together by dipole–dipole interactions. All such structures have the AsF m AsF n form, where (m,n) is (2,3) for As 2 F 5 , (3,3) for As 2 F 6 , (4,3) for As 2 F 7 , and (5,3) for As 2 F 8 . For As 2 F 8 the beautiful pentavalent F 4 AsAsF 4 structure (analogous to the stable AsF 5 molecule) lies about 30 kcal/mol above the AsF 3 · · · AsF 5 complex. The stability of AsF 5 depends crucially on the strong AsF bonds, and replacing one of these with an AsAs bond (in F 4 AsAsF 4 ) has a very negative impact on the molecule's stability. The anions As 2 F n − , n = 5–8, are shown to be stable with respect to the AsAs bond breaking, and we predict that all of them have fluorine‐bridged or fluorine‐linked structures. The zero‐point vibrational energy corrected adiabatic electron affinities are predicted to be 2.28 eV (As 2 F), 1.95 eV (As 2 F 2 ), 2.39 eV (As 2 F 3 ), 1.71 eV (As 2 F 4 ), 2.72 eV (As 2 F 5 ), 1.79 eV (As 2 F 6 ), 5.26 eV (As 2 F 7 ), and 3.40 eV (As 2 F 8 ) from the BHLYP method. Vertical detachment energies are rather large, especially for species with fluorine‐bridged global minima, having values up to 6.45 eV (As 2 F 7 , BHLYP). © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 411–435, 2005