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Electronic Coupling and Electron Transfer between Two Mo 2 Units through meta ‐ and para ‐Phenylene Bridges
Author(s) -
Gao Hang,
Mallick Suman,
Cao Lijiu,
Meng Miao,
Cheng Tao,
Chen Huo Wen,
Liu Chun Y.
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201805866
Subject(s) - phenylene , electron transfer , crystallography , conjugated system , coupling (piping) , valence (chemistry) , bridging ligand , quantum interference , chemistry , electron , materials science , physics , quantum , quantum mechanics , polymer , crystal structure , organic chemistry , metallurgy
A series of three Mo 2 dimers bridged by a meta ‐phenylene group has been studied in terms of electronic coupling (EC) and electron transfer (ET) in comparison with the para isomers. Optical analyses on the mixed‐valence complexes indicate that by replacing a para ‐phenylene bridge with a meta one, the EC between the two Mo 2 centers is dramatically weakened; consequently, the ET rates ( k et ) are lowered by two to three orders of magnitude. In the para series, the EC parameters ( H ab ) and ET rates ( k et ) are greatly affected by O/S atomic alternation of the bridging ligand. However, for the meta analogues, similar EC and ET parameters are obtained, that is, H ab =300–400 cm −1 and k et ≈10 9 s −1 . These results suggest that through‐σ‐bond and/or through‐space coupling channels become operative as the π conjugation is disabled. DFT calculations reveal that destructive quantum interference features seen for the meta series arise from the cancellation of two π‐conjugated coupling pathways.