Electronic couplings in organic mixed-valence compounds: the contribution of photoelectron spectroscopy.
We show that the electronic coupling in strongly coupled organic mixed-valence systems can be effectively probed by means of gas-phase ultraviolet photoelectron spectroscopy (UPS). Taking six diamines as examples, the UPS estimates for the electronic couplings H(ab) are compared with the corresponding values determined from the intervalence charge-transfer absorption bands and from electronic structure calculations. Similar trends are observed for the H(ab) values estimated from UPS and optical spectra; this provides support for the applicability of Hush theory to strongly coupled organic mixed-valence systems. The UPS electronic couplings are found to be somewhat smaller than those from optical spectroscopy, which is attributed to the role of vibronic coupling to symmetrical modes; when corrected for this vibronic coupling, the UPS H(ab) estimates confirm that triarylamine-based mixed-valence systems are close to the class-II/class-III borderline.
School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA. veaceslav.coropceanu@chemistry.gatech.edu
Veaceslav
V
Coropceanu
Nadine E
NE
Gruhn
Stephen
S
Barlow
Christoph
C
Lambert
Jason C
JC
Durivage
Tonja G
TG
Bill
Gilbert
G
Nöll
Seth R
SR
Marder
Jean-Luc
JL
Brédas