PMID- 22782521
OWN - NLM
STAT- MEDLINE
DCOM- 20121116
LR  - 20131121
IS  - 1463-9084 (Electronic)
IS  - 1463-9076 (Linking)
VI  - 14
IP  - 31
DP  - 2012 Aug 21
TI  - Excitation energies of retinal chromophores: critical role of the structural 
      model.
PG  - 11015-20
LID - 10.1039/c2cp41387f [doi]
AB  - We employ a variety of highly-correlated approaches including quantum Monte Carlo 
      (QMC) and the n-electron valence state perturbation theory (NEVPT2) to compute 
      the vertical excitation energies of retinal protonated Schiff base (RPSB) models 
      in the gas phase. We find that the NEVPT2 excitation energies are in good 
      agreement with the QMC values and confirm our previous findings that the 
      complete-active-space perturbation (CASPT2) approach yields accurate excitations 
      for RPSB models only when the more recent zero-order IPEA Hamiltonian is 
      employed. The excitations computed with the original zero-order formulation of 
      CASPT2 are instead systematically red-shifted by more than 0.3 eV. We then focus 
      on the full 11-cis retinal chromophore and show that the M06-2X and MP2 
      approaches provide reliable ground-state equilibrium structures for this system 
      while the complete-active-space self-consistent field (CASSCF) geometry is 
      characterized by significantly higher ground-state energies at the NEVPT2 and 
      CASPT2 level. Our calibration of the structural model together with the general 
      agreement of all highly-correlated excited-state methods allows us to reliably 
      assign a value of about 2.3 eV to the vertical excitation of 11-cis RPSB in the 
      gas-phase.
FAU - Valsson, Omar
AU  - Valsson O
AD  - MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE 
      Enschede, The Netherlands.
FAU - Angeli, Celestino
AU  - Angeli C
FAU - Filippi, Claudia
AU  - Filippi C
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20120711
PL  - England
TA  - Phys Chem Chem Phys
JT  - Physical chemistry chemical physics : PCCP
JID - 100888160
RN  - 0 (Gases)
RN  - 0 (Schiff Bases)
RN  - RR725D715M (Retinaldehyde)
SB  - IM
MH  - Gases/chemistry
MH  - *Models, Chemical
MH  - Monte Carlo Method
MH  - Retinaldehyde/*chemistry
MH  - Schiff Bases/chemistry
EDAT- 2012/07/12 06:00
MHDA- 2012/12/10 06:00
CRDT- 2012/07/12 06:00
PHST- 2012/07/12 06:00 [entrez]
PHST- 2012/07/12 06:00 [pubmed]
PHST- 2012/12/10 06:00 [medline]
AID - 10.1039/c2cp41387f [doi]
PST - ppublish
SO  - Phys Chem Chem Phys. 2012 Aug 21;14(31):11015-20. doi: 10.1039/c2cp41387f. Epub 
      2012 Jul 11.