TY - JOUR
T1 - Dynamic electron correlation effects on the ground state potential energy surface of a retinal chromophore model
AU - Gozem, Samer
AU - Huntress, Mark
AU - Schapiro, Igor
AU - Lindh, Roland
AU - Granovsky, Alexander A.
AU - Angeli, Celestino
AU - Olivucci, Massimo
PY - 2012/11/13
Y1 - 2012/11/13
N2 - The ground state potential energy surface of the retinal chromophore of visual pigments (e.g., bovine rhodopsin) features a low-lying conical intersection surrounded by regions with variable charge-transfer and diradical electronic structures. This implies that dynamic electron correlation may have a large effect on the shape of the force fields driving its reactivity. To investigate this effect, we focus on mapping the potential energy for three paths located along the ground state CASSCF potential energy surface of the penta-2,4-dieniminium cation taken as a minimal model of the retinal chromophore. The first path spans the bond length alternation coordinate and intercepts a conical intersection point. The other two are minimum energy paths along two distinct but kinetically competitive thermal isomerization coordinates. We show that the effect of introducing the missing dynamic electron correlation variationally (with MRCISD) and perturbatively (with the CASPT2, NEVPT2, and XMCQDPT2 methods) leads, invariably, to a stabilization of the regions with charge transfer character and to a significant reshaping of the reference CASSCF potential energy surface and suggesting a change in the dominating isomerization mechanism. The possible impact of such a correction on the photoisomerization of the retinal chromophore is discussed.
AB - The ground state potential energy surface of the retinal chromophore of visual pigments (e.g., bovine rhodopsin) features a low-lying conical intersection surrounded by regions with variable charge-transfer and diradical electronic structures. This implies that dynamic electron correlation may have a large effect on the shape of the force fields driving its reactivity. To investigate this effect, we focus on mapping the potential energy for three paths located along the ground state CASSCF potential energy surface of the penta-2,4-dieniminium cation taken as a minimal model of the retinal chromophore. The first path spans the bond length alternation coordinate and intercepts a conical intersection point. The other two are minimum energy paths along two distinct but kinetically competitive thermal isomerization coordinates. We show that the effect of introducing the missing dynamic electron correlation variationally (with MRCISD) and perturbatively (with the CASPT2, NEVPT2, and XMCQDPT2 methods) leads, invariably, to a stabilization of the regions with charge transfer character and to a significant reshaping of the reference CASSCF potential energy surface and suggesting a change in the dominating isomerization mechanism. The possible impact of such a correction on the photoisomerization of the retinal chromophore is discussed.
UR - http://www.scopus.com/inward/record.url?scp=84869024856&partnerID=8YFLogxK
U2 - 10.1021/ct3003139
DO - 10.1021/ct3003139
M3 - ???researchoutput.researchoutputtypes.contributiontojournal.article???
AN - SCOPUS:84869024856
SN - 1549-9618
VL - 8
SP - 4069
EP - 4080
JO - Journal of Chemical Theory and Computation
JF - Journal of Chemical Theory and Computation
IS - 11
ER -