Photoisomerization of Stilbene: The Detailed XMCQDPT2 Treatment

Abstract

We report the detailed XMCQDPT2/cc-pVTZ study of trans-cis photoisomerization in one of the core systems of both experimental and computational photochemistry-the stilbene molecule. For the first time, the potential energy surface (PES) of the S1 state has been directly optimized and scanned using a multistate multiconfiguration second-order perturbation theory. We characterize the trans-stilbene, pyramidalized (phantom), and DHP-cis-stilbene geometric domains of the S1 state and describe their stationary points including the transition states between them, as well as S1/S0 intersections. Also reported are the minima and the activation barriers in the ground state. Our calculations correctly predict the kinetic isotope effect due to H/D exchange at ethylenic hydrogens, the dynamic behavior of excited cis-stilbene, and trans-cis branching ratio after relaxation to S0 through a rather unsymmetric conical intersection. In general, the XMCQDPT2 results confirm the qualitative adequacy of the TDDFT (especially SF-TDDFT) picture of the excited stilbene but also reveal quantitative discrepancies that deserve further exploration.

Understanding the Driving Mechanisms of Enhanced Luminescence Emission of Oligo(styryl)benzenes and Tri(styryl)‐s‐triazine

“…In this sense, the torsional barrier around the vinylene moiety (dihedral angle α ) was calculated for all studied compounds in the S 1 excited state to deepen our understanding of its role in E / Z photoisomerization as a nonradiative deactivation process (see Figure ).Obtaining a complete description of the potential energy surface of the S 1 state of these compounds is out of the scope of the current study and could become extremely complex and prohibitively demanding (see ref. and references therein). Nevertheless, in the scanned region (from α =0 to 45°), it was found that the energy required for this rotation was significantly higher for compound 2 than that for 1 , according to the lower efficiency expected for E / Z photoisomerization of the tetrabranched molecule as a nonradiative deactivation mechanism.…”

Anticancer Activity of Stilbene‐Based Derivatives

“…Structurally, they are divided into Z ‐type and E ‐type based on the configuration of their central double bond; this can undergo Z / E isomerization, changing the overall configuration and decreasing the biological activity. In fact, photoisomerization is a problem that represents a common challenge in optimization work and most quantum chemistry calculation research has focused on its mechanisms but has not been concerned with optimizing these compounds to improve their stability and maintain their biological activity …”

“…Stilbenes are abundant in naturalp roducts [4] with av ariety of importantb iological activities. [5] Structurally,t hey are divided into Z-type and E-type based on the configuration of their central double bond;t his can undergo Z/E isomerization,c hanging the overall configuration and decreasing the biological activity.I nf act, photoisomerization is ap roblem that represents ac ommon challenge in optimization work and most quantum chemistry calculation research has focused on its mechanisms [6] but has not been concerned with optimizing these compounds to improvet heir stability and maintain their biological activity. [7][8][9] Stilbene containing compounds have drawn the attentiono f chemists and pharmacologistso vert he years mainly because of their important biological properties, such as antioxidant, hypolipidemic, antiviral, anti-inflammatory and anticancer.…”

Theoretical study on the torsional direction of simple ethylenoids after electronic relaxation at the conical intersection in the cis–trans photoisomerization

“…3,4 So we will check if the relationship found in fluorene-based ethylenoids is also true for simple ethylenoids such as ethylene, styrene and stilbene in Figure 1. The CIXs of these ethylenoids, which have been extensively studied, [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] are geometrically characterized by a non-symmetrical pyramidalized geometry; i) the C=C double bond is perpendicularly twisted, ii) the local geometry around the anionic C atom of the ethylenic bond is pyramidal and the other is planar, iii) the pyramidal structure is highly skewed against the ethylenic bond. By virtue of explicit definitions by internal coordinates, the CIXs are characterized by a geometry where the ethylenic double bond is perpendicularly twisted and in addition anionic portion of the ethylidenes is highly wagged and rocked against the ethylenic bond.…”