Modelling the non-radiative singlet excited state isomerization of diphenyl-acetylene: A vibronic coupling model

Abstract

Tolane (diphenyl-acetylene) is the smallest component of macromolecular arrays known as dendrimers that have interesting energy transport properties after photo-excitation. In this paper, a vibronic coupling Hamiltonian is set up to describe the initial internal conversion of this molecule. The calculated absorption spectrum is in good agreement with experiment, with the ordering of states and energies from MRCI-DFT calculation. The focus of the study is the pathway for photo-excited isomerisation from the linear geometry at the Frank-Condon point to a trans-structure. The model shows that the origin of the excited-state minimum for the trans-isomer is due to stabilisation of a high lying state. Quantum dynamics calculations using the MCTDH algorithm show the model agrees with experiment that isomerisation only occurs at high temperature. It also suggests that internal conversion to the S 1 global minima happens via second order coupling terms, which can explain the observed picosecond timescales.

Diabatic pseudofragmentation and nonadiabatic excitation-energy transfer in meta-substituted dendrimer building blocks

“…Along a similar line, let us mention that in-plane "zigzag" bending modes of CCCC chains may induce significant changes in the nature of the electronic states, as hinted for the p2 species in Ref. [31]. Such open questions will be addressed in future work, involving nonadiabatic quantum dynamics.…”

Excited-state dynamics of [Mn(im)(CO)3(phen)]+: PhotoCORM, catalyst, luminescent probe?

“…Recent simulations are mostly devoted to isomerization, fragmentation or charge transfer in organic chromophores. [28][29][30] Simulations of quantum dynamics including dissociative coordinates 31 are still scarce and only one example has been reported for a 1 st -row transition metal complex, namely the ultrafast photolysis of the heme-CO complex. 32 The present study is devoted to quantum dynamics simulations capable to follow the competition between fluorescence and carbonyl loss in [Mn(im)(CO)3(phen)] + , in particular the axial carbonyl, see Scheme 1.…”