Potential energy surface intermolecular dynamics

An ultrafast intermolecular electron transfer (ET) from electron donating solvent to an excited dye molecule was found. A temperature-dependent non-exponential time dependence was observed in aniline, and a temperature-independent single exponential process for Nile blue (160 fs) and oxazine 1 (260 fs) was observed in N,N-Smethylaniline. The solvation times of solvent anilines were obtained by dynamic Stokes shift measurements. The rate of ET in some systems was observed to be much greater than the solvation time of anilines. The dynamic behavior was simulated by the 2-dimen ional potential energy surface for reaction, taking into account of the effects of both solvent reorientation and nuclear motion of reactants. 

Weakly bound complexes display unusual structural and dynamical properties resulting from the shape of their intermolecular potential energy surfaces. They show large amplitude internal motions, and do not conform to the dynamics and selection rules based on the harmonic oscillator/rigid rotor models (4). Consequently, conventional models used in the analysis of the spectroscopic data fail, and the knowledge of the full intermolecular potential and dipole/polarizability surfaces is essential to determine the assignments of the observed transitions. 

Future applications by the VPIMD method include vibrational fluctuations of molecular clusters such as hydrogen bonded clusters. Molecular clusters characterized by weak intermolecular interactions are expected to have large anharmonicity of the potential energy surfaces. As demonstrated in the present study, the VPIMD method properly handles the anharmonicity including the case of multiple minima. Another important point is on the description of the adiabatic potential energy surfaces of molecular clusters. An improvement can be achieved by combining the VPIMD method with electronic structure calculations as in the case of the finite temperature path integral molecular dynamics [30-32], These issues will be addressed in the near future. 

The dynamic linear combination of fragment confi ia-tions method. - Even-even intermolecular multicentric reactions. - The problem of correlation imposed barriers. -Reactivity trends of thermal cycloadditions. - Reactivity trends of singlet photochemical cycloadditions. - Miscellaneous intermolecular multicentric reactions. - tc + o addi-tion reactions. - Even-odd multicentric intermolecular reactions. - Potential energy surfaces for odd-odd multicentric intermolecular reactions. - Even-even intermolecular bicen-tric reactions. - Even-odd intermolecular bicentric reactions. 

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