Photochemistry TDDFT

A recent re-investigation of the electronic structure of MeReCU by both DFT/TDDFT and more highly correlated methods leads to the conclusion that the second transition (ca. 240 nm) has both methyl carbon and oxo character (by DFT/TDDFT). Use of CASSCF/MS-CASPT2 calculations shows more oxo and less C contribution, demonstrating that the level of theory is important in interpreting the photochemistry [10]. 

For space limitation, other recent extensions of the PCM-TDDFT scheme aimed at describing other interesting photophysics phenomena of solvated molecules have not been considered. We cite here, as examples, the application of PCM-TDDFT to the study of the Excitation Energy Transfer (EET) between chromophores in different environments [48], and of absorption/emission spectra of chromophores in complex environments such as the interphase between two different media [49], All these new QM computational tools may be of support to the efforts toward an even better understanding and description of the photophysics and of the photochemistry of molecules in condensed phase and in complex environments. 

Another area where one needs to be careful is photochemistry. If the excited-state potential energy curves between two open-shell fragments are studied with TDDFT, artifacts may occur at bond lengths beyond the equilibrium geometry. The simplest example is where the... 

Whenever a method is shown to work well, it inevitably gets applied to many scientific investigations, and specific failures then appear. Charge-transfer excitations are of great importance in photochemistry, especially of biological systems, but many workers are now finding abysmal results with TDDFT for... 

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