@article {Mantela2016709,
	title = {Lowest ionisation and excitation energies of biologically important heterocyclic planar molecules},
	journal = {Molecular Physics},
	volume = {114},
	number = {5},
	year = {2016},
	note = {cited By 6},
	pages = {709-718},
	abstract = {We calculate the lowest ionisation and excitation energies in a variety of biologically important molecules, i.e. π-conjugated systems like DNA and RNA bases and isomers plus related heterocyclic molecules. For approximately half of these molecules, there are no experimental and theoretical/numerical data in the literature, as far as we know. These electronic transitions are mainly but not exclusively of π and π{\textendash}π* character, respectively. We perform symmetry-constrained density functional theory (DFT) geometry optimisation at the B3LYP/6-311++G** level of theory. At the DFT-obtained ground-state geometries, we calculate vertical ionisation energies with ionisation potential coupled cluster with singles and doubles (IP-EOMCCSD) and vertical excitation energies with the completely renormalised equation of motion coupled cluster with singles, doubles, and non-iterative triples (CR-EOMCCSD(T)) method. We also investigate whether a simple semi-empirical H{\"u}ckel-type model approach with novel parametrisation could provide reasonable estimates of the lowest π ionisation and π{\textendash}π* excitation energies. Our coupled cluster (CC) results are in very good agreement with experimental data, while the H{\"u}ckel-type model predictions generally follow the trends with some deviation. Finally, we investigate the effect of basis set in IP-EOMCCSD energies and we compare our CR-EOMCCSD(T) results with time-dependent DFT (TDDFT) ones.},
	doi = {10.1080/00268976.2015.1113313},
	url = {https://www.tandfonline.com/doi/full/10.1080/00268976.2015.1113313},
	author = {Mantela, M. and Morphis, A. and Tassi, M. and Simserides, C.}
}
