Supersymmetry of Hexabenzocoronene Torus

Hexabenzocoronene torus (HBCT) is a hypothetical torus-shaped network derived by properly connecting the nine pairs of peripheral carbon atoms of the hexabenzocoronene skeleton. The π-electronic structure of this hypothetical conjugated carbon network has an exceedingly high symmetry (supersymmetry) and is closely related to that of the graphite network. By using the group-theoretic technique developed by the authors it is shown that this 42 × 42 secular determinant of HBCT can be factorized into the product of 21 quadratic equations. A number of interesting mathematical properties of the supersymmetry of HBCT are introduced

Theoretical Studies for Molecular Modeling of New Camptothecin Analogues

Irinotecan (7-ethyl-10-[4-(1-piperidino)-1-piperidino carbonyloxycamptothecin: CPT-11) is a widely used potent antitumor drug that is developed based on camptothecin. However, overexpression of ABCG2 (BCRP/MXR/ABCP) confers cancer cells resistance to SN-38, that is, the active metabolite of irinotecan. In the present study to develop a platform for the molecular modeling to circumvent cancer drug resistance associated with ABCG2, we have characterized a total of fourteen new SN-38 analogues by some typical properties, which were evaluated by molecular orbital (MO) calculations and neural network (NN) QSAR technique

ELECTRONIC GROUND AND EXCITED STATES OF CoN: AN AB INITIO MOLECULAR ORBITAL STUDY

$^{a}$ K. Tanaka and M. Sekiya, Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0808, Japan. $^{b}$ M. Amano, S.S Itono, T. Hirano, U. Nagashima, M. Sekiya, and K. Tanaka, The 57th Ohio State University International Symposium on Molecular Spectroscopy, FB06, 255 (2002) $^{c}$ Q: Davidson's correction; $E_{rel}$: Relativistic correctionAuthor Institution: Grid Technology Research Center, Institute of Advanced Industrial Science and TechnologyBased on the information from Tanaka group of Hokkaido University,$^{a}$ we have studied the $^{1}\Sigma^{+}$ and $^{5}\Delta$ states of CoN by ab initio molecular orbital methods as an extension of our previous work on FeN.$^{b}$ The $MR-SDCI+Q+E_{rel}$/[Roos ANO(Co), aug-cc-pVQZ(N)] $calculations^{c}$ with full-valence plus Co $3_{s}$ and $3_{p}$ electron correlations predicted that the $^{5}\Delta$ level should be located by about $4300 cm^{-1}$ higher than the $^{1}\Sigma^{+}$ state. Hence, the electronic ground state is $^{1}\Sigma^{+}$. The equilibrium bond lengths for the $^{1}\Sigma^{+}$ and $^{5}\Delta$ states at this level of calculation are 1.5621 and $1.5945 {\AA}$, respectively. The first order relativistic correction $E_{rel}$ increases linearly with the Co-N bond length, with steeper gradient for $^{1}\Sigma^{+}$ than $^{5}\Delta$ states as is expected. The resultant shortening of the Co-N bond due to the relativistic effect is 0.016 and $0.005 {\AA}$ for the $^{1}\Sigma^{+}$ and $^{5}\Delta$ states, respectively

TOO SHORT CN BOND LENGTHS FOUND IN Fe, Co, AND Ni ISOCYANIDE AND CYANIDES

$^{a}$ J. Lie and P. J. Dagdigian, J. Chem. Phys. 114, 2137 (2001). $^{b}$ P.M. Sheridan and L.M. Ziurys, University of Arizona, Private communication (2003). $^{c}$ C.T. Kingston, AJ. Merer, and T.D. Varberg, J. Mole. Spectrosc, 215, 106 (2002). $^{d}$ P.M. Sheridan and L.M. Ziurys, J. Chem. Phys., 118, 6370 (2003).Author Institution: Grid Technology Research Center, Institute of Advanced Industrial Science and Technology 6-9-3 UenoWe were surprised, thinking it might be a misprint, with such a short C-N bond length, 1.03(8) {\AA}, of $\hat{X}^{6}\Delta$ FeNC when the Lie and Dagdigian paper (2001) on FeNC by $LIF^{a}$ came out. Ziurys and Sheridan aslo found a short CN bond length for the $\hat{X}$ CoCN, 1.13133 \AA, by MW, last $year.^{b}$ For $\hat{X}^{2}\Delta_{i}$ NiCN, Kingston and $Merer^{c}$ has reported a little short CN bond length of $1.1591(29) \AA$, determined by LIF, and Sheridan and $Ziurys^{d}$ $1.1580(8) \AA$ by MW. Our ab initio calculated $r_{e}$ values, though some of them are preliminary at the moment, are 1.172 (FeNC), 1.171 (CoCN), and 1.166 \AA (NiCN). The discrepancy between experimental and theoretical values is in the order $FeNC > CoCN > NiCN$, in parallel with the expected ionic character of the metal-ligand bond and accordingly with the floppy character of the bending motion. The observed too-short CN bond lengths in these radicals probably come from the inadequate model used for the analysis of observed spectra. A new model will be proposed, and calculations of the three dimensional potential energy surfaces for $\hat{X}^{6}\Delta$ FeNC/FeCN, which are necessary for the theoretical analysis based on the new model, are in progress at the level of $MR-SDCI+Q$ with Roos-ANO (Fe) and aug-cc-pVQZ (C and N) basis sets

SPECTROSCOPIC CONSTANTS OF Co-CONTAINING RADICALS PREDICTED BY HIGHLY ACCURATE AB INITIO QUANTUM CHEMICAL CALCULATIONS

{See for example: S.P. Beaton, K.M. Evenson, T. Nelis, and J.M. Brown, \textit{J. Chem. Phys{ P. M. Sheridan, M. A. Flory, and L. M. Ziurys, \textit{J. Chem. PhysAuthor Institution: Grid Technology Research Center, Institute of Advanced Industrial; Science and Technology, 6-9-3 Ueno, Taito-ku, Tokyo 110-0015, JapanWe have been investigating the method to predict spectroscopic constants of metal-containing radicals, such as MgNC, MgCN, FeNC, FeCN, FeC, FeN, and CoCO, \textit{etc}., accurately enough for molecular spectroscopy by highly-correlated \textit{ab initio} quantum chemical calculations. In this paper, we focus on the Co containing radicals, CoH and CoCN. The simplest Co containing molecule, CoH, has already been studied extensively.}., \textbf{89}, 4446-4448 (1988); R. S. Ram, P. F. Bernath, and S. P. Davis, \textit{J. Mol. Spectrosc.}, \textbf{173}, 158-176 (1995); D.P. Chong, S.R. Langhoff, C.W. Bauschlicher, Jr., S.P. Walch, and H. Partridge, \textit{J. Chem. Phys}., \textbf{85}, 2850-2860 (1986); M. Freindorf, C. M. Marian, and B. A. Hess, \textit{J. Chem. Phys}., \textbf{99}, 1215-1223 (1993).} However, not only experimentally but also theoretically obtained spectroscopic constants of CoH vary widely, and hence the spectroscopic constants of CoH have not conclusively been determined yet. After examining many methods carefully, we found that the size-consistent method and the separation of nearly-degenerate excited states are necessary to describe the electronic states of CoH. In addition, we found that the present available basis sets are not sufficient to describe such specific electronic states of CoH accurately. For CoCN, again a too short CN bond length, $r_{0}$(CN) = 1.1313(10) {\AA}, has been determined for the \tilde{X}\,^{3}\Phi_{\Omega = 4}.}., \textbf{121}, 8360-8368 (2004).} Our predicted $r_{e}$(CN) for the \tilde{X}\,^{3}\Phi_{i} at the MR-SDCI+Q+Relativistic-correction level is 1.171 {\AA}, which falls in the normal range of distance established for many CN-containing molecules

TOO SHORT CN BOND LENGTHS EXPERIMENTALLY FOUND IN COBALT CYANIDE: AN AB INITIO MOLECULAR ORBITAL STUDY

{ T. Hirano, R. Fukui, and U. Nagashima, \textit{59th Ohio State Univ. Internat. Sympo. Mol. Spectrosc.{P. M. Sheridan, M. A. Flory, and L. M. Ziurys, \textit{J. Chem. PhysAuthor Institution: Grid Technology Research Center, Institute of Advanced Industrial; Science and Technology, 6-9-3 Ueno, Taito-ku, Tokyo 110-0015, JapanIn the previous Ohio meeting, we pointed out that the CN bond lengths experimentally found for FeNC, CoCN, and NiCN are too-short.}, RF05 (2004).} The CN bond lengths in these radicals found by spectroscopy are shorter in this order than those predicted by high-level \textit{ab initio} molecular orbital calculations. The tendency is in parallel with the expected ionicity for the metal-N or metal-C bond, and hence is in parallel with the floppiness in bending motion. Recently submillimeter spectra of \tilde{X}\,^{3}\Phi_{i} has been published by Sheridan, Flory, and Ziurys, and the CN bond length $r_{0}$ derived for the \tilde{X}\,^{3}\Phi_{\Omega = 4} is reported to be 1.1313(10) {\AA}.}., \textbf{121}, 8360-8368 (2004).} Our $r_{e}$ value for the CN bond predicted at the level of the MR-SDCI+Q+Relativistic-correction/Roos ANO(Co, C, N) is 1.171 {\AA}, which is in the normal range observed and predicted for many CN-containing molecules. The difference in $r_{0}$ and $r_{e}$ shows how floppy CoCN is for the bending vibration mode

STRUCTURE AND SPECTROSCOPIC CONSTANTS OF FeCN: AN AB INITIO MOLECULAR ORBITAL STUDY

Author Institution: Department of Chemistry, Faculty of Science, Ochanomizu University; National Institute of Materials and Chemical Research, 1-1 HigashiFeCN is one of the possible candidates for an Fe-bearing interstellar molecule. Since no experimental data is available, prediction of its structure and spectroscopic constants by ab initio molecular orbital (MO) calculations has been requested. The ground state FeCl is known to be $^{6}\Delta$, and Cl and CN are known to show a similar chemical behavior. Hence, we assumed $^{6}\Delta$ state for the ground state FeCN. Wachters' all-electron basis set augmented with Bauschlicher's f-GTO, [8s.6p,4d,1f], for Fe and Dunning's cc-pVTZ basis sets for C and N have been employed. Active space for the MR-SDCI calculations has been selected to include Fe 3d and 4s as well as $CN \pi$ and $\pi^{\ast}$ orbitals obtained by the full valence MC-SCF MO calculations. Three dimentional potential energy surface has been calculated at the MR-SDCI level, and analyzed by the Mills' 2nd order perturbation theory. The $^{6}\Delta$ FeCN is predicted to be a linear molecule with Fe-C and CN bond lengths of 2.066 and 1.169 \AA, respectively, yielding $B_{e}, D_{J}$, and $B_{0}$ to be 3667.9, 0.0012, and 3676.1 MHz. Anharmonic vibrational frequencies $\nu_{1}, \nu_{2}$, and $\nu_{3}$ are predicted to be 2158, 185, and $450 cm^{-1}$, respectively

AN AB INITIO MOLECULAR ORBITAL STUDY OF ELECTRONIC EXCITED STATES OF FeC

$^{a}$W. J. Balfour, J. Cao, C. V. V. Prasad, and C. X. W. Qian J. Chem. Phys. 103, 4046, (1995) $^{b}$D. J. Brugh and M. D. Morse J. Chem. Phys. 107, 9772, (1997) $^{c}$K. Aiuchi, K. Tsuji, and K. Shibuya Chem. Phys. Lett. 309, 229, (1999)Author Institution: Ochanomizu University; Department of Chemistry, Faculty of Science, Ochanomizu University; Department of Chemistry, Faculty of Science, National Institute for Advanced Interdisciplinary ResearchThere has been a continuing effort to investigate the electronic states of iron carbide, FeC, by several research groups in the gas phase spectroscopy, but only electronic ground states have been established as $^{3}\Delta_{i}$ state arising from the configuration $\ldots 8\sigma^{2}3\pi^{4}1\delta^{3}9\sigma^{1}$. In this study, we have focused on characterizing the electronic excited states observed by $LIF^{a}$, $R2PI^{b}$ and $DF^{c}$ spectra. Spectroscopic constants and energy levels of the excited states have been calculated from the ab initio multireference singles and doubles configuration interaction (MR-SDCI) molecular orbital method using all-electron large basis sets. Both relativistic and spin-orbit coupling effects were taken into account. Many electronic states which are of complicated nature were found to populate densely in the low energy region. The lowest excited states for each spin and spatial symmetry, except the $^{1}\Delta$ state, were approximately described as the excited states derived by the promotion of one electron from the ground state. The excited states higher than these were found to be of completely multiconfigurational character. Each electronic state has been discussed in terms of electronic configuration, dipole moment, charge distribution, spin-orbit coupling constant, and spectroscopic constants