TY - JOUR
T1 - Quantum chemical calculations of electronically excited states
T2 - Formamide, its protonated form and alkali cation complexes as case studies
AU - Antol, Ivana
AU - Barbatti, Mario
AU - Eckert-Maksić, Mirjana
AU - Lischka, Hans
N1 - Funding Information:
cited singlet state is also strongly pyramidalized at the carbon atom whereas the O-protonated form shows negligible N-pyramidalization in the excited state. Substantial energetic shifts of up to 3.4 eV have been observed due to geometry relaxation to the energy minimum for the protonated formamide. In comparison, for adducts of formamide with lithium and sodium cations much smaller changes were found. Calculated gas phase basicities show that the strong preference for protonation at the oxygen atom found for the ground state is strongly diminished in the excited state. The photodynamical simulations on formamide show that the main primary deactivation path is CN dissociation with a lifetime of about 420 fs. No indication of excited state proton transfer in the first excited state was found. Besides the presentation of an overview about the excited states of formamide and its derivatives, another more general goal of the current work was to show how high-level ab initio quantum chemical calculations based on multireference methods have become a powerful tool in the analysis of photoabsorption spectra, of photochemical and photophysical processes activated in the excited states, and of relaxation processes by which the system returns to the ground state either via photoemission or nonradiative pathways. Acknowledgements The authors acknowledge support by the WTZ treaty between Austria and Croatia (Project Nos. 9=2004=2006), the COST D37 action, and the Austrian Science fund within theframework of the Special Research Program F16 and project P18411-N19 (H.L. and M.B.). The work in Zagreb (I.A. and M.E.M.) has been supported by the Ministry of Science and Technology of Croatia through project 098-0982933-2920. The calculations were performed in part on the Schrödinger III Linux cluster of the Vienna University Computer Center. References 1. 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Hirst JD, Hirst DM, Brooks CL III (1996) J Phys Chem 100:13487 19. a) Lischka H, Shepard R, Pitzer RM, Shavitt I, Dallos M, Müller T, Szalay PG, Seth M, Kedziora GS, Yabushita S, Zhang ZY (2001) PCCP 3:664; b) Lischka H, Shepard R, Brown FB, Shavitt I (1981) Int J Quantum Chem S 15:91; c) Lischka H, Shepard R, Shavitt I, Pitzer RM, Dallos M, Mueller T, Szalay PG, Brown FB, Ahlrichs R, Boehm HJ, Chang A, Comeau DC, Gdanitz R, Dachsel H, Ehrhardt C, Ernzerhof M, Hoechtl P, Irle S, Kedziora G, Kovar T, Parasuk V, Pepper MJM, Scharf P, Schiffer H, Schindler M, Schueler M, Seth M, Stahlberg EA, Zhao J-G, Yabushita S, Zhang Z, Barbatti M, Matsika S, Schuurmann M, Yarkony DR, Brozell SR, Beck EV, Blaudeau J-P (2006) COLUMBUS, an ab initio electronic structure program, release 5.9.1: www.univie.ac.at/columbus 20. a) Shepard R, Lischka H, Szalay PG, Kovar T, Ernzerhof M (1992) J Chem Phys 96:2085; b) Lischka H, Dallos M, Shepard R (2002) Mol Phys 100:1647; c) Dallos M, Lischka H, Shepard R, Yarkony DR, Szalay PG (2004) J Chem Phys 120:7330; d) Lischka H, Dallos M, Szalay PG, Yarkony DR, Shepard R (2004) J Chem Phys 120:7322 Quantum chemical calculations for formamide 327
PY - 2008/4
Y1 - 2008/4
N2 - The properties of formamide, its protonated form and interaction complexes with lithium and sodium cations were studied in electronically excited singlet states by means of high-level multireference ab initio methods. The vertical excitation energies show a marked influence on protonation with particular large effects found for the O-protonated form as compared to neutral formamide. Complexation with Li+ and Na+ leads to a pronounced shift of the nO-π* state to higher energies while the π-π* state moves in opposite direction. Geometry optimizations in the lowest excited singlet show strong geometrical effects leading to pyramidalization at the N and C atoms. The photodynamical simulations performed for formamide in the first excited singlet state show that the main primary deactivation path is CN dissociation with a lifetime of about 420∈fs.
AB - The properties of formamide, its protonated form and interaction complexes with lithium and sodium cations were studied in electronically excited singlet states by means of high-level multireference ab initio methods. The vertical excitation energies show a marked influence on protonation with particular large effects found for the O-protonated form as compared to neutral formamide. Complexation with Li+ and Na+ leads to a pronounced shift of the nO-π* state to higher energies while the π-π* state moves in opposite direction. Geometry optimizations in the lowest excited singlet show strong geometrical effects leading to pyramidalization at the N and C atoms. The photodynamical simulations performed for formamide in the first excited singlet state show that the main primary deactivation path is CN dissociation with a lifetime of about 420∈fs.
KW - Absorption
KW - Basicity
KW - Metal ion affinities
KW - Multireference configuration interaction
KW - Photochemistry
UR - http://www.scopus.com/inward/record.url?scp=43349084633&partnerID=8YFLogxK
U2 - 10.1007/s00706-007-0803-2
DO - 10.1007/s00706-007-0803-2
M3 - Article
AN - SCOPUS:43349084633
SN - 0026-9247
VL - 139
SP - 319
EP - 328
JO - Monatshefte fur Chemie
JF - Monatshefte fur Chemie
IS - 4
ER -