formico-agua

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formico-agua

  1. 1. Theoretical Study of the Formic Acid-Water Complex in the First Excited State Jose M. Hermida-Ramón, Carlos M. Estévez. Departamento de Química Física. Facultade de Química. Universidade de Vigo. Spain
  2. 2. Introduction <ul><li>Purpose: study the hydrogen bond between formic acid and water in both ground and first excited singlet states. </li></ul><ul><li>Method: Geometry optimizations at CASSCF/6-311++G(2d,2p). Single point energy calculations at CASPT2. </li></ul><ul><li>Only single-water molecule complexes with trans- formic acid are considered. </li></ul>
  3. 3. Ground state FAT-1 S 0
  4. 4. FAT-2 S 0
  5. 5. FAT-3 S 0
  6. 6. Binding energies (S 0 ) (kJ mol -1 ) 17.0 22.0 43.2 B3LYP/ 6-311++G(2d,2p)(1) CASPT2//CAS(8,8)/ 6-311++G(2d,2p) 22.9 FAT-3 29.6 FAT-2 47.6 FAT-1
  7. 7. Vertical p * <- n excitation Positive electronic density difference between the first singlet excited state and the ground state Negative electronic density difference between the first singlet excited state and the ground state
  8. 8. Vertical excitation energies Calculated at the CASPT2//CAS(8,8)/6-311++G(2d,2p) level 5.67 eV FAT-3 5.81 eV FAT-2 5.76 eV FAT-1 5.78 eV (5.83 eV exptl)(2) HCOOH
  9. 9. Excited state optimized geometries Distances (angstrom) C=O = 1.402 C-O = 1.347 O-H = 0.941 C-H = 1.076 Angles (degree) O-C=O = 112.2 H-C=O = 112.1 H-O-C= 110.6 Dihedrals (degree) O=C-H-O = 129.0 H-O-C=O = 68.5
  10. 10. First singlet excited state Distances (angstrom) C=O = 1.407 C-O = 1.340 O-H = 0.947 C-H = 1.077 Angles (degree) O-C=O = 112.3 H-C=O = 111.6 H-O-C= 110.2 Dihedrals (degree) O=C-H-O = 129.0 H-O-C=O = 64.5 FAT-1 S 1
  11. 11. Distances (angstrom) C=O = 1.406 C-O = 1.348 O-H = 0.941 C-H = 1.075 Angles (degree) O-C=O = 112.0 H-C=O = 111.6 H-O-C= 110.6 Dihedrals (degree) O=C-H-O = 128.7 H-O-C=O = 69.8 FAT-2 S 1
  12. 12. Distances (angstrom) C=O = 1.400 C-O = 1.353 O-H = 0.942 C-H = 1.076 Angles (degree) O-C=O = 111.8 H-C=O = 112.6 H-O-C= 110.7 Dihedrals (degree) O=C-H-O = 128.8 H-O-C=O = 72.5 FAT-3 S 1
  13. 13. 0-0 Band Origin CASPT2//CAS(8,8)/6-311+G(2d,2p) 4.54 eV (4.64 eV exptl)(2) HCOOH 4.62 eV FAT-3 4.73 eV FAT-2 4.70 eV FAT-1
  14. 14. Binding energies (S 1 ) (kJ mol -1 ) CASPT2//CAS(8,8)/6-311++G(2d,2p) 15.2 FAT-3 10.5 FAT-2 31.9 FAT-1
  15. 15. Conclusions <ul><li>Only one water molecule does not appreciably blue shift the excitation. </li></ul><ul><li>Hydrogen bond is slighly weaker in the excited state. </li></ul>References <ul><li>Zhou, Z; Shi, Y; Zhou X. J. Phys. Chem A , 2004 , 108 , 813-822. </li></ul><ul><li>Ioannoni, F.; Moule, D. C.; Clouthier. D. J.; J. Phys. Chem., 1990 , 94 , 2290. </li></ul>

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