Code: ThP18	Time Slot/Poster Number: 149	Session: Theoretical Advances in PES Calculations
Hydration of L-tyrosine in Aqueous Solution. An FT-IR and Raman Spectroscopic and Theoretical Study
Ana Ledesma; Hernan Lanus; Silvia Antonia Brandan; Christian D. Contreras
Cátedra de Fisicoquímica I. Instituto de Química F, San Miguel De Tucumán, Argentina
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Summary
QM/MM calculations have been carried out in order to study the theoretical structures of L-tyrosine as well in gas phase as in aqueous solution. The molecule was characterized by infrared and Raman spectroscopies in solid phase and aqueous solution. Optimized geometries for different specie derived from L-tyrosine have been calculated taking into account the solvent effects by using the SCRF theory with the GAUSSIAN program.1 The theoretical structures in gas phase were simulated by using AMBER2 force field while in aqueous solution were performed with the PCM model3 and then, the results were analyzed and compared.

Code: ThP18	Time Slot/Poster Number: 150	Session: Theoretical Advances in PES Calculations
Fourier Transform Raman and Infrared Spectral Investigations of 2,6-dimethyl-2,5-heptadien-4-one
Mohan Sriramulu
HAWASSA UNIVERSITY, Hawassa, Ethiopia
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Summary
The present study is committed to the normal coordinate analysis of 2,6-dimethyl-2,5-heptadien-4-one. The main goal of our work is to interpret the FTIR and FTRaman spectra of 2,6-dimethyl-2,5-heptadien-4-one. Therefore a systematic study on the FTIR and FT-Raman spectra of 2,6-dimethyl-2,5-heptadien-4-one is attempted to study normal coordinate analysis to obtain a reasonable vibrational frequencies and assignments. The potential energy distribution (PED) is also calculated for each fundamental vibration

Code: ThP18	Time Slot/Poster Number: 151	Session: Theoretical Advances in PES Calculations
Fourier transform infrared and FT-Raman spectra, assignment, ab initio, DFT and normal co-ordinate analysis of 2-chloro-4-methylaniline and 2-chloro-6-methylaniline
Mohan Sriramulu
HAWASSA UNIVERSITY, Hawassa, Ethiopia
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Summary
The Fourier transform infrared (FTIR) and FT-Raman spectra of 2-chloro-4-methylaniline and 2-chloro-6-methylaniline have been measured in the range 4000–400 and 4000–100cm−1, respectively. Utilising the observed FTIR and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of the compounds were carried out. The vibrational frequency which were determined experimentally are compared with those obtained theoretically from ab initio HF and DFT gradient calculations employing the HF/6-31G(d,p) and B3LYP/6-31G(d,p) methods for optimised geometries. The geometries and normal modes of vibration obtained from the HF and DFT methods are in good agreement with the experimental data

Code: ThP18	Time Slot/Poster Number: 152	Session: Theoretical Advances in PES Calculations
Structural, vibrational and DFT studies on 2-chloro-1H-isoindole-1,3(2H)-dione and 2-methyl-1H-isoindole-1,3(2H)-dione
Mohan Sriramulu
HAWASSA UNIVERSITY, Hawassa, Ethiopia
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Summary
The Fourier transform infrared (FTIR) and FT-Raman spectra of 2-chloro-1H-isoindole-1,3(2H)-dione and 2-methyl-1H-isoindole-1,3(2H)-dione have been measured in the range of 4000–400 and 4000–100cm−1, respectively. Complete vibrational assignment and analysis of the fundamental modes of thecompounds were performed using the observed FTIR and FT-Raman data. The geometry was optimized without any symmetry constraints using the DFT/B3LYPmethod with 6–31G(d,p) and 6–311++G(d,p) basis sets. The structural parameters and normal modes of vibration obtained from DFT method are in good agreement with the experimental data. The force fields obtained from DFT method were utilised to calculate potential energy distributions.

Code: ThP18	Time Slot/Poster Number: 153	Session: Theoretical Advances in PES Calculations
Normal Mode Spectrum of Fe(PPIX)Cl in the Presence of External Force Fields
Alexander Demidov; Paul Champion
Northeastern University, Boston, MA
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Summary
In heme proteins, the chromophore is often distorted from the geometry that it would adopt in the absence of the protein environment. We simulated the effect of the protein distortion on a 5-coordinate heme, the Fe(PPIX)Cl with a QM/MM calculation. The correlation between the normal vibrational modes of the distorted structure and the undistorted structure was calculated using a quantitative technique. We observed significant mixing between the normal modes and the shifting of their frequencies in the region below 200 wavenumbers. Experimentally, this spectral region of heme proteins is studied in our group using femtosecond coherence spectroscopy.