Calculation of Molecular Properties: How, What and Why?Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaDr. Vasile ChiBiomedical Physics Department, Faculty of Physics Babe-Bolyai University, Cluj-Napoca"Many experimental chemists use various kinds of spectroscopy in their research even though they are not spectroscopists. In a similar manner, more and more scientists are applying computational techniques as another weapon in their arsenal"Delano P. Chong in Recent Advances in Density Functional Methods, Part I, World Scientific, 1995

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaOutline1. Introduction2. Hartree-Fock-Roothaan-Hall Theory3. Basis Sets4. Electron Correlation 5. ABC of DFT6. Predictible Molecular Properties7. Examples of Calculationsvibrational, NMR and ESR spectraconformers, tautomers, relative energies, molecular orbitals

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaAb Initio Electronic Structure TheoryHartree-FockDFTMolecular StructuresMolecular PropertiesSpectroscopic ObservablesBenchmarks for parametrizationsTransition StatesReaction CoordinatesProdding and Helping the ExperimentalistsCalculation of Molecular Properties: Why?

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaWe are perhaps not far removed from the time when we shall be able to submit the bulk of chemical phenomena to calculationJoseph Louis Gay-Lussac, Memoires de la Societe dArcueil, 2,207(1808)

The more progress physical science make, the more they enter the domain of mathematics, which is a kind of centre to which they all converge. We may even judge the degree of perfection to which a science has arrived by the facility with which it may be submitted to calculation.Adolphe Quetelet, Instructions Populaires sur le Calcul des Probabilities, Tarlier, Brussels, 1828, p. 230Every attempt to employ mathematical methods in the study of chemical questions must be considered profoundly irrational and contrary to the spirit of chemistry. If mathematical analysis should ever hold a proeminent place in chemistry an aberration which is almost impossible it would occasion a rapid widespread degeneration of that scienceA. Compte, Philosophie Positive, 1830A short historyJ.L. Gay-LussacA. QueteletA. Compte

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaQuantum Wave Mechanics, 1926H=EThe underlying physical laws necessary for the mathematical theory of a large part of physics and the whole of chemistry are thus completely known, and the difficulty is only that the exact application of these laws leads to equations much too complicated to be soluble.P.A.M. Dirac, Proc. Roy. Soc(London) 123, 714(1929)E.R.J.A. SchrdingerW.K. HeisenbergP.A.M. Dirac

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-Napoca

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaHartree-Fock-Roothaan TheoryM. BornR. Oppenheimer

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaD. Hartree

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaD. HartreeV. Fock

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaD. HartreeV. FockC. Roothaan

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaBasis Sets=LCBF {} a set of known functionsSlater Type Orbitals (STO)Gaussian Type Orbitals (GTO)

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaGTOallow a more rapidly and efficiently calculation of the two-electron integralshave different functional behavior with respect to known functional behavior of AOs.S. F. Boys, Proc. Roy. Soc. (London) A200 (1950) 542.

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaStandard basis: 6-31G (6D, 7F) Basis set in the form of general basis input: 1 0 S 6 1.00 .3047524880D+04 .1834737130D-02 .4573695180D+03 .1403732280D-01 .1039486850D+03 .6884262220D-01 .2921015530D+02 .2321844430D+00 .9286662960D+01 .4679413480D+00 .3163926960D+01 .3623119850D+00 SP 3 1.00 .7868272350D+01 -.1193324200D+00 .6899906660D-01 .1881288540D+01 -.1608541520D+00 .3164239610D+00 .5442492580D+00 .1143456440D+01 .7443082910D+00 SP 1 1.00 .1687144782D+00 .1000000000D+01 .1000000000D+01 **** 2 0 S 3 1.00 .1873113696D+02 .3349460434D-01 .2825394365D+01 .2347269535D+00 .6401216923D+00 .8137573262D+00 S 1 1.00 .1612777588D+00 .1000000000D+01 **** ...6-31G Basis set for CH4 moleculeHF limit: mono-determinantal wave-function + infinite basis setSTO-3G3-21G6-31G(d)6-311++G(2df,p)

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-Napoca

Electron CorrelationDr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaHF method: electron-electron interaction is replaced by an average interactionE0 exact ground state energyEHF HF energy for a given basis set- represents a measure for the error introduced by the HF approximation

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaTypes of electronic correlationExchange EnergySpin correlation- effect of the Pauli exclusion principle(Fermi correlation) (Fermi hole)Dynamical correlation related to the movements of the individual electrons (Coulomb correlation) (Coulomb hole)Non-dynamical correlation- related to the fact that in certain circumstances the ground state SD wave-function is not a good approximation to the true ground state because there are other Slater determinants with comparable energies (near degeneracy problem)Correlation Energy

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaCorrelation Energy: Is it important?N2 molecule:CE ~ 0.5% of the EE ~ 50% of the binding energy!

Chart1

100

1

Sheet1

1

2

TEE1001

CE1

100

Total electronic energy100

Correlation energy1

99

Sheet1

0

0

Sheet2

Sheet3

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-Napocamultideterminantal wave-functionESD obtained by replacing MOs which are occupied in the HF determinant by unoccupied MOs- singly, doubly, triply, quadruply, etc. excited relative to the HF determinantHow to take it into account?

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaElectron correlated methods:Configuration Interaction (CIS, CID, CISD, CISDT, etc.)Multi-Configuration Self-Consistent Field Method (MCSCF) n,m-CASSCFMoller-Pleset Theory MP2, MP4, etc.Coupled Cluster Theory CCD, CCSD, etc.

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaABC of DFTWhy a new theory?HF method scales asK4 (K - # of basis functions)CI methods scale asK6-K10MPn methods scale as>K5CC methods scale as >K6Correlated methods are not feasible for medium and large sized molecules!The electron density1927L.H. Thomas, E. Fermi1964P. Hohenberg, W. Kohn, L.J. Sham1992Gaussian

DFT is presently the most successful and also the most promising approach to compute the electronic structure of matter.Applicability: atoms, molecules, solidsDFT is less computationally expensive than traditional Hartree-Fock methods but it gives similar accuracy.

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-Napoca

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaFirst HK Theorem:P. HohenbergW. Kohn

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaThe explicit form of T[] and Enon-cl[] is the major challenge of DFTFHK ???Modern DFTOnly J[] is known!

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaT[] kinetic energy of a real interacting electron system with density (r)TKS kinetic energy of a fictitious non-interacting system of the same density (r)i - are the orbitals for the non-interacting system (KS orbitals)T=TKS+(T-TKS)Exc[] includes everything which is unknown:exchange energycorrelation energycorrection of kinetic energy (T-TKS)

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaVariational Principle in DFTMinimize E[] with the conditions: Kohn-Sham Equations:with:Second HK TheoremW. KohnL.J. Sham

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaKohn-Sham FormalismHartree-Fock equationsKohn-Sham equationsW. KohnL.J. Sham

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaExc[] = ??Local Density Approximation (LDA)xc only depends on the density at rGeneralized Gradient Approximation (GGA)xc depends on the density and its gradient at rHybrid Functionals

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaDFT: a new and powerful tool in chemical physics

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaPredictible Molecular Properties

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaExamples of Calculations

pyrazinamide

meta-benzosemiquinone anion free radical

5-pBBTT

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-Napoca analogue of nicotinamide very important drug used to treat tuberculosis some transition metal(II) molecular complexes of this molecule are recognized and used as antimycobacterial agents

Pyrazinamide (PZA)

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaOptimized geometries (B3LYP/6-31G(d)) of the two conformers of PZAC1C2Possible contributions from both conformers (in gas or liquid phase)

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaHB moderate strength - predominant electrostatic characterInteraction energy:Euncorrected = 16.14 Kcal/molECP corrected = 13.82 Kcal/molBasis set superposition errorG.A. Jeffrey, An Introduction to Hydrogen Bonding, Oxford University Press, New York, 1997Optimized geometry (B3LYP/6-31G(d)) of the PZA dimer

Sheet1

ExperimentalCalculated (B3LYP/6-31G(d))

C1C2Dimer

Dihedral angles

H13N8C7C220.5025.60

H14N8C7C2177.1180173.5180

Hydrogen bond parameters

N8...O9'2.905--2.895

H14...O9'2.034--1.871

N8H14...O9'178.4--174.3

Sheet2

Sheet3

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaSelected experimental and calculated vibrational bands of PZA NH2 important role in the conformation of peptides or Watson-Crick complexes- intermediates the hydrogen bonds (intra and inter)

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaExperimental and calculated NMR spectrum of PZAHB

Sheet1

NucleusMonomer C1DimerMonomer C2

C2138.3138.9143.8

C3140.7140.5137.3

C5140.8140.8139.2

C6135.4135.6139.4

C7151.6155.6154.7

H109.49.48.7

H118.68.68.5

H128.38.38.6

H136.76.94.3

H144.08.94.1

Sheet2

Sheet3

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-Napoca [1H, 1H] COSY45 NMR spectrum of pyrazinamide in DMSO solution

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaFor a reliable assignment of experimental spectra- intermolecular interactions must be considered!

- minimal computational strategy: vibrational spectraDFT (B3LYP + BLYP) monomer + dimer calculations 6-31G(d) basis setNMR spectraDFT (B3LYP)dimer calculationscc-pVDZ basis set

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaQuinones (and related radicals) are involved in many biophysical processes: cellular respiration (ubiquinone = coenzyme Q10)- also, an essential nutrient blood clotting (menaquinones = vitamin K2) aging (tocoquinones = vitamin E2) microbial controlling agentsquinone-type radicals important cofactors for electron transfer in photosynthesis ESR spectra of ortho-, meta- and para-benzosemiquinone radicalsvery accessible to experimental and theoretical analyses

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaBSQ anion radicals: energetics, structures and symmetries7.38Kcal/mol7.15Kcal/molB3LYP/6-31+G(d)Cs symmetry

Chart1

-381.5382474-381.582884

-381.5269907-381.5703652

-381.5500087-381.5936425

6-31+G(d)

EPR-II

Total energies (a.u.)

Sheet1

orthometapara

6-31+G(d)-381.5382474-381.5269907-381.5500087

EPR-II-381.582884-381.5703652-381.5936425

HOMO

LUMO

Sheet1

00

00

00

6-31+G(d)

EPR-II

Sheet2

Sheet3

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaBSQ anion radicals: HOMO and LUMOs energiesB3LYP/6-31+G(d)Cs symmetry

Chart2

-0.3885-1.453-0.271

1.5550.5411.745

1.9441.9942.016

ortho

meta

para

Frontier orbitals energy (eV)

Sheet1

orthometapara

6-31+G(d)-381.5382474-381.5269907-381.5500087

EPR-II-381.582884-381.5703652-381.5936425

orthometapara

HOMO-0.3885-1.453-0.271

LUMO1.5550.5411.745

E1.9441.9942.016

orthometapara

HOMO-0.01428-0.05338-0.00997

LUMO0.057150.019890.06411

E0.071430.073270.07408

Sheet1

00

00

00

6-31+G(d)

EPR-II

Sheet2

000

000

000

ortho

meta

para

Sheet3

000

000

000

ortho

meta

para

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaorthoHOMOLUMOmetaparaUSD DistributionBSQ anion radicals: HOMOs, LUMOs, USDs

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-Napocameta-BSQ optimized structuresB3LYP/EPR-II

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-Napoca* absolute valuesCalculated hyperfine coupling constants of the meta-BSQ anion radical in gas-phase, for the three minimum structures

UB3LYP/EPR-IIGas-phaseA2A4,6A5Experimental*(water)0.6811.442.43Cs(2A)0.27-11.762.85C2v(2A2)0.27-11.762.85C2v(2B1)-16.320.32-0.72

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaGas-phase meta-benzosemiquinone anion radical B3LYP/EPR-II (grid ultrafine) 0.27 -11.76 2.87Marked non uniformity of the electron density in C1C2C3 region+-+

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaExperimental and calculated wave-numbers for m-BSQ anion radical*B3LYP/6-31+G(d) Cs symmetryCO stretchCH bendG.N.R.Tripathi, D.M.Chipman, C.A.Miderski, H.F.Davis, R.W.Fessenden, R.H. Schuler, J.Phys.Chem., 90,3968(1986)present work

calculated*5279621090/1048!1133/10891237/11891332/12811473/14161497/14391573/1512!1596/1534

Sheet1

IR Frequencies

Cs 2A"C2v 2A2C2v 2B1

ModSym.UnscaledScaledUHF/3-21Gscalate cu 0.89simModSym.UnscaledScaledUHF/3-21Gscalate cu 0.89simModSym.UnscaledScaled

1A"170163228203A"1B1170163210187A21B1177170

2A"178171248221A"2A2178171225200B12?A186179

3?A381366362322A'3A1381366404360A13?A187180

4?A397382484431A"4B1397382455405B14A1361347

5A"438421537478A'5B2438421547487B25B1426410

6A'517497551490A'6B2517497578514A16A1519499

7A'528508557496A'7A1528508654582B27B2526506

8A"600577707629A"8B1600577693617B18A2571549

9A"650625734653A"9A2649624748666A19B1634610

10A"729701758675A'10A1729701749667A210B1733705

11A"741712851757A"11B1740711844751B111A1760731

12A"804773956851A"12B1803772940837A212A2768738

13A"843810958853A'13A2843810951846B213B1837805

14A'9218851011900A"14B2921885979871B114B2939903

15A"9268901019907A'15B19268901044929A115A1957920

16A'9609231079960A"16A19619241064947B116B1959922

17A'109210501100979A'17A11092105011381013A117A110701029

18A'1136109211421016A'18B21136109212311096B218B211511107

19A'1247119912431106A'19B21247119913821230B219B212311183

20A'1330127912801139A'20A11330127913821230A120B212991249

21A'1331128013881235A'21B21330127914351277B221B213361284

22A'1339128714391281A'22B21339128715601388B222A113391287

23A'1467141015181351A'23B21467141015651393A123A114271372

24A'1492143415801406A'24A11492143416441463B224B214981440

25A'1554149415911416A'25A11555149517211532A125B215441484

26A'1556149617231533A'26B21556149620911861B226A115941532

27A'3128300732992936A'27A13127300633032940A127A131122992

28A'3178305533422974A'28B23178305533522983B228B231783055

29A'3182305933622992A'29A13182305933602990A129A131843061

30A'3186306333662996A'30A13185306233743003A130A131923069

Sheet2

n(cm-1)IntensityAssignment

533mediumCCC bend

970very weakCCC bend

1070weakCH bend

1093strongCO stretch

1227weakCH bend

1314weakCC stretch

1389weakCC stretch

1462weakCC stretch

1519strongCO stretch

1570very weakCC stretch

Sheet3

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-Napoca dipole moments: (ortho)> (meta)>(para)=0 number of minimum energy conformers: 2 for ortho and para, 3 for meta total energies: Emeta>Eortho>Epara hfccs:ortho - strong influence of the solvation effectsmeta - marked non-uniformity in the electron densitypara easilly reproduced even in gas-phase vibrational spectra: ortho no experimental data availablemeta reassignment of two bands in the IR spectrumpara very good agreement between experiment and theoryConclusions

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaMolecular structure and atom numbering scheme for 5-para-bromo-benzilidene- thiazolidine-2-thion-4-one molecule Vibrational, NMR and DFT investigation of 5-pBBTT

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-Napoca5-pBBTT Conformers and TautomersC1C2C1 ThiolC1 Thiol 1C2 ThiolC2 Thiol 1

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaUnit cell parameters

a = 4.4597(7) b = 12.5508(19) c = 13.727(2) = 90.751(2) = 96.230(2) = 97.865(3)

Crystal System:Triclinic Space group:P-1 X-ray diffraction

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-Napoca1H NMR Spectrum of 5-pBBTT in DMSOLooking for a proton

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaDifferent tautomers in liquid state?Experimental: 3.4ppm and 13.9 ppm Thiolic ConformerThione ConformerThiol: 66%Thione: 33%Calculated chemical shift for N-H and S-H protons in thione and thiol tautomers

ThioneThiolThioneH-bondedThioneH-bonded6-31G(d)6-31G(d)6-31G(d)6-31+G(d,p)7.133.5011.7414.14

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaSCRF-PCM continuum solvation model

SolventThioneThiolEnol5pBr-BTTVacuo0.002.6314.962.4115.805.39Water-17.612.8118.293.256.499.07DMSO-4.273.363.133.5411.637.815pF-BTTVacuo0.002.5615.072.6915.805.78Water-12.735.229.923.94-0.7910.51DMSO-3.724.093.374.0111.308.37

Chart1

014.9615.8

-17.6118.296.49

-4.273.1311.63

thione

thiol

enol

m1 corrected

Sheet1

6-31G(d)

m1

NHSHOHNH in waterSH in waterOH in waterNH in DMSOSH in DMSOOH in DMSO

Energy-3882.7498433-3882.7221499-3882.724143-3882.7707372-3882.7288055-3882.7390193-3882.75675762-3882.7413925-3882.7309069

ZPVE correction0.1392430.135320.1387040.131930.1475090.1387480.1393490.1357120.138828

ZPVE scaled0.13654168580.1326947920.13601314240.1293705580.14464732540.13605628880.13664562940.13307918720.1361347368

ZPVE corrected energy-3882.6133016142-3882.589455108-3882.5881298576-3882.641366642-3882.5841581746-3882.6029630112-3882.6201119906-3882.6083133128-3882.5947721632

14.9615.80-17.6118.296.49-4.273.1311.63

uncorrected17.3816.13-13.1113.206.79-4.345.3011.88

HOMO-0.23421-0.23294-0.22418-0.22902-0.23139-0.2263-0.23089-0.22958-0.22574

LUMO-0.10379-0.09635-0.11252-0.09982-0.09696-0.11052-0.10109-0.09563-0.11133

dE(HOMO-LUMO)3.553.723.044.333.663.153.533.653.11

Dipole moment2.632.415.392.813.259.073.363.547.81

m2

NHSHOHNH in waterSH in waterOH in waterNH in DMSOSH in DMSOOH in DMSO

Energy-1410.8790953-1410.8512927-1410.8534105-1410.89943456-1410.8591253-1410.8799268-1410.885126-1410.870381-1410.8603188

ZPVE correction0.1410980.1372380.1405760.1411590.1368590.1406620.1412060.1376960.140316

ZPVE scaled0.13836069880.13457558280.13784882560.13842051540.13420393540.13793315720.13846660360.13502469760.1375938696

ZPVE corrected energy-1410.7407346012-1410.7167171172-1410.7155616744-1410.7610140446-1410.7249213646-1410.7419936428-1410.7466593964-1410.7353563024-1410.7227249304

15.0715.80-12.739.92-0.79-3.723.3711.30

uncorrected17.4516.12-12.7612.53-0.52-3.785.4711.78

HOMO-0.23226-0.23089-0.22174-0.2321-0.23035-0.22492-0.22989-0.23109-0.22398

LUMO-0.0996-0.09184-0.10861-0.10019-0.09466-0.10768-0.09829-0.09469-0.10832

dE(HOMO-LUMO)3.613.783.083.593.693.193.583.693.15

Dipole moment2.562.695.785.223.9410.514.094.018.37

m1 uncorrected

NHSHOH

gas-phase017.3816.13

water-13.1113.206.79

DMSO-4.345.3011.88

m2 uncorrected

NHSHOH

gas-phase017.4516.12

water-12.7612.53-0.52

DMSO-3.785.4711.78

m1 correctedgas-phasewaterDMSO

thione0.00-17.61-4.27

thiol14.9618.293.13

enol15.806.4911.63

m2 correctedgas-phasewaterDMSO

thione0-12.73-3.72

thiol15.079.923.37

enol15.80-0.7911.30

Sheet1

gas-phase

water

DMSO

m1 uncorrected

Sheet2

thione

thiol

enol

m1 corrected

Sheet3

thione

thiol

enol

m2 corrected

6-31+G(d,p)

m1

NHSHOH

Energy-3882.806004-3882.7788948-3882.783145

ZPVE correction0.1395020.1356150.139126

ZPVE scaled0.13679566120.1329840690.1364269556

ZPVE corrected energy-3882.6692083388-3882.645910731-3882.6467180444

14.6214.11

uncorrected17.0114.34

HOMO-0.24287-0.24266-0.23322

LUMO-0.11503-0.10872-0.12283

dE(HOMO-LUMO)3.483.643.00

Dipole moment2.452.885.17

m2

NHSHOH

Energy-1410.9194898-1410.8923445-1410.896613

ZPVE correction0.1404520.1366210.140098

ZPVE scaled0.13772723120.13397055260.1373800988

ZPVE corrected energy-1410.7817625688-1410.7583739474-1410.7592329012

14.6814.14

uncorrected17.0314.36

HOMO-0.24282-0.24282-0.23202

LUMO-0.11231-0.10577-0.12036

dE(HOMO-LUMO)3.553.733.04

Dipole moment2.562.905.31

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaProposed molecular structure is confirmed by experimental and theoretical results.

The most stable conformer was proposed based on theoretical results and was confirmed by vibrational, NMR and X-ray diffraction results.

Based on NMR and theoretical data, the coexistence of thiolic and thione tautomers is proved in liquid state. Moreover, thiolic conformer is prevailing in this case and thione conformer still remains H-bonded in liquid phase.Conclusions:

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaFrom the beginning: Calculation of Molecular PropertiesWhy?How?What?HF, UHF, MPn, CI, CC, DFT, AM1, PM3, etc.6-31G(d), cc-pVDZ, Lanl2DZ(ECP), etc.well almost everything!can we live without? (designing new materials, pharmaceuticals, etc)

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaPublications: closed-shell systemsMolecular and Vibrational Structure of 2,4-Dinitrophenol: FT-IR, FT-Raman and Quantum Chemical CalculationsV.Chi Chem.Phys., 300, 1-11 (2004)

Vibrational Spectroscopy and Theoretical Studies on 2,4-dinitrophenylhydrazineV.Chi, V.Miclu, A.Prnu, C.Tnselia, V.Alman, M.VasilescuJ.Mol.Struct., 744-747 363-368 (2005)

NIR Surface Enhanced Raman Spectroscopy and Band Assignment by DFT Calculations of Non-Natural -amino acidsT. Iliescu, D. Maniu, V. Chi, F.D. Irimie, Cs. Paizs and M. Tosa Chem.Phys., 310, 189-199 (2005)

Adsorption of 6-Mercaptopurine and 6-Mercaptopurine-Riboside on Silver Colloid: A pH Dependent Surface Enhanced Raman Spectroscopy and Density Functional Theory Study. Part I. 6-MercaptopurineA. V. Szeghalmi, L. Leopold, S. Pnzaru, V. Chi, I. Silaghi-Dumitrescu, M. Schmitt, J. Popp, W. KieferJ.Mol.Struct., 735-736, 103-113 (2005)

Adsorption of 6-mercaptopurine and 6-mercaptopurine-riboside on silver colloid: A pH dependent surface enhancedRaman spectroscopy and density functional theory study. Part II. 6-mercaptopurine-ribosideV. Szeghalmi, L. Leopold, S. Pnzaru, V. Chi, I. Silaghi-Dumitrescu, M. Schmitt, J. Popp, W. KieferBiopolymers, 78, 298-310 (2005)

Experimental and DFT Study of PyrazinamideV. Chi, A. Prnu, T. Jurc, M. Vasilescu, S. Simon, O. Cozar, L. DavidChem. Phys., 316, 153-163 (2005)

Molecular and Vibrational Structure of 5-Para-Bromo-BenzilidenTiazolidin-2-Tion-4-Ona. Experimental and Theoretical InvestigationA.Prnu, M. Baias, O.Oniga, V.Chi, M.Vasilescu, O.CozarStudia Physica, Special Issue, NANOSPEC, 2005

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaPublications: open-shell systems (free radicals)Ab Initio and DFT calculations of the hyperfine structure of OH, HO2 and H2O+ radicalsV.Chi, L.David, O.Cozar, A.Chi Rom.J.Phys., 48, 413-428 (2003)

Ab Initio and DFT Study on Hyperfine Structure of 1,2-Benzosemiquinone Anion RadicalV.Chi, A.Neme, L.David, O.CozarStudia UBB, Physica, 47(1) 157-170 (2002)

AM1/INDO Semiempirical Calculations on Tyrosyl RadicalV.ChiStudia UBB, Physica, 47(1), 147-156 (2002)

Which radicals are formed by electrochemical reduction of Dihydrazid-Hydrazone? An ESR and DFT Investigation.V.Chi, V.Miclu, L.Murean, G.Damian, L.David, O.CozarStudia UBB, Physica, XLXIII, Special Issue, 123-134 (2003)

Theoretical ESR Spectrum of 1,3-Benzosemiquinone RadicalV.Chi, R.Marcu, M.Oltean, L.David, O.CozarAnalele Universitii din Oradea, A XIII, 123-142 (2003)

Density Functional Calculations of Hyperfine Coupling Constants in Glycine-Derived RadicalsRaluca Marcu, Vasile ChiStudia Physica, Special Issue, NANOSPEC, 2005

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaPublications: wave-functions for small moleculesThe effect of target representation in positron-impact ionization of molecular hydrogen R. I. Campeanu, V. Chi, L. Nagy and A. D. StaufferPhys.Lett. A, 310(5-6),445 - 450(2003)

Positron impact ionization of molecular nitrogenR.I. Campeanu, V.Chi, L. Nagy, A. D. StaufferNucl. Instrum. Meth. B 221 (2004) 21-23

Positron impact ionization of molecular oxygenR.I. Campeanu, V. Chi, L. Nagy, A. D. Stauffer Phys. Lett. A 325 (1) 66-69 (2004)

Positron impact ionization of CO and CO2R.I. Campeanu, V. Chi, L. Nagy, A.D. StaufferPhys.Lett. A, 344 (2-4): 247-252 (2005)

Dr. Vasile Chi , Faculty of Physics, Babe-Bolyai University, Cluj-NapocaProf. L. Nagy, Prof. T. Iliescu, Prof. S. Astileandr. N. Leopold, dr. D. Maniu, dr. S. Cinta Pinzaru, dr. C. Craciun, dr. M. VasilescuBabes-Bolyai University, Faculty of PhysicsAcknowledgmentsdr. V. Miclaus, dr. M. Venter Babes-Bolyai University, Faculty of Chemistrydr. T. Jurca University of Oradea, Faculty of Medicine and PharmacyProf. O.OnigaUMF Cluj-Napoca, Dept. of Pharmaceutical ChemistryA. Pirnau, R. Marcu, M. Baias, M. Oltean, C. Tanaselia, L. Szabo, S. Botond Babes-Bolyai University, Faculty of Physics