4th EucheMs chemistry congress

Poster Session 1
s859
chem. Listy 106, s587–s1425 (2012)
Poster session 1 - Physical, theoretical chemistry
P - 0 0 0 1
SeCtor ModeL SCheMe for PLACeMent of
exPLiCit wAter MoLeCuLeS for PKA
PrediCtion
r. ABrAMSon 1 , K. BALdridGe 1
1 Organic Chemistry Institute, Organic Chemistry Institute,
Zürich, Switzerland
Accurate prediction of the properties associated with proton
transfer reactions, in particular the acidity dissociation constant
(K ), are a benchmark challenge for theory. Considerable efforts
a
have been made in the last decade towards prediction within
0.5 units, [1] which is the minimum level of accuracy for many
problems such as structure based drug design. [2] Hybrid
approaches, referred to as continuum cluster (CC), are the most
recent and promising development in pKa prediction. [1, 3, 4, 5] They
attempt to capture some of the missing first solvation shell effects
by adding a small number (< 4) solvent molecules explicitly
around the solute embedded in the solvent cavity. However,
a number of practical challenges arise in application of this
method due to the need to have a consistent framework for
determination of optimal number and position of solvent
molecules surrounding the solute. We propose a sector model
approach to investigate in greater detail the role of explicit
first-shell solvation of a set of carboxylic acids and their conjugate
bases. This model offers the possibility of systematizing the study
of these effects according to the degree of solvation (S ) and the
D
configuration of solvation (S ), which allows a number of rules
C
for future prediction to be elucidated. Furthermore, prediction
within 1kcal/mol, a chemically significant bound, is demonstrated,
for a diverse set of carboxylic acids.
references:
1. Ho, J., Coote, M.L., 2011, Wires Comput. Mol. Sci., 2011,
1(5), 649-660
2. Klicic, J.J. Friesner, R.A., Liu, S., Guida, W., J. Phys.
Chem. A, 2002, 106, 1327-1335
3. Pliego, J.R., Riveros, J.M., J. Phys. Chem. A, 106, 2002,
7434-7439
4. Eckert, F., Diedenhofen, M., Klamt, A., Molecular
Physics, 2010, 108 (3), 229-241
5. Kelly, C.P., Cramer, C.J., Truhlar, D.G., J. Phys. Chem. A,
2006, 110 (7), 2493-9
Keywords: pKa prediction; continuum cluster; explicit solvent;
sector model;
4 th EucheMs chemistry congress
P - 0 0 0 2
theoretiCAL inveStiGAtionS on eLeCtroniCS
StruCture, And CheMiCAL BondinG on
iridAthiABenzene And iridAoxABenzne
A. eLAhe 1 , r. GhiASi 1
1 Islamic Azad University East Tehran Branch Qiam Dasht,
Chimistry, Tehran, Iran
The electronic structure and properties of the Iridathiabenzene
and Iridaoxabenzne isomers have been investigated using the
hybrid density functional mpw1pw91 theory. The energetic aspect
shows that trans-ortho isomer is the most stable isomer. This is
compatible with principles of minimum energy and minimum
polarizability. Molecular orbital analysis shows a linear
correlation between hardness and anisotropic polarizability values
for Iridathiabenzene and iridaoxabenzene isomers. The structural
and natural bond analysis (NBO) results illustrate electronic
delocalization in these rings. Also, the study of non linear optical
properties of these molecules indicate a good correlation between
b and E(HOMO) for iridathiabenzene. The results from natural
tot
bond orbital (NBO) analysis have provided insights into Ir–ligand,
P-H and P-H bonding.
apical basal
Keywords: Isomers; Bond energy; Analytical Methods;
Metallacycles;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc