J Chem Crystallogr (2011) 41:1520–1527
1521
above. The experimental infrared spectrum for this sample
is also obtained and compared with the theoretical findings.
We are not aware of any other experimental data to com-
pare for the reported vibrational modes. We believe that
our detailed quantum chemical study will aid in clarifying
the experimentally obtained data.
should represent a better point on the potential energy
surface. In order to fulfill this requirement, we applied
three-stage procedure for all of our calculations. First,
relatively small 6-31G basis set was employed for a linear
(tight self consistent field (SCF) convergence criteria)
search for local minima on the potential energy surface of
the system to obtain reliable initial guesses and reasonable
geometries. Second, starting from these equilibrium struc-
tures, the stable method [26, 27] was used to establish a
stable wave function but using the larger 6-311??G(d, p)
basis set. Finally, geometry optimization, natural bond
orbital (NBO) analysis (NBO 3.1 version included into
Gaussian package [28]) and frequency calculations (a
procedure to evaluate the vibrational normal modes) were
performed. Both of the infrared intensities and Raman
activities are reported since some of the infrared inactive
vibrations (because of the lack of change in dipole
moment) are active in Raman spectroscopy because Raman
activity is associated with the polarizability of the mole-
cule, and infrared is associated with the change of a dipole
moment. The experimental infrared spectrum for this
sample is also obtained and reported. We are not aware of
any other experimental data to compare for the reported
vibrational modes, we believe that the presented detailed
quantum chemical study will aid in clarifying the experi-
mental data available. Quadratically convergent SCF
procedure was used for the optimization at the B3LYP/6-
311??G(d, p) level of theory. The vibrational frequencies,
calculated at the same level, were used for the character-
ization of stationary points and for zero-point energy (ZPE)
corrections. The zero-point vibrational energy ZPVE (or
ZPE) results from the vibrational motion of the molecular
systems even at 0 K and is calculated from a harmonic
oscillator model as a sum of contributions from all the
vibrational modes of the system. Most partition function
formulae assume that the zero of energy is the energy of the
ground state of the studied system (ETOTAL = EELEC-
Results and Discussion
X-Ray Crystallography
A suitable single crystal was mounted on a glass fiber and
data collection was performed on a STOE IPDSII image
˚
plate detector using Mo Ka radiation (k = 0.71073 A).
Details of the crystal structure are given in Table 1. Data
collection and cell refinement: Stoe X-AREA [17]. Data
reduction: Stoe X-RED [17]. Molecular drawings: ORTEP-
III and PLATON [18, 19]. Software used to prepare this
material for the publication: WinGX [20].
The structure was solved by direct-methods using
SHELXS-97 [21] and anisotropic displacement parameters
were applied to non-hydrogen atoms in a full-matrix least-
squares refinement based on F2 using SHELXL-97 [21].
All carbon hydrogens were positioned geometrically and
refined by a riding model with Uiso 1.2 times that of
attached atoms. 1800 Friedel pairs were averaged before
the final refinement.
Computational Procedure
All calculations were carried out by solving the Kohn–
Sham equations in the DFT framework. We have employed
the generalized gradient approximations (GGA) using the
functionals of Becke’s three-parameter hybrid exchange
functional [22] and the Lee–Yang–Parr (LYP) non-local
correlation functional [23].
The appropriateness of the DFT based quantum chemi-
cal studies for calculation of geometries, total energies,
fundamental normal modes (in terms of infrared-absorption
intensities and Raman-scattering activities) to serve as an
indirect probe for the experimental studies is discussed in
the literature [24, 25]. The suitability of the GGA and LDA
(Local Density Approximations) methods for the aimed
physical and chemical properties and importance of the
polarization basis functions and well converged wave
functions are outlined in these studies. In the present study,
6-311??G(d, p) basis set is employed in order to optimize
the geometry. This size of basis set (diffuse functions
together with polarization functions) fulfills the necessary
requirements. Since the used basis set is large and results as
O(N4) computation expense (with N is the system size), the
starting geometry for a long lasting optimization procedure
? EZPE). All the stationary points were positively
TRONIC
identified for the minima (no imaginary frequency) or
transition states (only one imaginary frequency) or higher-
order saddle points (more than one imaginary frequency).
All of the obtained molecular orbitals (Highest Occupied
Molecular Orbital; HOMO and Lowest Unoccupied
Molecular Orbital; LUMO) are depicted at the same level
of theory (see Fig. 3). Chemcraft [29] program is made use
of for analyzing the outputs of the Gaussian package and
also for drawing MO energy levels, HOMO–LUMO pic-
tures and NBO analysis with dipole moment figures;
namely 3 and 4. Computations were carried out using the
program package Gaussian-03 [28] installed on our parallel
computing laboratory (linux cluster with 986 CPUs at
C¸ ankaya university) and because of the time complexity,
Linda package was utilized for parallel computations.
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Yueksektepe, Cigdem
