- Email: [email protected]
Ab initio powder structure analysis and theoretical study of two thiazole derivatives
Journal of Molecular Structure 1039 (2013) 153–159
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc
Ab initio powder structure analysis and theoretical study of two thiazole derivatives Dipak K. Hazra a, Monika Mukherjee a, Alok K. Mukherjee b,⇑ a b
Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India Department of Physics, Jadavpur University, Jadavpur, Kolkata 700 032, India
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
" Ab-initio structure determination
Two aminothiazole and benzothiazole derivatives have been structurally characterized using laboratory X-ray powder diffraction data along with an analysis of their Hirshfeld surfaces and evaluation of electronic structures via DFT method.
from X-ray powder diffraction data. " Interplay of NAH N/S hydrogen bonds and C/NAH p interactions. " Hirshfeld surface and 2D-fingerprint plot. " Electronic properties calculation by the DFT method.
a r t i c l e
i n f o
Article history: Received 2 January 2013 Received in revised form 28 January 2013 Accepted 28 January 2013 Available online 15 February 2013 Keywords: X-ray powder diffraction Ab-initio structure solution DFT calculation Hirshfeld surface analysis
a b s t r a c t Crystal structures of 2-amino-5-methylthiazole (1) and 4-(6-methyl-2-benzothiazolyl) aniline (2) have been determined from laboratory X-ray powder diffraction data along with an analysis of the Hirshfeld surfaces and 2D-fingerprint plots, facilitating a comparison of intermolecular interactions. The DFT optimized molecular geometries in (1) and (2) agree closely with those obtained from the crystallographic studies. An interplay of NAH N/S hydrogen bonds and C/NAH p interactions connects the molecules of (1) and (2) into two-dimensional framework. Hirshfeld surface analysis of (1) indicates that the H H and H p contacts can account for 56.9% of the Hirshfeld surface area, whereas the corresponding fraction in (2) is 80.5%. Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction Intermolecular interactions, in particular hydrogen bonds, are the key factor for the design of molecular assemblies of neutral organic molecules with donor and acceptor functionalities [1,2]. Many of the synthons frequently observed in supramolecular chemistry involve strong O/NAH O/N hydrogen bonds, which ⇑ Corresponding author. Tel.: +91 33 24138917; fax: +91 33 24146584. E-mail address: [email protected] (A.K. Mukherjee). 0022-2860/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.molstruc.2013.01.077
provide the requisite robustness and reproducibility to create a variety of solid-state architectures described as layers, rods, tapes, ribbons, channels, helices and sheets [3]. In addition to these relatively strong hydrogen bonds, weak hydrogen bonds such as CAH O/N and NAH S, and the C/NAH p interactions are also important in describing the self-assembly process [4–7]. The influence of these weak interactions can be evaluated by comparing the structural features as well as the interplay of hydrogen bonds in building possible supramolecular aggregation in closely related compounds.
154
D.K. Hazra et al. / Journal of Molecular Structure 1039 (2013) 153–159
In this context, the heterocyclic molecule 2-amino-1,3-thiazole (CSD code: BAWKEP10) possessing two strong donors (NH2), and both strong (Nsp2) and weak (S) acceptors constitute an ideal structural scaffold with a rigid core. To study the effect of substitutions in the thiazole ring on the potential of hydrogen-bonding ability of amino nitrogen to either the sulfur atom or the sp2 nitrogen atom, we decided to investigate the solid-state packing modes in aminothiazoles and benzothiazoles. In addition, many aminothiazole and benzothiazole derivatives have been extensively studied for a range of biological and industrial applications [8,9]. A search of the Cambridge Structural Database (CSD; Version 5.33, November 2011 release) reveals that there are 623 crystal structures containing either an aminothiazole or a benzothiazole moiety, with 356 of those being purely organic compounds. If we restrict our search with an amino or aminophenyl group at the 2-position of the thiazole ring, only four structures (excluding duplicate structure determination) with refcodes BAWKEP 10 [10], EYIXUF [11], IFUREH [12] and SESWOD [13] are found. The crystal structures of all these compounds have been determined using single-crystal X-ray analysis. Although single-crystal X-ray diffractometry is the method of choice for determination of crystal structure of molecular compounds, an intrinsic limitation of this approach is the requirement to grow single crystals of appropriate size and quality that make them amenable to structure analysis. As many important materials can be prepared only as microcrystalline powders, reliable procedures for determining crystal structures from powder X-ray diffraction data are highly desirable. With the developments in direct-space methodologies for structure solution [14,15], ab-initio crystal structure analysis of molecular solids can be accomplished from X-ray powder diffraction data [16,17]. This idea prompted us to investigate the structural features of two aminothiazole and benzothiazole derivatives using X-ray powder diffraction and to analyze the role of NAH N and NAH S hydrogen bonds in building possible supramolecular architecture. The results of structural study of 2-amino-5-methylthiazole (1) and 4-(6-methyl-2-benzothiazolyl) aniline (2) (Scheme 1) are reported here along with the DFT calculations to study the molecular geometry and the electronic structure. The structure of a different polymorph of (1) crystallizing in the monoclinic space group P21 is known (CSD code: XUVNIM) from single-crystal X-ray analysis [18]. An investigation of close intermolecular interactions in compounds (1), (2), XUVNIM and a few related aminothiazole and benzothiazole derivatives via Hirshfeld surface analysis is also presented.
2.2. Indexing and structure analysis The indexing of X-ray powder patterns of (1) and (2) were carried out using the program NTREOR [19]. The full pattern decomposition was performed with EXPO2004 [20] following the Le Bail algorithm [21], and using a split type pseudo-Voigt peak profile function [22]. Statistical analysis of powder patterns using the FINDSPACE module of EXPO2004 indicated P21/n and P212121 as the most probable space groups for (1) and (2), respectively, which were used for structure solution. The crystal structures were solved by global optimization of structural models in direct space using the simulated annealing technique as implemented in the program DASH [23]. The initial molecular geometry used in DASH was adopted from the standard data incorporated in the MOPAC 2009 program [24], and optimized a priori by an energy gradient method. Solutions with a chemically reasonable packing arrangement and no significant misfit between the observed and calculated powder patterns were used as the starting models for the Rietveld refinement [25], which was carried out using the program GSAS [26] with an EXPGUI [27] interface. The background was described by the shifted Chebyshev function of the first kind with 14 points regularly distributed over the entire 2h range for both compounds. The lattice parameters, background coefficients and profile parameters were refined initially followed by the refinement of positional coordinates of non-hydrogen atoms with soft constraints on bond lengths and bond angles, and a planar restraint for the thiazole and phenyl rings. A fixed isotropic displacement parameter of 0.04 Å2 for all non-hydrogen atoms was maintained. Hydrogen atoms were placed in the calculated positions with a common Uiso value of 0.07 Å2. In the final stages of refinement, a preferred orientation correction using the generalized spherical harmonic model was applied. Final Rietveld refinement with a good agreement between the observed and the calculated powder patterns (Fig. 1a and b) converged to low residual parameters Rp, Rwp and v2 (Table 1). 2.3. Hirshfeld surface analysis
2. Experimental methods
Hirshfeld Surfaces [28] and the associated 2D-fingerprint plots [29] were calculated using Crystal Explorer [30], which accepts a structure input file in the CIF format. Bond lengths to hydrogen atoms were set to typical neutron values (CAH = 1.083 Å and NAH = 1.009 Å). For each point on the Hirshfeld isosurface, two distances de, the distance from the point to the nearest nucleus external to the surface, and di, the distance to the nearest nucleus internal to the surface, are defined. The normalized contact distance (dnorm) based on de and di is given by
2.1. Materials and X-ray data collection
dnorm ¼
The compounds 2-amino-5-methylthiazole (1) and 4-(6methyl-2-benzothiazolyl) aniline (2) were purchased from Sigma Aldrich, NY, USA (CAS Nos. 7305-71-7 and 92-36-4), and were used without further purification. X-ray powder diffraction data of compounds (1) and (2) were collected at 293(2) K with a Bruker D8 Advance powder diffractometer using Cu Ka radiation (k = 1.5418 Å) operating in the Bragg–Brentano geometry.
where rvdW and r vdW being the van der Waals radii of the atoms. The e i value of dnorm is negative or positive depending on intermolecular contacts being shorter or longer than the van der Waals separations. The parameter dnorm displays a surface with a red–white–blue color scheme, where bright red spots highlight shorter contacts, white areas represent contacts around the van der Waals separation, and blue regions are devoid of close contacts.
ðdi rvdW Þ ðde r vdW Þ e i þ vdW r vdW ri e
2.4. Computational study
Scheme 1.
Isolated molecule DFT calculations were carried out using the DMol3 code [31] of the Materials Studio System of programs in the framework of a generalized-gradient approximation (GGA) [32]. The starting atomic coordinates were taken from the final X-ray refinement cycle. The geometry of the molecules was fully
D.K. Hazra et al. / Journal of Molecular Structure 1039 (2013) 153–159
155
Fig. 1. Final Rietveld plot of (a) C4H6N2S (1) and (b) C14H12N2S (2). Red crosses: observed pattern, green curve: calculated pattern, magenta curve: difference curve. The intensity in the high-angle region has been multiplied by a factor of 10. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
optimized using the hybrid exchange-correlation functional BLYP [33,34] and a double numeric plus polarization (DNP) basis set. The electronic structures of (1) and (2) were also calculated at the same level. No constraints to bonds, angles or dihedral angles were applied in the calculations, and all atoms were allowed free to optimize. 3. Results and discussion 3.1. Crystal and molecular Structure The observed X-ray powder diffraction profile of (1) did not match with the simulated powder pattern of 2-amino-5-methyl1,2-thiazole (CSD code: XUVNIM) based on the single crystal structure [18]. There were considerable differences in observed PXRD
peak positions of bulk material of (1) and that calculated for the single crystal structure (Fig. S1, vide 2h angles 32.0°, 33.5°), indicating that compound (1) exists in different polymorphic forms. All subsequent discussions relate to structure analysis of a new polymorph of (1) using X-ray powder diffraction. The molecule (1) (Fig. 2a) containing a thiazole ring (S1/C2/N1/ C3/C4) is essentially planar with an r.m.s. fit of the atomic positions (excluding N2) of 0.041 Å; the exocyclic amino atom N2 deviates from the least-squares plane through atoms S1/N1/C2AC5 by 0.142(3) Å. In molecule (2) (Fig. 2b), the dihedral angle between two almost planar benzothiazole (S1/N1/C2AC9) and aminophenyl (N2/C10AC15) fragments is 7.3(1)°. The observed CAS bond lengths in (1) and (2) lying in the range 1.727(2)–1.755(3) Å, although marginally shorter than the lower-quartile value (1.809 Å) for single bonds between three-connected C and
156
D.K. Hazra et al. / Journal of Molecular Structure 1039 (2013) 153–159
Table 1 Crystal data and structure refinement parameters for C4H6N2S (1) and C14H12N2S (2).
Chemical formula Mr Crystal system Space group, Z a, b, c (Å) b (°) V (Å3) D (g cm3) 2hmin, 2hmax 2hstep (°) Counting time/step (s) Rp, Rwp, R(F2) Rexp, v2 Data/restraints/ parameters
(1)
(2)
C4H6N2S 114.17 Monoclinic P21/n, 4 14.4456(4), 5.4634(2), 6.7739(2) 93.004(1) 533.9(1) 1.421 13.0, 100.00 0.02 4 0.0448, 0.0712, 0.1075 0.064, 1.299 4300, 24, 49
C14H12N2S 240.32 Orthorhombic P212121, 4 19.6411(20), 11.2389(11), 5.5798(4) 90.0 1231.7(2) 1.296 8.0, 100.00 0.02 4 0.0300, 0.0397, 0.0756 0.032, 2.097 4500, 70, 78
two-connected S atom [35,36], are comparable with the corresponding distances reported for thiazole derivatives [37,38]. The C2AN1 [1.303(3)–1.310(2) Å] and C3AN1 [1.373(2)–1.393(3) Å] bond distances in (1) and (2) agree well with the mean values of C@N [1.31 Å] and CAN [1.38 Å] bond lengths based on 193 ACsp2@NACsp2A fragments obtained with MOGUL [39] from the CSD search of related organic compounds. The hydrogen-bonding interactions in (1) and (2), both having two NH proton donating bonds, are significantly different, specially in terms of accepting centers, the nitrogen and sulfur atoms, of the heterocyclic ring. In the molecular structure of polymorph of (1), XUVNIM, both amino H atoms are hydrogen bonded to N and S atoms of the thiazole ring, thus generating a cyclic R44 (14) synthon [40]. (1), however, does not form an Rnm (X) dimer, a feature common in many 2-aminothiazole derivatives [10,11,38], but alternately forms a NAH N hydrogen-bonded polymeric chain. The amino atom N2 in the molecule (1) at (x, y, z) acts as hydrogenbond donor, via atom H2A, to thiazole ring atom N1 in the molecule at (½ x, ½ + y, ½ z), so generating an infinite onedimensional C 11 (4) chain [40] propagating along the [0 1 0] direction. A CAH p contact from C3AH3 to the thiazole ring (S1/C2/ N1/C3/C4) links the parallel chains into a two-dimensional stack
Fig. 2. Molecular structures of: (a) C4H6N2S (1) and (b) C14H12N2S (2) with atom numbering scheme.
(Fig. 3a). Examination of structure of (1) for interactions involving sulfur atom (another possible acceptor in the molecule) reveals that the closest S H (C/N) intermolecular distance is S1 H5A(C5)i [symmetry code: (i) x, y 1, z] of 3.07 Å, [S1 H2B (N2)ii of 3.14 Å [symmetry code: (ii) x, 1 y, z)], with S1 H5AiAC5i angle of 134°, [S1 H2BiiAN2ii angle of 160°], which excludes any possible C/NAH S hydrogen bond formation. In (2), however, the amino atom N2 in the molecule at (x, y, z) is hydrogen bonded to S1 atom of the benzothiazole moiety in the molecule at (1 x, ½ + y, ½ z) to form a C 11 (8) chain [40] propagating along the [0 1 0] direction. The N S distance of 3.279(3) Å is significantly shorter than the average distance [3.75 Å] calculated using 176 structures in the CSD for NAH S hydrogen bonds to a Csp2ASACsp2 system, while the NAH S angle of 142° is comparable to the similar calculated from the CSD search. The chains in (2) are further connected via N2AH1A N1 and N2AH1B N1 weak hydrogen bonds (Table 2), thus producing a herringbone framework built with fused R34 (20) rings [40] (Fig. 3b). The Hirshfeld surfaces [41] provide a relatively new tool for analyzing packing modes as well as intermolecular interactions in molecular crystals while maintaining a whole-of-molecule approach. They are constructed by partitioning the space in a crystal into regions where the electron density from the sum of spherical atoms of the molecule is greater than the corresponding sum over the crystal [42]. Two-dimensional fingerprint plots [29] complement the Hirshfeld surfaces, quantitatively summarizing the nature and type of intermolecular interactions experienced by the molecules in the crystal. This analysis can be very valuable in the identification and quantitative comparison of similarities and subtle differences among the intermolecular interactions in polymorphs and related compounds [43,44]. The Hirshfeld surfaces of compounds (1) and (2) are illustrated in Fig. 4a and b, showing surfaces that have been mapped over a dnorm range of 0.5 to 1.0 Å. The color codes from red for short dnorm ranges to blue for long dnorm ranges were employed. The dominant interactions between the amine NH2 group and the thiazole ring N1 atom in (1) and S1 in (2) can be seen in the Hirshfeld surface as red areas marked as ‘a’, ‘b’ in Fig. 4a and ‘e’, ‘f’ in Fig. 4b. The light red spots labeled as ‘c’ and ‘d’ in Fig. 4a originate from CAH p interactions in (1) and that marked as ‘g’ in Fig. 4b is due to weak NAH N interaction in (2). Other bright red spot (marked as ‘h’) in Fig. 4b correspond to H H contacts in (2). The corresponding 2D fingerprint plot of (1) (Fig. 4a) exhibits characteristic spikes in the region 2.1 < de + di < 2.9 Å (labeled as ‘a’ and ‘b’). The upper spike ‘a’ in Fig. 4a represents the donor spike (amino H atom interacting with the N atom of the thiazole ring), and the lower spike ‘b’ being the acceptor spike (thiazole N atom interacting with the amino H atom). The wings (Fig. 4a, marked as ‘c’ and ‘d’) in the (di,de) regions of (1.6 Å, 1.0 Å), and (1.0 Å, 1.6 Å) are attributable to the CAH p interaction in (1). For compound (2), the wings in the (di + de) region of (2.3 Å, 2.9 Å) and (2.9 Å, 2.3 Å) in Fig. 4b are due to the H S/p interactions. The central spike extending upto (di,de) region of (0.8 Å, 0.8 Å) in Fig. 4b reflects a high % of H H contacts in (2). The relative contributions of different interactions to the Hirshfeld surface calculated for (1), (2), BAWKEP10 and XUVNIM as well as a few related aminothiazole and benzothiazole compounds (Fig. S2) retrieved from the CSD are shown in Fig. 5. Replacement of the thiazole ring and the amino (NH2) group in (1) by a benzothiazole ring and an aminophenyl group in (2) decreases significantly the contribution of H S contacts to the Hirshfeld surface from 18.6% in (1) to 4.2% in (2) with a corresponding two-fold increase of the H p interactions from 14.8% in (1) to 31.8% in (2). The reduced contribution of H S interactions to the Hirshfeld surface in (2) compared to that in BAWKEP10 and (1) can be attributed to the fact that a phenyl ring fusion across the C3AC4 bond
157
D.K. Hazra et al. / Journal of Molecular Structure 1039 (2013) 153–159
Fig. 3. (a) A view of two-dimensional stacking of molecules in C4H6N2S (1) and (b) a view of herringbone framework built with fused R34 (20) rings in C14H12N2S (2). [Symmetry code: (ii) 1 x, ½ + y, ½ z and (iii) 1 x, ½ + y, ½ z].
Table 2 Intermolecular contacts for C4H6N2S (1) and C14H12N2S (2) (Å, °). D-HA
d(D-H)
d(H A)
d(D A)
<(DHA)
[Symmetry transform]
C4H6N2S (1) N2AH2A N1 C3AH3 Cg1
0.86 0.96
2.20 2.70
3.000(3) 3.425(1)
154 135
[½ x, ½ + y, ½ z] [½ x, ½ + y, ½ z]
C14H12N2S (2) N2AH1B S1 N2AH1B Cg1 N2AH1A N1 N2AH1B N1
0.87 0.87 0.87 0.87
2.55 2.35 2.72 2.70
3.279(3) 3.046(2) 3.302(2) 3.369(2)
142 138 126 134
[1 x, [1 x, [1 x, [1 x,
½ + y, ½ + y, ½ + y, ½ + y,
½ z] ½ z] ½ z] ½ z]
Cg1 is the centroid of thiazole ring (S1/C2/N1/C3/C4).
and a bulky aminophenyl substitution at the C2 position of the thiazole ring in (1) restrict close intermolecular contacts involving the sulfur atom. It is evident from Fig. 5 that the molecular interactions in substituted aminothiazoles such as compound (1), HIYLOQ [45], UNOMEP [46], XUNKAS [38] and XUVNIM [18] are predominantly of H H, H N, H S and H p types, which can account for about 87–97% (96.0% in BAWKEP10, 97.3% in (1), 91.7% in HIYLOQ, 87.7% in UNOMEP, 96.9% in XUNKAS and 94.8% in XUVNIM) of the Hirshfeld surface area. In the benzothiazole derivatives, however, the H H and H p contacts together contributed about 70–82% (80.5% in (2), 70.3% in IFUREH [12], 77.5% in JEVTIO [47], 73.1% in OLUZAX [48], 81.2% in YEVRAS [49] and 71.2% in WIHKUT [50]) to the Hirshfeld surface area; the remaining contributions were distributed mostly among the H N, H S, H O and S S interactions. 3.2. Electronic structure Superposition of molecular conformations of (1) and (2) as established by the X-ray study and quantum mechanical calculations show a good agreement (Figs. S3 and S4); the r.m.s. deviations between the coordinates obtained by geometry optimization and X-ray structure analysis are 0.042 Å (for 1) and 0.046 Å (for 2), respectively (Table S1). The net charges of atoms and dipoles calculated using BLYP functional indicate that the sulfur and nitrogen atoms in molecules (1) and (2) bear negative charges, while the carbon atoms in the thiazole core bear positive charges. The atomic charges estimated from the Mulliken population analysis appear to be consistent with the electronegativity of constituent atoms. Due to this charge redistribution, the dipole of the molecules (1) and (2) becomes 0.99 a.u. and 1.09 a.u., respectively.
The charge densities of HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) are depicted in Fig. 6a (for 1) and Fig. 6b (for 2) showing bonding- antibonding patterns in the molecules. The orbital energy level analysis for (1) and (2) at the BLYP level shows EHOMO and ELUMO values of 4.73 eV, 0.91 eV for (1), and 4.73 eV, 1.96 eV for (2), respectively. The differences between the orbital energies corresponding to HOMO-1 ? HOMO-4 energy levels in (1) and (2) are greater than 0.05 eV, which indicate that the energy levels in compounds (1) and (2) are non-degenerate. Similar conclusion can be drawn from the LUMO + 1 ? LUMO + 4 orbital energy calculations for both molecules. 4. Conclusions The results of the crystal structure determination using X-ray powder diffraction of two aminothiazole and benzothiazole derivatives, 2-amino-5-methylthiazole (1) and 4-(6-methyl-2-benzothiazolyl) aniline (2) clearly demonstrate an interplay of NAH N/S hydrogen bonds and C/NAH p interactions generating two-dimensional framework. The molecular geometry and the electronic structures of (1) and (2) have been analyzed by the DFT calculations. The observed molecular conformations of compounds as established by the X-ray analyses agree well with that obtained from the quantum mechanical calculations. A comparison of close intermolecular interactions in (1), (2) and a few related compounds using the Hirshfeld surface analysis indicated that the H H, H N, H S and H p interactions can account for about 87–97% of the Hirshfeld surface area in substituted aminothiazoles, whereas in benzothiazole derivatives the H H and H p contacts contributed about 70–82% of the Hirshfeld surface area. The compounds investigated here reveal the influence of
158
D.K. Hazra et al. / Journal of Molecular Structure 1039 (2013) 153–159
Fig. 4. Hirshfeld surface and 2D fingerprint plot of: (a) C4H6N2S (1) and (b) C14H12N2S (2).
Fig. 5. The relative contributions of various intermolecular contacts to the Hirshfeld surface area in (1), (2) and related compounds retrieved from the CSD.
Fig. 6. Charge density isosurface of (a) HOMO and LUMO orbitals in C4H6N2S (1) and (b) HOMO and LUMO orbitals in C14H12N2S (2) set at 0.03 eÅ3 calculated by the DFT method [surfaces in yellow (+) and blue ()]. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
D.K. Hazra et al. / Journal of Molecular Structure 1039 (2013) 153–159
weak intermolecular forces in building supramolecular assembly in the solid state. Acknowledgements Financial support from the University Grants Commission, New Delhi, through the DRS (SAP-II) program for purchasing the X-ray powder diffractometer in the Department of Physics, Jadavpur University, is gratefully acknowledged. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.molstruc.2013. 01.077. References [1] G.R. Desiraju, Angew. Chem. Int. Ed. 46 (2007) 8342. [2] E.R.T. Tiekink, J.J. Vittal, M. Zaworotko (Eds.), Organic Crystal Engineering: Frontiers in Crystal Engineering, John Wiley & Sons Ltd., Chichester, UK, 2010. [3] F.H. Allen, W.D.S. Motherwell, P.R. Raithby, G.P. Shields, R. Taylor, New J. Chem. 23 (1999) 25. [4] M. Nishio, CrystEngComm 6 (2004) 130. [5] G.R. Desiraju, T. Steiner, The Weak Hydrogen Bond in Structural Chemistry and Biology, Oxford University Press, Oxford, UK, 1999. [6] C.N. Sundaresan, S. Dixit, P. Venugopalan, J. Mol. Struct. 693 (2004) 205. [7] E. Arunan, G.R. Desiraju, R.A. Klein, J. Sadlej, S. Scheiner, I. Alkorta, D.C. Clary, R.H. Crabtree, J.J. Dannenberg, P. Hobza, H.G. Kjaergaard, A.C. Legon, B. Mennucci, D.J. Nesbitt, Pure Appl. Chem. 83 (2011) 1619. [8] B.S. Holla, K.V. Malini, B.S. Rao, B.K. Sarojini, N.S. Kumari, Eur. J. Med. Chem. 38 (2003) 313. [9] I. Hutchinson, J. Med. Chem. 45 (2002) 744. [10] C. Caranoni, J.P. Reboul, Acta Cryst. B38 (1982) 1255. [11] D.E. Lynch, I. McClenaghan, Acta Cryst. C60 (2004) o592. [12] Y. Zhang, Z.-H. Su, Q.-Z. Wang, L. Teng, Acta Cryst. E64 (2008) o2065. [13] W.-S. Wang, M. Gao, X. Chen, B. Liu, Acta Cryst. E62 (2006) o5668. [14] W.I.F. David, K. Shankland, L.B. McCusker, C. Baerlocher (Eds.), Structure Determination from Powder Diffraction Data, Oxford University Press, New York, 2002. [15] K.D.M. Harris, E.Y. Cheung, Chem. Soc. Rev. 33 (2004) 526. [16] A. Bhattacharya, S. Ghosh, K. Kankanala, V.R. Reddy, K. Mukkanti, S. Pal, A.K. Mukherjee, Chem. Phys. Lett. 493 (2010) 151.
159
[17] K.D.M. Harris, Mater. Manuf. Process. 24 (2009) 293. [18] D.E. Lynch, Private, Communication, 2009. [19] A. Altomare, C. Giacovazzo, A. Guagliardi, A.G.G. Moliterni, R. Rizzi, E. Werner, J. Appl. Cryst. 33 (2000) 1180. [20] A. Altomare, R. Caliandro, M. Camalli, C. Cuocci, C. Giacovazzo, A.G.G. Moliterni, R. Rizzi, J. Appl. Cryst. 37 (2004) 1025. [21] A. Le Bail, H. Duroy, J.L. Fourquet, Mater. Res. Bull. 23 (1988) 447. [22] H.J. Toraya, J. Appl. Cryst. 19 (1986) 440. [23] W.I.F. David, K. Shankland, J. van de Streek, E. Pidcock, W.D.S. Motherwell, J.C. Cole, J. Appl. Cryst. 39 (2006) 910. [24] J.J. Stewart, J. Mol. Model. 13 (2007) 1173. [25] H.M. Rietveld, Acta Cryst. 22 (1967) 151. [26] A.C. Larson, R.B. Von Dreele, General Structure Analysis System (GSAS), Los Alamos National Laboratory Report LAUR, 2000, p. 86. [27] B.H. Toby, J. Appl. Cryst. 34 (2001) 210. [28] J.J. McKinnon, A.S. Mitchell, M.A. Spackman, Chem. Eur. J. 4 (1998) 2136. [29] M.A. Spackman, J.J. McKinnon, CrystEngComm 4 (2002) 378. [30] S.K Wolff, D.J. Grimwood, J.J. McKinnon, D. Jayatilaka, M.A. Spackman, Crystal Explorer. University of Western Australia, Perth, Australia, 2007.
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc
Ab initio powder structure analysis and theoretical study of two thiazole derivatives Dipak K. Hazra a, Monika Mukherjee a, Alok K. Mukherjee b,⇑ a b
Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India Department of Physics, Jadavpur University, Jadavpur, Kolkata 700 032, India
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
" Ab-initio structure determination
Two aminothiazole and benzothiazole derivatives have been structurally characterized using laboratory X-ray powder diffraction data along with an analysis of their Hirshfeld surfaces and evaluation of electronic structures via DFT method.
from X-ray powder diffraction data. " Interplay of NAH N/S hydrogen bonds and C/NAH p interactions. " Hirshfeld surface and 2D-fingerprint plot. " Electronic properties calculation by the DFT method.
a r t i c l e
i n f o
Article history: Received 2 January 2013 Received in revised form 28 January 2013 Accepted 28 January 2013 Available online 15 February 2013 Keywords: X-ray powder diffraction Ab-initio structure solution DFT calculation Hirshfeld surface analysis
a b s t r a c t Crystal structures of 2-amino-5-methylthiazole (1) and 4-(6-methyl-2-benzothiazolyl) aniline (2) have been determined from laboratory X-ray powder diffraction data along with an analysis of the Hirshfeld surfaces and 2D-fingerprint plots, facilitating a comparison of intermolecular interactions. The DFT optimized molecular geometries in (1) and (2) agree closely with those obtained from the crystallographic studies. An interplay of NAH N/S hydrogen bonds and C/NAH p interactions connects the molecules of (1) and (2) into two-dimensional framework. Hirshfeld surface analysis of (1) indicates that the H H and H p contacts can account for 56.9% of the Hirshfeld surface area, whereas the corresponding fraction in (2) is 80.5%. Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction Intermolecular interactions, in particular hydrogen bonds, are the key factor for the design of molecular assemblies of neutral organic molecules with donor and acceptor functionalities [1,2]. Many of the synthons frequently observed in supramolecular chemistry involve strong O/NAH O/N hydrogen bonds, which ⇑ Corresponding author. Tel.: +91 33 24138917; fax: +91 33 24146584. E-mail address: [email protected] (A.K. Mukherjee). 0022-2860/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.molstruc.2013.01.077
provide the requisite robustness and reproducibility to create a variety of solid-state architectures described as layers, rods, tapes, ribbons, channels, helices and sheets [3]. In addition to these relatively strong hydrogen bonds, weak hydrogen bonds such as CAH O/N and NAH S, and the C/NAH p interactions are also important in describing the self-assembly process [4–7]. The influence of these weak interactions can be evaluated by comparing the structural features as well as the interplay of hydrogen bonds in building possible supramolecular aggregation in closely related compounds.
154
D.K. Hazra et al. / Journal of Molecular Structure 1039 (2013) 153–159
In this context, the heterocyclic molecule 2-amino-1,3-thiazole (CSD code: BAWKEP10) possessing two strong donors (NH2), and both strong (Nsp2) and weak (S) acceptors constitute an ideal structural scaffold with a rigid core. To study the effect of substitutions in the thiazole ring on the potential of hydrogen-bonding ability of amino nitrogen to either the sulfur atom or the sp2 nitrogen atom, we decided to investigate the solid-state packing modes in aminothiazoles and benzothiazoles. In addition, many aminothiazole and benzothiazole derivatives have been extensively studied for a range of biological and industrial applications [8,9]. A search of the Cambridge Structural Database (CSD; Version 5.33, November 2011 release) reveals that there are 623 crystal structures containing either an aminothiazole or a benzothiazole moiety, with 356 of those being purely organic compounds. If we restrict our search with an amino or aminophenyl group at the 2-position of the thiazole ring, only four structures (excluding duplicate structure determination) with refcodes BAWKEP 10 [10], EYIXUF [11], IFUREH [12] and SESWOD [13] are found. The crystal structures of all these compounds have been determined using single-crystal X-ray analysis. Although single-crystal X-ray diffractometry is the method of choice for determination of crystal structure of molecular compounds, an intrinsic limitation of this approach is the requirement to grow single crystals of appropriate size and quality that make them amenable to structure analysis. As many important materials can be prepared only as microcrystalline powders, reliable procedures for determining crystal structures from powder X-ray diffraction data are highly desirable. With the developments in direct-space methodologies for structure solution [14,15], ab-initio crystal structure analysis of molecular solids can be accomplished from X-ray powder diffraction data [16,17]. This idea prompted us to investigate the structural features of two aminothiazole and benzothiazole derivatives using X-ray powder diffraction and to analyze the role of NAH N and NAH S hydrogen bonds in building possible supramolecular architecture. The results of structural study of 2-amino-5-methylthiazole (1) and 4-(6-methyl-2-benzothiazolyl) aniline (2) (Scheme 1) are reported here along with the DFT calculations to study the molecular geometry and the electronic structure. The structure of a different polymorph of (1) crystallizing in the monoclinic space group P21 is known (CSD code: XUVNIM) from single-crystal X-ray analysis [18]. An investigation of close intermolecular interactions in compounds (1), (2), XUVNIM and a few related aminothiazole and benzothiazole derivatives via Hirshfeld surface analysis is also presented.
2.2. Indexing and structure analysis The indexing of X-ray powder patterns of (1) and (2) were carried out using the program NTREOR [19]. The full pattern decomposition was performed with EXPO2004 [20] following the Le Bail algorithm [21], and using a split type pseudo-Voigt peak profile function [22]. Statistical analysis of powder patterns using the FINDSPACE module of EXPO2004 indicated P21/n and P212121 as the most probable space groups for (1) and (2), respectively, which were used for structure solution. The crystal structures were solved by global optimization of structural models in direct space using the simulated annealing technique as implemented in the program DASH [23]. The initial molecular geometry used in DASH was adopted from the standard data incorporated in the MOPAC 2009 program [24], and optimized a priori by an energy gradient method. Solutions with a chemically reasonable packing arrangement and no significant misfit between the observed and calculated powder patterns were used as the starting models for the Rietveld refinement [25], which was carried out using the program GSAS [26] with an EXPGUI [27] interface. The background was described by the shifted Chebyshev function of the first kind with 14 points regularly distributed over the entire 2h range for both compounds. The lattice parameters, background coefficients and profile parameters were refined initially followed by the refinement of positional coordinates of non-hydrogen atoms with soft constraints on bond lengths and bond angles, and a planar restraint for the thiazole and phenyl rings. A fixed isotropic displacement parameter of 0.04 Å2 for all non-hydrogen atoms was maintained. Hydrogen atoms were placed in the calculated positions with a common Uiso value of 0.07 Å2. In the final stages of refinement, a preferred orientation correction using the generalized spherical harmonic model was applied. Final Rietveld refinement with a good agreement between the observed and the calculated powder patterns (Fig. 1a and b) converged to low residual parameters Rp, Rwp and v2 (Table 1). 2.3. Hirshfeld surface analysis
2. Experimental methods
Hirshfeld Surfaces [28] and the associated 2D-fingerprint plots [29] were calculated using Crystal Explorer [30], which accepts a structure input file in the CIF format. Bond lengths to hydrogen atoms were set to typical neutron values (CAH = 1.083 Å and NAH = 1.009 Å). For each point on the Hirshfeld isosurface, two distances de, the distance from the point to the nearest nucleus external to the surface, and di, the distance to the nearest nucleus internal to the surface, are defined. The normalized contact distance (dnorm) based on de and di is given by
2.1. Materials and X-ray data collection
dnorm ¼
The compounds 2-amino-5-methylthiazole (1) and 4-(6methyl-2-benzothiazolyl) aniline (2) were purchased from Sigma Aldrich, NY, USA (CAS Nos. 7305-71-7 and 92-36-4), and were used without further purification. X-ray powder diffraction data of compounds (1) and (2) were collected at 293(2) K with a Bruker D8 Advance powder diffractometer using Cu Ka radiation (k = 1.5418 Å) operating in the Bragg–Brentano geometry.
where rvdW and r vdW being the van der Waals radii of the atoms. The e i value of dnorm is negative or positive depending on intermolecular contacts being shorter or longer than the van der Waals separations. The parameter dnorm displays a surface with a red–white–blue color scheme, where bright red spots highlight shorter contacts, white areas represent contacts around the van der Waals separation, and blue regions are devoid of close contacts.
ðdi rvdW Þ ðde r vdW Þ e i þ vdW r vdW ri e
2.4. Computational study
Scheme 1.
Isolated molecule DFT calculations were carried out using the DMol3 code [31] of the Materials Studio System of programs in the framework of a generalized-gradient approximation (GGA) [32]. The starting atomic coordinates were taken from the final X-ray refinement cycle. The geometry of the molecules was fully
D.K. Hazra et al. / Journal of Molecular Structure 1039 (2013) 153–159
155
Fig. 1. Final Rietveld plot of (a) C4H6N2S (1) and (b) C14H12N2S (2). Red crosses: observed pattern, green curve: calculated pattern, magenta curve: difference curve. The intensity in the high-angle region has been multiplied by a factor of 10. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
optimized using the hybrid exchange-correlation functional BLYP [33,34] and a double numeric plus polarization (DNP) basis set. The electronic structures of (1) and (2) were also calculated at the same level. No constraints to bonds, angles or dihedral angles were applied in the calculations, and all atoms were allowed free to optimize. 3. Results and discussion 3.1. Crystal and molecular Structure The observed X-ray powder diffraction profile of (1) did not match with the simulated powder pattern of 2-amino-5-methyl1,2-thiazole (CSD code: XUVNIM) based on the single crystal structure [18]. There were considerable differences in observed PXRD
peak positions of bulk material of (1) and that calculated for the single crystal structure (Fig. S1, vide 2h angles 32.0°, 33.5°), indicating that compound (1) exists in different polymorphic forms. All subsequent discussions relate to structure analysis of a new polymorph of (1) using X-ray powder diffraction. The molecule (1) (Fig. 2a) containing a thiazole ring (S1/C2/N1/ C3/C4) is essentially planar with an r.m.s. fit of the atomic positions (excluding N2) of 0.041 Å; the exocyclic amino atom N2 deviates from the least-squares plane through atoms S1/N1/C2AC5 by 0.142(3) Å. In molecule (2) (Fig. 2b), the dihedral angle between two almost planar benzothiazole (S1/N1/C2AC9) and aminophenyl (N2/C10AC15) fragments is 7.3(1)°. The observed CAS bond lengths in (1) and (2) lying in the range 1.727(2)–1.755(3) Å, although marginally shorter than the lower-quartile value (1.809 Å) for single bonds between three-connected C and
156
D.K. Hazra et al. / Journal of Molecular Structure 1039 (2013) 153–159
Table 1 Crystal data and structure refinement parameters for C4H6N2S (1) and C14H12N2S (2).
Chemical formula Mr Crystal system Space group, Z a, b, c (Å) b (°) V (Å3) D (g cm3) 2hmin, 2hmax 2hstep (°) Counting time/step (s) Rp, Rwp, R(F2) Rexp, v2 Data/restraints/ parameters
(1)
(2)
C4H6N2S 114.17 Monoclinic P21/n, 4 14.4456(4), 5.4634(2), 6.7739(2) 93.004(1) 533.9(1) 1.421 13.0, 100.00 0.02 4 0.0448, 0.0712, 0.1075 0.064, 1.299 4300, 24, 49
C14H12N2S 240.32 Orthorhombic P212121, 4 19.6411(20), 11.2389(11), 5.5798(4) 90.0 1231.7(2) 1.296 8.0, 100.00 0.02 4 0.0300, 0.0397, 0.0756 0.032, 2.097 4500, 70, 78
two-connected S atom [35,36], are comparable with the corresponding distances reported for thiazole derivatives [37,38]. The C2AN1 [1.303(3)–1.310(2) Å] and C3AN1 [1.373(2)–1.393(3) Å] bond distances in (1) and (2) agree well with the mean values of C@N [1.31 Å] and CAN [1.38 Å] bond lengths based on 193 ACsp2@NACsp2A fragments obtained with MOGUL [39] from the CSD search of related organic compounds. The hydrogen-bonding interactions in (1) and (2), both having two NH proton donating bonds, are significantly different, specially in terms of accepting centers, the nitrogen and sulfur atoms, of the heterocyclic ring. In the molecular structure of polymorph of (1), XUVNIM, both amino H atoms are hydrogen bonded to N and S atoms of the thiazole ring, thus generating a cyclic R44 (14) synthon [40]. (1), however, does not form an Rnm (X) dimer, a feature common in many 2-aminothiazole derivatives [10,11,38], but alternately forms a NAH N hydrogen-bonded polymeric chain. The amino atom N2 in the molecule (1) at (x, y, z) acts as hydrogenbond donor, via atom H2A, to thiazole ring atom N1 in the molecule at (½ x, ½ + y, ½ z), so generating an infinite onedimensional C 11 (4) chain [40] propagating along the [0 1 0] direction. A CAH p contact from C3AH3 to the thiazole ring (S1/C2/ N1/C3/C4) links the parallel chains into a two-dimensional stack
Fig. 2. Molecular structures of: (a) C4H6N2S (1) and (b) C14H12N2S (2) with atom numbering scheme.
(Fig. 3a). Examination of structure of (1) for interactions involving sulfur atom (another possible acceptor in the molecule) reveals that the closest S H (C/N) intermolecular distance is S1 H5A(C5)i [symmetry code: (i) x, y 1, z] of 3.07 Å, [S1 H2B (N2)ii of 3.14 Å [symmetry code: (ii) x, 1 y, z)], with S1 H5AiAC5i angle of 134°, [S1 H2BiiAN2ii angle of 160°], which excludes any possible C/NAH S hydrogen bond formation. In (2), however, the amino atom N2 in the molecule at (x, y, z) is hydrogen bonded to S1 atom of the benzothiazole moiety in the molecule at (1 x, ½ + y, ½ z) to form a C 11 (8) chain [40] propagating along the [0 1 0] direction. The N S distance of 3.279(3) Å is significantly shorter than the average distance [3.75 Å] calculated using 176 structures in the CSD for NAH S hydrogen bonds to a Csp2ASACsp2 system, while the NAH S angle of 142° is comparable to the similar calculated from the CSD search. The chains in (2) are further connected via N2AH1A N1 and N2AH1B N1 weak hydrogen bonds (Table 2), thus producing a herringbone framework built with fused R34 (20) rings [40] (Fig. 3b). The Hirshfeld surfaces [41] provide a relatively new tool for analyzing packing modes as well as intermolecular interactions in molecular crystals while maintaining a whole-of-molecule approach. They are constructed by partitioning the space in a crystal into regions where the electron density from the sum of spherical atoms of the molecule is greater than the corresponding sum over the crystal [42]. Two-dimensional fingerprint plots [29] complement the Hirshfeld surfaces, quantitatively summarizing the nature and type of intermolecular interactions experienced by the molecules in the crystal. This analysis can be very valuable in the identification and quantitative comparison of similarities and subtle differences among the intermolecular interactions in polymorphs and related compounds [43,44]. The Hirshfeld surfaces of compounds (1) and (2) are illustrated in Fig. 4a and b, showing surfaces that have been mapped over a dnorm range of 0.5 to 1.0 Å. The color codes from red for short dnorm ranges to blue for long dnorm ranges were employed. The dominant interactions between the amine NH2 group and the thiazole ring N1 atom in (1) and S1 in (2) can be seen in the Hirshfeld surface as red areas marked as ‘a’, ‘b’ in Fig. 4a and ‘e’, ‘f’ in Fig. 4b. The light red spots labeled as ‘c’ and ‘d’ in Fig. 4a originate from CAH p interactions in (1) and that marked as ‘g’ in Fig. 4b is due to weak NAH N interaction in (2). Other bright red spot (marked as ‘h’) in Fig. 4b correspond to H H contacts in (2). The corresponding 2D fingerprint plot of (1) (Fig. 4a) exhibits characteristic spikes in the region 2.1 < de + di < 2.9 Å (labeled as ‘a’ and ‘b’). The upper spike ‘a’ in Fig. 4a represents the donor spike (amino H atom interacting with the N atom of the thiazole ring), and the lower spike ‘b’ being the acceptor spike (thiazole N atom interacting with the amino H atom). The wings (Fig. 4a, marked as ‘c’ and ‘d’) in the (di,de) regions of (1.6 Å, 1.0 Å), and (1.0 Å, 1.6 Å) are attributable to the CAH p interaction in (1). For compound (2), the wings in the (di + de) region of (2.3 Å, 2.9 Å) and (2.9 Å, 2.3 Å) in Fig. 4b are due to the H S/p interactions. The central spike extending upto (di,de) region of (0.8 Å, 0.8 Å) in Fig. 4b reflects a high % of H H contacts in (2). The relative contributions of different interactions to the Hirshfeld surface calculated for (1), (2), BAWKEP10 and XUVNIM as well as a few related aminothiazole and benzothiazole compounds (Fig. S2) retrieved from the CSD are shown in Fig. 5. Replacement of the thiazole ring and the amino (NH2) group in (1) by a benzothiazole ring and an aminophenyl group in (2) decreases significantly the contribution of H S contacts to the Hirshfeld surface from 18.6% in (1) to 4.2% in (2) with a corresponding two-fold increase of the H p interactions from 14.8% in (1) to 31.8% in (2). The reduced contribution of H S interactions to the Hirshfeld surface in (2) compared to that in BAWKEP10 and (1) can be attributed to the fact that a phenyl ring fusion across the C3AC4 bond
157
D.K. Hazra et al. / Journal of Molecular Structure 1039 (2013) 153–159
Fig. 3. (a) A view of two-dimensional stacking of molecules in C4H6N2S (1) and (b) a view of herringbone framework built with fused R34 (20) rings in C14H12N2S (2). [Symmetry code: (ii) 1 x, ½ + y, ½ z and (iii) 1 x, ½ + y, ½ z].
Table 2 Intermolecular contacts for C4H6N2S (1) and C14H12N2S (2) (Å, °). D-HA
d(D-H)
d(H A)
d(D A)
<(DHA)
[Symmetry transform]
C4H6N2S (1) N2AH2A N1 C3AH3 Cg1
0.86 0.96
2.20 2.70
3.000(3) 3.425(1)
154 135
[½ x, ½ + y, ½ z] [½ x, ½ + y, ½ z]
C14H12N2S (2) N2AH1B S1 N2AH1B Cg1 N2AH1A N1 N2AH1B N1
0.87 0.87 0.87 0.87
2.55 2.35 2.72 2.70
3.279(3) 3.046(2) 3.302(2) 3.369(2)
142 138 126 134
[1 x, [1 x, [1 x, [1 x,
½ + y, ½ + y, ½ + y, ½ + y,
½ z] ½ z] ½ z] ½ z]
Cg1 is the centroid of thiazole ring (S1/C2/N1/C3/C4).
and a bulky aminophenyl substitution at the C2 position of the thiazole ring in (1) restrict close intermolecular contacts involving the sulfur atom. It is evident from Fig. 5 that the molecular interactions in substituted aminothiazoles such as compound (1), HIYLOQ [45], UNOMEP [46], XUNKAS [38] and XUVNIM [18] are predominantly of H H, H N, H S and H p types, which can account for about 87–97% (96.0% in BAWKEP10, 97.3% in (1), 91.7% in HIYLOQ, 87.7% in UNOMEP, 96.9% in XUNKAS and 94.8% in XUVNIM) of the Hirshfeld surface area. In the benzothiazole derivatives, however, the H H and H p contacts together contributed about 70–82% (80.5% in (2), 70.3% in IFUREH [12], 77.5% in JEVTIO [47], 73.1% in OLUZAX [48], 81.2% in YEVRAS [49] and 71.2% in WIHKUT [50]) to the Hirshfeld surface area; the remaining contributions were distributed mostly among the H N, H S, H O and S S interactions. 3.2. Electronic structure Superposition of molecular conformations of (1) and (2) as established by the X-ray study and quantum mechanical calculations show a good agreement (Figs. S3 and S4); the r.m.s. deviations between the coordinates obtained by geometry optimization and X-ray structure analysis are 0.042 Å (for 1) and 0.046 Å (for 2), respectively (Table S1). The net charges of atoms and dipoles calculated using BLYP functional indicate that the sulfur and nitrogen atoms in molecules (1) and (2) bear negative charges, while the carbon atoms in the thiazole core bear positive charges. The atomic charges estimated from the Mulliken population analysis appear to be consistent with the electronegativity of constituent atoms. Due to this charge redistribution, the dipole of the molecules (1) and (2) becomes 0.99 a.u. and 1.09 a.u., respectively.
The charge densities of HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) are depicted in Fig. 6a (for 1) and Fig. 6b (for 2) showing bonding- antibonding patterns in the molecules. The orbital energy level analysis for (1) and (2) at the BLYP level shows EHOMO and ELUMO values of 4.73 eV, 0.91 eV for (1), and 4.73 eV, 1.96 eV for (2), respectively. The differences between the orbital energies corresponding to HOMO-1 ? HOMO-4 energy levels in (1) and (2) are greater than 0.05 eV, which indicate that the energy levels in compounds (1) and (2) are non-degenerate. Similar conclusion can be drawn from the LUMO + 1 ? LUMO + 4 orbital energy calculations for both molecules. 4. Conclusions The results of the crystal structure determination using X-ray powder diffraction of two aminothiazole and benzothiazole derivatives, 2-amino-5-methylthiazole (1) and 4-(6-methyl-2-benzothiazolyl) aniline (2) clearly demonstrate an interplay of NAH N/S hydrogen bonds and C/NAH p interactions generating two-dimensional framework. The molecular geometry and the electronic structures of (1) and (2) have been analyzed by the DFT calculations. The observed molecular conformations of compounds as established by the X-ray analyses agree well with that obtained from the quantum mechanical calculations. A comparison of close intermolecular interactions in (1), (2) and a few related compounds using the Hirshfeld surface analysis indicated that the H H, H N, H S and H p interactions can account for about 87–97% of the Hirshfeld surface area in substituted aminothiazoles, whereas in benzothiazole derivatives the H H and H p contacts contributed about 70–82% of the Hirshfeld surface area. The compounds investigated here reveal the influence of
158
D.K. Hazra et al. / Journal of Molecular Structure 1039 (2013) 153–159
Fig. 4. Hirshfeld surface and 2D fingerprint plot of: (a) C4H6N2S (1) and (b) C14H12N2S (2).
Fig. 5. The relative contributions of various intermolecular contacts to the Hirshfeld surface area in (1), (2) and related compounds retrieved from the CSD.
Fig. 6. Charge density isosurface of (a) HOMO and LUMO orbitals in C4H6N2S (1) and (b) HOMO and LUMO orbitals in C14H12N2S (2) set at 0.03 eÅ3 calculated by the DFT method [surfaces in yellow (+) and blue ()]. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
D.K. Hazra et al. / Journal of Molecular Structure 1039 (2013) 153–159
weak intermolecular forces in building supramolecular assembly in the solid state. Acknowledgements Financial support from the University Grants Commission, New Delhi, through the DRS (SAP-II) program for purchasing the X-ray powder diffractometer in the Department of Physics, Jadavpur University, is gratefully acknowledged. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.molstruc.2013. 01.077. References [1] G.R. Desiraju, Angew. Chem. Int. Ed. 46 (2007) 8342. [2] E.R.T. Tiekink, J.J. Vittal, M. Zaworotko (Eds.), Organic Crystal Engineering: Frontiers in Crystal Engineering, John Wiley & Sons Ltd., Chichester, UK, 2010. [3] F.H. Allen, W.D.S. Motherwell, P.R. Raithby, G.P. Shields, R. Taylor, New J. Chem. 23 (1999) 25. [4] M. Nishio, CrystEngComm 6 (2004) 130. [5] G.R. Desiraju, T. Steiner, The Weak Hydrogen Bond in Structural Chemistry and Biology, Oxford University Press, Oxford, UK, 1999. [6] C.N. Sundaresan, S. Dixit, P. Venugopalan, J. Mol. Struct. 693 (2004) 205. [7] E. Arunan, G.R. Desiraju, R.A. Klein, J. Sadlej, S. Scheiner, I. Alkorta, D.C. Clary, R.H. Crabtree, J.J. Dannenberg, P. Hobza, H.G. Kjaergaard, A.C. Legon, B. Mennucci, D.J. Nesbitt, Pure Appl. Chem. 83 (2011) 1619. [8] B.S. Holla, K.V. Malini, B.S. Rao, B.K. Sarojini, N.S. Kumari, Eur. J. Med. Chem. 38 (2003) 313. [9] I. Hutchinson, J. Med. Chem. 45 (2002) 744. [10] C. Caranoni, J.P. Reboul, Acta Cryst. B38 (1982) 1255. [11] D.E. Lynch, I. McClenaghan, Acta Cryst. C60 (2004) o592. [12] Y. Zhang, Z.-H. Su, Q.-Z. Wang, L. Teng, Acta Cryst. E64 (2008) o2065. [13] W.-S. Wang, M. Gao, X. Chen, B. Liu, Acta Cryst. E62 (2006) o5668. [14] W.I.F. David, K. Shankland, L.B. McCusker, C. Baerlocher (Eds.), Structure Determination from Powder Diffraction Data, Oxford University Press, New York, 2002. [15] K.D.M. Harris, E.Y. Cheung, Chem. Soc. Rev. 33 (2004) 526. [16] A. Bhattacharya, S. Ghosh, K. Kankanala, V.R. Reddy, K. Mukkanti, S. Pal, A.K. Mukherjee, Chem. Phys. Lett. 493 (2010) 151.
159
[17] K.D.M. Harris, Mater. Manuf. Process. 24 (2009) 293. [18] D.E. Lynch, Private, Communication, 2009. [19] A. Altomare, C. Giacovazzo, A. Guagliardi, A.G.G. Moliterni, R. Rizzi, E. Werner, J. Appl. Cryst. 33 (2000) 1180. [20] A. Altomare, R. Caliandro, M. Camalli, C. Cuocci, C. Giacovazzo, A.G.G. Moliterni, R. Rizzi, J. Appl. Cryst. 37 (2004) 1025. [21] A. Le Bail, H. Duroy, J.L. Fourquet, Mater. Res. Bull. 23 (1988) 447. [22] H.J. Toraya, J. Appl. Cryst. 19 (1986) 440. [23] W.I.F. David, K. Shankland, J. van de Streek, E. Pidcock, W.D.S. Motherwell, J.C. Cole, J. Appl. Cryst. 39 (2006) 910. [24] J.J. Stewart, J. Mol. Model. 13 (2007) 1173. [25] H.M. Rietveld, Acta Cryst. 22 (1967) 151. [26] A.C. Larson, R.B. Von Dreele, General Structure Analysis System (GSAS), Los Alamos National Laboratory Report LAUR, 2000, p. 86. [27] B.H. Toby, J. Appl. Cryst. 34 (2001) 210. [28] J.J. McKinnon, A.S. Mitchell, M.A. Spackman, Chem. Eur. J. 4 (1998) 2136. [29] M.A. Spackman, J.J. McKinnon, CrystEngComm 4 (2002) 378. [30] S.K Wolff, D.J. Grimwood, J.J. McKinnon, D. Jayatilaka, M.A. Spackman, Crystal Explorer. University of Western Australia, Perth, Australia, 2007.