Structural study, vibrational and optical properties, Hirshfeld surface analysis and DFT investigation of a novel organic cation hexachloridostannate(IV), (C5H8N3)2[SnCl6]
Graphical abstract
Introduction
Inorganic chemistry is beginning to have a major impact on medicine. It offers great potential for the design of novel therapeutic and diagnostic agents [1]. Furthermore, the use of metals such as tin in medicine raises a very important issue like toxicity. In addition to the biological evaluation for therapeutic potential, further chemical and pharmacological studies are necessary to unravel a structure–activity relationship for organotin derivatives that can guide subsequent design of new drug candidates [[2], [3], [4]]. Correlation of X-ray crystallographic data with anti-cancer activity has shown interesting results [[5], [6], [7]]. The Sn-X (X: halogen) length as well as the X-Sn-X bond angle seem to play an important role in the development of antitumor activity by octahedral Sn(IV) compounds [8]. While therapeutics-based organotin compounds continue to attract the greatest attention, ‘inorganic’ tin drugs are in or are finding their way into the clinic, being exploited now in treatment of jaundice, cancers and wet Age-related Macular Degeneration (AMD) which is a leading cause of blindness in older adult whereas organotin halides and their complexes with amines and other ligands exhibit borderline activities against P388 and L1210 leukaemia [[9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21]].
On the other hand, the choice of the ligand has an attractive wide influence in the synthesis of compound based on tin. Diaminopyridine as ligand can offer more benefits in many biologically important molecules such as cytosine derivatives, folates and antifolates drugs. When correlated with its availability with N donor systems including high affinity for metalions. Combination between these two entities leads to the synthesis of new compounds which thanks to their synergistic effect play a key role in control and design of new materials with appropriate and desired properties.
Organic-inorganic hybrids materials received a considerable attention due to their flexibility of these structures which gives a rich and fertile playground for the elaboration of interesting crystal structure with different physical properties. Furthermore, there are many interesting aspects of inorganic and organic tin chemistry; these complexes and their derivatives received considerable attention due to their interesting dielectric properties [22], optoelectronic [23] and development of low-cost photovoltaic devices [24]. It should be noted that tin and its derivatives are in commercial use more than any other elements. Considering the attractive properties a of Sn(IV) and the new promising opportunities that may open with regard to the development of useful organic–inorganic hybrid materials [25], we report in this work the synthesis, and a combined experimental and a theoretical studies of a new hybrid compound namely, bis(2,6-diaminopyridinium) hexachlorostannate(IV). The crystal structure was carried out by single crystal X-ray diffraction and the phase purity of the crystalline sample was studied by powder X-ray diffraction. Vibrational study by IR spectroscopy and optical properties by UV–Vis diffuse reflectance spectroscopy were done to identify the functional groups present in the studied compound and to determine the band gap respectively. Moreover, DFT calculations were reported in order to carry out correlation between crystal structure and physical properties. Hirshfeld surface analysis and molecular electrostatic potential (MEP) were also performed.
Section snippets
Materials and measurements
All reagents and solvents were obtained from commercial sources and used without further purification. The infrared (IR) spectrum was collected on a PerkinElmer Spectrum 100 FT-IR spectrophotometer with ATR accessory in the range of 4000-400 cm−1 using pellets made from a pure crystalline sample. UV–Vis spectrum was recorded on an Ellice SL–164 Double BEAM UV–Vis spectrophotometer in the range 200–800 nm using methanol as solvent.
Synthesis of (C5H8N3)2[SnCl6]
SnCl2 (0.3506 g, 1 mmol) was dissolved in 5 ml of MeOH resulting
Crystal structure
(C5H8N3)2[SnCl6] crystallizes at room temperature, in the monoclinic system, space group P21/c with two formula unit cell (Z = 2). The asymmetric unit of the title compound contains one protonated cation (C5H8N3)+ and a half of the [SnCl6]2- anion. Similarly to the previous studies [[38], [39], [40], [41], [42], [43], [44], [45]], the anion lies on the inversion center (Fig. 2). This question is probably connected with the octahedral structure of the anion which facilitates formation of the
Conclusion
Good quality single crystals of a novel organic–inorganic hybrid compound (C5H8N3)2[SnCl6] has been successfully synthesized by slow evaporation method at room temperature. This compound belongs to the monoclinic system with the P21/c space group. The crystal structure can be described as a 2D mixed organic-inorganic layers packed along the [100] direction and parallel to (bc) plan. The cohesion and the stability result from the establishment of N_H⋯Cl hydrogen bonds between the organic cations
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