Essay Example on At room temperature the title compound crystallizes in the Triclinic

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At room temperature the title compound crystallizes in the triclinic system P 1 space group with the following unit cell parameters a 8 7148 4 b 12 4875 6 c 16 0986 7 Å α 95 073 2 β 101 035 2 γ 107 446 2 Diamond computer program is used to prepare the drawings The crystal data collected reflections and the parameters of the final refinement are gathered in Table 1 The final atomic coordinates and Ueq or Uiso are given in in Table2 The interatomic bond distances and angle schemes are listed in Table 3 and 4 Hydrogen bonds schemes are listed in Table 5 The crystallographic analysis of this compound reveals that the crystal structure of C6H20N3 2 Cr2O7 3 consists of three distinct dichromates anion with an eclipsed conformation and a two protonated template N 3 aminopropyl 1 3 diaminopropane The XRPD data of a powder sample of C6H20N3 2 Cr2O7 3 has been compared to the pattern calculated from its single crystal data Mercury 3 6 software was used to generate the XRPD pattern from the single crystal data 22 Comparison of the diffraction patterns in Figure 1 indicates that C6H20N3 2 Cr2O7 3 is pure A view of the asymmetric unit of the structure showing the thermal ellipsoid atom mean square displacements of non hydrogen is depicted in Fig 2 The structural arrangement of the title compound can be described as an alternation of organic and inorganic layers along the 100 and 010 directions made up of C6H20N3 3 and Cr2O7 2 atom groups as shown in Fig 3 respectively Geometry of the Cr2O7 2 anion The dichromate ion consists of two CrO4 tetrahedra sharing the bridging oxygen atom O 71 O 72 and O 73 Fig 4a

As shown in Fig 4b the CrO4 tetrahedra viewed along the Cr O Cr direction exhibit a staggered configuration the tetrahedra twist about 55 31 to 57 83 away from an exactly eclipsed configuration in such a way that the ternary axis symmetry disappears In addition The bond distances between chromate and the terminal oxygen atoms O t range from 1 546 4 to 1 613 2 Å with an average Cr O t of 1 596Å whereas the bond lengths between Cr and the bridging oxygen atom O b are notably longer 1 772 2 1 732 3 1 767 3 1 780 3 and 1 778 3 Å Both the Cr O t and Cr O b bond distances are in the range observed in many other dichromates see Table 4 for comparison Interatomic bond angles of the dichromate anions spread respectively within the ranges 104 0 3 112 32 15 for O t Cr O t angles and 127 52 16 143 5 2 for Cr O b Cr angles as listed in Table 3 These geometrical features have also been noticed in other related crystal structure 38 The average values of the distortion parameters of CrO42 tetrahedron are calculated respectively using Eqs 1 and 2 39 ID O Cr O _ i 1 n1 ai am n1am 1 ID Cr O _ i 1 n2 di dm n2dm 2 with a O Cr O angle d Cr O distance m average values n1 4 and n2 6 ID O Cr O average 0 013 ID Cr O average 0 038 The low values of the distortion indices indicate that the coordination geometry of the metal is pseudo regular tetrahedron Geometry of the NH2 CH2 3NH3 2 3 cation The protonated NH2 CH2 3NH3 2 3 molecule have a trans configuration with a non crystallographic inversion center Table 5 reports the principal geometrical features of this organic group The C N and C C bond lengths vary from 1 470 5 Å to 1 492 4 Å and 1 501 4 Å to 1 513 4 Å respectively

They are similar to those reported in other N 3 ammoniumpropyl 1 3diammoniumpropane salts such as C6H20N3 BiCl6 40 C6H20N3 BiBr6 H2O 41 and C6H20N3 2 V4O4F14 2H2O 42 The intermolecular hydrogen bonding contacts N H O provide linkage between the NH3 CH2 3NH2 CH2 3NH3 3 cations and the Cr2O72 anionic chains belonging to the successive 101 planes All of these hydrogen bonds N H O give rise to a three dimensional network in the structure Fig 3 and Table 6 3 2 Hirshfeld surface analysis Hirshfeld surfaces and their associated two dimensional fingerprint plots 43 have been used to quantify the various intermolecular interactions in the title compound The Hirshfeld surface of a molecule is mapped using the descriptor dnorm which encompasses two factors one is de representing the distance of any surface point nearest to the internal atoms and the other one is di representing the distance of the surface point nearest to the exterior atoms and also with the van der Waals radii of the atoms 44 The Hirshfeld surfaces mapped over dnorm range of 0 502 1 427 Å are displayed in Fig 5 The surfaces are shown as transparent to allow visualization of the molecule The dominant interaction between oxygen O and hydrogen H atoms can be observed in the Hirshfeld surface as the red areas Fig 5 The intermolecular interactions of the title compound are shown in the 2D fingerprint plots shown in Fig 6 Globally O H and H O intermolecular interactions were most abundant in the crystal packing 47 01 and 39 02 respectively It is evident that van der Waals forces exert an important influence on the stabilization of the packing in the crystal structure Other intercontacts i e H H 9 10 O O 4 70 and Cr H 0 1 contribute less to the Hirshfeld surfaces The whole fingerprint region and all other interactions which are a combination of de and di are displayed in Fig 7

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